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2025(updated) ACI Concrete Field Testing Technician-
Grade I exam questions and answers
The sensor of the temperature measuring device shall be submerged a minimum of in. [ mm] into the freshly mixed concrete. - answer 3 in. [75 mm] The temperature measuring device shall have a capacity of measuring temperature of freshly mixed concrete to +- degrees F [+- C] throughout a range of. - answer 1 degree F [0.5 C], 30 degrees F to 120 F [0 C to 50 C] The temperature measuring device shall be calibrated , or whenever there is a question of. - answer Annually, accuracy The temperature of concrete may be measured in a wheelbarrow. True or False? - answer True The temperature of concrete may be measured in a wall form. True of False - answer True A composite sample of concrete is required even if the only purpose for obtaining the sample is to determine temperature. True of False? - answer False What must be done to the sample container prior to sampling the concrete? - answer Dampen (with water)
What must be done to the concrete surrounding the temperature measuring device after the device is submerged in the fresh concrete. - answer Gently press the concrete around the temperature measuring device at the surface of the concrete How long must the temperature measuring device remain in the freshly mixed concrete? - answer At least 2 minutes but not more than 5 minutes After the temperature of the concrete is read, what is required? - answer Reporting of temperature The temperature of concrete is reported to the nearest degrees F [ C] - answer 1 degree F [0.5 C] According to ASTM C1064, what is one reason to take the temperature of concrete? - answer Verify conformance to a specified requirement for temperature of concrete A maximum temperature of freshly mixed concrete is specified in ASTM C1064. True of False?
- answer False The sample of concrete used for temperature determination must be rodded 25 times. True or False? - answer False Sampling by this method is required when tests are to be made to determine with specification requirements. - answer Compliance This method covers sampling from four types of mixtures which are , , , and . - answer Stationary mixers, paving mixers, revolving drum mixers, and open top mixers
Concrete samples from a truck mixer must be obtained before any water or admixtures are added to the mixer at the job site. True or False? - answer False The composite samples from a truck mixer must be obtained from the portion of the batch. - answer Middle When the concrete contains aggregate larger than that permitted for a particular test method, the sample of concrete must be before making the test. - answer Wet sieved The slump test is applicable to plastic concrete with a maximum size aggregate of. - answer 1.5 in. [37.5 mm] When the concrete contains aggregate larger than allowed for the slump test, the large aggregate must be. - answer Removed by wet sieving the sample over 1.5 in. [37. mm] sieve The mold for making the slump test is in the shape of. - answer The frustum of a cone The height of the slump mold is. - answer 12 in. [300 mm] The interior surface of the slump mold is allowed to have minor irregularities. True or False? - answer False For use in the slump test, the end or both ends of the tamping rod must be. - answer Rounded to a hemispherical tip
The sample of concrete for use in making the slump test must be obained in accordance with ASTM Standard. - answer C172, Standard Practice for Sampling Freshly Mixed Concrete The slump mold should be in a dry condition before beginning the test. True or False? - answer False The surface on which the slump mold will be placed must be. - answer Flat, level, moist, nonabsorbent, and free of vibration The slump mold is filled in layers. - answer 3 Each layer should fill approximately the volume of the mold. - answer One-third The approximate concrete depth (in verticle distance) after placing the first layer is , and the second layer is. - answer 2 5/8 in. [70 mm], 6 1/8 in. [160 mm] What is the specified number of roddings for each layer? - answer 25 How deep should the tamping rod penetrate into each layer? - answer Rod each layer throughout its depth; on the second and final layers, the rod should penetrate into the previous layer approximately 1 in. [25 mm] When rodding the bottom layer, the tamping rod must be to uniformly distribute the strokes. - answer Slightly inclined
