Alkali Activated Concrete

The imperative to find sustainable alternatives to conventional cement, given its energy-intensive production and significant environmental impact, has driven research into alternative binder materials for civil infrastructure. This paper explores Geopolymer concrete (GPC), a polymer-based binder technology, as a promising solution to reduce the environmental footprint associated with traditional cement production. The study meticulously examines various aspects of GPC, focusing on its impact on crucial durability properties for infrastructure applications. This includes an in-depth analysis of GPC properties, elucidating characteristics influencing performance. In addition to fundamental properties, the paper critically evaluates the resistance of geopolymer pastes and concrete to a spectrum of extreme conditions. The discussion spans testing methodologies for both heat- and ambient-cured geopolymers, providing insights into their performance and durability across diverse environmental challenges. This comprehensive review aims to enhance the understanding of GPC technology, offering valuable insights for researchers, engineers, and industry professionals committed to sustainable and resilient infrastructure solutions.

All the opinions and statements expressed in the papers are on the responsibility of author(s) and are not to be regarded as those of the journal of Research on Engineering Structures and Materials (RESM) organization or related parties. The publishers make no warranty, explicit or implied, or make any representation with respect to the contents of any article will be complete or accurate or up to date. The accuracy of any instructions, equations, or other information should be independently verified. The publisher and related parties shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with use of the information given in the journal or related means. Published articles are freely available to users under the terms of Creative Commons Attribution -NonCommercial 4.0 International Public License, as currently displayed at here (the "CC BY -NC").

Shotcrete is a construction material that is applied by spraying under high pressure, and there are many factors that affect its properties. In this study, the effect of cement dosage and water-to-cement ratio on the compressive strength and drying shrinkage performance of shotcrete was investigated. For this purpose, shotcrete specimens were produced using three different water-to-cement ratios (0.40, 0.45, 0.50) and three different cement dosages (400, 450, 500). The unit weight, ultrasonic pulse velocity (UPV), compressive strength, splitting tensile strength, and drying shrinkage performance of the produced specimens were examined. As a result of the experimental studies, an increase in cement dosage resulted in an increase in unit weight values, with the amount of increase ranging from approximately 1% to 3%. When the UPV value was examined, an increase in cement dosage resulted in an increase in UPV values, with an increase of approximately 1% to 5%. An increase in cement dosa...

Concrete is indeed one of the most consumed construction materials all over the world. In spite of that, its behavior towards absolute volume change is still faced with uncertainties in terms of chemical and physical reactions at different stages of its life span, starting from the early time of hydration process, which depends on various factors including water/cement ratio, concrete proportioning and surrounding environmental conditions. This interest in understanding and defining the different types of shrinkage and the factors impacting each one is driven by the importance of these volumetric variations in determining the concrete permeability, which ultimately controls its durability. Many studies have shown that the total prevention of concrete from undergoing shrinkage is impractical. However, different practices have been used to control various types of shrinkage in concrete and limit its magnitude. This paper provides a detailed review of the major and latest findings regarding concrete shrinkage types, influencing parameters, and their impacts on concrete properties. Also, it discusses the efficiency of the available chemical and mineral admixtures in controlling the shrinkage of concrete.

Portland cement is a popular binder but causes many adverse effects on the environment. That is due to the large consumption of raw materials and energy during production while emitting vast amounts of CO2. In recent years, Alkali Aluminosilicate Cement (AAC) has drawn much attention in research and development and promises to become a binder that can replace the traditional cement. In many studies of this binder, the content of the ingredients is often gradually changed to determine the optimal composition. The object of this paper is to optimize the composition of AAC using a combination of three by-products as the primary raw material, including Rush Husk Ash (RHA), Fly Ash (FA), and Ground Granulated Blast-Furnace Slag (GGBS). The investigation was conducted based on the critical parameter SiO2/Al2O3, and the D-optimal design. The FA and the GGBS were industrial product form, while the RHA was ground in a ball mill for 2 hours before mixing. The results show that this type of binder has setting time and soundness to meet standard cement requirements. While comparing to Portland cement, the AAC has a faster setting time, slower development of compressive strength in the early stages but a higher strength at the age of 56 days. According to the highest compressive strength at 28 days and high fly ash content, the optimal composition was RHA of 27.8%, FA of 41.8%, and GGBS of 15.4%, corresponding to the ratio SiO2/Al2O3 of 3.83. In addition, compressive strength at 28 days of the mortar specimens with the optimal binder and the ratio of water/ cement at 0.32 reached 63 MPa.

The problem of the composition optimization of concrete mixes seems to be quite urgent as errors at the composition design stage can lead to problems of concrete at the stage of exploitation such as delamination, cracking etc. Reasonable selection of concrete mix components guarantees the required strength of concrete and reinforced concrete structures in the future. This paper investigates the influence of the concrete mix composition on the strength of concrete. Firstly, typical risks that can occur on the composition design stage have been identified through the experts' interviews. Secondly, this risks were associated with indicators and characteristics that can be tested experimentally. Running of several mathematical models has allowed to outline concrete mix parameters of highest importance and formulate an empirical equation for the dependence of the strength of the concrete mixture on the values of the coarse aggregate quality factor, the fine aggregate fraction and the consumption of the Portland cement has been proposed. As a result, a methodology for controlling the quality of concrete at the stage of the composition design has been formulated.

The innovation of using pumice as a basic material for traditional Balinese ornaments is increasingly widespread, especially in public facilities and holy places. In practice, natural pumice ground is mixed with portland cement as a binder before being molded and carved. To meet sustainable green building standards, the use of pozzolan cement needs to be reduced and replaced with more environmentally friendly materials. Bungkulan pumice soil (BPS) is the precursor material (P) used in this research, plus the alkali activator (A), sodium hydroxide (NaOH), and sodium silicate (Na2SiO3). Samples were made with 3 variations of PC (control) with a mixture of Portland cement and pumice soil (1:3). BPS-1 and BPS-2 samples were prepared with precursor and activator ratios (75%:25%) and (80%:20%), respectively. The activator ratio (Na2SiO3: NaOH) is 2:1 and the molarity concentration is 12M. For every variant, three samples were created and evaluated at 7, 14, 21, and 28 days of age. The sample with the BPS-2 code had the highest compressive strength and tensile strength results. SEM-EDX microstructural examinations were also performed on the samples with the results that the samples mixed with portland cement (PC) had more pore space compared to the geopolymer species (BPS-1 and BPS-2) because they did not use an activator to increase the density between the pores. Geopolymer can be an environmentally friendly alternative material for Balinese ornaments considering their mechanical and microstructural characteristics.

Geopolymer Concrete (GPC) is a new class of concrete that presents a vital improvement in sustainability and the environment, particularly in recycling and alternative construction methods. Geopolymers offer a sustainable, low energy consumption, low carbon footprint, and a 100% substitute for the Portland cement binder for civil infrastructure applications. Furthermore, many aluminosilicate materials can be obtained as by-products of other processes, such as coal combustion or the thermal pulping of wood. In addition, slag and fly ash are necessary to source materials for geopolymer. Therefore, geopolymer is considered a solution for waste management that can minimize greenhouse gas emissions. In this statistical study, the present experimental work and found experimental data were collected from local and international literature and were used to build and validate the statistical models to predict the strength development of Geopolymer concrete with binary and ternary systems of source materials. The main independent variable was R, representing the ratio of SiO2/Al2O3 by weight in the source material. The investigated range of R was 1.42-3.6. Nine concrete geopolymer mixes with R in the above range represent the experimental part carried out. The targeted properties were compressive, splitting, and flexural strengths. The experimental results showed that the R ratio significantly influences the mechanical performance of the final product. The compressive strength improved by 82, 86, 93, and 95%, when metakaolin content was partially replaced by fly ash and GGBS by percentages of 37, 70, 90, 72, and 95% for mixes 2, 3, 5, 7, and 8 respectively. Also, when GGBS partially replaced fly ash content by 36% and 100% for mixes 6 and 9, compressive strength improved by 10.6% and 41.8%, respectively, compared to mix4. Furthermore, the statistical study revealed that the R ratio might be utilized to determine geopolymer strength with reasonable accuracy. The built models were developed by linear and non-linear regression analysis using SPSS software, version 25.

