Assessment of the effect of different sand grading on strength properties of metakaolin blended cement mortar

Abstract

Abstract. Aggregate size has effects on the properties of cement composite. However, determination of sand grading is not usually put in to consideration in producing cement mortars for different application. Effects of different sand grading on the strength properties of metakaolin blended cement mortar have also not been well evaluated. In this study, effect of sand grading on the mechanical properties of metakaolin blended cement mortar, towards ensuring the development of durable and sustainable cement composite was investigated. Kaolin was sourced from Oyo State, South-West Nigeria. It was calcinated at 700oC to form metakaolin (MK) and characterized using X-Ray Fluorescence to determine its oxide composition. A blended cement produced with 15 to 25% replacement of Portland Limestone Cement (PLC) with the MK was used to produce mortar with different sand grading of fine, medium and coarse. Workability tests were carried out on freshly prepared mortar specimen with the three different sand grading. Water absorption, compressive strength and flexural strength tests on the different mortar specimen were carried out at 7, 14, 21, and 28 days, respectively. The addition of SiO2, Al2O3 and Fe2O3 of MK was found to be 79.23%. The grading variation are; Fine Sand (0.053 mm to 0.212 mm), Medium Sand (0.212 mm to 0.600 mm) and Coarse Sand (0.600 mm and 2.00). Workability of the mortar decreases with increasing particle sizes of sand and percentage replacement of PLC with MK. Fine sand absorbed more water with the highest at 25% MK replacement. Mortars specimen produced with Medium sand gave the highest compressive strength (15.11, 14.89 and 15.56 N/mm2) and flexural strength (5.616, 6.181 and 5.828 N/mm2) respectively for each of the 15, 20 and 25% replacement with MK. This study recommends the application of mortar containing medium sized sand with 20% MK for construction purposes.