Concrete test cylinders are usually prepared carelessly, mishandled and otherwise abused. This results in lower cylinder strengths. Can it be said that proper cylinder strengths can only be achieved by carefully following the prescribed standard methods of preparing and handling cylinders? In other words, do standard methods give the highest seven- and 28-day cy/inder strengths attainable?
Yes, it can be said that proper strengths can only be achieved on the job by following the prescribed methods. These give virtually the highest cylinder strengths attainable. Concrete test cylinders should be prepared, handled and tested in accordance with the methods described in ASTM C 31. Violations of the procedure almost inevitably result in lower cylinder strengths. Poor sampling of the concrete used to make the cylinder can produce a nonuniform cylinder which will be low in strength. Rodding or vibrating less than the specified amount may consolidate the concrete incompletely and cause low strength. Mixes with slumps of one inch or less should be consolidated by vibration as described, and not rodded. Rodding of such low slump mixes is likely to cause low strength results. Vibrating is optional for slumps of one to three inches but should not be used for higher slumps. Cylinders should be handled with care to avoid bumping and jarring on the job or in transit to the testing laboratory. They should be prevented from drying out and should not be stored at excessively low or high temperatures.