Determination of the Properties of Self-compacting Concrete Containing Metakaolin as a Replacement for Cement and Limestone Powder

Today, the tendency to use self-compacting concrete (SCC) is expanding due to its advantages. Manufacturing of SCC requires increasing the amount of cement used, which will result in the more environmental pollution due to the increased cement production, trying to use pozzolans to reduce cement consumption will be an essential step towards sustainable development. So, efforts to use pozzolans to reduce cement consumption will be an essential step towards sustainable development. Accordingly, in this study, by replacing a part of the cement and limestone powder with metakaolin as an active pozzolan, some properties of the produced concrete including rheology, mechanical and durability were evaluated. For this aim, metakaolin with 10%, 15%, 20%, 25% and 20%, 25%, 30%, 35% replaced the cement and limestone powder, respectively (without changing the cement content). The self-compacting properties of the concrete specimens were evaluated in the form of slump flow tests, L-box, U-box and J-ring, as well as mechanical properties including compressive and splitting tensile strength, and durability including water penetration depth and rapid chloride ion penetration (RCPT). The results present that the utility of metakaolin in the manufacturing of self-compacting concrete as an independent alternative to the part of cement and limestone powder has improved the mechanical properties of concrete, but has reduced its consistency. In order to solve this problem, it is necessary to increase the percentage of consumable superplasticizer used until it reaches the desired consistency level. Replacement of cement by 20% metakaolin reduced water permeability and RCPT by 35% and 20%, respectively, and replacing of the limestone powder by 35% metakaolin reduced water permeability and RCPT by 70% and 35%, respectively.