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A comprehensive set of questions and answers for the astm aci concrete strength technician exam. it covers key aspects of concrete testing, including compressive strength, flexural strength, and the use of unbonded caps. The questions and answers are detailed and cover various astm standards, making it a valuable resource for students and professionals in civil engineering and construction.
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ASTM standard dealing with compressive strength of cylindrical concrete specimens ---------CORRECT ANSWER-----------------C ASTM C39 measures the compressive strength of cylindrical concrete specimens that weigh less than 800 kg/m3 (50 lb/ft3). True or false --------- CORRECT ANSWER-----------------False.. weigh more than ASTM C39 consists of applying a compressive axial load to molded cylinders or cores at any rate until failure occurs. True or false? --------- CORRECT ANSWER-----------------False, Specified Rate Results obtained from the compressive strength test method will depend on many things, such as the size and ____ of the specimen, batching, _____ procedures, the age, temperature and _____ conditions during curing. ------ ---CORRECT ANSWER-----------------shape, mixing, moisture ASTM C39 is used to determine ____ _____ of cylindrical specimens. ------ ---CORRECT ANSWER-----------------Compressive Strength The calibration of the testing machines must be verified under 4 conditions: at least ____, upon original installation, or after _____, after making _____ or adjustments, and whenever there is reason to suspect the _____ of the indicated load ---------CORRECT ANSWER-----------------annually, relocation, repairs, accuracy
The machine must be power operated and apply the load intermittently. True or False? ---------CORRECT ANSWER-----------------False Supplemental means of loading for calibration may be power or hand operated. True or False? ---------CORRECT ANSWER-----------------True The percentage of error for loads used in the machine should not exceed _____ of the indicated load. ---------CORRECT ANSWER-----------------+_ 1 % The testing machine should have 2 steel bearing blocks: a spherically seated block and a solid block. True or false? ---------CORRECT ANSWER- ----------------True The _____ and _____ of the spherically seated bearing block must be designed so the steel in the contact area doesn't permanently deform when loaded to the capacity of the testing machine. ---------CORRECT ANSWER- ----------------ball and socketq The curved surface of the socket should be kept _____ and lubricated with _____ _____ _____ ---------CORRECT ANSWER-----------------clean, petroleum-based oil
Prior to testing the specimen, verify that the load indicator is _____ --------- CORRECT ANSWER-----------------zeroed Apply the load _____ and without ______ ---------CORRECT ANSWER------ -----------continuously, shock A higher rate of loading shall be permitted during the application of the first half of the nticipated loading phase, true or false? ---------CORRECT ANSWER-----------------True When the specimen fails, record the ____ _____ carried by the specimen during the test and note the ______ _______ ---------CORRECT ANSWER- ----------------Max Load, Fracture Type Calculate the compressive strength by dividing the _____ _____ by the average _____ _____ ______ ---------CORRECT ANSWER----------------- max load , cross sectional area What should a test report include? ---------CORRECT ANSWER----------------
The ____ _____ of Portland cement concrete is its ability to resist failure due to _____ stresses ---------CORRECT ANSWER-----------------flexural strength, bending What is ASTM C1231? ---------CORRECT ANSWER-----------------Standard Practice for use of Unbonded Caps in determination of compressive strength of hardened cylindrical concrete specimens (C1231) The height (cavity) of the metal retaining ring must be --------- CORRECT ANSWER-----------------(25 +/- 3mm) (C1231) If the retaining ring is greater than 4in (100mm) it must be at least __ thick. If it is less than 4in, it must be at least __ thick. ---------CORRECT ANSWER-----------------.47 in (12mm) and .35in (9mm) (C1231) Bearing surfaces of the retaining ring must not have gauges greater than ---------CORRECT ANSWER-----------------.01 inches (.25mm) deep or .05in (32mm) surface area (C1231) For specimen ends, depressions under a straightedge must not exceed ---------CORRECT ANSWER-----------------.2 inches (5mm) measured across any diameter using a round wire edge (C1231) Depressions on ends of specimens that exceed ___ must be corrected by sawing or grinding ---------CORRECT ANSWER----------------- .2in (5mm)
