Glass waste powder addition used as mitigator of concrete alkali-silica reaction

The recycled aggregates from demolition of concrete structures affected by alkali silica reaction as well as the potentially reactive natural aggregates are often a matter of great concern and fear in case of new structures construction. Thus, to encourage the recycling and use of some potential reactive aggregates under scientific basis, this paper presents an experimental study where suspected alkali-silica reactive recycled aggregates was used. The main goal of this study is evaluate the influence of waste glass powder addition as mitigator of the concrete expansive reaction. In a first phase, the level of expansibility of different aggregates was identified using accelerated tests in mortars bars, method ASTM C1260 and an adapted accelerated test on specimens of 40 x 40 x 160 mm. In a second phase, tests were performed on concrete mixtures, according to CMBT method, with 100% recycled reactive coarse aggregates and powder addition, such as the glass powder and metakaolin. The powder additions percentages were incorporated at 20%, 40% and 60% of cement weight. The results of mortars bars test showed opposite results according to the method applied, i.e. , the same aggregates considered as harmless by the adapted method are considered reactive by the ASTM method, if the same expansion limit of 0,10% for 16 days was adopted for both methods. Finally, the concrete results obtained with CMBT method showed that glass powder and metakaolin had a significant mitigation effect in alkali-aggregate reaction development