The 1988 edition of IS 4031 Part 7 outlines the standardized procedure to measure the compressive strength of masonry cement by utilizing 50 mm mortar cubes. It covers detailed instructions on sample collection, mortar mixing, curing conditions, and testing protocols to guarantee uniform and accurate strength assessment. This code is crucial for ensuring quality assurance and verifying compliance of masonry cement in construction.
Overview
The 1988 edition of IS 4031 Part 7 outlines the standardized procedure to measure the compressive strength of masonry cement by utilizing 50 mm mortar cubes. It covers detailed instructions on sample collection, mortar mixing, curing conditions, and testing protocols to guarantee uniform and accurate strength assessment. This code is crucial for ensuring quality assurance and verifying compliance of masonry cement in construction.
Audience
Contents
Structure
Frequently Asked
According to IS 4031 Part 7, mortar cubes must be 50 mm in size. For each set of three specimens, mix 420 grams of masonry cement with 1440 grams of standard sand as per IS 650-1966. The materials are to be thoroughly blended, cast into the 50 mm cube moulds, compacted, and then cured for 7 and 28 days prior to compressive strength testing. This process ensures uniform strength evaluation of the masonry cement mortar.
The flow of mortar is determined by filling a mould placed on a clean and dry flow table with two layers of 25 mm fresh mortar, each tamped 20 times with a rod. After leveling the surface, the mould is lifted vertically one minute post-mixing, and the table is dropped 25 times from a height of 12.5 mm within 15 seconds. The spread diameter is measured at four equal points, and the flow percentage is calculated by comparing the average diameter to the original mould diameter. This procedure ensures consistent mortar workability before casting specimens.
Immediately after moulding and compaction, specimens should remain in their moulds on flat plates inside a moist cabinet maintained at 27 ± 2°C and relative humidity not less than 90% for 48 to 52 hours, with the top surfaces exposed to moist air. Following this, cubes are demoulded and kept in the moist cabinet with free air circulation around at least five faces for 5 days. For 7-day strength measurements, specimens are tested immediately after this period. For 28-day tests, cubes are submerged in clean water in non-corrosive tanks at 29 ± 2°C for an additional 21 days before testing.
IS 4031 Part 7 specifies the use of an electrically operated compression testing machine fitted with self-aligning steel platens, where one platen is fixed to the base. No packing material should be placed between the cube and platens. The machine must apply load continuously at a rate that causes failure within 20 to 80 seconds, with initial loading up to half the expected maximum load if that load exceeds 13,500 N. Additionally, curing cabinets maintaining 27 ± 2°C and ≥90% relative humidity and non-corrosive water tanks for 28-day curing are essential to ensure reproducible and reliable results.
The compressive strength (f_c) is calculated by dividing the maximum load at failure (P, in Newtons) by the cross-sectional area (A, in mm²) of the cube face, using the equation f_c = P/A. The standard cube size is 70.6 mm per side, resulting in an area of 4984.36 mm². Tests are conducted on the cube sides without packing between the specimen and platens. The compressive load is applied continuously to cause failure within 20 to 80 seconds. The average strength from at least three specimens per curing age is used to assess the masonry cement quality, with rounding done per IS 2:1960 guidelines.
Ask AI about any clause, requirement, or provision in IS 4031 PART 7. Get instant, clause-cited responses powered by our indexed library.
Free tier includes 150 queries (50 AI + 100 Reference) · No credit card required