Sulfate resistance of cement mortar containing metakaolin

Abstract

Many of an extensive researches have been carried out by Libyan Industrial Research Center in natural row materials in south region of Libya [1] and the results found that there are many of material can be used as building material, one of these materials which widespread over large area is Kaolin clay. From that point of view civil Eng. Dep. at Sebha university-Libya start thinking of using Kaolin clay as a building material and a team work has been formed to carry out a deep research study work on possibility of using the local natural pozzolana in south of Libya as a partially replacement of Portland cement. Previous laboratory study [2] which carried out by the team work proved that there is a possibility to use south Libya natural Kaolin clay as partial replacement of OPC after calcination and milling to get active calcined clay (Metakaolin). Metakaolin being used very commonly as pozzolanic material or as supplementary cementing materials in mortar and concrete, and has exhibited considerable influence in enhancing the mechanical and durability properties of mortar and concrete as well as utilization of natural calcined clay has widely spread attention in the world to minimize the Portland cement consumption and manufacturing of which being environmentally damaging, in addition to its economic advantage. Metakaolin when mixed with cement the silica of the pozzolana combines with the free lime released during the hydration forms additional cementitious C-S-H gel. This paper investigates the effect of metakaolin (MK) cement replacement on the resistance of mortar to sulfate attack for two different metakaolin quarries. Four MK replacement levels were considered in the study: 0%, 10%, 15%, and 20% by weight of cement for two quarries. After the specified initial moist curing period, mortar specimens were immersed in 5% sodium sulfate solution for a total period of one year. The degree of sulfate attack was evaluated by measuring expansion of mortar prisms, compressive strength reduction and observation of appearance of deterioration that usually accompanying with sulfate attack. All metakaolins examined in this study led to increases in strength and resistance to sulfate attack in comparing with controls samples or according to standard limits.