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Subject: search.filters.subject.Compressive strength

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    Partially hydrated recycled aggregate concrete: A systematic approach towards sustainable development
    (Elsevier, 2018-10) Barai, Sudhir Kumar; Pradhan, Subhasis
    The experimental investigation on the mechanical properties of partially hydrated recycled aggregate concrete (PHRAC) with the addition of polypropylene fiber (PP fiber) is carried out and compared with the conventional concrete. The 28 days compressive strength is observed to be higher for PHRAC, whereas the tensile strength is lower than natural aggregate concrete (NAC). Based on the mechanical properties, the optimal dosage of PP fiber for both NAC and PHRAC is obtained as 0.6% by weight of cement. The bond strength is also evaluated by conducting the pullout tests using rebar of 12 mm, 16 mm and 20 mm diameter. Higher bond strength is experienced for PHRAC with respect to NAC, whereas the PP fiber addition does not have a significant effect on the bond strength of concrete. Further, -test reveals that, barring flexural tensile strength other mechanical parameters are not influenced either by the type of aggregate or by the incorporation of PP fiber. The cost analysis shows that, the preparation of PHRAC is 4.5% cheaper than NAC.
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    Use of alkali-silica reactive sedimentary rock powder as a resource to produce high strength geopolymer binder
    (Elsevier, 2017-11) Lahoti, Mukund
    This paper reports on an innovative way to utilize alkali-silica reactive (ASR) rocks as a natural resource to produce high strength geopolymer binder. Excavation of the Jurong rock caverns in Singapore has produced large quantities of sedimentary rocks. These rocks, however, cannot be used for ordinary Portland cement concrete production due to their ASR reactivity. An alternative way to beneficially utilize these rocks is to produce geopolymer binder. The excavated rocks were classified based on petrography into four types and then converted to powder form in a sequence of steps. The rock powders were used to synthesize geopolymers by replacing metakaolin in different replacement ratios. Results showed that geopolymer binder with 67 wt% rock powder and only 33 wt% metakaolin can achieve a high compressive strength of 80 MPa. Incorporation of sedimentary rock powder enhanced the compressive strengths by 15–30% as compared to pure metakaolin geopolymers. Microstructure analysis revealed that the enhancement in compressive strengths were primarily due to the densification of binder by filling the voids in matrix with rock powders.
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    A succinct review on the use of NMR spectroscopy in monitoring hydration, strength development, and inspection of concrete
    (Elsevier, 2022) Lahoti, Mukund
    NMR is a very useful technique used in analytical chemistry for quality and molecular structure determination of a compound as well as its chemical environment. It works on the principle of the energy gap between two nuclei of an atom for an applied external magnetic field, due to their opposite spins. The potential of the three sub-categories of NMR (H-NMR or proton NMR, liquid-state NMR, and solid-state NMR) for monitoring hydration reaction in cement paste, early-age strength development in fresh concrete, and the inspection of hardened concrete has been elucidated in this paper. Powerful features of NMR in identifying the chemical environment and structure have made it possible for this technique in the evaluation of concrete subjected to sulfate attack and the estimation of the effect of alumino-silicate precursor on the strength of geopolymer. In this manuscript, various other applications of NMR in the non-destructive testing, quality checks, and monitoring of reactions in concrete and cement have been reviewed.
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    An Experimental Investigation of Accelerated Carbonation on Properties of Concrete
    (ENGINEERING JOURNAL, 2016) Bhunia, Dipendu; Singh, Shamsher Bahadur
    This study deals with the effect of carbonation on the mechanical properties such as compressive strength, flexural strength and durability like depth of carbonation and volume of permeable voids of the concrete cast using ordinary Portland cement over a time period of up to 120 days. To study the behavior of carbonation front of concrete in presence of varying water content, water binder ratios of 0.35, 0.50 and 0.65 are chosen. It is observed that the volume of permeable voids of concrete has decreased, with an increase in compressive strength, flexural strength and depth of carbonation as the number of days of exposure of concrete specimen to high carbon dioxide increased.
