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96 Cards in this Set
- Front
- Back
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Concrete temperature is one the most important factors influencing the _______, ____ __ ___, and ________ __ ___ ________.
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quality, time of set, strength of the concrete.
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A concrete with a high initial temperature will probably have _____ ____ ______ _____ ________ and _____ ____ ______ _____ ________.
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higher than normal early strength, lower than normal later strength.
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Concrete placed and cured at low temperatures will develop strength at a ______ ____ ___ __________ ____ ____ ______ ________ and __ __ _ ______ _______.
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slower rate but ultimately will have higher strength, be of a higher quality.
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Concrete temperature affects the performance of?
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Chemical admixtures, air entraining admixtures, pozzolanic materials and other additives and admixtures.
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Concrete containing aggregate of a nominal maximum size greater than ___ may require up to 20 min for the transfer of heat from aggregate to mortar.
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3 in (75 mm)
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Container shall be large enough to provide at least ___ of concrete in all direction around the sensor of the temperature measuring device; concrete cover must also be at least _____ times the nominal maximum size of the coarse aggregate.
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3 in (75 mm), three.
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Temperature measuring device shall be capable of accurately measuring the temperature of the freshly mixed concrete to __________ throughout range of ___ to ________.
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+/- 1 degree F (+/- 0.5 degrees C), 30 degrees, 120 degrees F (0 to 50 degrees C)
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Reference Temperature Measuring Device shall be readable and accurate to ________.
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+/- 0.5 degrees F (0.2 degrees C)
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Each temperature measuring device used for determining temperature of freshly mixed concrete shall be calibrated ________, or whenever there is a question of ________.
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annually, accuracy.
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Calibration shall be performed by comparing the readings of temperature measuring device at ___ temperatures at least ___________ apart.
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two, 30 degrees F (15 degrees C).
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It is acceptable to measure the temperature of freshly mixed concrete in either the transporting equipment or the forms after discharge provided the sensor of the temperature measuring device that has __ _____ _______ of concrete cover in all directions.
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at least 3 in (75 mm)
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What do you do to the sampling container prior to placing freshly mixed concrete in it?
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Dampen with water.
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Standard Test Method for Temperature of Freshly Mixed Hydraulic-Cement Concrete is which section and ASTM?
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Section 1 and ASTM C1064
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Position the temperature measuring device so that the end of the temperature sensing portion is submerged a minimum of _________ into the freshly mixed concrete.
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3 in (75 mm)
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What do you do to prevent the ambient air temperature from affecting the reading of the temperature measuring device at the surface of the concrete?
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Close the void left by the placement by gently pressing the concrete around the temperature measuring device.
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Leave the temperature measuring device in the freshly mixed concrete for at least _ ___ but not more than _ ___.
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2 min, 5 min.
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Read and record the temperature to the nearest _________.
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1 degreee F (0.5 degrees C)
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Remove or keep the temperature measuring device in the concrete when reading the temperature.
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Keep
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Standard Practice for Sampling Freshly Mixed Concrete section and ASTM?
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Section 2 and ASTM C172.
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What is the minimum amount of the sample of concrete needed?
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1 cubic yard (28 liter)
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The elapsed time shall not exceed __ ____ between obtaining the first and final portions of the composite sample.
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15 min.
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Start tests for slump, temperature, and air content within _ ___ after obtaining the final portion of the composite sample.
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5 min
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Start molding specimens for strength tests within __ ___ after fabricating the composite sample.
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15 min.
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Expeditiously obtain and use the sample and protect the sample from the what?
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sun, wind, and other sources of rapid evaporation, and from contamination.
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Sampling from stationary mixers, sample the concrete by collecting ___ or more portions taken at regularly spaced interval during discharge of the ______ portion of the batch.
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two, middle.
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Do not obtain portions of the composite sample from the very _____ or ____ part of the batch discharge.
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first, last.
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No samples should be taken before ___ or after ___ of the batch has been discharged.
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10%, 90%.
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Sampling from Paving Mixers, obtain samples from at least ____ different portions of the pile and then composite into ___ sample for test purposes.
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five, one.
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Sampling from Revolving Drum Truck Mixers or Agitators, sample concrete by collecting ___ or more portions taken at regularly spaced intervals during discharge of the ______ portion of the batch.
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two, middle.
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In any case do or don't take samples before the water and any admixtures have been added to the mixer.
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Don't.
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Sample by repeatedly passing a receptacle through the entire _________ stream or by completely _________ the discharge into a sample container.
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Discharge, diverting.
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Regulate the rate of discharge of the batch by the ____ __ __________ of the drum and not by the size of the gate opening.
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rate of revolution
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The process of removing aggregate larger than a designated size from the fresh concrete by sieving it on a sieve of the designated size is called what?
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wet-sieving.
