ABSTRACT

Abstract Wet freeze/thaw testing means that the concrete is in continuous contact with liquid during freeze/thaw. This is by far the most common way of frost testing concrete. The behaviour of concrete in two types of wet freeze/thaw tests: slow deicer salt tests and rapid freeze/thaw tests was investigated. 12 concretes varying from normal to high strength qualities were invesigated: I - slabs with 3 % NaCl exposed to slow cycles (SS 13 72 44) II - beams in water exposed to rapid cycles (ASTM C666 procedure A) lH - slabs with varying cooling rates to "bridge the gap" between slow and rapid cycles. In all tests measurements were made of surface scaling, internal cracking and liquid uptake during freeze/thaw. The results showed that damage often is related to a "pumping effect", which is an accelerated absorption caused by wet freeze/thaw. Also evaporable water and calorimetric ice formation increased due to wet freeze/thaw. Frost/salt scaring was amplified by reduced cooling rate whereas internal cracking was amplified by increased cooling rate. This observation corresponds to less internal cracking in the slow slab test compared to the rapid beam test. Clearly different mechanisms of deterioration are mobilized in slow and fast cycles. One wet freeze/thaw test method may rank resistance against wet freeze/thaw of a series of concretes, but it cannot predict service life of structures exposed to different frost and moisture conditions. Keywords: durability, freeze/thaw, test methods, deicer salt scaling, cracking, absorption, ice formation, mechanisms, material ranking, service life prediction

1 Introduction

The choice of appropriate test method is important for assessing frost durability of concrete according to the actual exposure conditions. In the Nordic countries the main frost durability problem today is considered to be surface scaling due to the increased use of deicer salts. However, also frost problems connected to freezing without deicing Frost Resistance of Concrete, edited by M.J. Setzer and R. Auberg. Published in 1997 by E & FN Spon, 2-6 Boundary Row, London SE1 8HN, UK. ISBN: 0 419 22900 0.