Recently, the Department of Housing and Urban-Rural Construction of Liaoning Province issued the Technical Regulations for the Application of Machine-made Sand, which was formulated by Liaoning Construction Guidance Service Center, Liaoning Construction Science Research Institute Co., Ltd., Liaoning Building Materials Industry Association and other relevant units, and approved as the local standard of Liaoning Province. The serial number is DB21/T3761-2023, which is now issued and implemented from July 30, 2023.
The Technical Specification for Application of Machine-made Sand is applicable to the quality control of machine-made sand in Liaoning Province and the mix proportion design, preparation, construction, quality inspection and acceptance of machine-made sand concrete and mortar used in construction projects. In the application process, in addition to the implementation of this regulation, it should also comply with the provisions of the current relevant standards of the state and Liaoning Province.
It is understood that, Machine-made sand is divided into Class I, Class II and Class III according to technical requirements:
Class I sand is suitable for concrete with strength grade greater than or equal to C60 and high performance concrete, Class I and Class II sand is suitable for concrete with strength grade of C30 ~ C55, and Class I, Class II and Class III sand is suitable for concrete with strength grade less than or equal to C25. Machine-made sand of Class I, II and III can be used for mortar of various strength grades. The fineness
of machine-made sand can be divided into coarse sand, medium sand and fine sand according to its fineness modulus, and shall meet the following requirements: coarse sand: 3.7 ~ 3.1, medium sand: 3.0 ~ 2.3/fine sand: 2.2 ~ 1.6. The
particle size distribution shall comply with the following provisions:
the particle size distribution of machine-made sand can be exceeded except for the 4.75mm and 0.60mm sieve, but the total excess value of the cumulative sieve residue at all levels shall not be greater than 5%; for sand for mortar, the sub-sieve residue of the 4.75mm sieve shall be 0%.
In addition, the radioactivity of machine-made sand used in construction projects shall comply with the provisions of the Limits of Radionuclides in Building Materials GB6566. The compressive strength of the parent rock
used for the production of machine-made sand shall conform to the provisions of GB/T14685 Pebble and Gravel for Construction. Mechanical properties and durability
of machine-made sand concrete shall comply with the provisions of Code for Design of Concrete Structures (GB50010), Standard for Quality Control of Concrete (GB50164) and Standard for Durability Design of Concrete Structures (GB/T50476). The performance index of machine-made sand mortar shall comply with the provisions of Ready-mixed Mortar (GB/T25181) and Technical Specification for Application of Ready-mixed Mortar (JGJ/T223). The mix proportion
of machine-made sand concrete and machine-made sand mortar shall conform to the design requirements and the provisions of relevant standards, and the mix proportion shall be determined through test optimization.
For projects with concrete alkali-aggregate reaction design requirements, the provisions of Technical Code for Prevention of Concrete Alkali-Aggregate Reaction (GB/T50733) shall also be followed.
Machine-made sand and natural sand shall be mixed for use, and the preparation proportion shall be determined by test. The quality of natural sand shall conform to the provisions of GB/T14684 Sand for Construction. After entering the factory,
the machine-made sand shall be sampled and re-inspected, and the machine-made sand that fails to pass the inspection shall not be used. Forced mixing technology shall be adopted for machine-made sand concrete and machine-made sand mortar.
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