Quantifying the swelling properties of alkali‐silica reaction (ASR) gels as a function of their composition

Synthetic alkali‐silica reaction (ASR) gels were produced and tested to investigate the effects of chemical composition (Ca/Si, Na/Si, and K/Si atomic ratios) on the gels’ free swelling strain (εg,fr) and restrained swelling pressure (Prs). The gels were cast into disk‐shape molds and exposed to distilled water after curing. Each gel's εg,fr was recorded over a period of 28 days, followed by measuring Prs, defined as the pressure required to fully reverse and eliminate the gel's free swelling under a drained configuration. Regression models were developed linking gels compositions to their swelling properties. The outcomes show that Na/Si and K/Si monotonically increase εg,fr. Increasing Ca/Si up to 0.23 drastically reduces εg,fr; higher Ca/Si has modest effect on free swelling. Prs increases by increasing calcium up to a pessimum Ca/Si level; Prs decreases for higher Ca/Si. The value of (Ca/Si)pess is related to the alkali content of the gel. Prs also increases by increasing the gel's alkali content, while a (Na/Si)pess exists in the range 0.85‐0.95. These observations are linked with the roles of alkalis and calcium in modifying the silica gel network.