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International Concrete Abstracts Portal

Showing 1-10 of 256 Abstracts search results

Document: 

19-196

Date: 

March 1, 2020

Author(s):

Kacie C. D’ Alessandro, Carin L. Roberts-Wollmann, and Thomas E. Cousins

Publication:

Materials Journal

Volume:

117

Issue:

2

Abstract:

Ultra-high-performance concrete (UHPC) is known for its high strength and advanced durability. Due to the unique formulation of this material, including a fine cementitious matrix and distributed steel fibers, UHPC displays different material behavior than conventional concrete. This paper examines the biaxial tension-compression behavior of UHPC using a novel biaxial test method and compares results to biaxial failure criterion of conventional concrete. A total of 62 specimens were tested to evaluate the effects of curing regimes and fiber orientations. While the compressive strength of UHPC increased significantly when steam treated, tensile strength did not increase to the same degree. Controlled fiber orientation provided more compressive stress resistance than random fiber orientation with the presence of increasing tensile stress. Comparing UHPC results to biaxial failure criterion recognized for conventional concrete, the Mohr-Coulomb biaxial failure criterion was shown to be a conservative model for UHPC for all fiber orientations and curing regimes.

DOI:

10.14359/51722404


Document: 

18-448

Date: 

March 1, 2020

Author(s):

Yu Song and David A. Lange

Publication:

Materials Journal

Volume:

117

Issue:

2

Abstract:

Foam concrete is a highly cellularized cementitious material that undergoes extensive plastic deformation when loaded to failure. Under compression, the microstructure of low-density foam concrete gets progressively crushed at a steady stress stage, accompanied by substantial energy dissipation. Understanding foam concrete crushing behavior is of special importance for its engineering applications. However, the current studies are insufficient to define key attributes that are important for material characterization and design. This study focuses on low-density foam concrete ranging from 0.4 to 0.8 g/cm3 (25 to 50 lb/ft3), with the crushing behavior investigated using a penetration test and dynamic Young’s modulus determined using a resonant frequency test. Four distinct crushing phases—linear elastic, transitional, plateau, and final densification—are observed for the samples. Furthermore, the yield strength and plateau strength are identified to characterize the foam crushing behavior. Using the experimental inputs, the modulus-strength constitutive relationship is established for predicting the crushing behavior with fundamental material properties. The findings significantly facilitate subsequent foam concrete studies, as well as the engineering design of this material.

DOI:

10.14359/51722394


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: 

19-035

Date: 

January 1, 2020

Author(s):

Aravind Tankasala and Anton K. Schindler

Publication:

Materials Journal

Volume:

117

Issue:

1

Abstract:

In this project, the effect of using lightweight aggregate (expanded slate) on the early-age cracking tendency of mass concrete mixtures was evaluated. Concretes representative of mass concrete mixtures—namely, normal-weight concrete, internally cured concrete, sand-lightweight concrete, and all-lightweight concrete—at two different water-cementitious materials ratios (0.38 and 0.45) were tested in cracking frames from the time of setting until the onset of cracking. The development of early-age concrete stresses caused by autogenous and thermal shrinkage effects were measured from setting to cracking. The behavior of concretes containing lightweight aggregates was compared with normal-weight concrete placed under temperature conditions simulating fall placement in mass concrete applications. Increasing the amount of pre-wetted lightweight aggregates in concrete results in systematic decrease in density, reduced modulus of elasticity, and reduced coefficient of thermal expansion. All these factors effectively improve the concrete’s early-age cracking resistance in mass concrete applications.

DOI:

10.14359/51719082


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: 

18-040

Date: 

November 1, 2019

Author(s):

Sherif Yehia, Sharef Farrag, and Omar Abdelghaney

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

The durability of lightweight concrete (LWC), especially in the long term, is an essential factor for its successful implementation in structural applications. The use of supplementary cementitious materials (SCMs) and/or fibers changes the interaction between concrete constituents at a microlevel, which might improve durability. In this paper, the mechanical properties and durability aspects of fiber-reinforced, self-consolidating, high-strength, lightweight concrete were evaluated. Concrete specimens were exposed to wetting-and-drying cycles for 1 year in salt water to simulate chloride attack present in the United Arab Emirates and then were compared to control specimens. Results of the compressive strength, flexural strength, and modulus of elasticity are presented and discussed. In addition, scanning electron microscope (SEM) scans and rapid chloride permeability test (RCPT) were conducted. Results showed that the inclusion of fibers alters the microstructural features of concrete; hence, a different chloride resistance mechanism is introduced. Nevertheless, inclusion of fibers did not lead to an increase in chloride permeability. At 1 year, there was an ~3% and 10% reduction in compressive strength in the exposed plain and the fiber-reinforced mixtures, respectively, compared to the non-exposed mixtures. However, fibers significantly enhanced the flexural strength of lightweight concrete (up to an ~100% increase) compared to plain mixtures. In addition, cracks were ~80% smaller in the fiber-reinforced mixtures compared to the plain mixture.

