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 (ε g,fr ) and restrained swelling pressure ( P rs ). The gels were cast into disk‐shape molds and exposed to distilled water after curing. Each gel's ε g,fr was recorded over a period of 28 days, followed by measuring P rs , 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 ε g,fr . Increasing Ca/Si up to 0.23 drastically reduces ε g,fr ; higher Ca/Si has modest effect on free swelling. P rs increases by increasing calcium up to a pessimum Ca/Si level; P rs decreases for higher Ca/Si. The value of (Ca/Si) pess is related to the alkali content of the gel. P rs 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.