Air-void system of foamed concrete and its effect on mechanical properties

Abstract

A study has been undertaken to investigate the effect of air content ranging from approximately 10 to 70% introduced by preformed foam of same quality on the air-void system and the effect of the air-void system on the mechanical properties of foamed concrete without sand. The linear traverse method (ASTM C 457) was used to determine air-void system, which refers to air content, average air-void size, air-void frequency, and spacing factor. The cementitious material used in this study was blended cement with 50% of normal portland cement and 50% of ground-granulated blastfurnace slag (GGBFS) by weight; the water-cementitious material ratio (w/cm) of the foamed concrete was 0.3. For the range of air content adopted, the fresh densities of the foamed concrete ranged from approximately 600 to 1900 kg/m 3with a corresponding compressive strength range of approximately 2 to 58 MPa were obtained. The results show that although the same quality of foam was introduced, the air-void size and frequency and, hence, spacing factor in the foamed concrete, varied with different air contents, which in turn affected the mechanical properties of the concrete. In this study, it was found that the air-void system with a spacing factor, air-void size, and air content of 0.04 mm, 0.12 mm, and 42%, respectively, were to be optimal, and at which, a high strength-to-weight ratio can be achieved. The results also indicated that the inclusion of air voids in foamed concrete had a greater effect on compressive strength than the modulus of elasticity. A numerical analysis was carried out to verify the experimentally observed effect of an air-void system on strength and modulus. The result of the numerical analysis concurred with the experimental observations. Copyright © 2006, American Concrete Institute. All rights reserved.