Use of ash derived from refuse incineration as a partial replacement of cement

Abstract

Exploratory work on the use of ash derived from refuse incineration as partial replacement for cement in concrete is described. Laboratory tests were carried out to determine the suitability of the ash. These tests were then followed by actual production of concrete in which various percentages of the cement were replaced by equivalent amounts of ash. The resulting mixes were tested for workability, early strength and strength development with time. The ash derived from refuse incineration is essentially a granular material with a size ranging between 0·085 mm and 0·18 mm. The specific gravity of the ash particles is around 2·1. The ignition loss for the ash is about 15%–20%, suggesting that substantial quantities of organic matter are present in the ash. The predominant chemical constituent of the ash is lime. The high calcium content of 41% indicates that the ash is likely to be hydraulic in nature, and likely to exhibit self-hardening properties. The amounts of silicates, aluminates and chemicals such as potassium, sodium and magnesium are small. Experimental results indicated that it is feasible to incorporate this ash in concrete mixes of satisfactory workability and strength. There was a tendency for mixes containing the ash to have a slightly higher workability than the control (0% ash) mix. In the mix containing 10% ash, strengths comparable with or higher than that of the control mix were obtained, whereas the 20% and 30% ash mixes had strengths about 40%–50% lower.