Effect of off-white rice husk ash on strength, porosity, conductivity and corrosion resistance of white concrete

Rice husk ash (RHA) is one of the promising pozzolanic materials that can be blended with Portland cement for the production of durable concrete and the reduction of the environmental impact of the cement industry. Commercially available RHA contains 3% or more graphitic carbon which determines the dark pigmentation of the material. Recent studies have led to the production of carbon neutral rice ash named OWRHA (Off-White Rice Husk Ash), with no graphitic carbon, no crystalline SiO2 and toxic metals, so legitimately considered environmental friendly. This paper presents the results of an experimental investigation on the strength, porosity, corrosion resistance and thermal conductivity of white concrete blended with OWRHA. The results show that the compression strength of the concrete increases with replacement level of OWRHA, while the porosity decreases. Accelerated corrosion tests demonstrate that the use of OWRHA increases the corrosion resistance at all levels of replacement. The results on mortal samples showed that also thermal conductivity and density decrease with the increase in OWRHA and with age. With the intention of reducing the carbon footprint in the cement industry, this study evidences encouraging results for the use of OWRHA in sustainable construction. (C) 2011 Elsevier Ltd. All rights reserved.