Abstract
The most common source of failure for tunnellining occurs at the excavated surface due to a high frequency of freeze-thaw cycles and cold weather that significantly drop the strength of the interface between the rock and the concrete. A preliminary experiment was conducted to confront the problems associated with cold weather effect on concrete and the adhering connection between the concrete and the excavated rock surface. A series of composite specimens made of sandstone rocks and concrete with the three types of surfaces (smooth, semi-rough, and rough) were prepared in the Materials Laboratory of Northern Arizona University. All specimens were undertaken up to 180 Freeze-thaw cycles using an ASTM C666 apparatus with modifications on molds and dimensions of specimens. Tensile splitting tests of the interface between concrete and three types of rock surfaces were performed with respect to the bonding strength. The purpose of the research was to (1) evaluate the effect of freezing and thawing cycles on the bonding strength/interface behavior of the composite specimens and (2) to determine the rate at which adhesion strength is lost when undergoing cold weather environment. Based on the test results, the concrete-rock specimens prepared with rough surface show higher bonding strength than the other two surface treated specimens (smooth and semi-rough surface treatments).
Highlights
The concrete-rock composite structure has been used dramatically in engineering design and construction projects, such as tunnels, dams, mining facilities, etc
The interface behavior of the concrete-rock has a significant impact on the determination of the properties of the composite
Fishman [2] analyzed three failure mechanisms of concrete retaining structures situated on rock foundations and concluded that several factors occurred during the rock foundation construction that should be taken into consideration for design and analysis
Summary
The concrete-rock composite structure has been used dramatically in engineering design and construction projects, such as tunnels, dams, mining facilities, etc. The interface behavior of the concrete-rock has a significant impact on the determination of the properties of the composite. Similar with the design of dam foundations, the interface behavior of the concrete-rock structure appeared to be a prominent factor that influences the mechanical properties of the composite in both tunneling and underground mining [4]. The finishing surface between the interface of the concrete and the rock would result in a significant impact on the properties of the composite. The impact of freeze-thaw cycles on the interface behavior of the concrete-rock has not well studied, how the strength of the composite material would change under the action of freeze-thaw cycles. All concrete-rock specimens were prepared in the Construction Materials Laboratory of Northern Arizona University, USA and all concrete-rock specimens were undertaken a series of freeze-thaw cycle tests staring from 0, through 60, 120 and 180 cycles
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