Composite retarder for controlling setting time and hydration heat release characteristic of potassium magnesium phosphate cement paste and control method of composite retarder

Abstract

The invention discloses a composite retarder for controlling the setting time and hydration heat release characteristic of potassium magnesium phosphate cement paste and a control method of the composite retarder. The composite retarder is powdery, the particle size ranges from 10 micrometers to 250 micrometers, and the composite retarder comprises, by mass, 15.0%-25.0% of nitrite, 1.0%-20.0% of zinc oxide, 26.0%-38.0% of borax, and 26.0%-48.0% of disodium hydrogen phosphate dodecahydrate, wherein the total percentage of the four components is 100%. The composite retarder can effectively adjust the setting time of the potassium magnesium phosphate cement paste within 20-180 min, can meet the construction operation requirements, ensures that the hydration heat is released in two stages during the hydration reaction of the potassium magnesium phosphate cement paste, and the hydration heat release amount at the initial stage of hydration is small. The composite retarder can obviously improve the strength of slurry after 1d, does not contain chloride ions, and can enlarge the application range of a potassium magnesium phosphate cement-based material.

Description

Technical field [0001] The invention belongs to the technical field of potassium magnesium phosphate cement preparation, and specifically relates to a composite retarder for controlling the setting time and hydration exothermic characteristics of potassium magnesium phosphate cement slurry and a control method thereof. Background technique [0002] Magnesium phosphate cement, or chemically bonded magnesium phosphate ceramic, is a fast-hardening and early-strength cementing material. It is prepared from dead-burned magnesium oxide powder, phosphate, admixtures, retarder, etc. It can be mixed with water to It condenses and hardens in a relatively short period of time to form a dense structure similar to sintered ceramics. Cement-based materials prepared with magnesium phosphate cement as adhesive have excellent properties such as high early strength, low shrinkage, resistance to freezing and salt freezing, and resistance to salt erosion. [0003] The hydration reaction of mag...

AI Technical Summary

Problems solved by technology

Reducing the activity of dead-burned magnesia powder requires a higher calcination temperature and is difficult to control. Too thick dead-burned magnesia powder will affect the fluidity and early strength of magnesium phosphate cement slurry, and the retarding effect when the ambient temperature is high not obvious

Reducing the activity and fineness of dead-burned magnesium oxide powder can not change the characteristics of concentrated release of hydration heat of magnesium phosphate cement slurry

[0007] (3) Increasing the phosphate content in the magnesium phosphate cement slurry or combining acid phosphate and basic phosphate can appropriately delay the setting time of the magnesium phosphate cement slurry, but when more phosphate is added, it will increase the magnesium phosphate The cost of cement and the reduction of the strength and water resistance of magnesium phosphate cement, the retarding effect is not good when the ambient temperature is high, and the characteristics of the concentrated release of hydration heat of magnesium phosphate cement slurry cannot be changed

Using low-temperature cooling water to mix magnesium phosphate cement slurry to delay the setting time of magnesium phosphate cement slurry, but it can only be delayed for a few minutes, and the characteristics of the concentrated release of hydration heat of magnesium phosphate cement slurry cannot be changed

[0009] (5) Adding composite retarders (borax, disodium hydrogen phosphate dodecahydrate and inorganic chloride salts) can effectively delay the setting time of potassium magnesium phosphate cement, and change the concentrated release of heat of hydration to two during the slurry hydration reaction. Phase release, although the early intensity is appropriately reduced, but the later intensity increases

The disadvantage is that the composite retarder contains inorganic chloride salts, which will corrode steel and limit the scope of long-term use.

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