Experimental Study On Optimum Proportioning Of Mineral Admixture Rubber Concrete For Road

In areas where freezing and thawing alternate frequently,concrete pavements are prone to fracture and damage by repeated rolling and freeze-thaw cycles.Rubber concrete has significant ductility and frost resistance,and is promising for use in areas with frequent freeze-thaw,but its low compressive strength limits its development and can be optimally modified for use.In order to improve the paving performance of rubber concrete and to determine the optimum ratio,the following studies were conducted:(1)to replace cement with fly ash of equal mass,to investigate the effect of fly ash dosing on the performance of rubber concrete,and to determine the optimum range of fly ash dosing;(2)to replace cement with silica fume of equal mass,to investigate the effect of silica fume dosing on the performance of rubber concrete,and to determine the optimum range of silica fume dosing;(3)Mix fly ash and silicon powder into rubber concrete,explore the impact of the amount of fly ash and silicon powder on the performance of rubber concrete,and find out the reasonable range of compound mixing.(4)The BP neural network model of relative dynamic modulus was established using MATLAB software to predict the frost resistance of rubber concrete.The main research findings are as follows.(1)Within a certain age range,with the increase of fly ash admixture,the mechanical and frost resistance properties of rubber concrete first improve and then decrease,and the relatively optimal fly ash admixture levels for compressive strength,splitting tensile strength and freeze-thaw resistance are 0%～14.3%,0%～13.1% and 5%～15% respectively.The best fly ash admixture for overall performance ranges is 5%～13.1%.(2)Within a certain age range,the mechanical and frost resistance properties of rubber concrete improve and then decrease as the amount of silica fume increases.The relative best silica fume admixtures for compressive strength,splitting tensile strength and freeze-thaw resistance are 0%～13.8%,0%～10.9% and 3%～9% respectively.That is to say,the best overall performance of silica fume doping range is 3%～9%.(3)With the increase of fly ash and silica fume,the compressive strength,splitting tensile strength and frost resistance of rubber concrete first increase and then decrease,and the change of compressive strength is more significant.The optimum amount of fly ash is6.5%～9%,and the corresponding optimum amount of silica fume is 3.2%～6%.(4)A BP neural network frost resistance prediction model with structure 3-11-1 was established based on the relative dynamic modulus test data of rubber concrete compounded with fly ash and silica fume obtained from freeze-thaw tests.The model was validated by test samples,and the predicted values agreed with the test values with high accuracy,which can meet the frost resistance assessment and prediction of rubber concrete projects.