The effectiveness of expansion tests on slowly reactive aggregates

摘要

Cases of alkali-silica reaction were reported for the first time in Portugal in the 1990s, mainly associated with granitic aggregates used in large dams. A research project was developed aiming at the determination of the most effective laboratory test for the identification of the alkali reactivity of this type of aggregates. The laboratory tests followed the RILEM recommendations on Alkali-Silica Reaction, namely the petrographic method and the concrete prism tests at 38 ℃ and 60 ℃. Accelerated mortar bar tests were also performed. The results obtained show the importance of the variability of the rocks at the quarries' scale and the need to quantify the occurrence of microcrystalline quartz. It could be confirmed that the accelerated mortar bar test is ineffective for granitic aggregates. The concrete prism test at 60 ℃ proved to be more effective than at 38 °C to identify a larger number of slowly reactive granitic aggregates. The results are discussed according with two different criteria.