Use of Furnace Bottom Ash for producing lightweight aggregate concrete with thermal insulation properties

Abstract

The influence brought by Furnace Bottom Ash (FBA) incorporation on the properties of lightweight aggregate concrete was studied systematically. In total, six mixtures of concrete targeted at a 28 d compressive strength of 30 MPa were designed, including one control mix made with all normal weight aggregates and at a water/cement ratio (w/c) of 0.6, and another five lightweight aggregate concrete mixes at a w/c of 0.39 by using 0, 25%, 50%, 75% and 100% FBA replacing natural fine aggregate (crushed fine stone). The testing results of the hardened concrete properties showed that, for the lightweight aggregate concrete using 100% FBA to replace crushed fine stone, a 28 d oven-dried density of about 1500 kg/m3 was obtained. The test results showed the lightweight aggregate concrete had lower strength and stiffness compared to the normal aggregate concrete. But in terms of the effectiveness of strength provided by unit weight of concrete indicated by compressive strength in MPa divided by saturated-surface dried (SSD) density in g/cm3, fc/D, a satisfactory ratio can be obtained when not more than 50% FBA was used to replace the crushed fine stone. The durability property indicated by the chloride ion penetration test shows the lightweight aggregate concrete with FBA had high chloride ion penetrability. The heat insulation property (thermal conductivity K-value) test demonstrated that by using the porous lightweight aggregate, the thermal conductivity could be lowered to around 70% of the control. When more FBA was used to replace crushed fine stone, the thermal conductivity value could be further reduced. The results of this study demonstrated it is feasible to produce lightweight aggregate concrete with high volume of FBA incorporation for building insulation uses.