Pressure reliance on mix composition and replacement level of expanded polystyrene (EPS) in dry mix mortar / Amirah Mohamad Juri

In recent decades, the approach of using dry mix mortar in the construction industry is
crucial due to high demand of concrete block for building materials either for load
bearing or non-load bearing structure. Dry mix is widely used by manufacturers as it
can be produced quickly and higher production because it’s casted by machine. River
sand is one of the natural resources used to produce building materials which is now
depleting. Besides that, the consumption of polystyrene has extremely increased due to
its many applications such as packaging purpose and consumer goods thus generated to
the increment of polystyrene waste. Hence, the introduction of lightweight dry mix
mortar incorporating with EPS executed with appropriate pressure is one of feasible
options to overcome the issue. The objective of this study is to determine the best
replacement of expanded polystyrene (EPS) powder in the design mix composition ratio
of 1:3.0, 1:3.5 and 1:4.0, cement to sand with pressure of 500, 600 and 700 psi in
achieving the targeted density between range of 1200 to 1800 kg/m3 and compressive
strength between range of 5 to 7 N/mm2 that suit it as lightweight and for non-load
bearing purposes. The pressure was applied to compress the fresh mortar in the mould
in order to produce a preform dry mix mortar cube size 100 mm x100 mm x 100 mm.
The EPS was mixed with different percentages of 35%, 40%, 45%, 50% and 55% as
partial replacement of sand and 0% as control. A constant water cement ratio of 0.37
was used throughout the study and exposure to air-drying for a period of 7 and 28 days
were considered in this study. The density and compressive strength tests were
conducted to obtain the best replacement of EPS in dry mix mortar which achieve the
targeted value. It is shows that 55% of EPS replacement in mix composition of 1:3.0,
1:3.5 and 1:4.0 at all pressures can be consider as appropriate mix proportion at 28 days
of age. The density for all specimens also was found to be below than 1800 kg/m3, where
it can be considered as lightweight concrete. However, the most appropriate mix was
selected at 55% of EPS in mix design 1:3.5 subjected to pressure 500, 600 and 700 psi
where compressive strength marked 5.010 N/mm2, 5.045 N/mm2 and 5.994 N/mm2
respectively. Scanning Electron Microscopy (SEM) also was carried out in determining
the morphological of the EPS dry mix mortar based on mix 1:3.5 at three (3) pressures.
From the study, it can be suggested that the properties of EPS and pressure exerted play
a crucial role to the density, thus influences the strength of mortar cube. Further study
can be conducted by using mix 1:3.5 with higher level of EPS replacement to achieve
higher compressive strength within the range of non-load bearing structure but lower in
density.