Compressive Strength of Concrete Cores
[BS 1881 – Part 120: 1983]
·
Specimens: 100 or 150 mm Dia, (Dia/Agg. Size ≥ 3),
(Length/Diameter [λ] = 1 – 2).
·
Identification: Check Location, Orientation, Direction of
Drilling relative to Direction of Casting and Min/Max Length as received.
·
Examination: Check the Excess Voids (%) by Comparing the
Core Surface with Figure 1:
o
Small
Void (0.5 – 3.0) mm.
o
Medium
Void (3.0 – 6.0) mm.
o
Large
Void (>6.0) mm.
o
Honeycombing
(Interconnected Voids).
·
Density (As Received, Moist, Saturated): to nearest 10 Kg/m3
·
Reinforcement: Measure the Size, Spacing of bars and
Position in core (Center of bar to top of Core) as received and after
preparation.
·
Tolerances: Flatness: 0.06 mm, Squarness: 2.0 mm wide, Parallelism:
2.0 mm wide & Cylindricity: 3 % of core diameter
·
End Preparation:
1.
By
grinding: Store in Water (20 ± 2) °C, take out for 1h for grinding and
measurement.
2.
By
capping (<10mm Thickness):
a)
Store
in Water (20 ± 2) °C, take out for 1h for Capping and measurement.
b)
Store
in dry condition; take out for 1h for Capping and measurement.
·
Testing: Not less than 2 days after preparation and
immersing in water
·
Loading: Pace Rate (0.2 -0.4)N/(mm2.s)
·
Compressive
Strength: to nearest
0.5 N/mm2 (Load/Area)
·
Estimated
In-Situ Cube Strength:
1.
Free
of reinforcement: I.S.C.S = 
x C.S (D = 2.5 horizontally
drilled, 2.3 Vertically)
x C.S (D = 2.5 horizontally
drilled, 2.3 Vertically)
2.
Presence of
reinforcement (Single Bar): Correction Factor = 1.0 + 1.5 (ør*d/øc*l)
3.
Presence of
reinforcement (Two Bars): Correction Factor = 1.0 + 1.5 (Ʃør*d/fc*l)
ør is diameter of
Reinforcement
øc is diameter of Specimen
d is distance of bar from nearer end
l is length
