چكيده به لاتين
The first goal in this research is to determine the workability and rheological properties of self-compacting concrete, then the relationship between rheological parameters and workability was investigated, and based on concrete workability, numerical models were presented to predict rheological parameters. In the second part of this research, bond strength relationships between concrete layers have been examined, and the parameters of thixotropy, roughness and paste volume, as well as values of yield stress and viscosity have been examined. Finally, to predict the residual strength in different time intervals, models were presented based on delay time, thixotropy, roughness and volume of paste. To achieve these goals, 8 samples were designed and made with the variables. The results from the workability section showed that increasing the size of the aggregate leads to a decrease in workability and an increase in the need for superplasticizer. Among the prepared samples, the lowest workability was related to the sample containing zeolite additive. Considering the results of the rheology tests and comparing and relating it with concrete workability characteristics, the most relevant tests for determining the yield stress are the slump flow test and the L-Box test, which have a correlation coefficient of -0.803 and -0.793, respectively. Also, the most relevant test for determining viscosity is V-Funnel, T50 time and Sieve segregation, which are related to viscosity with correlation coefficients of 0.829, 0.74, and 0.735, respectively. Based on these parameters, models were presented to predict yield stress and plastic viscosity. In the second part of this research, the bond strength of concrete samples with delay times of 15, 30, 60 and 100 minutes was investigated with two methods of compressive and pull off. The results showed that the strength drop in the pull off test is more than the compressive strength test, which can be caused by the type of load applied to the concrete. Also, the effect of different parameters on the bond strength was investigated. Based on the results obtained, at lower delay times, the thixotropy has the greatest (inverse) effect on the bond strength, at longer delay times, the bond strength is affected by the surface roughness of the first layer, which directly affects the bond strength and Finally, by examining the effect of the volume of the paste, it was concluded that the volume of the paste helps mixing between the two layers in a short time and increases the adhesion strength, but in more delay times, because it has a negative effect on the surface roughness of the first layer, it leads to a decrease in the bond strength. will be Also, viscosity is closely related to thixotropy and roughness, and in this way, its effect is seen in this two-parameter, and it is not seen independently in the calculations of bond strength. In this research, no significant relationship was found between bond strength and yeild stress. Finally, by using parameters of roughness, thixotropy and paste volume, predictive models for bond strength were presented.
