多尺度钢纤维组合与碳纳米管对RPC力学性能影响

Influence of Multi-scale Steel Fiber Combination and Carbon Nanotube on Mechanical Properties of Reactive Powder Concrete

研究了多尺度钢纤维组合与碳纳米管对活性粉末混凝土(RPC)力学性能的影响,并通过压汞法(MIP)对掺加碳纳米管前后RPC内部的孔结构进行了测定.结果表明:不同尺度的钢纤维组合掺加相对于单掺大尺度钢纤维可以显著提高RPC的力学性能;双掺总量一定的大、中尺度钢纤维时,提高中尺度钢纤维比例会降低RPC的力学性能;双掺1.5%大尺度钢纤维和0.5%中尺度钢纤维时RPC的性能最佳,其抗压强度、劈裂抗拉强度、抗弯强度和断裂能分别比单掺2.0%大尺度钢纤维时提高6.1%、33.3%、22.7%和30.4%;在三掺钢纤维基础上掺加占水泥质量0.10%的碳纳米管后,RPC的抗压强度、劈裂抗拉强度、抗弯强度和断裂能分别提高了8.4%、2.6%、4.4%和6.1%,这与碳纳米管的填充效应和桥接阻裂作用,以及各纤维间的牵制效应有关.另外,碳纳米管分散不均时会引起RPC局部应力集中,其分散效果对RPC的力学性能有显著影响.

The influence of multi-scale steel fiber combination and carbon nanotube on mechanical properties of reactive powder concrete(RPC)was investigated.Moreover,pore structure of RPC before and after adding carbon nanotube was also determined by means of mercury intrusion porosimetry(MIP).The results show that compared with macro-fiber,adding multi-scale steel fiber can improve the mechanical properties of RPC significantly.At an identical total dosage of steel fiber,the mechanical properties of RPC incorporating macro-fiber and meso-fiber decrease gradually with the increase of proportion of meso-fiber.The compressive strength,tensile splitting strength,bending strength and fracture energy of RPC are optimized by simultaneously addition of 1.5%macro-fiber and 0.5%meso-fiber to increase by 6.1%,33.3%,22.7%and 30.4%relative to that with the addition of 2.0%macro-fiber,respectively.In addition,adding 0.10%carbon nanotube can efficiently increase the compressive strength,tensile splitting strength,bending strength and fracture energy of RPC incorporating three types of steel fiber(i.e.macro-fiber,meso-fiber and micro-fiber),exhibiting the increments of 8.4%,2.6%,4.4%and 6.1%,resrespectively.This is mainly related to the filling effect and capacity for bridging cracks of carbon nanotube,and the snubbing effect between multi-scale fibers.Meanwhile,dispersion effect of carbon nanotube can significantly affect the mechanical properties of RPC.If carbon nanotube is not dispersed uniformly,local stress concentration will occur,thus resulting in a decrease in the mechanical properties of concrete.