International Concrete Abstracts Portal

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International Concrete Abstracts Portal

Showing 1-10 of 28 Abstracts search results

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: 

19-067

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: 

19-136

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


Document: 

18-011

Date: 

November 1, 2019

Author(s):

A. Shakir, M. Haziman Wan Ibrahim, N. Othman, A. Ahmed, and S. Shahidan

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

Palm oil fuel ash (POFA) is a by-product procured from the palm oil mill through the incineration of empty fruit bunches, mesocarp fibers, and shells so as to produce electricity. POFA was considerably used as a cementitous supplement in various types of concrete, bricks, blocks, mortar, and grout due to its pozzolanic content. However, using raw POFA as cementitious replacement caused a distinct deterioration on the properties of the hardened mixture. Therefore, various treatment methodologies were adopted to enhance the properties of POFA to improve the mechanical properties of the hardened mixture. This study reviews the treatment approaches performed on POFA and their effects on the physical, chemical, and microstructural properties of POFA. It was documented that grinding POFA increased its fineness and decreased the voids and porosity of the mixture. However, the optimum use of grounded POFA was ranged 5 to 25% by weight of cement. On the other hand, thermal treatment of POFA exhibited a substantial improvement on the physical, chemical, and morphological properties of POFA; consequently, the hardened properties were dramatically developed. Thermal-treated POFA could be used as binder supplement up to 70% by weight of cement, whereby environmental pollution was dropped and sustainability was achieved. It was concluded that the higher fineness of POFA contributed to a significant pozzolanic reaction and thus promoted better performance in the hardened matrix. However, future detections should address the leaching behavior of POFA and the leaching performance of the hardened mixture incorporating POFA. Besides, the durability of specimens containing POFA as binder supplement should be well covered in the prospectus research.

DOI:

10.14359/51716975


Document: 

18-415

Date: 

September 1, 2019

Author(s):

C. Gunasekera, Z. Zhou, M. Sofi, D. W. Law, S. Setunge, and P. Mendis

Publication:

Materials Journal

Volume:

116

Issue:

5

Abstract:

The increase of carbon emissions due to the annual growth of portland cement (PC) production has promoted research into the development of sustainable green concrete using a range of readily available industrial waste materials. The present study is focused on developing two high-volume fly ash (HVFA) concretes with cement replacement levels of 65% (HVFA-65) and 80% (HVFA-80). The required lime for both HVFA concrete mixtures was initially determined and the optimized mixture designs identified, based on the 28-day compressive strength, by varying the low-calcium Class F fly ash-hydrated lime composition. The optimized concrete mixtures achieved a compressive strength of 53 and 40 MPa (7.69 and 5.80 ksi) for HVFA-65 and HVFA-80 concretes, respectively. The early-stage strength development is dependent on the matrix produced in the specific HVFA concrete, which is itself dependent on the number of unreacted fly ash spheres. The increase of fly ash and hydrated lime dosage in HVFA concrete increases the rate of hydration of the C3A and C4AF phases, but decreases the hydration of the C3S phase, which resulted in lower early-age strength development than occurs in PC concrete. It was noted that the initial setting time of HVFA concretes increase with an increase of fly ash content. However, addition of hydrated lime accelerates the hydration and decreases the final setting time for HVFA concretes.

DOI:

10.14359/51716815


Document: 

18-343

Date: 

July 1, 2019

Author(s):

Wei Cheng, John R. Elliott, and Kenneth C. Hover

Publication:

Materials Journal

Volume:

116

Issue:

4

Abstract:

Crushed charcoal (biochar) was introduced into mortar as lightweight, high-carbon fine aggregate, at eight levels of sand replacement varying from 0 to 100% and up to 275% of cement content by mass. Carbon encapsulated in hardened mortar offset the carbon footprint of cement production and reduced demand for natural sand. Water content was increased to accommodate 125% biochar absorption and maintain workability. Mixture proportions affected water-cement ratio (w/c), fresh density, and compressive and splitting tensile strength of hardened mortar, with significantly diminished strength at increased biochar content. A net carbon benefit accrued when biochar content exceeded approximately 10% of the total aggregate mass or one-third of the cement mass. At this level, compressive strength is less than typically associated with structural concrete, but net sequestration of 800 kg carbon per m3 (1350 lb/yd3) could be realized at strength levels associated with controlled low-strength materials (CLSM). Multiple environmentally effective applications are suggested.

