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International Concrete Abstracts Portal

Showing 1-5 of 838 Abstracts search results

Document: 

18-512

Date: 

July 1, 2020

Author(s):

Mahdi Valipour and Kamal H. Khayat

Publication:

Materials Journal

Volume:

117

Issue:

4

Abstract:

Ultra-high-performance concrete (UHPC) can be vulnerable to variations in materials properties and environmental conditions. In this paper, the sensitivity of UHPC to changes in mixing, casting, curing, and testing temperatures ranging between 10 and 30 ± 2°C (50 and 86 ± 3.5°F) was investigated. The investigated rheological properties, mechanical properties, and shrinkage of UHPC are shown to be significantly affected by temperature changes. UHPC made with either binary or ternary binder containing fly ash (FA) or slag cement exhibited greater robustness than mixtures prepared with 25% silica fume. UHPC made with 60% FA necessitated the lowest high-range water-reducing admixture demand. With temperature increase, the yield stress of UHPC mixtures increased by up to 55%, and plastic viscosity decreased by up to 45%. This resulted in accelerating initial and final setting times by up to 4.5 and 5 hours, respectively. The increase of temperature from 10 to 30 ± 2°C (50 ± to 86 ± 3.5°F) led to a 10 to 75% increase in compressive, splitting tensile, and flexural strengths and modulus of elasticity and 15 to 60% increase in autogenous shrinkage.

DOI:

10.14359/51724613


Document: 

19-328

Date: 

July 1, 2020

Author(s):

Jedadiah F. Burroughs, Charles A. Weiss Jr., John E. Haddock, and W. Jason Weiss

Publication:

Materials Journal

Volume:

117

Issue:

4

Abstract:

This study presents the application of an analytical model to describe the rheological behavior of cement pastes containing silica fume at replacement rates of up to 30% by mass. The analytical model hypothesizes how water interacts with particles in a cementitious system. The coating thickness of water surrounding each particle in the system is estimated. This coating thickness is shown to correlate strongly with measured rheological properties when fit to the Herschel-Bulkley model. To calculate coating thickness, it is necessary to account for the water absorbed by nonhydraulic components in the system, whether aggregate, supplementary cementitious materials, or mineral. The results suggest that silica fume particles may be absorptive, and this absorption capacity, although small, must be considered when designing water-starved cementitious materials. The experimental investigation involved the rheological testing of three water-binder ratios (0.20, 0.30, 0.45), three silica fume replacement levels (10%, 20%, 30%), and eight different silica fume products.

DOI:

10.14359/51724626


Document: 

18-320

Date: 

May 1, 2020

Author(s):

Colin B. Van Niejenhuis, Ibrahim G. Ogunsanya, and Carolyn M. Hansson

Publication:

Materials Journal

Volume:

117

Issue:

3

Abstract:

The pore solution expressed from 28-day cement pastes was analyzed as part of a wider research program investigating the corrosion behavior of stainless-steel reinforcing bars in concrete, using inductively coupled plasma and ion chromatography techniques. The pastes were prepared with different water-cementitious materials (binder) ratios (w/cm), portland cement with and without supplementary cementitious materials (SCMs), and with admixed sodium chloride in the range typical of the threshold values for stainless steel reinforcement. The major anion and cation concentrations are given, showing the influence of admixed chloride on the amount of chloride retained in solution and of sulfate released into the pore solution. The results are discussed in terms of the initial compositions of the cementitious materials and their effect on chloride binding.

DOI:

10.14359/51724590


Document: 

18-417

Date: 

May 1, 2020

Author(s):

Kamran Amini, Kristen Cetin, Halil Ceylan, and Peter C. Taylor

Publication:

Materials Journal

Volume:

117

Issue:

3

Abstract:

This paper compiles results from three different laboratory studies and employs multivariate regression analyses to model the effect of mixture parameters and concrete hardened properties on saltscaling performance. The correlations between concrete hardened properties and mixture proportions were also studied. The modeled mixture parameters included water-cementitious materials ratio (w/cm), slag cement, and air content. Concrete performance was evaluated through abrasion resistance, sorptivity, compressive strength, and salt scaling tests. According to the results obtained in this study, concrete scaling performance is affected, in the order of importance, by w/cm, slag-cement replacement, and air content. In addition, concrete hardened properties, especially abrasion resistance, were found useful in making reliable salt-scaling predictions. Based on the results derived from the regression analyses and the discussions provided in the reviewed literature, recommendations are given for proportioning of concrete to obtain adequate performance with respect to compressive strength, abrasion resistance, sorptivity, and salt-scaling resistance. In addition, the relationship between concrete properties, ingredients, and effective mechanisms are investigated.

DOI:

10.14359/51724614


Document: 

19-095

Date: 

March 1, 2020

Author(s):

Sikiru Folahan Oritola, Abdul Latif Saleh, and Abdul Rahman Mohd Sam

Publication:

Materials Journal

Volume:

117

Issue:

2

Abstract:

Iron ore tailings (IOTs) are common industrial solid waste products which are generated in enormous quantities during the production process of iron ore. By visual observation, this material shows some similarity with natural sand (NS); it was therefore desired to characterize the IOTs to further ascertain their use in concrete. Five types of IOTs obtained from different locations were characterized using microscopic and physical examination techniques. These methods were used to assess the structure and properties of IOTs, subsequently comparing it with that of NS. The surface image of the materials is provided and numerical information, such as the relative concentrations of atoms that comprise the materials, is also indicated. Subsequently, the structure and composition of the IOT materials are identified for possible applications in the construction industry.

DOI:

10.14359/51720305


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