Great efforts are being made to minimize the negative impact of the Portland cement industry on the environment by using industrial by-products during the manufacture of clinker or by the partial replacement of cement during the preparation of concrete. However, the carbon footprint remains relatively high in addition to the large consumption of natural resources such as sand and other aggregates. A solution to these problems is to completely replace Portland cement with a new generation of mineral binders, commonly known as geopolymers, which have properties similar to those of Portland cement. These binders can be obtained by the alkali-activation of siliceous or aluminosilicate materials. This study aims to develop pozzolanic type binders at room temperature (20°C) from the alkali-activation of aluminosilicate materials based on metakaolin and blast furnace slag at different percentages. Different activators were employed, including solid (NaOH) and liquid (Na2SiO3.nH2O). The optimal mixtures were used for making mortars based on natural sand (NS) and concrete recycled sand (CRS). A comparative experimental study of the physical, mechanical, and microstructural characteristics of the two types of mortars was conducted. Cement mixtures with a high amount of slag and an association of sodium hydroxide and sodium silicate gave the best physico-mechanical properties. A drop in the compressive strength of mortars prepared with CRS was observed after 365 days, but it was still higher than those with NS. The obtained results show the possibility of designing an eco-friendly CRS-based geopolymer mortar that is more resistant than NS-based mortar with a homogeneous and integrated microstructure.

The objective of this study was to investigate the effect of curing temperature on the mechanical properties of sanitary ware porcelain powder-based geopolymer paste and mortar under various curing temperatures. The setting time, porosity, water absorption, and compressive strength of specimens mixed with alkaline concentrations of 8M, 10M, 12M, and 14M were compared. All mortar cube (50×50×50 mm) specimens were placed into drying ovens for 24 hours at 60°C, 75°C, 90°C, and 105°C, respectively. The specimens were then air-cured for 1, 3, 7, 14, and 28 days. The results showed that the elevated curing temperature accelerated the polymerization process of the porcelain geopolymerization reaction. The setting time varied between 89 mins and 380 mins. It showed variability depending on alkaline concentration and initial curing temperature. The setting time of pastes decreased when alkaline concentrations increased. An increasing temperature in the drying oven decreased the initial and final setting times. Similar to this, the rate of water absorption and permeability of porcelain-based geopolymer mortar specimens decreased with drying oven temperatures and increments in alkaline concentration. The lowest water absorption and porosity of the specimen were 2.1% and 15.7%, respectively. The compressive strength increased as drying oven temperatures and alkaline concentrations increased. The highest 28 day compressive strength was found in 14M specimens with 105°C curing temperatures. The ultimate compressive strength was 64.45 N/mm 2. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were investigated to study the microstructural properties of the geopolymers.

The escalating demand for construction materials driven by rapid population growth has heightened the reliance on cement binders, resulting in increased CO2 emissions from the cement industry. Geopolymers, considered environmentally friendly alternatives, have been explored in various studies to address this challenge. This research specifically investigates the impact of different types of ceramic waste bricks (BT), floor tiles (FT), roof tiles (RT), and sanitary ceramics (ST) on the physical and mechanical properties of fly ash-based geopolymer mortar. To provide a comprehensive understanding, this research examines the compressive strength, mineral phase, chemical bonds, and microscopic evolution of fly ash geopolymer mortar incorporating varying proportions of each ceramic waste type (25% and 50% fly ash replacement). A consistent mixture of Na2SiO3 and NaOH was used for the alkaline solution in all formulations. The curing process was carried out at room temperature for 7, 14, and 28 days prior to the compressive strength test. The result revealed that the inclusion of 25% BT experienced higher strength compared to the control sample after 14 days, but the strength became comparable after 28 days at 40.24 MPa. A reduction in strength was evident with the addition of other ceramic components. Moreover, higher incorporation of CWP correlated with a faster setting time for fresh geopolymers. This was also linked to the degree of gel formation, as indicated in the microstructure images. The emergence of plagioclase minerals was evident in all formulations of the geopolymer products under XRD analysis, while the bond of the geopolymer signature, Si-O-T (T = Si or Al), was identified from the infrared spectra. The microstructure of the binder showed a geopolymer matrix alongside unreacted fly ash particles. Overall, CWP replacement up to 25% can be potential in fly ash geopolymer without sacrificing significant strength loss and remaining in the range of normal strength mortar.

High-temperature exposures of concrete lead to serious damage in concrete structures, resulting in the significant decay of mechanical properties and spalling of concrete. Alkali-activated concretes (AAC) of blended aluminosilicate precursors and activators have been proven to have higher thermal endurance than conventional portland cement concrete. Incorporation of gypsum (GY) in alkali-activated systems has proven to positively impact the mechanical properties when adopted in controlled amounts. GY releases SO4 2-to the binder system, which helps in the formation of ettringites, along with Ca 2+ , which leads to the formation of hydrates. This causes a reduction in porosity and improves strength gain. Incorporation of GY into the fly ash-slag-based alkali-activated system further improves thermal endurance by retaining considerable residual strengths even after 800°C exposure. In the present study, the influence of GY on the residual mechanical properties of fly ash-slag-based AAC is investigated to explore the thermal endurance of the ternary mix at elevated temperatures. The mechanical properties of fly ash (FA), Ground Granulated Blast Furnace Slag (GGBS), and gypsum (GY) ternary blended AAC subjected to elevated temperatures are studied in comparison with conventional portland cement concrete (control mix). AAC design mixes with varying proportions of GY as a replacement to FA-GGBS precursor are tested for mechanical properties to obtain the optimum mix. The residual mechanical properties of the FA-GGBS-GY optimum ternary AAC mix are obtained after exposure to elevated temperatures up to 800°C. The morphology and microstructural characteristics of AAC are studied by Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) analyses to investigate the influence of gypsum on the thermal endurance of concrete when exposed to elevated temperatures. Improved thermal endurance is observed for AAC when FA-GGBS precursors are replaced with 5% of GY as compared to the thermal endurance of conventional portland cement concrete (PCC) of the same compressive strength.

