Compressible Packing Model Based Study Of Green Concrete

This thesis briefly describes the theoretical basis of Compressible Packing Model. Based on the theory of Compressible Packing Model,two parameters are established. One is Binder Space Factor(BSF),which is the characterization of the space between cementitious material particles and other particle in fresh concrete mixtures. Another one is Surplus Water Index(W),which is the characterization of the amount of surplus mixed water after filling mixtures voids. Aggregate gradation optimization perspective, the impact of different optimization methods of aggregate gradation on workability and mechanical properties and resistance to chloride ion permeability are analyzed. From the perspective of gradation optimization of cementitious materials, the impact of different fineness of mineral admixtures on cement mortar workability and mechanical performance are analyzed. And then investigate the correlation between W or BSF and the performance of concrete or mortar. By analyzing the relationship between workability and W,the mechanical performance and BSF in pure cement concrete with different water-cement ratio, establish performance prediction models and discuss its applicability in mineral admixtures concrete. The key conclusions of this thesis are as followings:(1)Surplus Water index and Binder Space Factor can reflect the surplus degree of mix water after filling mixture voids and the distance between binder particles and aggregate particles respectively. With smaller value of W,the mix will have more surplus water provides the fluidity. With bigger value of BSF, the space around the particles of binder will be smaller,which can increase the density of concrete.(2)Optimization of aggregate gradation is helpful to improve the concrete mixture packing density. Continuity of aggregate gradation must be considered in the optimization because it will be more efficient to improve the packing density of concrete mixture by improve the packing density of aggregate under the premise of aggregate continuous. With the optimization of aggregate gradation, the workability and mechanical properties of concrete will be improved, which have a high correlation with the calculated results of W and BSF. The resistance of concrete to chloride ion permeability coefficient cannot be reduce effectively by optimizing the aggregate gradation only.(3)It is effective to increase the packing density of mortar mixture by adding mineral admixtures. Effect of fly ash on the packing density is higher than that of slag. Adding a kind of mineral admixture, the finer the particle size is, the greater the contribution to packing density will be.For a same dosage of fly ash, the more fine fly ash is, the smaller W value will be, which means the more surplus water in unit volume of mortar will be. The corresponding relationship between the mortar expansion and the W value is high.(4)To the pure cement concrete that water-cement ratio between 0.45-0.57,W value is very high correlation with workability, so that workability prediction model based on the W value has a high correlation. There is a linear relationship between the compressive strength of concrete and BSF, so that the compressive strength prediction model base on the BSF has a high correlation.(5)Correlation between W value and workability is poor because of the material characteristics of mineral admixture,so that it is necessary to introduce correction factor to amending the W value to establish Equivalent Surplus Water index(EW) in mineral admixture concrete. By considering the activities of mineral admixture,Equivalent Cement Space Factor(ECSF)are established and was use to predict the compressive strength of mineral admixture concrete. High precision of the prediction of 28 d compressive strength was found.(6)Base on the study about quantitative relation between indicators and concrete performance, a new mix design of green concrete which is considering the amount of water, cement, mineral admixture and mixture gradation is found.