Assessment of additional ASR damage resulting from residual expansion tests using the DRI and SDT test methods

Currently, ASR damage evaluation of concrete road infrastructure can be done following FHWA protocol (Fournier et al., 2010) [1]. The current level of ASR damage (diagnosis) is evaluated using the Damage Rating Index (DRI) and the Stiffness Damage Test (SDT), and future potential of damage (prognosis) is assessed using residual expansion tests, in humid air (> 95 % RH and T = 38 ± 3 °C) and alkaline solution (NaOH 1 N, 38 ± 3 °C). While accelerated expansion tests on cores have been used for decades, they provide only limited insights into ASR severity, without providing information on the ASR damage mechanisms, nor allowing extrapolation to the structural level. The aim was to identify correlations between pre- and post-expansion test results and additional expansion generated by assessing the actual extent and mechanisms of extra ASR damage caused by these tests. Results of the expansion tests in humid air were inconclusive, making the test procedure questionable. On the other hand, residual expansion tests in alkaline solution proved to be more relevant for assessing potential future damage to concrete. No new damage mechanism related to the added alkalis could be identified. The results indicated a comparable progression of ASR damage between the NaOH solution and in situ conditions. A cracking pattern in concrete at high expansion levels due to ASR was identified based on petrographic examination of test specimens following residual expansion testing in 1 N NaOH solution. • We question the applicability of expansion tests in humid air for ASR prognosis. • We show that expansion tests in alkaline solution are relevant for ASR prognosis. • We find no new damage mechanism related to the added alkalis in NaOH 1 N solution. • We find comparable ASR damage progression for NaOH solution and in situ conditions. • We propose a cracking pattern due to ASR after testing in 1 N NaOH solution.