TESTS ON WATER FOR CONCRETE
One way to determine if water is suitable for mixing with cement is by comparing its effects on the setting time and strength of mortar cubes to those of de-ionized or distilled water. The water being tested should have an initial setting time of no less than one hour and be within 25% of the result obtained using distilled water. The final setting time should not exceed 12 hours and also be within 25% of the result with distilled water. The mean strength of the mortar cubes using the tested water should be at least 90% of that obtained with distilled water. These requirements can be compared with the standards outlined in BS 3146:1980, which permits a tolerance of 30 minutes for the initial setting time and recommends a tolerance of 10% for strength. Meanwhile, the requirements of ASTM C 1602-06 state that the setting time can be from one hour early to one hour 30 minutes later, and the strength must be at least 90%.
The determination of whether impurities in the curing water will cause staining cannot be made solely through chemical analysis. Instead, it is necessary to conduct a performance test that simulates wetting and evaporation. This test will provide a more accurate assessment of whether staining is likely to occur.
Chemical analysis can be useful in identifying the presence of impurities in the curing water, but it cannot determine the impact that these impurities will have on the final product. Other factors, such as the specific materials being used and the conditions under which they are being cured, can also play a role in determining whether staining will occur.
To ensure that staining does not occur, it is therefore important to conduct a performance test that specifically simulates the wetting and evaporation processes that will occur during curing. This test will provide a more comprehensive understanding of how the impurities in the curing water will interact with the materials being used, and will allow for any necessary adjustments to be made to prevent staining from occurring.