Effects of Fly Ash on Mechanical Properties of 10-year-old Concrete Prepared with Recycled Concrete Aggregates

Title: Effects of Fly Ash on Mechanical Properties of 10-year-old Concrete Prepared with Recycled Concrete Aggregates
Author(s): Chisun POON, Shicong KOU
Paper category : conference
Book title: 2nd International Conference on Waste Engineering and Management - ICWEM 2010
Editor(s): J.Zh. Xiao, Y. Zhang, M.S. Cheung and Reuben P. K. Chu
Print-ISBN: 978-2-35158-102-5
e-ISBN: 978-2-35158-103-2
Publisher: RILEM Publications SARL
Publication year: 2010
Pages: 46 - 59
Total Pages: 14
Nb references: 13
Language: English

Abstract: This paper presents the findings of a long-term study on the mechanical properties of recycled aggregate concrete (RAC) containing 25%, 35% and 55% Class-F fly ash, as cement replacement, after curing in water and an outdoor exposure condition for 10 years. Variations in compressive strength, splitting tensile strength, modulus of elasticity with time are determined and discussed. It was found that after 10 years, the compressive strength and modulus of elasticity of the concrete mixture with 100% recycled aggregate was still lower than that of the control concrete. Over this period, the highest gain of compressive strength and modulus of elasticity was recorded for the concrete mixture prepared with 55% fly ash RAC followed by 35% fly ash RAC and 25% fly ash RAC. Even though the 55% fly ash RAC at the age of 28 days had lower compressive strength than other concretes, it attained the highest strength gain of more than 105% between 28 days and 10 years. In general, the compressive and splitting tensile strengths of the water cured concrete were higher than that of outdoor cured specimens. But the modulus of elasticity of the water cured and outdoor exposure concrete were similar. The study results show the optimal mix proportions for preparing RAC mixtures is by using 50% RA as a replacement of natural aggregates and using 25% FA as a replacement of OPC.

Online publication: 2011-01-25
Publication type : full_text
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