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Sustainable development goal 6: clean water and sanitation—could be a big challenge for water-stressed India. Use of non-potable water for concrete production can contribute largely towards this goal. Scattered experimental studies on concrete mixed with non-potable water having different pH, were collated to prepare a pan-Indian database. Using this data, probability of code compliance of Indian concrete for varying ranges of pH value of mixing water, within the limits permitted by the Indian code (6–8.5), were estimated for the first time in India. A bootstrap-based re-sampling approach was employed for this purpose. The results indicated that fulfilling the 28-day strength requirements would possibly concurrently fulfill similar stipulations for 7-day strength for Indian concrete mixed with non-potable water of varying pH. However, the probabilities of meeting the Indian code requirements were between 54%-66% for pH ranges starting from 6; and between 66%-85% for others (95% confidence). Considering the entire range of pH (6–8.5), this probability was 66% for 28-day and 72% for 7-day (95% confidence). Probabilistic approach for examining the strength/setting time compliance, along with inclusion of 7-day strength as well as durability aspects in future experiments would help to promote use of non-potable sources of water and reduce use of freshwater for mixing concrete in India. [ABSTRACT FROM AUTHOR]

Construction is a process of developing new ventures and is a never-ending activity. The aggregates are the raw materials, which constitute 70-80% in the concrete mixture. Every year, it is estimated that the construction industry in India generates about 10-12 million tonnes of waste annually. Concrete is the most versatile material which is used extensively in the construction field. There is a need to think of alternate materials because of the scarcity of natural aggregates. The use of this recycled coarse aggregate is mainly for two reasons: To decrease CO2 emission which is harmful to environment and to reduce the cost of construction material / cost cutting/reduce the budget of the construction. C&D waste can be reduced, re-used and recovered, dramatically reducing the dumping of demolished waste. The main purpose of recycling is to minimize the amount of waste to be deposited and to preserve natural resources. The present investigation is carried out for evaluation of properties of natural and recycled aggregate concrete. Pozzolanic materials like Fly Ash and Silica Fume are used as mineral admixtures for good workability and for better strength. Cement is replaced with 10% SF and 20% FA in design mix. RAC20 made with different grades of recycled aggregates of GA20, GA25, GA30, GA35 and GA40 with different replacements 50%, 75% and 100%. During mix proportion presoaking of aggregates is done before the mixing of concrete. Three stage mixing approach is adopted for the production of concrete. The density of concrete, compressive strength and water absorption of PC & RAC were determined at ages of 7 and 28 days. The results of compressive strength are found to be lower than target strength. With GA20 at 50% replacement, 95% of the target strength is achieved (27.55MPa). Strength could have achieved with increase in curing period. It is also concluded that the water absorption and density of RAC is lower than NAC. [ABSTRACT FROM AUTHOR]

Marble stone is the mostly quarried stone in Rajasthan for its high demand in India and abroad. This quarrying resulted in the generation of waste in a slurry form which was dumped in the nearby landfill sites resulted in a detrimental effect on the soil strata and expanding the landfill area with time. The focus of the study is to explore the outcome of utilization of marble slurry as a partial substitution of ordinary Portland cement by 10%, 20%, 30%, and 40% for lean concrete mixes with an average target compressive strength of 20 MPa or more. To explore the prospect of deployment of marble slurry in cement concrete mechanical properties, durability aspects, and relevant microstructural analysis was performed, and the results have been reported. Though the durability aspect was not purely encouraging, though it was depicted that marble slurry can be utilized as a partial replacement of OPC up to 40% for the purpose for which the investigation has been done. Highlights: Marble slurry utilized as a substitution of OPC by 10%, 20%, 30%, 40%.TGA results indicate that marble slurry did not affect the hydration of OPC.Resistance against carbonation decreases with the increment of marble slurry content.UPV results indicates after 40% substitution concrete was in the good quality zone. [ABSTRACT FROM AUTHOR]

