<abstract xmlns="http://www.w3.org/1999/xhtml">Air contents of concrete are necessary for concrete durability in freeze-thaw exposure. According to the Finnish concrete code, the target value for air content varies between 4% and 5.5% for XF - exposure classes. Lately in Finland, some cases showed an elevation of air contents up to 15% in fresh air-entrained concrete at construction site and in drilled concrete samples.The objectives of this study were to investigate the stability of air entrainment by measuring the air content elevation 30 minutes and 60 minutes after concrete mixing and investigating the concrete sensitivity to segregation. Composition of concretes used in this study include 7 different combination of PCE based superplasticizer and air-entraining agent admixtures, cement content of 425 kg/m3, two consistency classes S3 with water to cement ration of 0.33 and F5 with water to cement ration of 0.38. One cement type was used for all concrete mixes. The concretes were mixed for 2 minutes and 5 minutes mixing times.The results show that the elevation of the air content of fresh concrete depends on the consistency of the concrete and on the used combination of superplasticizer and air-entraining agents. The higher consistency classes concretes have more risk of air elevation with some combinations of PCE-based superplasticizers and air-entraining agents. The results also indicate that short mixing time would not be enough to achieve total effectivity of some air-entraining agents, especially for higher consistency classes concrete.</abstract>

Air contents of concrete are necessary for concrete durability in freeze-thaw exposure. According to the Finnish concrete code, the target value for air content varies between 4% and 5.5% for XF - exposure classes. Lately in Finland, some cases showed an elevation of air contents up to 15% in fresh air-entrained concrete at construction site and in drilled concrete samples.The objectives of this study were to investigate the stability of air entrainment by measuring the air content elevation 30 minutes and 60 minutes after concrete mixing and investigating the concrete sensitivity to segregation. Composition of concretes used in this study include 7 different combination of PCE based superplasticizer and air-entraining agent admixtures, cement content of 425 kg/m3, two consistency classes S3 with water to cement ration of 0.33 and F5 with water to cement ration of 0.38. One cement type was used for all concrete mixes. The concretes were mixed for 2 minutes and 5 minutes mixing times.The results show that the elevation of the air content of fresh concrete depends on the consistency of the concrete and on the used combination of superplasticizer and air-entraining agents. The higher consistency classes concretes have more risk of air elevation with some combinations of PCE-based superplasticizers and air-entraining agents. The results also indicate that short mixing time would not be enough to achieve total effectivity of some air-entraining agents, especially for higher consistency classes concrete.

Stability of Air Content in Fresh Concretes with PCE-Based Superplasticizers

Nordic Concrete Research

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

{"article-title":"Stability of Air Content in Fresh Concretes with PCE-Based Superplasticizers"}

Air contents of concrete are necessary for concrete durability in freeze-thaw exposure. According to the Finnish concrete code, the target value for air...

Stability of Air Content in Fresh Concretes with PCE-Based Superplasticizers

Published Online: Jul 20, 2019

Page range: 145 - 158

Received: Sep 26, 2018

Accepted: Jun 18, 2019

DOI: https://doi.org/10.2478/ncr-2019-0093

Keywords
Air content, superplasticizer, air-entraining, admixtures, concrete

© 2019 Fahim Al-Neshawy et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Stability of Air Content in Fresh Concretes with PCE-Based Superplasticizers

Published Online: Jul 20, 2019

Page range: 145 - 158

Received: Sep 26, 2018

Accepted: Jun 18, 2019

DOI: https://doi.org/10.2478/ncr-2019-0093

KeywordsAir content, superplasticizer, air-entraining, admixtures, concrete

© 2019 Fahim Al-Neshawy et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Keywords
Air content, superplasticizer, air-entraining, admixtures, concrete