Technical Questions - ACI Concrete Knowledge Center  
   

Emergency Construction Joint Procedures
 
Q. While the contractor was placing a trench footing, the concrete supply was interrupted, creating an unexpected cold joint. The footing is 2 ft (0.6 m) wide, 4 ft (1.2 m) deep, and 40 ft (12 m) long with 10 longitudinal reinforcing bars (three top and bottom and two on each side) enclosed by stirrups. The cold joint is not at a uniform depth. It’s about 1 ft (0.3 m) below the plan elevation for 20 ft (6 m), then slopes all the way to the bottom of the footing at the 40 ft (12 m) mark. What should have been done when it was apparent that an emergency construction joint was needed?

A. Emergency construction joints are sometimes needed when unexpected work stoppages occur. Documents in the ACI Manual of Concrete Practice don’t mention or distinguish between procedures for emergency or planned construction joints in structures other than pavements. Two ACI documents briefly discuss preparation of cold-joint surfaces prior to subsequent concrete placements that are in contact with the surfaces. Section 3.5.7 of ACI 336.1-01, “Specification for the Construction of Drilled Piers,”1 directs the contractor to:

“Place concrete in pier in one continuous operation, unless otherwise directed by the Owner’s Representative-Geotechnical Engineer. Level, roughen, and clean the surface of construction joints to the satisfaction of the Owner’s Representative-Geotechnical Engineer before recommencement of concrete placement. Provide reinforcing dowels or shear key when directed by the Owner’s Representative-Geotechnical Engineer.”1
Section 7.7.5 of ACI 309R-05, “Guide for Consolidation of Concrete,”2 discusses cold joints as follows:
“Delays in concreting can result in cold joints. To avoid cold joints, placing should be resumed substantially before the time of initial set. For unusually long delays during concreting, the concrete should be kept live by periodically revibrating it. Concrete should be vibrated at approximately 15 minute intervals or less, depending upon job conditions. Concrete should not be overvibrated to the point of causing segregation. Furthermore, should the concrete approach time of initial setting, vibration should be discontinued and the concrete should be allowed to harden. A cold joint will result, and suitable surface preparation measures should be applied.”2
If design professionals are on site or can be contacted, they should make decisions regarding emergency construction joints. The drilled piers document, for instance, gives responsibility for discontinuing concrete placement to the Owner’s Representative-Geotechnical Engineer. We found some further guidance on this subject in a section on bridge construction from the Illinois Department of Transportation Construction Manual.3 The manual advises that construction joints in bridge superstructures should be avoided at locations other than those shown on the plans. It also states, however, that occasional equipment breakdowns or sudden storms may make emergency construction joints necessary. While the manual lists preferred locations for emergency construction joints in simple and continuous spans, it also states that construction joints are permissible at other locations if necessary in cases of a real emergency. It cautions, however, to use sound judgment when making an emergency construction joint and instructs field engineers to consult their supervising engineer before granting permission to make a construction joint that is not of an emergency nature.

More detailed instructions for emergency construction joints may be included in the specifications for the project and may include provisions requiring some or all of the following:

  • Reinforcing bar dowels fully developed on both sides of the cold joint when the joint is not perpendicular to the primary reinforcing;
  • Thorough cleaning of the joint face prior to placing additional concrete;
  • Sandblasting to expose coarse aggregate; and
  • Bedding grout worked into the surface of the joint immediately prior to placing additional concrete.
    • To summarize, in the absence of specific instructions in the contract documents, the design professional should preferably make decisions regarding the procedures to be followed when an emergency construction joint is needed. If the design professional can’t be contacted and immediate action is needed, the contractor may have to bulkhead off the placement and possibly install reinforcing bars normal to the construction joint surface. For the trench footing you mentioned, the bulkhead would usually be installed with a vertical form normal to the direction of the reinforcing steel. The trench would then be filled to the full depth of the footing. The hardened concrete surface at the bulkhead would then be prepared following normal practice for construction joints as directed by the design professional.

    References

    1. ACI Committee 336, “Specification for the Construction of Drilled Piers (ACI 336.1-01),”
      American Concrete Institute, Farmington Hills, MI, 2001, p. 7.
       
    2. ACI Committee 309, “Guide for Consolidation of Concrete (ACI 309R-05),”
      American Concrete Institute, Farmington Hills, MI, 2005, p. 19.
       
    3. Construction Manual, Illinois Department of Transportation, Jan. 2006, Section 500, pp. 7-8.


    Bookstore Purchase ACI documents at the ACI Bookstore

    Posted 11/29/07.

    Disclaimer: Questions in this column were asked by users of ACI documents and have been answered by ACI staff or by a member or members of ACI technical committees. The answers do not represent the official position of an ACI committee. Only a published committee document represents the formal consensus of the committee and the Institute.
      Was this answer useful? Yes No