This paper reports the effect of slag (SL) replacement and water-to-binder (w/b) ratio on properties of one-part geopolymer derived from high-calcium fly ash (FA) and sodium silicate powder (NP). The FA was replaced by SL at the rates of 20% and 40%, respectively. This study focused on conducting experimental tests to evaluate the relative slump, setting time, compressive strength, and flexural strength of one-part FA-based geopolymer. The relationship between compressive and flexural strengths of one-part geopolymer mortar was expressed using the simplified linear regression model, whereas the normalization of compressive and flexural strengths with SL replacement by the strength of one-part geopolymer mortar without SL as the divisor was also evaluated. Experimental results showed that the increase of SL replacement and w/b ratio significantly affected the workability and strength development of one-part geopolymer mortar. Higher SL replacement exhibited a positive effect on their compressive and flexural strengths; however, a reduction in its setting time was obtained. The enhancement in strength development of one-part geopolymer was primarily due to the increased calcium content of SL. Similarly, reducing the w/b ratio in the production of one-part geopolymer resulted in a decrease in setting time and an increase in strength development. Based on the relationship between compressive and flexural strengths, the prediction coefficient value (R 2) obtained from the curve fitting procedure was 0.835, indicating a good level of reliability and acceptability for engineering applications.

This study deals with the use of ground palm oil fuel ash (GPOFA) in combination with ground granulated blast furnace slag (GGBFS) and ground calcium carbide residue (GCR) to produce the binary and ternary binders-based alkali activated mortar. The appropriate content of materials in each binder type was determined as a function of compressive strength. The results revealed that both GPOFA:GGBFS and GPOFA:GCR binders had an optimum blending ratio of 70:30 wt%, while the GPOFA:GGBFS:GCR binder was 55:30:15 wt%. An alkaline catalyst of NaOH was admixed to the best mixture in each binder type to stimulate the mortar's compressive strength. The sulfuric acid (H2SO4) resistance of the mortar in terms of weight change was also examined. The addition of 1M NaOH in both binary and ternary binders could enhance the compressive strength and H2SO4 resistance of the mortar. The highest compressive strength and lowest weight change due to soaking in H2SO4 solution were found in the ternary binder mortar with a 1 M NaOH. The mortar with GCR immersed in H2SO4 solution resulted in an increased weight, which was different from that of the mortar without GCR. The microstructural analysis of the alkali-activated pastes indicated more reaction products than in the case of the pastes without alkali activator. However, a higher concentration of 2 M NaOH resulted in a poor microstructure, which had a negative effect on the compressive strength and H2SO4 resistance.

Brick represents one of the most used materials for the construction of buildings, but the rising demand of building materials and increased construction and demolition wastes have encouraged the development of new building materials. However, the traditional brick production causes several environmental and human health impacts, so there is a clear need of searching and replacing for more efficient and durable alternatives far beyond the limitations of the conventional brick production. The production and use of alternative materials, such as geopolymers, represents a great opportunity to ensure greater sustainability in the construction sector especially for the use of industrial wastes such as fly ash or blast furnace slag, as precursors solid. Study results have revealed that the Geopolymeric brick making process consumes less energy and involves low cost in terms of raw materials. The production of the former is compared to conventional bricks and their development which is an important step to reach better performance and environmental friendly materials. The purpose of this article is to evaluate impacts during the life cycle and describes the basic operations of the geopolymeric brick manufacturing. The analysis is performed using a life cycle approach to identify and quantify the environmental performance of the process.

In recent years, many research works have been done to investigate the possibility of utilizing a broad range of materials as raw materials in the production of geopolymer cements. The use of artificial pozzolans or aluminosilicate-type industrial waste materials such as granulated blast-furnace slag and fly ash has been reported in many research works. Natural pozzolans are also aluminosilicate-type materials which can be activated with solutions of NaOH and Na 2 SiO 3 . Using a pumice-type natural pozzolan from Taftan Mountain located at the south east of Iran and different alkaliactivators based on combinations of Na 2 SiO 3 and NaOH, a number of natural-pozzolanbased geopolymer cement systems were designed and prepared. Final setting time, workability, and 28-day compressive strength of the systems were studied. The results obtained reveal that Taftan pozzolan can be activated using a proportioned mixture of Na 2 SiO 3 and NaOH resulting in the formation of a geopolymer cement system exhibiting suitable workability and relatively high 28-day compressive strengths up to 63 MPa.

Natural pozzolans are aluminosilicate-type materials which can be activated with solutions of NaOH and Na 2 SiO 3 . Using a pumice-type natural pozzolan and different alkali-activators based on combinations of Na 2 SiO 3 and NaOH, a number of geopolymer cement systems were designed and studied. Water-to-dry binder ratio, silica modulus, and sodium oxide concentration of the systems were adjusted at different levels and setting time, workability, and 28-day compressive strengths of the systems were studied. The results obtained reveal that natural pozzolans of pumice-type can be activated using a proportioned mixture of Na 2 SiO 3 and NaOH resulting in the formation of a geopolymer cement system exhibiting suitable workability and acceptable 28-day compressive strengths. All the measured final setting times are acceptable compared to standard values given for Portland cement.

Abstract: In recent years, many research works have been done to investigate the possibility of utilizing a broad range of materials as raw materials in the production of geopolymer cements. The use of artificial pozzolans or aluminosilicate-type industrial waste materials ...

Research works carried out in developing other alkali activated binders such as fly ash and metakaolin show that this new binder based on kaolin is likely to have enormous potential to become an alternative binder to current concrete. Sodium hydroxide was mixed with sodium silicate to prepare liquid alkali activator 24 h prior to use. Kaolin powder was mixed well with alkali activator using mixer. The fresh paste was then rapidly poured into steel mould and put into the oven at suitable temperature. This study aims to analyze the effect of Sodium Hydroxide (NaOH) concentration (6M-14M) on compressive strength of kaolin cement paste. The result shows that the kaolin binder has adequate compressive strength and is able to apply for non-loading construction materials. This paper outlines the potential of kaolin to produce an environmental friendly, energy saving, clean technology to conserve the natural environment and resources. Kaolin binders are still in the early stages of development and; hence, they need further research work in order to become technically and economically viable construction materials.

This paper reviews the use of recycled waste materials-such as plastic, industrial by-products, and construction debris-in infrastructure development. It evaluates their structural performance, environmental impact, and economic viability in road construction, concrete composites, and urban infrastructure. The paper identifies global best practices and presents a roadmap for adopting sustainable construction materials at scale. The review aims to bridge the gap between research and implementation, helping to shape policy and engineering practice.

Fly ash geopolymer requires rather long heat curing to obtain reasonable strength development at an early age. However, the long heat curing period limits the application of the fly ash geopolymer. High strength development and a reduction in heat curing duration have been considered for energy saving. Therefore, this research proposed a process using 90-W microwave radiation for 5 min followed by conventional heat curing for high-calcium fly ash geopolymer. Results showed that the compressive strengths of geopolymer with microwave radiation followed by conventional heat curing were comparable to those of the control cured at 65 °C for 24 h. Microwave radiation gave the enhanced densification. In addition, SEM images showed that the gels formed on the fly ash particles owing to the promoted dissolution of amorphous phases from fly ash. This method accelerated the geopolymerization and gave the high compressive strength comparable to the conventional curing.

This research aimed to investigate the potential of using alkali activation technology to valorize steel slag and bauxite residue for the production of high-performance pavement blocks. By utilizing these industrial by-products, the study seeks to reduce their environmental impact and support the development of sustainable construction materials. Lab-scale testing showed that bauxite pavers showed a decrease in mechanical strength with increasing replacement of ordinary Portland cement. Partial replacement up to 20% still exceeded 30 MPa in compressive strength. Steel slag-based pavers achieved the 30 MPa threshold required for the application with selected mix designs. Pilot-scale productionoptimized formulations and standards testing, including freeze-thaw resistance, confirmed the technical viability of these products. Life cycle analysis indicated a 25-27% reduction in CO 2 emissions for slag-based tiles compared to traditional concrete tiles. Moreover, using industrial residue reduced mineral resource depletion. This study examined the properties of the resulting alkali-activated binders, their ecological benefits, and their performance compared to conventional materials. Through a comprehensive analysis of these applications, our research promotes the circular economy and the advancement of sustainable construction products.

