Research On Asphalt Construction Temperature Determination And Viscosity Characteristics Based On Rotational Plate Viscosity Test Method

At present,high-grade road surface increasingly using various types of modified asphalt and warm mix modified asphalt as the paving material in China.But the current asphalt testing standards have not given the construction temperature prediction for modified asphalt method.The Brookfield Viscosity Test,widely used,cannot control the shear rate during the test process.The modified asphalt construction temperature predicted will be significantly higher than 15-25℃,which cause problems such as aging of asphalt and wasting of energy consumption.This method is also difficult to reflect the change of viscosity and construction temperature after adding warm agents to the modified asphalt,and the test operation is complicated and inefficient.All of it are in conflict with the actual needs of engineering testing.On the basis of carrying out a large number of construction temperature prediction tests with modified and warm mix asphalt,combined with extensive research on asphalt viscosity testing equipment and construction temperature prediction methods at home and abroad,it can be concluded that:To achieve accurate and rapid prediction of the construction temperature of modified asphalt,the key is to develop a viscosity testing device that can actively control the shear rate,and accurately measure the viscosity-temperature curve of the modified asphalt under the appropriate shear rate.The main work has been carried out as follows:（1）A novel method for testing the apparent viscosity of asphalt—rotational plate viscosity Test（RPV）is proposed,which has the advantage of strain control to achieve active control of the shear rate during the viscosity test.This paper systematically introduces the theoretical principles,equipment hardware,program implementation and operation methods of the rotational plate viscosity test,and details the determination process of its core parameters-shear rate.（2）The novel rotational plate viscosity test method and the traditional Brookfield viscosity test method are used to predict the construction temperature of 8 representative asphalt binders and guide the production of mixture test pieces,respectively.The results show that:For the matrix asphalt,the new method solves the problem of cumbersome rotor and speed replacement in the traditional method.The test efficiency is improved by at least 3 times,and the test accuracy is improved by nearly 1 time.In the testing process of SBS and SBR modified asphalt,the new method effectively avoids the problem of excessively high construction temperature prediction caused by the shear thinning effect whcih will occur when testing by traditional methods.In the testing of the three SBS modified asphalts,the new method can fully reflect the temperature-saving and energy-saving performance of the warm mix on the premise of ensuring the quality of the mixture.（3）In addition to the test of construction temperature prediction using a fixed shear rate,and by enriching the shear rate control mode during the test,this paper also uses the rotational plate viscosity test method to expand three studies related to asphalt viscosity,temperature,and shear rate performance tests,including viscosity-temperature-shear rate comprehensive scanning test that reflects the dual dependence of asphalt viscosity on temperature and shear rate,steady state shear test that reflects the thixotropy of asphalt at low shear rates,and characterization of the thixotropy hysteresis loop test.These tests help to fully demonstrate the viscous flow performance of asphalt,and also provide a quick and convenient test method for obtaining some common asphalt performance evaluation indicators,such as zero shear viscosity（₀）and infinite shear viscosity（_∞）.（4）In this paper,the extended test of the rotational plate viscosity test method is used to test 70#asphalt and SBS modified asphalt.It fully demonstrates the dual dependence of the viscosity of two asphalts on temperature and shear rate.The in-depth analysis of the"shear thinning phenomenon"and"thixotropic phenomenon"is also carried out,revealing the essential reason for the traditional method to predict the high construction temperature.This paper also attempts to establish a temperature-shear rate binary regression model that reflects the viscosity of SBS modified asphalt,which provides a basis for more accurate prediction of asphalt construction temperature in the future and research on the rheological properties of modified asphalt.The rotational plate viscosity test method is based on the current widespread use of dynamic shear rate rheometers and 25mm circular plate fixtures for testing,which has strong engineering promotion potential.Its flexible expansion performance also provides a new way to further study the viscosity-temperature-shear rate characteristics of asphalt.