冻融作用下风积沙浮石混凝土孔结构分形特征

Fractal Characteristics of Pore Structure of Aeolian Sand Pumice Concrete Subjected to Freeze-thaw Cycles

利用天然浮石作为粗骨料,以沙漠风积沙等质量替代部分河砂作为细骨料,配制风积沙浮石混凝土并对其进行抗冻耐久性试验。借助核磁共振技术对冻融循环作用下不同风积沙替代率的浮石混凝土孔结构进行测试,并揭示冻融循环作用下风积沙浮石混凝土孔结构与分形维数间关系。结果表明:风积沙替代率低于40%对浮石混凝土抗冻性影响不大,但风积沙替代率为60%的浮石混凝土抗冻性不满足设计要求;风积沙浮石混凝土中大毛细孔(100 nm<r≤1000 nm)占比多可增强其抗冻性,而有害孔(r>1000 nm)占比多会削弱其抗冻性;分形维数D_(max)变化可反映混凝土微毛细孔(r≤100 nm)和有害孔(r>1000 nm)占比变化。该研究可以为风积沙浮石混凝土在寒冷地区土木与水利工程中的应用提供理论支撑。

Natural pumice stone was used as coarse aggregate,and part of river sand was replaced by desert aeolian sand as fine aggregate.Aeolian sand pumice concrete was prepared and tested for frost resistance and durability.With the help of nuclear magnetic resonance,the pore structure of pumice concrete with different replacement rates of aeolian sand under the action of freeze-thaw cycles was tested,and the relations between the pore structure of aeolian sand pumice concrete under the action of freeze-thaw cycles and the fractal dimension was revealed.The results showed that:the replacement rate of aeolian sand lower than 40%had little effect on the frost resistance of pumice concrete,but the frost resistance of pumice concrete with the replacement rate of aeolian sand 60%did not meet the design requirements;a greater proportion of large pores in the aeolian sand pumice concrete(100 nm<r≤1000 nm)could increase its frost resistance,while a greater proportion of harmful pores(r>1000 nm)could weaken its frost resistance;the change of fractal dimension D_(max)could reflect the change in the proportion micropores(r≤100 nm)and harmful pores(r>1000 nm)of concrete.The research could provide theoretical support for the applications of aeolian sand pumice concrete in civil and water conservancy projects in cold regions.