CFRP composites for swelling control of inorganic mortar subjected to alkali silica reactions

This paper presents the swelling mechanisms of mortar bars subjected to alkali-silica reactions when confined with carbon fiber reinforced polymer (CFRP) sheets. Alkali-silica reactions are a critical concern in concrete structures because they can degrade durability, leading to cracking, disintegration, and malfunctioning of elements. A standard test protocol (ASTM C1293) is employed to examine the expansions of the mortar which contains a variable amount of reactive aggregates (i.e., replacement ratios of regular sand with rhyolite powder ranging from 0% to 100% in 25% increments, intended to control the degree of alkali-silica reactions) and is immersed in water and sodium hydroxide solutions. The properties and behavior of the CFRP and conditioned bars are assessed using supplementary tests such as particle gradation, surface microscopy, tension, and bending. The distribution of the regular sand and rhyolite particles is comparable to each other at an average difference of 5.1%. The discrepancy in moisture-related adhesion between the cement paste and rhyolite leads to the local spalling of the mortar. Upon activation of the chemical reactions, amorphous silica gels form and cover the mortar surface. The volumetric expansions of the plain mortar and CFRP-confined cases are investigated (0.45% and 0.06% at 28 days, respectively), followed by a comparative assessment against the 0.2% limit of ASTM C1260. The replacement ratio affects the flexural capacity and energy dissipation of the plain and CFRP-confined mortar bars (e.g., 8.1% and 30.3% decreases in the capacity with and without CFRP, respectively). Chemo-mechanical modeling characterizes the reactivity of the test specimens and substantiates the evolution of the silica gels and the efficacy of CFRP in mitigating detrimental alkali-silica reactions.