International Concrete Abstracts Portal

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International Concrete Abstracts Portal

Showing 1-10 of 1680 Abstracts search results

Document: 

18-490

Date: 

September 1, 2019

Publication:

Materials Journal

Volume:

116

Issue:

5


Document: 

18-349

Date: 

September 1, 2019

Author(s):

Alok A. Deshpande and Andrew S. Whittaker

Publication:

Structural Journal

Volume:

116

Issue:

5

Abstract:

The effect of elevated temperature on the mechanical behavior of concrete and the seismic behavior of reinforced concrete walls was investigated through materials and component testing. Tests were performed on concrete cylinders at temperatures between 70 and 600°F (21 and 316°C). The planar walls had web reinforcement ratios of 0.93% and 2.0%; the concrete compressive strength was approximately 6 ksi (41 MPa) for all walls. The maximum surface temperature for the tests of the walls was 450°F (232°C). Fully reversed, in-plane, inelastic cyclic loading was imposed on the walls in heated and ambient conditions to establish the effects of elevated temperature on peak strength and elastic stiffness. For temperature between 68 and 450°F (20 and 232°C), the materials tests showed a reduction in concrete uniaxial compressive strength and compression modulus of elasticity of no more than 10% and 30%, respectively. The wall tests showed no meaningful effect of temperature on either peak strength or secant stiffness to peak strength in both heated (up to 450°F [232°C]) and residual (tested at room temperature after cooling from 450°F [232°C]) conditions.

DOI:

10.14359/51715636


Document: 

18-310

Date: 

September 1, 2019

Publication:

Materials Journal

Volume:

116

Issue:

5


Document: 

18-283

Date: 

September 1, 2019

Publication:

Materials Journal

Volume:

116

Issue:

5


Document: 

18-272

Date: 

September 1, 2019

Publication:

Materials Journal

Volume:

116

Issue:

5


Document: 

18-392

Date: 

July 1, 2019

Author(s):

Edwin R. Dunstan Jr.

Publication:

Materials Journal

Volume:

116

Issue:

4

Abstract:

The current ASTM C311 test method to determine strength activity index (SAI) of fly ash and pozzolans was introduced in the 1980s. ASTM C618 specifies that a fly ash or pozzolan should have a minimum SAI of 75%. The SAI limit is inadequate because marginal materials, which are neither pozzolanic nor partially cementitious materials, are known to meet the 75% limit. A strength efficiency test procedure is proposed to replace the current SAI test. Strength efficiency of a fly ash or pozzolan is subdivided into efficiency from chemical reaction (pozzolanic and cementitious) and efficiency from changes in water-cement ratio (non-chemical impacts). A new specification limit is proposed based on chemical efficiency. In turn, chemical reaction is subdivided into pozzolanic and self-cementing reactions, which coincides with the recent 18% CaO% specification that separates Class C and Class F fly ashes.

DOI:

10.14359/51716721


Document: 

18-354

Date: 

July 1, 2019

Author(s):

Ruben Snellings, Xuerun Li, François Avet, and Karen Scrivener

Publication:

Materials Journal

Volume:

116

Issue:

4

Abstract:

Although supplementary cementitious materials (SCMs) are now commonly accepted and widely used, consensus has not been reached for methods to test their chemical reactivity. A multitude of test methods exist but often fall short on one or more of the key features of a proper test—that is, width of scope, practicability, reproducibility, and relevance of the result. A rapid, robust, and relevant chemical reactivity test applicable to a wide range of SCMs would therefore not only serve as global benchmark but it would also remove present ambiguities in regards to classification. In response, a new, so-called “R3” test was conceived at Ecole Polytechnique Federale de Lausanne and is now being further developed and tested in RILEM TC 267 TRM, The test method was initially based on a screening of calcined clays in portlandite-alkali-sulfate systems by isothermal calorimetry. Subsequently, the system formulation was more systematically studied and compared to strength development of blended cement mortar bars for a wide range of calcined kaolinitic clays. Remarkably good correlations between strength development and heat release were found. This was confirmed for other SCMs and other measurable system properties. In particular, bound water content and chemical shrinkage correlated remarkably well to the isothermal calorimetry results. The origin of this correspondence can be traced back to the hydration reaction. Indeed, it is the solidification of water that directly links heat release; chemical shrinkage; and, obviously, bound water content. This contribution traces back the origins and the first inroads leading up to the present state of development of the test method and concludes on future perspectives.

DOI:

10.14359/51716719


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: 

18-351

Date: 

July 1, 2019

Author(s):

E. F. Irassar, A. Tironi, V. L. Bonavetti, M. A. Trezza, C. C. Castellano, V. F. Rahhal, H. A. Donza, and A. N. Scian

Publication:

Materials Journal

Volume:

116

Issue:

4

Abstract:

Clay minerals are the most abundant raw materials for calcined pozzolans. Thermal transformation includes dehydration, dehydroxylation, mineral collapse, and neo-formation. Depending on the type and amount of clay mineral, and the nature and amount of associated minerals, the thermal treatment determines the pozzolanic activity. In this paper, 10 natural shales or clays (six illite, two kaolin, and two loess) from Buenos Aires Province (Argentina) were identified using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetry (TG). The thermal transformation was checked by XRD or FTIR and the electrical conductivity (EC) at the calcination window. The pozzolanic activity was evaluated using the Frattini test and strength activity index (SAI). The Frattini test gives positive results after 7 days and SAI is greater than 0.90 at 28 days, but the compressive strength development depends on main clay mineral. The EC was effective to evaluate the Ca(OH)2 fixation during the first time and it is related to the specific surface obtained.

DOI:

10.14359/51716717


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


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