2.2. Tests Performed on Hardened Concrete Specimens
Compression Test
The compression test was performed to find out compressive strength of polymer modified steel fiber reinforced
concrete on test specimens cubical in shape of size 150 mm × 150 mm × 150 mm, confirming to IS:
10086-1982. Compression testing machine of capacity 3000 kN was used. The schematic test setup is shown in
Figure 2 and compression test of concrete cube in progress is shown in Figure 3.
The compressive strength of the specimen is calculated by dividing the maximum load applied to the specimen
during the test by the cross sectional area, i.e. by using the formula
c
cu
P f A = (1)
where fcu = Compressive strength of concrete in MPa;
Pc = Maximum applied load in kN;
A = Cross sectional area in mm2
.
Flexure Test
To find out flexural strength of concrete, prism specimens of size 150 mm × 150 mm × 700 mm were used.
The arrangement for loading of flexure test specimen is shown in Figure 4. The prism specimen shall be placed
in the machine in such a manner that the load shall be applied to the uppermost surface as cast in the mould,
along two lines spaced 200 mm apart i.e. two point load. The axis of the specimen shall be carefully aligned
with the axis of the loading device. The load was applied without shock and increased continuously at the rate of
400 kg/min. The appearance of the fractured faces of concrete and any unusual features in the type of failure
was noted. Flexure test on concrete beam under progress is shown in Figure 5.
The flexural strength of the specimen (fb) is calculated by using following expression:
b 2
Pa f bd = (2)
where P = maximum applied load to the specimen in kN;
a = span of the beam in mm;
b = width of the beam specimen in mm;
d = depth of the beam specimen in mm.
Pullout Test (Bond Strength Test)
Pullout test was performed to find out bond strength of concrete. The specimens were cast according to
ASTM standard C234-91a. Concrete cube of size 150 mm × 150 mm × 150 mm with a 16 mm diameter tor steel
bar embedded 150 mm in concrete cube as shown in Figure 6 was used as test specimen. The verticality of 16
mm embedded tor steel rod was ensured by supporting it till the concrete hardens.
The pullout test was carried out at 28 days using Universal Testing Machine (UTM). The specimen was held
between upper and middle cross-head. The rod was gripped in upper cross-head and cube was held below middle
cross-head as shown in Figure 7.
The tensile load was applied on steel bar for pullout purpose. The loads and slips were recorded at every 400
Kg interval till failure of specimen. The maximum pull-out force is recorded in the test at bond failure. The deformations
(slips) were recorded with sensitive dial gauge of least count 0.01 mm. The maximum pull force, P
and corresponding slip, Δ were used to calculate the pull-out work done (P × Δ) from this test. The bond
strength is calculated by using the equation
π bd
P
dl
τ = (3)
where τbd = bond strength of concrete in MPa;
P = pull-out force in kN;
d = diameter of steel bar embedded in concrete cube in mm;
l = length of the bar embedded in concrete in mm.