Hydrothermal Calcium Silicate Hydrate Production for Low-Viscosity Curing
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Solution Overview
Problem
Existing calcium silicate hydrate-based curing accelerators for hydraulic binders face issues such as high viscosity, corrosivity, and limited handling and application difficulties, which hinder their economic feasibility and effectiveness in enhancing early strength development of cementitious compositions.
Innovation Solution
A process involving the reaction of a calcium hydroxide source with silicon dioxide under hydrothermal conditions, followed by the addition of a water-soluble polymeric dispersant and an organic compound with specific molecular weight and functional groups, to produce a semi-ordered calcium silicate hydrate with improved stability and pumpability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If calcium silicate hydrate nuclei are produced by reaction of water-soluble calcium component with water-soluble silicon component, then the accelerating effect on cement hydration is excellent, but the viscosity of the composition becomes relatively high which makes use difficult
Solution Approach 1:
The patent changes the chemical composition parameters by replacing water-soluble calcium components (like calcium chloride or calcium nitrate) with water-insoluble calcium compounds (such as calcium carbonate, calcium oxide, or calcium hydroxide). This parameter change resolves the contradiction by eliminating the source of high viscosity while maintaining the calcium supply for C-S-H formation, thus preserving the accelerating effect without the viscosity penalty.
Solution Approach 2:
The patent employs readily available, inexpensive materials like calcium carbonate (limestone), calcium oxide (quicklime), or calcium hydroxide (slaked lime) as calcium sources. These materials are economically advantageous and environmentally friendly compared to water-soluble calcium salts, providing a cost-effective solution that avoids the viscosity problem while maintaining accelerator performance.
2Productivity
If calcium silicate hydrate nuclei are produced by reaction of water-soluble calcium component with water-soluble silicon component, then the accelerating effect on cement hydration is excellent, but foreign ions such as chloride and nitrate are introduced which are associated with use disadvantages
Solution Approach 1:
The patent extracts and removes harmful foreign ions (chloride, nitrate) from the system by replacing water-soluble calcium salts with water-insoluble calcium compounds. This extraction principle eliminates the source of corrosive ions while retaining the essential calcium component needed for C-S-H nucleus formation, thus resolving the contradiction between accelerating effect and corrosivity.
Solution Approach 2:
The patent converts potentially harmful water-soluble calcium salts into beneficial water-insoluble calcium compounds. By using materials like calcium carbonate, calcium oxide, or calcium hydroxide, the patent transforms what would be sources of corrosive ions into environmentally friendly, non-corrosive calcium sources that still effectively promote C-S-H formation and cement hydration acceleration.
3Productivity
If crystalline calcium silicate hydrate materials are used as accelerators, then the accelerating effect is achieved, but the compositions show increased viscosity resulting in problems during pumping or spraying
Solution Approach 1:
The patent changes the physical and chemical parameters of the calcium source by using water-insoluble compounds with controlled particle sizes and surface characteristics. This parameter change allows the calcium to be released gradually during cement hydration without creating high-viscosity solutions, thus maintaining pumpability and sprayability while achieving the desired accelerating effect.
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
The resulting composition effectively accelerates the curing of hydraulic and latent hydraulic binders, maintaining low viscosity and ease of handling even at elevated temperatures, thereby enhancing early strength development without the drawbacks of previous solutions.
Implementation Method 1
reacting a calcium hydroxide source with silicon dioxide under hydrothermal conditions
Implementation Method 2
addition of a water-soluble polymeric dispersant... to produce a semi-ordered calcium silicate hydrate with improved stability and pumpability
Data Source
AI summary
The present invention relates to a process for producing calcium silicate hydrate under hydrothermal conditions, wherein an organic compound is added in at least one of the process steps and wherein the organic compound has a molecular weight of 100 to 600 g/mol and from 0.02 to 0.035 functional groups per gram of the organic compound, wherein the functional groups being selected from —OH, —COOH, —COOMa, —SO3H or —SO3Ma, or —C(═O)H, wherein M is hydrogen, a mono-, di- or trivalent metal cation, ammonium ion or an organic amine radical and a is ⅓, ½ or 1. Further the invention is directed to the calcium silicate hydrate produceable according to the process of the present invention and its use as curing accelerator for hydraulic binders.