ACI Concrete Strength Exam Study Guide - Questions and Answers These procedures for capping enable concrete cylinders and cores to meet the standard prac... [Show More] tice's requirements for _____ and _____. Planeness; perpendicularity Equipment needed for the capping process includes capping ____ ____ devices and _____ pots. Plates; alignment; melting Plates for neat cement and high-strength gypsum plaster caps should be made of ____, _____, or _____. Metal; glass; granite Sulfur mortar cap plates should be formed against _____ or _____ plates. Metal; stone True or false? The purpose of the guide bar or bull's eye level is to ensure that caps remain perpendicular to the axis of the cylinder within 0.5 degrees. True To avoid accidents during reheating of cooled sulfur, use melting pots that have _____. peripheral heating The technician should use a stiff layer of _____ to cap fresh concrete cylinders. neat cement paste Hardened concrete cylinders should be capped with ________, ______, or _______. High-strength gypsum paste; neat cement past; sulfur mortar True or false? Plasters of paris and mixtures of plaster of paris and portland are examples of suitable high-strength plasters. False Sulfar mortars and high-strength gypsum cement cubes must demonstrate a minimum compressive strength of _____ or _____, whichever is greater. 35 Mpa [5000 psi]; cylinder strength The cement paste should be applied to the freshly molded cylinder from _____ hours after molding. This is to allow for _____ of the concrete specimen. 2-4; settling The strength of the paste depends on:
A. The water-cement ratio B. Time C. The equipment used D. Type of cement A slight twisting action will help eliminate _____ and air _____ when the capping plate is placed onto the mound of paste. Excess paste; voids Neat cement paste caps should not be used on dry specimens because the caps may _____ and _____ when dry. Shrink; crack The technician should remove all _____ or _____ materials from the ends of hardened concrete cylinders before capping. Oily; waxy _____ the pot and recharge the fresh material at intervals to ensure that the oldest material has not been used more than _____ times. Empty; five True or false? When capping concrete cylinders with a comprehensive strength of 35 MPa [5000 psi] or greater, it is permitted to reuse compound recovered from the capping operation or old caps. False To avoid _____, the sulfur mortar should be dry when it is added to the pot. It should be kept away from _____ when heating. foaming; water The melting pot for the sulfur mortar must be located under a _____ with an _____ for _____. Hood; exhaust fan; ventilation Hydrogen sulfide gas, which may be produced during capping, may be _____ in high concentrations. In lower concentrations, the gas may result in _____, _____, _____, _____, and _____. Lethal, nausea, stomach distress, dizziness, headache, irritation of the eyes Unbonded caps may NOT be used for acceptance testing of concrete with compressive strengths below ... or above ... . 1500 psi [10 MPa] ... 12000 psi [80 Mpa] Elastomeric pads should not be more than ... smaller than the inside diameter of the retaining ring. 1/16th inch [2 mm] For a neoprene pad of a compressive strength of 13000 psi [89 MPa], what are the maximum reuses of the pad? 50 For a neoprene pad of a compressive strength of 10000 psi [80 MPa], what are the maximum reuses of the pad? 100 For a neoprene pad of a compressive strength of 5000 psi [34 MPa], what are the maximum reuses of the pad? 100 For a neoprene pad of a compressive strength of 4000 psi [28 MPa], what are the maximum reuses of the pad? 100 For a neoprene pad of a compressive strength of greater than 1000 psi [7 MPa], what are the maximum reuses of the pad? N/A (the test is not permitted) Only those tests or reuses within ... of the highest strength level will actually be included in the reuse count. 2000 psi [14 MPa] True or false? Laboratories must maintain records of the number of times that the pads are reused. True True or false? The unbonded end cap may be used greater than 50 times. True, if the compressive strength is less than 7000 psi [50 MPA] After 50 uses, test results may be used for greater than 50 times at... A. ±5000 psi of average strength B. ±5000 psi of highest strength C. ±2000 psi of average strength D. ±2000 psi of highest strength When qualification tests of unbonded pads are required, they are performed by the _____ or _____. Supplier; user True or False? This standard practice establishes a maximum number of pad reuses that may not be exceeded under any circumstances. False True or false? Polyurethane or butyl pads with a Shore A durometer hardness of 50 that will be used on concrete with a compressive strength of 10 to 40 MPa [1500 to 6000 psi]. It may be used "as is" from the manufacturer without further qualification testing. False To keep track of pad usage, the user is required to maintain records that will include _____, _____, and _____. date placed in service; pad durometer; number of uses True or false? The term "unbonded cap" refers to the combination of a metal retainer and elasomeric pad. True True or false? Practice C1231/C1231M may be used instead of the capping requirements of Practice C617/C617M. True True or false? The pads provide a uniform distribution of load from the bearing blocks of the testing machine by deforming in initial loading to conform to the contour of the ends of the cylinder. True When qualifying unbonded caps, strengths below _____ of the average obtained from the bonded caps is considered unacceptable. 98% True or false? Practice C1231/C1231M contains step-by-step procedures for aligning the specimens in the testing machine through complete failure of the cylinder. False The pads used in this practice must be _____ thick, and the diameter shall not be more than ____ smaller than the inside diameter of the retaining ring. 1/2 ± 1/16 inch; 1/16 in The height of the metal retaining ring must be _____. 1.0 ± 0.1 in The inside diameter of the retaining rings shall not be less than _____ or greater than _____ of the diameter of the cylinder. 102%; 107% Depressions in the ends of cylinders that exceed _____ must be corrected by sawing or grinding prior to testing. .20 in [Show Less]
