C-S-H Seed Admixture for Rapid Cement Hardening
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Solution Overview
Problem
Current hardening accelerators for cement mixes, such as those based on Portland cement, face limitations in promoting rapid mechanical strength development, especially in cold climates, and are not effective with supplementary cementitious materials like fly ash and blast furnace slag, leading to delays in construction processes and potential concrete degradation.
Innovation Solution
A novel admixture using calcium silicate hydrate (C-S-H) seeds in aqueous suspension, produced by hydrating Portland cement or other siliceous binders in the presence of carboxylic acids or their calcium salts, which enhances mechanical strength development without introducing alkalis or nitrates, and can activate supplementary cementitious materials, eliminating the need for grinding and reducing energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional hardening accelerators (chlorides, nitrates, calcium formate) are used to increase mechanical strength at short curing times, then the hardening speed is improved, but either corrosion of reinforcing bars occurs or the material must be used in powder form due to low solubility
Solution Approach 1:
The patent introduces C-S-H seeds as an intermediary substance that mediates the hardening process. These seeds are formed by hydrating Portland cement in the presence of carboxylic acids or their calcium salts, and they act as a catalyst to accelerate the hardening of both Portland cement and supplementary cementitious materials without causing corrosion to reinforcing bars, thus resolving the contradiction between hardening speed and corrosion resistance
Solution Approach 2:
The patent changes the chemical parameters of the accelerating admixture by using carboxylic acids or their calcium salts during the hydration process. This parameter change results in the formation of C-S-H seeds with specific surface area and composition that provide acceleration without the harmful effects of traditional accelerators like chlorides and nitrates
2Quantity of substance
If supplementary cementitious materials (fly ash, blast furnace slag) are used to reduce Portland cement consumption, then the sustainability is improved, but the mechanical strength development is delayed
Solution Approach 1:
The patent applies preliminary action by pre-forming C-S-H seeds through the hydration of Portland cement in the presence of carboxylic acids or their calcium salts before adding supplementary cementitious materials. These pre-formed seeds then serve as nucleation sites that accelerate the hardening of fly ash and blast furnace slag, enabling early strength development even with high proportions of supplementary materials
Solution Approach 2:
The C-S-H seeds act as an intermediary that bridges Portland cement and supplementary cementitious materials. The seeds provide a reactive surface that facilitates the hardening of supplementary materials, allowing them to contribute to early strength development rather than merely filling the matrix passively
3Speed
If grinding is performed to enhance the effectiveness of admixtures, then the acceleration effect is improved, but the energy consumption increases
Solution Approach 1:
The patent applies self-service by utilizing the natural hydration process of Portland cement to form C-S-H seeds without requiring external energy input from grinding. The carboxylic acids or their calcium salts facilitate the in-situ formation of these seeds during mixing, allowing the system to serve itself by converting the hydration exotherm and chemical energy into the desired acceleration effect without mechanical energy consumption
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 admixture significantly accelerates mechanical strength development at short curing times, allows for higher substitution of Portland cement with supplementary materials, and prevents concrete degradation, while maintaining long-term strength and stability.
Implementation Method 1
The action mechanism of the accelerators described above is not yet fully understood, but said compounds are believed to accelerate the C3S hydration reaction by means of surface adsorption processes
Implementation Method 2
acts as a crystallisation seed for the C-S-H product by hydration of the C3S of the cement, accelerating its nucleation and precipitation
Implementation Method 3
modification of the microstructure of the hydrated phases
Implementation Method 4
acts as a crystallisation seed for the C-S-H product by hydration of the C3S of the cement, accelerating its nucleation and precipitation
Data Source
Figure 1~2
Figure 3
AI summary
The object of the present invention is a novel admixture comprising a hardening accelerator for hydraulic compositions based on Portland cement and other supplementary cementitious materials.