The Experimental Study On Performance Of Fly Ash Ceramsite Lightweight Aggregate Concrete

Fly ash ceramsite is one kind of artificial lightweight aggregates,which is mainly composed by baked fly ash under a high temperature.it has developed pore structure and lighter weight.The density of concrete of fly ash ceramsite lightweight aggregates is usually less than 1950kg/m3.Compared with ordinary concrete,lightweight aggregate concrete is characterized with a lightweight,high-seismic resistance,high crack resistance,high durability and so on.So the research of fly ash ceramsite lightweight aggregate concrete not only can help to reduce the environmental pollution from fly ash,but also can develop a kind of high-efficiency and ecological-friendly building materials,which has both mechanics performance of ordinary concrete and performance of thermal insulation.In this paper,we take fly ash ceramsite of Ningxia as research object.Based on the chemical composition and structure of ceramsite,the study focuses on its mechanical properties,frost resistance,sulfate resistance,thermal conductivity,high temperature properties and microstructure properties and both using experimental and microscopic method are employed.The main research methods and findings are as follows:1.The influence of fly ash ceramsite on the microstructure of concrete was investigated by using SEM,XRD,IR.The results show that,fly ash ceramsite of Ningxia contains large amounts of silicate and aluminum silicate vitreous and crystalline mullite phase material,and its external defects can be improved by secondary hydration reaction with cement slurry.Meanwhile there are a lot of pores on the outer core of fly ash ceramsite,which can force the cement slurry and mineral admixtures into the ceramic surface to enhance strength of fly ash ceramsite.In further tests,the study examines influence of compressive strength of fly ash ceramsite,pre-wet conditions,water-cement ratio on compressive strength of lightweight aggregate concrete.The results show that,compressive strength of fly ash ceramsite depends primarily on their own ceramic strength,pre-wet time of fly ash ceramsite will affect the strength of ages significantly.Pre-soaking wet and Pre-vacuum wet are better than the pre-pressurized wet.The study aslo investigated the influence of mineral admixtures on different ages of compressive strength,axial compressive strength and elastic modulus.The results show that types and quantities of mineral admixtures can enhance the strength of lightweight aggregate concrete through its ultra-superimposed effect.The order of 128d compressive strength for multiple-doped mineral admixture is:three-doped>double-doped>single-doped.In addition,the study analyzes and cement and interfacial transition zone microstructure by using SEM.The results show that multiple-doped mineral admixture can make ITZ closely connected and reduce the cracks of interface.2.A lot of hydraulic Structures are damaged by freeze-thaw cycles and sulfate attacking in Ningxia.In order to solve these serious problems,we have studied frost resistance of fly ash ceramsite lightweight aggregates concrete under cold water and 5%sodium salt conditions.The results show that damage of water-cement ratio of 0.3 for lightweight aggregate concrete in 5%sodium salt is larger than in cold water,the frost resistance of fly ash ceramsite lightweight aggregates concrete with mineral admixture is better than that of ordinary concrete,relative dynamic elastic modulus of T1 has increased by 9.1%.Through the study of the effect of water-cement ratio and mineral admixture on sulfate attack resistance of fly ash ceramsite lightweight aggregates concrete,it is found that water-cement ratio is reduced at the same cycles of wet and dry,lightweight aggregate concrete strength corrosion coefficient will increase.Fly ash(10%)+ slag(10%)+ silica fume(5%)and fly ash(15%)+ slag(15%)+ silica fume(5%)can improve sulfate attack resistance of lightweight aggregate concrete.3.By systematically investigating the thermal conductivity of fly ash ceramsite lightweight aggregates concrete,the study shows that the thermal conductivity in saturation state is greater than in the dry state;thermal conductivity of lightweight aggregate concrete decreases from 0.39w/(m-k)to 0.30w/(m-k),when the water cement ratio change from 0.3 to 0.4;thermal conductivity of lightweight aggregate concrete admixture are lower when adding different mineral admixtures than without mixing of mineral admixtures.4.The study aslo investigates temperature performance of fly ash ceramsite lightweight aggregates concrete.The results show that by drying under 100?,and the use of the ladder when the heating temperature can reduce the lightweight aggregate concrete burst phenomenon;fly ash,silica fume and slag can significantly reduce the net cracks of the concrete surface;different mineral admixrures have different influence on the properties of lightweight aggregate concrete under high temperature;high temperature expansion of concrete cause less damage of aggregate by using SEM.5.By analyzing consumption of the heat energy of the building models with DeST-h,we can see that structure of fly ash ceramsite lightweight aggregate concrete can be energy-saving by 56.5%,and be capable of meeting requirements energy saving by 50%in cold areas.Through the experiments,we have got a new type of fly ash ceramsite lightweight aggregates concrete,which have advantage of thermal insulation and high strength,and we also found that mineral admixtures can significantly improve the mechanical and durability of fly ash ceramsite lightweight aggregate concrete.