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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 35 Abstracts search results
May 1, 2021
Lihe Zhang, Dudley R. Morgan, Iain Kirk, Anastasia Rolland, and Robert Karchewski
Wet-mix shotcrete has been used more and more for structural applications in the past few decades. Recently, wet-mix shotcrete was successfully used to construct a mass structural wall with congested reinforcement and minimum dimensions of 1.0 m in a sewage treatment plant. A low-heat shotcrete mixture that included up to 40% slag was proposed for shotcrete application. A preconstruction mockup was shot to established proper work procedures for shotcrete application and qualify the shotcrete mixture and shotcrete nozzlemen. Extraction of cores and cut windows from the mockup confirmed proper consolidation around the congested reinforcement. A thermal control plan was developed, which included laboratory and field testing requirements, thermal analysis modeling with a three-dimensional (3-D) finite element program, and thermal control requirements, including installation of cooling pipes and thermal blankets. Shotcrete proved to be an efficient means for mass concrete structural construction. Thermal control for mass shotcrete construction was studied, and the proposed thermal control plan was proved to function properly. The general guidance for mass shotcrete construction is provided.
May 1, 2020
Mohamed M. Sadek, Mohamed K. Ismail, and Assem A. A. Hassan
This study aimed to optimize the use of fine and coarse expanded slate lightweight aggregates in developing successful semi-lightweight self-consolidating concrete (SLWSCC) mixtures with densities ranging from 1850 to 2000 kg/m3 (115.5 to 124.9 lb/ft3) and strength of at least 50 MPa (7.25 ksi). All SLWSCC mixtures were developed by replacing either the fine or coarse normal-weight aggregates with expanded slate aggregates. Two additional normal-weight self-consolidating concrete mixtures were developed for comparison. The results indicated that due to the challenge in achieving acceptable self-consolidation, a minimum binder content of at least 500 kg/m3 (31.2 lb/ft3) and a minimum water-binder ratio (w/b) of 0.4 were required to develop successful SLWSCC with expanded slate. The use of metakaolin and fly ash were also found to be necessary to develop successful mixtures with optimized strength, flowability, and stability. The results also showed that SLWSCC mixtures made with expanded slate fine aggregate required more high-range water-reducing admixture than mixtures made with expanded slate coarse aggregate. However, at a given density, mixtures developed with expanded slate fine aggregate generally exhibited better fresh properties in terms of flowability and passing ability, as well as higher strength compared to mixtures developed with expanded slate coarse aggregate.
January 1, 2019
Mohamed K. Ismail, Assem A. A. Hassan, and Mohamed Lachemi
This investigation aims to study the abrasion resistance of developed self-consolidating engineered cementitious composite (SCECC) mixtures using the rotating-cutter and sandblasting abrasion tests. The fresh and mechanical properties of the developed SCECC were also investigated in this study. Additional conventional self-consolidating concrete (SCC) (with 10 mm [0.39 in.] coarse aggregate) and vibrated engineered cementitious composite (VECC) mixtures were tested for comparison. The standard engineered cementitious composites (ECCs) are commonly developed using a high volume of fly ash (FA) and microsilica sand (SS). In this study, the FA was partially replaced by varied volumes of slag (SL), silica fume (SF), and metakaolin (MK), while the SS was replaced by crushed granite sand (CS) of different sizes. The results indicated that combining SL, SF, or MK with FA resulted in developing SCECCs with adequate deformability and higher abrasion resistance, compressive strength, and flexural strength. Using 20% of MK in the development of SCECC showed the best abrasion resistance improvement in both rotating-cutter and sandblasting tests. The results of rotating-cutter and sandblasting tests also indicated that SCECC mixtures appeared to have less abrasion resistance compared to their SCC counterpart mixtures with 10 mm (0.39 in.) coarse aggregate.
September 1, 2017
L. A. Sbia, A. Peyvandi, I. Harsini, J. Lu, S. Ul Abideen, R. R. Weerasiri, A. M. Balachandra, and P. Soroushian
A pilot-scale field investigation was conducted through which: 1) a refined ultra-high-performance concrete (UHPC) mixture was prepared in a ready mixed concrete plant; 2) a large reinforced UHPC block was constructed through placement, consolidation, and finishing of UHPC; and 3) a commonly available concrete curing (insulating) blanket was applied for field thermal curing of the UHPC block using the exothermic heat of hydration of the cementitious binder in UHPC. Monitoring of the reinforced UHPC block temperature over time confirmed the development of a reasonably uniform temperature and a viable temperature time history, which suited thermal curing of UHPC without any heat input. In-place nondestructive inspection of the reinforced UHPC structure pointed at timely setting and strength development, leading to achievement of ultra-high-performance status. Specimens were cored from the large reinforced concrete block and subjected to laboratory testing. The experimental results indicated that the field thermal curing was more effective than the laboratory thermal curing considered in the project, and that the pilot-scale production of the UHPC mixture produced compressive strengths approaching 170 MPa (24.7 ksi).
May 1, 2017
Wael A. Megid and Kamal H. Khayat
Multilayer casting of self-consolidating concrete (SCC) can be critical in situations involving casting of successive lifts. The increase in structural buildup at rest of freshly cast SCC material prior to the placement of a successive layer can result in lift lines and loss in interlayer bond strength. Delay in the casting of successive lifts without mechanical consolidation can further reduce bond. Eight SCC mixtures designed to develop different levels of structural buildup at rest were investigated. The structural buildup at rest was determined by multiplying the values of initial slump flow, T50, or J-ring flow by average rates of change in these properties with rest time. Bond between successive layers was determined using composite specimens cast with two lifts of SCC after rest periods of 17 to 52 minutes, which corresponds to 25 to 60 minutes of concrete age. Bond strength was determined using the slant shear and direct shear test setups. Compared to monolithically cast samples, composite specimens had residual bond strengths of 15 to 100%. The critical delay time to secure at least a 90% residual bond strength was found to vary between 5 and 55 minutes, depending on the structural buildup at rest of the concrete in the existing layer. Statistical models for predicting residual bond strength between successive lifts were established and account for the structural buildup at rest of the first lift and delay period between successive lifts. Based on the level of structural buildup at rest, three categories of SCC are proposed. Category III SCC with relatively low structural buildup at rest can develop high residual interlayer bond. Such concrete should have maximum slump flow filling ability index of 800 mm.mm/min (31.5 in.in./min), T50 viscosity index of 0.08 sec.sec/min, and J-ring passing ability index of 600 mm.mm/min (23.6 in.in./min).
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