Magnesium phosphate cement with good water resistance and application thereof

Abstract

The invention relates to the technical field of building materials, in particular to magnesium phosphate cement with good water resistance. The cement disclosed by the invention is prepared from the following raw materials in parts by weight: 50 to 100 parts of pre-modified caustic calcined magnesite, 15 to 30 parts of composite acidic phosphate, 6 to 12 parts of a water-reducing retarder, 6 to 12parts of a pH value regulating agent, 20 to 40 parts of ultrafine filling aggregate, 0.5 to 1.5 parts of a composite expansion component, 0.5 to 2 parts of a slow-release hydrophobic component and 0.5 to 2 parts of a thixotropic lubricant. The invention also provides a preparation method of the cement. The magnesium phosphate cement with good water resistance has the characteristics of good waterresistance, high setting time controllability, good construction performance, early strength, high strength, high bonding strength, strong rib protection performance and good aging resistance.

Description

technical field [0001] The invention relates to the technical field of building materials, in particular to a magnesium phosphate cement with good water resistance. Background technique [0002] Magnesium phosphate cement has a series of excellent properties such as early strength, fast hardening, and high bond strength. It has been well applied in the field of rapid concrete repair and reinforcement. prospect. [0003] However, magnesium phosphate cement currently has the following problems: the setting speed is fast and the setting time is uncontrollable. Secondly, the water resistance is relatively poor. In a humid and water-immersed environment, its compressive strength or bond strength will shrink, so it is strictly limited. its scope of application. The reason why the water resistance of magnesium phosphate cement is poor is mainly attributed to the following points: First, the hydration reaction of magnesium phosphate cement is too fast so that the phosphate cannot ...

AI Technical Summary

Problems solved by technology

[0003] However, magnesium phosphate cement currently has the following problems: the setting speed is fast and the setting time is uncontrollable. Secondly, the water resistance is relatively poor. In a humid and water-immersed environment, its compressive strength or bond strength will shrink, so it is strictly limited. range of application

Patent CN 108249795 A discloses a magnesium phosphate cement whose main ingredients are magnesium oxide mixture, dihydrogen phosphate, and setting retarder. This technology uses borax and boric acid as retarding agents to reduce the amount of free water evaporated and retained by delaying heat release. holes, but the retarding effect of borax and boric acid is limited

[0005] Based on the above technologies, it can be seen that magnesium oxide can be modified by retarders such as borax or boric acid, that is, by forming a slow-release layer on the surface of magnesium oxide, but the retarding effect is not good, and adding too much retarder will cause It affects the late hydration reaction of magnesium phosphate cement; the problem of fast solidification cannot be fundamentally solved by grinding phosphate, and reducing the amount of phosphate affects the strength of magnesium phosphate cement; only by reducing water consumption can It is not conducive to the fluidity of the slurry. On the contrary, the poor fluidity accelerates the solidification and produces more pores due to poor operability; and the water-reducing agent suitable for the Portland cement system, from the traditional Nai-based water-reducing agent based on electrostatic repulsion and based on Polycarboxylate superplasticizers with steric hindrance, due to the influence of the acidic environment in the initial stage of hydration of magnesium phosphate cement, cannot show effective water reducing effect on magnesium phosphate cement

That is to say, the above-mentioned measures for the poor water resistance of magnesium phosphate cement have not achieved obvious results, or only focus on water resistance and affect the strength of magnesium phosphate cement

The reason why it can't play an effective role is because it doesn't fundamentally solve the problem that magnesium oxide needs too much water and the hydration rate is fast.