This specification outlines the standards for autoclaved cellular (aerated) concrete blocks used as masonry units in construction projects. It details the required materials, production methods, physical and mechanical characteristics, dimensional allowances, testing protocols, and marking criteria. The standard is essential for producers, suppliers, and engineers utilizing these blocks for load-bearing and partition walls.
Overview
This specification outlines the standards for autoclaved cellular (aerated) concrete blocks used as masonry units in construction projects. It details the required materials, production methods, physical and mechanical characteristics, dimensional allowances, testing protocols, and marking criteria. The standard is essential for producers, suppliers, and engineers utilizing these blocks for load-bearing and partition walls.
Audience
Contents
Structure
This section defines the extent of the standard covering concrete masonry units in the form of autoclaved cellular concrete blocks, including specifications for dimensions, density, and measurement methods. It highlights density limits as per designated tables and details measurement points on blocks for length, height, and thickness to maintain quality consistency.
This part provides definitions related to autoclaved cellular concrete blocks, including parameters such as density, compressive strength, and thermal conductivity. It presents a classification table correlating density ranges with minimum compressive strength values and maximum thermal conductivity limits, facilitating appropriate block selection.
Outlined here are the nominal sizes for length, height, and width of blocks, along with the number of measurement locations for each dimension to ensure accuracy. It also specifies the tolerances allowed on these dimensions, depending on block size, to guarantee uniformity and suitability for construction.
This segment details the classification system for blocks based on oven-dry density, with associated grades reflecting minimum compressive strength levels. It also covers thermal conductivity variations across density classes and specifies manufacturing conditions for blocks with special surface profiles.
This section discusses the physical properties required for the blocks, including limits on thermal conductivity and minimum compressive strength values per density grade. It emphasizes the use of oven-dry density measurements and air-dry conditions for thermal testing, ensuring compliance with defined standards.
Describes the production methodology for autoclaved cellular concrete blocks, involving the mixing of cementitious materials, lime, sand, water, and aluminum powder, followed by molding and autoclaving to attain the desired physical properties. It also addresses quality parameters such as strength and density verification post-production.
This section specifies the required physical properties of the blocks, including density, minimum compressive strength for different grades, and maximum permissible thermal conductivity. It outlines the testing procedures for these properties to ensure blocks fulfill performance criteria.
Outlined here are the mechanical characteristics of the blocks, focusing on compressive strength testing methods, acceptance criteria based on statistical evaluation, and thermal conductivity limitations. The section also includes formulae used to verify compliance with minimum strength requirements.
Details the methods for conducting tests on compressive strength, density, and thermal conductivity, including sample sizes, test setups, and calculation formulas. It emphasizes adherence to prescribed testing clauses to guarantee reliable and standardized results.
Describes the sampling strategies for block inspection, including the allowable number of defective units, dimensional measurement points, and visual quality checks. It also outlines procedures for collecting samples for independent testing and ensures compliance with the inspection criteria.
This section defines the standards for compliance based on average compressive strength, density, and thermal conductivity values. It provides guidance on sample distribution for tests and stipulates adherence to testing methods and limits specified in the standard to confirm block conformity.
Explains the requirement for manufacturers to issue certificates affirming that blocks meet all specified standards, including dimensional tolerances, compressive strength, drying shrinkage, and other mechanical and physical properties. The certification serves as assurance to purchasers regarding product quality.
Outlines the need for independent testing of blocks, specifying sample sizes, testing frequency, and the manufacturer’s responsibility to verify compliance. It also details the process for issuing certificates based on test outcomes and actions to be taken if blocks do not meet standards.
Provides recommendations for proper storage and handling of the blocks to prevent damage and moisture absorption, including stacking techniques, use of pallets, protection from weather, and maximum stacking heights, aligned with relevant storage standards.
Specifies the marking information to be included on each batch or individual block, such as manufacturer identification, block grade, density classification, manufacturing date, and optional ISI certification mark. These markings facilitate traceability and quality assurance.
Frequently Asked
According to IS 2185 Part 3 (1984), the manufacturing of autoclaved cellular concrete blocks typically involves Ordinary Portland Cement (OPC) conforming to IS 269 or IS 8112. Aggregates include sand meeting IS 383-1970 standards with a minimum silica content of 80%, and fly ash complying with IS 3812-1981, having a loss on ignition not exceeding 6%. These materials ensure the blocks possess adequate strength and durability.
IS 2185 Part 3 prescribes nominal dimensions such as lengths of 400, 500, or 600 mm; heights of 200, 250, or 300 mm; and widths of 100, 150, 200, or 250 mm. The actual dimensions are permitted to be up to 10 mm less than nominal for standard blocks, with a reduced tolerance of up to 6 mm less allowed for fine jointing applications. Width is measured at the bedding plane, perpendicular to length and height, ensuring uniform mortar joints and dimensional consistency.
Compressive strength testing under IS 2185 Part 3 requires selecting 12 blocks from a sample of 24. Testing follows IS 6441 (Part 5)-1972 procedures, where blocks are compressed until failure, and the average strength is calculated. The mean compressive strength must meet or exceed the minimum values specified in Table 1 of the standard, which varies according to block density and grade.
As per IS 2185 Part 3, the thermal conductivity of autoclaved cellular concrete blocks must not exceed the limits detailed in Table 1, which vary according to the oven-dry density of the blocks. Generally, lower density blocks have thermal conductivity around 0.21 to 0.42 W/m·K, ensuring good insulation properties. Testing is conducted following Clause 9.3 to confirm compliance.
Sampling should be performed either before or immediately after delivery at regular intervals during loading or unloading. If this is not feasible, samples can be randomly taken from accessible locations within the stack. From a total of 24 sampled blocks, 12 are tested for compressive strength, 3 for density, 3 for thermal conductivity, and 3 for drying shrinkage, with an additional 3 reserved for potential re-testing. Samples must be properly marked and protected to maintain testing integrity.
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