Compressive Strength of Concrete Cores

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).

·         Dimension: to nearest 1mm (measure length and diameter before and after preparation)

·         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)

2.       Presence of reinforcement (Single Bar): Correction Factor = 1.0 + 1.5 (ø_r*d/ø_c*l)

3.       Presence of reinforcement (Two Bars): Correction Factor = 1.0 + 1.5 (Ʃø_r*d/f_c*l)

ø_r is diameter of Reinforcement

ø_c is diameter of Specimen

d is distance of bar from nearer end

l is length