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    Analytical and Experimental Investigations on Using Waste Marble Powder in Concrete
    (ASCE, 2019-04) Srivastava, Anshuman; Bhunia, Dipendu
    Research using marble powder as a partial replacement of cement in concrete has gained a lot of attention recently. In this paper,the effect of dried marble powder on particle packing of concrete has been demonstrated. Experimental investigations have been conducted onthe effect of marble powder on hydration reaction, strength activity index, and possible reasons for the gain in strength. In addition, statisticalmethods were used to develop two mathematical models for marble powder incorporated in concrete using experimental values. In the firstmodel, the ratios of 28-day compressive strength between concrete with cement partially replaced by marble powder and control concretehave been related to marble powder replacement percentage. In the second model proposed, modified and simplified relationships for thewater-cement law when cement is partially replaced by marble powder have been provided. The first model was validated for both standardcubes and cylinders used for testing by researchers and the predictions showed only 7.15% error as compared with the experimental values.The second model might serve as a useful tool for mix proportioning of concrete mixes incorporating marble powder in concrete. Finally,based on a review of the literature and experimental results, a set of guidelines has been proposed for the use of marble powder as a partialreplacement of cement in concrete
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    Role of water/cement ratio on strength development of cement mortar
    (Elsiever, 2015-12) Singh, Shamsher Bahadur
    The effect of water/cement (w/c) ratio on the mechanical properties such as compressive strength and split tensile strength of cement mortar cylinders and cubes was investigated experimentally for 28 days curing period as per IS standard. Based upon the experimental results, empirical equations have been developed to predict the strength of cement mortar mixes with various w/c ratios. It is observed that Abrams’ law is applicable for the cement mortar also. The cement mortar contains varying proportions of portland pozzolana cement (PPC) and river sand such as 1:3, 1:4, 1:5, 1:6, 1:7, 1:8 with different w/c ratios. An empirical equation has been developed between split tensile strength and compressive strength of cement mortar. Results show that compressive strength and split tensile strength of cement mortar decreased with an increase in the w/c ratio. It is observed that minimum w/c ratio required to make the cement mortar workable is 0.5.
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    An Experimental Investigation of Accelerated Carbonation on Properties of Concrete
    (Eng. Journal, 2016) Singh, Shamsher Bahadur; Bhunia, Dipendu
    This study deals with the effect of carbonation on the mechanical properties such as compressive strength, flexural strength and durability like depth of carbonation and volume of permeable voids of the concrete cast using ordinary Portland cement over a time period of up to 120 days. To study the behavior of carbonation front of concrete in presence of varying water content, water binder ratios of 0.35, 0.50 and 0.65 are chosen. It is observed that the volume of permeable voids of concrete has decreased, with an increase in compressive strength, flexural strength and depth of carbonation as the number of days of exposure of concrete specimen to high carbon dioxide increased.
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    Evaluation of use of bottom ash in cement masonry and concrete regarding their mechanical properties
    (IAAM-VBRI Press, 2018) Gupta, Rajiv
    Large quantities of ash are generated every year by the various manufacturing industries as a waste by-product. This study aims to utilize waste by-product in concrete and to reduce its cost by replacing cement in parts with bottom ash. This research presents the results of the experimental investigations to study the use of bottom ash as partial replacement for cement in concrete and masonry units. Bottom ash is the coarser material, which falls into furnace bottom and constitutes about 20% of total ash content. The strength development for various percentage replacements (5-15%) of cement with bottom ash has been compared to control specimens of concrete and masonry.
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    Group Method of Data Handling Algorithms to Predict Compressive Strength of Concrete Based on Absorbed Extraterrestrial Solar Radiations
    (Scientific Net, 2016-04) Gupta, Rajiv
    The present study applies group method of data handling (GMDH) to predict compressive strength of normal strength concrete based on experimentally determined weight, ultrasonic pulse velocity and extraterrestrial solar radiations absorbed by concrete specimen. GMDH are widely used as mathematical modelling and non-linear regression algorithms, and are assumed as specific type of supervised artificial neural networks. Concrete being a multi-phase porous and non-linear material justifies usage of such algorithm as GMDH employs the idea of natural selection to control size, complexity and accuracy of networks being used for various applications like function approximation, non-linear regression and pattern recognition. The effectiveness of algorithm is validated when 60%, 70%, 80% and 100% of normalized and non-normalized data is used for training. GMDH being an intelligent algorithm with ability of learning and adaptation can be conveniently used as an appropriate prediction tool for non-linear complex systems like concrete.
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    Compressive Strength Characteristics of Normal Strength Concrete Cured Using Colored Polythene Sheets
    (Scientific Net, 2013-04) Gupta, Rajiv
    Concrete performance is severely influenced when placed in extreme environmental conditions and hence certain measures are required to control it. The present paper proposes covering the structural members with colored polythene sheets which serves dual purpose of curing. Polythene sheets do not allow appreciable loss of water by evaporation and thus they do not delay or prevent hydration besides providing optimum temperature and humidity conditions for strength development and being water conservative. In present study concrete cubes were wrapped using five different colored polythene sheets for a period of 7-days. The study incorporates prevailing environmental conditions by relating effect of curing, including conventional methods like sprinkling and ponding on compressive strength of concrete at varied atmospheric temperatures, relative humidity and influence of available solar radiation. Significant compressive strength characteristics like initial tangent modulus and strain at peak stress are also determined for cubes at a period of 7-, 28-, and 180-days. The quality assessment of concrete cubes cast was carried out using ultrasonic pulse velocity test results. The study aims at developing a knowledge base to design an extensive decision making algorithm that identifies appropriate curing method in prevailing environmental conditions.