Bridges

The common practice of waterproofing road bridge decks with a membrane and asphalt has been a common design approach for many decades. However, if older bridges with concrete decks performed well in rural areas, why does asphalt need to be used? Today, with better access to technology in Australia and the push for road agencies to procure more sustainable practices, it may be better to use concrete surfaces again, negating the need for asphalt as the waterproofing layer.

There are clear benefits of a concrete-wearing course, such as the concrete-coloured surface reflects more light, reducing energy costs for nighttime lighting, the exposed concrete surface absorbs carbon, and the minor reduction in dead load without asphalt slightly reduces member sizes for small-span bridges. The issues raised by designers of poor ride quality and skid resistance from an exposed concrete surface for the bridge deck can be easily overcome with conventional diamond grinding.

This paper explores conventional diamond grinding practices and highlights the application of diamond grinding on several road bridges on the Pacific Highway in northern NSW as an alternative to a bitumen membrane and asphalt surfacing to waterproof the bridge deck. It also provides practical design advice for use with the design drawings to allow asset managers to achieve long-term outcomes for a waterproof deck without the need for asphalt.