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International Concrete Abstracts Portal

Showing 1-5 of 29 Abstracts search results

Document: 

20-052

Date: 

January 1, 2021

Author(s):

Adeyemi Adesina and Sreekanta Das

Publication:

Materials Journal

Volume:

118

Issue:

1

Abstract:

The use of cementitious composites reinforced with fibers as repair materials for concrete pavements is gaining huge attention recently due to their enhanced mechanical and durability properties. However, the use of portland cement as the main binder of these composites still poses a serious sustainability issue. The production of portland cement has been associated with the high use of raw materials and the emission of carbon dioxide into the environment. On the other hand, alkali-activated binders exist that are capable of eliminating portland cement totally. However, the activators currently used to activate these types of materials are expensive and extremely corrosive. Therefore, this study used hydrated lime, which is a less expensive, less corrosive, and eco-friendly alternative activator to produced fiber-reinforced alkali-activated composites for repair applications. The mechanical performance of the developed composites was evaluated in terms of its compressive and flexural properties, as these properties are critical to the performance of repair materials. Results from this study showed that fiber-reinforced composites produced with an eco-friendly binder exhibited excellent mechanical performance suited for various repair applications. Microstructural investigations were also carried out on the evaluated mixtures to determine the microstructural properties of the developed mixtures.

DOI:

10.14359/51725993


Document: 

19-067

Date: 

March 1, 2020

Author(s):

Seyedhamed Sadati and Kamal H. Khayat

Publication:

Materials Journal

Volume:

117

Issue:

2

Abstract:

The research presented in this paper addresses the effect of coarse recycled concrete aggregate (RCA) on drying shrinkage of concrete designated for transportation infrastructure. Six types of RCA were employed at 30 to 100% replacement rates of virgin coarse aggregate. Two binder systems, including a binary cement with 25% Class C fly ash and a ternary system with 35% fly ash and 15% slag were employed. Three different water-cementitious materials ratios (w/cm) of 0.37, 0.40, and 0.45 were considered. Test results indicate that the use of RCA increased drying shrinkage by up to 110% and 60% after 7 and 90 days of drying, respectively. Correlations with R2 of up to 0.85 were established to determine the shrinkage at 7, 28, 56, and 90 days as a function of aggregate properties, including specific gravity, water absorption, and Los Angeles abrasion resistance of the combined coarse aggregates. The water absorption of the combined coarse aggregate was shown to be a good index to showcase the effect of RCA on shrinkage. Contour graphs were developed to determine the effect of RCA content and its key physical properties on 90-day drying shrinkage of concrete intended for rigid pavement construction. A classification system available in the literature was also used to suggest the maximum allowable replacement rates for use of RCA in a hypothetical case study. Results suggest replacement rates of 100%, 70%, and 50% (% wt.) to limit the 90-day shrinkage to 500 μɛ when RCA of A-1, A-2, and A-3 Classes are available, respectively.

DOI:

10.14359/51720296


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


Document: 

19-136

Date: 

March 1, 2020

Author(s):

Bradley S. Hansen, Isaac L. Howard, Jay Shannon, Tim Cost, and Wayne M. Wilson

Publication:

Materials Journal

Volume:

117

Issue:

2

Abstract:

Portland-limestone cement (PLC) performance is controlled, to a significant extent, by limestone content and fineness. There are questions about how much fineness is needed or beneficial, with the most commonly used guidelines focused on how to achieve performance comparable to ordinary portland cement (OPC). This paper provides guidance on the production of PLC with potential concrete strength performance exceeding that of OPC and also considers (secondarily) concrete workability, setting, and durability performance. A database of related previous work was evaluated, and additional experiments were done with dedicated grinds of PLC at a single plant, from similar clinker, of varying fineness and controlled limestone contents. Findings from concrete and cement paste testing showed that the change in fineness (m2/kg) (ΔF) in relation to the change in limestone content (% limestone) (ΔL) relative to OPC can be a useful index for performance bench-marking. Specific guidance is provided where ΔF/ΔL values are in the general range of 10 to 30 and ΔF values are 110 to 175 m2/kg. Recommendations for some ΔF/ΔL values are also considered.

DOI:

10.14359/51720301


Document: 

19-044

Date: 

January 1, 2020

Author(s):

Joaquín Abellán, Jaime Fernández, Nancy Torres, and Andrés Núñez

Publication:

Materials Journal

Volume:

117

Issue:

1

Abstract:

This paper presents the experimental results of research carried out involving the compressive strength and slump flow of ultra-high-performance concrete (UHPC) made with cementitious blends of recycled glass flour, recycled glass powder, micro limestone powder, silica fume, and portland cement. The adopted second-order polynomic regression model provided an accurate correlation between the considered variables and the obtained responses. A numerical optimization was then performed to obtain an eco-friendly mixture with the proper flow, highest compressive strength, and minimum content of cement. The use of 603 kg/m3 of cement in the mixture can be considered as the most appropriate amount to be employed in UHPC mixtures, fulfilling the limit values of compressive strength and spread flow.

DOI:

10.14359/51720292


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