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 (epsilon(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 epsilon(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 epsilon(g,fr). Increasing Ca/Si up to 0.23 drastically reduces epsilon(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)(pes)s 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.