Bond Strength Of Concrete Research Articles

Laboratory Evaluation and Field Application of Concrete Reinforcement with Aramid Fiber-Reinforced Polymer Bars

This research describes extensive accelerated aging tests that were conducted on polymer composite bars reinforced with aramid fibers. Aramid fiber-reinforced polymer (AFRP) bars exhibited desirable durability characteristics under a broad range of accelerated weathering effects. They also exhibited satisfactory bond strength and dowel action in concrete. A bridge deck reinforced with AFRP bars was designed with due consideration given to the punching shear mode of failure. Design procedures were verified through scaled lab tests. The construction and cost attributes of AFRPs were evaluated in this field project.

Effect of corrosion on bond behavior and bending strength of reinforced concrete beams

There is growing concern for corrosion damage in reinforced concrete structures with several decades’ service. Pullout tests and beam tests were carried out to study the effect of reinforcement corrosion on the bond behavior and bending strength of reinforced concrete beams. The bond strength of plain bars and concrete initially increases with increasing corrosion, then declines. The turning point depends on the cracking of the concrete cover. The bond strength of deformed bars and concrete increases with corrosion up to a certain amount, but with progressive increase in corrosion, the bond strength decreases, and the cracking of the concrete cover seems to have no effect on the bond strength. On the basis of test data, the bond strength coefficient recommended here, which, together with the bond strength of uncorroded steel bars and concrete, can be used to easily calculate the bond strength of corroded steel bars and concrete. The bond strength coefficient proposed in this paper can be used to study the bond stress-slip relationship of corroded steel bars and concrete. The bending strength of corroded reinforced concrete beams declines with increasing reinforcement corrosion. Decreased bending strength of corroded RC beam is due to reduction in steel bar cross section, reduction of yield strength of steel bar, and reduction of bond capacity between steel bar and concrete.

Factors Affecting Anchorage Bond Strength in High-Performance Concrete

The objective of this investigation was to observe the effect of the compressive strength of concrete, reinforcing bar size, thickness of concrete cover, and amount of web reinforcement on the anchorage bond strength and on the bond behavior of reinforced high-performance concrete. For this purpose, eccentric pullout bond tests were conducted under monotonic loading on high-performance concrete specimens. Some of the specimens were reinforced by one and some by two deformed steel bars. Results indicated that the bond strength between reinforcement and concrete increased with increasing concrete strength, cover thickness, and amount of web reinforcement, while it decreased with increasing bar size. Using the test data, the variation in the average bond strength with respect to each of the stated parameters is formulated. The trend of variation for each parameter is compared with the associated trends inherent in the development length expressions of the American Concrete Institute Building Code and the Eurocode 2. An expression for the required development length, enveloping all the tested specimens, is presented.

Test Method for Measuring the Bond Strength of Latex-Modified Concrete and Mortar

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Effect of Freezing Cycles on Bond Strength of Concrete

Experimental observations on the effect of freezing cycles on the bond behavior between steel reinforcement and concrete are reported. Specimens that experienced 1, 10, and 30 freezing cycles are tested under monotonic and reversed cyclic loadings. Results are compared with experimental observations of identical specimens that did not experience freezing cycles. Under monotonic loading the maximum bond resistance decreases as the number of freezing cycles increases. For reversed cyclic loading the average value of bond factors (ratio of maximum bond strengths to compressive strength) in both directions decreases with an increasing number of freezing cycles. In addition, other mechanical properties of concrete experiencing freezing cycles are also determined. It is concluded that cyclic temperature changes do have definite effects on the bond strength of reinforced concrete structures and on the mechanical properties of concrete.

Bond characteristics of oil saturated concrete

The bond strength of oil saturated concrete is compared to those cured in water or sealed dry as control specimens. Concentric cylindrical pull-out specimens reinforced with one central bar were tested after different oil soaking periods. A modified pull-out test was also used to measure the bond stress distribution along a plain bar in concrete prisms saturated with crude oil. The test results show that the average bond strength between steel bar and concrete, for both plain and deformed bars, decreases with an increase in the amount of absorbed oil. The reduction for the plain bar was between 1.8–2.3 times greater than that for the deformed bar. The study of the bond stress distribution showed that at the maximum applied load, the local bond stress at the embedded end of the oil saturated specimens was six times greater than that at the loaded end. It also showed that the rupture point along the steel bar of oil saturated specimens occured at a lower load compared to that of the other storage condition.

Adfreeze strength of model piles in ice

The adfreeze bond strengths of wood, concrete, and steel H-section piles embedded in fresh-water ice have been measured under constant rates of displacement for displacement rates varying between 10−4 and 10−1 mm/min (loading rates between 10−3 and 10 kN/min). Wood piles showed the highest adfreeze strength (0.6 and 1.8 MPa); that for concrete piles was independent of rate of displacement (average value 0.8 MPa); that for steel H-sections varied between 0.2 and 0.6 MPa. These results were used in estimating the contribution of ice adhesion to the total adfreeze strength of various piles in frozen sand.

ベントナイト液中のコンクリートの鉄筋の付着強度に関する研究 : 其の一・モデル実験

These experiment have been performed to investigate the bond strength of reinforcement in concrete cast into the bentonite suspension and the compressive strenght of that concrete. In this method, the bentonite suspension is always in jected, as the drilling proceeds, to prevent the wall surface from falling and then concrete is poured into the bentonite suspension using tremie pipe. It is feared that the compreesive strength of concrete and the bond strength of the reinforcement may decrease as the result of the in perfect replacement of bentonite suspension with concrete. These expreiments were performed to clarify there points and they consisted of the two experments, one of which was the model experiment in the laboratory and the other was the experiment performed at job sites, The results of the experments show that the compressive strength of the concrete cast into the bentonite suspension about 13% concentration is lower than that of the concrete cast in ordinary way, and in the concrete cast into the bentonite suspension below the value, it does not decrease so much. However, at the top end and the both side ends of the concrete wall cast into the bentonite suspension, consiclerable decrase of the compressive streugth is observed. As to the bond strength in the concrete cast into the bentonite suspension, it is found to be lower than that of the ordinatry concrete and the following formula for the relation between the concentration of bentonite suspension and the bond strength is suggested. ^τx=α・τ_c(1-βX^2) where; X=concentration of bentonite suspension (%) τ_x=bond strength (kg/<cm>^2) for concrte poured into bentonite suspension with concrete of × % τ_c=bond strength (kg/<cm>^2) of ordinary concrete. α, β=coustants Further, it is shown that the bond strength of concrete decreases considerably when the bentonte suspension is gelatinized by Ca^++ ion of the cement. And the bond strength of ths concrete at the top and the both side ends of the wall is also found to decrease.

2262 ベントナイト懸濁液中に打設したコンクリートの圧縮強度及び付着強度

2262 ベントナイト懸濁液中に打設したコンクリートの圧縮強度及び付着強度