Fabrication And Performance Of Foam Concrete With Circulating Fluidized Bed Combustion Fly Ash

CFBC fly ash which is the combustion products of coal and sulphur-fixing agent (generally are limestones) under850-900℃, is obtained from the flue outlet. Unlike the traditional fly ash, CFBC fly ash contains a certain amount of anhydrite and free lime, has the properties of selfhardening and expansion. If CFBC fly ash used in building materials directly would be easy to result in later expansion of products. Therefore, CFBC fly ash is usually stacked, which not only occupy a lot of land resulting in secondary pollution but also block the application of circulating fluidized bed combustion technology. Based on the envision of using a large volume of pore in the foam concrete for reducing the expansion from CFBC fly ash and reducing the shrinkage of foam concrete, CFBC fly ash is utilized for the preparation of foam concrete with different density, which is not only helpful for sustainable development and environmental protection, but conform to the state advocates of recycling, energy saving and emission reduction policy.This paper studied the properties and excitation technologies of CFBC fly ash and then prepared the foam concrete with different density. The influence factor of compressive strength and durability of foam concrete with CFBC fly ash are also studied. The results showed that:Grinding process is good for improving the activity of CFBC fly ash. The addition of lime and aluminate cement in system of CFBC ash (70%)-clinker (30%) can accelerate the setting and hardening, shorten the setting time, release expanding energy early. With the addition of8%lime,2%aluminate cement,70%CFBC fly ash (d0.5=12.225μm) and curing in the circumstance of60℃for24h, the foam concrete with compressive strength achieving3.38MPa and the bulk density of512kg/m3were prepared. Besides, altering the foam content can prepare foam concrete with level of A04、 A06、A08. Through the orthogonal experiment and the mix optimization, the foam concrete with compressive strength of0.5MPa and the bulk density of192kg/m3at the content of lime8%, CFBC fly ash (d0.5=12.225μm)60%, cement (P.O52.5R)32%, PP (0.64%) and water to solid ratio of0.5were prepared. As foam concrete with lower density (A04-A08) has high porosity, compressive strength wouldn’t change significantly when the content of CFBC fly ash changed or composition fluctuation. However, the strength of foam concrete with density of1000kg/m3is reduced with an increase in CFBC fly ash content. At content of CFBC fly ash (d0.5=12.225[μm)60%, cement (P.O42.5R)40%, sand (0.3-0.6mm)5%and water to solid ratio of0.4, the foam concrete with compressive strength of11.6MPa and the bulk density of1030kg/m3are prepared.Compared with the existing foam concrete, foam concrete with CFBC fly ash has the properties of lower density, higher compressive strength, lower coefficient of thermal conductivity but higher water absorption. The shrinkage of foam concrete with CFBC fly ash is lower than that of foam concrete with cement and the splitting tensile strength after dry-wet circulation reduce a little, the frost-resistance of foam concrete with CFBC fly ash of different density (except density of200kg/m3) meet the requirements of standard.