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Hand tools used in sampling concrete.
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Shovels, hand scoops, plastering trowels, and rubber gloves as required.
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Mortar adhering to the aggregate retained on the sieve should or shouldn't be wiped from it before it is discarded.
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Shouldn't
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Standard Test Method for Slump of Hydraulic-Cement Concrete section and ASTM?
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Section 3 and ASTM C143.
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The purpose of the slump test is to determine the ___________ of the concrete.
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consistency
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Slump does or does not measures the water content or workability of the concrete.
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Does not.
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Is it true that an increase or decrease in the water content will cause a corresponding increase or decrease in the slump of the concrete, provided that all of the other materials and conditions are constant. True or False?
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True.
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A sample of freshly mixed concrete is placed and compacted by _______ in a mold shaped as the frustum of the cone.
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Rodding
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This slump test method is considered applicable to plastic concrete having coarse aggregate up to _____ in size.
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1 1/2 in. (37.5 mm)
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Mold-what are the dimensions for the slump cone?
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4 in +/- 1/8" x 8 in +/- 1/8" x 12 in +/- 1/8".
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Slump Cone Mold-the test specimen shall be formed in a mold made of _____ not readily attacked by cement paste.
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metal
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Molds other than metal are allowed if the following requirements are met:
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The mold shall meet the shape, height, and internal dimensional requirements.
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Tamping Rod- A round, straight steel rod, with a _______________ diameter. The length of the tamping rod shall be at least ________ greater than the depth of the mold in which rodding is being performed, but not greater than _________ in overall length.
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5/8 in. (16 mm) +/- 1/16 in (2 mm), 4 in (100 mm), 24 in (600 mm)
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A rod length of ____________ to ___________ meets the requirements of a tamping rod.
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16 in (400 mm), 24 in (600 mm)
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One third of the volume of the slump mold fills it to a depth of _____?
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2 5/8 in (70 mm)
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Two thirds of the volume fills it to a depth of _______?
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6 1/8 in (160 mm)
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Slump mold-Rod each layer __ times uniformly over the cross section with the rounded end of the rod. Half of the strokes should be near the perimeter.
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25
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Slump test rodding- for each upper layer, allow the rod to penetrate through the layer being rodded and into the layer below approximately ______.
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1 in ( 25 mm)
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Slump test- Raise the mold a distance of 12 in (300 mm) in _________ by a steady upward lift with no lateral or torsional motion.
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5 +/- 2 s.
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Slump test- complete the entire test from the start of the filling through removal of the mold without interruption and complete it with an elapsed time of _______.
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2 1/2 min.
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Immediately measure the slump by determining the vertical difference between the top of the mold and the displaced original ______ of the top surface of the specimen.
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center
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If ___ consecutive tests on a sample of concrete show a falling away or shearing off of a portion of the concrete from the mass of the specimen, the concrete probably lacks necessary plasticity and cohesive for the slump test to be applicable.
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Two
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Report the slump in term of inches (millimeters) to the nearest ______ of subsidence of the specimen during the test.
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1/4 in. (5 mm)
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Slump test- for the _____ layer, heap concrete above the top of the mold.
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third
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Standard Practice for Making and Curing Concrete Test Specimens in the Field section and ASTM?
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Section 7 and ASTM C31.
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Most concrete is or isn't bought and sold on the basis of strength test results.
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Is
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Concrete strength test specimens must be made according to Method C31 for two reasons:
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1. so that the results are reliable, and 2. so that the test can be reproduced by someone else that the same concrete, following the same procedure and getting (nearly) the same results.
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General molds- for specimens or fastenings thereto in contact with the concrete shall be made of _____, ____ ____ or other nonabsorbent material, nonreactive with concrete containing Portland or other hydraulic cements.
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steel, cast iron.
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Vibrators- the vibrator frequency shall be at least ____ vibrations per minute (150 Hz) while the vibrator is operating in the concrete.
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9000
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Vibrator- the diameter of the a round vibrator shall be no more than __________ the diameter of the cylinder mold or __________ the width of the beam mold.
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one-fourth, one-fourth.
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Mallet- a mallet with a rubber or rawhide head weighing __________ shall be used.
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1.25 +/- 0.50 lb (0.6 +/- 0.2 kg)
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Placement tools- should be of a size _____ enough so each amount of concrete obtained from the sampling receptacle is representative and _____ enough so concrete is not spilled during placement in the mold.
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Large, small
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Type of sampling receptacles?
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Heavy gauge metal pan, wheelbarrow, or flat, clean nonabsorbent board of sufficient capacity to allow easy remixing of the entire sample with a shovel or trowel.
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What are the sizes of the cylinders for specified compressive strength?
