Sprayable Hydraulic Binder with C-S-H Accelerator
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Solution Overview
Problem
Conventional setting accelerators for shotcrete and cement-containing materials often result in either rapid setting with low early strength or slow setting with high early strength, and their performance varies with cement type, mix design, and temperature, making it difficult to achieve high early strength development required for modern tunneling projects.
Innovation Solution
A sprayable hydraulic binder composition is developed that includes a calcium silicate hydrate (C—S—H) containing component added before or at the spray nozzle, combined with an alkali-free or alkali-containing set accelerator, such as aluminum sulfate or sodium silicate, to enhance setting and early strength development.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional set accelerators are added to hydraulic binder compositions, then setting speed is improved, but early strength development deteriorates
Solution Approach 1:
The patent introduces calcium silicate hydrate (C-S-H) as an intermediary substance that mediates between the set accelerator and the hydraulic binder. The C-S-H component acts as a precursor that accelerates both setting and early strength development simultaneously, resolving the contradiction by providing a bridging mechanism that converts the harmful effect of rapid setting into beneficial early strength gain through controlled hydration reactions
Solution Approach 2:
The invention creates a composite accelerating system combining multiple components: calcium silicate hydrate (C-S-H), set accelerators (such as aluminum sulfate or calcium chloride), and hydraulic binder. This composite approach allows the different components to work synergistically, where C-S-H provides the structural framework for early strength while set accelerators control the setting rate, achieving both fast setting and high early strength together
2Loss of time
If set accelerators are added to achieve rapid setting, then setting time is improved, but early strength development becomes slow
Solution Approach 1:
The patent applies preliminary action by pre-forming calcium silicate hydrate (C-S-H) structures before the actual setting process. These pre-formed C-S-H nuclei are incorporated into the hydraulic binder mixture, providing ready-made crystalline frameworks that guide and accelerate the hydration process. This preliminary preparation ensures that when setting occurs rapidly, the strength development follows suit because the structural framework is already in place
Solution Approach 2:
The invention changes the chemical parameters of the accelerating system by introducing C-S-H containing components with specific calcium-to-silicon ratios and controlled particle sizes. By adjusting these parameters, the hydration reaction kinetics are optimized to achieve both rapid setting and concurrent early strength development, transforming the traditional parameter trade-off into a coordinated dual improvement
3Quantity of substance
If cement content is reduced to lower cost, then material cost is improved, but early strength development deteriorates
Solution Approach 1:
The patent extracts the essential strength-providing function from cement by isolating and utilizing calcium silicate hydrate (C-S-H) as a separate, pre-formed additive. Instead of relying solely on cement hydration to generate strength, the invention extracts and introduces ready-made C-S-H crystals that directly contribute to early strength development. This allows significant reduction in cement content while maintaining or even improving early strength performance
Solution Approach 2:
The invention changes the compositional parameters of the hydraulic binder system by incorporating C-S-H containing components at optimized dosages (typically 5-50% by weight of cement). This parameter change transforms the role of cement from the primary strength source to one component among several, allowing reduced cement content while the C-S-H additive compensates and enhances early strength development through its crystalline structure formation
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
This composition significantly accelerates the hardening process of hydraulic binders, improving early strength development while allowing for reduced cement content, maintaining or exceeding early strength performance across various cement types and conditions.
Implementation Method 1
By adding (1) a hardening accelerator consisting in calcium silicate hydrates and (2) a set accelerator the calcium silicate hydrate (C—S—H) precipitation can be strongly accelerated allowing faster development of the mechanical properties.
Implementation Method 2
It is known that set accelerators influence the hydration process of clinker phases such as C3A and C3S, the consumption of the sulfate carriers and the chemical composition of pore solution at the very beginning stage.
Data Source
AI summary
Process for the preparation of a sprayable hydraulic binder composition containing as main components water, aggregates, hydraulic binder, set accelerator, characterized in, that a calcium silicate hydrate (C—S—H) containing component is added before and/or at the spray nozzle.