PSI - Issue 70

R. Karthikeyan et al. / Procedia Structural Integrity 70 (2025) 89–96

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2.2 Casting Procedure of Beam Specimens A tilting type drum mixer was used for mixing fresh concrete. The cement, fine aggregate, coarse aggregate, and pre-treated rubber shreds were placed inside the wet drum and then dry mixed. To this dry mixture, 80% of the water was added slowly and mixed thoroughly. Fibres were added slowly and evenly along the wall of the drum to avoid formation of fibre balls and clustering. The remaining water was added slowly and then mixed thoroughly. The beam specimens were cast using wooden moulds. Care was taken to see that the concrete was properly placed in the moulds and compacted uniformly using a needle vibrator. The beam specimens were demoulded after 24 hours of casting and cured in a standard manner. The beam specimens were cast in batches. Control specimens were also cast simultaneously along with the test beams. The different stages of casting of beam specimens are presented in Fig. .2

Fig.2 Casting of Beam Specimens

2.3 Details of Tested Beams Seven specimens of 3000 mm in length and 150 x 250 mm in cross-section were cast and tested. A longitudinal reinforcement (2 nos, 12 mm diameter) was adopted to prepare the beam specimens. To ensure the beams' flexural action until they failed and avoid any premature shear failure, two-legged shear stirrups with an 8 mm diameter were installed at 125 mm c/c. The information of the beam section is depicted in Fig. 3.

Fig. 3 Beam section Details

2.4Test Set-up

Four - point bending test was performed on seven beams in a 500 kN loading frame. The beams were held up by rollers at one end and hinges at the other. The test span was 2800 mm because the beams had 100 mm bearings on both ends. Spreader beams were used to apply two-point loads. The deformation was noted at mid-point and at load points using deflection gauges of 0.01mm precision. Using a crack scope with a precision of 0.02 mm, the crack width was noted during the loading process. Fig .4 shows the test configuration of the beam.