Abstract
This paper presents an experimental study on the flexural behavior of an innovative CA-UHPC (ultrahigh-performance concrete containing coarse aggregate) slab with high and low reinforcement ratios. A total of eighteen CA-UHPC slabs were tested to failure under the parameters of longitudinal reinforcement ratio, curing method, and maximum aggregate size. Test results indicated that sufficient longitudinal reinforcement should be embedded to prevent the brittle failure and disastrous damage. High ductile failure mode was observed for specimens with high reinforcement ratio compared with specimens with low reinforcement ratio. Instead of extensively crushing as normal strength concrete, delamination failure appeared in the compression zone of the CA-UHPC slabs owing to the fibers’ bridging effect, the yielding of longitudinal reinforcement, and the large expansion of flexural cracks which led to the final failure. The reinforced CA-UHPC slabs demonstrated excellent deformability, and ultimate ratio of deflection to span increased from 1/281 to 1/12 when the reinforcement ratio raised from 0% to 3.45%. Stiffness of the reinforced specimens at the flexural cracking state was about 88% and only approximately 6% at the ultimate state, but nearly 50% of the initial stiffness remained when the longitudinal reinforcements yielded, which indicated superior load resistance ability and excellent postcracking deformability. A new ductility index was proposed to evaluate the postcracking ductility of the CA-UHPC specimens. Finally, test results were compared with the flexural strength predictions of CECS 38-2004, ACI 544.4R, and BS EN 1992.
Highlights
UHPC is a generic term for a class of advanced cementitious composite materials that reflects excellent strength, stiffness, ductility, and energy dissipation, and these allow more economic and long-life structures than the conventional concrete even without accounting for the increase in structural durability [1,2,3,4].e tensile strength and ultimate tensile strain of UHPC could be as high as 8 MPa and 1% [5,6,7,8]
All the eighteen CA-UHPC slabs were tested to failure
Delamination failure appeared in compression zone of the CA-UHPC slabs owing to the fibers bridging effect
Summary
UHPC (ultrahigh-performance concrete) is a generic term for a class of advanced cementitious composite materials that reflects excellent strength, stiffness, ductility, and energy dissipation, and these allow more economic and long-life structures than the conventional concrete even without accounting for the increase in structural durability [1,2,3,4]. Sumpter et al [17] compared the structural performance of beams with high-strength reinforcement and conventional reinforcement; test results demonstrated that shear capacity improved distinctly by using high-strength steel reinforcement. Flexural behaviors of four UHPC beams with different reinforcement ratios (0%∼1.71%) were experimentally and numerically investigated by Yoo et al [22] and test results indicated that the postcracking stiffness and load carrying capacity increased with the reinforcement ratio, whereas the first cracking load decreased. Hasgul et al [23] studied the flexural behavior of eight UHPC beams with low and high reinforcement ratios (0.9%, 1.9%, 2.8%, and 4.3%), and results demonstrated that the ductile flexural behavior could be achieved even at high reinforcement ratios because of its high compressive strength and deformation capacity. The applicability of CECS 38-2004, ACI 544.4R, and BS-EN 1992 is compared to evaluate flexural capacity of the innovative CA-UHPC slabs with high and low reinforcement ratios
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