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International Concrete Abstracts Portal

Showing 1-10 of 582 Abstracts search results

Document: 

17-433

Date: 

November 1, 2019

Publication:

Materials Journal

Volume:

116

Issue:

6


Document: 

18-314

Date: 

September 1, 2019

Author(s):

Harikrishnan Nair and H. Celik Ozyildirim

Publication:

Materials Journal

Volume:

116

Issue:

5

Abstract:

Cracks in bridge decks facilitate the penetration of chlorides that induce corrosion of reinforcing steel. Formation of cracks is related to the shrinkage and properties of the concrete and the restraints to movement. Lightweight concrete with a low modulus of elasticity, high creep, and water in the aggregate pores for internal curing has a reduced cracking potential. To control cracking, shrinkage of concrete can be reduced by using a shrinkage-reducing admixture (SRA). A recent study at the Virginia Department of Transportation (VDOT) investigated the performance of both lightweight concretes and concretes with SRA containing normal-weight aggregates in the field and found that these concretes had no cracks or fewer cracks than were typical of decks constructed with normal-weight aggregates over the past 20 years. VDOT developed a new specification that included lightweight concretes or concretes with normal-weight aggregates and SRA and this specification is being used successfully to reduce cracking in bridge decks. This paper summarizes the work conducted to develop the new specification and includes information on field applications.

DOI:

10.14359/51716830


Document: 

18-036

Date: 

September 1, 2019

Author(s):

Yail J. Kim and Junhao Gao

Publication:

Structural Journal

Volume:

116

Issue:

5

Abstract:

This paper presents a new concept of high-performance structures composed of internally cured concrete and glass fiber-reinforced polymer (GFRP) reinforcement. The former addresses autogenous shrinkage that leads to premature cracking of concrete, and the latter provides a noncorrosive service environment. Presaturated superabsorbent polymer (SAP) is mixed with concrete at 0 to 0.4% of the cement mass to facilitate a hydration process. The swelling kinetics of SAP due to water absorption is quantified, and its releasing rate with time is determined. A total of 15 one-way slabs are tested in flexure to examine the effects of SAP inclusions. The behavior of the slabs is assessed by deterministic and stochastic models with an emphasis on tension stiffening and performance reliability. The amount of the internal curing agent affects the strength of the concrete and the response of the slabs. Various cracks are observed when the slabs are loaded, including flexural, horizontal splitting, and diagonal tension cracks. As the amount of SAP increases, the cracks become localized and expedite the failure of the slabs. The tension stiffening of control slabs (0%SAP) is more pronounced than that of the slabs with SAP. The cumulative degradation probability and the risk level of the slabs made of the internally cured concrete are controlled by the amount of SAP.

DOI:

10.14359/51715574


Document: 

18-352

Date: 

July 1, 2019

Author(s):

Mahipal Kasaniya, Michael D. A. Thomas, and Edward G. Moffatt

Publication:

Materials Journal

Volume:

116

Issue:

4

Abstract:

With the potential decline in supplies of today’s most widely used supplementary cementitious materials (SCMs) such as fly ash and slag, there is growing interest in the use of natural pozzolans (for example, pumice, volcanic ash), processed pozzolans (for example, calcined clays and shales), and manufactured pozzolans (for example, ground glass). Establishing the pozzolanic reactivity of these materials is an essential part of the evaluation process. Currently, pozzolans are assessed using ASTM C618 and C311, with the strength activity test being the only real performance indicator. Unfortunately, it is not possible to accurately determine the contribution of the pozzolanic reactivity to the strength in this test. This paper presents the development of a new pozzolanic reactivity test method based on the previous strength-activity-with-lime test but modified to increase the rate of the pozzolanic reaction. In this test, the solution-to-binder ratio is kept constant with workability adjusted using chemical admixtures. A range of mixing solutions containing combinations of KOH, NaOH, and K2SO4 and various curing regimes were investigated. The outcome of the test is compared with results from the current ASTM C311 and CSA A3004-E1 test methods for a wide range of pozzolanic (and inert) materials.