(C1231) Tolerance on Shore A durometer hardness is +/- __ --------- CORRECT ANSWER-----------------+/- 5 (C1231) The surface of the base plate that contacts the bearing block must be plane to within ___ in. ---------CORRECT ANSWER-----------------.002 in (.05mm) Unbonded caps can be used for ASTM C__, C___, and C___ --------- CORRECT ANSWER-----------------C31, C192, and C After application of the load, but before reaching 10% of the anticipated specimen strength, check to see that the axis of the cylinder does not depart from vertical by more than _____ degrees. ---------CORRECT ANSWER-----------------.5 degrees Qualification tests on an unbonded capping system must be repeated when ever there are changes in _____ (3) ---------CORRECT ANSWER------------- -----The design or dimensions of the retaining rings
What is ASTM C78 ---------CORRECT ANSWER-----------------Standard test method for Flexural strength of concrete (C78) When measuring the width and depth of the fractured face, take measurements to the nearest ___ ---------CORRECT ANSWER----------------
(C78) How should force on the specimen be loaded? ---------CORRECT ANSWER-----------------continuously and without shock (C78) Apply the load at a rate that constantly increases the maximum stress on the tension face between __psi/min and __psi/min --------- CORRECT ANSWER-----------------between 125psi/min and 175 psi/min (.9MPa/min and 1.2MPa/min (C78) The span length of a test specimen should be within what percent of three times the depth of the specimen as tested? ---------CORRECT ANSWER-----------------within 2% of three times the depth (C617) Sulfur should be heated to what temperature range? --------- CORRECT ANSWER-----------------265 and 290 degrees F (c617) Measure and record thickness of the cap to the nearest ___in --------
(C617) When capping cylinders it is acceptable to twist but not rock the capping plate in an effort to extrude___ ___ and ___ ___ ---------CORRECT ANSWER-----------------excess material and air voids (C617) Neat cement paste caps can ___ and ___ if allowed to dry --------- CORRECT ANSWER-----------------shrink and crack (C617) The end of a capped cylinder must be plane to within ___in --------- CORRECT ANSWER-----------------.002in (.05mm) (C617) Empty the pot and recharge with fresh material to ensure the oldest material is not reheated more than how many times? ---------CORRECT ANSWER-----------------5 times (C617) Cement paste should be applied to freshly molded cylinder within how many hours after molding to allow for settling of the concrete specimen ---------CORRECT ANSWER-----------------within 2 to 4 hours (C617) The vertical distance between the highest and lowest points on the end of an uncapped cylinder shall not exceed ___ ---------CORRECT ANSWER-----------------1/8 inch (3mm) (C617) The guide bar/bullseye level ensures caps are perpendicular to the axis within __ degrees ---------CORRECT ANSWER-----------------.5 degrees
What ASTM standard describes the apparatus, materials, and procedures for capping freshly molded concrete cylinders with neat cement? --------- CORRECT ANSWER-----------------ASTM C (C617) Plate size for capping must exceed the diameter of the test specimen by __in ---------CORRECT ANSWER-----------------1 inch (25mm) (c617) Guide bars and bullseyes are used to ensure that no single cap departs from perpendicularity to the axis by more than how many degrees - --------CORRECT ANSWER-----------------.5 degrees (C617) Sulfur mortar caps are formed against metal or stone plates. The recessed area that receives molten sulfur must not be deeper than ___in --- ------CORRECT ANSWER-----------------1/2 inch (12mm) (C617) If concrete strength is less than 5000psi, caps shall harden for a minimum of how many hours ---------CORRECT ANSWER----------------- 2 hours (C617) If concrete strength is greater than 5000psi, caps shall harden for a minimum of how many hours ---------CORRECT ANSWER----------------- 16 hours
(C617) For concrete cylinders with compressive strength greater than 7000psi, the maximum average thickness of the cap must be ___in --------- CORRECT ANSWER-----------------1/8 inch (3mm) (C1231) When testing for acceptance, unbonded capping systems are not to be used for concrete with a compressive strength less than ___psi or greater than ____psi ---------CORRECT ANSWER-----------------1,500 psi and 12,000 psi Thickness of the base plate must be at least __mm thick for a retainer greater than 100mm and __ thick for a retainer 100mm or smaller --------- CORRECT ANSWER-----------------12mm and 8mm Thickness of the retaining ring must be __mm thick for a retainers with nominal diameters greater than 100mm and __ thick for a retainers with a diameter of 100mm or smaller ---------CORRECT ANSWER----------------- 12mm and 9mm When qualification tests of unbonded pads are required, they are performed by the _____ or _____. ---------CORRECT ANSWER----------------
