Bridge Expansion Joint for Bridges with Expansion Joints in Deck Slabs on Expanded Polystyrene

Expanded polystyrene (EPS) geofoam is a lightweight fill material used to reduce the load on soft ground under bridge approach fills. EPS geofoam near existing expansion joints requires careful planning to minimize the effects on the joints. EPS geofoam properties include very low density (15-30 kg/m3), high compressive strength relative to its weight, and good thermal insulation. EPS geofoam is used as a replacement for conventional fill in areas where the soft ground cannot support the weight of conventional fill. The low density of EPS geofoam reduces the settlement of the soft ground. EPS geofoam installation involves placing the EPS blocks on the prepared subgrade and covering them with a load distribution layer and the road pavement. The EPS blocks must be protected from damage during installation and from fuel and solvent spills during service. Settlement reduction from EPS geofoam is the primary benefit for adjacent expansion joints. By reducing the load on the soft ground, EPS geofoam reduces the settlement of the approach fill, which reduces the differential settlement between the approach fill and the bridge abutment. This reduces the step at the approach slab expansion joint. Buoyancy of EPS geofoam in areas with high groundwater tables must be considered. EPS geofoam has a density lower than water, so it will float if the groundwater table rises above the EPS. The EPS must be anchored or weighted to prevent flotation. Post-installation inspection of existing expansion joints must verify that the EPS geofoam installation has not caused any damage. The inspection should check the joint gap width, the concrete edge beam condition, and the anchor bolt torque. Any damage must be repaired before the bridge is returned to service.