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American Society for Testing and Materials

The fifth edition of "Numerical Methods for Engineers" continues its tradition of excellence. Instructors love this text because it is a comprehensive text that is easy to teach from. Students love it because it is written for them--with great pedagogy and clear explanations and examples throughout. The text features a broad array of applications, including all engineering disciplines. The revision retains the successful pedagogy of the prior editions. Chapra and Canale's unique approach opens each part of the text with sections called Motivation, Mathematical Background, and Orientation, preparing the student for what is to come in a motivating and engaging manner. Each part closes with an Epilogue containing sections called Trade-Offs, Important Relationships and Formulas, and Advanced Methods and Additional References. Much more than a summary, the Epilogue deepens understanding of what has been learned and provides a peek into more advanced methods. Approximately 80% of the end-of-chapter problems are revised or new to this edition. The expanded breadth of engineering disciplines covered is especially evident in the problems, which now cover such areas as biotechnology and biomedical engineering. Users will find use of software packages, specifically MATLAB and Excel with VBA. This includes material on developing MATLAB m-files and VBA macros.

Numerical methods for engineers

Structural and material performance of geopolymer concrete: A review

Use of geopolymer concrete for a cleaner and sustainable environment – A review of mechanical properties and microstructure

Environmentally sustainable repair materials with reduced carbon footprint have been in great demand by the construction industry worldwide. Gradual deterioration of concrete containing large quantities of Portland cement is inevitable, and requires repair or replacement. Numerous repair materials including cementitious mortars, polymer-modified cementitious mortars, resinous mortars, etc. have been utilized to rectify the problem. Cement-free geopolymer mortars prepared from waste materials with high content of silicate aluminum and alkaline activator solution are emerging as prominent sustainable repair materials. Geopolymer binders are preferred because they generate 70–80% less carbon dioxide with remarkably lesser greenhouse gas emissions than ordinary Portland cement. These new binders are highly sought-after due to their enhanced durability performance, sustainability, and environmental affability. This paper provides a comprehensive overview of state-of-the-art research on sustainable geopolymers for repairing deteriorated and damaged concrete structures as well as restoring their integrity. Present challenges and future prospects of various geopolymer mortars as repair materials are emphasized.

Geopolymer mortars as sustainable repair material: A comprehensive review

Advances in research and development of geopolymer concrete have made it a feasible alternative material for civil and infrastructural applications. However, currently, there is a gap in design methodology due to lack of knowledge on geopolymer concrete, which has been a significant barrier for engineers and designers. The current research addresses this gap, modeling an equivalent stress block of fly-ash-based geopolymer concrete, to enable the design of sections. It was found that the design parameters based on the standard codes are not well suited for the fly-ash-based geopolymer concrete structures. In addition, the elastic modulus model obtained from Ordinary Portland Cement concrete is inappropriate for fly-ash-based geopolymer. Therefore, in this study, the stress–strain relation, an elastic modulus model and equivalent stress block design parameters were obtained from experimental results, also using prior published data, for flexural strength predictions of fly-ash-based geopolymer concrete members. A simplified stress–strain relationship based on Thorenfeldt’s model, as well as the stress block design equations, was fit to test data. The results showed that the simplified stress–strain model is reasonably accurate. The prediction of flexural moment capacity based on the proposed design parameters correlated well with experimental test data. It was found that the nominal moment capacity using standard code design parameters was about 1.43 times higher than with the proposed design parameters.

Development of Equivalent Stress Block Parameters for Fly-Ash-Based Geopolymer Concrete

High early strength is the most important property of pavement repair materials to allow quick reopening to traffic. With this in mind, we have experimentally investigated geopolymers using low cost raw materials available in Thailand. The geopolymer mortar was metakaolin (MK), mixed with parawood ash (PWA, rubberwood ash) or oil palm ash (OPA) as binder agent. Rubberwood is often used as raw material for biomass power plants in Thailand, especially at latex glove factories and seafood factories, and burning rubberwood generates PWA. Both PWA and OPA are therefore low cost residual waste, locally available in mass quantities. The geopolymer samples were characterized for compressive strength, drying shrinkage, and bond strength to Portland cement mortar with slant shear test. The experimental design varied the contents of PWA and OPA and the heat curing time (1, 2 and 4 h) after hot mixture process. The hot mixture process resulted in very high early strength. In addition, we achieved high compressive strengths, low drying shrinkage, and very significant bond strength enhancement by use of the ashes.

https://downloads.hindawi.com/journals/amse/2013/764180.pdf

Development and Performance Evaluation of Very High Early Strength Geopolymer for Rapid Road Repair

