Study On The Ceramsite Concrete Prepared With Manufactured Sand

At present,the functional demand and environmental protection demand of the construction industry are getting higher and higher.The construction materials are required to be lightweight,complex performance and environment friendly,and lightweight aggregate concrete can meet these requirements well.However,the lightweight aggregate concrete is usually made up of natural sand,while the natural sand resources shortage will restrict the popularization of lightweight aggregate concrete.As a substitute for natural sand,manufactured sand is seldom applied to lightweight aggregate concrete and studied.Aiming at the problems,this subject prepares ceramsite aggregate concrete with manufactured sand,and studies the effect of manufactured sand on the workability/mechanical properties/durability of ceramsite concrete.Hoping to provide a certain basis for the research and application of ceramsite concrete prepared with manufactured sand.This paper based on the research status of light aggregate concrete and manufactured sand concrete,puts forward the mix design of manufactured sand ceramsite concrete.The influences of sand ratio,water/cement ratio,paste/aggregate ratio and silica fume on its mechanical and durability properties are discussed.Finally,the relationship between the performance of mortar and manufactured sand ceramsite concrete is also explored.The main conclusions include:（1）The particle packing theories and slurry filling theories can effectively guide the mix proportion design of manufactured sand ceramsite concrete.It is made up successfully and meet both the density grade of 1800¹900kg/m³ and trial-mix strength grade 40⁵0MPa at 28d.When the sand ratio（by volume）=35%,water/cement ratio=0.30 and the paste/aggregate ratio=35/65,the manufactured sand ceramsite concrete gets smaller bulk density and better specific strength under the conditions of this paper.（2）The increase of sand ratio will increase the yield stress and plastic viscosity of mortar,and then reduce the fluidity of mortar.There is an approximate linear relationship y=1.37x+261.5（y:slump flow of concrete,x:fluidity of mortar）between fluidity and slump flow.When aggregate packs densely and mortar fills space well,the manufactured sand ceramsite concrete gets better specific strength,higher peak load,lower shrinkage value and superior resistance to chloride penetration.（3）When water/cement ratio increasing in 0.27⁰.40,the fluidity of mortar increases,the compressive strength decreases.the yield stress and plastic viscosity of mortar tend to be stable after water/cement ratio≥0.35.With the increasing of water/cement ratio,the mechanical properties/deformability/resistance to chloride penetration of concrete get weaker and the shrinkage value increases.When water/cement ratio≥0.35,the main factor affecting the workability of concrete is the yield stress,the greater the yield stress,the better the workability.The mixing strength of concrete has an approximate relationship to the water/cement ratio:f_cu,0=0.255f_ce（B/W+1.284）.The approximate correlation between mortar strength and concrete strength is y=0.49x+11.32（y:concrete strength,x:mortar strength）.（4）With the increase of paste/aggregate ratio,the slump/slump flow/compressive strength of the manufactured sand ceramsite concrete will increase.The deformability/resistance to chloride penetration are strongest relatively and the shrinkage value is smallest when paste/aggregate ratio=35/65.The paste is divided into wrapped paste and filling paste in concrete.The wrapped one has a maximum value,while the filling one between the aggregate plays a major role in the workability of the concrete.（5）The mixing of silica fume will not affect the mechanical properties of the manufactured sand ceramsite concrete,but it will reduce the total shrinkage value and shorten the stable time to 52d,and also improve the ability of resistance to chloride penetration to achieve the high performance concrete level.This research shows that the manufactured sand can be used to prepare lightweight aggregate concrete with excellent workability and mechanical properties.Although its durability is not as good as the ordinary lightweight aggregate concrete,while it can reach the high performance concrete level after adding silica fume.