Flowable Concrete Secondary Accelerator System
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Solution Overview
Problem
Existing flowable concrete and mortar technologies face challenges in achieving fast setting and early strength development, particularly when used in applications like tunneling, where alkali carbonates decompose when added to weakly acidic alkali-free accelerators, leading to precipitation issues.
Innovation Solution
A two-component system comprising a concrete mixture with alkali carbonate as a secondary accelerator and a retarder, combined with a main accelerator, which prevents premature activation of the carbonate, allowing for controlled setting and early strength development without modifying existing spray equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If alkali carbonate is added to accelerate setting and strength development, then early strength is improved, but decomposition occurs in weakly acidic environments causing precipitation
Solution Approach 1:
A pH buffer system comprising phosphoric acid and phosphates is introduced as an intermediary to control the chemical environment. This buffer maintains pH within 6-8, preventing the weakly acidic conditions that cause carbonate decomposition while allowing the carbonate to function as an effective accelerator. The buffer acts as a mediator between the accelerator and the cementitious materials, ensuring chemical stability.
Solution Approach 2:
The patent changes the pH parameter control strategy by introducing a buffering system. Instead of allowing pH to drop into the weakly acidic range (which causes carbonate decomposition), the buffer maintains pH within the 6-8 range. This parameter control enables the alkali carbonate to remain stable and effective throughout the acceleration process.
2Speed
If main accelerator is added immediately before application, then fast setting is achieved, but equipment modification is required
Solution Approach 1:
The patent merges the accelerator and retarder components into a single pre-mixed composition that can be stored and applied using existing equipment. This unified composition eliminates the need for separate storage and dosing systems for multiple components, maintaining simplicity while achieving controlled fast setting through the synergistic interaction of the accelerator and pH buffer.
3Duration of action of moving object
If retarder is used to maintain flowability, then workability time is extended, but setting speed is reduced
Solution Approach 1:
The patent implements a staged acceleration mechanism where the pH buffer and alkali carbonate create an initial controlled setting phase that maintains flowability, followed by a secondary acceleration phase. The buffer initially controls the reaction rate to preserve workability, then as pH stabilizes, the carbonate accelerator becomes more effective, creating a periodic action pattern that achieves both extended flowability and ultimately fast setting.
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 solution enables rapid setting and high early strength development, achieving compressive strengths of 1 MPa or higher within one hour, suitable for tunneling applications, while maintaining flowability and preventing decomposition, thus enhancing the performance of sprayable concrete and backfill grouts.
Implementation Method 1
alkali carbonate serves as a secondary accelerator... enables rapid setting and high early strength development
Implementation Method 2
The retarder serves to maintain flowability of the concrete or mortar mixture before combination with the main accelerator
Implementation Method 3
combining the concrete mixture and accelerator component to initiate curing of the concrete composition
Data Source
AI summary
A concrete, mortar or grout formulation comprises two separate components: a concrete admixture comprising: (a) a concrete mixture; (b) alkali carbonate; (c) aretarder; and (d) water, an accelerator mixture comprising: (a) anaccelerator component; and (b) water.