WATERPROOFING OF CONCRETE BRIDGE DECKS SPECIFICATION PROVISIONS AND QUALITY ISSUES

摘要

The use of waterproofing membranes to enhance the durability performance of concrete bridge decks has been steadily increasing over the past 20 years. Waterproofing membranes are used both as part of bridge deck rehabilitation and as part of new construction, to provide an effective additional line of defence against premature deterioration and corrosion. Concrete decks on older bridges may be characterised by carbonated and permeable concrete of lower compressive strengths (15 MPa to 30 MPa), and cracking which allow water penetration resulting in spalling of concrete due to corrosion of steel reinforcement. Concrete decks on newer structures may suffer from shrinkage cracking and cracking due to restraint movement, reduced concrete cover, unsatisfactory concrete practices, unsatisfactory curing and higher volume of permeable voids (VPV) which render such bridge decks susceptible to water ingress and leakage below. A third category of susceptible bridge decks are associated with asphalt milling which is required as part of asphalt renewal, carbon fibre strengthening, concrete repair or simply waterproofing which may cause damage to the concrete, reduce concrete cover and expose or damage steel reinforcement. When left unprotected such deficiencies can result in corrosion of the steel reinforcement, increase the risk of alkali aggregate reactivity if reactive aggregates are present, adversely affect other concrete members and generally result in reduced overall durability performance. Such durability reducing factors may be avoided by the application of suitable waterproofing membrane systems onto concrete bridge decks and other concrete members, which can ensure the required service life of bridges. 'Ms paper introduces the new waterproofing provisions in the new Vic Roads Standard Specification Section 691 "Waterproofing of Concrete Bridge Decks" and identifies some of the key activities which may suffer due to non-conforming work and which can have a significant impact on the adhesive bond of the waterproofing membrane onto the concrete substrate. It further highlights the need to better control the whole waterproofing membrane system installation, to allow for the early identification and elimination of quality problems and thus maintain its integrity in-situ.