This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
A unified critical state model has been developed for both clean sand and silty sand using the mo... more A unified critical state model has been developed for both clean sand and silty sand using the modified Cam-clay model (MCC). The main feature of the proposed model is a new critical state line equation in the e-ln(p) plane that is capable of handling both straight and curved test results. With this feature, the error in calculating plastic volumetric strain is eliminated in theory. Another crucial feature of the model is the transformed stress tensor based on the SMP (spatially mobilized plane) criterion, which takes into account the proper shear yield and failure of soil under three-dimensional stresses. Additionally, the proposed model applies the intergranular void ratio with the fines influence factor for silty sand. Only eight soil parameters are required for clean sand, and a total number of twelve soil parameters are needed for silty sand.
From the crisis of global warming, conservation of natural resources and economic growth, buildin... more From the crisis of global warming, conservation of natural resources and economic growth, buildingstructures and infrastructures with high performances are needed. Research on civil engineering is then highlyfocused on upgrading materials and developing new technologies to earn a brilliant solution both inengineering and global concerns. One of the smart technologies being developed and promoted is the socalled\new hybrid steel structure^ in which steel, the main structural element, and other structural materialssuch as fiber-reinforced polymer (FRP), glass and timber can be utilized appropriately. Ecological and modernstructure styles can be efficiently integrated with this new technology. Therefore, this technology may becomea new fundamental construction in the near future. This paper is, hence, aimed at introducing and discussingabout this new technology.
The corrosion of reinforcing steel in concrete structures is still a main problem and needed prot... more The corrosion of reinforcing steel in concrete structures is still a main problem and needed protection especially the structures subjected to aggressive environments. At present, an alternative is to use concrete reinforced with fiber-reinforced polymer (FRP) bars as FRP bars are noncorrosive. However, this technology is quite new for civil engineers. More importantly, the mechanical properties of FRP bars are different from those of steel bars. This paper is, therefore, aimed at introducing and discussing about this technology in the issues of mechanical and physical properties of FRP bars; advantages and disadvantages, research work and applications of concrete structures reinforced with FRP bars; and economic considerations as well as research work and applications in Thailand.
Alkali-activated binders/geopolymer and an application to environmental engineering
For environmental reason, new binders that can be used as Portland cement replacement materials a... more For environmental reason, new binders that can be used as Portland cement replacement materials are being needed. Recently, alkali-activated binders (AAB) and geopolymer have found increasing interest. As several research reports have showed that the two new binders are likely to have high potential to be developed and become an alternative to OPC. However, confusion in the classification of both binders is still there. This paper reviews knowledge about AAB and geopolymer including historical background, reaction mechanisms and reaction products. The similarities and differences of both binders are discussed. The application to environmental engineering on hazardous waste management using stabilization/solidification is also described.
Numerical simulation of fracture in unreinforced masonry
The aims of this thesis are to study the fracture behaviour in unreinforced masonry, to carry out... more The aims of this thesis are to study the fracture behaviour in unreinforced masonry, to carry out a limited experimental program on three-point bending (TPB) masonry panels and to develop a time-dependent fracture formulation for the study of mode I fracture in quasi-brittle materials. A micro-model for fracture in unreinforced masonry is developed using the concept of the discrete crack approach. All basic masonry failure modes are taken into account. To capture brick diagonal tensile cracking and masonry crushing, a linear compression cap is proposed with a criterion for defining the compression cap. The failure surface for brick and brick-mortar interfaces are modelled using a Mohr-Coulomb failure surface with a tension cut-off and a linear compression cap. The fracture formulation, in nonholonomic rate form within a quasi-prescribed displacement approach, is based on a piecewise-linear constitutive law and is in the form of a so-called ?linear complementarity problem? (LCP). The...
Many materials which are widely used in industries such as building, aircraft, aerospace, marine ... more Many materials which are widely used in industries such as building, aircraft, aerospace, marine and biological technology can undergo large nonlinear elastic deformations and have inherent anisotropic characteristics. To be able to utilize these materials efficiently and economically, better analytical methods and designs are needed. Hyperelastic constitutive modeling has appeared as an effective tool in continuum mechanics for characterizing large deformation materials. In this paper a hyperelastic model proposed for anisotropic materials is applied for example to soft tissues at large strains. The model is an extension of a model successfully used for the analysis of isotropic hyperelastic materials. The formulation is based on the invariant theory and polyconvexity. The model is decomposed into an isotropic part and an anisotropic part. The numerical results show a very good agreement with the experimental results.
