Publication Details
Abstract
This experimental study examines the crucial role of the pozzolanic reaction of High-Reactivity Metakaolin (HRM) when used as a highly active partial replacement to enhance the mechanical and structural properties of conventional concrete. The experimental program was established by designing a control mix with a cement content of 400 kg/m³ and a constant water-to-cement (w/c) ratio of 0.5 to ensure optimal workability. The research methodology adopted a weight-based cement replacement strategy, incorporating 15% metakaolin to evaluate its efficiency in micro-void filling and stimulating secondary reactions. Laboratory results following a 28-day water curing cycle revealed a qualitative leap in structural performance: compressive strength increased substantially from an average of 33.4 MPa for the control specimens to 38.2 MPa for the metakaolin-modified specimens, with peak values reaching 39.57 MPa. This mechanical strength enhancement, approximately 14.3%, is attributed to the synergistic "filler effect" and the vigorous chemical reaction between the silica in metakaolin and the free calcium hydroxide Ca(OH)_2 liberated during cement hydration. This reaction facilitates the transformation of weak hydration products into dense Calcium Silicate Hydrate (C-S-H) gel, thereby refining capillary porosity and strengthening the Interfacial Transition Zone (ITZ) between the aggregate and the cement paste. Beyond mechanical improvements, the study highlights the environmental and economic dimensions of this approach. Reducing cement content directly lowers the carbon footprint of its production, positioning metakaolin as a strategic choice for producing sustainable High-Performance Concrete (HPC) with superior durability and exceptional resistance to external stresses.