A preliminary study on the effect of fine aggregate replacement with metakaolin on strength and abrasion resistance of concrete

• Concrete strengths increased with increasing in sand replacement with MK up to 40%.
• Abrasion resistance increased with increasing in sand replacement with MK up to 40%.
• Good linear regressions were found between wear depth and compressive strength.
• Hardened concrete density decreased with increasing in MK content as sand replacement.
• Suitable MK content could be efficiency used as partial sand replacement in concrete.

The purpose of this experimental study is to conduct a feasibility of using metakaolin (MK) as fine aggregate replacement in concrete. Sand was partially replaced with MK at levels of 10%, 20%, 30%, 40% and 50%, by weight. A reference mixture was designed to have characteristic compressive strength of 30 MPa. Specimens were subjected to abrasion testing in accordance with Egyptian Standard specifications (ES: 269-2/2003). Tests on compressive strength, splitting tensile strength, unit weight density and abrasion were performed up to 500 days. The various decomposition phases formed were identified using X-ray diffraction (XRD). The morphology of the formed hydrates was studied using scanning electron microscopy (SEM). Test results indicated that compressive strength, splitting tensile strength and abrasion resistance of concrete mixtures increased with increasing content of fine aggregate replacement with MK up to 40% then decreased at 50% replacement level. Abrasion resistances of concrete improved by about 23.12%, 36.18% and 46.24% over reference mixture with 40% replacement level at ages of 28, 91 and 500 days, respectively.