5.8 : Testing Water Quality

When the quality of water for concrete preparation is uncertain, its impact on the setting time of cement and compressive strength of mortar is assessed by comparison with de-ionized or distilled water benchmarks. American Society for Testing and Materials (ASTM) C1602 requires the setting times to be within 90 minutes of the control, British Standard (BS) 3146:1980 allows a 30-minute variance in the initial setting, while British Standards European Norm (BS EN) 1008 specifies initial setting time must be not less than 1 hour and final setting time less than 12 hours, within a 25 percent variability from the results with distilled water. Mortar cubes made with test water must achieve at least 90 percent of the compressive strength of those with distilled water.

Testing for impurities, such as chlorides, sulfates, total solids, alkalis, etc, is critical, as concentrations must not exceed established limits to ensure concrete quality. When seawater is utilized, the concrete's long-term compressive strength must not be over 15 percent lower than that of freshwater-prepared concrete. Moreover, performance tests simulating natural wetting and drying are employed to check for potential staining, a necessary step to verify the water's suitability for curing without compromising the concrete's appearance.