Abstract
Magnesium phosphate cement (MPC) has been proven to be a very good repair material for deteriorated concrete structures. It has excellent adhesion performance, leading to high bonding strength with old concrete substrates. This paper presents an experimental study into the properties of MPC binder as the matrix of carbon fiber sheets to form fiber-reinforced inorganic polymer (FRIP) composites. The physical and mechanical performance of the fresh mixed and the hardened MPC paste, the bond strength of carbon fiber sheets in the MPC matrix, the tensile strength of the carbon FRIP composites and the microstructure of the MPC matrix and fiber-reinforced MPC composites were investigated. The test results showed that the improved MPC binder is well suited for developing FRIP composites, which can be a promising alternative to externally-bonded fiber-reinforced polymer (FRP) composites for the strengthening of concrete structures. Through the present study, an in-depth understanding of the behavior of fiber-reinforced inorganic MPC composites has been achieved.
Highlights
Portland cement concrete structures could be deteriorated during service by loading and various environmental effects
The objective of this paper is to further study the properties of magnesium phosphate cement (MPC) paste and mortar as the matrix to develop fiber-reinforced inorganic polymer (FRIP) composites for the strengthening of concrete structures
Based on the current experimental investigations, the following conclusions can be drawn: 1. The workability of fresh mixed MPC paste was improved and an initial setting time of around min was achieved by using the boric acid when the W/B ratio was 0.22
Summary
Portland cement concrete structures could be deteriorated during service by loading and various environmental effects. They have poor resistance to fire and high temperature, because of the use of organic polymer binders (commonly an epoxy resin) as the matrix of the fibers. The polymer binders form a sealed coating on the concrete surface that prevents the exchange of moisture, leading to the incompatibility of concrete and externally-bonded FRP composites. To overcome these problems, attempts have been made to develop inorganic matrix-based FRP materials for the strengthening of concrete structures. To attain ideal reinforcing effects, the inorganic matrix requires the following features [3]: (1) sufficient mechanical strength for load transfer; (2) the ability to impregnate and create a strong bond with the fiber-reinforcing materials; (3) the ability to bond strongly to the concrete substrate; (4) thermal and chemical compatibility with the concrete substrate; (5) good workability on site, including good consistency and fast-curing ability; (6) environmental acceptability; and (7) limited shrinkage
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