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Showing 1-5 of 55 Abstracts search results

Document: 

19-385

Date: 

September 1, 2020

Publication:

Materials Journal

Volume:

117

Issue:

5


Document: 

19-206

Date: 

May 1, 2020

Author(s):

Anwar Al-Yaqout, Moetaz El-Hawary, Khallad Nouh, and Pattan Bazieth Khan

Publication:

Materials Journal

Volume:

117

Issue:

3

Abstract:

The main objective of this paper is the investigation of the corrosion resistance of reinforced concrete containing various proportions of recycled aggregates (RA) combined with 25% ground-granulated blast-furnace slag (GGBS) as a partial cement replacement. An accelerated corrosion system was designed to test the steel corrosion in reinforced concrete by subjecting the samples to 150 and 300 wetting-and-drying cycles. The results, in general, showed that the use of RA in concrete mixtures was found to reduce the compressive strength, increase chloride penetration, decrease the corrosion potential of reinforcing bars, reduce the electrical resistance of concrete, and hence increase the corrosion risk. However, better results were achieved by the addition of 25% GGBS, which increased the core compressive strength and electrical resistance. Moreover, better results were achieved for normal and slag mixtures that have 0.788 in. (20 mm) concrete cover than those having 0.394 in. (10 mm) cover.

DOI:

10.14359/51722406


Document: 

19-253

Date: 

May 1, 2020

Author(s):

K. Tamanna, M. Tiznobaik, N. Banthia, and M. Shahria Alam

Publication:

Materials Journal

Volume:

117

Issue:

3

Abstract:

Using recycled scrap tire and construction and demolition waste as aggregates in concrete will not only facilitate an environmentally sustainable solution to solid waste disposal but also will significantly contribute to alleviating the ever-growing demand for natural aggregates in concrete production. However, only limited studies focused on the use of rubberized recycled aggregate concrete (RRAC), which lacks in-depth scrutinization of its material behavior with respect to conventional concrete. The first stage of this study is focused on investigating the effect of pre-treatment of crumb rubber (CR) with three levels of NaOH concentration on rubberized mortar specimens. The second stage consists of an experimental investigation on the mechanical behavior of concrete comprising CR and recycled concrete aggregate (RCA) each at three replacement levels of natural fine and coarse aggregates, respectively, at a water-cement ratio (w/c) of 0.34. The results indicate RRAC yields satisfactory compressive and flexural behavior for use in structural concrete.

DOI:

10.14359/51722409


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: 

19-088

Date: 

March 1, 2020

Author(s):

B. Cantero Chaparro, I. F. Sáez del Bosque, A. Matías Sánchez, M. I. Sánchez de Rojas, and C. Medina

Publication:

Materials Journal

Volume:

117

Issue:

2

Abstract:

A full understanding of the characteristics of the granular skeleton comprising different percentages of conventional and recycled aggregates is requisite to the reusability of construction and demolition waste. This study analyzed the effect of partially replacing natural aggregate with recycled concrete (RCA) and mixed (RMA) aggregates on the performance of granular mixtures. Each type of aggregate was characterized physically, chemically, mineralogically, and mechanically, and the physical and mechanical properties of the mixtures were assessed. Correlations were established to predict the optimal mixture proportions. The recycled aggregates analyzed met most requirements laid down in the national legislation and complied with international recommendations. The mixtures exhibited a close linear correlation between the properties analyzed and the recycled aggregate replacement ratios. For concrete, the upper limit was 75% for RCA and RMA, and for the base and intermediate layers in medium/low traffic roads, 75% for RCA and 35% for RMA.

DOI:

10.14359/51720299


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