Preparation And Performance Study Of High-Strength Low-Shrinkage Cement Stabilized Crushed Stone

Cement-stabilized gravel base materials are very sensitive to changes in temperature and humidity,so they are prone to shrinkage cracking,which can lead to reflective cracks in the asphalt pavement,which in turn affects the pavement performance and durability of the highway.In this paper,on the basis of ensuring the strength of the base layer,the crack disease of semi-rigid base layer was reduced by optimizing the gradation design and applying the new synergist to prepare highstrength and low-shrinkage cement stabilized crushed stone,and the performance research was carried out.The main research contents and conclusions are as follows:(1)Design grading and optimization of vibration filling method plus i method:based on vibration filling method,the coarse aggregate gradation is determined by the maximum vibration density index;Based on the i method,the fine aggregate gradation corresponding to the best i value was determined by CBR and unconfined compressive strength test results,and the optimal i value was 0.65.The three structural types of cement-stabilized crushed stone were synthesized according to different mass ratios: suspension compactness,skeleton compactness and skeleton void,and the fractal theory was applied to analyze the compressive and splitting strength indexes of cement-stabilized crushed stone under different grades,and finally the optimal synthetic grade was obtained as skeleton dense gradation D by comparing the test results.(2)Preparation and mechanical properties of high-strength and low-shrinkage cement stabilized crushed stone: On the basis of the preferred grade D,a new synergist is added to further improve its strength and crack resistance.Through the analysis of 7D compressive strength and 7D splitting strength test results,it is found that the optimal mixing ratio of 0.6% synergist is added at 4% cement dose,and its compressive strength and splitting strength are increased by 7.2% and 5.2%,respectively,compared with cement stabilized gravel without synergist.The results of the tensile strength test showed that the incorporation of synergist showed an enhancement effect on the flexural tensile strength of cement-stabilized crushed stone at different ages,and the bending tensile strength of 7d was the highest,reaching 9.3%,which indicated that the synergist improved the early bending tensile strength greatly.Finally,the microscopic morphology analysis of cement-stabilized lithotripsy with synergist was carried out by electron microscopy scanning test(SEM),and the reasons for the influence of synergist on cement-stabilized lithotripsy were obtained.(3)Dry shrinkage performance verification: Through the dry shrinkage test of cement-stabilized crushed stone with different design grades and cement-stabilized crushed stone mixed with synergist under the preferred grade,the crack resistance effect of high-strength and low-shrinkage cement-stabilized crushed stone was further verified.At the same time,the variation law of water loss rate and dry shrinkage strain of cement-stabilized crushed stone of different graded types at different ages,and the influence of synergists on the dry-shrinkage performance of cement-stabilized crushed stone were explored.Finally,the function fitting of the dry shrinkage data shows that the long-term dry shrinkage coefficient of highstrength and low-shrinkage cement-stabilized crushed stone is 41.34*10-5,and the shortest shrinkage coefficient can be seen through comparative analysis,so the crack resistance of high-strength and low-shrinkage cement-stabilized crushed stone is verified.A mathematical model was established to predict the cumulative dryshrinkage strain of high-strength and low-shrinkage cement stabilized crushed stone,and the Gaussian regression process equation was best obtained by analyzing the robustness and generalization ability of the model.