The Effect of Metakaolin on the Compressive Strength of Recycled Aggregate Concrete
No Thumbnail Available
Date
2019-10-04
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
Large quantity of construction and demolition waste has been produced due to the
economic growth of the world. However, the most common way to dispose of such waste
is by landfill. Without proper sorting and handling of it, as time passes, landfills will cause
many environmental issues. Furthermore, the continuous utilization of natural aggregates
will cause resource scarcity. The potential solution for these problems is the recycling of
aggregates. Still, due to strength reduction associated with recycled aggregates, its usage
is restricted for low strength concrete.
On the other hand, incorporation of metakaolin as a cement replacement in recycled
aggregate concretes could pave a path towards a sustainable future. In addition, kaolin, the
original material from which metakaolin is produced, is found in large quantities in
Ethiopia which makes it an attractive option.
This research presents the effect of metakaolin as a cement replacement on the properties
of fresh and hardened recycled coarse aggregate concrete as well as natural coarse
aggregate concrete. The recycled coarse aggregate is extracted from first-hand cast
laboratory cubes with known average compressive strength. Different types of concrete
mixtures are tested: concrete made with natural coarse aggregate as a control concrete,
concrete made with recycled coarse aggregate (0%, 25%, 50%, 75% and 100%
replacement of natural coarse aggregate), concrete made with metakaolin as cement
replacement (0%, 6%, 12%, 18%, and 24% replacement of cement), and concrete made
with recycled coarse aggregate (0%, 25%, 50%, 75% and 100% replacement of natural
coarse aggregate) with metakaolin as cement replacement (6%, 12%, and 18%
replacement of cement). Additionally, a separate experiment has been conducted to check
the production of metakaolin from locally found kaolin samples.
The outcomes of this research show that the use of metakaolin as a cement replacement
improved the compressive strength of recycled coarse aggregate concrete and even
resulted in a compressive strength almost equal to natural coarse aggregate concrete. In
addition, this thesis has shown that metakaolin can be produced from locally occurring
kaolin by thermal activation.
Description
Keywords
Recycled Aggregate Concrete, Metakaolin, ompressive Strength