为了研究石膏矿渣水泥与活性骨料的膨胀反应,我們通过对試条长度变化的測定和显微鏡观察,均証明这种水泥不与活性骨料发生反应,外加含碱盐时情况也相同。外加碱时,則随着碱的增加,与活性骨料的反应也增加,但与硅酸盐水泥相比,碱含量相同时反应程度輕得多。經化学法測定,发現其原因在于石膏矿渣水泥浸出液的OH~-浓度比硅酸盐水泥小, In order to study the expansion reaction between gypsum slag cement and active aggregates, we determined that the cement does not react with the active aggregate by measuring the length of the test strips and observing the microscope. The conditions are also the same when external alkali salts are added. When alkali is added, the reaction with the active aggregate increases with the increase of the alkali, but the reaction is much lighter when the alkali content is the same as that of the Portland cement. According to the chemical method, the reason is found that the OH~- concentration of gypsum slag cement leachate is smaller than that of Portland cement.