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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 281 Abstracts search results
September 1, 2021
M. A. R. Manzano, Y. S. B. Fraga, E. F. da Silva, R. B. de Oliveira, B. Caicedo Hormaza, and R. D. Toledo Filho
This study investigates the influence of internal curing water on the compressive strength and microstructure of high-performance cementitious materials. For this, three high-performance fine-grained concrete (HPFC) and cement pastes were prepared. Two reference mixtures were investigated with total water-cement ratios (w/c) of 0.30 and 0.35. The third mixture was prepared with a basic w/c of 0.30 and the addition of 0.3% of superabsorbent polymer (SAP), resulting in a total w/c of 0.35. X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and compressive strength tests were performed. The incorporation of SAP resulted in a refinement of the porous structure of the paste, despite increasing the total porosity. In addition, the paste containing 0.3% SAP resulted in an intermediate calcium hydroxide content compared with the reference pastes. Thus, it was concluded that SAP internal curing water participates in the hydration reactions of the cementitious material.
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.
July 1, 2021
Ultra-high-performance concrete (UHPC) is the outcome of the mixture of several constituents, leading to a highly complex material, which makes it more difficult to understand the effect of each component and their interactions on compressive strength. This research goal is developing an artificial neural network (ANN)
approach to predict the compressive strength of UHPC, being able to incorporate supplementary cementitious materials (SCMs), and even different situations in relation to the aggregate: from pastes to incorporation of coarse aggregate. The one-hidden-layer ANN model was trained with 927 data by using the R-code language. The data was produced by collecting data from 210 experiments combined with 717 dosages from previous research. The Olden algorithm was used to analyze the relationships between the UHPC’s components and strength. The results indicated that the
ANN is an efficient model for predicting the compressive strength of UHPC, regardless of the SCM used or maximum size of aggregate
Adeyemi Adesina and Sreekanta Das
Engineered cementitious composites (ECC) are special fiber-reinforced cementitious composites with outstanding performance. However, the high cost and unavailability of the special sand (that is, microsilica sand [MSS]) used as the aggregate for such composites have limited its use and even made it impractical in some geographical locations. Therefore, there is a dire need to find alternative materials that can be used to replace MSS in ECC. This study was carried out to investigate the feasibility of using recycled concrete (RC) as an alternative aggregate, which is a much cheaper and more sustainable option as opposed to the conventional MSS currently used in ECC. Fly ash—the coal-based, thermal, plant-generated waste material—was incorporated as an alternative binder to partially replace the traditional binder, portland cement (PC), which is a large greenhouse emitter. Thus, the use of fly ash to replace a high volume of ECC would result in a reduction in the carbon footprint of ECC. The RC was used to replace the MSS in proportions ranging from 0 to 100% at an increment of 25%. The mechanical performance of the ECC mixtures was assessed in terms of the compressive, tensile, and flexural properties. The results obtained from this study showed that the use of RC as a partial replacement of MSS in ECC mixtures resulted in a satisfactory ECC mixture. However, at a replacement ratio of 75% and above, the performance of ECC may not be acceptable. The sustainability index assessment of the mixtures indicates that the use of RC as a replacement of up to 50% of MSS is optimum.
May 1, 2021
Dong Li, Liu Jin, and Xiuli Du
The concept of global size effect theory from material level to structural level is raised. The material level is described by a Universal Morphological Model (UMM) that accounts for the size effect behaviors introduced by the mixture variables of concrete, whereas the structural level is linked to the size effect theory based on quasi-brittle fracture mechanics. First, the UMM that is eligible for the description of material-level size effect is established and verified. Parametric study on the UMM shows that the mechanical properties of concrete are insensitive to the maximum aggregate size (MAS) at a critical interface crack index ηc. Secondly, by introducing the UMM into the formulation of structural-level size effect, a global size effect model (GSEM) expressed as a variant for the Type-2 size effect model (SEM) is proposed. Parametric study on the GSEM shows that the properties and the scales of mesostructures have significant influences on the size effect behaviors of concrete at the structural level. The critical interface crack index ηc determined by the UMM should receive sufficient attention in large-scale structural concrete design in practice.
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