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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 48 Abstracts search results
September 1, 2021
Davood Mostofinejad, Farzaneh Nosouhian, and Bahareh Tayebani
Microbial carbonate precipitation (or biodeposition) has been widely studied for use in characteristics improvement and selfhealing of concrete and mortar of cementitious materials. The presence of a calcium source contributes to the formation of calcite (CaCO3), which is a key component in the biode-position process. The current study is aimed at benefiting from the available calcium ion in seawater as a calcium source in the biode-position of marine structures. To this end, four different bacteria strains were cultured and added to the mortar mixture for making bacteria-containing mortar specimens. The specimens consisted of six groups of 50 x 50 x 50 mm mortar cubes, 40 x 40 x 160 mm (1.57 x 1.57 x 6.3 in.) mortar prisms, and conventional mortar briquettes, all of which were cured in seawater. The effects of the exposure to seawater were mechanically investigated at different mortar ages in terms of their compressive, flexural, and tensile strengths and compared with control specimens made with no bacteria and cured in water. The experimental results represented an increase of 97% and 101%, respectively, in compressive and flexural strengths of mortar specimens containing Bacillus subtilis and cured in seawater at 28 days. It was found that the specimens cast and treated with Bacillus sphaericus exhibit a rise of approximately 72% in tensile strength. Therefore, it was concluded that treated mortar with bacteria and cured in seawater may enhance the mechanical properties of mortar, which can be a beneficial development in marine structures. The use of such bacteria strains in concrete technology, specifically in inshore structures, can eliminate the destructive effects of the coastal environment.
September 1, 2020
Edward G. Moffatt, Michael D. A. Thomas, Andrew Fahim, and Robert D. Moser
This paper presents the durability performance of ultra-high-performance concrete (UHPC) exposed to a marine environment for up to 21 years. Concrete specimens (152 x 152 x 533 mm [6 x 6 x 21 in.]) were cast using a water-cementitious materials ratio (w/cm) in the range of 0.09 to 0.19, various types and lengths of steel fibers, and the presence of conventional steel reinforcement bars in select mixtures. Laboratory testing included taking cores from each block and determining the existing chloride profile, compressive strength, electrochemical corrosion monitoring, and microstructural evaluation. Regardless of curing treatment and w/cm, the results revealed that UHPC exhibits significantly enhanced durability performance compared with typical high-performance concrete (HPC) and normal concretes. UHPC prisms exhibited minimal surface damage after being exposed to a harsh marine environment for up to 21 years. Chloride profiles revealed penetration to a depth of approximately 10 mm (0.39 in.) regardless of exposure duration.
Electrochemical corrosion monitoring also showed passivity for reinforcement at a cover depth of 25 mm (1 in.) following 20 years.
Morteza Khatibmasjedi, Sivakumar Ramanathan, Prannoy Suraneni, and Antonio Nanni
The use of seawater as mixing water in reinforced concrete (RC) is currently prohibited by most building codes due to potential corrosion of conventional steel reinforcement. The issue of corrosion can be addressed by using noncorrosive reinforcement, such as glass fiber-reinforced polymer (GFRP). However, the long-term strength development of seawater-mixed concrete in different environments is not clear and needs to be addressed. This study reports the results of an investigation on the effect of different environments (curing regimes) on the compressive strength development of seawater-mixed concrete. Fresh properties of seawater-mixed concrete and concrete mixed with potable water were comparable, except for set times, which were accelerated in seawater-mixed concrete. Concrete cylinders were cast and exposed to subtropical environment (outdoor exposure), tidal zone (wet-dry cycles), moist curing (in a fog room), and seawater at 60°C (140°F) (submerged in a tank). Under these conditions, seawater-mixed concrete showed similar or better performance when compared to reference concrete. Specifically, when exposed to seawater at 60°C (140°F), seawater-mixed concrete shows higher compressive strength development than reference concrete, with values at 24 months being 14% higher. To explain strength development of such mixtures, further detailed testing was done. In this curing regime, the seawater-mixed concrete had 33% higher electrical resistivity than the reference concrete. In addition, the reference concrete showed calcium hydroxide leaching, with 30% difference in calcium hydroxide values between bulk and surface. Reference concrete absorbed more fluid and had a lower dry density, presumably due to greater seawater absorption. Seawater-mixed concrete performed better than reference concrete due to lower leaching because of a reduction in ionic gradients between the pore solution and curing solution. These results suggest that seawater-mixed concrete can potentially show better performance when compared to reference concrete for marine and submerged applications.
July 1, 2020
Hayeon Kim, H. M. Son, Solmoi Park, Joonho Seo, and H. K. Lee
The present study investigated the effects of temperature and salinity on CaCO3 production metabolism by soil bacteria. S. pasteurii was incubated in a urea-calcium lactate medium with the variables of salinity (0.5, 2, and 3.5%) at 10, 20, and 30°C. The effects of temperature and salinity on the growth, activity of urea hydrolysis, and CaCO3 production were determined by comparing the growth rate and the changes in concentration of the NH4 + and
Ca2+. The effects of temperature and salinity on concrete surface treatment by S. pasteurii were conducted by water absorption test. The CaCO3 precipitation metabolism of S. pasteurii was predominantly affected by temperature, while there was no significant difference in the metabolic capacity in terms of salinity. The water absorption rate of surface-treated concrete reduced with increasing temperature and salinity.
May 1, 2020
Anwar Al-Yaqout, Moetaz El-Hawary, Khallad Nouh, and Pattan Bazieth Khan
The main objective of this paper is the investigation of the corrosion resistance of reinforced concrete containing various proportions of recycled aggregates (RA) combined with 25% ground-granulated blast-furnace slag (GGBS) as a partial cement replacement. An accelerated corrosion system was designed to test the steel corrosion in reinforced concrete by subjecting the samples to 150 and 300 wetting-and-drying cycles. The results, in general, showed that the use of RA in concrete mixtures was found to reduce the compressive strength, increase chloride penetration, decrease the corrosion potential of reinforcing bars, reduce the electrical resistance of concrete, and hence increase the corrosion risk. However, better results were achieved by the addition of 25% GGBS, which increased the core compressive strength and electrical resistance. Moreover, better results were achieved for normal and slag mixtures that have 0.788 in. (20 mm) concrete cover than those having 0.394 in. (10 mm) cover.
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