Bridge Expansion Joint for Bridges with Expansion Joints in Deck Slabs on Steel Slag Fill

Steel slag is a byproduct of steel production that can be used as a fill material for bridge approaches. Steel slag has high strength and durability, but can be subject to volume expansion due to the hydration of free lime and magnesia. Steel slag near existing expansion joints requires careful planning to minimize the effects on the joints. Steel slag properties include high density (2500-3000 kg/m3), high strength, and good drainage. Steel slag has a higher density than natural aggregate, which can be beneficial for applications where high density is required. However, the high density also increases the load on the soft ground, which can increase settlement. Volume expansion of steel slag occurs when the free lime and magnesia in the slag hydrate over time. The expansion can cause the fill to heave, which can affect adjacent expansion joints. The steel slag must be weathered or treated to reduce the free lime and magnesia content before use as a fill material. Environmental considerations for steel slag fills include the potential for leaching of heavy metals and other contaminants. The steel slag must be tested for contaminant leaching before use as a fill material. The fill must be designed to prevent leaching of contaminants into the groundwater. Settlement of steel slag fills depends on the compaction level and the applied load. Properly compacted steel slag fills have settlement characteristics similar to natural granular fills. Settlement monitoring is recommended during and after steel slag placement near existing joints. Post-installation inspection of existing expansion joints must verify that the steel slag 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.