2023 second-level construction engineer construction gold test point Concrete uses raw materials, a must-test point for second-level construction, long press to like + forward + comment to continue to update, click on my avatar in the Wendang version to send me a private message: 2022
(2) ordinary concrete structure should use general portland cement ; for concrete with impermeability and freeze-thaw resistance requirements, portland cement or ordinary portland cement should be used.
(3) The maximum particle size of coarse aggregate should not exceed 1/4 of the minimum size of the component section, and should not exceed 3/4 of the minimum clear spacing of steel bars; for solid concrete slabs, the maximum particle size of coarse aggregate should not exceed 1/3 of the slab thickness, and should not exceed 40mm.
(6) Untreated seawater is strictly prohibited from being used for mixing and curing of reinforced concrete and prestressed concrete .
(8) concrete admixture should be selected according to the design and construction requirements, and determined through tests and technical and economic comparisons. Admixtures containing urea, ammonia and other pungent smelling ingredients shall not be used in housing construction projects.
Example: A certain construction project, construction area 23824㎡. There are 10 floors above ground and 2 floors underground. The exterior wall of the main basement of the structure is poured with P8 waterproof concrete . The wall thickness is 250mm and the clear distance between steel bars is 60mm. The following events occurred during the construction process: During the pouring of waterproof concrete for the exterior wall of the basement of the main structure, the maximum particle size of the coarse aggregate was tested on site, and the test result was 40mm.
[Question] In the incident, was the maximum particle size control of concrete coarse aggregate accurate? Please analyze the maximum particle size of the waterproof concrete in this project from three aspects: the cross-sectional size of the underground structure exterior wall, the clear distance between steel bars and the design principles of waterproof concrete.
【Answer】 (1) Accurate. Coarse aggregate particle size does not exceed 40mm to meet the requirements.
(2) Reasons: ① It should not exceed 1/4 of the minimum size of the component section, 250mm×1/4=62.5mm ② It should not exceed 3/4 of the clear distance of the steel bars, that is, 60×3/4=45mm ③ According to the design principles of waterproof concrete, the maximum particle size of coarse aggregate should not be larger than 40mm.
so concrete aggregate is qualified.
