Can anything be done, short of repair, to reduce leakage through construction joints in swimming pools?
It has been found that it helps not to leave a pool drained for any significant length of time, and if possible to keep it warm while it is drained. The Scottish Laboratory of the Building Research Establishment (Great Britain) has investigated joint movements in three indoor pools in the Glasgow area. The pools were of cast-inplace concrete with construction joints not designed to accommodate movement, but one of the pools had two one-inch-wide control joints designed for movement in both the floor and walls and filled with bitumenimpregnated cork. Joint movements were measured before, during and after filling and emptying and also at yearly intervals. (Some measurements were made inside, under water, by technicians equipped with breathing apparatus and flippers.) The largest movements occurred across movement joints when the pool was shut down. For example, a movement of 0.055 inch was measured over a period of eight days during one shut-down period. This was much greater than the movement arising from drying shirnkage or creep, which was less than 0.024 inch over a period of two years. During shut-down periods there was a loss in temperature of 25 degrees F or more when the pool was emptied which was responsible for the movement. This influence of temperature changes has not been fully appreciated by pool managers; the temperature of indoor pools can easily be controlled during shutdown periods. Movements in construction joints not designed to permit any movement can be up to 0.006 inch, which might cause leakage through poorly designed or constructed joints. Movements in both construction and control joints in the Glasgow pools were ascribed entirely to the thermal contraction and expansion of the concrete shell and not to loading or other causes.