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International Concrete Abstracts Portal

Showing 1-5 of 73 Abstracts search results

Document: 

22-380

Date: 

March 15, 2024

Author(s):

Changhui Jin, Ningshan Jiang, Hui Li, Chengkui Liu, Aoxiang Cao Jianing Wang , Xiaochu Wen

Publication:

Materials Journal

Abstract:

The use of construction waste to prepare recycled micro powder can improve the utilization of construction waste resources and effectively reduce carbon emissions. In this paper, researchers used waste concrete processing micro powder to prepare foam concrete and quantitatively characterized the performance and pore structure of foam concrete by SEM, PCAS, and mechanical property testing methods with different mixing ratios of micro powder, the results showed that: The effect of single mixing of micro powder or fly ash is better than the composite mixing test, and the optimal proportion of compressive strength of single mixing of micro powder is higher than that of single mixing of fly ash. The optimum mixing ratio is 6:4 between cement and micro powder, and the best effect is achieved when the micro powder mixing amount is 40%. Single or double mixing can fill the pores between the foam and strengthen the performance of the substrate. The test of single-mixed or compound-mixed micro powder showed that the fractal dimension decreased with the increase of porosity; the fractal dimension of the specimen increased, the average shape factor became smaller, the compressive strength decreased, and the water absorption rate increased.

DOI:

10.14359/51740703


Document: 

22-260

Date: 

January 1, 2024

Author(s):

Amit Kumar, Gyani Jail Singh, Priyanshu Raj, and Rajesh Kumar

Publication:

Materials Journal

Volume:

121

Issue:

1

Abstract:

This research examines the performance of quality-controlled recycled concrete aggregates (QRAs) with fly-ash-based cement. Compared to concrete made from untreated recycled concrete aggregates (URC), quality-controlled recycled aggregate concrete (QRC) has superior physical, mechanical, and durability properties. Except for sorptivity, the physical, mechanical, and durability properties of QRC are almost identical to those of natural aggregate concrete (NC). The compressive strength, splitting tensile strength, flexural strength, fracture energy, and modulus of elasticity of QRC are higher than those of URC by 18.0%, 16.8%, 60.0%, 27.17%, and 43.46%, respectively. The abrasion resistance of QRC is approximately 60% higher than URC. Scanning electron microscope (SEM) image and energy-dispersive X-ray (EDX) analysis prove that quality control produces denser old interfacial transition zones (OITZ) with fewer microvoids. The QRA improves not only the pore structure but also the weak mortar structure attached to the aggregate. There is also a strong correlation between the compressive strength and splitting tensile strength, flexural strength, fracture energy, and modulus of elasticity of QRC. QRA can be used to compute the mixture proportions for concrete (certainly up to medium-strength concrete) according to either the Indian standard or the international standard. It is challenging to improve the sorptivity of recycled concrete aggregates closer to NC. In addition, QRC has an initial sorptivity of two times (initial) and a final sorptivity of 1.8 times higher than NC, whereas URC has an initial sorptivity of 3.5 times (initial) and a final sorptivity of 2.35 times higher than NC.

DOI:

10.14359/51740259


Document: 

22-124

Date: 

September 1, 2023

Author(s):

Arindam Dey, Tara L. Cavalline, Miras Mamirov, and Jiong Hu

Publication:

Materials Journal

Volume:

120

Issue:

5

Abstract:

The use of recycled concrete aggregates (RCAs) in lieu of natural aggregates improves the sustainability of the built environment. Barriers to the use of RCA include its variable composition, including the residual mortar content (RMC), chemical composition, and its potential to contain contaminants, which can negatively affect the properties of concrete or present environmental concerns. In this study, a rapid, economical method to estimate the RMC and provide the chemical characterization of RCA was developed using a portable handheld X-ray fluorescence (PHXRF) device. Models were developed using reference tests (RMC test based on the thermal shock method and chemical composition from whole-rock analysis) to correlate PHXRF results to measured values. The PHXRF shows strong potential for estimating the RMC and chemical composition of RCA. Paired with locally calibrated reference samples, the test method could be used in laboratory or field applications to characterize RCA and increase its use in bound and unbound applications.

DOI:

10.14359/51738890


Document: 

22-265

Date: 

May 1, 2023

Author(s):

Haikuan Wu, Chao Zhao, Zhao Zhang, Shun Kang, and Changwu Liu

Publication:

Materials Journal

Volume:

120

Issue:

3

Abstract:

In rare-earth mining projects, ammonium sulfate (AS) solution has a great impact on the concrete structure, which often causes serious damage to the structure. To improve the corrosion resistance of concrete in AS solution, recycled plastic was used to replace concrete fine aggregate. Compared with normal concrete (NC), the deterioration mechanism of recycled plastic concrete (RPC) against the corrosion of AS solution (3, 5, and 7%) was studied. Through the tests and analysis of apparent morphology, relative mass, ultrasonic wave velocity, and compressive strength—as well as scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR)—of corroded concrete, the test results indicate that many spots and corner damage occurred in the early and later stages of corroded concrete, respectively. The corrosion reaction of AS solution produced more ettringite and gypsum, resulting in serious damage. The RPC was expansive under the corrosion of AS solution, and the expansion degree was greater than that of NC. The compressive strength of RPC decreased gradually in AS solution. The corrosion deterioration mechanism of RPC was revealed by microstructure and phase analysis.

DOI:

10.14359/51738687


Document: 

22-057

Date: 

January 1, 2023

Author(s):

N. P. Kannikachalam, D. di Summa, R. P. Borg, E. Cuenca, M. Parpanesi, N. De Belie, and L. Ferrara

Publication:

Materials Journal

Volume:

120

Issue:

1

Abstract:

This research focuses on the evaluation of the sustainability of recycled ultra-high-performance concrete (R-UHPC) in a life cycle analysis (LCA) perspective, and with reference to a case study example dealing with structures exposed to extremely aggressive environments. This involves the assessment of the self-healing capacity of R-UHPC, as guaranteed by the R-UHPC aggregates themselves. Recycled aggregates (RA) were created by crushing 4-month-old UHPC specimens with an average compressive strength of 150 MPa. Different fractions of recycled aggregates (0 to 2 mm) and two different percentages (50 and 100%) were used as a substitute for natural aggregates in the production of R-UHPC. Notched beam specimens were pre-cracked to 150 μm using a three-point flexural test. The autogenous self-healing potential of R-UHPC, stimulated by the addition of a crystalline admixture, was explored using water absorption tests and microscopic crack healing at a pre-determined time (0 days, 1 month, 3 months, and 6 months) following pre-cracking. Continuous wet/ dry healing conditions were maintained throughout the experimental campaign. The specimens using R-UHPC aggregates demonstrated improved self-healing properties to those containing natural aggregates, especially from the second to the sixth month. To address the potential environmental benefits of this novel material in comparison to the conventional ones, an LCA analysis was conducted adopting the 10 CML-IA baseline impact categories, together with a life cycle cost (LCC) analysis to determine the related economic viability. Both LCA and LCC methodologies are integrated into a holistic design approach to address not only the sustainability concerns but also to promote the spread of innovative solutions for the concrete construction industry. As a case study unit, a basin for collection and cooling of geothermal waters was selected. This is representative of both the possibility offered, in terms of structural design optimization and reduction of resource consumption, and of reduced maintenance guaranteed by the retained mechanical performance and durability realized by the self-healing capacity of R-UHPC.

DOI:

10.14359/51737336


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