DOI:

10.14359/51716718


Document: 

18-348

Date: 

July 1, 2019

Author(s):

Marija Krstic and Julio F. Davalos

Publication:

Materials Journal

Volume:

116

Issue:

4

Abstract:

The inconsistent supply of fly ash and relatively high cost of slag as supplementary cementitious materials (SCMs) in the Northeastern United States is of concern to the concrete industry. Fly ash is a by-product from coal-burning plants that are shutting down or converting to natural gas, and slag is a residue from steel production mainly outside of the United States. With the goal of contributing significantly to the implementation of sustainable high performance concrete, this study focuses on the evaluation of mixture designs using recycled post-consumer glass as SCM for concrete, for three mixtures with 20, 30, and 40% glass pozzolan as cement replacements, as well as two other comparable mixtures with 30% fly ash and 40% slag. Following laboratory characterizations for fresh and hardened properties, the mixtures with 20 and 40% glass pozzolan were selected for implementation in a sidewalk project in Queens, NY. The field work involved evaluations of mixture production, placement, finishing, curing, compressive strength, and development of maturity curves from data loggers in concrete. This study offers great potential for benefitting the concrete and glass recycling industries.

DOI:

10.14359/51716716


Document: 

18-070

Date: 

July 1, 2019

Author(s):

Krešimir Nincevic, Lisa-Marie Czernuschka, Marco Marcon, and Roman Wan-Wendner

Publication:

Structural Journal

Volume:

116

Issue:

4

Abstract:

A large experimental campaign was completed with the objective to determine how concrete composition and age affect the tensile load capacity of mechanical anchors with concrete cone breakout, tested in three different normal-strength concretes. Structural tests for cast-in headed stud anchors were performed at 28 and 70 days and compared to results obtained on post-installed undercut anchors. The concretes were fully characterized in terms of Young’s modulus, compressive and tensile strength, and fracture energy. The evolution of the concrete compressive strength is consistent with the aging function proposed in codes. Because the history of environmental conditions influences the development of material properties with age, three different curing conditions are considered for the material characterization, including indoor moist-curing and outdoor storage with the slabs. The structural data clearly show a pronounced aging effect, even after normalization by compressive strength, regardless of the curing protocol considered.

DOI:

10.14359/51715575


Document: 

17-487

Date: 

July 1, 2019

Author(s):

Harun Tanyildizi

Publication:

Materials Journal

Volume:

116

Issue:

4

Abstract:

This study investigated polymer-phosphazene mortars subjected to external sulfate attack for 1 year to examine their resistance to the sulfate effect. Then, the mechanical properties and microstructure of polymer-phosphazene mortars were studied. The number of experiments was reduced by selecting the L25 orthogonal array. Samples were produced in sizes of 50 x 50 x 50 mm (1.97 x 1.97 x 1.97 in.) and 25 x 25 x 285 mm (0.98 x 0.98 x 11.22 in.). The samples were dried at 105 ± 5°C (221 ± 9°F) for 24 hours after curing for 28 days. Later, the monomer containing phosphazene was impregnated to samples at atmospheric conditions for 1 day. The polymerizations of samples were carried out at 60°C (140°F) for 4 hours. These samples were subjected to sulfate attack for 30, 60, 90, 180, and 365 days. The compressive strength, weight, and length changes of polymerphosphazene mortars subjected to external sulfate attack were determined. After the external sulfate attack, scanning electron microscope (SEM), energy-dispersive X-ray (EDX), and X-ray diffraction (XRD) analyzes of the samples were carried out. The analysis of variance (ANOVA) results showed that the most effective parameter was cement dosage. The results showed that sulfate was prevented from entering into the concrete as cracks and voids in the samples were filled with phosphazene polymers.

