| Reactive powder concrete is a new type of cement based composite material with low brittleness,high toughness,high strength and good volume stability.Because of the high cost,the complex process,the lack of relevant norms,and the lack of a large number of simulation studies,the application in domestic engineering is less.Based on the conventional materials,the work performance and compressive strength of the active powder concrete are studied in this paper.The relationship between the microscopic dispersion characteristics and the strength of the reactive powder concrete system is revealed by means of scanning electron microscopy.The factors that affect the strength of reactive powder concrete are summarized,and the active powder concrete with the compressive strength of 130MPa is prepared.Through indoor contrast test,it is clear that the factors influencing the workability of RPC mixture include feeding sequence,mixing time,high efficiency water reducing agent type,steel fiber content and water binder ratio.Feeding order:the cementitious material mixing first,adding high efficiency water reducing agent and water wet mixing,adding steel fiber and quartz sand wet mix,the mixing time was 6?8min;the experiment selects the naphthalene high efficiency water reducing agent,optimizes the steel fiber content and ensures the good working performance of the mixture.steel fiber mixing amount of cement 20%-30%;water cement ratio control in the range 0.18?0.20,the measured slump value is 165?180mm.Through the laboratory comparison test,the factors affecting the RPC strength are water glue ratio range,type and ratio of cementitious material,the ratio of quartz sand,the types and proportions of steel fibers,the types and proportions of high efficiency water reducing agents,the order of feeding and the system of health maintenance.Water to glue ratio is an important index to influence the strength of reactive powder concrete.The suitable ratio of water to glue can improve the fluidity of the mixture.the water binder ratio is controlled from 0.18 to 0.20 with the appropriate dosage of the suitable naphthalene high efficiency water reducing agent.In cementitious materials,cement and silica fume contain rich active ingredients.In the hydration reaction,a large amount of gel is generated for strength growth,the best ratio of cementitious material is determined by comparing the effect of filling the void of cement stone and reducing the porosity.The optimum gradation and maximum compactness index of the three grade quartz sand provide the good development space for the benign growth of the hydrogel calcium silicate gel.The steel fiber with a length of 12mm,a diameter of 0.15mm,a slenderness ratio of 80,and the amount of steel fiber accounted for 20%?30%of the cement content,a good dispersing effect in the process of material mixing.The experiment selects the naphthalene high efficiency water reducing agent with the water reducing efficiency of 25%?35%,and the dosage is 0.95%of the cement quality.the water glue ratio is effectively reduced and the working performance of the mixture is in the best condition.The parameters of RPC indoor mixing,molding and health maintenance were clarified,and the relationship between the parameters and the compressive strength was analyzed.Scanning electron microscopy(SEM)was used to observe the microstructural dispersion in RPC,when the curing temperature is 90 ?,a large number of cloud hydrated calcium silicate gel can promote the increase of the strength of the active powder concrete,the extension of the crack is combined with the destruction of the active powder concrete and the connection between the exposed material and the matrix,etc.It is concluded that there is an inevitable relationship between the micro dispersion state and the strength,which is helpful to the optimization of the mechanical properties of the active powder concrete.The research results provide support for the application of the technology in Luqiao,high speed rail and other projects. |
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