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International Concrete Abstracts Portal

Showing 1-10 of 585 Abstracts search results

Document: 

19-022

Date: 

January 1, 2020

Publication:

Materials Journal

Volume:

117

Issue:

1


Document: 

18-481

Date: 

November 1, 2019

Author(s):

Augustine Uchechukwu Elinwa and Nasir Kabir

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

This research work was on the evaluation of the flexural strength and compressive strength relationship of spent foundry sand (SFS) concrete. The relationship was established using a concrete mixture of 1:1.71:2.56, a cement content of 404 kg/m2, and a water-cement ratio (w/c) of 0.52. This was used to cast beams of dimensions 150 x 150 x 500 mm (6 x 6 x 20 in.) cured for 90 days in a water curing tank under laboratory conditions. The SFS was used to replace fine aggregate (FA) 0 to 40% by wt. The evaluations on the statistical characteristics of the flexural strength data results showed that the addition of SFS to concrete improved the hydration process. This was reflected in the strength development of the concrete and the strong correlation and level of significance observed with the variables (mixture and age). The values of the modulus of rupture (MOR) obtained are in the range of 4.6 to 6.6 MPa; this was at the optimum replacement of 10%. At this level, the value of the flexural strength was approximately 29% of the compressive strength. The two models chosen that represented the flexural strength and compressive strength relations are the square root and 2/3 models. The relative predictive error (RPE) for each is 0.1 and 0.2, respectively.

DOI:

10.14359/51718055


Document: 

18-391

Date: 

November 1, 2019

Author(s):

Songhee Lee, Yeonhee Kim, Minhyeok Ko, and Chadon Lee

Publication:

Structural Journal

Volume:

116

Issue:

6

Abstract:

Re-tensioning tests were performed and analyzed to measure the thermal prestress loss (ΔfT) caused by elevated temperatures during the curing of precast and prestressed concrete members. A total of eight prismatic concrete beams were pretensioned with strands 12.7 mm (0.5 in.) in diameter. Experimental parameters were the concrete strength (f ′cd), initial prestress (fpi), and curing condition (steam curing versus air-dry curing at ambient temperature). Analytical expressions were derived for changes in prestress at different curing stages. Using those expressions and the retensioning test results, the time and temperature at bonding between the strand and the surrounding concrete were identified. The results indicate that ΔfT was only marginally influenced by f ′cd and fpi. However, ΔfT was observed to increase almost linearly with the additional increase in temperature until bonding.

DOI:

10.14359/51718004


Document: 

17-433

Date: 

November 1, 2019

Author(s):

Er-yu Zhu and Ze-wen Zhu

Publication:

Materials Journal

Volume:

116

Issue:

6

Abstract:

A total of 16 pullout specimens were tested to investigate the effect of curing conditions on bond behavior of near-surface-mounted (NSM) carbon fiber-reinforced polymer (CFRP) strengthening concrete under curing temperatures from 35 to 65°C (95 to 149°F) and curing times from 6 to 12 hours. It was compared to that of specimens in ambient conditions (16°C [60.8°F]). On these bases, a nonlinear local bond-slip model was proposed. Two key parameters—A and B—are employed in the proposed bond-slip model, the specific expressions of which were mainly related to ultimate pullout load and peak shear stress of the specimen. The results show that the bond behavior of CFRP strip represents a negative quadratic curve with curing temperature and positive inverse tangent curves with curing time, respectively. The nonlinear local bond-slip model, considering the curing temperature-time, is deduced and validated.

DOI:

10.14359/51719148


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


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