Thermal and mechanical properties of gypsum–cement foam concrete: effects of surfactant

Abstract

The mineral foams studied were mainly composed of a reactive, partially anhydrous calcium sulphate (90%) and Portland cement (10%), mixed with a low water-to-binder ratio (W/B = .35) leading to a highly concentrated suspension. The foaming method used allowed a wide foam density range (250 < ρ < 820 kg/m3) to be obtained after hardening and drying, with the same mineral suspension composition. To ensure that foam formed and remained stable until the material had set, six surfactants were chosen. The influence of the surfactants on paste properties in the fresh state was evaluated and the thermal and mechanical performances of gypsum–cement products (foamed and unfoamed) were analysed. The thermal conductivity of gypsum–cement foams evolved linearly with density but compressive strength values were widely dispersed and depended on the porous structure, which was strongly dependent on surfactant type and content. The performance levels of gypsum–cement foams were compared with those of lightweight foam concrete from litterature. The most efficient surfactants and the optimum content range leading to the best thermomechanical compromise were identified. They ensured a minimal compressive strength of 2 MPa, and thermal conductivity lower than .2 W/(m.K).