Investigation of the effect of uniform magnetic field on the bond strength of rebar in concrete containing quartz aggregates using pull-out test

The present study was an attempt to investigate the effect of direct and uniform magnetic field on concrete-steel rebar bond strength in fresh and hardened concrete specimens containing quartz aggregates using pull-out test. Moreover, compressive strength test was performed on all magnetic and non-magnetic specimens at 28 days of concrete age in order to investigate the effect of compressive strength of concrete on bond strength. In the present study, a concrete mixture containing smart quartz aggregate was designed for a compressive strength of 30 MPa, . The water to cement ratio was selected to be 0.4 for concrete mixes. The method of fabrication and processing of samples was performed according to ASTM C192 . Accordingly, first one-third of the fine-grained and one-third of the mixing water were added to the mixer with one-third. The remaining cement and water were gradually added to the concrete mix. At the end, superplasticizer was gradually added to the concrete mix for 1 to 2 minutes and then the concrete mixing process was continued for 3 minutes. In order to prevent the magnetic field from being absorbed by the concrete mold, concrete samples were sampled in plastic molds. Concrete samples were covered with a wet sack at a temperature of 20–22 ° C for 24 hours and then removed from the formwork and stored under moist conditions until the experimental age. The device used in this study is able to convert electricity into a uniform magnetic field with an intensity of 0.5 Tesla. According to the results, the failures in all specimens are of slip type with no fissure cracks. The results also showed that applying a magnetic field to the concrete can lead to enhancement of bond strength by about 55% and 73%, in 14 and 20 mm rebar respectively.