Investigation of Properties of Lightweight Geopolymer Mortars Containing Expanded Clay

Abstract

This study investigates the fresh and mechanical properties of lightweight geopolymer mortars incorporating expanded clay powder as a binder and expanded clay aggregate as a lightweight aggregate. The influence of varying binder/activator ratios (1.0–2.0) on fresh density, workability, water absorption, and mechanical strength was systematically evaluated. Despite variations in binder content, fresh densities remained within a narrow range due to the low specific gravity of the raw materials. However, an increase in binder/activator ratio led to enhanced hardened density, reduced water absorption, and improved compressive and flexural strengths. The results indicated that the optimum binder/activator ratio was 1.8, where the highest 28-day compressive (25 MPa) and flexural (7.3 MPa) strengths were achieved. Workability decreased significantly with higher binder contents due to increased viscosity and reduced liquid-to-solid ratio. Excessive binder ratios beyond 1.8 did not yield further mechanical improvement and slightly reduced performance, possibly due to incomplete dispersion or micro-defect formation. The study concludes that a binder/activator ratio of 1.8 offers the best balance between mechanical performance and processability for lightweight geopolymer mortars utilizing expanded clay-based components.