Sampling from a mixer/truck agitator- Where is sample taken? - Answers Between 10% and 90%
(Not when testing with Super P)
How is a sample taken when sampling plastic concrete? - Answers Either pass a receptacle
completely through a discharge stream OR divert a discharge stream completely into a
sampling container.
How many grab samples are needed when testing for uniformity of samples? - Answers 3
What size sample is needed when casting 3 100mm x 200mm cylinders? - Answers Minimum
20L
What size sample is needed when casting 150mm x 300mm cylinders? - Answers Minimum 30L
What size sample is needed when casting 150mm x 150mm x 535mm beams? - Answers
Minimum 55L
How much extra sample is needed when more than 3 cylinders/specimens are to be cast? -
Answers Volume of the cylinders/specimens plus 10% extra
How much time is allowed for obtaining, transporting and remixing the sample? - Answers 10
minutes
A sample contains aggregate larger than that appropriate for the size of the moulds or
equipment. - Answers It must be wet-sieved prior to testing
Information required on reports - Answers Conc mix no, Sample source, Batch time/date,
Sample time/date, Project site, Sample location if different, Location of conc in structure,
Technician name, Lab name/address, Signature of test report reviewer, Any deviation from test
procedures
Air Content - Answers The volume of air voids of plastic concrete, exclusive of pore space in
aggregate particles, determined through observations of the change of air volume in concrete
with a change in pressure.
Slump - Answers A measure of consistency of freshly mixed hydraulic cement concrete, equal
to the subsidence, measured to the next 5mm, of the moulded substance immediately after the
removal of the slump cone
Slump Flow - Answers The horizontal spread of concrete immediately upon removal of the
slump cone as a measure of the unconfined fluidity of concrete giving a relative degree of
indication of the degree to which concrete can travel
How many water-to-cementing materials ratios are needed for concrete trial mixes? - Answers 3
, What temperature is considered stable before mixing concrete? - Answers 23 C +/- 2 C
Where should cementing materials be stored? - Answers In a dry place, in moisture-proof
containers
What sieve must cementing materials be passed through before use to reject lumps? - Answers
1.25mm or finer
Surface moisture in fine and coarse aggregate should be obtained using samples of what size? -
Answers 500g-1000g
How much time is spent mixing concrete? - Answers Mix 3 minutes, rest 3 minutes, mix 2
minutes
Which sample can be re-used for casting cylinders? - Answers Slump or slump flow, NOT air.
Must be remixed into batch first
Cylinder moulds - Answers Must have nonabsorbent surfaces and be sufficiently rigid- Must be
coated with mineral oil
Cardboard moulds cannot be used for what strength? - Answers Greater than 35MPa
Flexural moulds - Answers Must be rectangular and 50mm longer than the prescribed span.
Must be watertight and rigid, nonabsorbent. Variation from specified cross-section is not to
exceed 3mm. Coat with mineral oil.
Tamping Rod for 100mm x 200mm cylinders - Answers Diameter 10mm +/- 1mm and a Length
of 450mm to 600mm. One end must be hemispherical.
Tamping Rod for cylinders 150mm or greater, and rectangular moulds - Answers Diameter
16mm +/- 1mm and a Length 450mm to 600mm. One end must be hemispherical.
Internal Vibrators - Answers Rigi, flexible shaft; powered by electric motor. Frequency 120Hz or
greater. Outside diameter 20mm to 40mm. Minimum height 50mm less than specimen being
consolidated.
Ratio for vibrating cylinders - Answers 4.0 or higher
Vibrating beams - Answers The diameter of the element or thickness of a square vibrating
element shall not exceed 1/3 the width of the mould.
External vibrators - Answers Table/plank type. Minimum 60Hz. Clamp mould securely to
apparatus.
Head mallet weight - Answers 0.6 kg +/- 0.3 kg.
Strike-off Bar - Answers Steel. 6mm x 25mm x 450mm.