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Item Partially hydrated recycled aggregate concrete: A systematic approach towards sustainable development(Elsevier, 2018-10) Barai, Sudhir Kumar; Pradhan, SubhasisThe 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.Item Properties of Recycled Aggregate Concrete(Springer, 2018-06-17) Barai, Sudhir KumarThe important properties of fresh and hardened recycled aggregate concrete such as workability, compressive strength, split tensile strength, flexural strength, modulus of elasticity, density and ultrasonic pulse velocity (UPV) are discussed in detail in this chapter. The influence of the factors like w/c ratio of mix, engineering and physical properties of recycled aggregate (RA) to be used in concrete, the microstructure, strength of parent concrete, moisture state of RA, method of curing, proportioning of RA reported by different researchers with illustrations is described. A database was created with various important properties of RAC from a wide range of experimental results available globally during the period 1990–2015. Relationships between important properties of concrete viz. compressive strength and static modulus of elasticity, flexural strength, split tensile strength, density and ultrasonic pulse velocity (UPV) were investigated and using static regression analysis, modified equations were suggested for better description of the interrelationships among different important properties of RAC.Item Influence of Particle Packing Method on Sustainable Concrete Using Fly Ash and Recycled Aggregates(Springer, 2018-08-02) Barai, Sudhir KumarThe construction industry, using concrete most widely, is not sustainable as (i) it consumes large quantities of natural resources (for aggregates), (ii) The principal binder in concrete is cement whose production is a major contributor to greenhouse gas emissions (iii) Performance of concrete structures relies on rapid strength gain rather than durability and long-term effects. So, use of fly ash and recycled aggregates (RA) in concrete production may become a sustainable construction material with less environmental and economic impact if the performance of concrete structures is satisfied. Effect of RA and fly ash on compressive strength (CS) of concrete is addressed in present context by adopting particle packing method of mix design and modifying mixing techniques. Theoretical and experimental packing density is obtained and compared. A comparison of PPM and Indian standard (IS) code method of mix design is being done for the observed CS. Results concluded that PPM is suitable in terms of compressive strength for RAC with fly ash.Item Recycled aggregate concrete: a sustainable built Environment(ICSBE, 2010) Barai, Sudhir KumarIn the present study the influence of recycled coarse aggregate (RCA) obtained from three different sources having different ages of structures are on the properties of recycled aggregate concrete (RAC) are investigated. RAC mixes are prepared with each source of RCA separately. In order to assess the performance of RAC in comparison with normal concrete, two normal concrete mixes prepared with 100% natural coarse aggregate. Locally available natural sand is used in all mixes. The compressive strength and the characteristics of interfacial transition zone (ITZ) viz. porosity and microhardness of RAC are studied. The results reveal that the ITZ of RAC is relatively loose and porous than the ITZ in normal concrete.Item Statistical techniques to analyze properties of nano-engineered concrete using Recycled Coarse Aggregates(Elsiever, 2014-11-15) Barai, Sudhir KumarThis paper aims at evaluating effect of incorporation of Nano-Silica as replacement of cement on natural and recycled aggregate concrete using Two-way Analysis of Variance (ANOVA). In this study 3, 7 and 28 d compressive strength, Modulus of Elasticity, Water Absorption, Density, and Volume of voids are considered as responses. Principles of general factorial design is adopted for selection of number of mixes with consideration of Nano-Silica (%) and Recycled Coarse Aggregate (%) as two factors for this study. The ANOVA of test results depicts that these two factors have significant effect on compressive strength, Water Absorption, Density, and Volume of voids. However, the analysis of results indicates that only Recycled Coarse Aggregate (%) has considerable influence on Modulus of Elasticity. Moreover, there are no substantial influences of interaction of two factors on the selected properties of concrete.Item Partially hydrated recycled aggregate concrete: A systematic approach towards sustainable development(Elsiever, 2018-10-20) Barai, Sudhir KumarThe 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.Item Development of construction materials using nano-silica and aggregates recycled from construction and demolition waste(Sage, 2015-05-18) Barai, Sudhir KumarThe present work addresses the development of novel construction materials utilising commercial grade nano-silica and recycled aggregates retrieved from construction and demolition waste. For this, experimental work has been carried out to examine the influence of nano-silica and recycled aggregates on compressive strength, modulus of elasticity, water absorption, density and volume of voids of concrete. Fully natural and recycled aggregate concrete mixes are designed by replacing cement with three levels (0.75%, 1.5% and 3%) of nano-silica. The results of the present investigation depict that improvement in early days compressive strength is achieved with the incorporation of nano-silica in addition to the restoration of reduction in compressive strength of recycled aggregate concrete mixes caused owing to the replacement of natural aggregates by recycled aggregates. Moreover, the increase in water absorption and volume of voids with a reduction of bulk density was detected with the incorporation of recycled aggregates in place of natural aggregates. However, enhancement in density and reduction in water absorption and volume of voids of recycled aggregate concrete resulted from the addition of nano-silica. In addition, the results of the study reveal that nano-silica has no significant effect on elastic modulus of concrete.Item Compressive Strength of Nano-Silica Incorporated Recycled Aggregate Concrete(ISJR, 2014) Barai, Sudhir KumarThe present work is based on analysis of the influence of incorporation of Nano-Silica on compressive strength of recycled aggregate concrete using two factorial designs. In this study, recycled coarse aggregate (%), Nano-silica (%) and Specimen Type are selected as factors and each having two levels. Four numbers of mixes with three replicates are designed and compressive strength at seven and 28 days are selected as responses. Analyses of Variance (ANOVA) of experimental results are carried out to study the influence of factors and various plots are used to demonstrate the results of the analysis. The outcome of the study depicts that the selected factors are significantly affecting the compressive strength of concrete. However, the analysis indicates that interaction of factors has no substantial influence on compressive strength of concrete.Item Influence of incorporation of nano-silica and recycled aggregates on compressive strength and microstructure of concrete(Elsiever, 2014-11-30) Barai, Sudhir KumarThe present investigation deals with the study of compressive strength and characteristics of the Interfacial Transition Zone (ITZ) of concrete containing recycled aggregates and nano-silica. For this purpose, compressive strength at 7, 28, 90 and 365 days are determined for fully natural and recycled aggregate concrete mixes made with or without nano-silica. In addition to above, Vickers microhardness test and backscattered-mode scanning electron microscopic analysis is carried to characterize ITZ of concrete mixes. The results of study depict that full replacement of natural coarse aggregates with recycled ones have significant effect on compressive strength and ITZ characteristics of concrete. However, compressive strength and microstructure of concrete mixes improves with the incorporation of nano-silica.Item Behaviour of recycled aggregate concrete under drop weight impact load(Elsiever, 2011-01) Barai, Sudhir KumarThis paper presents the experimental results of recycled aggregate concrete (RAC) beams prepared with different amount of recycled coarse aggregate (RCA) subjected to low velocity impact. The recycled coarse aggregates are obtained from a demolished RCC culvert. Four concrete mixes with 0%, 25%, 50% and 100% RCA respectively are prepared. With each mix three beam specimens of size 1.15 × 0.1 × 0.15 m are prepared and tested under drop weight impact load. The behavior of the RAC beams are studied in terms of acceleration, strains and support reaction histories under impact load in addition to the physical and mechanical characteristics of RCA and RAC. It is observed that 25% RCA does not influence the strength of concrete. In addition, it is found that for a given impact energy (the energy imparted by the hammer per blow) the reactions and strains of RAC with 50% and 100% RCA are significantly lower and higher respectively than those of normal concrete and RAC with 25% RCA.