冲击荷载下免蒸养活性粉末混凝土分形特征研究

应用?80 mm分离式霍普金森压杆系统(SHPB)得到了免蒸养活性粉末混凝土(RPC)在6组冲击气压(0.5 MPa、0.6 MPa、0.7 MPa、0.8 MPa、1.0 MPa、1.1 MPa)下的峰值强度和吸能值,通过筛分试验统计了相应应变率范围(约90 s-1~290 s-1)内破碎产物中不同粒径颗粒的质量分布特征;采用分形维数对试件的破碎程度进行表征,探究了峰值强度和吸能值随分形维数的变化规律,并与其他水泥基材料进行了对比。结果表明:免蒸养RPC破碎产物的平均粒径随应变率增加而线性递减,随着冲击气压的增加,粗颗粒碎片逐渐转化为细颗粒碎片,中等颗粒碎片的质量没有显著变化;分形维数与冲击速度和应变率间存在指数性关系,峰值应力与吸能值随分形维数的增大而增长,通过对比发现免蒸养RPC的抗破碎能力优于普通混凝土和钢纤维混凝土。通过定量分析破碎分形特征与力学性能之间的关系可以对材料进行更全面的评估。

EXPERIMENTAL STUDY ON FRACTAL CHARACTERISTICS OF STEAM FREE REACTIVE POWDER CONCRETE UNDER IMPACT LOAD

The peak strength and energy absorption of steam free reactive powder concrete(RPC) under 6 air pressures(0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 1.0 MPa, 1.1 MPa) are obtained by 80 mm split Hopkinson pressure bar(SHPB) test system. The mass distribution characteristics of fragments corresponding to strain rates ranging from nearly 90 s-1-290 s-1 are analyzed by sieving test. The fractal dimension is used to characterize the fragmentation degree of specimens, and then the variation rule of peak strength and the energy absorption value with the fractal dimension are also explored and compared with other existing cementitious materials. The experimental results indicate that the average particle size of fragments decreases linearly with the increase of strain rate, the coarse particles gradually change into the fine particles while the mass of the medium particles do not change significantly. There exists an exponential relationship between the fractal dimension and the impact speed as well as strain rates. The peak stress and energy absorption value increase with the fractal dimension. The comparison shows that the crushing resistance capacity of steam free RPC is better than that of ordinary concrete and steel fiber reinforced concrete. The quantitative analysis of the relationship between fractal characteristics and mechanical properties, helps to gain more comprehensive evaluation of the investigated material.