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International Concrete Abstracts Portal

Showing 1-5 of 335 Abstracts search results

Document: 

18-315

Date: 

March 1, 2021

Author(s):

John S. Lawler, Jonah C. Kurth, Stephen M. Garrett, and Paul D. Krauss

Publication:

Materials Journal

Volume:

118

Issue:

2

Abstract:

Reliability-based durability design of reinforced concrete structures requires a probabilistic service life modeling approach. Probabilistic service life modeling of chloride-induced corrosion should consider the statistical distributions of key parameters that influence corrosion initiation and subsequent damage. For typical reinforced concrete structures (such as bridge decks), these are chloride exposure, chloride penetration resistance of the concrete, chloride-induced corrosion threshold, depth of concrete cover, and corrosion propagation time. Assessing the impact of the use of corrosion-resistant reinforcement, such as epoxy-coated reinforcing bars (ECR), is typically performed through a selection of the chloride threshold and/or propagation time. This paper provides recommendations for statistical distributions for the chloride threshold to be used in service life modeling for structures containing carbon steel and ECR based on both experimental work reported in the literature and field investigations of existing structures conducted by the authors.

DOI:

10.14359/51730411


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: 

19-214

Date: 

January 1, 2021

Author(s):

Wei Yang, Hassan Baji, Chun-Qing Li, and Wenhai Shi

Publication:

Materials Journal

Volume:

118

Issue:

1

Abstract:

In durability design of concrete structures using performance-based framework, hydraulic sorptivity of concrete can be used as a key indicator. In this paper, a probabilistic methodology considering variability of hydraulic properties of concrete components, namely the mortar, aggregates, and interfacial transition zone (ITZ), is developed. Evaluation of the effective sorptivity of concrete is based on a rigorous nonlinear finite element (FE) analysis at the meso-scale level, which is verified using available experimental results. Using the response surface method (RSM), a conceptual model relating effective hydraulic sorptivity of concrete to aggregate volume fraction and hydraulic properties of mortar and the ITZ is derived. The proposed probabilistic methodology can be used for durability design of concrete structures. It is found that for high aggregate volume fractions the variability of hydraulic sorptivity is high due to increasing volume of ITZ.

DOI:

10.14359/51726996


Document: 

19-512

Date: 

November 1, 2020

Author(s):

Job Thomas, Ardra Mohan, and Dhannya K. K.

Publication:

Materials Journal

Volume:

117

Issue:

6

Abstract:

In this study, copper slag and lime-activated fly ash were used for the manufacturing of cold-bonded aggregates. Cold-bonded copper slag fly ash (CSFA) aggregates were manufactured by varying copper slag content. The aggregate type with 37.5% copper slag and 62.5% fly ash showed optimum strength properties and was selected for the production of CSFA aggregate concrete. The strength and durability properties of concrete with a varying replacement ratio of CSFA aggregate from 0 to 100% at normal temperature and at elevated temperatures of 200, 400, and 600°C were investigated. The results show that concrete containing CSFA aggregate can be ideally used as a construction material up to a temperature of 400°C and as 100% replacement for coarse aggregate. A prediction model has been formulated using multiple regression analysis for the mechanical strength properties of concrete at different replacement ratios and exposure temperatures. A mixture design methodology is also proposed for the concrete containing CSFA aggregates.

DOI:

10.14359/51727000


Document: 

19-449

Date: 

November 1, 2020

Author(s):

Sarah De Carufel, Andrew Fahim, Pouria Ghods, and Rouhollah Aalizadeh

Publication:

Materials Journal

Volume:

117

Issue:

6

Abstract:

This paper presents a model developed to predict the internal relative humidity (RH) of concrete during drying. The model makes use of simplified inputs, including the concrete mixture design and the cement Bogue composition, thus making it accessible to engineers and practitioners. These inputs are used to separately determine the permeability of both liquid and vapor phases, hence solving for moisture transport through an empirical derivation of the (de) sorption isotherm, total porosity, and pore tortuosity. The model is validated using previously published literature data as well as experiments designed specifically for model validation. The model was found successful in predicting RH profiles for the validation data with the simple inputs required. However, it was found that in cases where the standardized ASTM F2170 method is used to measure RH, the agreement between the model and experimental data decreases. This was found to be related to errors associated with performing humidity measurements within cavities drilled in concrete. Such errors are discussed, and room for improvement in in-place humidity measurements is proposed. Finally, the model is used to validate the use of RH measurements at a specific concrete depth to evaluate the susceptibility of moisture-sensitive flooring to failures.

DOI:

10.14359/51728146


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