Effect of Metakaolin Activation and Alccofine on the Mechanical Strength of Concrete at Elevated Temperature

Abstract

This research examines the possibility of chemically activating MK (Metakaolin) to increase the MK ratio with strength improvement at both standard and elevated temperatures. Besides, cement was replaced by AF (Alccofine) with a ratio of up to 15 % to improve concrete workability and strength. MK was tested with ratios ranging from 0% to 30%, with a 5% increase. MK was activated chemically using two activators: 2.5% Na2SO4 and 4% Aquis Na2SiO3. AF was investigated at 5%, 10%, and 15% ratios. 0.7% glass fibres (GF) were added to improve concrete ductility. According to the results of the tests, MK. up to a ratio of 15% without an activator improved concrete strength. After 28 days, the increase in strength was more pronounced. After the 15% ratio, the concrete strength improvement was rapidly declined. The Aquis Na2SiO3 activator increased the strength of the concrete while diminishing its workability. AF improved workability and concrete strength when subjected to normal and after being exposed to elevated temperatures. Using GF at a weight ratio of 0.7% on activated 30% MK with Aquis Na2SiO3 and 10% AF improved splitting and flexural strength at normal and increased temperatures Furthermore, GF avoided the spalling of concrete samples induced by the application of AF. Correlations between different mechanical parameters of concrete using multiple regression analysis. A good agreement between the predicted equations' outputs and the experimental results for compressive, splitting, and flexural strengths. Further, a cost analysis was conducted for the suggested mix by comparing it with a high-strength concrete mix of the same grade, and workability.