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Quantifying the freeze-thaw performance of air-entrained concrete using the time to reach critical saturation modelling approach
Cement & Concrete Composites ( IF 10.5 ) Pub Date : 2019-11-29 , DOI: 10.1016/j.cemconcomp.2019.103479
Mehdi Khanzadeh Moradllo , Chunyu Qiao , Rita Maria Ghantous , Myo Zaw , Hope Hall , M. Tyler Ley , W. Jason Weiss

Many State Highway Agencies have been working to develop performance-based specifications for concrete pavements and concrete bridge decks in freeze-thaw environments. A time to reach critical saturation (TTRCS) model has been proposed to estimate the freeze-thaw performance of concrete. This study evaluates the TTRCS model for thirty different concrete mixtures with varying w/c, air volumes, and quality of air void (size and spacing). Simple quality control test procedures are used to determine the input parameters for the TTRCS model. The estimated time to reach critical saturation is compared with the measured durability factor using ASTM C 666–15. Results indicate that 86% of the mixtures with air volume above 4.5% and a Sequential Air Method (SAM) Number below 0.30 have a normalized time to reach critical saturation of greater than 20, and a durability factor that is greater than 75%. The mixtures with a high range water reducer require a higher volume fraction of entrained air to satisfy the recommended limit for the durability factor. This appears to be due to an interaction between the high range water reducer and air entraining admixture which results in greater air void spacing (i.e., larger air voids). However, the addition of high range water reducer was also found to increase the time to reach critical saturation in the mixtures with a low w/c due to a refined pore structure with a reduction in the connectivity of the matrix pores. Reducing the w/c improves the freeze-thaw performance due to a reduction in the pore volume, connectivity, and absorption rate of the concrete. A relationship is developed to estimate the time to reach critical saturation based on SAM Number and apparent formation factor. In addition, a relationship is proposed to estimate the critical degree of saturation based on air void content and quality.



中文翻译:

使用达到临界饱和度建模时间的时间来量化引气混凝土的冻融性能

许多州高速公路局一直在努力为冻融环境中的混凝土路面和混凝土桥面板制定基于性能的规范。有人提出了达到临界饱和时间的模型以估计混凝土的冻融性能。这项研究针对具有不同w / c,风量和气隙质量(尺寸和间距)的30种不同混凝土混合物评估了TTRCS模型。简单的质量控制测试程序用于确定TTRCS模型的输入参数。使用ASTM C 666-15将达到临界饱和度的估计时间与测得的耐用性因子进行比较。结果表明,空气量高于4.5%且顺序空气法(SAM)值低于0.30的混合物中有86%的归一化时间达到了大于20的临界饱和度,耐久性系数大于75%。具有高范围减水剂的混合物需要更高体积的夹带空气,才能满足耐久性因素的建议极限。这似乎归因于高范围减水剂和夹带空气的混合物之间的相互作用,这导致更大的气隙间距(即,更大的气隙)。但是,还发现添加高范围的减水剂会增加w / c低的混合物达到临界饱和的时间,这是由于细化的孔结构降低了基体孔的连通性。降低w / c可以降低混凝土的孔体积,连通性和吸收率,从而提高冻融性能。建立了一种关系,以根据SAM编号和表观形成因子来估计达到临界饱和的时间。另外,提出了一种关系,以基于空隙含量和质量估算临界饱和度。

更新日期:2019-12-11
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