Title: Steel-Concrete Bond in High-Strength Lightweight Concrete

Author(s): Avi Mor

Publication: Materials Journal

Volume: 89

Issue: 1

Appears on pages(s): 76-82

Keywords: aggregates; bond (concrete to reinforcement); silica fume; compressive strength; cracking (fracturing); fatigue (materials); high-strength concretes; lightweight aggregates; lightweight concretes; pullout tests; tensile strength; tests; Materials Research

DOI: 10.14359/1248

Date: 1/1/1993

Abstract:
The objective of this test program was to study the effect of condensed silica fume (CSF) on the mechanical properties of high-strength concrete made with lightweight aggregate (LWA) and to compare these properties to concretes with similar strength properties. The tensile strength (modulus of rupture R), modulus of elasticity E c, stress-strain properties, and bond-slip of reinforcing bars were studied for four concrete mixes of similar high strength [10,000 psi (69 MPa)] with varying contents of CSF (0, and 13 to 15 percent by weight of cement) and low water-cement ratios (0.25 to 0.34). The use of CSF did not significantly change the compressive strength to E c ratio for concretes made from either aggregate, but it doubled the steel-concrete bond strength to compressive strength ratio at 0.01 in. (0.25 mm) slip for LWA concrete while having no significant effect on normal weight aggregate concrete. CSF reduced the porosity and thickness of the transition zone adjacent to the steel, thus improving the adhesion-type bond at small slip levels. The lower E c of LWA concrete, combined with its compatible aggregate and cement paste matrix, results in better utilization of the bond-adhesion, allowing larger stress and strain levels.