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    Use of concrete wastes as the partial replacement of natural fine aggregates in the production of concrete
    (Springer, 2019) Saha, S.; C, C.; Vinay, K.
    Due to rapid development of construction industries in various dimensions, demand for construction materials is also gaining high momentum. Therefore, availability of natural sources of construction materials is going to be in decreasing trend to cope up with the high demand. Again currently, quantity of construction and demolition waste is also going too high day by day. Reuse of these construction and demolition waste is one of the promising solutions to protect natural fine aggregates. This study aims at investigations the possibility of the usage of these construction and demolition wastes to produce the fresh concrete with desirable properties. Natural fine aggregates (river sand) are replaced by the recycled fine aggregates by the different percentage levels for the production of fresh concrete. A comparative interpretation on the strength characteristics of the concrete produced with Ordinary Portland Cement and Portland Pozzolana Cement is also presented and discussed in this paper. © Springer Nature Singapore Pte Ltd. 2019.
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    Investigation on the potential use of recycled fine aggregate to produce geopolymer mortar mix
    (ASTM International, 2019) Saha, S.; C, C.
    The utilization of construction and demolition waste (C&DW) partially or fully for various purposes in construction industries is one of the most significant solutions to overcome the scarcity of raw materials and disturbances of the environmental system. On the other hand, geopolymer is being tried to be established as an alternative sustainable binder material for ordinary portland cement. In the present study, with the thought of promoting of sustainability, an attempt has been made to use concrete wastes as recycled fine aggregate (RFA) partially to produce fly ash (FA)-based geopolymer mortar. The workability, water absorption, compressive strength at 3, 7, 28, and 56 days, volume change behavior, and chloride permeability of the produced FA-based geopolymer mortar were determined. The effects of RFA, the ratio of alkali liquid (AL) to FA, and different curing regimes on these properties of mortar mix also discussed. The morphology and microstructures of the samples taken from the mortar mix, which were observed having the highest strength under different curing regimes, were studied using scanning electron microscopy (SEM). The experimental results indicate lower workability, higher water absorption capacity, and higher drying shrinkage of geopolymer mortar mix that has more RFA content in the mix, but the compressive strength of the geopolymer mortar mix started decreasing after a certain percentage of RFA content in the mix. Utilization of that certain percentage of RFA will help us to minimize the consumption of natural fine aggregates and reduce the disturbances generated by unorganized dumping of C&DW. © 2019 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.
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    Volume change characteristics of eco-friendly mortar mixes produced with geopolymeric binder and recycled fine aggregate
    (ASTM International, 2020) Saha, S.; Shaik, N.; C, C.
    The production of geopolymer mortar using recycled fine aggregate (RFA) generated from concrete waste has significant potential to be a sustainable construction material. In this article, the volume change properties of the produced geopolymer mortar mixes are studied in terms of drying shrinkage up to the age of 180 days and reported as the percentage increase with respect to the shrinkage value of 3 days. The influence of RFA content, alkaline liquid (AL) in terms of the concentration of sodium hydroxide (SH) solution, the ratio of sodium silicate (SS) solution to SH solution, and the ratio of AL to fly ash (FA) were investigated on the drying shrinkage properties of the geopolymer mortar mixes. All the cast specimens were cured at 80°C for 24 hours. Higher drying shrinkage values were observed for the mortar mixes produced with higher RFA content, AL/FA, SS/SH ratio, and lower concentration of SH solution. Scanning electron microscope images were studied for the samples taken from the geopolymer mixes showing lower drying shrinkage values to understand the microstructure. © 2019 by ASTM International.
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    Strength and shrinkage properties of heat-cured fly ash-based geopolymer mortars containing fine recycled concrete aggregate
    (ASTM International, 2020) Saha, S.; C, C.
