LOCAL FORMULATION OF HIGH PERFORMANCE CONCRETE USING CALCINED KAOLIN: CASE OF CHAD

The main aim of the work carried out in this article is to investigate the local formulation and characterization of metakaolin and superplasticizer-based high-performance concretes (HPCs) in Chad. Five types of concrete were formulated, including one control and four others containing metakaolin as a cement substitute in proportions of 5, 10, 15 and 20%. Four concrete properties were evaluated: fresh concrete (density and slump test) and hardened concrete (density and compressive strength at 3, 7, 14 and 28 days), in order to assess the influence of metakaolin in the different compositions. The results obtained show that: (1) the concretes tested have almost identical workability, with a standard deviation of 0.62 (2) in the fresh state, the control concrete has a higher density, justifying the lower mass of the metakaolin, whereas in the hardened state, the density of the high-performance concrete with 20% metakaolin is higher (3) the high-performance concretes show greater kinetics in the evolution of compressive strengths. Simple compressive strengths are observed on HPCs with a maximum of 70.2 MPa on 15% metakaolin concrete, compared with a minimum value of 51.4 MPa on control concrete. Overall, the present work has highlighted the pozzolanic activity between metakaolin and lime released during cement hydration to produce hydrated calcium silicates, and the deflocculating activity of cement grains by the superplasticizer, with the joint aim of improving concrete mechanical strengths and durability.