British Standard and RILEM water absorption tests: A critical evaluation

British Standard and RILEM capillary suction rate and water absorption test s used for clay bricks, stones and pre-cast concrete products are criticall y examined. Experimental data are reported comparing the initial rate of su ction with the sorptivity, an analytically based method of measuring capill ary suction rate. Experimental work is also reported comparing water conten ts attained as a result of vacuum saturation absorption and the British Sta ndard 5 h boiling test. Results of 24 h and 30 min immersion tests are also reported. It is concluded that the initial rate of suction test is fundamentally flaw ed and may produce misleading results because of its use of only a single p oint measurement. It is further concluded that vacuum saturation provides t he most accurate measurement of water absorption, and therefore porosity. T he 5 h boiling test generally produces results significantly below those ob tained by vacuum saturation with samples attaining approximately 90% of vac uum saturation. Immersion tests, used to provide comparative data on the ra tes of absorption of different materials, can only be valid if the specimen s have identical dimensions.