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The alkali-silica reaction has been studied in depth due to the evolution in the knowledge of the expansive phenomenon. One of its most important aspects is the reaction rate of the aggregates. In Spain, at the early 90s of the 20th century, aggregates were considered almost non-reactive. However, the use of accelerated curing and other environmental factors revealed that there were potentially reactive siliceous aggregates. Nevertheless, there are several siliceous and limestone aggregates with siliceous inclusions that show reactivity over long period. In the present work, open porosity, expansion and petrography with quartz reactivity index have been determined, in 68 siliceous, limestone and dolomitic aggregates, from quarries located in areas with diagnostic reactivity. Based on these parameters and their interrelation, a classification method is proposed to detect slow-reacting aggregates., This research was funded by the CSIC (Intramural Projects PIE 201660E054 and PIE 202060E176).

Alkali¿silica reaction (ASR) is a swelling reaction that occurs in concrete structures over time between the reactive amorphous siliceous aggregate particles and the hydroxyl ions of the hardened concrete pore solution. The aim of this paper is to assess the effect of pozzolanic Portland cements on the alkali¿silica reaction (ASR) evaluated from two different points of view: (i) alkali-silica reaction (ASR) abatement and (ii) climatic change mitigation by clinker reduction, i.e., by depleting its emissions. Open porosity, SEM microscopy, compressive strength and ASR-expansion measurements were performed in mortars made with silica fume, siliceous coal fly ash, natural pozzolan and blast-furnace slag. The main contributions are as follows: (i) the higher the content of reactive silica in the pozzolanic material, the greater the ASR inhibition level; (ii) silica fume and coal fly ash are the best Portland cement constituents for ASR mitigation., This research was funded by the CSIC (Intramurales Projects PIE 201660E054 and PIE202060E176).

The increased use of industrial wastes and by-products to produce concretes and blended cements is a lever to achieve carbon neutrality. Furthermore, they could improve their durability. Some pozzolanic additions can minimize the alkali-silica reaction (ASR), which is a well-known deleterious process that occurs between some reactive aggregates and the alkaline pore solution found in mortars and concretes. This work quantifies the efficiency of four pozzolanic materials (natural pozzolan, P, siliceous coal fly ash, V, silica fume, D, and blast-furnace slag, S) assessed by means of compressive strength testing, open porosity, ASR-expansion measurements, and SEM microscopy. Accelerated expansion tests were performed in mortar bars with a cement/sand ratio of 1/2.25 and a water/cement ratio of 0.47, two reactive aggregates and a non-reactive one. The major contributions of this paper are: (i) The more aggregate reactivity is, the higher ASR mitigation level was found when additions were added and (ii) The best additions for ASR inhibition are silica fume and fly ash., This research was funded by the CSIC (Intramurales Projects PIE 201660E054 y PIE 202060E176).