Alkali-silica reaction: understanding the phenomenon

Abstract

The alkali-silica reaction in cementitious composites occurs through the chemical association of the solution contained in the matrix pores, which is strongly basic and rich in alkalis, and the reactive phases of some aggregates. For the process to begin, high relative humidity and a high concentration of total alkalis are required. The degradations resulting from this reaction involve expansion, cracking, exudation and decreased mechanical performance of the structure, which can cause it to break depending on the magnitude of the phenomenon. Understanding the reaction development process is necessary to propose measures that can effectively extinguish or mitigate the occurrence. One of the measures widely studied is the incorporation of supplementary cementitious materials in concrete. In Brazil, technical regulations already exist that recommend the use of these cementitious materials. The Northeast region of the country is a major producer of fly ash and granulated blast furnace slag, but not all of this material is destined for other industries. The article in question is a compendium of technical information from relevant research developed about alkali-silica reaction. His contribution is in the didactic approach that allows the understanding of students in the engineering area and professionals who do not have the expertise in the subject in order to stimulate future research on the use of supplementary cementitious materials in Northeast Brazil, mainly.

Durability Behavior of Mortars Containing Perlite Tailings: Alkali–Silicate Reaction Viewpoint

“…Such SiO 2 and Al 2 O 3 contents plus values of alkaline equivalents (Na 2 O eq ) greater than 5% can trigger characteristic expansions of alkali-aggregate reactions (Table 2). The amorphous alkaline gel is the main product of such reactions and has high water absorption, which can cause expansion and consequent cracking of the cementitious materials [33][34][35]. Table 2 presents the chemical composition of the PP and CP tailings used in this research.…”

Improving Concrete Infrastructure Projects Conditions by Mitigating Alkali-Silica Reactivity of Fine Aggregates

“…Exact gel composition varies; however, it will always contain alkali, silica, calcium, and water [4]. Aggregates with large surface area for reaction, poor crystalline, with many lattice defects are more susceptible to ASR reaction [5,6]. ASR white expansive gel, shown in Figure 3, results in cracking once the resulting tensile stresses exceed the hardened concrete tensile strength.…”

Improving Concrete Infrastructure Project Conditions by Mitigating Alkali–Silica Reactivity of Fine Aggregates

“…The exact gel composition varies; however, it always contains alkali, silica, calcium, and water [4]. Aggregates with a large surface area for reaction, poor crystalline structure, and many lattice defects are more susceptible to ASR reactions [5,6]. White expansive gel that forms due to ASR, shown in Figure 2, results in cracking once the resulting tensile stresses exceed the hardened concrete tensile strength.…”