Low Density Fiber Cement Panels with Uniform Air Voids
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Developing low-density fiber cement building products with consistent and evenly distributed air voids is challenging due to the harsh processing conditions of the Hatschek process, which often results in air void loss and inconsistent air content in fiber-reinforced cement sheets and panels.
Innovation Solution
The use of air entrainment agents, such as sodium vinsol resin, and sacrificial fillers like ammonium carbonate, integrated into the fiber cement formulation to create uniformly distributed air voids within the matrix, ensuring air voids are greater than 3% of the volume and have an average diameter between 20 to 100 microns, while maintaining mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If conventional air entrainment techniques are used to reduce density, then the density of fiber cement panels is reduced, but the air void content and distribution become inconsistent and unpredictable
Solution Approach 1:
Air voids are introduced into the fiber cement slurry before the Hatschek manufacturing process begins. The air is entrained in the slurry mixture prior to layering and pressing, allowing the air voids to be distributed uniformly throughout the final product while withstanding the subsequent processing forces
Solution Approach 2:
The patent controls the size, distribution, and volume of air voids by adjusting parameters such as air void diameter (20-100 microns), cumulative volume (>3% of matrix volume), and spatial distribution throughout the fiber cement matrix. These parameter controls ensure consistent air void characteristics while achieving the desired density reduction
2Weight of moving object
If low density additives are used to reduce density, then the weight of fiber cement products is reduced, but the additives cannot withstand the high pressure and mechanical forces of the Hatschek process
Solution Approach 1:
Instead of using solid low-density additives, the patent employs air (a gas) as the low-density component. Air voids are entrained in the slurry and can withstand the Hatschek process pressures and mechanical forces, providing reliable density reduction without the reliability issues of solid additives
Solution Approach 2:
The fiber cement product is designed with a porous structure containing uniformly distributed air voids throughout the matrix. This porous structure achieves the desired low density while maintaining the structural integrity and reliability needed to withstand processing and service conditions
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 approach allows for the production of low-density fiber cement products with consistent air void distribution and reduced density, achieving densities between 1.0 to 1.3 g/cc, while maintaining or improving mechanical properties like Modulus of Rupture and durability, and offering cost-effective density modification.
Implementation Method 1
air entrainment agents, such as sodium vinsol resin
Implementation Method 2
creating air bubbles in a aqueous fiber cement slurry
Implementation Method 3
sacrificial fillers like ammonium carbonate
Implementation Method 4
each of the overlaying fiber cement substrate layer is bonded to an adjacent overlaying substrate layer thereby forming a fiber cement matrix
Data Source
AI summary
Disclosed herein are low density fiber cement articles, such as fiber cement building panels and sheets, comprised of multiple overlaying fiber cement substrate layers having small and uniform entrained air pockets and low density fillers distributed throughout. The combination of entrained air pockets and low density fillers provide a low density fiber cement matrix with physical and mechanical properties similar to comparable low density fiber cement matrix without entrained air pockets.