An expansion joint system includes a cover plate; a spline attached to the cover plate; and a core having a fire retardant material included therein in an amount effective to pass testing mandated by UL 2079. The spline depends from the cover plate and is configured to be positioned in a gap between substrates such that the cover plate overlies the gap. The core is compressible between a first face of the spline and one of the substrates and is compressible between a second face of the spline and the other of the substrates, and the expansion joint system is configured to facilitate compression of the core when installed between the substrates by repeatedly expanding and contracting to accommodate movement of the substrates; and the core with the fire retardant material included therein is configured to pass the testing mandated by UL 2079.