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International Concrete Abstracts Portal

Showing 1-5 of 49 Abstracts search results

Document: 

20-207

Date: 

May 1, 2021

Author(s):

Lihe Zhang, Dudley R. Morgan, Iain Kirk, Anastasia Rolland, and Robert Karchewski

Publication:

Materials Journal

Volume:

118

Issue:

3

Abstract:

Wet-mix shotcrete has been used more and more for structural applications in the past few decades. Recently, wet-mix shotcrete was successfully used to construct a mass structural wall with congested reinforcement and minimum dimensions of 1.0 m in a sewage treatment plant. A low-heat shotcrete mixture that included up to 40% slag was proposed for shotcrete application. A preconstruction mockup was shot to established proper work procedures for shotcrete application and qualify the shotcrete mixture and shotcrete nozzlemen. Extraction of cores and cut windows from the mockup confirmed proper consolidation around the congested reinforcement. A thermal control plan was developed, which included laboratory and field testing requirements, thermal analysis modeling with a three-dimensional (3-D) finite element program, and thermal control requirements, including installation of cooling pipes and thermal blankets. Shotcrete proved to be an efficient means for mass concrete structural construction. Thermal control for mass shotcrete construction was studied, and the proposed thermal control plan was proved to function properly. The general guidance for mass shotcrete construction is provided.

DOI:

10.14359/51730423


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: 

18-247

Date: 

July 1, 2020

Author(s):

Nattapong Paewchompoo, Wanchai Yodsudjai, and Prinya Chindaprasirt

Publication:

Materials Journal

Volume:

117

Issue:

4

Abstract:

The objective of this research was to clarify the mechanism of concrete cover cracking time due to reinforcement corrosion in steel fiber-reinforced concrete. An experimental study and analytical study were conducted. For the experimental study, 3 in. (76.2 mm) diameter and 6 in. (152.4 mm) length cylindrical concrete specimens with reinforcement placed in the middle were prepared. Conventional and steel fiber-reinforced concrete with three levels of compressive strength were used in the study. A strain gauge was installed along the specimen’s circumference and the corrosion of reinforcement was accelerated using anodic DC current. Concrete surface strain and impressed anodic current were recorded via a data logger and a multimeter, respectively. Concrete cover cracking time was also investigated. After corrosion acceleration, reinforcement weight loss was evaluated and internal pressure due to the reinforcement corrosion product was calculated. The analytical study was conducted using finite element with four-node bilinear plane strain in a two-dimensional (2-D) model. In the finite element method (FEM) model, the reinforcement was removed and the internal pressure result from the expansion of corrosion products was applied, similar to the problem of cylinder under constant internal pressure. The relationship between concrete surface strain and internal pressure from the analytical study was compared with the experimental study. It was found that corrosion current density of the reinforcement embedded in the fiber-reinforced concrete was higher than that of conventional concrete. Concrete cover cracking time increased with increase of concrete tensile strength. In addition, the relationship between concrete surface strain and the internal pressure could be predicted by the FEM results within an acceptable margin of error.

DOI:

10.14359/51724620


Document: 

19-057

Date: 

May 1, 2020

Author(s):

A. Pczieczek, C. Effting, A. Schackow, I. Ribeiro Gomes, and D. V. Ferronato da Silva

Publication:

Materials Journal

Volume:

117

Issue:

3

Abstract:

This work aimed to analyze the physical and mechanical properties of mortar with the addition of fly ash and rubber concentrations used on building walls. The mortars had 5 and 10% of fine aggregate mass replaced by rubber and added fly ash in proportions of 10 and 20% according to the volume of cement. Ground fly ash addition in the mortar, in turn, increased the compressive strength by 18% at 28 days compared to the reference mortar, assuring a greater durability against sulfate attacks and presenting lower mass loss during exposure to sodium sulfate. The mortar containing 20% of ground fly ash and 5% of rubber presented tensile adhesion strength of 0.33 MPa at 65 days. A numerical simulation of the mortar microstructure was carried out using the finite element method to study its thermomechanical behavior. Stress distribution and cracking field of the model were also obtained.

DOI:

10.14359/51724594


Document: 

18-322

Date: 

September 1, 2019

Author(s):

Mahmoud Shakouri, Naga Pavan Vaddey, and David Trejo

Publication:

Materials Journal

Volume:

116

Issue:

5

Abstract:

The binding of chlorides by the hydration products of cement in concrete is one of the factors that affects the rate of chloride ingress, which in turn can influence the time to corrosion initiation of reinforcing steel in concrete. Theoretical assessments of the influence of chloride binding on the chloride ingress and service life estimates are often based on empirically developed chloride binding isotherms to account for the interaction between the concrete matrix and external chlorides. While being useful, these assessments disregard the binding influence of admixed chlorides that may be present in the concrete from the early stages of hydration. It is suspected that the presence of free admixed chlorides can influence the diffusivity of chlorides in concrete. This work focuses on determining the binding behavior of admixed chlorides and proposes a modified diffusion model that takes chloride binding from admixed and external chlorides into consideration.

DOI:

10.14359/51716833


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