Study of ASR in concrete with recycled aggregates: Influence of aggregate reactivity potential and cement type

A study into the alkali-silica reactivity of recycled concrete aggregates and the role of the extent of damage in the source structures: Evaluation, accelerated testing, and preventive measures

“…The importance of taking the RCA absorption into consideration when running the AMBT was also reported in other research work [8]. In some cases, the AMBT underestimated the expansion compared to CPT [6]. The Concrete Microbar test (CMBT) [28] was used to evaluate the reactivity of aggregate [29,30,31].…”

“…The original aggregate used in the demolished structure has a major impact on the RCA usability, and different precautions may need to be taken. For instance, an RCA produced from a structure that has suffered alkali-silica reaction (ASR) may continue to cause expansion if used in a new structure without preventive measures [1][2][3][4][5][6][7][8][9]. In reality, more than one deterioration mechanism is likely co-occurring.…”

“…RCA produced from concrete suffering ASR was found to cause significant expansion when used as aggregate in lab-prepared concrete prisms [1][2][3][4][5][6][7][8][9]. The expansion of concrete prisms with a natural reactive limestone (Spratt) from Ottawa, Ontario, was slightly lower than new concrete prisms made with RCA containing the same reactive aggregate [2].…”

“…Other studies [3,4] showed the opposite trend, with RCA producing less expansion than the natural aggregate. The reactive RCA required higher dosages of SCMs -compared to those required by the natural stone -to mitigate the expansion [2,6,[20][21][22]. Using the reactive RCA as partial replacement of the coarse aggregate in concrete was found to reduce the expansion [4,6,20] and require lower levels of mitigation, compared to using the RCA as a total replacement of the coarse aggregate [20].…”

“…The reactive RCA required higher dosages of SCMs -compared to those required by the natural stone -to mitigate the expansion [2,6,[20][21][22]. Using the reactive RCA as partial replacement of the coarse aggregate in concrete was found to reduce the expansion [4,6,20] and require lower levels of mitigation, compared to using the RCA as a total replacement of the coarse aggregate [20]. Although high levels of SCM -including ternary blends of silica fume and fly ash -were necessary to reduce the expansion in Spratt-RCA below the 0.040% limit at two years [2,20], this may not be the case for other types of RCA.…”