改性材料及其掺量对超高性能混凝土力学性能的影响

Effects of modified materials and its contents on mechanical property of ultra-high performance concrete

【目的】优选不同掺量的改性材料,并分析改性后的UHPC抗压强度和破坏形态,制备更加经济型的超高性能混凝土(ultra-high performance concrete,UHPC)。【方法】选取钢渣微粉、河砂、粗骨料、钢纤维作为4种改性材料,设计四因素三水平正交试验,根据正交试验结果制备9种试件;通过力学性能实验,对比分析各试件的抗压强度,优选出改性材料最佳配方并分析UHPC的破坏形态。【结果】钢渣微粉、河砂、粗骨料和钢纤维的加入量(掺量)对试件抗压强度平均值影响的极差分别为7.60、7.57、7.77、0.84,粗骨料、钢渣微粉、河砂对UHPC的抗压强度的影响较大,钢纤维对UHPC抗压强度影响较小。由正交试验结果可知,当钢渣微粉、河砂、粗骨料的加入量分别为210、855、640 kg/m^(3),钢纤维的体积分数(掺量)为1.5%,养护龄期为28 d时,经改性的UHPC抗压强度最大,为134.4 MPa。改性后的UHPC受压破坏时不会瞬间炸裂,整体形态完整。【结论】钢渣微粉和粗骨料的添加能降低改性后的UHPC制造成本,经优化4种改性材料的掺量后UHPC的抗压强度降幅较小,但韧性增强,力学性能得到保障。

Objective Ultra-high performance concrete(UHPC)exhibits remarkable properties such as high compressive strength,high toughness,and excellent durability,making it with broad application prospects.Despite its outstanding features,the high cost of UHPC has promoted research into the addition of modified materials with a certain content.This approach can effectively reduce the cost under the premise of ensuring mechanical properties.By studying the influence of different contents of steel slag powder,river sand,coarse aggregate and steel fiber on the compressive strength of UHPC and analyzing the damaged form of modified UHPC,the optimum modified material formula is determined,and the purpose of producing UHPC with low cost and good mechanical properties is realized.Methods Steel slag powder,river sand,coarse aggregate and steel fiber were selected as four kinds of modified materials.The particle size of steel slag powder,river sand and coarse aggregate were analyzed,and the micromorphology of steel slag powder and silica fume were analyzed.Using four-factors and three-levels orthogonal tests,nine kinds of specimens were prepared and the curing ages of the specimens were set as 3,7 and 28 days,respectively.Moreover,the compressive strength tests of the specimen were carried out,focusing on the influences of the dosage and curing age of each modified material on the compressive strength.The optimum formula of modified material was determined by the range analysis method.The damaged form of UHPC was analyzed by destructive experiment,and the toughness of the modified specimen was verified.Results and Discussion The compressive strength range analysis shows that the compressive strength of UHPC first increases and then decreases with the increase of steel slag powder content when the addition of steel slag powder is 193,210,228 kg/m^(3) respectively.Similarly,varing the addition of river sand at 855,1045,1140 kg/m^(3) indicates a slowly decreasein compressive strength with the increase of river sand content.For coarse aggregate with the addition of 320,640,1280 kg/m^(3),the compressive strength of UHPC exhibits an intial increase followed by a subsequent decrease with the increase of coarse aggregate content.Conversely,the volume fraction of steel fiber at 1.5%,2.0%and 2.5%demonstrates a slight increase in the compressive strength with increasing steel fiber content.The range values of steel slag powder,river sand,coarse aggregate and steel fiber are 7.60,7.57,7.77 and 0.84,respectively.This indicates that coarse aggregate,steel slag powder and river sand have a greater influence on the compressive strength of UHPC,while steel fiber has less influence.The orthogonal test results show an optimal configuration for modified UHPC.Specifically,when the addition of steel slag powder,river sand and coarse aggregate is 210,855,640 kg/m^(3) respectively,with the volume fraction of steel fiber at 1.5%,and a curing age of 28 days,the compressive strength of the modified UHPC reaches 134.4 MPa.Importantly,the lateral binding force provided by the steel fiber within the UHPC enhances its structural integrity,avoiding instantaneous bursting under pressure,and maintaining an intact overall shape.Conclusion The addition of steel slag powder and coarse aggregate reduces the manufacturing cost of the modified UHPC.However,the reduction of compressive strength of UHPC is small after optimizing the content of four modified materials,but the toughness is enhanced and the mechanical properties are guaranteed.