Page 5 - March-2022

TECHNICAL PAPER

under excessive temperature or with fiber addition. The lowest of the UHPCC [10-11] . But the, there exist no study on hybrid
decrease in compressive strength is at 0.5–1.5 % for carbon fiber reinforced mortar mixtures that has incorporated the
fiber if all temperature conditions are taken into consideration. combination of FS-FA with pumice and slag aggregates.
The optimum fiber addition ratios of the samples containing Therefore, this study was conducted taking SF and FA as cement
polypropylene (PP) and glass fibers are 0.5 % by volume. And for replacement along with pumice and BFS slag aggregates to
PVA, it is between 0.5 % and 1.5 % by volume. manufacture fiber reinforced mortar mixtures (FRM ) to sustain
at elevated temperature. Three different fiber reinforcement
Similarly, Aydin et al. investigated the influence of high volume
[6]
of pozzolanic materials (25 % GBFS + 25 % silica fume) in binder combination were used to evaluate their effect on the
phase of mixtures of UHPCC under autoclave curing conditions. compressive strength before and after the high temperature
Compressive and flexural strength of high strength mortar treatment followed by microstructural studies. A complete
increased by using steel fibers and increased slightly by using replacement of fine aggregates with BF slag and pumice
PP fibers at 20°C. On the other hand, steel fibers also increased aggregates was done to improve the post-fire performance
the compressive and flexural strength, while PP fibers caused properties along with the sustainability of the FRM.
some reduction in both the compressive and flexural strength
under autoclave curing before high temperature exposure. Test 2. EXPERIMENTAL DETAILS
results indicated that, using PP and steel fibers in high strength
and ultra-high strength autoclaved mortars is a promising 2.1 Materials
development which conserves almost all compressive strength
characteristics without spalling up to 600°C temperature even The cement used in all mixtures of this experimental work is the
with a high silica fume content under a saturated condition. Ordinary Portland Cement of grade 43 manufactured confirming
IS: 8112 (2013). The specific gravity, fineness, consistency and
Furthermore, Aydın and Baradan studied the alteration in soundness of used cement is found to be 3.15, 5 %, 32 %
[7]
mechanical properties of the mortars containing fly ash (FA) as and 2 mm as per IS 4031, respectively. Due to the pozzolanic
binder alternative and pumice as an aggregate alternative. It property of fly ash (FA) it was used as a supplementary
has been found that the specimen with 60 % replacement of cementitious material (SCM). In this research work, a class-F
cement with FA indicates a gain of 19 % strength in comparison fly ash (ASTM classification) with specific gravity of 2.52 was
to control specimen at 900°C because of stronger aggregate- used which was obtained from HINDALCO power plant. Silica
cement paste ITZ and ceramic bond formation. Similarly, Pumice fume (SF) is an ultra-fine reactive powder and the addition of it
aggregate mortar with cement as a binder (FA0) has excellent can improve properties of concrete particularly in compressive
high-temperature resistance up to 600°C. This mortar confirmed strength [12] . Bond strength and abrasion resistance are also
best approximately 4 % compressive strength loss and 32 % improved due to pozzolanic reactions between silica fume and
flexural strength loss at 600°C (cooled in the air). However, at the free calcium hydroxide (CH) in the cement paste, thus SF is
temperature of 900°C, the mechanical properties of this mixture also used as a SCM in this study along with FA addition. Here
dropped significantly. The residual compressive strength and steel slag was used as fine aggregate. Pumice has very porous
flexural strength at this temperature became 32 % and 20 %, structure . The density is 0.5-1.0 g/cm3. Due to its toughness
[7]
respectively.
and durability, pumice has been used for lightweight, thermal
The major concern with the UHPCC/ HPCC is that, it uses and sound insulating, fire resistance construction materials such
approximately two times the quantity of cement that is as concrete blocks and concrete. Steel slag is obtained as a
used to manufacture normal CC . Therefore, sustainable by-product of steel manufacturing. Steel slag is produced under
[8]
approaches shall be given to reduce the environmental effect a high temperature of 1650°C, so that organic, semi-volatile and
of UHPCC/ HPCC, owing to the fact that cement manufacturing volatile compounds are removed. Approximately 150 to 200 kg
[9]
caused a huge anthropogenic emission . There are several of steel slag is generated per every ton of steel production [13] .
studies that have incorporated waste materials such as FA, Here steel slag was used as fine aggregate. All the chemical
SF and slag materials to reduce the environmental impact composition of ingredients are listed in Table 1. No coarse

Table 1: Chemical compositions of cement, fly ash, silica fume, pumice, steel slag in %
MATERIALS SiO 2 Al 2 O 3 Fe 2 O 3 CaO MgO SO 3 Na 2 O K 2 O LOI
Cement 20.27 5.32 3.56 60.41 2.46 3.17 - - 3.55
Fly ash 54.90 25.60 14.40 8.70 0.98 0.78 0.98 0.98 3.50
Silica fume 86.75 0.92 0.84 0.98 4.29 0.36 1.40 1.12 2.40
Pumice 75.51 1.10 9.94 0.25 0.04 - 2.04 5.12 4.27
Steel slag 17.03 5.64 22.69 43.38 5.98 - - - 1.56

38 THE INDIAN CONCRETE JOURNAL | MARCH 2022