Damage model of fresh concrete in sulphate environment

A model of damage to fresh concrete in a corrosive sulphate environment was formulated to investigate how and why the strength of corroded concrete changes over time. First, a corroded concrete block was divided into three regions: an expanded and dense region; a crack-development region; and a noncorroded region. Second, based on the thickness of the surface corrosion layer and the rate of loss of compressive strength of the corroding region, a computational model of the concrete blocks’ corrosion-resistance coefficient of compressive strength in a sulphate environment was generated. Third, experimental tests of the corrosion of concrete were conducted by immersing specimens in a corrosive medium for 270 d. A comparison of the experimental results with the computational formulae shows that the calculation results and test results are in good agreement. A parameter analysis reveals that the corrosion reaction plays a major role in the corrosion of fresh concrete containing ordinary Portland cement,but the diffusion of the corrosion medium plays a major role in the corrosion of concrete mixtures containing fly ash and sulphate-resistant cement. Fresh concrete with a high water-to-cement ratio shows high performance during the whole experiment process whereas fresh concrete with a low water-to-cement ratio shows poor performance during the late experiment period.     

甘肃变电钢构架腐蚀类型调查与分析

对甘肃省境内10所变电站钢构架腐蚀现状进行了现场调查。调查发现不同地理气候环境下变电钢构架的腐蚀程度及腐蚀特征差别较大,不能采用一种腐蚀模型对其进行描述。分析了不同环境因素对变电钢构架腐蚀的影响,并归纳总结了各影响因素与腐蚀类型及机理之间的关系,可为类似地理气候环境下变电钢构架耐久性的进一步研究及腐蚀防护提供参考。     

硫酸盐环境下混凝土抗压强度耐蚀系数研究

基于混凝土腐蚀层厚度及腐蚀区混凝土抗压强度损失率的概念,建立了硫酸盐环境下混凝土试块的蚀强模型.根据该模型推导出混凝土抗压强度耐蚀系数计算公式,同时进行了3组全浸泡混凝土的腐蚀试验,并根据试验结果对混凝土抗压强度耐蚀系数计算公式进行拟合和参数分析.结果表明：根据所建立的模型得到的混凝土抗压强度耐蚀系数计算结果与试验结果吻合较好;硫酸盐环境下混凝土可划分为裂缝发展区、膨胀密实区和未腐蚀区3个区域;综合性的腐蚀系数可以反映混凝土配合比与抗硫酸盐腐蚀性的关系,腐蚀系数越大,抗硫酸盐腐蚀性越差.根据所建立的模型和计算方法能够评估和预测硫酸盐环境下混凝土的抗腐蚀性能.     

我国城市停车库建设的现状与选型建议

回顾了我国城市停车库的发展历史,介绍了各类停车库的特点,重点论述了各类机械式立体停车库,指出机械式立体停车库具有节地、环保的优点,是我国城市化进程中停车设施的必然选择,并建议了城市停车库建设中适宜的型式。