Concrete experiences volume changes due to temperature and moisture variations. When the temperature changes, concrete contracts and expands. The resulting expansion of the concrete pavement must be taken into account. Normally, concrete pavement is abutted to bridge structures via approach slabs. If the pavement expansion is not accounted for, the approach slabs will be pushed into the bridge and can cause serious damage to the bridge structures. To prevent this problem, a mitigation system is installed at the bridge and pavement interface to account for the expansion. There were three systems in use by the department:

The basic premise of the expansion joint system is that the expansion joint width will be able to absorb any concrete pavement expansion without transmitting the compression forces to the bridge structure.

The wide-flange system is similar to the expansion joint system, except that the expansion joints exist under the wide flange and are not seen from the pavement surface. One advantage is that, since the joint is not exposed to the pavement surface, joint maintenance is minimized.

An anchor lug system tries to restrict the concrete movement at the interface between bridge and pavement by providing several anchor lugs.

TxDOT has investigated the movements of CRCP near bridges and the effectiveness of these three terminal systems in Research project 0-6326, “Rational Use of Terminal Anchorages in Portland Cement Concrete Pavements.”

The research data has shown that the anchor lug system is not effective in the long run. The stresses generated in soil due to slab expansion at lug walls are large enough to result in permanent deformations in soils. The soil does not retract with the lug when the pavement contracts. The permanent deformations result in voids between soil and lug walls.

Field measurements have indicated that the base friction restrains slab movements effectively. Using coarse texture base, such as HMA, might be the most effective tool to control slab movements. Simple expansion joint systems or wide-flange systems are also effective in accommodating slab movements. Expansion joint systems should cost less than wide-flange systems with comparable performance.

The standard for the anchor lug system was deleted and not replaced. The transverse expansion joint details at bridge approaches are shown in sheet 2 of 2 of CRCP and CPCD standards.

Item 368, Concrete Pavement Terminals of 2004 Standard Specification, was removed in the 2014 Standard Specification. Districts may develop a Special Specification for using wide-flange systems.