Efflorescence, a time-dependent and water-driven phenomenon, is a major concern in alkali-activated materials (AAMs), impacting their practical use and preservation in a time-frozen state for post-characterisation. Although a method for stopping chemical reactions in conventional cements exists, it is time-consuming and not chemical-free. Therefore, this study explored the effects of low-power microwave-induced dehydration on efflorescence, mechanical performance, and structural integrity in AAMs, to create an alternative and more "user-friendly" dehydration method. For this purpose, several mixtures based on secondary raw (slag, fly ash, glass wool, and rock wool) and non-waste (metakaolin) materials were activated with a commercial Na-silicate solution in ratios that promoted or prevented efflorescence. Characterisation techniques, including Fourier-transform infrared spectroscopy and X-ray diffraction, showed that microwave dehydration effectively removed water without altering crystallinity, while mercury intrusion porosimetry and compressive strength tests confirmed increased porosity. In addition to being an efficient, time-saving, and solvent-free manner of stopping the reactions in AAMs, microwave irradiation emerged as an innovative, chemical-free method for evaluating curing finalisation and engineering foams in a stage when all other existing methods fail. However, the artificially provoked efflorescence in aged dehydrated AAMs connected the slipperiness of AAM with the instant extraction of Na, which raised the need for further research into alternative alkali replacements to evaluate the practical use of AAM.

I hereby certify that this thesis is the result of my own investigations and calculations. No part of it has been submitted for any degree other than 'Doctor of Philosophy' at the Newcastle University and all references are appropriately acknowledged.

This work reports and describes a novel alkali-activated metakaolin as a potential binder material for the granulation of zeolites, which are widely used as CO 2 adsorbents. The alkali-activated binders are zeolite-like materials, resulting in good material compatibility with zeolite-based adsorbents. A major problem during the granulation of zeolites is that their adsorption capacities decrease by about 15-20%, because typical binder materials (for example bentonite or kaolin clay) are inactive towards CO 2 adsorption. A possible pathway to solve this problem is to introduce a novel binder that is also able to sorb CO 2 . In such a case, a binder plays a dual role, acting both as a binding material and as a sorbent. However, it is important that, alongside the adsorptive properties, a novel binder material must fulfil mechanical and morphological requirements. Thus, in this work, physical and mechanical properties of this novel binder for zeolite granulation for CO 2 adsorption are studied. Alkali-activated metakaolin was found to be efficient and competitive as a binder material, when mechanical and physical properties were concerned. The compressive strengths of most of the obtained binders reported in this work are above the compressive strength threshold of 10 MPa. The future work on this novel binder will be conducted, which includes granulation-related details and the CO 2 adsorptive properties of the novel binder material. Metakaolin was used as a precursor for alkali-activated binders. Binders were synthesized using varying molarity of a NaOH solution and at varying curing conditions. The final products were characterized using density measurements, compressive strength tests, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) analysis, and scanning electron microscopy (SEM).

Alkali-activated copper tailings based-pastes (AACTP) were synthesized using 90 wt% copper tailings and 10 wt% coal fly ash as the precursors, and water glass with sodium hydroxide as the alkaline activator. The effects of the formation pressure, the liquid/solid mass ratio of water to precursor materials, and the partial substitution of CaO for NaOH as the alkaline activator were investigated. The highest compressive strength of 40.9 MPa was obtained using a formation pressure of 20 MPa, a liquid/solid of 0.15, and a substitution of 20% CaO for NaOH as the alkaline activator. The characterization using a Mercury Intrusion Porosimeter (MIP) indicated that the formation pressure affected the pore structure, as well as the amount of the gel formed. XRD, FTIR, SEM and 29 Si NMR showed that a 20% CaO substitution for NaOH promoted the dissolution of raw materials and led to more [AlO 4 ] -being incorporated into the tetrahedron [SiO 4 ] backbone. Additionally, the gel formed in the AACTP was predominantly a N-A-S-H gel. Partial substitution of CaO for NaOH as alkaline activator did not lead to the formation of a C-S-H gel.

This study investigates the hydration kinetics, phase assemblages, and pore structure refinement in blended cement systems containing silica fume (SF), fly ash (FA), and ground granulated blast furnace slag (GGBFS). These supplementary cementitious materials (SCMs) were blended with Ordinary Portland Cement (OPC) to analyze their impact on hydration processes, strength development, and pore structure. Experimental techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) were utilized to evaluate the effects of each SCM in varying proportions. The results suggest that the incorporation of these materials enhances the pore structure refinement, reduces porosity, and improves the hydration efficiency, leading to a more sustainable and durable cementitious system. This paper provides a comprehensive understanding of the interactions between these SCMs during hydration and their contribution to improving cement properties.

Thin concrete inlays incorporating flowable fibrous concrete (FFC) mix designs as well as titanium dioxide (TiO2)containing photocatalytic cements are a promising pavement preservation solution. These multi-functional inlays offer enhanced constructability and structural properties while also benefiting the environment by reacting with harmful nitrogen oxides (NOx) and removing them from the near-road environment. Photocatalytic FFC mixes were prepared in the laboratory to verify feasibility of field application and to characterize how mixture and microstructural properties and environmental factors affect photocatalytic performance. Testing of fresh and hardened concrete confirmed the ease of application of photocatalytic FFC and its benefits to the pavement's structural properties, particularly to residual strength ratio and fracture toughness. Laboratory photoreactor testing of mortar samples established that photocatalytic FFC is an effective tool to mitigate NOx pollution in the urban environment. Carbonation of the sample surface was shown to have the potential to significantly reduce NOx removal ability, but this effect could be curtailed by replacing some of the cement with fly ash or increasing TiO2 content by mass of cement. Spectrophotometer testing showed that reflectance of the mortar samples also factored into photocatalytic performance. More reflective specimens demonstrated greater NOx removal ability, which was most apparent when comparing the performance of white cement specimens to gray cement specimens. Finally, analysis of cement paste specimens using scanning electron microscopy (SEM) and related techniques suggested the importance of porosity to photocatalytic ability. These findings will be useful in helping design and optimize photocatalytic concrete mix designs for applications in pavements and other structures. Based on the results of the mixes and materials tested, a white cement photocatalytic concrete with 15% fly ash replacement would offer the most optimal balance between high photocatalytic efficiency and resilience to carbonation.

Alkali-activated composites are significant materials in reducing CO2 emis-
sions and ensuring sustainability. With the increasing concerns about cli-
mate change globally, the interest in alkali-activated materials has also
increased. Researching different fibers has very important potential in this
area. This study aims to make alkali-activated concretes widespread in the
concrete sector by using the materials common in conventional concretes
and ensuring that alkali-activated concretes are an alternative in terms of
sustainability. Experimental studies were conducted to examine the mech-
anical, durability, and microstructural properties (SEM) of slag-based alkali-
activated concrete (AASC) reinforced with three various fibers. The fibers,
polypropylene (PP), polyamide (PA), and steel (ST), were used with two
ratios (%0.4 and %0.8 by vol.). Compressive, splitting tensile, and flexural
strength tests were carried out at 28 and 90 days. In terms of durability
properties, the samples were exposed to high temperatures
(300–600–900 C) and freeze-thaw test (250 cycles). The results showed
that the addition of fibers improved the strength and durability properties;
for instance, the existence of steel and polypropylene fibers increased the
flexural toughness factor values by 430% and 260%, respectively.
Moreover, the compressive strength of the fibrous samples exposed to
900 C was obtained in the range of 6-23 MPa.

