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International Concrete Abstracts Portal

Showing 1-5 of 887 Abstracts search results

Document: 

21-175

Date: 

July 1, 2022

Author(s):

Amirmozafar Benshams, Farzad Hatami, and Mesbah Saybani

Publication:

Materials Journal

Volume:

119

Issue:

4

Abstract:

Shape memory alloys (SMAs), with their unique ability to undergo large deformations and recover to their initial shapes through the removal of stress without significant residual strain, have become attractive materials in bridge engineering. In this study, nine samples of bridge piers are reinforced by two types of SMA (NiTi and Cu-Al-Mn) in plastic hinge regions where high-performance fiber-reinforced concrete (HPFRC) is additionally used to enhance the ductility of piers. To investigate the effects of SMAs and HPFRC on seismic performance of concrete bridge piers, 28 near-field ground-motion record pairs are selected. Then, the models are analyzed using the incremental dynamic analysis (IDA) method and fragility curves are derived. The results show that using SMAs leads to the reduction of residual drift. Also, using HPFRC increases the capacity of the models. Furthermore, the model with HPFRC and NiTi shows the best performance in terms of capacity and residual drift reduction.

DOI:

10.14359/51734685


Document: 

21-157

Date: 

July 1, 2022

Author(s):

Junhao Chen, Yanlong Li, Lifeng Wen, Hanyu Guo, and Kangping Li

Publication:

Materials Journal

Volume:

119

Issue:

4

Abstract:

The objective of this paper is to investigate the microscopic pore characteristics and macroscopic mechanical properties of concrete under different curing conditions. Ultrasonic nondestructive testing technology was used to measure the ultrasonic sound velocity of specimens of different ages, and the compressive strength and splitting tensile strength were obtained through indoor mechanical performance tests. The pore-size distribution characteristics and internal microstructure were observed using nuclear magnetic resonance (NMR) technology and scanning electron microscopy (SEM) testing, respectively. The results revealed that, compared with standard curing conditions, the decrease of the curing temperature and humidity can result in the volume and proportion of macropores and microcracks being larger, which results in the deceleration of the ultrasonic wave speed inside the concrete and the decrease of the mechanical properties. Under the same curing condition, a lower water-binder ratio (w/b) enables the internal pore surface area of the material to increase, and the mechanical properties are improved. With the decrease of the curing temperature and relative humidity, the stress-strain curve appeared delayed in the initial compaction stage and presents more obvious brittleness characteristics in the failure stage. By fitting the relationship between the concrete strength and the porosity under different curing conditions, an extended model that can be applied to cement-based materials was obtained. Additionally, it was found that the porosity is negatively correlated with the ratio of the compressive strength to splitting tensile strength of the concrete.

DOI:

10.14359/51734683


Document: 

21-273

Date: 

July 1, 2022

Author(s):

Mohit Agarwal and Enrique del Rey Castillo

Publication:

Materials Journal

Volume:

119

Issue:

4

Abstract:

The use of industrial waste in concrete and controlled low-strength mixtures (CLSM) along with the experimental analysis of the fresh and hardened properties was investigated in this research. Four waste materials were used to design 17 mixtures. Fly ash and glass powder were investigated at high rates of replacement for cement, from 60 to 90%. This information is scarce in published literature and can help practitioners and concrete batchers in developing mixtures with a high level of replacement. Additionally, natural sand was substituted by glass sand which, in combination with fly ash and glass powder as cement replacement, provides an entirely new body of knowledge of concrete mixtures that use limited newly produced materials. Adequate strength and flowability was achieved with the use of recycled waste materials for both normal concrete and CLSM. All normal concrete mixtures except one, which had a 90% fly ash replacement, achieved a 28-day compressive strength of at least 29 MPa. Concrete with this compressive strength has multiple applications that represent a significant portion of the concrete produced. Using these mixtures has the potential to significantly reduce the amount of virgin products, especially cement that has a significant carbon footprint. All CLSM mixtures except two had a compressive strength of less than 2 MPa, therefore meeting the walkability and excavability requirements as set out in American Concrete Institute (ACI) guidelines and codes. Finally, an equation was proposed to predict the 28-day compressive strength of concrete with high volumes of fly ash replacement (>60%). As far as the authors are aware, there is no method to calculate the compressive strength of this type of concrete. This equation represents a significant contribution not only to the research body but also to practitioners and concrete batchers.

DOI:

10.14359/51734687


Document: 

21-396

Date: 

July 1, 2022

Author(s):

Huayuan Zhong and Henry E. Cardenas

Publication:

Materials Journal

Volume:

119

Issue:

4

Abstract:

Electrokinetic nanopozzolan treatment of cementitious materials has proven to be beneficial for improving durability and rehabilitation outcomes through significant porosity reduction. This study investigated process parameters that enabled control of particle transport effectiveness and cost efficiency as applied to ordinary portland hardened cement paste (HCP). The most significant strength enhancement achieved in this study was 35%, which was provided by a 22 nm silica nanoparticle. This treatment produced a porosity reduction from 25 to 18%. The cost of using this particle was a factor of 2 to 6 lower than the other candidates. An innovative electrode setup was developed to help reduce the particle instability associated with electrolysis-induced pH increases. This new method enabled the use of electric field values that allowed for current densities as high as the concrete damage threshold of 1 A/m2.

DOI:

10.14359/51734730


Document: 

21-366

Date: 

May 1, 2022

Author(s):

Sara Seyedfarizani, Basem H. AbdelAleem, and Assem A. A. Hassan

Publication:

Materials Journal

Volume:

119

Issue:

3

Abstract:

This study aimed to investigate the effect of different curing conditions/temperatures on the compressive strength, flexural strength (FS), modulus of elasticity (ME), and abrasion resistance of concrete developed with different mixture compositions. The studied parameters included different water-binder ratios (w/b) (0.4 and 0.55), different coarse-to-fine aggregate ratios (C/F) (0.7 and 1.2), addition of steel fibers (SFs), and different supplementary cementitious materials (SCMs) (metakaolin [MK] and silica fume [SLF]). The developed mixtures were cured at four different curing conditions: moist curing (C1); air curing (C2); and cold curing, including +5°C curing (C3) and –10°C curing conditions (C4). The results indicated that the effect of curing concrete samples at cold curing conditions was more pronounced on FS results compared to all other mechanical properties results, in which the FS reduced by 23% and 41% at +5°C and –10°C curing conditions, respectively, compared to at the moist-curing condition. Despite the considerable enhancement in the mechanical properties and abrasion resistance when SFs or SCMs were used in the mixtures, cold curing of mixtures with SCMs or SFs significantly reduced this enhancement. The results also revealed that the rotating-cutter test results of the mixture with SFs were more affected by cold curing conditions than the sandblasting test results.

DOI:

10.14359/51734619


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