摘要
【目标】揭示高原低气压环境对引气混凝土孔隙结构特征的影响规律,进一步探明其对混凝土抗压强度与抗冻耐久性指数的劣化效应。【方法】分别在北京和甘南地区配置引气混凝土,对不同气压环境下引气混凝土的含气量、气孔结构参数、抗压强度及抗冻耐久性指数进行测试。【结果】低气压环境明显削弱了引气剂的引气能力及气泡稳定性,当气压由101 kPa降至64 kPa时,新拌混凝土含气量最大降幅约为17%,硬化后混凝土含气量最大降幅增至25%;低气压环境导致引气混凝土中气孔数量仅为常压时的25%~86%;不同直径气孔数量占比下降和上升幅度最大的孔分别为0~100μm的微孔和500~1000μm的大孔;大孔数量占比上升削弱了混凝土的力学性能,当硬化混凝土含气量为3%~5%时,低压环境下混凝土的抗压强度较常压环境下降3%~20%;微孔数量占比下降劣化了气孔结构,导致低压环境下混凝土的抗冻耐久性指数较常压下降约8%~26%;【结论】在低气压环境下进行抗冻混凝土含气量设计时,建议混凝土含气量设计值较常压环境提高约1.50%,以保障混凝土实际抗冻耐久性能达到设计要求。
[Objective]This study investigated the influence mechanism of plateau low atmospheric pressure on the air void structure of air-entrained concrete,thereby exploring the deteriorating effects on the compressive strength and frost resistance durability index of concrete.[Method]The air-entrained concrete was prepared in Beijing and Gannan Tibetan Autonomous Prefecture respectively.The tests were carried out in different pressure conditions on air contents,air void structure parameters,compressive strengths,and frost resistance durability index of air-entrained concrete.[Result]The low atmospheric pressure significantly impairs the air-entraining ability and bubble stability of air-entraining agents.When the atmospheric pressure drops from 101 kPa to 64 kPa,the maximum reduction in air content of fresh concrete is approximately 17%,and that of hardened concrete increases to 25%.Under low atmospheric pressure,the number of air voids in air-entrained concrete is only 25%-86%of that under normal atmospheric pressure.Among the air voids with different diameters,the proportion of micro-pores(0-100μm)shows the largest decrease,while that of macro-pores(500-1000μm)shows the largest increase.The increase in proportion of macro-pores weakens the mechanical properties of concrete.When the air content of hardened concrete ranges from 3%to 5%,the concrete compressive strength under low atmospheric pressure is approximately 3%-20%lower than that under normal atmospheric pressure.The decrease in proportion of micro-pores deteriorates the void structure,causing the concrete frost resistance durability index under low atmospheric pressure to be 8%-26%lower than that under normal atmospheric pressure.[Conclusion]When designing the air content of frost resistance concrete in low atmospheric pressure environment,it is advisable to increase the designed air content by approximately 1.50%compared with that in normal atmospheric pressure environment.It can ensure the concrete actual frost resistance performance meeting the specifications for design.
作者
李向阳
李雪峰
LI Xiangyang;LI Xuefeng(The Highway Development Center of Gansu Province,Lanzhou,Gansu 730030,China;Research Institute of Highway,Ministry of Transport,Beijing 100088,China)
出处
《公路交通科技》
北大核心
2025年第8期103-109,共7页
Journal of Highway and Transportation Research and Development
基金
中央级公益性科研院所基本科研业务费项目(2024-9006)
新疆维吾尔自治区科技重大专项(2020A03003-4)。
关键词
桥梁工程
引气混凝土
低气压环境
孔隙结构
抗冻耐久性指数
bridge engineering
air-entrained concrete
low atmospheric pressure
air void structure
frost resistance durability index
