Bearings and expansion joints for bridges

Perhaps the most well known application of resins in civil engineering is in the form of resin mortar for either bridge bearings or expansion joint nosings. In bearings the mortar is used as a bedding compound on which to seat rubber or steel bearing pads. These pads serve to transfer loads from the superstructure to piers or abutments and the stresses they resist are largely compressive in nature.

Expansion joints in concrete bridges were traditionally formed by the use of steel edging angles anchored or bolted into the concrete deck either side of the expansion gap. Such joints have a limited life due to disintegration of the supporting concrete under the action of traffic impact and they are very difficult to repair or replace. As a result resin mortar nosings were introduced on UK highway bridges in the mid 1960s but they too were not entirely free from trouble. The early nosings were based on relatively slow curing epoxy systems and a typical installation procedure is illustrated in Fig. 7.1(1). In due course other epoxy formulations began to appear and faster curing systems were introduced in an attempt to avoid the need for heating and testing in cold weather.

In the late 1960s transverse cracks began to appear in some nosings and in the following years hollowness and cracking became a major nuisance.