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International Concrete Abstracts Portal

Showing 1-5 of 47 Abstracts search results

Document: 

19-404

Date: 

September 1, 2020

Author(s):

Chaomei Meng, Liangcai Cai, Guanhu Wang, Xingang Shi, and Jianming Ling

Publication:

Materials Journal

Volume:

117

Issue:

5

Abstract:

Cross-tensioned prestressed concrete pavement (CTPCP) has superior mechanical and durable performance over ordinary concrete pavement. An approximate model to predict stresses and displacement of CTPCP under temperature loading is developed. Elasticplastic model is adopted to describe the performance of sliding layer between CTPCP and subgrade. The stresses in concrete are divided into friction introduced, curling, and prestressed components. Friction introduced component is obtained with the equivalent equation of CTPCP and curling component is obtained with Westergaard solution for concrete pavement with infinite length but finite width. Furthermore, influences of parameters, including length and thickness of slab, elastic modulus of concrete, frictional coefficient, space, angle and position of prestressed strands and reaction modulus of subgrade, on stresses and displacements are discussed. Results show that decreasing length and thickness of pavement, frictional coefficient, and elastic modulus of concrete are effective ways to reduce stress under temperature loading. Furthermore, decreasing space but increasing diameter of prestressed strands is another way to prevent too large tensile stress in CTPCP. Additionally, it seems to be more concise that the perfect plastic model is adopted to predict friction introduced stress in engineering application after comparative analysis of difference between to bilinear model and plastic model.

DOI:

10.14359/51725979


Document: 

18-455

Date: 

January 1, 2020

Author(s):

Ricardo Girardi, Denise Coitinho Dal Molin, and Fernando Antonio Piazza Recena

Publication:

Materials Journal

Volume:

117

Issue:

1

Abstract:

The dimensioning of structural systems in reinforced or prestressed concrete requires knowledge, among other properties, at least of the deformation modulus and compressive strength. However, concrete may present enough strength, whereas the structure rigidity might not be compatible with minimum required values for the verification of possible deformations. In Brazil, the estimate of deformation modulus is made using the NBR 6118 theoretical equation and internationally, the main theoretical models used are recommended in ACI 318, Eurocode 2, and the fib Model Code. But the bibliography indicates that there is no confidence in the models proposed. The present study aims to analyze the isolated effect of paste volume on the portland cement concrete deformation modulus. The results of the study indicate a significant influence of paste volume on the module value and, because a reduction in the amount of paste volume occurs, the concrete deformation modulus increases for all ages. The lack of consistency is also observed between experimental values and those obtained by theoretical equations, suggesting independency of the two magnitudes, compressive strength, and deformation modulus.

DOI:

10.14359/51719068


Document: 

18-305

Date: 

July 1, 2019

Author(s):

Lincy Varghese, V. V. L. Kanta Rao, and Lakshmy Parameswaran

Publication:

Materials Journal

Volume:

116

Issue:

4

Abstract:

The paper presents an experimental investigation on durability performance of colloidal nanosilica-added high-volume fly ash concrete (HVFAC) mixtures made with coarser unprocessed siliceous fly ash (with its proportion varying from 50 to 70% in the cementitious matrix) under chloride exposure. Chloride-induced corrosion is a serious durability concern for reinforced and prestressed concrete structures, and corrosion of reinforcement severely lowers the service life of structures. Therefore, an attempt has been made in this study to investigate, through rapid chloride permeability and chloride penetration tests, the performance of HVFAC mixtures under chloride ingress by migration and diffusion mechanisms. The permeability test results have been further corroborated with electrical resistivity of these concretes. The corrosion behavior of reinforcing bar embedded in test specimens made with these concretes was also investigated. The study indicated that the addition of small quantities of colloidal nanosilica significantly improved the resistance to chloride ingress and increased resistance to the corrosion of reinforcing bar in HVFAC.

DOI:

10.14359/51716711


Document: 

17-254

Date: 

May 1, 2019

Author(s):

Duo Zhang and Yixin Shao

Publication:

Materials Journal

Volume:

116

Issue:

3

Abstract:

Carbonation curing has demonstrated potential of improving concrete performance while facilitating carbon dioxide utilization. However, reinforcement corrosion behavior in carbonation-cured concrete has not been documented. This paper presents a study on chloride-induced corrosion in reinforced concrete subjected to carbonation curing. A special carbonation curing process was developed for precast non-prestressed applications. Performance of carbonation curing was evaluated by concrete compressive strength, pH value, and carbon dioxide uptake, while corrosion resistance of the carbonation-cured concrete was assessed by reinforcing bar mass loss and concrete chloride content. To understand the mechanism, concrete and cement paste were further characterized using mercury intrusion porosimetry, absorption, and electrical resistivity tests. Micromorphology was assessed by scanning electron microscopy. It was found that apart from rapid early-age strength gain, carbonation curing could significantly reduce chloride permeation in concrete concerning both total and free chloride contents. It was attributed to the reduced pore size and pore volume by calcium carbonate precipitation. With subsequent 28-day hydration, the carbonation-cured concrete displayed a pH over 12.0 at the surface of steel reinforcing bars and a micromorphology similar to the non-carbonated reference. The direct corrosion tests showed that the corrosion-induced mass loss of steel reinforcing bar was lessened by 50% in concrete subjected to carbonation curing.

DOI:

10.14359/51714461


Document: 

16-183

Date: 

September 1, 2017

Author(s):

A. Gil, F. Pacheco, R. Christ, F. Bolina, K. H. Khayat, and B. Tutikian

Publication:

Materials Journal

Volume:

114

Issue:

5

Abstract:

There is still a concern regarding concrete structures’ fire safety, mostly due to the occurrence of concrete spalling. Although many tests have already been carried out, there is no clear definition about the parameters of the factors that influence its occurrence. This paper aimed to compare three different types of concrete panels, with dimensions of 300 x 315 x 10 cm (124.0 x 39.4 x 3.9 in.), composed of reinforced concrete (RC), prestressed concrete, and polypropylene microfiber RC. The panels were exposed to the standard fire curve based on ISO 834, aged 28 days, measuring the temperatures in panels’ surfaces. Prestressed concrete panels experienced explosive spalling 18 minutes after the test began. RC panels and the panels with polypropylene microfiber addition maintained their integrity and structural stability for 240 minutes, failing in the thermal insulation criteria at 210 and 140 minutes, respectively. Although polypropylene microfiber concrete panels presented no spalling of concrete, conventional concrete panels attended the standardized criteria for a longer period due to its better thermal insulation.

DOI:

10.14359/51689715


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