Abstract
The bond between reinforcements and concrete is the only mechanism that transfers the tensile stresses from concrete to reinforcements. Several factors including chemical adhesion, roughness and reinforcement interface and bar bearing affect the bond strength of reinforcements with concrete. This work was carried out considering another varying factor which is maximum aggregate size. Four mixes of concrete with similar compressive strengths but different maximum aggregate sizes of 25.4mm, 19.05mm, 12.7mm and 9.53mm were used with the same bar size of 16mm. Compressive strength, splitting tensile strength and bond strength for each concrete mix were studied. Test results depict a slight increase in compressive and splitting tensile strength with decrease in maximum aggregate size. The bond strength remained at the same level with decrease in maximum aggregate size except at maximum aggregate size of 9.53mm when there was a drop in bond strength, despite better compressive and splitting tensile strengths. ACI-318 and FIB-2010 codes equation for bond strength calculation work well only when the maximum aggregate size is 12.7mm and above. Therefore, maximum aggregate size is critical for bond strength when smaller size aggregates are used.
Highlights
The role of the bond of reinforcement in concrete is of great importance
Trial mixes were conducted to finalize the concrete mix with maximum aggregate size of 25mm and target 28 day compressive strength of 20MPa
From previous studies [22,23,24] and trials of concrete compressive strength tests of each mix, it was observed that with the decrease in maximum aggregate size of coarse aggregates the compressive strength of concrete increases
Summary
The role of the bond of reinforcement in concrete is of great importance. When the concrete member is loaded, tensile stresses from steel to concrete are transferred through the bond. To ensure the safety of concrete, proper bonding between reinforcing steel and concrete is essential When the concrete member cracks, tensile stresses are resisted by the reinforcement, reinforcement slip occurs which is resisted by friction and reinforcement bearing producing bond stresses [1]. Bond behavior of steel reinforcements with concrete is an important aspect which affects the performance of reinforced concrete [2,3,4,5,6]. There are three main components of bond between reinforcements and concrete: friction, chemical adhesion and mechanical interlocking of deformations in steel bars. The factors affecting bond strength include strength and cover of concrete around reinforcement, geometry and yielding strength of reinforcement, embedded length, type of aggregates and admixtures used [1, 7,8,9,10]
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