CCIL Concrete Study Guide with Complete Solutions Latest Updated 2024 Procedure for sampling plastic concrete includes - Correct Answer Every precaution that will assist in obtaining samples that are truly representative of the nature and conditions of the concrete When sampling from a truck agitator or truck mixer, - Correct Answer The sample shall be taken between the 10% and 90% points of the discharge Grab Sampling - Correct Answer The operation of securing at one point of the discharge the required volume of representative material in as short a period of time as possible.Sampling for uniformity of mixed concrete includes: - Correct Answer Obtaining three grab samples of concrete for comparative purposes while the mixer is being emptied and keep the samples separate to represent the designated portions in the batch rather than combined to form a composite sample.When 100 mm x 200 mm cylinders are to be cast: - Correct Answer A minimum 20 L sample shall be obtained.When 150 mm x 300 mm cylinders are to be cast: - Correct Answer A minimum 30 L sample shall be obtained.When 150 mm x 150 mm x 535 mm cylinders are to be cast: - Correct Answer A minimum 55 L sample shall be obtained.For more than three cylinders or beams, the minimum volume shall be increased - Correct Answer By a value equal to the volume of the extra specimens, plus 10%.Sampling shall by performed - Correct Answer By passing a receptacle completely through the discharge stream or by completely diverting the discharge into a sample container.The sample shall be obtained, transported, and remixed - Correct Answer Within 10 minutes. 1 / 2
The sample shall be protected - Correct Answer From sun, wind, and other sources of rapid evaporation and from contamination.When the concrete contains aggregate larger than that appropriate for the size of the moulds or equipment to be used, - Correct Answer the sample shall be wet sieved prior to testing. For all density tests, an unsieved sample shall be used.Do not use cardboard moulds: - Correct Answer When the specified concrete strength is greater than 35 MPa.Rectangular moulds: - Correct Answer Should be at least 50 mm longer than the length of the span.Moulds shall be watertight and made of rigid, nonabsorbent material.Tamping rod for 100 x 200 mm cylinders - Correct Answer Straight steel 10 +- 1 mm in diameter and between 450 and 600 mm in length, having at least one end rounded to a hemispherical tip.Tamping rod for cylinders 150 mm in diameter or greater - Correct Answer Straight steel 16 +- 1 mm in diameter and between 450 and 600 mm in length, having at least one end rounded to a hemispherical tip.The frequency of vibration of an internal vibrator shall be a minimum of - Correct Answer 120 Hz The outside diameter of the internal vibrator shall be - Correct Answer 20 to 40 mm The minimum length of the internal vibrator shall be - Correct Answer 50 mm less than the height of the mould being consolidated For vibration of cylinders, the ratio of the diameter of the cylinder to the diameter of the vibrating element shall be - Correct Answer 4.0 or higher For vibration of beams, the diameter of the vibrating element or thickness of a square vibrating element shall not exceed - Correct Answer One third of the width of the mould
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