骨料级配对超高性能混凝土强度及孔结构的影响

Effect of Aggregate Gradation on Strength and Pore Structure of UHPC

设计两种粒径区间的细骨料,研究骨料级配与骨料堆积密度、超高性能混凝土(UHPC)抗压强度的关系;利用压汞法(MIP)测定不同骨料级配的UHPC孔结构,基于热力学分形模型计算得到不同骨料级配的UHPC孔体积分形维数,研究孔体积分形维数与孔结构各项参数的关系,建立微观孔结构与宏观抗压强度模型。结果表明:0.16~1.25mm骨料与0.16~0.63mm骨料相比,在形成致密堆积时堆积密度更高,制备的UHPC抗压强度更高,7d与28d强度可达92.4MPa和116.8MPa,比同龄期抗压强度分别提升5.96%与2.64%;孔体积分形维数反映孔结构不规则程度,其与孔结构各项参数的相关系数均大于0.77,孔结构随分形维数的增大而趋于复杂;分形维数与抗压强度显著相关,相关系数可达0.8854,孔结构越复杂,抗压强度越高。

Two kinds of fine aggregate with different particle sizes are designed,and the rela-tionship between aggregate gradation,packing density and compressive strength of UHPC are studied.The pore structure of UHPC with different aggregate gradation was tested by mercury intrusion porosimetry(MIP),and the pore volume fractal dimension of UHPC with different aggregate gradation was calculated based on thermodynamic fractal model.The relationship be-tween pore volume fractal dimension and various parameters of pore structure was studied,and the micro pore structure and macro compressive strength model were established.The results show that 0.16~1.25mm aggregate has higher packing density when forming densest packing compared with 0.16~0.63mm aggregate,so the compressive strength of UHPC prepared by 0.16~0.63mm aggregate is higher,the strength of 7d and 28d can reach 92.4MPa and 116.8MPa,which is increased by 5.96%and 2.64%respectively compared with that of UH-PC prepared by 0.16~0.63mm.The pore volume fractal dimension can reflect the irregularity of pore structure,and its correlation coefficient with various parameters of pore structure is greater than 0.77.The pore structure tends to be complex with the increase of fractal dimen-sion.The fractal dimension is significantly correlated with the compressive strength,and the correlation coefficient can reach 0.8854,when the pore structure is more complex,the com-pressive strength is higher.