The standard outlines the essential criteria for compression testing machines employed in assessing concrete and mortar samples. It mandates precise design, manufacturing, and calibration to guarantee steady, shock-free compressive force application while adhering to strict dimensional and measurement tolerances. This guideline is pivotal for producers, testing labs, and quality assurance professionals to ensure dependable and uniform test outcomes.
Overview
The standard outlines the essential criteria for compression testing machines employed in assessing concrete and mortar samples. It mandates precise design, manufacturing, and calibration to guarantee steady, shock-free compressive force application while adhering to strict dimensional and measurement tolerances. This guideline is pivotal for producers, testing labs, and quality assurance professionals to ensure dependable and uniform test outcomes.
Audience
Contents
Structure
This section defines the scope of the standard, covering the testing methods and dimensional criteria for bearing blocks used in structural testing applications. It also details rounding rules compliant with IS 2:1960 and specifies maximum bearing face diameters for suspended spherically seated blocks based on specimen size, permitting square faces provided the inscribed circle diameter remains within limits.
Lists standards incorporated by reference within this code. Emphasizes the importance of consulting the latest editions of these standards. Highlights rounding practices per IS 2:1960, surface texture requirements (R-value between 0.4 µm and 3.2 µm), and bearing face diameter constraints aligning with specimen dimensions.
Provides key definitions by referencing related standards such as ASTM C39-86. Includes rounding procedures as per IS 2:1960 and clarifies that no direct formulas or tables are included in this section, directing readers to associated standards for detailed testing methodologies.
Covers rounding conventions, dimensional limits for bearing blocks corresponding to specimen sizes, and references essential associated standards like IS 516:1959. Includes graphical representation of bearing face sizing criteria to enforce uniformity and accuracy.
Specifies that load pacers must feature essentially linear scales with a resolution of 1 mm corresponding to no more than 100 N/s, maintaining accuracy within ±5%. Load scale indicators should have clear visual displays and include resettable maximum load registers with needle widths narrower than scale graduations to enhance readability.
Details requirements for bearing blocks including free rotation and minimum tilt of 4° in spherical seats, surface roughness parameters for auxiliary platens, and hardness and dimensional criteria for spacing blocks to assure proper load distribution and durability.
Describes the surface texture limits for auxiliary platens, maximum count of spacing blocks allowed (up to four), their flatness and parallelism standards, and movable bearing face characteristics such as free rotation and tilt of at least 4°, ensuring consistent load application.
Outlines the material hardness requirement of minimum 550 HV as per IS 1501, resistance against permanent deformation, flatness and parallelism tolerances identical to auxiliary platens, surface roughness limits, and bearing face diameter restrictions based on specimen size.
Mandates clear, permanent markings on machines including manufacturer’s name or trademark, manufacturing date (month and year), and unique serial numbers. Discusses optional use of BIS Standard Mark subject to licensing under the Bureau of Indian Standards Act, 1986.
Prescribes periodic verification intervals and immediate checks if accuracy is questioned. Defines a five-point load testing method with increments not exceeding one-third of the load range, error calculation formulas, and the requirement for elastic calibration devices that must fit the specimen space and provide legible readings.
Specifies surface roughness for auxiliary platen contact faces, requirements for readable load indicators with resettable maximum load registers, movement speeds for screw and hydraulic machines, and mandatory machine markings. Emphasizes maintaining detailed performance records for quality assurance.
Lists the members of the Cement and Concrete Sectional Committee CED 2, representing government research labs, industry, academia, public works departments, and specialized agencies. Highlights the inclusion of alternate members and the broad expertise contributing to the development of the standard.
Frequently Asked
Per IS 14858, auxiliary platens and spacing blocks must have a minimum Vickers hardness of 550 and resist permanent deformation during use. Steel bearing blocks should have hardened faces with hardness not less than 550 Vickers. These blocks include one spherically seated block on the specimen’s upper surface and a solid block beneath the specimen. The bearing face dimensions must be at least 3% larger than the specimen diameter, with flatness tolerances of 0.025 mm or 0.0225 mm depending on size. This ensures component durability and testing precision.
The standard requires machines to undergo periodic verification as outlined in clauses 10.1.1 to 10.1.3. Additionally, verification must be conducted immediately whenever there is doubt about the machine’s accuracy. The procedure involves applying five test loads in ascending order, with load increments not exceeding one-third of the total load range, and recording machine-indicated and applied loads to compute errors. This process guarantees reliable and accurate test results.
IS 14858 specifies that platen contact faces must have flatness within 0.03 mm, parallelism relative to a datum face within 0.06 mm, and squareness between adjacent edges within 0.06 mm. Spacing blocks must comply with the same flatness and parallelism requirements as auxiliary platens. These strict tolerances ensure uniform load application and accurate compressive strength testing.
The standard mandates that load be applied gradually and monotonically at rates specified in IS 516. Screw-type machines should operate at an idle moving head speed of about 1.3 mm per minute, while hydraulic machines should apply load at a rate between 0.14 and 0.324 MPa per second. This controlled loading prevents shocks and ensures consistent compressive strength measurement.
Load indicators must feature easily readable dials, scales, or electrical displays with clear visual outputs, supplemented optionally by calibrated recording devices. The system should include a resettable device to register the specimen’s maximum load. Pointer needles must be narrower than the scale graduations to improve reading accuracy. Regular verification using five test loads with controlled increments ensures maintenance of calibration and measurement reliability.
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