Reply to the discussion by C. Shi of the paper “Laboratory assessment of alkali contribution by aggregates to concrete and application to concrete structures affected by alkali–silica reactivity”

Na2O, K2O, SiO2 and Al2O3 release from potassic and calcic–sodic feldspars into alkaline solutions

“…According to some authors, the process of alkali release into the concrete pore solution may be linked to the ion exchange between the solution and the minerals. Others, however, suggest that alkali contribution occurs by hydrolysis or dissolution of the minerals contributing even alumina and silica to the concrete pore solution [2,[4][5][6][7][8][35][36][37].…”

“…Although there are different criteria for the characteristics that the solutions to test alkali release from aggregates [1][2][3][6][7][8][27][28][29][30][31] should have, it was decided to use a NaOH solution since it is employed both in the chemical test method [19] and in the mortar bar accelerated test method [32] to assess aggregate reactivity.…”

“…Predicting the potential alkali supply from different minerals under conditions similar to those of concrete by controlled laboratory tests has aroused great interest and is a problem that has been dealt with by a large number of researchers. Some of the most recent papers are those by Bérubé et al [1][2][3], Constantiner and Diamond [4], Leemann and Holzer [5], Lu et al [6], Shi [7] and Wang et al [8,9], although this subject has been under study for 50 years.…”

Effects of Soak Solution Type on Alkali Release from Volcanic Aggre-gates − Is Alkali Release Really Responsible for Accelerating ASR Expansion? −

“…These results emphasize that measuring only the amount of alkalis in the solution is insufficient when trying to determine the relationship between the amount of alkalis released and the potential risk of long-term ASR expansion. Bérubé et al (2004aBérubé et al ( , 2004b argued that there is competition between the consumption of alkalis via silica dissolution and the supply of alkalis being released from the aggregate. In fact, it was observed in these experiments that the amount of dissolved silica was higher than that of the alkalis released by one to two orders of magnitude.…”

“…Following a publication by Bérubé et al (2002), Tang (2004) and Shi (2004) raised a discussion regarding whether or not alkalis released from aggregates can increase hydroxide ion concentration and thus the pH of the pore solution. Bérubé et al (2004aBérubé et al ( , 2004b argued that this was possible, but did not measure hydroxide ion concentration or pH. They believed that the underlying mechanism was the precipitation of the reaction in the presence of lime.…”