What is the required shape of the tamping end of the rod? - answer Rounded to a hemispherical tip What is the required minimum frequency of the vibrator used in this test method? - answer 7000 vibrations per minute The outside diameter or side dimension of the vibrating element must be at least but not greater than. - answer 0.75 in. [19 mm], 1.50 in. [38 mm] A plastic container can be used for the measure in this method. True or False? - answer False, measure must be steel or another suitable metal What is the minimum thickness of a metal strike-off plate? - answer 1/4 in. [6 mm] What is the minimum thickness for a glass or acrylic strike-off plate? - answer 1/2 in. [12 mm] What is the specified weight of the mallet used on measures that are 0.5 ft^3 [14 L] or smaller? - answer 1.25 +- 0.50 lb. [600 +- 200 g] Measures other than air meter bowls used for this test must conform to ASTM. - answer C Air meter bowls used for this test must conform to ASTM and be calibrated for volumee according to ASTM. - answer C231, C The concrete sample must be obtained in accodance with what ASTM method? - answer C
What method of consolidation must be used when the slump is greater than 3 in. [75 mm]? - answer Rodding What method of consolidation must be used when the slump is less than 1 in. (25 mm]? - answer Vibration If rodding is the method of consolidation being used, the measure must be filled in how many layers? - answer 3 For a measure of 0.5 ft^3 [14 L], what is the required number of strokes of the tamping rod for consolidation of each layer? - answer 25 When rodding the middle and the top layers, the tamping rod should penetrate into the layer below approximately. - answer 1 in. [25 mm] If vibration is the method of consolidation, the measure must be filled in approximately equal layers. - answer 2 If, after consolidation of the final layer, the concrete level is 1/2 in. (13 mm) above the top of the measure, what should be done? - answer Remove a representative portion of the excess concrete with a trowel or scoop After consolidation of the final layer, an excess of concrete above the top of the measure is considered optimum. - answer 1/8 in. [3 mm] After completing the strike-off procedure, what must be done before weighing the measure and sample? - answer Clean off any excess concrete
If the concrete sample is to be consolidated by vibration, the measure is filled in layers.
- answer 2 equal When rodding the concrete sample, what is the specified number of strokes required for each layer? - answer 25 Vibration of the concrete sample is not allowed when the slump of concrete exceeds. - answer 75 mm (3 in.) In rodding the sample, how deep should the rod penetrate each layer? - answer Rod bottom layer to full depth; rod second and final layer penetrating the previous layer about 25 mm ( in.) After rodding each layer, what should be done to the measure before adding another layer of concrete? - answer Tap the sides of the measure smartly 10 to 15 times with the mallet When consolidating the concrete by vibration, how many times should the vibrator be inserted into each layer? - answer Three (3) What tools may be used to strike off the top surface of the concrete following consolidation of the final layer? - answer A strike-off bar; a metal, glass, or acrylic plate What must be done if there is a slight deficiency in the quantity of concrete in the measure of consolidation of final layer? - answer Add a quantity of representative concrete before strike off
What must be done if there is an excessive amount of concrete in measure following consolidation of the final layer? - answer Remove a representative quantity of concrete with the scoop or trowel before the strike off The volumetric method of determining air content of concrete can be used on concrete containing what types of aggregate? - answer All types of aggregate What are the requirements for the tamping rod used in the test method? - answer Round, straight 5/8 [16 mm] +- 1/16 in. [2 mm] diameter rod at least 5 in. [300 mm] greater in length than the depth of the bowl being used, with the tamping end rounded to a hemispherical tip of the same diameter, made of steel, high-density polyethylene, or other plastic of equal or greater abrasion resistance. What are the requirements for the strike-off bar used in this test method? - answer Flat, straight steel bar at least 1/8 by 3/4 by 12 in. [3 by 20 by 300 mm] or a 4.4 flat, straight high- density polyethylene bar, or other plastic of equal or greater abrasion resistance, at least 1/ by 3/4 by 23 in [6 by 30 by 300 mm]. What is the approximate volume of the measuring cup used to add water to the air meter, in relation to teh volume of the air meter bowl? - answer 1.00% +- 0.04% What type of alcohol and concentration must be used in this test method? - answer Isopropyl, 70% by volume (65% by weight) A mallet weighing must be used to tap the sides of the bowl after rodding each layer. - answer 1.25 +- 0.50 lb. (600 +- 200 g) The sample of concrete used in this test method must be obtained in accordance with what ASTM Standard? - answer C