This study investigated the development of artificial aggregates using copper tailings activated by sodium silicate via granulation. Five different mixes were prepared by incorporating varying amounts of ground granulated blast furnace slag (GGBS) and sodium silicate. The granulation process was performed in a rotating disk granulator, with water sprayed onto the dry mixture to facilitate binding. The resulting aggregates, ranging from 5 to 25 mm in diameter, were cured in a humid environment for 3, 7, and 28 d. The aggregates were then tested for size distribution, oven-dried density, water absorption, crushing strength, and individual-granule strength. Microstructural analysis was conducted using scanning electron microscopy (SEM) and X-ray computed tomography (XCT). The results showed that the addition of GGBS significantly improved the properties of the artificial aggregates, resulting in a higher density, lower water absorption, and increased strength.XCT images revealed a more refined pore structure with smaller and more evenly distributed pores in the GGBS-containing samples. The crushing strength and individual granule strength followed a Weibull distribution, with the GGBS samples exhibiting higher strength values. SEM analysis confirmed the formation of N-AS -H gel in the GGBS samples, which acted as a binding phase and improved the microstructure. These findings demonstrate the potential of using copper tailings and GGBS to produce sustainable artificial aggregates with enhanced properties for construction applications.

Here we present a geopolymer as a sustainable alternative for cements. The geopolymer binder is presented in a dry form (dry mixing method). The geopolymer has demonstrated to be ideal candidate to mitigate the typical carbon footprint emissions of cements, such as Portland. The potential global benefits include a reduction of up to 1480 million tons of CO 2 per year when compare with Portland cement. In this design, it is proposed an alkaliactivated cementitious material that is made out of a mix of silica-rich sand and sodium carbonate. Such sand has 80-85 wt% SiO 2 and 15-20 wt% mixed rock grain. This composition is processed at temperatures around 850 °C that is 650 °C less than that for Portland cements. One of the benefits is that the use of limestone is eliminated resulting in such reductions in CO 2 emissions. The emission analysis is carried during a calcination process used to analyze the decarbonation or CO 2 emission step. This work presents a complementary characterization of the products including an infrared spectroscopy analysis and thermogravimetry.

Here we present a geopolymer as a sustainable alternative for cements. The geopolymer binder is presented in a dry form (dry mixing method). The geopolymer has demonstrated to be ideal candidate to mitigate the typical carbon footprint emissions of cements, such as Portland. The potential global benefits include a reduction of up to 1480 million tons of CO 2 per year when compare with Portland cement. In this design, it is proposed an alkaliactivated cementitious material that is made out of a mix of silica-rich sand and sodium carbonate. Such sand has 80-85 wt% SiO 2 and 15-20 wt% mixed rock grain. This composition is processed at temperatures around 850 °C that is 650 °C less than that for Portland cements. One of the benefits is that the use of limestone is eliminated resulting in such reductions in CO 2 emissions. The emission analysis is carried during a calcination process used to analyze the decarbonation or CO 2 emission step. This work presents a complementary characterization of the products including an infrared spectroscopy analysis and thermogravimetry.

The use of clay-based waste as an aggregate for concrete production is an amply studied procedure. Nonetheless, research on the use of this recycled aggregate to prepare alkaline cement mortars and concretes has yet to be forthcoming. The present study aimed to determine: the behaviour of this waste as a pozzolan in OPC systems, the mechanical strength in OPC, alkali-activated slag (AAS) and fly ash (AAFA) mortars and the effect of partial replacement of the slag and ash themselves with ground fractions of the waste. The pozzolanic behaviour of clay-based waste was confirmed. Replacing up to 20 % of siliceous aggregate with waste aggregate in OPC mortars induced a decline in 7 day strength (around 23 wt. %). The behaviour of waste aggregate in AAMs mortars, in turn, was observed to depend on the nature of the aluminosilicate and the replacement ratio used. When 20 % of siliceous aggregate was replaced by waste aggregate in AAS mortars, the 7 day strength values remained the same (40...

S t r e s z c z e n i e W referacie przedstawiono rezultaty wybranych analiz wykonanych przy użyciu sztucznych sieci neuronowych aby zbadać wpływ składu betonu na jego mrozoodporność. Najprostszym sposobem zapewnienia mrozoodporności jest właściwe napowietrzenie z odpowiednim rozstawem porów powietrznych. Pierwszym etapem tworzenia sieci było zebranie informacji zawierających informację o składzie mieszanki betonowej, właściwościach fizycznych i strukturze wewnętrznej badanych betonów (absorpcja kapilarna, przepuszczalność, wytrzymałość na ściskanie) oraz przeprowadzenie testów mrozoodporności zgodnie z PN-B-06250:1988. Zebrane dane dotyczyły betonów wykonanych na cementach CEM I, CEM II/A,B-S i CEM III/A, napowietrzonych lub nienapowietrzonych. W zależności od straty wytrzymałości próbek zamrażanych metodą zwykłą PN po 150 cyklach zamrażania-rozmrażania wprowadzono pojęcie 4 klas mrozoodporności. K e y w o r d s : Air entrainment; ANN Model; Durability; Frost resistance; GGBFS conc...

Alkali-activated materials (AAMs), which utilize industrial by-products, present a sustainable and highperformance alternative to Portland cement. However, ensuring their reliability depends on their long-term durability under harsh environmental conditions. There are a limited number of studies on the durability of AAMs concerning alkali-silica reaction (ASR) and its adverse effects on compressive strength, and the results of alkali content's impact on ASR are frequently inconsistent. This research has investigated the ASR performance in the alkali-activated slag (AAS) system using reactive aggregates to address this issue. The impacts of alkali activators' dosage and silicate modulus on ASR performance were examined, aiming to identify the conditions that achieved the highest compressive strength and expansion due to ASR. Additionally, this research investigated how accessible alkali concentration affects the mechanical properties and the ASR in AAMs. Finally, the study investigated the potential for improving durability and mitigating ASR in binders containing mid-grade calcined clay (CC). Results indicated that mortars with a 10 % alkali dosage and a silicate modulus of 1 were optimal for further investigation regarding mechanical properties and ASR. Additionally, the ASR reaction significantly intensified when the available alkali from the exposure solution increased. Hybrid systems with optimal replacement of CC were less susceptible to ASR-induced expansion than AAS systems, likely due to the reacted aluminum content present in CC. Replacing 10 wt% of slag with mid-grade CC significantly reduces expansion during accelerated tests, even in high-alkali concentration exposure solutions (HS condition). Despite a slight decrease in compressive strength compared to the control mixture in standard curing condition (immersing in water at 80 ºC), there was a notable lower rate of expansion and a smaller decrease in compressive strength due to ASR in ASR curing condition (immersing in NaOH solution at 80 ºC).

