Experimental Research On The Influence Of Spontaneous Combustion Coal Gangue Coarse Aggregate Characteristics On The Performance Of Sand Lightweight Concrete

Due to the scarcity of resources，many scholars of recycled aggregate concrete wasresearched，including spontaneous combustion coal gangue aggregate. The results showthat the spontaneous combustion coal gangue aggregate can be made smaller than theconcrete strength grade of C40，but its workability is poor，thus the application range islimited.Using the spontaneous combustion gangue replace all natural coarse aggregatepreparation of spontaneous combustion coal gangue sand lightweight concrete，and therealization of ready-mixed concrete and high fluidity target.Selecting the spontaneouscombustion coal gangue of Fuxin GaoDe Mine as materials， using orthogonalexperiment method， and represent spontaneous combustion coal gangue coarseaggregate material properties of mass water absorption rate，particle size distributionrange and coarse aggregate volume content three influencing factors，to investigate thespontaneous combustion coal gangue sand lightweight concrete mixture workabilitystrength and durability，hardening effect.This paper is the sub project of NationalNatural Science Fund《research on the key science problem of resource utilization ofCoal Gangue in cement and concrete》(U1261122).The results achieved of all the studiesare funded by this fund. The main results as follows:(1) mercury injection experiment shows:Fuxin GaoDe mine spontaneous combustioncoal gangue porosity was significantly higher than that of natural coarse aggregate，andthe most is capillary pore.The mass water absorption rate of spontaneous combustioncoal gangue coarse aggregate is about12%，significantly higher than that of naturalstones.Particle size distribution of small grain size coarse aggregate numbers，Higher ofthe water absorption rate，lower of the concrete strength; In oder to prevent spontaneouscombustion coal gangue absorbent mixing water and then reduce the mixture flow，taking the method of incorporating additional water early. When the additional water forcoarse aggregate mass water absorption rate of78%，the mixture obtained the bestworkability.Eventually water cement ratio changed bigger with the adding of additionalwater，the strength of spontaneous combustion coal gangue sand lightweight concrete islower than the baseline.Additional water inside concrete form a capillary channels，leading to the concrete frost resistance and resistance to chloride ion permeabilityvariation. (2) The most significant factor on fresh mixture workability is the mount ofadditional water，followed by the sand ratio and the particle size distribution of coalgangue; additional water is the most significant factor on the early strength ofspontaneous combustion coal gangue sand lightweight concrete，followed by sand ratio.The main factors later strength of spontaneous combustion coal gangue sand lightweightconcrete of for the sand ratio，followed by additional use;gradation of spontaneouscombustion coal gangue has less influence on workability of fresh mixture，compressive strength and split tensile strength.But with the adding of the larger size ofcoarse aggregate grain， mixture will perfomance bleeding and segregating.(3) when the sand rate is0.44and spontaneous combustion coal gangue coarseaggregate grading range is (5mm~10mm):(10mm~15mm):(15mm~20mm)=7:47:46，additional water is0.78，we can prepare C25(strength)，F50(antifreeze grade)，(chlorideion penetration grade) of larger mobility(H≥200mm) spontaneous combustion coalgangue sand lightweight concrete.