19-08-2014, 10:20 AM
GEOPOLYMER CONCRETE : A REVIEW OF DEVELOPMENT AND
OPPORTUNITIES
GEOPOLYMER CONCRETE.pdf (Size: 160.46 KB / Downloads: 35)
Abstract
Geopolymer results from the reaction of a source material that is rich in silica
and alumina with alkaline liquid. It is essentially cement free concrete. This material is
being studied extensively and shows promise as a greener substitute for ordinary
Portland cement concrete in some applications. Research is shifting from the chemistry
domain to engineering applications and commercial production of geopolymer concrete.
It has been found that geopolymer concrete has good engineering properties with a
reduced global warming potential resulting from the total replacement of ordinary
Portland cement. The research undertaken at Curtin University of Technology has
included studies on geopolymer concrete mix design, structural behavior and durability.
This paper presents the results from studies on mix design development to enhance
workability and strength of geopolymer concrete. The influence of factors such as,
curing temperature and régime, aggregate shape, strengths, moisture content,
preparation and grading, on workability and strength are presented. The paper also
includes brief details of some recent applications of geopolymer concrete.
Introduction
1.1. Use of concrete and environment impact
Utilization of concrete as a major construction material is a worldwide phenomenon and the
concrete industry is the largest user of natural resources in the world (1). This use of concrete is driving
the massive global production of cement, estimated at over 2.8 billion tonnes according to recent industry
data (2). Associated with this is the inevitable carbon dioxide emissions estimated to be responsible for 5
to 7% of the total global production of carbon dioxide (3). Significant increases in cement production have
been observed and were anticipated to increase due to the massive increase in infrastructure and
industrialization in India, China and South America (
2. Geopolymer Concrete Development
Geopolymer concrete is concrete which does not utilize any Portland cement in its production.
Rather, the binder is produced by the reaction of an alkaline liquid with a source material that is rich in
silica and alumina. Geopolymers were developed as a result of research into heat resistant materials
after a series of catastrophic fires (5). The research yielded non-flammable and non-combustible
geopolymer resins and binders.
Geopolymer Precast Opportunities
Gourley and Johnson (13) have reported the details of geopolymer precast concrete products on
a commercial scale. The products included sewer pipes, railway sleepers, and wall panels. Reinforced
geopolymer concrete sewer pipes with diameters in the range from 375 mm to 1800 mm have been
manufactured using the facilities currently available to make similar pipes using Portland cement concrete.
Tests performed in a simulated aggressive sewer environment have shown that geopolymer concrete
sewer pipes outperformed comparable Portland cement concrete pipes by many folds. Gourley and
Johnson (13) also reported the good performance of reinforced geopolymer concrete railway sleepers in
mainline tracks and excellent resistance of geopolymer mortar wall panels to fire.
Siddiqui (14) and Cheema et al (15) demonstrated the manufacture of reinforced geopolymer
concrete culverts on a commercial scale. Tests have shown that the culverts performed well and met the
specification requirements of such products. In this study, reinforced geopolymer concrete box culverts of
1200 mm (length) x600 mm (depth) x1200 mm (width), and 100 mmx200 mm cylinders were
manufactured in a commercial precast concrete plant located in Perth, Western Australia. The dry
materials were mixed for about 3 minutes. The liquid component of the mixture was then added, and the
mixing continued for another 4 minutes. The geopolymer concrete was transferred into a kibble from
where it was then cast into the culvert moulds (one mould for two box culverts) and cylinder moulds. The
culverts were compacted on a vibrating table and using a hand -held vibrator. The cylinders were cast in 2
layers with each layer compacted on a vibrating table for 15 seconds. The slump of every batch of fresh
concrete was also measured in order to observe the consistency of the mixtures. After casting, the cylinders were covered with plastic bags and placed under
Concluding remarks
Basic mixture proportions characterized by 75% aggregate to total mass, alkaline liquid to fly ash
of 0.35 (analogous to water to cement ratio) and elevated temperature curing results in a high strength
geopolymer concrete. Ambient curing of geopolymer has been trialed and further mixture trials with
ambient curing are presently being researched.
Temperature specification for curing should be correlated to actual specimen temperature for
high and very high strength geopolymer concretes, monitoring temperature may be warranted if strength
is critical and when steam curing, placement of the steam vents or hoses and control thermocouples as
well as specimens is important. The introduction of a rest day, that is ambient curing for 24 hours prior to
steam curing, resulted in elevated compressive strengths of the order of 20%. As with Portland cement
concrete, strength was increased and workability and ease of compaction decreased with a reduction in
added water. Strength gain at one day is around 80% of the 28 day strength when cured for 24 hours.
As with Portland cement concrete, the aggregate moisture content can be accommodated by
adjusting the total water added to a geopolymer concrete mixture without sacrificing strength or
workability. Additionally, the effect of aggregate particle shape and grading on the properties of
geopolymer concrete is similar to that of Portland cement concrete.
The paper presented brief details of geopolymer precast concrete products. The economic
benefits and contributions of geopolymer concrete to sustainable development are also outlined.