Carbonated Calcium Hydroxide Compacts Strength via Cement Hydration
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Solution Overview
Problem
Calcium hydroxide releases a large amount of water during the carbonation process, preventing effective cementation between calcium carbonate grains and resulting in low strength of carbonated compacts.
Innovation Solution
A method involving the mixing of calcium hydroxide-rich materials with ordinary portland cement, magnesium hydroxide, pottery sand, and water in specific ratios, followed by compression, carbonation, and natural curing, which utilizes the synergy of cement hydration, magnesium hydroxide carbonation, and pottery sand's physical adsorption to consume water and enhance gelation and compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If calcium hydroxide undergoes carbonation reaction to absorb CO2 and form calcium carbonate, then CO2 consolidation and resource disposal are achieved, but a large amount of water is released resulting in low strength of carbonated compacts
Solution Approach 1:
The patent converts the harmful effect of water release during carbonation into a beneficial effect by using the released water to activate cement hydration and magnesium hydroxide carbonation reactions. The water that would otherwise weaken the compact structure is instead utilized to drive secondary reactions that produce binding agents (C-S-H gel, magnesium carbonate), transforming the weakness into a strength-enhancing mechanism.
Solution Approach 2:
The patent creates a composite material system combining calcium hydroxide-rich solid waste, ordinary portland cement, and magnesium hydroxide. This composite approach allows multiple mechanisms to work synergistically: calcium carbonate provides the primary carbonation product, cement hydration produces C-S-H gel for binding, and magnesium hydroxide carbonation contributes additional binding phases, collectively overcoming the strength limitation of pure calcium hydroxide carbonation.
2Productivity
If calcium hydroxide releases water during carbonation, then the carbonation reaction proceeds, but the water prevents effective cementation between calcium carbonate grains
Solution Approach 1:
The patent introduces cement and magnesium hydroxide as intermediary substances that mediate between the water release and the calcium carbonate grains. These intermediaries consume the released water through hydration and carbonation reactions, producing binding agents (C-S-H gel, magnesium carbonate) that act as intermediaries to cement the calcium carbonate grains together, thus resolving the conflict between reaction progress and grain bonding.
3Manufacturing precision
If wet grinding is used to refine particle size and increase reactivity, then carbonation reactivity improves, but the compressive strength remains low at only 15.3 MPa
Solution Approach 1:
The patent merges the wet grinding process with additional binding agents (cement and magnesium hydroxide). While wet grinding refines particle size for better reactivity, the combined system incorporates multiple binding mechanisms: C-S-H gel from cement hydration, magnesium carbonate from magnesium hydroxide carbonation, and calcium carbonate from calcium hydroxide carbonation. This merging of multiple binding sources overcomes the strength limitation that persists even with fine particle size optimization.
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
Significantly increases the compressive strength of carbonated calcium hydroxide compacts, improving mechanical properties of products like carbonated bricks and aerated concrete, from 15.3 MPa to up to 75 MPa at 7 days, while facilitating safe disposal of calcium hydroxide-rich solid waste.
Implementation Method 1
the C-S-H gelation effect produced by cement hydration
Implementation Method 2
the cementation effect produced by magnesium hydroxide carbonation
Implementation Method 3
the gas transmission channel and internal curing effect of the pottery sand
Implementation Method 4
the gas transmission channel and internal curing effect of the pottery sand
Implementation Method 5
the degree of carbonation
Data Source
AI summary
The present disclosure discloses a method and an article for improving the strength of carbonated calcium hydroxide compacts. The method includes the following steps: calcium hydroxide-rich materials, ordinary portland cement, magnesium hydroxide, pottery sand and water are mixed according to the mass ratio of 100:15-20:15-20:40-80:10-20, then the mixture was compressed, carbonated and naturally cured to obtain the carbonated compacts. The present disclosure utilizes cement hydration and magnesium hydroxide carbonation to consume the water produced by calcium hydroxide carbonation, the C-S-H gelation effect produced by cement hydration, the cementation effect of magnesium hydroxide carbonation products, the volume expansion effect of magnesium hydroxide carbonation and the gas transmission channel and internal curing effect of pottery sand further improve the carbonation degree, product gelation, thus greatly improving the strength of carbonated calcium hydroxide compacts.