Abstract
Bridge traffic in lanes adjacent to a deck that is being widened or replaced causes movements in the fresh concrete deck. A study of the effects of these movements in concrete decks is reported here. An experimental investigation was conducted to determine the deformation properties of concrete at early ages. A total of 32 flexural tests were performed using a test apparatus developed to test concrete at early ages. Tests were conducted at concrete ages of 3, 5, 7, 9, and 11 hours, age being reckoned from the time mixing was completed. The test results provided valuable information on the behavior of concrete at early ages. The curvature at first cracking, the modulus of elasticity, and the flexural strength of the material at early ages were determined. A theoretical study was made to determine the traffic induced bending curvature and stresses in the fresh concrete of the widened or replaced bridge decks. A total of 18 hypothetical cases of bridges were analyzed. Two types of beams (Steel I-beams and AASHTO PC beams), three span lengths (50, 70, and 90 feet), and three beam spacings (7, 8, and 9 feet) were considered in the analysis. The results, from both the experimental investigation and the theoretical study, were analyzed to determine the effect of adjacent traffic on the quality of concrete in replaced or widened decks. The calculations showed that the traffic induced bending curvature, in all bridge cases considered, exceeded the curvature capacity of the material during a brief period of time in the early age concrete. That is to say, cracking of the widened concrete deck should be expected in all cases over a short period of time at about 5 hour age. The most critical traffic induced bending curvature occurred at the 5 hour age, which is about the setting age of concrete. Tests showed that the concrete material had least capacity for flexural strain at this age. Procedures to prevent cracking of the widened deck, due to active traffic on the adjacent lane, are presented. These procedures are associated with the control of traffic on the adjacent lane during the casting and curing of the widened or replaced part.
Fouad, Fouad Hilmy (1981). The effect of traffic induced movement on fresh concrete in widened or replaced bridge decks. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -98861.