Rigid culverts with invert wear may be rehabilitated by paving the lower quadrant of the culvert. Where there is no reduction in the structural capacity of the culvert, the invert may be protected from further erosion by placing portland cement concrete or by using shotcrete. Welded wire mesh may be used to strengthen the culvert where it is necessary to do so. For an unreinforced concrete pipe, this will be the case where there is either significant invert wear or longitudinal cracking. Strengthening of a reinforced concrete pipe may be deemed necessary where there is significant longitudinal cracking, invert wear, or spalling. Dowels should be drilled into the member to be repaired, to provide anchorage for the welded wire fabric.
Cracks and spalls caused by flexural distress may be repaired in rigid culverts by sealing and patching. Spalls may be patched with a mortar — or cement-based material, a procedure that is inexpensive and requires little resource allocation. Cracks may be sealed with either a flexible or a nonflexible sealant. If the crack is continuing to move, and if there will be no loss in the structural capacity of the culvert if it continues to do so (circumferential cracks may be an example), a flexible sealant may be used. If the crack has stabilized, or if additional movement is not acceptable, a nonflexible sealant such as a cement mortar may be appropriate. However, the sealant itself will not prevent additional movement. The underlying cause of the cracking must be discovered and appropriate measures such as pressure grouting applied.
Cracking caused by shear failure of the wall section is a cause for immediate rehabilitative efforts. The replacement or structural relining of the affected pipe will be necessary.
If reinforced concrete pipes separate at the joints and infiltration or exfiltration occurs, not only must the joint be repaired, but the surrounding embankment must be stabilized. The concrete pipe joint may be sealed by the use of an expansion ring gasket and band to prevent further infiltration or exfiltration. Stabilizing the embankment may be accomplished by pressure grouting.
