Influence of Coarse Aggregates on Frost Resistance of concrete from the view point of Scaling Damage

(1) ASTM C 666程序A检验的极劣质粗集料混凝土的抗冻融性能并不能仅仅通过改善混凝土配合比来提高。然而，通过改善水灰比和空气含量等混凝土配合比，ASTM C 672测试的抗结垢性得到了很大的提高。推测这些结果的差异可能是由于冻融变质的机制不同造成的。(2)粗集料的孔隙结构特性对混凝土的抗冻性能有很大影响。此外，粗集料的孔隙结构不仅影响混凝土的抗垢性能，而且影响其最大粒径。(3)粗集料的最大粒径对抗结垢性能也有影响。(4)不能仅从粗集料的密度和吸水率来评价混凝土的冻损和除冰盐结垢风险。具体的措施和基于混凝土冻损机理的粗集料质量评价方法必须进行详细的研究。(5)提出了评估混凝土强度和渗透性的具体测试方法，并对其方法进行了检验，以评估冻害劣化的程度和深度。(6)从结构设计、混凝土配合比和施工等方面提出了防止冻害的措施。

(1)The freezing and thawing resistance of concrete with very inferior coarse aggregates examined by ASTM C 666 procedure A was not improved solely by the improvement of concrete mixture proportions. However, the scaling resistance examined by ASTM C 672 was greatly improved by the improvement of concrete mixture proportions such as water cement ratio and air content. The difference of these results was guessed possibly due to the different mechanism of freezing and thawing deterioration.(2)The character of pore structures in coarse aggregates had great role to the frost resistance of concrete. In additon, not only pore structures in coarse aggregate, but also its maximum size, were influenced on the scaling resistance of concrete.(3)The maximum size of coarse aggregate also influenced on the scaling resistance.(4)The risks of frost damage and deicer salt scaling damage of concrete could not be estimated solely from density and the water absorption of coarse aggregates. The measures to be specified and the method for estimation of coarse aggregates quality based on mechanism of frost deterioration of concrete must be investigated in detail.(5)Specific testing methods to assess the strength and permeability of concrete were proposed, and their methods were also examined to evaluate the degree and the depth of deterioration caused by frost damage.(6)Measures for the prevention of the frost damage were proposed from the aspect of the design of structure, the mixing of concrete and the execution of work.