Johnny Ching Ming Ho Senior Lecturer School of Civil Engineering

Johnny Ching Ming Ho
Senior Lecturer
School of Civil Engineering
Faculty of Engineering,
Architecture and
Information Technology
Migrating to the use of low-carbon-footprint high-performance concrete
with multi-sized fillers
High performance concrete (HPC) has been widely advocated thanks to its
superior performance in strength, workability and segregation stability.
However, the cement content in HPC is normally very high at about 40%, which
increases the carbon footprint, cost of production and impair the dimensional
stability of concrete. To this, the speaker proposes to use multi-sized fillers
(limestone and superfine sand in this study) coupled with other supplementary
cementitious materials SCM (i.e. fly ash and silica fume) to reduce the cement
paste, and hence embodied carbon content and production cost of concrete.
Some test data on fresh concrete containing two paste volume of 50% and 40%,
as well as water binder ratios of 0.5 and 0.4, with and without using fillers will
be presented. From the results, it can be observed that up to 25% partial
replacement of cement with limestone and/or super-fine sand, the workability
performance of concrete in terms of slump flow, passing ability, filling ability
and segregation stability is not adversely affected. The results obtained are
inspiring as concrete with even lower paste volume could be produced without
jeopardizing the workability performance given that more fillers and
superplasticiser are provided. This new type of “low-paste concrete” will not
only reduce the carbon footprint of the construction, but also improve the
dimensional stability by reduces early thermal cracking, long term creep and
shrinkage that is capable of prolonging the structural design life and contributing
significantly towards a more sustainable built environment.
Dr Johnny Ho is a Senior Lecturer in the School of Civil Engineering, The
University of Queensland. Before joining the university in 2013, he has been
working as an Assistant Professor in The University of Hong Kong for 6 years.
Regarding practical experience, Dr Ho worked in both Hong Kong and Brisbane
offices of Arup on some large scale infrastructure projects such as The
Stonecutters Bridge in Hong Kong and the Ipswich Motorway Upgrade (Wacol
to Darra) in Brisbane. Dr Ho’s research interests are on low-carbon, low-cost
high-performance concrete using filler technology and packing theory, as well as
its application in the concrete-filled-steel-tube columns with external