Page 4 - March-2022

TECHNICAL PAPER

MECHANICAL AND MICRO

STRUCTURAL STUDIES OF

FIBER REINFORCED MORTAR

MIXTURES AT ELEVATED SHASWAT KUMAR DAS

TEMPERATURE SAMBITA SAHOO
SANJAYA KUMAR PATRO*
SYED M. MUSTAKIM

Abstract microstructure of the hardened concrete alters, and thus the
inherent properties of the concrete degrades . Furthermore,
[2]
The present study evaluates the effectiveness of two different the used aggregates plays a vital role in the performance of
fibers, i.e., steel and Polypropylene (PP), along with their the concrete/cementitious composite (CC) exposed to fire. It
hybridisation on the resistance properties of a mortar mix is reported that at 573°C, the crystal structure of quartz in a
at elevated temperature. The used mortar mix has been siliceous aggregate transforms from a low-temperature phase
made with a combination of silica fume and fly ash as mineral to an elevated temperature phase and thus this results in an
admixtures. To improve the temperature resistance property approximate volumetric expansion of 1 % . This volumetric
[3]
and sustainability of the fiber reinforced mortar (FRM), a expansion results in internal cracks and thus it leads to
combination of pumice and slag fines was used in place of reduction of load bearing capacity and other properties of
natural sand aggregates. The FRM was reinforced with only the CC. Therefore, to obtain better performance of the CC
steel, PP, and a mixture of steel and PP fibers. All FRM mixes under elevated temperature conditions, the used aggregate in
were then evaluated for high-temperature performance at 300°C CC must be thermally stable at high temperatures. Since the
and 600°C inside a furnace for a duration of 1 hour. After the minerals that are present in aggregates (Quartz in river sand and
exposure to the elevated temperature of the FRM mixes, their stone aggregates, calcium carbonate in lime stone aggregates,
performances were assessed through compressive strength etc. ) differ in their thermal expansion properties, the aggregate
tests, visual observation, and microstructural evaluations. The which show low thermal strains coefficient as well as negligible
results revealed that the steel fiber was the most efficient one residual strains can be contemplated as a better choice for the
to prevent spalling and reduction in compressive strength fire performance of CC .
[4]
at below and above 300°C as compared to the only PP and
PP+steel fibers reinforced FRM. The improvement in the residual The CC that is intended to retain its properties at fire exposures
compressive strength values of the steel fiber reinforced FRM must be designed with all the consideration discussed above,
was 59.52 % and 19.05 % at 300°C and 600°C, respectively, as and thus, it can sustain elevated temperature conditions.
compared to the ambient temperature values. Now a days, the demand for ultra-high performance or high
performance cementitious composites (UHPCC/ HPCC) is
Keywords: Fiber reinforced mortar, fiber reinforcement, increasing considering several advantages that includes high
temperature resistance, cement mortar, fiber, microstructural strength, workability and other durability aspects. The modern
study
buildings are constructed with high grade CC for several
reasons, such as less material consumption, more living space
1. INTRODUCTION and many more. A good resistance to fire exposure of these
UHPCC/ HPCC must be integrated to avoid consequence
The post fire-performance of the building materials especially caused by fire catastrophe and thus, a huge economic burden
the concrete plays a vital role in rehabilitation of the structures can be avoided that are being used to repair the fire danged
suffered from fire catastrophes. Concrete usually perform well structure.
at fire exposures, but the strength and durability properties
of concrete are considerably affected when exposed to high A. Cavdar concluded that each fiber types make contributions
[5]
temperatures due to chemical and physical changes . At high to the flexural strengths of mortars under high temperature.
[1]
temperatures, due to vaporization of pore water, dehydration However, this contribution decreases with increase in
of hydrated gel phases, and decomposition reactions the temperature. The compressive strengths of the mortars reduce

THE INDIAN CONCRETE JOURNAL | MARCH 2022 37
*Corresponding author : Sanjaya Kumar Patro, Email: skpatro_ce@vssut.ac.in