Abstract:
The building industry is facing challenges in terms of resource management, excessive
energy consumption, and CO 2 emissions resulting from the extended usage of concrete
made primarily of Portland cement and ceramic bricks. Geopolymer technology has
caught the attention of many researchers in an attempt to promote the development of
sustainable concrete. This study investigates how to utilize diatomaceous earth as a
resource for geopolymers. Little research has been conducted on the use
of diatomaceous earth as a stand-alone geopolymer precursor or in combination with
natural fibres and/or polymeric additives, although, it has become a significant source
of industrial waste that ends up in landfills. The primary goal of the study was to
develop and analyse the performance properties of diatomaceous earth-based
geopolymer concrete incorporated with sisal fibres and high-density polyethylene
wastes. The specific objectives were: to characterize diatomaceous earth in relation to
chemical, physical, thermal, and mineralogical features; fabricate geopolymer concrete
from alkaline activated diatomaceous earth with the addition of sisal fibres and HDPE
waste; analyze the effect of incorporating sisal fibres and HDPE wastes on the
performance properties of the geopolymer concrete; and to generate correlational and
predictive models for the developed geopolymer performance properties. The
methodology involved using standard techniques to characterize diatomaceous earth
that had been calcined at 600 °C and in its raw state. After 28 days of curing, the alkaline
(lime)-activated specimens were tested for their mechanical, physical, and thermal
characteristics. The geopolymer performance correlation and predictive models were
developed using linear and polynomial regression approaches. The chemical
composition showed that silica was the main constituent, making up 88.12% of the raw
sample and 89.92% of the calcined sample. The optimum material mixture for the lime-
activated geopolymers was found to contain 83.75 %wt diatomite, 15 %wt lime, and
1.25 %wt sisal fibres yielding 2.72 MPa of compressive strength, 0.72 g/cm 3 bulk
density and 0.110 W/mK thermal conductivity. In comparison to the acceptable
standards for the concrete masonry units, as stated in ASTM C1634 and ASTM C129,
the properties of the lime-activated diatomite-based concrete suggested the necessity
for modification. The optimum performance outcomes of the modification, which
comprised substituting sodium hydroxide and sodium silicate activation for lime
activation, were a compressive strength of 34.10 MPa, a bulk density of 1.32 g/cm 3 ,
water absorption of 13.93 %, and 0.322 W/mK thermal conductivity. Bulk density and
water absorption showed a strong correlation with compressive strength. The diatomite
under investigation is a class F pozzolan, and it can be used to produce sisal-fibre
reinforced geopolymer concrete with acceptable performance for masonry walling
materials. There was a strong correlation between certain performance characteristics
and the amount of sisal fibre incorporation. Additionally, strong correlations between
performance properties were found. The practicality, economic viability, and durability
of cellulosic fibre-reinforced geopolymer composites were however deemed to require
further study. The development of standards and specifications for the manufacturing
of geopolymers as well as their functional properties was also recommended.