This study reports on the microstructure, compressive strength, and drying shrinkage of metakaolin (MK) based geopolymers produced by partially replacing MK by oil palm ash (OPA). The OPA was used as raw material producing different molar ratios of SiO2/Al2O3 and CaO/SiO2. The geopolymer samples were cured at 80°C for 1, 2, or 4 hours and kept at ambient temperature until testing. The compressive strength was measured after 2, 6, and 24 hours and 7 and 28 days. The testing results revealed that the geopolymer with 5% OPA (SiO2 : Al2O3 = 2.88 : 1) gave the highest compressive strength. Scanning electron microscopy (SEM) indicated that the 5% OPA sample had a dense-compact matrix and less unreacted raw materials which contributed to the higher compressive strength. In the X-ray diffraction (XRD) patterns, the change of the crystalline phase after heat curing for 4 hours was easily detectable compared to the samples subjected to a shorter period of heat curing.

/pdf/performance-evaluation-and-microstructure-characterization-swg8zlm15d.pdf

Performance evaluation and microstructure characterization of metakaolin-based geopolymer containing oil palm ash.

Fiber reinforced polymer (FRP) composites are gaining acceptance in concrete structural applications due to their high ratio of strength/stiffness to self-weight and corrosion resistance. This study focused on the structural behavior and the performance of concrete columns internally reinforced with glass fiber reinforced plastic (GFRP) rebars. Twelve series of concrete columns with varied longitudinal reinforcement, cross section, concrete cover, and type of lateral reinforcement were tested under compression loading. The results show that the amount of GFRP longitudinal and lateral reinforcement slightly affects the column strength. The lateral reinforcement affects the confining pressure and inelastic deformation, and its contribution to the confined compressive strength increases with the GFRP reinforcement ratio. In addition, the confining pressure increases both concrete strength and deformability in the inelastic range. The confinement effectiveness coefficient varied from 3.0 to 7.0 with longitudinal reinforcement. The average deformability factors were 4.2 and 2.8 with spirals and ties, respectively. Lateral reinforcement had a more pronounced effect on deformability than on column strength.

/pdf/behavior-and-performance-of-gfrp-reinforced-concrete-columns-4mx4l68gx0.pdf

Behavior and Performance of GFRP Reinforced Concrete Columns with Various Types of Stirrups

Geopolymer concrete has progressively gained acceptance as one of the best alternative construction materials in civil and infrastructural engineering applications. The geopolymer binders have excellent mechanical properties and commercial potential, with lower environmental impact compared to ordinary Portland cement. In the past, most studies have focused on mixtures, properties, mixing and curing process, and micro-structure, etc., of the geopolymer binder. However, studies on structural member design using fly ash geopolymer concrete are still limited and do not have comprehensive coverage. Furthermore, some design parameters are rarely available, and this has slowed down the development of applications. The objective of this study was to evaluate and establish strength parameters of fly ash geopolymer concrete under flexural, shear and torsion loadings, utilizing prior experimental data and those from various standard design codes such as ACI, AS3600, CSA, and CIB-FIP. Models of modulus of rupture, elastic modulus, torsional strength, and flexural beam shear were developed in terms of compressive strength. In our experimental study, three different experimental sets were performed: 1) uniaxial compression and flexural beam test to evaluate modulus of rupture, 2) uniaxial compression and torsion test to determine cracking torsional strength, and 3) beam test (with shear span to effective depth ratio (a/d) ≈ 2) and uniaxial compression test to characterize shear strength. By using experimental data of the current and prior studies, the modulus of rupture model was developed in terms of an exponential function for the geopolymer concrete compressive strength, with acceptable accuracy. The modulus of elasticity in a power function was more accurate with 85% R2 for a board range of compressive strengths. The proposed cracking torsional strength model, based on thin-wall theory, was established with the critical stress 0.47√f'c. The proposed shear strength estimate having similar form as the original ACI equation is reasonably conservative and facilitates the practical use of geopolymer concrete in structural design.Finally, the interaction surface for combined loads, such as bending, shear and torsion was demonstrated for the quarter-parabola bending –shear and – torsion, and for the quarter - circle torsion and shear interactions, with the critical stresses: (fb = 0.815f′c), (fs = 0.11f′c) and (ft = 0.30f′c), respectively.

Woraphot Prachasaree

Papers

Development of Equivalent Stress Block Parameters for Fly-Ash-Based Geopolymer Concrete

Development and Performance Evaluation of Very High Early Strength Geopolymer for Rapid Road Repair

Performance evaluation and microstructure characterization of metakaolin-based geopolymer containing oil palm ash.

Behavior and Performance of GFRP Reinforced Concrete Columns with Various Types of Stirrups

Manuscript title: Development of strength prediction models for fly ash based geopolymer concrete