A wide range of waterproofing systems considered suitable by manufacturers for concrete bridge decks have been laid under experimentally controlled conditions on a concrete slab at the Transport and Road Research Laboratory. Their performance was monitored over a three year period. Many of the systems, including some of those with a British Board of Agreement Roads and Bridges approval certificate for use, were found to be unsuitable or ineffective. Severe damage was often caused during the laying of the base course due to penetration of aggregate into the membrane. The use of sand carpet asphalt to protect membranes from the effects of base course aggregate overcame this problem, but the interface bond between membrane and sand carpet was weaker than that for base course road surfacing materials. Where membranes were punctured or leaked, water transmission was much greater where there was poor bond between the concrete and the membrane. Resinous primers gave a better bond to the concrete than their bituminous counterparts. The results showed that the test programme current during the period of the trial for approval certification of waterproofing membranes is inadequate as it does not cover the full range of conditions to which membranes are subjected. Tests are required to cover the effect of hot aggregate, bond, moisture content of the deck and waterproofing integrity over the ambient and asphalt temperature range. This will necessitate the development of improved waterproofing systems.

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