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Topics In Concrete
Home > Publications > International Concrete Abstracts Portal
Showing 1-5 of 113 Abstracts search results
Document:
23-329
Date:
December 1, 2024
Author(s):
S. Al-Fadala, D. Dashti, H. Al-Baghli, J. Chakkamalayath, and Z. Awadh
Publication:
Materials Journal
Volume:
121
Issue:
6
Abstract:
Compared to external curing, internal curing enables the judicious use of available water to provide additional moisture in concrete for more effective hydration and improvement in the performance of concrete structures. However, certain challenges with the incorporation of internal curing materials (ICMs) still need to be addressed, as their effectiveness depends on several factors. Furthermore, sustainable construction demands the use of recycled materials, and this paper discusses the comparative evaluation of recycled aggregate (RA) as an ICM, along with two other types of ICMs, on various properties of high-performance concrete in the hardened state under two curing conditions. Concrete mixtures were prepared with pre-wetted RAs, superabsorbent polymers (SAPs), and pre-wetted lightweight volcanic aggregates (LWVAs) as ICMs. Concrete performance was compared through the investigation of the strength development, shrinkage, mass loss, and volumetric water absorption. In addition, the change in internal humidity of concrete with time at different stages of hardening was determined. The compressive strength results showed that RA and LWVA are more efficient in early days, and the performance of SAP is better in the later age due to its slow water releasing capabilities. Compared to the control mixture, the least reduction in strength of 4% and 8% at 28 days and 90 days, respectively, could be observed for the mixtures containing RA under both air and water curing.
DOI:
10.14359/51742261
23-326
J. Yan, Y. Luo, L. Feng, H. Zhang, W. Weng, B. Yang, J. Li, Y. Zhuang, J. Zuo, C. Liang, X. Wang, and J. Xie
To make full use of recycled aggregate concrete (RAC), carbon fiber (CF) and nano-metakaolin (NMK) were mixed into RAC to improve its mechanical properties and microstructure. The effects of NMK content, CF content, recycled aggregate (RA) replacement rate, and CF length on the compressive strength, splitting tensile strength, and tension-compression ratio of RAC were studied by the orthogonal test method; then, the test results were analyzed. The results show that the NMK content and RA replacement rate have significant effects on the compressive strength of RAC, while the CF content has significant effects on the splitting tensile strength and the tension-compression ratio. Through the synergistic effect of NMK and CF, the pore structure characteristics of RAC are improved, and the bond strength of the interfacial transition zone (ITZ) of CF-mortar is increased, which further enhances the strengthening effect of CF; thus, the mechanical properties of RAC are continuously enhanced.
10.14359/51743286
23-293
November 22, 2024
Tohid Asheghi Mehmandari, Mehdi Shokouhian, Meysam Imani, Kong Fah Tee, Ahmad Fahimifare
This study investigates the behavior of recycled steel fibers recovered from waste tires (RSF) and industrial hooked-end steel fibers (ISF) in two single and hybrid reinforcing types with different volume content, incorporating microstructural and macrostructural analyses. Scanning electron microscopy (SEM) is used to study the microstructure and fractures, focusing on crack initiation in the fiber interface transition zone (FITZ). The macrostructural analysis involves using digital image correlation (DIC) software, Ncorr, to analyze the split tensile behavior of plain and FRC specimens, calculating strain distribution, and investigating crack initiation and propagation. The SEM study reveals that industrial fibers due to the presence of hooked ends promoted improved mechanical interlocking, anchors within the matrix, frictional resistance during crack propagation and significantly improved load transfer have better bonding, crack bridging, and crack deflection compared to recycled fibers. Recycled steel fibers significantly delay crack initiation and enhance strength in the pre-peak zone. The study suggests hybridizing recycled fibers from automobile tires with industrial fibers as an optimum strategy for improving tensile performance and utilizing environmentally friendly materials in FRC.
10.14359/51744375
23-229
September 1, 2024
Lautaro Santillan, Claudio Zega, and Edgardo F. Irassar
5
The attached cement paste in recycled concrete (RC) aggregateleads to its potential reactivity against sulfate ions. Several testmethods were evaluated to find a suitable, reliable, and accuratemethod to evaluate the potential reactivity of aggregates. Differentquality RC aggregates were used to apply those methods. Thestudies included evaluations of concrete cores drilled from sourceconcrete (SC), RC aggregates, recycled mortar bars under differentexposures, and RC prisms exposed to external sulfate attack (ESA).The concrete core test allowed qualifying SC as potentially reactiveagainst sulfate in a short time. Tests on recycled aggregates andrecycled mortar bars showed variable sensitivity levels. Resultsfrom concrete prisms showed an effective reactivity of recycledaggregates when the replacement is higher.
10.14359/51742039
23-194
Md. Shahjalal, Kamrul Islam, Mohammad Tiznobaik, M. Shahria Alam, and Raquib Ahsan
Structural Journal
The concrete industry is increasingly adopting the production of environmentally sustainable green concrete. Using recycled coarse aggregate (RCA) produced from demolished concrete infrastructures and waste tire-derived crumb rubber (CR) in the concrete mixture provides a sustainable construction practice and can enhance structural performance. This study investigates the uniaxial compressive behavior of concrete columns composed of RCA, CR, and polypropylene (PP) fiber. A total of 26 columns 150 x 150 x 950 mm in size were tested under uniaxial compression loading. Test parameters included longitudinal reinforcement ratio (0, 1.4, and 2.0%), tie spacing (75 and 150 mm), CR content (0, 5, 10, and 15% of the volume of natural fine aggregate), and percentage of PP fiber (0 and 0.5% of the volume of the total mixture) with 30% RCA replacement (by weight of natural coarse aggregate). The compressive behavior, failure mechanism, influence of longitudinal and transverse reinforcement, dilation, ductility, and toughness were examined. This study demonstrated that incorporating fiber into the concrete made with RCA and CR waste materials improved the axial capacity, resulting in fiber-reinforced rubberized recycled concrete (FRRC) columns with enhanced ductility and toughness. These findings support the development of sustainable concrete for structural columns, justifying their applicability to existing design codes.
10.14359/51740860
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