Problems durability of concrete structures are in the interest of engineers, practitioners, and researchers due to the potential negative consequences for the operation of concrete and high repair costs, despite the advanced technology to produce concrete and extensive practical knowledge.
Following this objective, this work is a part of an on-going project developed in the materials laboratory of LAB Casey Concrete, Co. Wexford in cooperation with Warsaw University of Technology, Poland,
Concrete is degradable by cycles of freezing and thawing. The impact of 200 cycles of freezing and thawing on the durability of concrete was examined by replacing CEM II/A-L with GGBS at 30%, 50% and 70%. A control mix at 0% GGBS was also cast. The w / c = 0.45 was consistent throughout the trials and mixes where considered with and without air entraining agent (AEA). All concrete mixtures were controlled to have a similar slump by using a dosage of superplasticizer. Concrete was assessed for water absorption, tensile strength, loss of comprssive strength, and loss of mass.
Performance advantages were achieved by replacing CEM II/A-L with GGBS in the range of 30%-50%. Such advantages are increased 28 and late strength compressive and tensile strength, reduction in water absorption, reduction in mass loss and strength loss after 200 freeze/thaw cycles The level of compressive strength of concrete samples not aerated and aerated subjected to freezing and thawing, control samples and samples after 120 days of ripening in curing tank water is significant. Determination of mass loss of samples subjected to 200 cycles of freezing and thawing in all mixes resulted in compressive strength ≤20% and in mass loss ≤ 5% which conforms to the Polish standard, PN-B-06250, requirement which represents severe winter conditions.
The air void structure of the concrete was studied using the Air Void Analyzer which determined whether the differences in the composition of concrete mix would influence the concrete durability with a cycle of freezing and thawing. The results indicate that all concrete mixes with air entrainment showed better freezing and thawing resistance than without air entrainment.
The study demonstated the Freeze-thaw resistance of CEM II/A-L and GGBS combinations at 30%, 50% and 70% after 200 cycles of freezing and thawing resulting in durable concrete for XF exposure class.
Professor Pawel Lukowski. Head of the Department of Building Materials Engineering. Warsaw University of Technology
Dr. Eng. Joanna Julia Sokolowska. Department of Building Materials Engineering. Warsaw University of Technology
MSc. Eng. Ali Salih Technical and Quality Manager – Casey Concrete, Gorey Co. Wexford