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6" x 12" (150 x 300 mm) or 4" x 8" (100 x 200 mm)
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Cylindrical Specimens- compressive or splitting tensile strength specimens shall be _________ ____ and allowed to set in an _______ ________.
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cylinders cast, upright position.
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Cylindrical Specimens- the length shall be _____ the diameter and the cylinder diameter shall be at least _ times the nominal maximum size of the coarse aggregate.
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twice, 3
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When the nominal maximum size of the coarse aggregate exceeds _______, the concrete sample shall be treated by ___ _______ through a ________ sieve.
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2 in. (50 mm), wet sieving, 2-in (50-mm)
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Beam Specimens- Flexural strength specimens shall be beams of ________ ____ and hardened in the ___________ position.
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concrete cast, horizontal.
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Beam Specimens- The length shall be at least _______ greater than _____ times the depth as tested.
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2 in (50 mm), three.
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Beam Specimens- the ratio of width to depth as molded shall not exceed ___.
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1.5
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Beam Specimens- the standard beam shall be _______ in cross section, and shall be used for concrete with nominal maximum size coarse aggregate up to _______.
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6" x 6" (150 x 150 mm), 2 in (50 mm)
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Place of Molding- mold specimens promptly on a _____, _____ _______, ____ __ _________ and other disturbances at a place near as practicable to the location where they are to be stored.
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level, rigid surface, free of vibration.
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What are the methods of consolidation?
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Practice of rodding or internal vribration.
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Cylinder molds: number of layers for rodding depend on the diameter, 4 in = _, 6 in = _, and 9 in = _.
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2, 3, and 4.
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Cylinder molds: number of roddings depend of diameter, 4 in = __, 6 in = __, and 9 in = __.
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25, 25, and 50.
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Cylinder molds: number of layers for vibrating are all of the same diameter for 4 in, 6 in, 9 in which is what?
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2
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Cylinder molds: number of vibrator insertions per layer? 4 in = _, 6 in = _, and 9 in = _.
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1, 2, 4.
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Beam molds: number of layers depend of width of beam, 6 to 8 in = _ and greater than 8 in = _ __ ____ _____ ______, ____ ___ __ ______ ____.
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2, 3 or more equal depths, each not to exceed 6 in.
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Tap the outsides of the mold lightly __ to __ times with the mallet to close any holes left by rodding and to release any large air bubbles that may have been trapped.
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10, 15.
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No more than ___ of vibration should be required for each insertion to adequately consolidate concrete with a slump greater than ____. Longer times may be required for lower slump concrete, but the vibration time should rarely have to exceed ___ per insertion.
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5s, 3 in (75 mm), 10s
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Cylinder molds- after each layer is vibrated, tap the outsides of the mold at least __ times with the mallet, to close holes that remain and to release entrapped air voids.
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10
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Beam molds- Insert the vibrator at intervals not exceeding ______ along the center line of the long dimension of the specimen.
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6 in (150 mm)
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Beam molds- for specimens wider than ____, use alternating insertions along two lines.
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6 in (150 mm)
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Beam molds- allow shaft of the vibrator to penetrate into the bottom layer about ____.
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1 in (25 mm)
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Beam molds- after each layer is vibrated, tap the outsides of the mold sharply at least __ times with the mallet to close holes left by vibrating and to release entrapped air voids.
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10
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Cylinder mold- use a _______ ___ or ________ _____ or ______ to strike off the top of the mold
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tamping rod, handheld float, trowel.
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Beam mold- use a ________ _____ or ______ to strike off the top off the surface produce a flat, even surface.
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handheld float, trowel.
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Identification of molds: ____ the specimens to positively identify them and the concrete they represent.
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Mark
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Initial curing of molds: Immediately after molding and finishing, the specimens shall be store for a period up to __ ______ in a temperature range from __ and __________ and in an environment preventing moisture loss from the specimens.
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48 hours, 60, 80 degrees F (16 and 27 degrees C)
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Curing of molds 6000 PSI or greater, the initial curing temperature shall be between __ and _________.
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68, 78 degrees F (20 and 26 degrees C)
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Final curing of cylinder molds: within __ min after removing the molds, cure specimens with free water maintained on their surfaces at all times at a temperature of ________________ using water storage tanks or moist rooms.
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30, 73.5 +/- 3.5 degrees F ( 23.0 +/- 2.0 degrees C)
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Final curing of beam molds: beams are to be cured the same as cylinders except that they shall be stored in water saturated with _______ _________ at 73.5 +/- degrees F (23.0 +/- 2.0 degrees C) at least 20 h prior to testing.
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calcium hydroxide
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Field curing of cylinder molds: _____ cylinders in or on the structure as near to the point of deposit of the concrete represented as possible.
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Store
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Molds: Immediately after finish, provide __________ to prevent sample moisture loss and move the specimens to an initial curing place for storage.
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Protection
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