Why is the isopropyl alcohol added to the meter? - answer To dispel any foam that may be on the surface of the water The direct reading of the final liquid level in the neck of the air meter, is estimated to teh nearest. - answer 0.25% If the air content is greater than the 9% range of the meter,. - answer Calibrated cups of water are added to ring the liquid level within the graduated range In order for an initial meter reading to be valid, the meter must not be leaking, the liquid level must stabilize within 6 minutes, and the foam on the surface of the liquid must not be greater than 2 full percent divisions. True or False? - answer True If less than 2.5 pints of alcohol are used, the air content is always indicated by the inal meter reading. True or False? - answer False, if the air content is more than 9%, the number of calibrated cups of water introduced into the meter to bring the liquid level within the graduated range must be added If more than 2.5 pints of alcohol are used, the final meter reading is always adjusted using
. - answer A correction factor When large amounts of alcohol are used, the direct reading will tend to indicate a air content. - answer Higher At the end of the procedure, the air meter is. - answer Disassembled and its contents examined
If portions of undisturbed concrete are found in the air meter at the end of the test,. - answer The test is invalid ASTM Method gives standardized requirements for , , , and , of test specimens. - answer Making, curing, protecting, transporting For cylinders with a diameter of 6 in. [150 mm] or greater, the tamping rod must be a round, straight steel rod with a diameter of. - answer 5/8 +- 1/16 in [16 mm +- 2 mm] The minimum frequency of an internal vibrator used in this procedure is. - answer 9000 vibrations per minute [150 Hz] The container for obtaining the concrete sample used in this procedure can be a , , or. - answer Metal pan, wheelbarrow, flat, clean nonabsorbent mixing board A 6 by 12 in [150 mm by 300 mm] cylinder mold can be used for concrete containing aggregate with particles not exceeding in size, without the need for wet sieving the concrete. - answer 2 in. [50 mm] The sample of concrete used in molding test specimens must be obtained in accordance with what ASTM Standard? - answer C When strenght specimens are to be made, what three other tests must be made? - answer Slump, air content, temperature After molding test specimens, you should wait two hours before moving them to the location of initial storage. True or False? - answer False; the specimens must be moved immediately
Up to 48 hours after molding, test specimens that are to be standard cured shall be stored in a temperature range between to. - answer 60 and 70 degrees F [16 and 27 C] Upon completion of initial curing, the test specimens may be left in their molds and sealed in plastic bags. True or False? - answer False; specimens are to be demoled and placed in water storage tanks or moist rooms with free water at a temperature of 73.5 +- 3.5 degrees F [23. +- 2.0 C] During transportation, test specimens must be protected from damage due to , , and. - answer Jarring, freezing temperatures, moisture loss Specimens shall not be transported until after final set. - answer 8h Transportation time shall not exceed. - answer 4h Standard Curing is the curing method used when test specimens are to be used for
. - answer Acceptance testing for specified strength, checking the adequacy of mixture proportions for strength, quality control Field Curing is the curing method used when test specimens are to be used for. - answer Determination of whether the structure is capable of being put into service; Comparison with standard cured specimens test results or with results from various in-place test methods; Adequacy of curing and protection of concrete in the Structure, or Form or shoring removal time requirements Cylinders that are to be field cured are stored and protected. - answer In or on the structure as near to the point of deposit of the concrete represented as possible; In as near as possible the same way as the formed work
The temperature and moisture environment for field cured cylinders must be. - answer The same as the structural work Cylinders made for the purpose of determining when a structure may be put into service shall be removed from the mold. - answer At the time of the removal of formwork
