A study on the role of metakaolin and alccofine as supplementary materials on strength properties of concrete

Abstract

In recent years, the utilization of supplementary materials has played an important role in development of high strength concrete, improving the overall properties of concrete and rendering sustainability to concrete construction. Though different supplementary materials such as fly ash, silica fume, metakaolin and ground granulated blast furnace slag have been utilized for development of concrete, there is a need to understand the comparative role of these supplementary materials on workability, early strength gain, stress–strain response under compression and flexure, etc. In this context, the present study evaluates the comparative performance of metakaolin and alccofine (ultrafine slag) as supplementary materials in concrete; wherein, 30% replacement of cement with supplementary cementitious has been done (20% replacement with fly ash (class C) and 10% replacement with metakaolin, MK / alccofine, AL). The comparative assessment of the compressive strength, stress–strain behaviour and flexural response of MK- and AL- blended concrete has been carried out, and the results suggests that AL blended concrete exhibits higher early age strength (7 days curing), as compared to MK blended concrete. Similar trend in strength development is witnessed for 28 days and 56 days cured specimen; wherein, the average 56 days compressive strength of AL blended concrete observed to be 86.11 MPa, is substantially higher than 61.45 MPa strength observed for MK blended concrete (load control tests). Further, the flexural strength of AL blended concrete is noted to be higher than MK blended concrete. Moreover, the pre-peak and post-peak energy absorption capacity, evaluated from stress-strain (displacement control compression tests) and load–displacement response (flexural tests) of AL blended concrete, is higher than MK blended concrete, indicating its higher ductility under loading. Overall, the study findings suggest the beneficial contribution of supplementary materials in developing sustainable concrete with superior properties, and demonstrates the potential of AL as supplementary material in concrete.