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International Concrete Abstracts Portal

Showing 1-5 of 46 Abstracts search results

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: 

18-010

Date: 

November 1, 2019

Author(s):

Konstantinos Sotiriadis, Eleni Rakanta, Maria Eleni Mitzithra, George Batis, and Sotirios Tsivilis

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

The development of environmentally friendly cementitious materials, efficient in preventing chloride ingress and decreasing reinforcement corrosion risk, is significantly important for structural applications exposed to corrosive conditions. This paper investigates the effect of natural pozzolana, fly ash, blast-furnace slag, and metakaolin on the behavior of portland-limestone cement concretes and mortars during storage in chloride-sulfate and chloride solutions at 5°C (41°F). Acid- and water-soluble chloride contents, and apparent chloride diffusion coefficients, were determined in concretes. Reinforcement corrosion half-cell potential and current density, mass loss of steel reinforcing bars, and carbonation depth were monitored in mortars. The employment of mineral admixtures decreased chloride ingress and reinforcement corrosion during specimens’ exposure to chloride solution; however, the presence of sulfates in the corrosive environment prevented their improving effect. Mineral admixtures increased chloride binding and the resistance of concrete against chloride diffusion, while they also showed similar efficiency in preventing reinforcement corrosion. Sulfates facilitated chloride ingress, hindered chloride binding, and promoted reinforcement corrosion.

DOI:

10.14359/51716820


Document: 

18-507

Date: 

November 1, 2019

Author(s):

Saranya P, Praveen Nagarajan, and A. P. Shashikala

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

Development of geopolymer concrete (GPC) with industrial by-products is a solution to the disposal of the industrial wastes, thus making the concreting process sustainable. This paper focuses on the development of GPC using ground-granulated blast-furnace slag (GGBS) and dolomite (by-product from rock crushing plant) as source materials. Strength properties of slag-based GPC are studied with different proportions of dolomite. It is observed that the addition of dolomite into slag-based GPC reduces the setting time, enhances workability, and rapidly improves the early-age strength. Addition of dolomite into slag GPC also improves the durability properties, such as high resistance towards water absorption, sorptivity, marine attack, and chemical attack.

DOI:

10.14359/51716981


Document: 

18-192

Date: 

March 1, 2019

Author(s):

Meysam Najimi and Nader Ghafoori

Publication:

Materials Journal

Volume:

116

Issue:

2

Abstract:

The current study aims to assess the transport and durability properties of alkali-activated concretes made with hybrid aluminosilicate precursors having different proportions of natural pozzolan as a low-calcium precursor and ground-granulated blast furnace slag as a high-calcium precursor, which are activated with different concentrations and combinations of sodium hydroxide and sodium silicate. The studied parameters included precursor combination (natural pozzolan/slag combinations of 30/70, 50/50, and 70/30), sodium hydroxide concentration (1, 1.75, and 2.5 M), and activator combination (sodium hydroxide/sodium silicate combinations of 70/30, 75/25, and 80/20). The resulting concrete mixtures were tested for slump flow, setting time, compressive strength, absorption, rapid chloride penetration, rapid chloride migration, resistance to sulfuric acid attack, chloride-induced corrosion, and frost resistance. Mercury intrusion porosimetry and X-ray diffraction were used to justify the observed behaviors. The performance of alkali-activated natural pozzolan/slag concretes was also compared with that of a reference concrete made with solely portland cement binder. In view of overall performance, an equal proportion of natural pozzolan and slag (50/50) and a 30/70 combination of sodium silicate and sodium hydroxide proved to be the optimum precursor and activator combinations. The optimum sodium hydroxide concentration was dependent on the precursor and activator combinations as well as the expected fresh, strength, transport and durability performance. In terms of the measured transport properties (that is, absorption, chloride penetration depth, and passing charges) and resistance to acid attack and chloride-induced corrosion, all the studied alkali-activated concretes performed considerably superior to the reference portland cement concrete. In the case of frost resistance, only alkali-activated concretes with 50 and 70% slag performed superior to the reference portland cement concrete.

DOI:

10.14359/51714455


Document: 

18-186

Date: 

March 1, 2019

Author(s):

Sary A. Malak and Neven Krstulovic-Opara

Publication:

Materials Journal

Volume:

116

Issue:

2

Abstract:

This paper presents a micromechanical energy approach model that builds upon models previously developed for aligned fibers predicting slurry infiltrated mat concrete’s (SIMCON) behavior in tension at first crack and ultimate strength for the general orientation of fiber mats in terms of the critical fiber/matrix interfacial parameters. SIMCON is a new high-performance fiber-reinforced concrete (HPFRC) made by infiltrating continuous steel fiber-mats with cement-based slurry. What distinguishes this material from other fiber-reinforced composites is that the fibers have flexible longer individual lengths that can be placed at specific orientations depending on the appropriate applications, resulting in higher interfacial debonding energies. These characteristics are best suited for repair and new construction for structural retrofits that require a predetermined orientation of the fibers to optimize the design and enhance the material resistance to high-blast pressures applied at different directions to the structural elements.

DOI:

10.14359/51714453


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