Study On High Fluidity Spontaneous Combustion Coal Gangue Full-lightweight Concrete

In recent years, environmental protection consciousness strengthens among people day byday. People also pay more and more attention to the variety of industrial waste residuecomprehensive utilization problem. Solid waste utilization has become the research focus ofbuilding materials in twenty-first Century. Coal gangue is the wastes set out during the coalmining and processing, is the largest industrial waste residues. If we can realize its utilization incement concrete, the significance is great. This paper is the sub project of National NaturalScience Fund Joint Coal Project "Research on key scientific problem of Coal gangue in cementand concrete utilization"(U1261122). All results of the studies are in the fund of the project.Firstly, this paper studys the preparation and main technical performance of spontaneouscombustion coal gangue aggregate. Secondly, determines the coal gangue aggregate gradingrange based on the theory of maximum density curve, select0.44,0.47,0.50,0.53,0.56,0.59,0.62,0.65and0.68as n values, establish ideal gradation curve formula for the spontaneouscombustion coal gangue aggregate concrete. Once again, through the orthogonal experimentdesign, using orthogonal design to analyse the influence of the fly ash replacement ratio,water-reducing rate of water-reducing agent, and sand ratio which were used as three mix factorsin the mixture’s workability and harden strength of spontaneous combustion coal ganguefull-lightweight concrete, and discussed permeability resistance of chloride ion of somespecimen. Finally, through the contrast test studys water-reducing agent varieties on the effect ofspontaneous combustion coal gangue complete lightweight concrete mixture slump loss, throughseparate mixing carboxymethyl cellulose, air-entraining agent and fly ash, to realize the highfluidity target(H>160mm) of the coal gangue aggregate concrete.The result shows that: spontaneous combustion coal gangue aggregate has high waterabsorption and porosity,24h water absorption rate is higher than11%, the total porosity is about27%, is10times as big as natural stone, pore structure distribution characteristic is also differentfrom natural stone. On the basis of the mix design, the ideal curve formula index is n=0.63foraggregate gradation of spontaneous combustion coal gangue lightweight concrete. Orthogonalexperiment range, variance and regression analysis shows that under the premise fluidity(H>160mm) goal of the ready-mixed concrete, the most significant influence is fly ashreplacement ratio, then are the water-reducing rate and n value of maximum density curve, the optimum mixture ratio combinations is A1B2C3, that is fly ash replacement ratio is15%,water-reducing rate is14%and n value is0.62. Chloride ion permeability test results show thatthe performance on resistance to chloride ion penetration of high fluidity spontaneouscombustion coal gangue lightweight concrete inferior than ordinary concrete. Contrastexperiment shows that polycarboxylate type superplasticizer has better adaptability thannaphthalene type superplasticizer on the preparation of spontaneous combustion coal gangueconcrete, complex use polycarboxylate type superplasticizer and air-entraining agent can controlthe gradual loss in slump of the concrete mixture more effective.Through the study on spontaneous combustion coal gangue lightweight concrete, as long aswe adopt certain technical means, spontaneous combustion coal gangue can completely replaceall the natural sand, stone to prepare high fluidity concrete. Coal gangue is used as aggregate inconcrete is a more reasonable way for coal gangue using, and more fully, completely, but alsoeconomic, environmental and has obvious social benefits than other coal gangue using method.The study on preparation and properties of spontaneous combustion coal gangue lightweightconcrete has provided theory basis and technical support for spontaneous combustion coalgangue lightweight concrete using in civil engineering.