Fluorosilicate Additives for Magnesium Silico-Phosphate Cement Hardening Control
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Solution Overview
Problem
Current methods for controlling the hardening rate of magnesium silico-phosphate cements (MSPCs) are inadequate, as existing retardants either extend workability by limited amounts or compromise compressive strength, and there is a need for a more precise method to manage the hardening process.
Innovation Solution
The use of commercially available salts and acids of complex fluoride anions, such as [MF6]n-, as additives to alter the hardening rate of MSPCs, functioning as either retardants or accelerants, without adversely affecting the compressive strength of the cement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If borate salts or boric acid are used as retardants to extend workability time, then the time before cement sets is extended from about 10 minutes to about half an hour, but the compressive strength deteriorates significantly when larger amounts of retardant are added
Solution Approach 1:
The patent changes the chemical parameters of the retardant by using fluorosilicates instead of borate salts, and by controlling the concentration within a specific range (0.01-1.0% by weight). This parameter change allows extension of workability time without the significant compressive strength deterioration that occurs with conventional retardants at higher concentrations.
Solution Approach 2:
The patent employs fluorosilicates as a temporary retardant that performs its function of extending workability time and then is consumed or transformed during the hardening process. The retardant is added in controlled amounts and serves its purpose during the critical workability period before the cement sets, after which it no longer interferes with the final strength properties.
2Ease of manufacture
If polycarboxylic acids or polyphosphonic acids are used as retardants, then the cement composition is modified, but the set time is not significantly extended
Solution Approach 1:
The patent changes the chemical parameters by using fluorosilicates instead of polycarboxylic acids or polyphosphonic acids. This parameter change results in both composition modification and significant extension of set time, achieving both ease of manufacture and extended workability time simultaneously.
3Duration of action of moving object
If fluorosilicates are used as retardants to extend set time by delaying mixing of acid and base fractions, then the rate of formation of hydrated salt is reduced, but the method becomes more complex
Solution Approach 1:
The fluorosilicate retardant automatically performs its function by interfering with the formation of the hydrated salt complex when mixed with water. The retardant self-regulates the hardening process without requiring complex control mechanisms or separate mixing stages, thereby extending set time while maintaining process simplicity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These additives significantly alter the hardening rate of MSPCs, providing more precise control over the setting time while maintaining the compressive strength of the cement, with effects lasting beyond the mixing period and not deterring the final compressive strength.
Implementation Method 1
the rate of formation of the complex hydrated salt MMgPO4·6H2O
Implementation Method 2
chemically bonded silico-phosphate cements
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
A method is provided for advantageously altering the rate of hardening of a magnesium silico-phosphate cement (MSPC). Addition of on the order of 1% of an [MF6]n- salt or acid to an MSPC, obtained by adding the salt or acid either directly to the dry mix or to the water used to effect hydraulic hardening of the cement, significantly alters the hardening rate without adversely affecting the physical properties of the final set cement. In preferred embodiments, Na2TiF6 and/or K2TiF6 are used as retardants, while K3AlF6 is used as an accelerant. Other embodiments use M'nMF6 compounds wherein M' is an alkali metal, an alkaline earth metal, or H, and M is chosen from inter alia Ti (n = 2), Zr (n = 2), Si (n = 2), P (n = 1), Al (n = 3), and Sb (n = 1).