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Home > Publications > International Concrete Abstracts Portal
The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.
Showing 1-5 of 123 Abstracts search results
July 1, 2020
Ishtiaque Tuhin and Mostafa Tazarv
Confinement enhances mechanical properties of concrete, especially the strain capacity. As a result, confined reinforced concrete (RC) members usually exhibit higher displacement capacities compared to unconfined members. Even though the behavior of concrete confined with external jackets has been extensively investigated in the past, confined properties of polyureajacketed concrete are largely unknown and were investigated in the present study. Thirty concrete cylinders were tested under slow uniaxial compression to investigate mechanical properties of polyurea-confined concrete and to establish stress-strain behavior. It was found that polyurea does not increase the strength of the confined sections under static loads. However, the compressive strain capacity of polyurea-confined concrete is more than 10%, equal to or higher than the reinforcing steel bar tensile strain capacity. Two uniaxial stress-strain models were developed for polyurea-confined concrete with circular sections under static loads. Analytical studies showed that the displacement ductility capacity of low-ductile bridge columns can be doubled using polyurea jackets. This unique property may make this type of confinement a viable retrofit or rehabilitation method to increase the displacement capacity of low-ductile members and structures in seismic regions.
B. S. Sindu and Saptarshi Sasmal
To develop cementitious composites with improved properties, engineering has to be judiciously done at different scales. In this study, a multi-scale engineered cementitious composite (MS-ECC) with high tensile strength and strain-hardening properties is developed by incorporating nano-, micro-, and macro- (in the form of continuous fibers) fibers into it. At first, a cementitious composite
is developed by individually incorporating nano- and microfibers to understand the influence of each type of fiber and to arrive at the optimum dosage level. Digital image correlation information is employed to investigate the crack properties and fracture process in the developed composite with individual scale fibers. Next, a hybrid cementitious composite, developed by incorporating nano- and
microfibers, is found to demonstrate an improvement in the strength and strain hardening properties. Further improvement in higher scale is carried out by incorporating continuous fibers into it to develop MS-ECC which exhibited tensile strength of 23 MPa (3.63 ksi) and strain capacity more than 8000 micron.
March 1, 2020
Leonidas P. Emmenegger and Alberto A. Sagüés
Half-cell potential mapping is frequently used for the detection of corrosion in reinforced concrete. The procedure can be time-consuming and disruptive, partly due to the need for physical contact with the concrete surface. An alternative is presented in the form of a fast-responding, non-contacting electrode array that requires no surface pretreatment, and is suitable for mobile operation. This approach uses the vibrating Kelvin probe principle, with the electrode hovering over but not touching the concrete surface. Operation is demonstrated on an actual Florida bridge deck with a robust synchronized array as a model for lane-wide roadway scanning. The electrode-to-concrete (operating) surface gap can clear normal deck surface irregularities. Results replicated corrosion-identifying features from conventional half-cell electrode mapping without significant surface preparation or waiting for potential stabilization. The technology is promising for rapid corrosion assessment of bridges at low cost without extended lane closures.
September 1, 2019
Harikrishnan Nair and H. Celik Ozyildirim
Cracks in bridge decks facilitate the penetration of chlorides that induce corrosion of reinforcing steel. Formation of cracks is related to the shrinkage and properties of the concrete and the restraints to movement. Lightweight concrete with a low modulus of elasticity, high creep, and water in the aggregate pores for internal curing has a reduced cracking potential. To control cracking, shrinkage of concrete can be reduced by using a shrinkage-reducing admixture (SRA). A recent study at the Virginia Department of Transportation (VDOT) investigated the performance of both lightweight concretes and concretes with SRA containing normal-weight aggregates in the field and found that these concretes had no cracks or fewer cracks than were typical of decks constructed with normal-weight aggregates over the past 20 years. VDOT developed a new specification that included lightweight concretes or concretes with normal-weight aggregates and SRA and this specification is being used successfully to reduce cracking in bridge decks. This paper summarizes the work conducted to develop the new specification and includes information on field applications.
The presence of uncontrolled or unexpected nonstructural cracking in reinforced concrete structures generally leads to conflict and disputes. The current industry practice aims to prevent or mitigate the presence of cracking at early ages (that is, plastic shrinkage, thermally induced cracking) or due to volumetric changes (restrained or drying shrinkage). However, cracking of concrete can still occur and lead to questioning the durability of concrete with prolonged service life expectations such as bridge decks, piers, or waterfront structures, to name a few. The effect of cracks on chloride penetration has been thoroughly studied, and evidence of the effect of cracks on accelerated ingress of chlorides is well established. Structural codes and guides, on the other hand, consider that the integrity of the concrete element is not significantly affected as long as the crack width does not exceed a recommended limit based on exposure conditions. Similarly, service life predictions based on chloride ingress modeling disregard the effect of cracks. Because crack-free concrete cannot be guaranteed, service life predictions that neglect the effect of cracks can be significantly inaccurate. A simplified approach is presented in this paper, where a correction to the chloride diffusion coefficient of concrete is performed to account for the effect of cracks. This correction is similar, in principle, to the so-called aging or decay coefficient in concrete. Results of Monte Carlo simulations on chloride ingress and estimations of the time-to-corrosion initiation are presented and discussed. Results indicate that a decrease of the reliability index (β), or an increase in the probability of failure (pf), can be calculated when accounting for the effect of cracks.
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