measure and record the thickness of a piece of cap to the nearest __ in ---- -----CORRECT ANSWER-----------------.01 in (.2mm) The ends of freshly molded cylinders can be capped with what material? --- ------CORRECT ANSWER-----------------Neat cement paste only (not high strength gypsum paste) In all cases, capping plates shall be at least __ in. greater in diameter than that of the test specimen ---------CORRECT ANSWER-----------------1 in (25mm) When checking the thickness of a cap, obtain at least __ random pieces distributed over the entire area of the cap ---------CORRECT ANSWER------ ----------- 6 ASTM C617 planeness of a cap is checked with a straight edge and feeler gauge to ensure that the surface of the cap does not depart from plane by more than __inches ---------CORRECT ANSWER-----------------.002inches When the diameter of the bearing face of a spherically seated block exceeds the diameter of the specimen by more than 13mm concentric circles not more than __ mm deep and __mm wide shall be inscribed to ensure proper centering ---------CORRECT ANSWER-----------------.8mm and 1mm
The ___ bearing block should provide a readily machinable surface for maintenance of the specified surface conditions ---------CORRECT ANSWER-----------------bottom Calibration of compression testing machine is required within an interval not to exceed __ months ---------CORRECT ANSWER----------------- 13 months Report the computed density to the nearest ___kg/m3 (__lb/ft3) --------- CORRECT ANSWER----------------- 10 kg/m3 (1lb/ft3) The percentage of error for loads used in the testing machine should not exceed +/- ___% ---------CORRECT ANSWER-----------------+/- 1% Specimens shall not be tested if individual diameter measurements for the cylinder differ by more than __ % ---------CORRECT ANSWER----------------- 2% Align the _____ of the specimen with the center of thrust of the spherically seated block. ---------CORRECT ANSWER-----------------axis True or false: When placing the lower bearing block on the table or platen, place the hardened face up ---------CORRECT ANSWER-----------------True
While measuring the specimens after the test procedure, if a fracture occurs at a capped section, do you include the thickness of the cap in your calculations? ---------CORRECT ANSWER-----------------Yes, include the thickness of the cap in the measurement (c78) The block surface in contact with the specimen shall not depart from plane by more than ___inch ---------CORRECT ANSWER----------------- .002in (.05mm) (C78) when measuring the width and depth dimensions of the fractured face, take measurements to the nearest ---------CORRECT ANSWER-------- ---------1 mm (.05in) The drying of the surface of the test specimen will result in a ___ of the measured flexural strength ---------CORRECT ANSWER----------------- reduction For flexural strength, the testing equipment must be capable of maintaining distances between load applying and support blocks constant within +/- ___in. ---------CORRECT ANSWER-----------------+/- .05inches (+/-1mm) For flexural strength, the final report should include both the average width and depth to the nearest __ inch ---------CORRECT ANSWER----------------- .05inches (1mm)
The block surface in contact with the specimen shall not depart from plane by more than ___inch ---------CORRECT ANSWER-----------------.002in ASTM Standard dealing with proper capping methods ---------CORRECT ANSWER-----------------C The procedure for capping enables concrete cylinders to meet the standard's requirements for ____ and ____ ---------CORRECT ANSWER---- -------------Planeness and Perpendicularity equipment needed for the capping process include ____, ____ devices, and ____ pots ---------CORRECT ANSWER-----------------plates, alignment, melting Plates for neat cement and high-strength gypsum plaster caps should be made of ____, ____, ____, or ____ ---------CORRECT ANSWER-------------- ---glass, metal, granite, diabase Sulfur mortar cap plates should be formed against _____ or _____ --------- CORRECT ANSWER-----------------metal or stone The purpose of the guide bar or bullseye level is that caps remain perpendicular to the axis of the cylinder within _____ degrees --------- CORRECT ANSWER-----------------.