The Special Issue “Innovative Solutions for Concrete Applications” presents recent developments in the field of concrete technology and its applications. The articles and state-of-the-art reviews highlight the key themes such as sustainability, performance, durability, cost, environmental impact, recycling, and construction waste management. It also explores emerging techniques and innovations, including alkali-activated concrete, bacterial concrete, crumb rubber concrete, foamed concrete, waste-based concrete composites, and the reuse of construction and demolition waste. Sustainable concrete alternatives, innovative materials, and improved recycling and mixing techniques offer significant opportunities to reduce the environmental impact of concrete. However, challenges related to cost, long-term durability, and the application of life cycle assessment and life cycle cost analysis still need to be addressed through ongoing research. Furthermore, technologies such as three-dimensional concrete printing present advanced opportunities for innovation in the construction industry.

The geopolymer introduced by Davidovits is a new binder for making concrete as an alternative to ordinary Portland cement. One of the materials used to make geopolymers is fly ash. The annual worldwide production of fly ash is estimated to be around 500 Mt. In making geopolymers with fly ash, scientists usually use activators such as silicate and aluminate solutions, as well as with kaolinite. The geopolymerization process is related to the metal oxide ratio of the activator solution. Geopolymers can withstand temperatures up to about 600°C, so they are fire/heat resistant. This paper describes the role of the comparison of dominant elements in a mixture of geopolymer paste with fly ash and alkali which produces the best quality based on compressive strength, where there is an effect of the ratio of alkali on the compressive strength of geopolymer paste. Almost all of the highest compressive strength obtained did not follow the Davidovits rule. This is caused by other factors that affect the compressive strength such as the content of elements such as Si and Al in fly ash and the curing temperature. However, the volumetric and mechanical properties of the artificial aggregate (geopolymer fly ash application) meet the requirements as a road material. It's just that the absorption value is above the requirements (>3%). Seeing the properties of these geopolymers, there is hope to be developed into materials for building materials.

Hybrid fiber reinforced concrete (HFRC) consisting of two or more different types of fibers has been widely investigated because of its superior mechanical properties. In the present study, the effect of the addition of steel (0.25%, 0.5%, 0.75% and 1% of concrete volume) and Polypropylene (0.2%, 0.4% and 0.6% of concrete volume) fibers on the surface scaling resistance of concrete, depth of penetration of water, and compressive strength of concrete is investigated. The permeability test is conducted for all the specimens to measure the depth of penetration of water under pressure. Moreover, scaling resistance of concrete subjected to freezing and thawing cycles in the presence of salt solution is assessed to simulate the durability of concrete under field exposure conditions. The results showed that the addition of fibers increases the permeability of concrete. However, it enhances the scaling resistance and compressive strength of concrete. The mixture containing 0.4% of Polypropylene (PP) fibers and 0.75% of steel fibers demonstrated the highest scaling resistance since the scaled materials in this mixture were almost half weight of the materials scaled from the control mixture after 84 cycles of freezing and thawing. Increasing the scaling resistance of concrete leads to a better long-term serviceability performance of HFRC compared to plain concrete, making these composites a great choice for application in environments exposed to cold weather.

In this study, prediction and optimization of Na concentration, Ms modulus (total ratio of SiO₂/Na₂O in alkali activators), fly ash (FA) and granulated blast furnace slag (GGBFS) contents of geopolymer mortars produced by vapour curing in a prefabricated element production plant were carried out focusing on compressive strength, cost and environmental impacts. After the compressive strengths of geopolymer mortars made with comprehensive mixture designs were obtained experimentally, an artificial neural network (ANN) model was developed to estimate the compressive strength from Na, Ms, FA and GGBFS input variables. Moreover, primary energy (PE), global warming potential (GWP, equivalent-CO₂ emission) and cost were optimized separately in different compressive strength ranges with ANN predictions. The efficiency optimizations were also performed to evaluate the cost and environmental impacts per unit compressive strength. As a result of the optimizations, the maximum compressive strength of geopolymer mortar coded with 0.41 FA/0.59 GGBFS (Na = 6.75, Ms = 0.83) was determined as 54.42 MPa. The most efficient geopolymer mortar mixtures within the optimization ranges were 0.29 FA/0.71 GGBFS (Na = 3, Ms = 0.25, 27.79 MPa) regarding GWP with 1.82 (kgCO₂/m³)/MPa, 0.34 FA/0.66 GGBFS (Na = 3, Ms = 0.55, 31.49 MPa) regarding PE with 27 (MJ/m³)/MPa, and 0.38 FA/0.62 GGBFS (Na = 6.56, Ms = 0.66, 52.50 MPa) considering cost efficiency with 2.29 (€/m³)/MPa. FA + GGBFS based geopolymer mortars stand out as the most sustainable options in terms of energy efficiency and carbon footprint with lower PE/MPa and GWP/MPa values compared to 100 %FA and 100 %GGBFS based geopolymer mortars. Optimized geopolymer mortars are 78 %, 35 %, and 42 % more efficient than traditional OPC based mortars in terms of CO₂ emissions, energy consumption, and cost, respectively.

Geopolymers are inorganic materials that have been studied since 1972 due to their advantages over Portland cement concrete, such as greater inertia, lower CO₂ emissions, and greater chemical and fire resistance. The use of the ultrasonic velocity propagation technique, a non-destructive and widely used method for evaluating the quality of Portland cement concrete, has also been applied to geopolymers. However, the chemical composition and proportions of the materials used to produce geopolymers affect properties such as density, porosity, and absorption, which directly influence the propagation of ultrasonic waves. These factors indicate that the ultrasonic velocity propagation technique may not be entirely reliable for qualifying geopolymers, which is why more research on the subject is needed. Given this scenario, this study investigated how variations in the composition of geopolymer samples can impact the propagation speed of ultrasonic waves, considering an experimental design using response surfaces and taking into account the following variables: propagation speed of ultrasonic waves, compressive strength, absorption and specific mass. The results obtained demonstrated that the use of sodium silicate in geopolymer formulations to evaluate the propagation speed of ultrasonic waves, considering a significance level of 5%, was significant (p = 0.002), that is, less than p0.

