Testing natural sands for alkali reactivity with the ASTM C1260 mortar-bar expansion method

The effect of different portland cements on the alkali expansivity of five Italian natural sands of known field performance was investigated using the ASTM C1260 mortar-bar expansion method. The alkali reactivity of these sands was also evaluated according to the petrographic examination, infrared spectroscopy technique, ASTM C227 expansion method, ASTM C289 and AFNOR P18-589 chemical tests. The expansivity of the sands in the ASTM C1260 test is significantly affected by both the native alkali content and the specific surface area of the portland cement while it is virtually unaffected by its mineralogical composition. For all the sands there is good agreement between the diagnoses of the ASTM C1260 and the other test methods, except ASTM C227, only when a portland cement with a Blaine surface area of 500 m2/kg and a native alkali content of 1.13-1.15% Na2Oeq is used in the ASTM C1260 test.