改性橡胶碾压混凝土路用性能及作用机理

Pavement Performance and Mechanism of Action for Modified Rubber Roller Compacted Concrete

为增强碾压混凝土的韧性和耐久性,改善其路用性能,将粒径为1~2 mm的橡胶颗粒用5%NaOH溶液进行改性处理,并设置不做处理的对照组,然后分别以5%、10%、15%、20%等体积取代砂加入碾压混凝土。通过改进VC值、抗压强度、抗折强度、干燥收缩、抗冻等试验,分析橡胶碾压混凝土的工作性能、力学性能和耐久性能,采用工业CT和扫描电镜,对比分析改性前后混合料的孔隙结构和微观形貌,揭示橡胶颗粒对碾压混凝土混合料力学性能的微观作用机理。结果表明:相比于纯碾压混凝土,橡胶颗粒的掺入降低了碾压混凝土早期强度增长速率,改善了碾压混凝土的塑性;在相同橡胶掺量下,改性橡胶碾压混凝土力学性能优于未改性橡胶碾压混凝土,且改性橡胶颗粒掺量不宜大于15%,此时对道路路面结构的承载能力影响较小;当改性橡胶掺量≥15%时,对碾压混凝土的干缩性能有改善效果;改性橡胶颗粒掺量为5%~20%时,掺量越大,对碾压混凝土的抗冻性能改善程度越显著;橡胶颗粒的加入减少了碾压混凝土中的孔隙体积,优化了孔隙结构,改性后的橡胶颗粒表面更加粗糙,减小了橡胶颗粒与水泥砂浆结合面间的裂缝宽度,提高了改性橡胶碾压混凝土混合料中橡胶颗粒与骨料之间的结合强度。

In order to enhance the toughness and durability of roller compacted concrete(RCC)and improve its road performance,rubber particles with sizes of 1-2 mm were modified by 5%NaOH solution,and a control group without treatment was set up.Then,5%,10%,15%,and 20%volume of sand were replaced by RCC.The working performance,mechanical properties,and durability of rubber RCC were analyzed by improving the VC value,compressive strength,flexural strength,drying shrinkage,and frost resistance.The pore structure and microstructure of the mixture before and after modification were compared and analyzed by industrial CT and SEM,and the microscopic mechanism of rubber particles on the mechanical properties of the RCC mixture was revealed.The results show that the incorporation of rubber particles reduces the early strength growth rate of modified rubber RCC and has a negative impact on the mechanical properties of road RCC,but improves its plasticity.With the same rubber content,the mechanical properties of modified rubber RCC are better than those of unmodified rubber RCC,and the content of modified rubber particles should not exceed 15%,which has little effect on the bearing capacity of the road pavement structure.When the modified rubber content exceeds 15%,the dry shrinkage performance of RCC is improved.When the content of modified rubber particles is 5%-20%,the higher the modified rubber content,the more significant improvement in the frost resistance of the RCC.Therefore,the addition of rubber particles reduces the pore volume in RCC and optimizes the pore structure.The surface of the modified rubber particles is rougher,the crack width between the rubber particles and cement mortar is reduced,and the bonding strength between rubber particles and aggregate in the modified rubber RCC mixture is improved.