Page 11 - Open-Access-Oct-2019

TECHNICAL PAPER

Table 2: Sieve analysis results of fine aggregate

siEvE sizE 10mm 4.75mm 2.36mm 1.18mm 600µ 300µ 150µ
Cumulative percentage passing 100 98 96.2 75.3 53.6 14.8 2.9
Remarks Zone II (As per IS-383:2016)

2.5 Preparation of Mortar Mixture and testing temperature. Prior to conduct of compressive test, specimens
were stored in laboratory condition for 20 hours .
[16]
Mortar mixtures were prepared by using binder to natural fine
aggregate ratio of 1:3. Water to binder ratio of 0.4 is adopted.
Three major mortar mixture proportions were adopted in the 2.7 Microstructure and Mineralogical studies
present study. Three mortar mixtures composed of 0%, 10% FCA Microstructure studies were carried out using Scanning Electron
and 7% lime, and 20% FCA and 7% lime as a replacement to Microscope (SEM by JEOL Model JSM 6380 LA) in secondary
OPC. Table 3 presents the different mixtures used in the present electron mode. Phase identification of raw and hydrated
study. samples was carried out by X-ray Diffraction analysis (XRD) with
Cu K radiation of make, JEOL JDX 8P.
table 3: Mixture composition of FCA based mortars
3. ResULts AND DIsCUssION
sl nO Mix iD Mix cOMPOsitiOn
3.1 Consistency of Mortar Mixtures
1 M1 100% OPC + 0% FCA + 0% Lime
The consistency of fresh mortar mixtures was determined by
2 M2 83% OPC + 10% FCA + 7% Lime flow-table method as per . As FCA replacement increases from
[17]
0% to 20%, the spread value is found to vary from 101 mm to
3 M3 73% OPC + 20% FCA + 7% Lime
108 mm. This change in spread value can be attributed to
spherical shape [18] of FCA [Figure 1(a)]. Water to binder ratio of
Mortar cubes were cast using standard moulds as per of size 0.4 is sufficient to make consistent homogeneous mixture and
[12]
70.6 mm to measure compressive strength of FCA-based mortar also satisfies the requirement [17] of 105±5 mm spread.
mixtures. Cast mortar cubes were allowed to set for one day
under room temperature of 24 ± 5ºC with relative humidity of 3.2 Compressive strength of Mortar Mixture
90 ± 5%. The samples were demoulded after 24 hours and then
cured for 28, 56 and 84 days in water. After 28, 56 and 84 days Table 4 and Figure 2 present the observed values of compressive
of water curing, the samples were dried for one hour and then strengths, for OPC and FCA based mortar specimen at the age
crushed to failure to determine the compressive strength of the of 28, 56, and 84 days. From the compressive strength values, it
mortar specimen as per . Compressive strength is reported as is observed that, as expected like other SCM, FCA did not show
[13]
the average of three mortar specimen results. any strength development by secondary hydration. This may be
due to insufficient reactive silica from FCA to react with calcium
hydroxide to form C-S-H in secondary hydration process. This
2.6 elevated temperature studies
effect is usually known as “dilution effect” . Nevertheless,
[19]
After 84 days of water curing, test specimen were dried at room FCA-based mortar mixtures showed comparable compressive
temperature for 1 hour and weighed to obtain dry mass of strength as that of OPC based control mortar mixture.
samples. Afterwards, the specimens were subjected to elevated
temperatures in a programmable electrical furnace. The samples table 4: Compressive strengths of FCA-based
were set to maintain little gap from bottom of furnace chamber, mortar mixtures at different curing temperatures
and were relatively at a large distance from heating coils to
enable uniform dispersion of heat to specimen and also avoid Mix iD cOMPrEssivE strEngth (MPa)
damage to the furnace coils in case of severe spalling [1, 14-15] . 28 DAys 54 DAys 84 DAys
Specimen were heated at the rate of 5ºC/min to reach desired
temperature level. After reaching the desired test temperature, M1 47.75 47.75 48.42
specimens were held for a retention period of half an hour to M2 49.43 50.11 48.09
avoid any thermal shock on specimen, and then power supply
to furnace was turned off and specimens were cooled to room M3 44.39 45.73 45.73

16 The IndIan ConCreTe Journal | oCToBer 2019