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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).

Ternary Portland cements composed of coarse silica fume (SF), limestone (LS), and Portland cement (PC) can afford some environmental advantages by reducing the clinker content in Portland cements. These cements will help to reduce the clinker factor target from 0.78 to 0.60 by 2050 with the aim to be climate neutral. Silica fume (SF) possesses pozzolanic properties that enhance mechanical strength and durability. By contrast, limestone powder has three main outcomes, i.e., filler, dilution, and chemical effects. The first reduces porosity and refines the microstructure of mortars and concretes. The second decreases the amount of hydration products and increases the porosity; the third one promotes the appearance of carboaluminates and reduces porosity. This paper covers the mechanical properties of Portland cement-limestone-coarse silica fume ternary cements, and its synergetic mechanism. Compressive and flexural strength of mortar at 2, 7, 14 and 28 days was performed. Coarse silica fume has a minor contribution on the nucleation effect compared to ground limestone at early ages. The nucleation and filler effects, at early ages, are less pronounced in coarse and very fine limestone powder. The highest compressive strength at 28 days is reached with the lowest content of coarse silica fume (3%). Mortar mixes made with a high level of limestone presented a delay in the compressive strength development.

Organic repair products for concrete can be exposed to accidental incidents, like fire. The increase of temperature produces a modification in some of their properties. In general, these types of repair products have organic fibers to increase their tixotropic properties, but they are more sensible to the high temperature than the Portland cement or aggregates. In order to analyze the behavior of organic repair mortars with temperature three types of repair mortars are studied. These repair products have the organic components composed by acetate fiber of polyvinyl like Vinyl Acetate Acrylate (VAA), Copolymer of Vinyl Acetate Vinyl Versatate (VeoVA) and Acrylic polymers fibres. The repair products are tested increasing the temperature from 1.7ºC /min until 200ºC, 400ºC or 600ºC respectively during 20 minutes. After that, the samples are cooled in four different cooling conditions two of them slow and two others fast, and with and without oxygen. These conditions are used in order to simulate the different conditions that can occur during the cooling after fire. After the testing the visual aspect, the color and brightness and the open porosity is analyzed in each condition of test. In this work the relationship between the temperature of exposition, the cooling conditions and the change in some physical properties are studied.