Construction Bulletin Number 22
 

Subject:			Removal of forms for culvert walls
Category:			Structures
Issued:			November 5, 2003
Contact Person:			State Bridge Construction Engineer
Phone Number:			(919) 733-2210
Issue Details:
	Table 420-1 of the January 2002 Specifications requires the top slabs and walls of box culverts to achieve a minimum compressive strength of 2,400 psi prior to removal of the forms and falsework. This portion of the table deals with members subject to dead load bending. Culvert walls are only subject to dead load bending when a load is placed on them. This situation would occur when casting the walls and top slab monolithically. When culvert walls are cast separately, the minimum strength for form removal is dependent upon wall height. If the wall is 10 feet or greater, the 2,400 psi strength still applies. For walls less than 10 feet, there is no strength requirement. However, there must be a minimum of 12 hours between the completion of casting and form removal.
References:		1995 Standard Specifications - Section 225-3, Article 104-3 1995 Construction Manual - Section 225 1995 Roadway Standard Drawings 930.142002 Standard Specifications – Section 420-17 Table 420-1
Illustrations:		None