ABSTRACT
Abstract A large number of freeze-thaw-tests is known. Many of them claim to simulate natural conditions of freezing and thawing. The temperature shock test which is now established in several guidelines and draft European standards for concrete repairs is far away from real temperature changes in winter. But its results seem to be similar to those of well-known long-term tests. It uses a saturated sodium chloride solution at -15 °C and a water bath at +20 °C. The samples are alternately submerged in both liquids for 2 hours each with very quick changes. This simple principle needs special techniques. An automatically working equipment is described. Investigations and results are presented. The comparison with results achieved with the cube method according to CEN TC 51 drafts indicate sufficient reliability of the shock method for judging the freeze-thaw resistance of concrete with a considerable acceleration of the test. Keywords: Freeze-thaw resistance, test method, accelerated test
1 Introduction
Numerous methods for the assessment of the freeze-thaw resistance of concrete with or without impact of deicing agents are well-known. The tests consist mostly of temperature cycles within the range of +20 °C and -15...20 °C, each lasting 24 hours with respect to usual working hours. It is often claimed that these cycles simulate natural conditions. But long term measurements in structures have demonstrated that the real temperature range is much more limited and the rate of cooling or warming is much lower on site than it is in the tests [1]. So might be concluded that not the impact but the effect of freezing and thawing in the presence of salt or salt solutions is simulated. On that condition, even a temperature shock impact can be applied if the detrimental effect on concrete is similar to the one observed on site. One of these methods originally based on a RILEM proposal for testing the
thermal compatibility of polymer bearing products with concrete substrates will be described, with its principles, the technique and previous experiences. Considering the test results, the advantages and disadvantages will be discussed with regard to the suitability for testing conventional concrete.
