Securing hardened specimens concrete from the

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Unformatted text preview: ween the mortar and the coarse rn genera1 the concrete shall be 14 days old before the speciaggregate. mens are removed. Specimens that show abnormal defects or that have been damaged in removal shall not be used. E-3. APPARATUS B-3.1 Core Drill - A core drill shall be used for securing cylindrical core specimens. For specimens taken perpendicular to a horizontal surface, a diamond drill shall he used. B-3.2 Saw -. A saw shall be used for securing beam specimens from the structure or pavements for flcxural strength tests. The saw shall have a diamond or silicon carbide cutting edge and shall have adjustments that will permit cutting specimens which conform to the dimensions prescribed under B-4.2. B-4. !WECIMENS B-4.1 Core Specimen - A core specimen for the determination of pave mrnt thickness shall have a diamet-r of at least 10 cm (or 4 in ). A core specimen for the determination of compressive strength shall have a diameter at least three times the maximum nominal size of the coarse aggregate used in the concrete, and in no case shall the final diameter of the specimen be less than twice the maximum nominal size of the coarse aggre.gate. The length of the specimen, when capped, shall be, as nearly as practicable, twice its drameter. 39 IS : 457 - 1957 B-4.2 Beam Specimen - A bcsm specm~cn for the determination of flexural strength. in general, shall iia.ve a cross-section of 15 X 15 cm (or 6 x 6 in ). The specimen shall be at least 53 cm ( or 21 in ) in length but when two tests for flexural strength are desired for one beam specimzn, it shall be at least 84 cm ( or 33 in ) in length. NoTE - In mauy ca.&s, the width shall be governed hy the thickness ot the slab. B-5. particularly with prisms cut from pavement slal=. by the size of the coarse aggregate and the depth PROCEDURE B-5.1 Core Drilling - A core specimen taken perpendicular to a horizontal surface shall bc located, when possible, so that its axis is pcrpendicular to the bed of the concrete as originally placed. A specimen taken perpendicular to a vertical surface, or perpendicular to a surface with a batter, shall be taken from near the middle of a unit of deposit. i.e., 380 cu m ( or 500 cu yd ) of mass concrete and from 190 cu m (or 250 cu yd) of reinforced concrete placed in any one day’s run. B-5.2 Slab Removal - A sufficiently large slab shall ‘be removed so that the desired test spccimcns may be secured without the inclusion of any concrete whicll has been cracked, spalled, undercut, or otherwise damaged. B-5 3 Beam Sawing - The sawing operation shall be so performed that the concrete will not bc weakened by shock or by heating. The sawed surfaces shall bc smooth, plant, parallel. and free from steps, ridges and grow ves. Care si~all be taken in handling sawecl beam specimens to avoid chipping or cracking. B-6. COMPRESSIVE STRENGTH B-6.1 End Preparation--Core specimens to be tested in compression shall have ends that arc essentially smooth. perpendicular to the axis, and of t...
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This document was uploaded on 10/01/2013.

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