EXPERIMENTAL STUDY ON THE FROST RESISTANCE DURABILITY OF CONCRETE IN HIGH ALTITUDE AND COLD REGIONS
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摘要: 高海拔寒冷地区具有海拔高、气温低、昼夜温差大等特点。在冻融循环作用下,高海拔寒冷地区混凝土结构容易发生损伤而影响建筑物使用年限,当损伤严重时甚至威胁建筑物的安全。为了研究高海拔寒冷地区混凝土的工作性能、力学性能、抗冻耐久性以及冻融损伤机理,在某高海拔寒冷地区桥梁施工项目制作了4种不同混凝土试件,开展了混凝土冻融循环试验,并对不同冻融循环次数下的高寒混凝土试件进行了核磁共振试验。结果表明:从宏观力学性能来看,高寒引气减水混凝土的抗冻耐久性表现最佳。同时,4种高寒混凝土试件的抗冻耐久性与混凝土内部的小孔(<0.01 μm)和中孔(0.01 μm~0.05 μm)所占比例密切相关,即高寒混凝土内部的小孔和中孔所占比例越大,混凝土抗冻耐久性越好。Abstract: The cold regions at high altitude have the characteristics of high altitude, low temperature and large temperature difference between day and night. Under the action of freeze-thaw cycle, the concrete structure is prone to damage in the high altitude and cold regions, which affects the service life of buildings and even threatens the safety of buildings when the damage is serious. To study the working performance, mechanical properties, frost resistance durability and freeze-thaw damage mechanism of concrete in the high altitude and cold regions, four kinds of concrete specimens were produced in a bridge construction project, and the freeze-thaw cycle tests were carried out. At the same time, the Nuclear Magnetic Resonance (NMR) tests of concrete under different freeze-thaw cycles were carried out. The results show that the alpine air-entraining and water-reducing concrete has the best frost resistance durability from the perspective of macroscopic mechanical properties. At the same time, the frost resistance durability of the four alpine concrete specimens is closely related to the proportion of mesopores (<0.01 μm) and micropores (0.01 μm-0.05 μm) inside the concrete, i.e., the proportion of small pores and mesopores in the alpine concrete. A larger proportion leads to a better frost resistance of concrete.
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表 1 高寒混凝土配合比与强度
Table 1. Mix ratio and strength of cold-resistant concrete
配合比 水泥/(kg/m3) 碎石/(kg/m3) 砂子/(kg/m3) 水/(kg/m3) 引气剂/(kg/m3) 减水剂/(kg/m3) 抗折强度/MPa 抗压强度/MPa 高寒普通混凝土(P) 458 1046 641 165 0.00 0.00 8.66 52.7 高寒减水混凝土(J) 458 1046 641 165 0.00 4.58 10.44 55.4 高寒引气混凝土(Y) 485 1032 633 160 0.05 0.00 8.18 51.9 高寒引气减水混凝土(YJ) 485 1032 633 160 0.04 4.23 8.93 54.1 表 2 高寒混凝土试件工况表
Table 2. Working conditions of cold-resistant concrete
冻融次数 高寒普通混凝土 高寒减水混凝土 高寒引气混凝土 高寒引气减水混凝土 0次冻融循环 P-1~P-3 J-1~J-3 Y-1~Y-3 YJ-1~YJ-3 25次冻融循环 P-4~P-6 J-4~J-6 Y-4~Y-6 YJ4~YJ-6 ··· ··· ··· ··· ··· 175次冻融循环 P-22~P-24 J-22~J-24 Y-22~Y-24 YJ-22~YJ-24 200次冻融循环 P-25~P-27 J-25~J-27 Y-25~Y-27 YJ-25~YJ-27 -
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