Hardened properties of pre-cracked concrete incorporating metakaolin and crushed blast furnace slag as an additional blend material

Abstract

• Mechanical and durability properties of pre-cracked modified concrete by metakaolin (MK) and granulated blast furnace slag (GBFS) are studied. • Pre-cracking concretes exposed to sulfuric acid reduces the compressive strength by 45% to 50%. • Increasing the degree of concrete cracking reduces the compressive strength and the durability of the concretes after acid exposure. • A positive effect of additives (MK and GBFS) on the durability of the concrete is noted. • Replacement of cement with additives at 10% is the better mix design for concrete. In this research paper, an experimental study was carried out to analyze the durability of pre-cracked modified concrete by metakaolin (MK) and ground granulated blast furnace slag (GBFS). The mechanical and durability properties of three different types of hardened concrete and conventional cement concrete were assessed in terms of compressive strength, mass loss, open porosity, water penetration, capillary water absorption, and drying shrinkage for two compressive damage levels subjected to sulfuric acid attack (concentration of 5%). After the immersion period, these proprieties were compared with those of the control mix, and the variation in different parameters was evaluated. The results show that incorporating MK and GBFS improves the compressive strength in the long term compared to control concrete. In addition, the exposition of pre-cracking concrete to sulfuric acid reduces by 45% to 50% of the compressive strength of the concrete for all formulations. These results are confirmed by the mass loss and the pre-cracking samples’ open porosity variation. The F10 formulation provided the lowest water penetration depth and capillary absorption coefficient compared to the control mix regardless of the degree of cracking and exposure to acid, which shows the positive effect of additives on the durability of the concrete. The replacement of cement with MK and GBFS at 10% is considered the better mix design for concrete of sewer structures. The shrinkage of this mix was the lowest compared to the other formulations.