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International Concrete Abstracts Portal

Showing 1-5 of 242 Abstracts search results

Document: 

20-254

Date: 

March 1, 2021

Author(s):

Vineet Shah and Allan Scott

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

Magnesium silicate hydrate (M-S-H) formed by the reaction between magnesium oxide and amorphous silica in water imparts strength-binding characteristics similar to that of portland cement (PC). Analysis of both the mechanical and durability parameters of MgO-SiO2 binder is essential for its adoption as an alternative cementitious material. This study investigates the mechanical and transport properties of MgO-SiO2 binder concrete. Silica fume and metakaolin were used as amorphous silica sources in the binder. The implications of the addition of magnesium carbonate in MgO-SiO2 binder concrete was also investigated. Along with the compressive strength, other hardened properties of concrete including elastic modulus, shrinkage, porosity, sorptivity, permeability, and resistivity were measured at 7, 28, and 90 days. The overall performance of the concrete was improved through the use of metakaolin instead of silica fume in terms of compressive strength, elastic modulus, and shrinkage. The transport properties of the magnesium oxide and metakaolin mixture were found to be better or similar compared to PC, which was attributed to the refined pore structure and lower porosity. The addition of magnesium carbonate further helped to improve the overall performance of the concrete through likely the formation of hydrotalcite type phases.

DOI:

10.14359/51730418


Document: 

20-166

Date: 

March 1, 2021

Author(s):

Jiayin Tao, Rita Maria Ghantous, Ming Jin, and Jason Weiss

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

The objective of this study is to determine whether the addition of silica fume (SF) can accelerate a reduction in the degree of saturation (DOS) of sealed cementitious materials at early ages, thereby increasing the freezing-and-thawing (F-T) resistance of the paste. This study investigated the influence of SF on the F-T resistance of cementitious materials using two techniques. The first technique consists of quantifying the DOS of cementitious materials at early ages and compares it to the critical degree of saturation (DOSCR). The second technique consists of determining the difference in the length of the cement paste sample before and after exposure to an F-T cycle at early ages. The change in length during the F-T cycle is an indicator of the development of damage caused by F-T. The DOS decreases faster when a higher amount of SF replaces cement. Consequently, the DOS of SF cement paste samples are more likely to be below DOSCR faster than plain cement paste samples when the samples are sealed.

DOI:

10.14359/51730414


Document: 

20-222

Date: 

March 1, 2021

Author(s):

M. R. Sakr and M. T. Bassuoni

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

The response surface method, a statistical modeling approach, was used to assess the influence of water-binder ratio (w/b), binder content, and dosages of supplementary cementitious materials on the performance of 52 mixtures under accelerated physical salt attack (PSA). The test protocol simulated partially embedded elements. Also, the PSA damage of concrete was mapped by regression analysis based on combination of performance-based parameters. Mineralogical, thermal, and microstructural analyses were conducted to elucidate the bulk trends obtained from the models. Multi-objective optimization was also performed to determine optimal combinations of parameters (w/b; binder content; and dosages of fly ash, slag, and silica fume) producing mixtures resistant to PSA. In addition, a classification for the resistance of concrete to PSA based on performance indicators (mechanical capacity and wicking factor) was proposed.

DOI:

10.14359/51730515


Document: 

18-308

Date: 

January 1, 2021

Author(s):

M. Almarshoud, H. Mosavi, R. Alrashidi, M. H. M. Alyami, C. C. Ferraro, H. D. DeFord, and K. A. Riding

Publication:

Materials Journal

Volume:

118

Issue:

1

Abstract:

In this study, the concrete penetrability properties were measured for both the older test methods and the new resistivity-based test methods. To consider different materials, four types of cement were used, including an ASTM C150/C150M Type I/II low alkali cement, Type V cement, Type I cement with high alkali content, and an ASTM C595/C595M Type IL cement. Silica fume, slag cement, Class F fly ash, and metakaolin were used as supplementary cementitious material (SCM) in binary and ternary blends with different replacement ratios to evaluate the correlation between electrical and transport properties. The tests included AASHTO TP 119 for bulk resistivity, AASHTO T 358 for surface resistivity measurement, rapid chloride permeability test (ASTM C1202/C1202M), rapid chloride migration test (NT Build 492), concrete water absorption rate (ASTM C1585/C1585M), concrete volume of permeable voids (ASTM C642/C642M), and a constant-head water permeability test. The results showed good correlation between the electrical-based tests and water permeability, but poor correlation between the electrical-based tests and the volume of permeable voids.

DOI:

10.14359/51729334


Document: 

20-085

Date: 

January 1, 2021

Author(s):

Mohammed Farooq and Nemkumar Banthia

Publication:

Materials Journal

Volume:

118

Issue:

1

Abstract:

The influence of factors such as cementitious matrix characteristics, fiber inclination, and temperature on the interfacial bond between fiber-reinforced polymer (FRP) fibers and cementitious matrix are studied herein. It was noticed that use of glass fibers in the form of glass FRP (GFRP) composite fiber greatly improved the bonding mechanism over using just constituent glass fibers. With matrix maturity, a steady increase in bond was observed with over 60% bond strength achieved within a day. Densification of the cementitious matrix with the addition of silica fume was found to greatly increase the interfacial bond and changed the failure mode from fiber pullout to fiber rupture and delamination. At inclined loading as well, a different failure mode in the form of fiber rupture after partial pullout was noticed. This change in failure mode from fiber pullout to fiber rupture was also accompanied by a lower apparent tensile strength at large inclination. At lower temperature of –20°C, the bond between FRP fibers and the cement matrix was found to improve, but increased brittleness in fibers was also noted. At higher temperatures, FRP fibers performed satisfactorily up to 80°C, after which a gradual degradation in bond was observed.

DOI:

10.14359/51725996


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