    Geopolymer has obtained significant importance as an alternative eco-friendly binder material for ordinary portland cement (OPC) as it can be produced from the reaction between the industrial by-product materials rich in alumina, silica, and alkaline solutions. Therefore, usage of geopolymer effectively in the construction industry will help to reduce the consumption of a huge quantity of natural resources for the energy processes required for the production of OPC. It is also one of important solution to control carbon dioxides emission by the usage of OPC. On the other hand, using construction and demolition waste (C&DW) as the source of recycled aggregates in construction industry helps to reduce the huge consumption of natural aggregates and protect the environment from the disturbances caused by the unorganized dumping of C&DW. In this study, an attempt has been madeto produce fly ash (FA)-based geopolymer mortar mixes using C&DW effectively as fine aggregates partially. The effects of recycled fine aggregates (RFA), the ratio of alkaline liquid (AL) to FA, and duration of heat curing on the properties of the produced geo-polymer mortar mixes have been discussed in this article. To determine the influence of RFA on the strength and volume change behavior of mixes, natural fine aggregates were replaced by RFA at 0, 10, 20, 30, 40, and 50 % by mass. The AL/FA ratio was adopted as 0.4 and 0.6. Higher compressive strength was observed for most of the mortar mixes having RFA up to 20 %, and higher drying shrinkage value was found for the mixes with higher RFA content. Scanning electron microscopy (SEM) images were also studied for knowledge about the signature of the formed structures in the mortar mixes, which were observed having higher strength. © © 2019 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.
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    EXPERIMENTAL INVESTIGATIONS ON THE PROPERTIES OF CONCRETE CONTAINING PRE-SOAKED RECYCLED FINE AGGREGATE
    (Associated Cement Companies Ltd., 2022) Saha, S.; C, C.; Ganiger, M.S.; Sajjan, S.
    Recycled fine aggregate (RFA) becomes very significant and promising alternative materials for natural fine aggregate (river sand) to be used in the production of concrete. But, most of the past research works indicated higher water absorption capacity of RFA as one of the key factor to affect the properties of fresh concrete. Therefore, an experimental attempt has been made to address the issues related to water absorption capacity of RFA by soaking it in water for 24 hours prior to use as alternative fine aggregate for the production of the fresh concrete. Mechanical properties of concrete such as compressive strength, splitting tensile strength, and flexural strength, and durability properties such as resistance against acidic and alkaline environment, chloride permeability test for ordinary Portland cement (OPC) and Portland pozzolana cement (PPC) based concrete mixes made with soaked recycled fine aggregates (SRFA) are determined, and analysed. For OPC, and PPC based concrete, respectively 4.32, and 20.75 % in compressive strength at 28 days; 2.69, and 27.24 % increase in flexural strength; 6.38, and 40 % increase in splitting tensile strength at 28 days were observed for the concrete mixes with SRFA compared to the mixes with RFA. Experimental results indicated notable improvement of the mechanical, and durability properties of concrete mixes when recycled fine aggregates were soaked in water prior to use. © 2022, Associated Cement Companies Ltd.. All rights reserved.
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    Influence of the mix parameters on shrinkage properties of environment-friendly mortar
    (Taylor and Francis Ltd., 2024) Saha, S.; C, C.
    Cracks in concrete structures are generally initiated due to the shrinkage i.e. the volume change characteristics of the concrete structures. In this experimental study, effects of the mix parameters related to alkaline liquid (AL) and recycled fine aggregate (RFA) on the shrinkage behaviour of environment-friendly mortar mixes produced with fly ash (FA)-based geopolymer binder and RFA were investigated and reported. To find out the effects of AL, concentration of liquid sodium hydroxide (LSH) was varied from 6M to 16M, ratio of liquid sodium silicate (LSS) to LSH in AL was varied from 1.0 to 2.5 and AL/FA ratio was considered as 0.4 and 0.6. Different fly ash-based geopolymer mortar mix were produced depending on above-said combinations of mix parameters along with the RFA content (by weight) of 10%, 20%, 30%, 40% and 50% in lieu of natural fine aggregate. Prismatic specimens (25 mm × 25 mm × 285 mm) were cast and cured at ambient air temperature to determine the shrinkage behaviour. Higher RFA content in mix, higher LSS/LSH ratio in AL and higher AL/FA ratio resulted in higher shrinkage value. But, lesser shrinkage value was noticed for those specimens of mortar mix with the consideration of higher concentration of LSH in AL with varying RFA content. ©, Engineers Australia.