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International Concrete Abstracts Portal

Showing 1-5 of 153 Abstracts search results

Document: 

23-101

Date: 

February 8, 2024

Author(s):

Le Teng, Alfred Addai-Nimoh, Kamal H. Khayat

Publication:

Materials Journal

Abstract:

This study evaluates the potential to use shrinkage-reducing admixture (SRA) and pre-saturated lightweight sand (LWS) to shorten the external moist curing requirement of ultra-high-performance concrete (UHPC), which is critical in some applications where continuous moist curing is challenging. Key characteristics of UHPC prepared with and without SRA and LWS and under 3 days, 7 days, and continuous moist curing were investigated. Results indicate that the combined incorporation of 1% SRA and 17% LWS can shorten the required moist curing duration since such mixture under 3 days of moist curing exhibited low total shrinkage of 360 µε at 56 days and compressive strength of 135 MPa (19,580 psi) at 56 days and flexural strength of 18 MPa (2,610 psi) at 28 days. This mixture subjected to 3 days of moist curing also had a similar hydration degree and 25% lower capillary porosity in paste compared to the Reference UHPC prepared without any SRA and LWS and under continuous moist curing. The incorporation of 17% LWS promoted cement hydration and silica fume pozzolanic reaction to a degree similar to extending the moist curing duration from 3 to 28 days and offsetting the impact of SRA on reducing cement hydration. The lower capillary porosity in the paste compensated for the porosity induced by porous LWS to secure an acceptable level of total porosity of UHPC.

DOI:

10.14359/51740566


Document: 

23-191

Date: 

February 8, 2024

Author(s):

Pouria Mohsenzadeh Tochahi, Gholamreza Asadollahfardi, Seyed Fazlullah Saghravani, Niloofar Mohammadzadeh

Publication:

Materials Journal

Abstract:

In marine structures, concrete requires adequate resistance against chloride ion penetration. As a result, numerous studies have been conducted to enhance the mechanical properties and durability of concrete by incorporating various pozzolans. This research has investigated the curing conditions of samples including zeolite and metakaolite mixed with Micro nanobubble water in artificial seawater and standard conditions. The results indicated that incorporating zeolite and metakaolin mixed with Micro nanobubble water, which was cured in artificial seawater conditions, compared to similar samples that were cured in standard conditions, improved the mechanical properties and durability of concrete samples. The compressive strength of 28 days concrete samples containing 10% metakaolin mixed with 100% Micro nanobubble water and samples consisting of 10% zeolite blended with 100% Micro nanobubble water cured in seawater in comparison to the control sample cured in the standard condition indicated an increase of 25.06% and 20.9%, respectively. The most results were obtained with a compound of 10% metakaolin, and 10% zeolite with 100% Micro nanobubble cured in seawater (MK10Z10NB100CS) which rose significantly Compressive, Tensile and Flexural Strength by 11.13, 14, and 9.1%, respectively, in comparison with to the MK10Z10NB100 sample cured in the standard condition. Furthermore, it decreased considerably 24-hr water absorption and Chloride Penetration at 90 days by 27.70 and 82.89%, respectively, in comparison with the control sample cured in standard conditions.

DOI:

10.14359/51740567


Document: 

22-277

Date: 

July 1, 2023

Author(s):

Keshav Bharadwaj, O. Burkan Isgor, and W. Jason Weiss

Publication:

Materials Journal

Volume:

120

Issue:

4

Abstract:

As the number of potential supplementary cementitious materials (SCMs) increase, there is a need to determine their reactivity. Most recent methods to assess pozzolanic reactivity are based on measuring certain outputs such as heat release (Q), calcium hydroxide (CH) consumption, and nonevaporable water. This paper uses thermodynamic modeling to aid in the interpretation of these tests and the quantification of reactivity. It is shown that pozzolanic reactivity should be interpreted based on the SCM type. The presence of sulfates and carbonates during reactivity quantification alter the reaction of the Al2O3 phases, making the interpretation of the reactivity test results challenging. The reactivity of commercial SCMs should be interpreted specific to the type of SCM as described by ASTM International/AASHTO. A proposed interpretation for commercial SCMs is provided in this paper.

DOI:

10.14359/51738817


Document: 

22-163

Date: 

May 1, 2023

Author(s):

Rimvydas Kaminskas, Irmantas Barauskas, and Edvinas Kazlauskas

Publication:

Materials Journal

Volume:

120

Issue:

3

Abstract:

The main objective of this study was to investigate the possibility of using a mixture of two different wastes—spent catalyst from the oil cracking process and spent smectite clay from the alimentary oil bleaching process—as supplementary cementitious materials (SCMs). The spent catalyst was used as received, and the smectite clay waste was further thermally activated at 600°C. Both wastes were found to contain amorphous compounds and to have good pozzolanic activity. Fifteen wt. % of portland cement was replaced by these wastes mixed in different proportions. It was found that the additives from a mixture of these wastes accelerated the early hydration of the cement in a complex manner. The smectite clay component promotes the hydration reactions of calcium silicates, while the catalyst component activates the reaction of the aluminate-bearing phase. A similar complex trend was found for the compressive strength of the samples: the higher compressive strength of the cement samples produced the catalyst component at shorter periods of hydration, but as the duration of hydration increased to 28 days, a smectite clay component began to impart greater compressive strength. The mixture of 70 wt. % spent catalyst and 30 wt.% smectite clay waste was found to have the best strength properties, and up to 20 wt. % portland cement could be replaced using these admixtures.

DOI:

10.14359/51738684


Document: 

22-067

Date: 

March 1, 2023

Author(s):

Garima Rawat, Sumit Gandhi, and Yogesh Iyer Murthy

Publication:

Materials Journal

Volume:

120

Issue:

2

Abstract:

The current paper investigates the effects of partial cement replacement with nano-titanium dioxide (nano-TiO2 [NT]) in varying weight proportions in concrete. In the C20/25 grade of concrete, NT was added by weight of cement with partial replacement of 0, 0.5, 1.5, 2.0, 2.5, and 3.0% using portland pozzolana cement. The physical and mechanical properties of the resulting concrete were assessed, as well as aspects of durability such as sorptivity and nondestructive tests (NDT) such as ultrasonic pulse velocity (UPV). Compared with the control mixture, the fresh concrete produced showed a drastic reduction in slump with increasing percentage of replacement, with a 54% reduction at a 3.0% replacement. Furthermore, for 1.5% NT, the compressive, flexural, and splitting tensile strengths peaked at 7, 28, 56, and 90 days, after which the values decreased. The addition of NT improved the homogeneity and integrity of the resulting concrete based on the UPV values. As the percentage of NT increased, chloride penetration decreased. From microstructural studies, it can be concluded that NT acts as a filler material and can be used as a partial replacement for cement in concrete up to 2% by weight.

DOI:

10.14359/51738490


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