Cement Board Lightweight Core Binder Composition
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional cement board production methods, especially continuous processes, face challenges with thaumasite formation due to gypsum-cement reactions, leading to expansion and deterioration, and require improved compositions with faster setting times and better moisture management.
Innovation Solution
A cement board with a lightweight core, comprising 20-90% of a reactive binder mixture of 15-25% hydraulic cement, 50-65% calcium sulphate hemihydrate, and 10-35% pozzolanic material, which prevents thaumasite formation and offers improved water resistance and workability, along with a glass fibre-based covering layer for enhanced strength and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If gypsum (calcium sulphate dihydrate) is combined with cement to decrease setting time, then setting time is reduced, but thaumasite formation occurs causing expansion and deterioration
Solution Approach 1:
The patent converts the harmful effect of gypsum-cement reactions into a beneficial one by using calcium sulphate hemihydrate (plaster) instead of dihydrate (gypsum). The hemihydrate form reacts with cement to accelerate setting time while the pozzolanic material prevents thaumasite formation, transforming a potentially harmful reaction into a controlled beneficial process that improves both setting time and board stability
Solution Approach 2:
The patent introduces pozzolanic material as an intermediary substance that mediates between the calcium sulphate hemihydrate and cement components. This intermediary prevents the formation of thaumasite crystals while allowing the beneficial setting acceleration effect to occur, thus protecting the board matrix from deterioration while maintaining improved setting characteristics
2Object-affected harmful factors
If hydraulic cement content is reduced to lower carbon footprint, then environmental sustainability improves, but water resistance may deteriorate
Solution Approach 1:
The patent creates a composite binder system combining calcium sulphate hemihydrate, pozzolanic material, and reduced amounts of hydraulic cement. This composite approach allows the system to achieve both low carbon footprint (through reduced cement content) and maintained water resistance (through the synergistic action of hemihydrate and pozzolanic material components)
Solution Approach 2:
The patent changes the chemical composition parameters of the binder mixture by optimizing the ratios of hydraulic cement, calcium sulphate hemihydrate, and pozzolanic material. This parameter optimization enables the system to reduce cement content for environmental benefits while maintaining adequate water resistance through the adjusted composition balance
3Speed
If calcium sulphate hemihydrate content is increased to accelerate setting time, then setting speed improves, but thaumasite formation increases causing deterioration
Solution Approach 1:
The patent introduces pozzolanic material as an intermediary that selectively interacts with the calcium sulphate hemihydrate-cement system. This intermediary prevents thaumasite crystal formation while allowing the setting acceleration effect of the hemihydrate to proceed, thus decoupling the beneficial speed improvement from the harmful deterioration effect
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 composition provides cement boards with reduced hydraulic cement content, improved moisture management, and a lower carbon footprint, while preventing thaumasite formation and maintaining mechanical properties, suitable for continuous manufacturing processes.
Implementation Method 1
The addition of calcium sulphate hemihydrate in the aqueous cementitious composition accelerates the setting time of the Portland cement board
Implementation Method 2
The use of pozzolanic materials, such as silica fume, in gypsum-cement compositions is known to prevent the formation of thaumasite
Implementation Method 3
the relatively low content of hydraulic cement results in an increased permeability of the board leading to better moisture management
Data Source
AI summary
A cement board includes a lightweight core between a first covering layer and a second covering layer, wherein the lightweight core results from the curing of an aqueous cementitious composition including, based on the total dry matter, 20 to 90 wt % of a reactive binder mixture and 10 to 80 wt % of fillers, wherein the reactive binder mixture includes, based on the total dry matter of the reactive binder mixture: 15 to 25 wt % hydraulic cement, 50 to 65 wt % calcium sulphate hemihydrate, and 10 to 35 wt % pozzolanic material; and at least one of the first and second covering layers includes a glass fibre-based sheeting, the sheeting being fully or partially embedded in a cementitious matrix.