Two-Course Bonded Concrete Bridge Deck Construction. 'An Evaluation of the Technique Employed'.

摘要

A two-course bonded technique was used in June 1974to construct six bridge decks in Virginia. The overlay concretes selected for use as wearing courses included a latex modified concrete, a high quality PCC,and a wire fiber reinforced concrete. Based on comparisons of two-course and single-lift construction techniques the following conclusions are made. An overlay should be placed not sooner than two days after a base layer is placed. Light sandblasting of the base layer removes laitance that might adversely affect the bond between the base layer and overlay. A bonding layer of cement slurry should be broomed onto the base layer not further than 10feet (3meters) nor longer than 15minutes ahead of the overlay placements. The same depth of clear concrete cover above the top reinforcing steel resulted from the two-course construction as from the single-lift technique. The construction activities proceeded in an orderly and satisfactory manner and coefficients of variation for the time intervals required to install the base layers and the overlays are comparable to values representing excellent control for single-lift construction. The average man-hours required to install concrete in the separate layers of the two-course decks was 33% greater than for conventional single-lift decks,but in terms of project days,the two-course and single-lift techniques are equivalent. The total additional cost of the two-course technique is approximately 5% of the cost of the bridge deck superstructure.