Properties of a foamed concrete with soil as filler

Properties of a foamed concrete with soil as filler Ma Cong, Chen Bing ⇑ Department of Civil Engineering, Shanghai Jiaotong University, Shanghai 200240, PR China highlights Soil-based foam concrete exhibits unusual physical properties, such as strength, thermal insulation and water resistance. Silica fume added into soil-based foamed concrete can greatly increase the physical properties. The fit of mathematical expressions based on hygroscopic test results was investigated. article info Article history: Received 12 May 2014 Received in revised form 27 September 2014 Accepted 28 November 2014 Available online 12 December 2014 Keywords: Soil Thermal conductivity Compressive strength Foam Density Water resistance Hygroscopic property abstract Ordinary Portland cement, soil and foaming agent are the raw materials used to make soil-based foamed concrete. The effects of foam content and silica fume on the physical properties of soil-based foamed concrete, such as the dry density, 28-day compressive strength, thermal conductivity, water resistance and pore structure, were studied. The experimental results indicate that the foam and silica fume contents have a large impact on the physical properties of soil-based foamed concrete. The thermal conductivity, density, water resistance and compressive strength decrease with increasing volume fractions of foam. The compressive strength, the thermal insulation and water resistance are all improved by increasing the content of silica fume. Soil-based foamed concrete consisting of 20% silica fume with a density of 800 kg/m 3 , compressive strength of 7.5 MPa and thermal conductivity of 0.16 W/m K can be used as water-resistant lightweight concrete. The hygroscopic tests were performed and the results indicate that the addition of silica fume has some effect on the hygroscopic property of soil-based foamed concrete. Several fitting curves have been obtained, the fitted functions developed by the Kumaran model and Cubic function have better fitting parameters. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Soil-based construction buildings have been used in China for centuries, especially in rural regions of the Loess Plateau and Fujian Province [1,2]. In recent years, the soil which can be used as an eco- friendly building material has attracted lots of attention. Some researchers have studied the mechanical properties of soil-based concrete used in modern buildings [3–5]. Adesanya’s tests showed that the trend of compressive strength development was similar to that of conventional concrete. The 28-day compressive strength of laterite and clay based concrete ranged from 8 to 22 MPa for densities of 1500–2350 kg/m 3 [4]. Furthermore, the soil-based ancient buildings have characteris- tics of coolness in the summer and warmth in the winter for the existing of natural micro-pore structures in mud walls. Inspired by this discovery, several researchers have introduced soil into lightweight concrete [6,7]. Goual et al. studied clayey cellular concrete and found that the compressive strength and thermal conductivity ranged from 0.95–3.85 MPa and 0.201–0.281 W/m K for densities of 843–1038 kg/m 3 , respectively [7]. Porosity identifi- cation revealed the existence of two distinct pores classes: inher- ent micropores in the clay and macropores or gaseous cells, resulting from the addition of aluminium powder at the time of mixing. On account of the only moderate strength requirement for foamed concrete, soil can be used as eco-friendly and cheap filler for creating novel foamed concrete some excellent properties. Soil-based foamed concrete is a novel lightweight construction material consisting of Portland cement, soil, water and foaming agent. Although the foamed concrete is not used as load-bearing wall material, it is necessary to improve the strength of soil-based foamed concrete without thermal insulation performance degrada- tion. Generally, fly ash, silica fume and fibres are often added into the mixture to customise the mechanical properties of foamed concrete [8–10]. Fly ash has been used in concentrations of 30–70 wt% [8] and silica fume (up to 10 wt% by weight of cement) has been added to intensify the cement strength [10]. http://dx.doi.org/10.1016/j.conbuildmat.2014.11.066 0950-0618/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +86 13917109022. E-mail address: [email protected] (C. Bing). Construction and Building Materials 76 (2015) 61–69 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat