Bond, durability and microstructural characteristics of ground granulated blast furnace slag based recycled aggregate concrete

Abstract

Abstract The current paper aims to explore the effects of high volume ground granulated blast furnace slag (GGBFS) as the replacement of ordinary Portland cement (OPC) on the bond, durability properties of recycled aggregate concrete (RAC). In order to fulfil the above objective, seven concrete mixes are prepared; out of which one mix is regarded as the control mix. Other six concrete mixes contain 0%, 40% and 60% GGBFS with each of 50% and 100% recycled coarse aggregate (RCA). Since, the compressive strength is the key property of any concrete, the short- and long-term compressive strength behaviours of these mixes are first evaluated. The bond strength of these mixes is also investigated in order to study the effect of GGBFS on the bond behaviour of RAC. Further, the durability characteristics of these mixes are evaluated by exposing the concrete to various chemical attacks such as magnesium sulphate attack, sulphuric acid attack and sodium chloride attack. Moreover, the rate of water absorption by capillary action of the above concrete mixes is evaluated by performing the sorptivity test. In addition, the ultrasonic pulse velocity test is also performed to check the quality of concrete. In order to confirm the above strength and durability properties, the microstructural characteristics are also investigated by conducting the scanning electron microscopy (SEM) and X-ray diffraction (XRD) study. From the compressive and bond strength results, it is found that though these strength values decrease with the increase in GGBFS content, the high volume GGBFS can be utilized in the production of sustainable concrete. The durability results led to the conclusion that resistance to sulphate, acid and chloride attacks improve with increase in the content of GGBFS. Similarly, sorptivity of RAC reduces with increase in the content of GGBFS. The microstructural characteristics obtained in the present investigation justify the above strength and durability behaviour of these mixes.