ASTM C348-18 pdf free download.Standard Test Method for Flexural Strength of Hydraulic-Cement Mortars.
1.1 This test method covers the determination of the Ilexural strength of hydraulic-cement mortars.
1.2 The values stated in SI units are o be regarded as standard. No other units of measurement are included in this standard.
3. Terminology
3. 1 Definitions:
3. 1. 1 For definitions of terms used in this test method, refer to Terminology C125 and C219.
4. Summary of Test Method
4.1 The test mortar used consists of 1 part cement and 2.75 parts of sand proportion by mass. Portland or air-cntraining portland cements are mixed at specified water-cement ratios. Water content of other cements is that sufficient to obtain a flow of 110 ± 5 % with 25 drops of the flow table. Test prisms, 40 by 40 by 160-mm. are molded by tamping in two layers. Prisms are cured one day in the molds and stripped until tested by center point loading.
5. Significance and Use
5.1 This test method provides a means for determining the flexural strength of hydraulic cement mortars. Portions of the mortar prisms tested in flexure according to this test method may be used for the determination of compressive strength in accordance with Test Method C349.
5.2 The values arc determined from this test method for research or reference purposes only and are not used for determining compliance with specification requirements.
6.4 Specimen Molds—Molds for the 40 by 40 by 160-mm prism specimens shall he triple-gang molds and shall he so designed that the specimens will be molded with their longitudinal axes in a horizontal position. The molds shall be made of a hard metal, not attacked by cement mortar, and with a Rockwell hardness of not less than HRB 55. The parts of the molds shall he rnatchmarked and, when assembled, shall he tight-tItting and positively held together. The sides of the molds shall he sufficiently rigid to prevent spreading or warping. The interior faces of the molds shall be plane surfaces with a permissible variation, in any 50-mm line on a surface, of 0.03 mm for new molds and 0.05 mm for molds in use. The distance between opposite sides shall he 40 ± 0. 1 3 mm for new molds and 40 ± 0.3 mm for molds in use. The height of the molds shall be 40 mm with permissible variations of +0.25 and —0.15 mm for new molds, and +0.25 and —0.40 mm for molds in use. The inside length of the molds shall be 160 ± 2.5 mm. The angle between adjacent interior faces and top and bottom planes of the mold shall be 90 ± 0.5°, measured at points slightly removed from the intersections of the faces. The base plate shall be approximately 10 mm in thickness and shall have a plane surface 200 by 180 mm with a permissible variation in any 50-mm line on the surface of 0.03 mm.
6.5 Tamper—The tamper (see Fig. 1) shall be made of nonahsorptive, nonabrasive material, such as a rubber compound having a Shore A durometer hardness of 80 ± 10, or seasoned oak wood rendered nonahsorptive by immersion for 15 mm in paraffin at approximately 200°C. The face of the tamper shall be 22 by 85 mm.ASTM C348 pdf download.