DOI:

10.14359/51716976


Document: 

18-440

Date: 

November 1, 2019

Author(s):

Arturo D’Alessandro, David J. Corr, and Surendra P. Shah

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

Ferrocement is a construction material that (in comparison to traditional reinforced concrete) provides superior crack control, impact resistance, and toughness. However, while extensive literature exists on the deterioration mechanisms and maintenance of reinforced concrete structures, little attention has been given to the durability of ferrocement. In this study, the adoption of ethyl silicate, a newly developed nanomaterial, is investigated to improve durability of ferrocement. Such nanomaterials are expected to penetrate the cementitious matrix without changing the appearance of the surface. Once penetrated, pozzolanic behavior is displayed forming calcium silicate hydrate and consequently increasing durability and mechanical performance. Particular attention is given to the carbonation-induced corrosion of reinforcement, which should be considered a major concern in ferrocement due to the initially small diameter of the mesh wires and the thin mortar cover. Despite its importance, there is a limited amount of literature on carbonation-induced corrosion of ferrocement structural elements.

DOI:

10.14359/51716821


Document: 

18-356

Date: 

September 1, 2019

Author(s):

Jussara Tanesi, Haejin Kim, and Ahmad Ardani

Publication:

Materials Journal

Volume:

116

Issue:

5

Abstract:

Deicing chemical solutions can profoundly affect concrete’s physical and chemical properties. It is a known fact that salt solutions are highly conductive in comparison with pure water and are expected to alter concrete’s electrical resistivity as well as other transport properties. In this study, the influence of NaCl, CaCl2, and MgCl2 on transport properties of cementitious materials was investigated. The first part of the project evaluated the continuous exposure for 1 year, while the second part evaluated the wetting-drying cyclic exposure for 6 months (27 cycles). This paper presents the results of the cyclic exposure. Results obtained with standard testing methodologies can be misleading and should be interpreted with caution because transport properties were influenced by different factors, especially the exposure history. In addition, each salt affected each individual transport property differently. Cyclic exposed samples presented similar results as those subjected to 1 year of continuous exposure.

DOI:

10.14359/51716837


Document: 

18-338

Date: 

September 1, 2019

Author(s):

Karthik H. Obla

Publication:

Materials Journal

Volume:

116

Issue:

5

Abstract:

Past research showed a correlation between the measured apparent chloride diffusion coefficient determined in accordance with ASTM C1556 and the ASTM C1202 rapid indication of chloride ion penetrability test (RCPT) results. Based on that research, a combination of RCPT and strength criteria was proposed to categorize mixtures based on their resistance to chloride ion penetration. This article proposes specification criteria based on a formation factor to categorize mixtures. The efficacy of using both approaches to categorize 44 concrete mixtures prepared from different portland cements, types and dosages of supplementary cementitious materials, and w/cm is examined. It is found that either approach can be used to categorize mixtures based on their resistance to chloride ion penetration. Specimens from 10 mixtures, moist-cured for over 8 years, were tested for surface and bulk resistivity. The same specimens were immersed in chloride solutions in accordance with ASTM C1556, and chloride-ion contents at specific depths from the exposed surface were measured and compared with the later-age bulk resistivity, early-age RCPT, and estimated formation factor.

DOI:

10.14359/51716835


Document: 

18-310

Date: 

September 1, 2019

Author(s):

M. Moini, K. Sobolev, I. Flores-Vivian, S. Muzenski, L. T. Pham, S. Cramer, and M. Beyene

Publication:

Materials Journal

Volume:

116

Issue:

5

Abstract:

Durability and long-term performance of concrete exposed to deleterious ions and environmental conditions are major concerns. The rapid chloride permeability (RCP) test is commonly used in specifications in the United States to evaluate the permeability of concrete. To evaluate the critical factors that control the service life of structures, the investigation of various concrete mixtures is required. In this paper, the performance of 54 concrete mixtures containing three types of water-reducing admixtures, two types of aggregates, and two levels of cement contents are evaluated in the RCP and freezing-and-thawing tests and the air void structure of selected mixtures are analyzed. It was found that the use of supplementary cementitious materials (SCMs) significantly enhances the performance of concrete mixtures in the RCP test. In addition, mixtures containing up to 30% of Class C fly ash and 50% slag content achieved exceptional durability performance in both RCP and freezing-and-thawing (F-T) tests. The “very-low” RCP values were found for mixtures containing Class F fly ash and polycarboxylate ether (PCE) admixture.

DOI:

10.14359/51716828


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