The Feasibility of Modified Magnesia-Phosphate Cement as a Heat Resistant Adhesive for Strengthening Concrete with Carbon Sheets

Abstract

External bonding of carbon fiber sheets has become a popular technique for strengthening concrete structures all over the world. Epoxy adhesive, which is used to bond the carbon fiber sheets and concrete, deteriorates rapidly when being exposed to high temperatures. This paper presents a high-temperature-resistant modified magnesia-phosphate cement (MPC) with the compressive strength that does not decrease at the temperature of 600˝C. The bond properties of both the modified MPC and the epoxy adhesive between externally bonded carbon fiber sheets and concrete were evaluated by using a double-shear test method after exposure to elevating temperatures from 105˝C to 500˝C. The results showed that the bond strength of the modified MPC at room temperature (RT) is much higher than that of the epoxy resin. Full carbonation with almost 0 MPa was detected for the epoxy sample after the exposure to 300˝C, while only 40% reduction of bond strength was tested for the modified MPC sample. Although the modified MPC specimens failed through interlaminar slip of fiber strips instead of complete debonding, the MPC specimens performed higher bond strength than epoxy resin at ambient temperature, and retained much higher bond strength at elevated temperatures. It could be concluded that it is feasible to strengthen concrete structural members with externally bonded carbon fiber sheets using the modified MPC instead of epoxy adhesive. Furthermore, the use of the modified MPC as the binder between carbon fiber sheets and concrete can be less expensive and an ecologically friendly alternative.

Verbundverhalten mineralisch gebundener und polymergebundener Bewehrungsstrukturen aus Carbonfasern bei Temperaturen bis 500 °C

“…In Bezug auf den Verbund mit dem Beton ist eine deutlich abweichende Tendenz zu verzeichnen. Auszugsversuche ergaben eine dramatische Abnahme der Haftfestigkeit von bis zu 90 % bei einer Temperaturerhöhung auf 200 °C . Ein vielversprechender Lösungsansatz zur Erhöhung der Leistungsfähigkeit des Verbunds und hiermit des Verbundwerkstoffs Carbonbeton ist die Entwicklung weniger temperaturempfindlicher Tränkungs‐ bzw.…”

The Experimental Study of the Temperature Effect on the Interfacial Properties of Fully Grouted Rock Bolt

“…Yao et al [12] derived the rock bolt interface shear stress produced by the deformation of the surrounding rock, taking the displacement of rock as the functional parameter, thereby allowing the location of the neutral point and axial force distribution of a fully grouted rock bolt to be determined. Based on the damage characteristics of rock and soil under the action of shear stress and the load transfer mechanism of rock bolts in rock and soil mass, Zou et al and others [13][14][15] established a differential equation for the load transfer of a rock bolt when the rock and soil mass was damaged, and derived an analytical solution of the distribution of axial force, shear displacement, and side friction along the length of a rock bolt.…”