Highways Agency (HA) requirements relating to bridge deck waterproofing are contained in Departmental Standard BD 47/99. Waterproofing systems that have satisfied the requirements of the certification tests that are specified in the Standard are considered suitable for use on bridge decks where the concrete age is 28 days or more. To determine if waterproofing systems can perform satisfactorily when applied to younger concrete, a series of tests was carried out on the four waterproofing systems that are currently registered by the BBA and have Roads and Bridges Agrément Certificates, using the ‘standard’ primers specified in the Certificates, and a system approved for use in Germany. The systems were applied to concrete slabs manufactured from four mixtures aged from 3 to 28 days that had been subjected to different curing regimes. The slabs were waterproofed by the suppliers of the systems after they were surface dried in accordance with normal site practice, as deemed necessary by the suppliers. The day after the application of the systems, the slabs were overlaid with hot sand to simulate the high temperatures encountered during surfacing. Observations were made for blisters and tensile adhesion tests were carried out at -10oC, 23oC and 40oC from 28 days after waterproofing. It was concluded that the performance of waterproofing systems on bridges should not be adversely affected by application to concrete aged 7 days or more, provided they are applied in the same way as during the tests. In particular, the time between surface drying and the application of the primer should be as short as possible so that any moisture that may migrate from the bulk of the concrete material back to the surface is minimal. The findings from these tests were consistent with other research.

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