DOI:

10.14359/51716818


Document: 

17-254

Date: 

May 1, 2019

Author(s):

Duo Zhang and Yixin Shao

Publication:

Materials Journal

Volume:

116

Issue:

3

Abstract:

Carbonation curing has demonstrated potential of improving concrete performance while facilitating carbon dioxide utilization. However, reinforcement corrosion behavior in carbonation-cured concrete has not been documented. This paper presents a study on chloride-induced corrosion in reinforced concrete subjected to carbonation curing. A special carbonation curing process was developed for precast non-prestressed applications. Performance of carbonation curing was evaluated by concrete compressive strength, pH value, and carbon dioxide uptake, while corrosion resistance of the carbonation-cured concrete was assessed by reinforcing bar mass loss and concrete chloride content. To understand the mechanism, concrete and cement paste were further characterized using mercury intrusion porosimetry, absorption, and electrical resistivity tests. Micromorphology was assessed by scanning electron microscopy. It was found that apart from rapid early-age strength gain, carbonation curing could significantly reduce chloride permeation in concrete concerning both total and free chloride contents. It was attributed to the reduced pore size and pore volume by calcium carbonate precipitation. With subsequent 28-day hydration, the carbonation-cured concrete displayed a pH over 12.0 at the surface of steel reinforcing bars and a micromorphology similar to the non-carbonated reference. The direct corrosion tests showed that the corrosion-induced mass loss of steel reinforcing bar was lessened by 50% in concrete subjected to carbonation curing.

DOI:

10.14359/51714461


Document: 

18-224

Date: 

March 1, 2019

Author(s):

Kamran Amini, Seyedhamed Sadati, Halil Ceylan, and Peter C. Taylor

Publication:

Materials Journal

Volume:

116

Issue:

2

Abstract:

With adoption of winter maintenance strategies that typically include incorporation of aggressive deicer chemicals, pavement surfaces in cold regions are exposed to the risk of scaling damage. Reduced ride quality due to surface deterioration can eventually lead into a variety of maintenance and repair programs. Such pavement preservation programs impose significant charges to the owner agencies, while raising concerns regarding the safety issues associated with work zone areas. The present study addresses the correlation between surface hardness and concrete hardened properties. Moreover, factors that influence the concrete performance with respect to surface-abrasion resistance (hardness) were investigated. Of special interest was the relationship between surface hardness and concrete salt-scaling performance. An extensive investigation was carried out to assess the effects of various mixture proportions, curing regimes, and finishing times on surface hardness of the concrete specimens. In addition, compressive strength, depth-sensing indentation (DSI), and salt scaling tests were used to evaluate the correlation between concrete surface hardness and performance. A scaling quality classification table using abrasion mass loss values was developed. The results reflect further understanding of the relationship between abrasion resistance and salt scaling resistance that can cause defects when more than two cycles of abrasion testing are applied.

DOI:

10.14359/51714457


Document: 

18-183

Date: 

March 1, 2019

Author(s):

Pshtiwan Shakor, Shami Nejadi, Gavin Paul, Jay Sanjayan, and Ali Nazari

Publication:

Materials Journal

Volume:

116

Issue:

2

Abstract:

Three-dimensional (3-D) printers have the potential to print samples that can be used as a scaffold for a variety of applications in different industries. In this paper, cement-based materials including ordinary portland cement, calcium aluminate cement (passing 150 μm [0.0059 in.] size sieve), and fine sand were investigated as the cement-based materials in inkjet 3-D printing. Prism specimens were printed for the three-point bending test; and cubic specimens were printed for the uniaxial compressive strength test. Prism samples were printed along different directional axes (X, Y, and Z). The tests were conducted at different saturation levels (water-cement ratio [w/c]) as represented by S100C200, S125C250, S150C300, and S170C340. The prism specimens were cured in water for 7 and 28 days while cubic specimens were cured in Ca(OH)2 and water for 7 and 28 days at the same ambient temperatures. In general, the results changed according to the directional axes of the prisms. However, following water curing, the cubic samples were heated up to 40°C (104°F) in an oven and a higher compressive strength was evident compared to the samples which were only cured in the room-temperature water. The wettability test for both powders has been conducted in the presented study.

DOI:

10.14359/51714452


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