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

(1)ASTM C 666程序A检验的粗集料含量很低的混凝土的抗冻性和抗冻性并不是单靠混凝土配合比的提高而提高的。但随着水灰比、含气量等混凝土配合比的提高，ASTM C672混凝土的抗结垢性能有了很大的提高。这些结果的差异可能是由于冻融劣化机理不同所致。(2)粗集料的孔结构特征对混凝土的抗冻性有很大影响。此外，粗骨料的孔结构及其最大尺寸对混凝土的抗结垢性能也有影响。(3)粗骨料的最大尺寸对混凝土的抗结垢性能也有影响。(4)不能仅从粗骨料的密度和吸水率来估计混凝土冻害和除冰盐垢破坏的风险。提出了评价混凝土强度和渗透性的具体试验方法，并研究了评价冻害破坏程度和深度的方法。(6)从结构设计、混凝土配合比、施工等方面提出了预防冻害的措施。

(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.