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International Concrete Abstracts Portal

Showing 1-5 of 335 Abstracts search results

Document: 

20-188

Date: 

March 1, 2021

Author(s):

Noura Sinno, Matthew Piersanti, and Medhat H. Shehata

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

This paper presents tests that can be used collectively to provide a qualitative assessment of residual expansion in structures affected by alkali-silica reaction (ASR). The tests are applied to bridge barriers suffering different levels of ASR deterioration. These include testing extracted cores under different lab conditions, monitoring concrete elements under field condition, damage rating index (DRI) on cores, and measuring alkali levels in the affected concrete. Expansion of barriers with low deterioration level was double that of highly deteriorated barriers at 4.5 years. Similar results were reached through testing cores under laboratory conditions at 38°C (100°F) and 100% relative humidity, although the DRI showed the same increase in damage in both cores after testing. Testing cores under laboratory conditions until expansion ceases helps in predicting the minimum residual expansion. Soaking cores in alkaline solutions of different concentrations and finding the level required to trigger expansion helps in assessing the risk of future expansion.

DOI:

10.14359/51729330


Document: 

20-140

Date: 

March 1, 2021

Author(s):

Quang Tran and Jeffery Roesler

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

The concrete final set time (tf) is influenced by the concrete mixture and ambient conditions. Rapid measurement in the laboratory or field is difficult because of wet sieving or access and device coupling limitations. A non-contact, one-sided ultrasonic testing system (UTS) has been developed to monitor leaky Rayleigh wave (LR-wave) signals emitting from the specimen surface with an array of non-contract microelectromechanical systems (MEMS) receivers. A new ultrasonic set time (tUS) parameter was defined based on the initiation time of the LR-wave energy curve. The UTS technique implemented in the laboratory determined the tUS of multiple mortar mixtures to be between 270 and 1335 minutes. The tUS for the mortars were consistent with tf by ASTM C403 penetration resistance when the transmitter’s incident angle was set at 12 degrees. Different incident angles (12 to 60 degrees) influence the signal quality and tUS. The non-contact UTS was deployed on three concrete pavement sections and produced tf of 210, 266, and 289 minutes.

DOI:

10.14359/51729328


Document: 

18-301

Date: 

March 1, 2021

Author(s):

Erik Stefan Bernard

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

It is well known that creep can affect the serviceability of concrete structures, including tunnel linings made using fiber-reinforced shotcrete (FRS). However, the possible effect of creep on the strength of structures is seldom explicitly considered in design. For cracked FRS loaded in tension or flexure, creep rupture of the fiber-concrete composite, either by pullout or rupture of fibers, can lead to structural collapse, at least when no alternative load path exists. In the present investigation, the influence of fiber geometry and surface roughness on creep rupture (expressed as the time-to- collapse) of FRS panel specimens subjected to a sustained flexural-tensile load has been assessed. The results suggest that geometric aspects of fiber design influence the propensity of the fiber composite to suffer creep rupture at a crack, and that collapse primarily occurs as a result of fiber pullout rather than tertiary creep of individual fibers. For the fibers presently investigated, geometric aspects of fiber design appear to exert a greater influence on creep rupture of the fiber composite than the properties of the material comprising the fibers.

DOI:

10.14359/51730410


Document: 

20-079

Date: 

January 1, 2021

Author(s):

Prannoy Suraneni, Lisa Burris, Christopher R. Shearer, and R. Douglas Hooton

Publication:

Materials Journal

Volume:

118

Issue:

1

Abstract:

ASTM C618 and AASHTO M 295 specifications for fly ash represent the primary documents used by U.S. state and federal agencies to determine the suitability of a fly ash source for use in concrete. Other countries have broadly similar specifications for fly ash. The article compares specifications from the United States, Canada, Europe, Australia, and New Zealand, noting similarities and differences. Despite its common use, several criticisms of the ASTM C618 specification exist and are discussed in this document. Specifically, concerns exist regarding its dependence on strength activity index testing for determination of fly ash reactivity and strength generation potential, and loss on ignition for quantification of unburnt carbon content, as these tests relate somewhat poorly to performance of the fly ash in concrete. Recently developed test methods that could improve some of the most problematic components of the ASTM C618 specification are discussed.

DOI:

10.14359/51725994


Document: 

20-029

Date: 

November 1, 2020

Author(s):

M. R. Sakr, M. T. Bassuoni, R. D. Hooton, T. Drimalas, H. Haynes, and K. J. Folliard

Publication:

Materials Journal

Volume:

117

Issue:

6

Abstract:

Physical salt attack (PSA) is a potential deterioration mechanism in porous materials, including concrete, exposed to salt-laden environments. Damage occurs as salt crystals grow in the near-surface pores causing tensile stresses on the pore walls higher than the tensile capacity of concrete, which can lead to surface scaling similar in appearance to that of freezing-and-thawing damage. This paper compiles, synthesizes, and analyzes current knowledge/research on this topic in terms of the mechanisms of damage, test procedures, damage assessment methods, most influential factors, protection against PSA, and code/guideline provisions. Moreover, key aspects that require further investigation are highlighted, along with a proposed classification for the resistance of concrete to PSA and mitigation strategy.

DOI:

10.14359/51727015


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