DOI:

10.14359/51716716


Document: 

17-240

Date: 

May 1, 2018

Author(s):

Seyedhamed Sadati and Kamal H. Khayat

Publication:

Materials Journal

Volume:

115

Issue:

3

Abstract:

This paper evaluates the effect of recycled concrete aggregate (RCA) on concrete durability. Six RCA types procured from different sources were employed at 30 to 100% replacement rates by volume of virgin coarse aggregate. One fine RCA was also investigated and was used for up to 40% replacement by volume of virgin sand. In total, 33 mixtures were proportioned with these aggregates in concrete made with a binary or a ternary binder system and a watercementitious materials ratio (w/cm) of 0.37 to 0.45. The mixtures were investigated for frost durability, electrical resistivity, sorptivity, and abrasion resistance. Test results indicate that concrete made with up to 100% coarse RCA from an air-entrained source can exhibit proper frost durability. No significant reduction (limited to 3%) in frost durability factor was observed when the fine RCA volume was limited to 15% of total sand. Increase in mass loss due to deicing salt scaling was observed in concrete made with 50% of RCA with high (over 4%) deleterious materials content and high mass loss during soundness test. For a given w/cm and binder type, the use of 50% coarse RCA resulted in up to 32% reduction in electrical resistivity. The reduction in w/cm from 0.40 to 0.37 and the use of ternary binder containing 35% Class C fly ash and 15% slag proved to be effective in mitigating the potentially negative impact of RCA on sorptivity and abrasion resistance, compared to concrete made without any RCA with w/cm of 0.40 and binary cement with 25% fly ash.

DOI:

10.14359/51702190


Document: 

16-238

Date: 

January 1, 2018

Author(s):

Hasan Sahan Arel and Ertug Aydin

Publication:

Materials Journal

Volume:

115

Issue:

1

Abstract:

This work investigated the effects of Class F fly ash (FA), coconut husk ash (CHA), and rice husk ash (RHA) as cement replacements at various proportions on the workability, setting time, compressive strength, and pullout strength of concrete. Concretes containing partial replacement of cement by 20 and 40% FA and 10, 15, and 20% CHA and RHA were investigated. The results revealed that FA, CHA, and RHA can be used as replacements for cement in concrete production to produce sustainable and ecological products. The mixed composition of 20% FA and 20% RHA had 15.3% greater compressive strength than that of the reference composition after 180 days, while a slight reduction in this parameter was observed in FA-CHA combinations. FA and RHA mixtures showed the highest compressive and pullout strengths for all aging times tested.

DOI:

10.14359/51700991


Document: 

16-259

Date: 

March 1, 2017

Author(s):

Jay Shannon, Isaac L. Howard, V. Tim Cost, and Will Crawley

Publication:

Materials Journal

Volume:

114

Issue:

2

Abstract:

Portland-limestone cement (PLC) has recently been found useful in improving concrete’s synergy with some supplementary cementitious materials (SCMs), relative to ordinary portland cement (OPC), and in reducing early-age performance impacts of higher levels of cement replacement with SCMs. Use of PLC extends sustainability benefits by reducing concrete’s carbon footprint via reduced clinker content. This study explores how the performance of concrete using higher cement replacement with SCMs may be improved through use of PLCs in place of traditional OPCs in support of improved sustainability. PLCs were found to be able to enhance strength and setting in mixtures with higher levels of SCM replacement of cement, especially in certain combinations, while maintaining or improving later-age strengths. Results were notably productive in balancing mixture early performance, late-age strengths, and economics, with performance generally improved using PLCs relative to OPCs.

DOI:

10.14359/51689596


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