Investigation on usability of cement and alkali activated pastes in coated lightweight aggregate production

Pumice, which is abundant worldwide and particularly in Turkey, is utilized in various industries. However, its potential contribution to the national economy has not been fully realized due to underutilization. Due to its hollow structure, its mechanical properties are not satisfactory. For this reason, it is not preferred to be used in the production of structural lightweight concrete applications. However, it is possible to improve their mechanical properties by coating their surfaces and use them in the production of structural lightweight concrete. In this study, pumice aggregates were coated with cement paste and alkali activated mortars with different properties. Cement pastes, were obtained 0.50 and 0.55 water/cement ratio and by using %1,5 super plasticizer with 0.30-0.35 water/cement ratio while preparing alkaline activated mortars, fly ash, water, and sand were mixed with 8 mol, 10 mol, and 12 mol sodium silicate (NaOH) and sodium hydroxide (Na₂SiO₃) aqueous solutions as alkali activators. Slump-flow, Marsh funnel flow time, compressive strength and flexural strength of the cement paste and alkali activated mortars used in the coating were investigated. The water absorption, impact value, grain strength, specific gravity, loose density, microstructure, and coat ability properties of the coated aggregates were investigated. In addition to physical properties, compressive strength, splitting tensile strength, flexural strength, capillary water absorption, high temperature, freeze thaw and microstructure of concretes produced with coated aggregates were investigated. It was observed that the fluidity of the materials to be used in the coating improves the coating performance. It was determined that the grain strength of the coated aggregates increased and the water absorption rate decreased up to 59%. Increases in compressive strength, splitting tensile strength, flexural strength and decreases in capillary water absorption rate of concretes produced with coated aggregates were determined. As a result, it was determined that the performance of the aggregates increased as a result of coating and the concrete to be produced with them has the characteristics of lightweight concrete. Keywords: Pumice, Structural Lightweight Concrete, Coated Aggregate, Cement Paste, Alkali Activated Mortar