Study On The Influence Of Limestone Powder On Properties Of Foam Concrete

Because of light weight, heat insulation, anti-seismic, sound insulation and other excellent properties, foam concrete is heavily favored in recent years. Considering that it has high porosity, high cementitious materials content and lacking aggregates, foam concrete still has many problems with its performance. Also, adding mineral admixtures is the main way in the modification research, not only because there are extensive material resources, but also it's an effective way for energy conservation and waste utilization that conform to the national policies.Under the circumstance of increasingly intense fly ash resource, as a new kind of mineral admixture, limestone powder is acquiring more and more attention. So considering the application situation of limestone powder in the concrete field of our country and referring lots of literatures related to limestone powder application, the author carried out a series of experimental study on the influence of limestone powder on properties of foam concrete based on previous research results. Firstly, the effect of limestone powder fineness on the water demand and mortar strength has been analyzed to acquire the basic properties of limestone powder. Secondly, the influence of limestone powder on the compressive strength of foam concrete has been investigated. Some evaluation methods such as coefficient of specific strength(CCS) and rate of activity contribution(RAC) have been used to evaluate the micro-activity of limestone powder. Finally, the influence of limestone powder on durability of foam concrete has been researched relatively systematically. The results show that:The water demand ratios of three different kinds of limestone powder which cantain 26.57%, 37.93%, 58.41% fine particles(<10?m) are 94.5%, 91.5%, 89.5% respectively, which indicates that the limestone powder can arouse water-reducing effect through filling effect of the fine particles and the water-reducing effect is more and more obvious with the increase of limestone powder fineness.The 3d and 28 d compressive strength of A05 foam concrete can reach 0.83 MPa and 2.34 MPa respectively when using the foaming agent type A, keeping the water-binder ratio at 0.5 and adding into less than 20% limestone powder and about 10% fly ash. Therefore, it's likely to reduce the cost of foam concrete production through decreasing the content of cement, meanwhile maintain the compressive strength of foam concrete basically.When keeping the water-binder ratio at 0.5, the dry shrinkage of foam concrete with 20% limestone powder contained comes to the lowest level, 2.21×10-3. Also the rate of dry shrinkage can be restrained effectively when mixing the fly ash used as the combined admixture into it and the dry shrinkage would hit the lowest level of 1.51×10-3 when the fly ash content is 5%. Adding limestone powder with slag can improve the anti-frost property of foam concrete and guarantee the strength even after 25 freeze-thaw cycles. The carbonation depth of the foam concrete decreases firstly and then rises with the increase of content of limestone powder, and carbonation depth hits the bottom level when the replacement of limestone powder is 10%. After urgent cold and heat treatment, the appearance of foam concrete with different contents of limestone powder still keep well without apparent defects.This research introduces an effective way to prepare A03 and A05 foam concrete which are used widely in the cast-in-situ projects of building roofs currently through replacing the cement with three different types of limestone powder. Obviously, it can not only reduce the massive solid waste, limestone powder, in the quarries, reduce the cement content and carbon emission in the foam concrete production, but also reduce about 10% to 20% foam concrete production cost while maintaining the early age strength, which shows great economic and social benefits.