Application Research On New Method Of Automatic Test For Setting Time Of Cement Based Materials

There are several drawbacks on traditional testing method of determining the setting time of concrete:it’s inconvenience to operate when testing the setting time of the concrete;the actual site conditions are hard to be reflected by the laboratory experiments;it fails to reflect the degree of hydration directly on the test principle.In order to conquer above drawbacks,a new testing method is presented in this paper.According to this new method,setting time of concrete is determined by testing the temperature rise of concrete hydration in early ages.The main parts of this dissertation are as follows:1.The principle of the setting time of concrete based on the temperature rise of hydration.Based on the study and analysis of the rate curve of the hydration temperature rise under the thermal insulation and natural condition,the testing principle of the setting time of the concrete was studied.2.Comparative study between the new method and the traditional method.Firstly,comparing the differences between the two methods on test results and the procedures of the testing operation by the contrast test.Secondly,determining the application of the new method in sample size,operation steps,the results of processing and the determination of setting time,test notes,etc.And a step further,to form a standard of test method.3.Study on the applicability of the new method to different kinds of concrete.According to standardized test method,different types of concrete were tested,such as low slump concrete,ordinary concrete and the self compacting concrete of low water to binder ratio.And then the applicability of the test method to various kinds of concrete in engineering could be verified.4.Study on the applicability of the new method in construction site.In the light of traditional method,the setting time of concrete is influenced by the environmental conditions and the transportation and the testing results can hardly guide the issues on projects.The applicability of the new method in the field of construction site was studied by the field experiment,which will provide basis for scheduling and quality control in construction site.The study results show that this method is based on the principle of hydration of concrete directly.And the test results reflect the nature of the growth of concrete strength.Comparing with the traditional method of penetration resistance,tests on concrete specimen avoids the errors caused by differences between mortar and concrete penetration resistance method in testing.At the same time,it’s convenient for the usage of various kinds of concrete to work out the problem of the difficulty of mortar test.Then the simplicity and accuracy of the operation were improved.In addition,the method is not only applicable to the laboratory operation,but also can be used in the construction site.It provides a more reliable basis for the engineering practice,the concrete maintenance,the construction schedule and the related quality control.