3D printing with concrete is a new, innovative technology with promising benefits for the construction industry. Additive manufacturing of concrete has the potential to save costs on labor, formwork, and material and is a more sustainable means of producing the built environment for the future. Although potential exists, there are many obstacles to overcome before concrete 3D printing can be applied on a construction scale. This project first aimed to determine an optimal mixture design for printable concrete by experimenting with two different viscosity modifying admixtures: Acti-Gel and polyacrylamide. Polyacrylamide, a polymer-based flocculent, was found to enhance the rheology and cohesiveness of concrete in doses as low as 0.6% by weight of binder. Secondly, this project investigated improvements to the interfacial bond between layers of concrete using a liquid adhesive and sinusoidal layer geometries. Although there was insufficient data to make specific conclusions on the ideal bond improvement, test results indicated an enhanced shear strength from the sinusoidal layer geometries and an enhanced tensile strength from the adhesive. Finally, scanning electron microscopy completed on the interface between printed layers with polyacrylamide revealed the polymer's microstructure bridging across the interface and anchoring to the hydrated C-S-H structure. It is concluded that polyacrylamide is the most suitable viscosity modifying admixture for printable concrete. Our project team would like to recognize the contributions of a few individuals to this project. Firstly, we thank Professor Nima Rahbar for inspiring this research into the innovative field of concrete 3D printing. Without his guidance and technical knowledge, this project would not have been possible. Secondly, we acknowledge Jessica Rosewitz for her commitment to the success of this project. Without being asked, Jessica took on the role of co-advisor for this project providing assistance with lab work, sample preparation, technical analysis, and writing on a day to day basis. Her contributions to this project were selfless and impactful. Russel Lang assisted with lab work and the ordering of materials, and we acknowledge and thank him for his contributions. Finally, this group acknowledges Mason Guarino from SSG Pools for generously donating two admixtures for use in this project. As a member of the American Shotcrete Association, Mason also invited us to observe the shotcrete process on a construction site, and provided information and advice which was critical to the success of this project. Through research and iterative design, an economical mix design was developed for enhancing the performance of printed concrete in structural applications. The scope of the project included two main components. The project began with a literature review on the most current research and developments in the field of concrete 3D printing. It was discovered through our research that one of the main difficulties with printed structures is the lack of Professional licensure statement Professional licensure indicates that an engineer has a certain level of competency within his or her engineering discipline. For civil engineers, a professional engineering license allows an engineer to prepare, sign, and seal engineering plans and drawings. Licensure is a legal requirement for private and consulting engineers who are responsible for their work. It is also a requirement for many governmental engineering jobs as well as educational positions in many states. However, professional licensure is not easily obtained. It is a long-term commitment that lasts for the entire career of a practicing engineer. To begin with, an engineer must complete at least a four-year college degree from an ABET-accredited engineering program and pass the Fundamentals of Engineering (FE) Exam to become an Engineer in Training (EIT). The FE exam is a six hour exam comprised of 110 questions. Following this, an engineer has to accumulate four years of experience underneath a licensed professional engineer. Accurate records of this experience need to be kept and endorsed by a supervising professional engineer. These records are part of the review process as each state requires a detailed work history before the final step toward licensure can be taken: successful completion of Principles and Practice of Engineering (PE) exam. Once an engineer's credentials have been verified, he or she can register to take the PE exam. It is an eight hour exam which consists of 80 questions covering all five areas of civil engineering: construction, geotechnical, structural, transportation, and water resources and environment. Both the FE and PE exams are organized by the National Council of Examiners for Engineering and Surveying (NCEES). Once professional licensure is obtained, the process of maintaining licensure through continued industry education begins. Each state has varying requirements for maintaining professional licensure, but in 42 states, there is a certain standard of continued education that must be completed before an engineer's license can be renewed. There are online courses, conferences, webinars, and other forms of continuing education for professional engineers, all of which count for a certain number of Professional Development Hours (PDHs). Each state has its own requirements as to how many PDHs are needed to renew a license and how often an engineer needs to renew his or her license. It is important for a professional engineer to remain up to date on the requirements of any of the states within which he or she is registered. There is some reciprocity between states that allows engineers to obtain and maintain a PE license in multiple states, but in some instances the PE exam must be retaken to obtain a license in another state depending on the requirements. Professional licensure is crucial for the public, the individual, and the civil engineering profession as a whole. Prior to 1907, no state regulated who was permitted to offer engineering services to the public. This meant that there was no standard method for designating who was and was not competent enough to practice as an engineer which was a significant danger to the public. However, in 1907, Wyoming passed the first engineering licensure law which established a minimum level of competency for engineers to protect the safety of the public and uphold a certain standard of ethics. Today, professional licensure continues to uphold the safety of the public. It is also beneficial to the individual. It enables engineers to take on more responsibility and often reach a higher and more lucrative position within the industry. Further, becoming a professional engineer opens the gate to a community of high achieving individuals and resources that can help an engineer develop his or her career. It is a mark of integrity and achievement that sets an engineer apart in the industry. Finally, professional licensure is beneficial to the civil engineering profession as it ensures that the field of civil engineering continues to develop and grow, continually reaching higher standards of safety and creativity.

3D printing with concrete is a new, innovative technology with promising benefits for the construction industry. Additive manufacturing of concrete has the potential to save costs on labor, formwork, and material and is a more sustainable means of producing the built environment for the future. Although potential exists, there are many obstacles to overcome before concrete 3D printing can be applied on a construction scale. This project first aimed to determine an optimal mixture design for printable concrete by experimenting with two different viscosity modifying admixtures: Acti-Gel and polyacrylamide. Polyacrylamide, a polymer-based flocculent, was found to enhance the rheology and cohesiveness of concrete in doses as low as 0.6% by weight of binder. Secondly, this project investigated improvements to the interfacial bond between layers of concrete using a liquid adhesive and sinusoidal layer geometries. Although there was insufficient data to make specific conclusions on the ideal bond improvement, test results indicated an enhanced shear strength from the sinusoidal layer geometries and an enhanced tensile strength from the adhesive. Finally, scanning electron microscopy completed on the interface between printed layers with polyacrylamide revealed the polymer's microstructure bridging across the interface and anchoring to the hydrated C-S-H structure. It is concluded that polyacrylamide is the most suitable viscosity modifying admixture for printable concrete. Our project team would like to recognize the contributions of a few individuals to this project. Firstly, we thank Professor Nima Rahbar for inspiring this research into the innovative field of concrete 3D printing. Without his guidance and technical knowledge, this project would not have been possible. Secondly, we acknowledge Jessica Rosewitz for her commitment to the success of this project. Without being asked, Jessica took on the role of co-advisor for this project providing assistance with lab work, sample preparation, technical analysis, and writing on a day to day basis. Her contributions to this project were selfless and impactful. Russel Lang assisted with lab work and the ordering of materials, and we acknowledge and thank him for his contributions. Finally, this group acknowledges Mason Guarino from SSG Pools for generously donating two admixtures for use in this project. As a member of the American Shotcrete Association, Mason also invited us to observe the shotcrete process on a construction site, and provided information and advice which was critical to the success of this project. Through research and iterative design, an economical mix design was developed for enhancing the performance of printed concrete in structural applications. The scope of the project included two main components. The project began with a literature review on the most current research and developments in the field of concrete 3D printing. It was discovered through our research that one of the main difficulties with printed structures is the lack of Professional licensure statement Professional licensure indicates that an engineer has a certain level of competency within his or her engineering discipline. For civil engineers, a professional engineering license allows an engineer to prepare, sign, and seal engineering plans and drawings. Licensure is a legal requirement for private and consulting engineers who are responsible for their work. It is also a requirement for many governmental engineering jobs as well as educational positions in many states. However, professional licensure is not easily obtained. It is a long-term commitment that lasts for the entire career of a practicing engineer. To begin with, an engineer must complete at least a four-year college degree from an ABET-accredited engineering program and pass the Fundamentals of Engineering (FE) Exam to become an Engineer in Training (EIT). The FE exam is a six hour exam comprised of 110 questions. Following this, an engineer has to accumulate four years of experience underneath a licensed professional engineer. Accurate records of this experience need to be kept and endorsed by a supervising professional engineer. These records are part of the review process as each state requires a detailed work history before the final step toward licensure can be taken: successful completion of Principles and Practice of Engineering (PE) exam. Once an engineer's credentials have been verified, he or she can register to take the PE exam. It is an eight hour exam which consists of 80 questions covering all five areas of civil engineering: construction, geotechnical, structural, transportation, and water resources and environment. Both the FE and PE exams are organized by the National Council of Examiners for Engineering and Surveying (NCEES). Once professional licensure is obtained, the process of maintaining licensure through continued industry education begins. Each state has varying requirements for maintaining professional licensure, but in 42 states, there is a certain standard of continued education that must be completed before an engineer's license can be renewed. There are online courses, conferences, webinars, and other forms of continuing education for professional engineers, all of which count for a certain number of Professional Development Hours (PDHs). Each state has its own requirements as to how many PDHs are needed to renew a license and how often an engineer needs to renew his or her license. It is important for a professional engineer to remain up to date on the requirements of any of the states within which he or she is registered. There is some reciprocity between states that allows engineers to obtain and maintain a PE license in multiple states, but in some instances the PE exam must be retaken to obtain a license in another state depending on the requirements. Professional licensure is crucial for the public, the individual, and the civil engineering profession as a whole. Prior to 1907, no state regulated who was permitted to offer engineering services to the public. This meant that there was no standard method for designating who was and was not competent enough to practice as an engineer which was a significant danger to the public. However, in 1907, Wyoming passed the first engineering licensure law which established a minimum level of competency for engineers to protect the safety of the public and uphold a certain standard of ethics. Today, professional licensure continues to uphold the safety of the public. It is also beneficial to the individual. It enables engineers to take on more responsibility and often reach a higher and more lucrative position within the industry. Further, becoming a professional engineer opens the gate to a community of high achieving individuals and resources that can help an engineer develop his or her career. It is a mark of integrity and achievement that sets an engineer apart in the industry. Finally, professional licensure is beneficial to the civil engineering profession as it ensures that the field of civil engineering continues to develop and grow, continually reaching higher standards of safety and creativity.

