Production of sustainable concrete utilising high-volume blast furnace slag and recycled aggregate with lime activator

Abstract

Waste products from construction sector and industries have been significantly increased in the last decade, which create serious environmental problems. Therefore, their utilisation in concrete has great role in the production of sustainable concrete, preservation of natural resources and proper solid waste management. This study involves the fundamental characterisation of sustainable concrete produced using high volumes of recycled coarse aggregate (RCA) and ground granulated blast furnace slag (GGBFS) with addition of lime for its application in structural concrete members. In this investigation, at the first, the effects of lime as an alkaline activator on the mechanical and micro-structural properties of high volume GGBFS based recycled aggregate concrete (RAC) is studied in order to obtain the desired mechanical properties. From the study, the experimental results reveal that lime can be effective in activating the GGBFS and thereby, enhancing the mechanical properties such as (1) compressive strength, (2) splitting tensile strength, (3) flexural strength and (4) bond strength of high volume GGBFS based RAC. The enhancement in the above strength properties of GGBFS based RAC mixes are found to be in the range 14.02%–19.61%, 9.33%–14.07%, 10.74%–14.71% and 6.65%–14.17% for compressive, splitting tensile, flexural and bond strength, respectively. The trend of the above results is also supported by X-ray diffraction and scanning electron microscopy investigations. Secondly, the cost-effective analysis including the sensitivity analysis of cost for this concrete are carried out to ascertain its (5) economic benefit. The cost-effective analysis reveals that the cost of concrete reduces by 7.15%–11.80% for the combined use of RCA, GGBFS and lime. Thirdly, environmental impact analysis of this concrete is also performed to assess its (6) environmental benefit. It is found that the impacts on various environmental factors reduce by 32.5%–67.0% for using RCA, GGBFS and lime in concrete. Hence, it is concluded that the concrete produced using high volume of GGBFS and RCA with addition of lime activator provides the desired strength, environmental benefit by reducing the environmental impacts and minimising the waste disposal problem, economical benefit by reducing the cost and social benefit by preserving natural resources for future generation due to which this concrete becomes sustainable.