Carbonatable Cementitious Powder with Controlled Ca/Si Ratio
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Solution Overview
Problem
Existing methods for recycling fiber cement waste material into supplementary cementing materials face challenges in achieving consistent quality due to variations in composition and fiber content, leading to inconsistent compressive and flexural strengths in mortars.
Innovation Solution
A method involving the comminution and removal of organic fibers from fiber cement waste, followed by mixing waste materials with specific Ca/Si and SiO2 content ratios to achieve a predefined Ca/Si ratio in the cementitious powder, which is then carbonated to enhance its properties as a supplementary cementing material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fiber cement waste material is directly carbonated and used as supplementary cementing material, then the process is simple, but the composition variations lead to inconsistent quality and strength
Solution Approach 1:
The patent applies parameter changes by controlling the Ca/Si ratio of the cementitious powder within a specific range (0.8-1.5) before carbonation. This parameter control ensures that despite variations in raw fiber cement waste material, the final carbonated product achieves consistent quality and compressive strength when used as supplementary cementing material.
Solution Approach 2:
The patent implements preliminary action by adjusting the Ca/Si ratio of the fiber cement waste material before carbonation treatment. This pre-adjustment of compositional parameters ensures that the material is optimized for subsequent carbonation and achieves consistent performance as SCM, resolving the quality inconsistency issue before the actual cementitious application.
2Adaptability or versatility
If air-cured fiber cement waste material is used, then the material is readily available, but the resulting mortar strength is lower compared to autoclave-cured material
Solution Approach 1:
The patent uses parameter changes to adjust the Ca/Si ratio of air-cured fiber cement waste material to fall within the optimal range (0.8-1.5). This compositional adjustment compensates for the lower inherent strength of air-cured material compared to autoclave-cured material, enabling air-cured waste to achieve comparable mortar strength while maintaining broad material availability.
3Ease of manufacture
If the Ca/Si ratio is not controlled, then the processing is simpler, but the carbonated material does not achieve optimal pozzolanic properties and strength development
Solution Approach 1:
The patent implements parameter changes by precisely controlling the Ca/Si ratio within the range of 0.8-1.5 before carbonation. This controlled parameter ensures that the carbonated material develops consistent and optimal pozzolanic properties, reliably accelerating strength development in fresh cement when used as supplementary cementing material.
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 method produces a cementitious powder with consistent quality and improved compressive strength, capable of minimizing composition variations and enhancing the performance of mortars.
Implementation Method 1
comminuting fiber cement waste material
Implementation Method 2
a carbonation step is typically performed on such recycled concrete. This carbonation step transforms any calcium-silicate hydrates (also known as CSH) in cured cement into calcium carbonate and an alumino-silica gel
Data Source
Figure 1a~1b
Figure 2(a)~2(b)
AI summary
A method of generating a carbonatable cementitious powder with a predefined Ca/Si ratio, comprising the steps of: - comminuting fiber cement waste material; - removing organic fibers from said comminuted fiber cement waste material, to obtain a first waste powder, - comminuting a further waste material with a Ca/Si ratio of at most 0.6 and a SiO2 content of at least 50wt% as identified with XRF, therewith providing a second waste powder, and - mixing the first and the second waste powder.