复合纳米材料对混凝土动态力学性能的影响

制备了掺量为0.2%(以水泥质量为基准)的纳米Fe₂O₃(NF)、复掺纳米Fe₂O₃和纳米CaCO₃ 2种纳米材料(NFC)以及复掺纳米Fe₂O₃、纳米CaCO₃和纳米SiO₂ 3种纳米材料(NFCS)的混凝土,之后采用直径100 mm分离式霍普金森压杆(SHPB)试验装置测试了养护龄期为28 d的3种混凝土在不同平均应变率等级下的动力特性并与普通混凝土(PC)进行对比研究。结果表明:准静态载荷下,复合纳米材料的掺入可有效调高混凝土的抗压强度;冲击载荷作用下,中低水平平均应变率时, NFC动态抗压强度最高, 80 s-1时NFC比PC高31.6%,高水平平均应变率下NF动态抗压强度具有优势,在125 s-1时, NF比PC高16%;NF在冲击载荷作用下峰值应变具有显著优势,具有良好的变形性能;以比能量吸收作为韧性评价指标,在平均应变率为75 s-1和125 s-1时, NF比PC增幅达到66.6%和75.7%。通过SEM照片分析,纳米Fe₂O₃颗粒增大了水泥石密实度,进而改善了NF的强度和韧性;由压汞试验分析,纳米CaCO₃颗粒在混凝土中,改善了水泥石孔隙结构。 

Effects of composite nanomaterials on dynamic mechanical properties of concretes

Concrete with nano-Fe₂O₃ (NF), double kinds of nanomaterials (nano-Fe₂O₃ and nano-CaCO₃, NFC), and three kinds of nanomaterials (nano-Fe₂O₃, nano-CaCO₃, nano-SiO₂, NFCS) all containing the addition of 2.0% (based on cement quality)were prepared, then the dynamic properties of three kinds of concrete were compared with the plain concrete (PC) under varied average strain rate levels by the 100 mm-diameter split Hopkinson pressure bar (SHPB) test device after a 28 d maintenance period. The results show that the addition of composite nanomaterials can effectively improve the compressive strength of concrete under quasi static load. Under impact load, NFC has the highest dynamic compressive strength at middle and low average strain rate, it is 31.6% higher than that of PC at 80 s^-1. Dynamic compressive strength of NF has an advantage at high level of average strain rate with 16% higher than that of PC at the average strain rate of 125 s^-1. Peak strain of NF has significant advantages under impact load, which verified good deformation performance; From the perspective of the evaluation index of specific energy absorption, NF increases by 66.6% and 75.7% than that of PC at the average strain rate of 75 s^-1and 125 s^-1. SEM photograph analysis shows that nano-Fe₂O₃ particles increases the compactness of cement stone, improves the strength and toughness of NF. Mercury injection test analysis show that nanoparticles CaCO₃ improve the pore structure of cement stone in concrete.