The extraction of marble and its processing as marble blocks is most common in several states of India. But the extensive growth of this industry has put adverse impact on the environment because of the production of huge amount of marble waste during extraction and processing. This experimental study highlights the impact of use of marble waste on the properties of lean concrete mix designed for the production of bricks. The basic objective of this experimental programme is to replace river sand in concrete by an optimum combination of quarry dust and marble waste in order to extract best performance in terms of strength and durability parameters. By varying the percentage replacement of fine aggregate with marble waste (0–100%), six concrete mix proportions were prepared for experimental purpose. The result shows that all these properties improved for complete substitution of fine aggregate with marble waste. It was found that compressive strength and flexural strength increased by 84% and 18.6%, respectively. The mixes were less reactive to the aggressive agents also. These advantages were derived due to the ability of marble fines impart necessary cohesiveness even at lesser water content which resulted in an impermeable microstructure. [ABSTRACT FROM AUTHOR]

Use of aggregates from recycled construction and demolition wastes in concretes alleviates the disposal problem and reduces the cost of concrete significantly. However, excessive water absorption, weak interfacial transition zone, and high porosity are its shortcomings. This study explores a bacterial cement and conventional cement slurry coating treatment on recycled coarse aggregates (RCA) for overcoming these shortcomings. In the first method, microbial carbonate precipitation (MCP) through bio-mineralization treatment has been utilized. Four different concretes were made using both control and treated aggregates. Once the performance of these concrete mixes was found adequate, a life cycle assessment was conducted using ISO14040–44 guideline to determine their environmental impacts. The experimental results confirmed that concrete with MCP treated aggregate offered better material performance than the untreated recycled aggregate based concrete mixes and possessed similar properties as natural aggregate concrete. While MCP process avoided the use of energy intensive cement, this research discovers that concrete with MCP treated aggregates was found to produce marginally higher environmental impacts than other concrete mixes mainly due to additional emissions associated with the bio-cement treatment of RCA. Further environmental mitigation strategies for concrete with MCP treated aggregates has considered to improve its environmental performance in terms of global warming impact and cumulative energy demand. This study demonstrates that the use of 100% RCA delivers significant environmental benefits in terms of ecological footprints, land conservation and biodiversity in a densely populated region like India. Global warming impact (GWI) and Cumulative Energy Demand (CED) of Natural Aggregate Concrete (NAC), Recycled Aggregate Concrete (RAC), Concrete with Cement Slurry Coated Recycled Aggregate Concrete (CCRAC) and Concrete with Bio-Cement Treated Recycled Aggregate (BTRAC) Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Mechanical strength and pore properties are checked with over burnt brick aggregate. • Nonlinear relation is obtained among permeability, porosity and compressive strength. • For single sized aggregates, permeability lie in the range of 1.2–2.1 cm/s. • Prediction equations are made for porosity, permeability and compressive strength. In the search of alternate construction materials, over burnt brick aggregate has enrolled its appellation as a low cost sustainable alternate material. In the north-eastern part of India, especially in Tripura, the shortage of natural stone aggregate has opened up the field for over burnt brick aggregate to be used as an alternate pavement material. This study mainly focuses on the characterization of pervious concrete mixes produced with over burnt brick as coarse aggregate. Pervious concrete, in the recent era, has been considered as the emergent technology due to its prominence as an environmentally and hydrologically sustainable pavement system. In this paper, a series of test samples are produced using various design variables and then the mechanical strength and the pore properties of porous mixes are evaluated. Aggregate gradation, water-cement ratio and the percentage of fine aggregate are chosen as the design variables and their effect in the compressive strength, tensile strength, flexural strength, porosity, permeability, etc. are estimated. The statistical analysis is also carried out using the experimental test data and prediction equations are developed to estimate the porosity, permeability and the compressive strength of the pervious concrete mixes. The predicted equations fitted well and showed a very good agreement with the calculated results. These equations can be directly used for the selection of the mix proportion and the designing of pervious concrete mixes made with over burnt brick aggregate. [ABSTRACT FROM AUTHOR]