Study on the preparation and properties of high-porosity foamed concretes based on ordinary Portland cement

Fire-resistant, low-cost, high-porosity foamed concretes, which have desirable thermal-insulation properties and can be cast in-place, were prepared by adding preformed foam to ordinary Portland-cement slurries. The air-void structure, hardened properties, curing method, and stability of the fresh foamed concrete were investigated. The results indicated that foamed concretes with porosities of 88.5%-95.4%, compressive strengths of 0.12 MPa-0.75 MPa, and low thermal conductivities of 0.036 W m(-1) K-1 to 0.063 W m(-1) K-1 could be obtained with the addition of preformed foam. Moreover, the addition of an accelerator and low dosages of a superplasticizer, as well as a reduction in the water-to-cement ratio prevented the collapse of the fresh foamed concrete. Small air-void sizes and narrow distributions of these sizes were obtained by increasing the apparent density, and by adding an accelerator and a suitable superplasticizer. In addition, humidity-insulated curing enhanced the strength of the foamed concrete. (C) 2015 Elsevier Ltd. All rights reserved.