Case Studies in Construction Materials (Jul 2024)
Tension and bond characteristics of foam concrete for repair applications
Abstract
In this study, foam concretes (FCs) 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 a pull-off test while the shear 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 strength for FCs ranged between 6.67 MPa and 8.08 MPa while that of the M25-grade concrete was 5.49 MPa. Additionally, the tensile bond strength of FCs fell within the range of 0.67 MPa to 1.46 MPa while that of the M25-grade concrete was 1.12 MPa. The bond strength obtained from the pull-out test for FCs was observed to vary within the range of 11.87 MPa to 23.26 MPa while that of the M25-grade concrete was 14.14 MPa. FCs 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 FC 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 developed using the GGBS and FA as substitutes for cement and sand, respectively showed promise as an alternative concrete repair material, with comparable or superior tensile and bonding properties compared to M25-grade concrete.