The effects of several parameters on the workability and strength of alkali-activated high calciu... more The effects of several parameters on the workability and strength of alkali-activated high calcium fly ash (AAHCFA) concrete were investigated in this study. The AAHCFA concretes were activated with alkali sodium hydroxide solution (NaOH), sodium silicate solution (Na 2 SiO 3) and heat. Three alkali liquid to fly ash (L/S) ratios of 0.55, 0.60 and 0.65, three NaOH concentrations of 10, 15 and 20 molars (M) and three Na 2 SiO 3 /NaOH ratios of 1.0, 1.5 and 2.0 were used. The workability was obtained by measuring the slump and the compressive strength was tested to gauge the strength of concrete. The results revealed that the workability of AAHCFA concrete was related to the molar ratio of H 2 O/Na 2 O in activator, the NaOH concentration, and the L/S ratio. The improvement in compressive strength was mainly related to the increase in the NaOH concentrations. The strength was, however, reduced with the increase in the Na 2 SiO 3 /NaOH ratio. The obtained slumps were in the range of 70 to 260 mm and the 28-day compressive strength ranged from 9.0 to 47.5 MPa. The influence of delay time (the time taken from the completion of specimen casting to the start of heat curing), curing temperature and curing duration on compressive strength were also presented.
Advances in Materials Science and Engineering, 2015
This research focuses on evaluating the feasibility of utilizing bottom ash from coal burning pow... more This research focuses on evaluating the feasibility of utilizing bottom ash from coal burning power plants as a fine aggregate in cellular concrete with various foam contents. Flows of all mixtures were controlled within 45 ± 5% and used foam content at 30%, 40%, 50%, 60%, and 70% by volume of mixture. Bottom ash from Mae Moh power plant in Thailand was used to replace river sand at the rates of 0%, 25%, 50%, 75%, and 100% by volume of sand. Compressive strength, water absorption, and density of cellular concretes were determined at the ages of 7, 14, and 28 days. Nonlinear regression technique was developed to construct the mathematical models for predicting the compressive strength, water absorption, and density of cellular concrete. The results revealed that the density of cellular concrete decreased while the water absorption increased with an increase in replacement level of bottom ash. From the experimental results, it can be concluded that bottom ash can be used as fine aggre...
Performance and Economic Comparative Study of Interlocking Block and Clay Brick Buildings
Applied Mechanics and Materials, 2013
This paper presents the results of an inquiry into the comparative thermal performance and econom... more This paper presents the results of an inquiry into the comparative thermal performance and economic viability of interlocking block and clay brick. To this end, two test rooms of 2.4 m width, 2.4 m length and 2 m height were built. The first room was constructed using interlocking block wall whereas the second room used commercial clay brick wall. Data recorded included room temperature, inside and outside surfaces temperatures of all walls, and solar intensity. The experimental results showed that heat conducted better through the interlocking block than through the clay brick. This was not surprising because the thermal conductivity of the interlocking block is 234% higher than the clay brick. However, the cost of interlocking block wall was lower than the clay brick wall by 34.5%. An economic analysis indicates that the payback period of the clay brick in tandem with a 1 ton, split-type air-conditioner depends on the indoor set-point temperature. The payback period extends over a...
Properties of Reactive Powder Concrete Using Densified Silica Fume
Applied Mechanics and Materials, 2013
This paper presents some experimental results on the physical and mechanical properties of reacti... more This paper presents some experimental results on the physical and mechanical properties of reactive powder concrete (RPC) using two different characteristics of densified silica fume (f1 and f2). The silica fume/cement ratio (f/c) varied from 15% to 35% by weight. The flow, the micromorphology by scanning electron microscopy (SEM) and the compressive strength at the ages of 3, 7 and 28 days were studied. The effects of the silica fume agglomerations on the properties of the RPC were considered and discussed. The test results indicated that the properties of RPC depended on the type of silica fume, amount of silica fume and amount of superplasticizer used.
Uploads
Papers by Krit Chaimoon