Tension and bond characteristics of foam concrete for repair applications
Arvind Vishavkarma, Kizhakkumodom Venkatanarayanan Harish
Abstract
In this study, foam concretes (FC) were developed, and their tension, shear, and bond properties were investigated for potential repair applications. Seven FC mixtures with varying combinations of ground granulated blast furnace slag (GGBS) and fly ash (FA) were prepared, along with one M25-grade conventional concrete mixture. The tension properties of both types of concrete were assessed through split tensile strength, flexural strength, and pull-off test while the shear strength and bond strength (with reinforcing bars) were determined using the slant shear test and pull-out test, respectively. The results indicated that the compressive strength of the FC mixtures at 28 days ranged from 21.98 to 40.08 MPa, satisfying the requirements of IS 456:2000 for M15 to M30-grade concrete. Furthermore, the split tensile strength of FC was in the range of 2.21 MPa to 2.83 MPa while M25-grade concrete showed a strength of 2.24 MPa. Shear strengths for FC and M25-grade concrete ranged between 6.67 MPa and 8.08 MPa, and 5.49 MPa, respectively. Additionally, tensile bond strengths of FC and M25-grade concrete fell within the range of 0.67 MPa to 1.46 MPa and 1.12 MPa, respectively. The bond strength obtained from the pull-out test for FC and M25-grade concrete was observed to vary within the range of 11.87 MPa to 23.26 MPa and 14.14 MPa, respectively. FC exhibited superior bond strength compared to M25-grade concrete with both the concrete substrate and reinforcing bars. It was also noted that the tension and bond strength of FC were linearly correlated with its compressive strength. Microstructure analysis indicated that macropores were isolated and discontinuous in all mixtures. The improvement in mechanical and bond properties was attributed to enhancements in the microstructure, and the ability of GGBS and FA particles to fill pores in the cementitious paste regions. In conclusion, FC showed promise as an alternative concrete repair material, with comparable or superior tensile and bonding properties compared to M25-grade concrete.