A special mixed cement for on-site preparation of concrete and its preparation method and application

Abstract

The invention relates to the field of cement and concrete. The invention discloses special mixed cement for on-site preparation of concrete as well as a preparation method and application. Except formixing and grinding cement clinker and other raw materials, the mixed cement is prepared from the following components in percentage by mass: 60%-80% of general Portland cement of the 42.5 grade or above, 3.0%-6.0% of gypsum, 5%-15% of limestone, 2%-29% of an admixture and 0.5%-3.0% of a functional additive. The general Portland cement with the grade of 42.5 or above meets the requirements of GB175, and parameters of the general Portland cement are controlled such that the mass ratio of the micro powder less than or equal to 3 [mu]m is less than or equal to 10%, the one-day compressive strength is less than or equal to 12 MPa, the 3-day compressive strength is more than or equal to 20 MPa, the 28-day compressive strength is more than or equal to 45 MPa, the water consumption of the standard consistency of the cement paste is less than or equal to 28%, the alkali content is less than 0.6% in terms of 0.658 K2O + Na2O, and the chloride ion content is less than 0.06%. The raw materials are wide in source, the mixed cement can be directly used for preparing or premixing concrete on site, no admixture or functional additive needs to be added again, crack resistance, workability and themechanical property of the concrete are improved, and construction operation is simplified.

Description

technical field [0001] The invention relates to the technical field of cement and concrete production, in particular to a special mixed cement for on-site preparation of concrete and its preparation method and application. Background technique [0002] According to the design, construction and acceptance specifications of construction projects, the concrete strength of various parts of common construction projects can be divided into: ① general cushion C10-C15; pile concrete generally above C30; foundation beams, slabs, caps, and columns generally C25-C35 ; ② wall columns are generally C20-C35 (according to the building needs higher strength); ③ floors are generally C20-C30; ④ other secondary structures are generally C20-C30. [0003] According to statistics, domestic C15-C30 strength grade concrete accounts for more than 75% of all concrete. In 2018, the largest commercial concrete company in Hunan Province sold 16.5 million cubic meters of commercial concrete, and the weig...

AI Technical Summary

Problems solved by technology

and little or no SO in the admixture 3 , only by SO in cement 3 , affecting the sulfate ion content in the cement system, which may aggravate the poor adaptability between the cementitious material and the water reducer, and will lead to the SO required for the hydration reaction of the cementitious material in concrete 3 severely deficient or deficient

And SO in concrete 3 It not only affects the setting time, water demand properties, strength development law and compatibility with admixtures of the concrete mixture, but also affects the volume deformation of the concrete, increasing the risk of cracking, and it is easy to cause cracking when the deformation or shrinkage is large

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