Thermal and Strength Properties of Lightweight Concretes with Variable Porosity Structures

Abstract

The thermal and strength properties and microstructural characteristics of lightweight composites composed of cement matrices aerated by various methods are evaluated. The influence of methods that increase the overall porosity of the cement composites and their overall effect on the thermal and strength properties of the composites are discussed. The porosity of the composites was increased using either an air-entraining admixture, reactive aluminum powder, or aerogel particles. The porosity distribution graphs determined by using mercury and optical porosimetry are presented. A discussion on the technical difficulties that arise during porosity evaluation of the composites with aerogel additive is reviewed. The increased porosity of individual composites results in a significant reduction of the thermal conductivity coefficients, λ. Relatively low values of λ were observed in concretes aerated with the air-entraining admixture and with aerogel particles. Simultaneously, none of the composites showed any significant decrease of the volumetric specific heat, cv. However, aeration of the composites brought about a strong reduction of the compressive strength. The biggest drops were observed for the concretes with air-entraining admixture.