Concrete Resistance to Freezing and Thawing Effects

Concrete durability is a capacity of concrete to resist the changes of its properties. Concrete structures should be designed and performed in the way that, under expected environmental conditions, their safety and usability hold over the structure´s lifetime with minimal repair and maintenance costs. Long-life concrete must be resistant to destruction when exposed to agressive environment like, among other things, the freezing effect with or without deicing salt. Direct testing methods in Croatia so far have not provided for timely information about the required concrete resistance to the freezing and thawing effects. The aim of this paper is the analysis of the air voids parameters in fresh concrete and the proving the concrete resistance to the freezing and thawing effects already in fresh concrete. Thirty nine (39) concrete mixtures have been prepared and all the concrete´s physical and mechanical properties have been tested. Mixtures are prepared with two cement types of air entraining admixtures out of which one is selected and used. The assessment of concrete resistance obtained i fresh concrete is compared with assessments obtained in hardened concrete. By means of an air pores analyzer, it is proved that it is possible to make necessary corrections of the concrete composition in the mixing stage and avoid additional costs of repair works. With a proper pre-selection of concrete components by the AVA method, a reliable perception of the resistance to freezing in fresh concrete is possible already during mixing. Also, checking by the microscopic method in hardened concrete has significantly reduced time necessary for the execution of preliminary testing by the alternating freezing and thawing cycles.