Designing Crossovers

See FHWA’s CRCP Design and Construction Guidelines for the references included in this page. A new, more comprehensive FHWA CRCP Design, Construction, Maintenance and Rehabilitation manual is currently under development and this page will be updated upon its release in the spring of 2016.

Crossovers are often used during construction to provide access to thru traffic. When crossovers are needed, it is recommended to pave the crossover in anticipation of the mainline paving requirement. Leaving gaps in the CRCP to provide room for crossovers is not recommended. When these gaps are paved, they are subjected to excessive movement exerted by the CRCP on both ends due to cyclic temperature changes. During the first days after placing, the leave-out concrete will not have reached its full strength, and will be more susceptible to slippage of the reinforcement.

Paving these sections ahead of the mainline paving prevents reinforcement slippage since it is less unlikely that the short length of the paved crossover will exert excessive force on the fresh CRCP. It is recommended that special attention be given to crossovers when planning the paving schedule in order to minimize the need for leave-outs. Some States such as South Dakota include language in their specifications to discourage leave-out gaps.

An option worth considering is the use of a fast-track (high early strength) concrete in areas where a leave in/leave out would otherwise been used. Where this has been tried wet mat curing has been provided for 24 hours. This method would require prior coordination for the delivery of high-early strength concrete in a timely manner so that all con- crete within the crossover is high-early strength.

When leaving a gap in the CRCP cannot be avoided, a minimum of 50 percent additional reinforcement should be required in the leave-out and across the construction joints on both ends of the leave-out. The additional reinforcement should be evenly distributed between every other regular reinforcement bar. Both additional and regular reinforcement bars should extend into the leave-out no less than 7 ft (2.1 m) and should be embedded no less than 3 ft (0.9 m) into the pavement ends adjacent to the leave-out. Splices in the leave-out area should follow the same requirements as those followed at a construction joint.