چكيده به لاتين
In this research, the main purpose of the done tests , is to evaluate the relationships between the rheological properties and setting time in self-consolidating concrete (scc) mixtures. Rheology is the science of studying the materials deformation and flow and in general , in scc mixtures , the most important variables are the rheological variables. The setting time is also one of the most important parameters existing in all kinds of concrete. It should be noted that different definitions have been presented for the time of setting in various sources. As a short definition, it can be said that the setting time is a period of time in which concrete changes from fluid to solid phase.
In the rheology section, workability tests and rheometric experiments have been performed. Also in the section of determining the setting time, the main method used to determine the time of setting is the electrical resistance measurement method (E.R.). Despite there is a long time of using this method in determination the time of setting of concrete, there is no standard written for it. Therefore in this research said method and its results have also been brought under more precise verification and study (which can be referred to as a side purpose). For this purpose, standard methods have been used to check the accuracy of the results. The standard methods that have been chosen are the Vicat needle and the Penetration resistance method (P.R.). Based on the obtained results, it was noted that the fault percentage of E.R in comparison with the P.R is about 5.3 and 3.59 in determining the initial and final setting time respectively.Therefore, it was found that the results obtained by this method(E.R.) are reliable. Thus, by using the results obtained from the E.R method, the existence or non-existance of relationships between the rheological properties and the setting time was studied. According to the obtained results, it was found that there are behavioral and numerical relationships between them. Based on the obtained results it was found that in the scc mixtures with lower slump flow and longer T50, the setting time becomes shorter but, on the other hand no relationship was found between the J-Ring results and setting time.
In the section of rheometric study of the scc mixtures performed by the rheometer, it was found that there is also important relationships between the static yield stress, dynamic yield stress and the thixothropy on one side and the setting time on the other side. Of the obtained results, it was found that the higher static and dynamic yield stress has led to occurrence of shorter setting time and in connection to this issue, some numerical relations were also introduced. With respect to thixothropy, using the electrical resistance was also evaluated and its results were studied, though more researche is needed in this section and there is no definite conclusion in said regards.Thus, in this research it has been endevoured to study the relationship between the setting time and rheology properties in scc mixtures as much as possible and abviate the existing gaps.
Keywords: RHEOLOGY, WORKABILITY, SETTING TIME , ELECTRICAL RESISTIVITY