Due to the construction industry's dependency on Portland cement, approximately 5-8% of global CO₂ emissions are attributed to its production, which requires an alternative sustainable solution. Recently, alkali-activated materials (AAMs), particularly originating from ground granulated blast-furnace slag (GGBFS), have emerged and presented sustainable alternatives due to their lower carbon footprint and better mechanical properties. The study focuses on its application to hybrid GGBFS activation utilizing NaOH, Na₂SiO₃, and alkali sulfates in a quest to develop high early strength selfcompacting concrete (SCC). This study investigates the potential of SCC incorporating alkali-activated slag (AAS) around 80% Silica Fume (SF) 20% as a complete replacement for Portland cement. Before the test date, samples were prepared under standardized conditions and cured in a tank with limewater saturated at 23±1C°. Compressive strength tests were conducted on 150 × 300 mm cylindrical samples at 1, 7, and 28 days. The findings indicate that SCC using AAS could arrive at an early-age compressive strength of around 22 MPa at 1-day age of curing. The hybrid activation system, powered by NaOH, Na₂SiO₃, and alkali sulfates, shows improvements in early-age strength and durability. This system offers a sustainable alternative to conventional cement, reducing CO₂ emissions while maintaining excellent mechanical properties.

Geopolymers are the eco-friendly binders derived from activation of alumina silicates such as fly ash and metakaolin with alkaline activators. Ground perlite, a volcanic alumina silicate, has a potential to be a precursor material for geopolymer production thanks to its high SiO2 content and amorphous form. This paper presents the investigation of geopolymer production with ground perlite and NaOH. For this purpose, mortar mixtures are made with four different NaOH solutions (3M, 6M, 9M and 12M). Mortar specimens with dimensions of 4*4*16 cm are taken from the mixtures and heat curing process is applied to the specimens after casting. The flexural and compressive strength tests are conducted on the mortar specimens at 7 and 28 days of curing. The test results showed that the flexural and compressive strengths of the ground perlite based geopolymer mortars increase as the increment in molarity of NaOH solution, significantly.

Numerous research efforts on metakaolin as a supplementary cementitious material (SCM) have been undertaken in the past 20 years. This material, while relatively expensive mainly due to low production volumes worldwide, nevertheless has a significantly lower production cost than Portland cement. However, the industry remains tentative in considering metakaolin in concrete. This paper takes the view that industry should consider investing in the production and application of metakaolin in appropriate concrete projects, particularly in aggressive environments where plain Portland cement may be inadequate, and where other SCMs may not be readily available. A major contribution of the paper is a global review of recent studies on the use of metakaolin in different types of concrete. This international experience is then compared with results from a study on the durability performance of metakaolin concrete using local materials in the Western Cape province of South Africa, as a means of concrete performance improvement. The study investigated concrete durability properties: penetrability (sorptivity, permeability, conductivity and diffusion), mitigation of Alkali-Silica Reaction (ASR), and carbonation resistance. The concretes were prepared with three water-binder ratios (0.4, 0.5 and 0.6), and with metakaolin replacement levels of 0% (control), 10%, 15% and 20%. Performance results show that, with increasing metakaolin content, the transport properties of concrete are considerably improved, ASR expansion due to a highly reactive local aggregate decreases to non-deleterious levels, while no detrimental effect on carbonation is observed. Thus, metakaolin could serve as a valuable SCM to enhance the durability performance of concrete in local aggressive environments.

In recent years, the geopolymer will considerably replace the role of cement in the construction field. Generally, geopolymers have advantageous characteristics such as minimal shrinkage, minimal creep, and high compressive strength, respectively. In the literature, some of the geopolymer-based concrete is designed which attains low compressive strength and inadequate compressive strength computation. Hence, in this research paper, lightweight geopolymer mortar with base material for the based concrete mix is designed. The base material is considered as fly ash (FA) and alkali-activated slag (AAFS). The main components of lightweight geopolymer mortar are insubstantial burnish aggregate and AAFS binder or alkali-activated FA. The mixed concrete design compressive strength is computed with the Artificial Intelligence (AI) technique. Here, Adaptive Neuro-Fuzzy Inference Controller (ANFIS) with Salp Swarm Optimization (SSO) is utilized to compute the urging force of the concrete mix. SSO is used to compute the optimal learning rate to find out the urging force of the concrete. The preliminary parameter's potential was inspected with the relations of variant urging force in insubstantial geopolymer mortar. The performance is evaluated by changing the temperature and binder content. The proposed method with an intended concrete mix result illustrates the performance. The proposed method is compared with existing methods of Artificial Neural Network (ANN).

The imperative to find sustainable alternatives to conventional cement, given its energy-intensive production and significant environmental impact, has driven research into alternative binder materials for civil infrastructure. This paper explores Geopolymer concrete (GPC), a polymer-based binder technology, as a promising solution to reduce the environmental footprint associated with traditional cement production. The study meticulously examines various aspects of GPC, focusing on its impact on crucial durability properties for infrastructure applications. This includes an in-depth analysis of GPC properties, elucidating characteristics influencing performance. In addition to fundamental properties, the paper critically evaluates the resistance of geopolymer pastes and concrete to a spectrum of extreme conditions. The discussion spans testing methodologies for both heat-and ambient-cured geopolymers, providing insights into their performance and durability across diverse environmental challenges. This comprehensive review aims to enhance the understanding of GPC technology, offering valuable insights for researchers, engineers, and industry professionals committed to sustainable and resilient infrastructure solutions.

Geopolymer binders are pulling in the consideration of scientists as replacement to solidify binder in traditional concrete. In assembling 1 ton of concrete, 1 ton of CO2 is discharged into the climate. In this manner, substitution of concrete by geopolymer material in development industry diminishes contamination by two different ways: decrease in carbon dioxide emanation into climate by diminishing the utilization of concrete and usage of fly ash, which is another waste item heaping in colossal amounts in warm force plants. To inspect the utilization of geopolymer as a substitution to solidify, it is basic to explore ordinary consistency, last setting time and compressive strength of geopolymer which are normal tests for the most part led for concrete. The method embraced for deciding the ordinary consistency, last setting time and compressive strength of geopolymer is same as the method received for concrete. In these tests, concrete is supplanted by geopolymer material and water...