Precipitated Calcium Carbonate Additive for Low-CO2 Blended Cement
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Solution Overview
Problem
Portland cement production contributes significantly to anthropogenic CO2 emissions, and conventional calcium carbonate additives, such as limestone, are used as fillers without reacting effectively, necessitating a more efficient and environmentally friendly alternative.
Innovation Solution
Incorporation of precipitated calcium carbonate, formed through mineral sequestration of CO2, with controlled morphology, size, and shape, to enhance its reactivity and reduce embodied CO2 emissions, utilizing silica for further enhancement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional limestone is used as a calcium carbonate additive in cement, then the environmental impact is reduced partially, but the reactivity and strength enhancement are insufficient
Solution Approach 1:
The patent applies parameter changes by transforming the physical and chemical parameters of calcium carbonate through controlled precipitation processes. This produces precipitated calcium carbonate (PCC) with specific particle size distributions, morphologies, and crystallinities that enhance reactivity with cement, thereby improving strength while maintaining CO2 reduction benefits
Solution Approach 2:
The patent creates a composite material system by combining precipitated calcium carbonate with cement matrix. The PCC particles are engineered to have specific surface areas and morphologies that facilitate interfacial bonding and chemical reactions, creating a composite structure that enhances overall cement strength beyond what conventional limestone can achieve
2Ease of manufacture
If conventional limestone is used as a filler in cement, then the production cost is reduced, but the embodied CO2 reduction is limited
Solution Approach 1:
The patent changes the production parameters of calcium carbonate by using controlled precipitation from aqueous solutions containing calcium ions and carbonate/bicarbonate ions. This process allows for the production of PCC with tailored properties that enhance cement performance, enabling higher replacement levels of clinker (up to 40% or more) and thus greater embodied CO2 reduction while maintaining cost-effectiveness
3Productivity
If the particle size of calcium carbonate is reduced to enhance reactivity, then the hydration is accelerated, but the manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-engineering the calcium carbonate particles through controlled precipitation before they are incorporated into cement. The precipitation process pre-establishes the desired particle size distribution, morphology, and crystallinity, eliminating the need for complex post-processing or specialized handling equipment in cement production
Solution Approach 2:
The patent employs self-service by using the calcium carbonate production process itself to generate particles with the desired reactive properties. The controlled precipitation conditions (pH, temperature, mixing rate, additive concentration) automatically produce PCC with optimal characteristics for cement reactivity, without requiring additional complex manufacturing steps
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 use of precipitated calcium carbonate increases cement strength and reduces CO2 emissions by up to 42%, while maintaining the high pH characteristic of cement, promoting the formation of scawtite and tilleyite, which are silica-rich calcium carbonate silicates, thereby enhancing the cement's binding capacity and accelerating hydration.
Implementation Method 1
a method of making reactive and amorphous calcium carbonate by capturing gaseous emissions from one or more cement plants and from said gaseous emissions converting carbon dioxide to carbonate and bicarbonate ions in aqueous solution and precipitating calcium, magnesium carbonates and carbonate hydrates
Implementation Method 2
converting carbon dioxide to carbonate and bicarbonate ions in aqueous solution and precipitating calcium, magnesium carbonates and carbonate hydrates
Implementation Method 3
a reaction between the cement and amorphous calcium carbonate resulting in the formation of calcium carbonate silicate (hydrates) including either or both of scawtite and tilleyite by a spontaneous and internal reaction
Implementation Method 4
a reaction occurring between the cement and the nano-crystalline calcium carbonate
Data Source
AI summary
The present invention relates to a cement additive for use in a blended cement composition, the additive comprising a precipitated calcium carbonate formed from mineral sequestration of carbon dioxide.