EFFECT OF TIME ELAPSED BETWEEN SUCCESSIVE CONCRETE POURINGS AND LOCATION OF THE COLD JOINTS ON THE FLEXURAL CAPACITY OF RC BEAMS

Abstract

This research investigates the effect of the time interval between successive concrete pouring and the position of cold joints on properties and bending strength capacity in reinforced beams. Two horizontal cold joints were examined: another positioned in the zone of compressions (h=110 mm) and one situated in the beam's tension area ( h = 50mm). In both cold joint elevations, the time interval between two mert patches was varied as 1.5 hrs.,3 hr and 4 hrs. Furthermore, six nominally standardized RC beams were tested and analyzed with a reference beam devoid of cold joints. The obtained outcomes revealed the decrease of beams' ultimate flexural capacity with an increase in time elapsed between periods of pouring from 1.5 to 4.5 hours. The reduction in flexural strength was more evident when a cold joint went through the compression fibre of a beam. Additionally, the hardness and rigidity of the tested beams roughly inversely correlated with time intervals between consecutive pourings. More specifically, the percentage reduction in ultimate load, stiffness and toughness of cold joints for tension fibres at 1.5 hours was (4.36% ,9.7% and 9.3%) while that of compression fibre was (5.36%),(34.2%)and ( 34.5%  ) % respectively when compared with control beam.