Backfilling Paste Flow via Calcium Hydroxide Mediation
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Solution Overview
Problem
The production of backfilling pastes for underground operations often faces issues with clogging and inadequate flow due to interactions between tailings and superplasticizers like polycarboxylate esters, especially when dealing with phyllosilicate-containing materials, which complicates the efficient backfilling process.
Innovation Solution
Incorporating calcium hydroxide with polycarboxylate ether into the mixing process of cement and tailings to enhance the flow characteristics of backfilling pastes, specifically increasing the slump flow, by adjusting the composition and order of addition of components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If polycarboxylate esters (superplasticizers) are used to improve paste flow, then flow characteristics should improve, but tailings containing phyllosilicates interact unfavourably with the superplasticizer causing clogging and reduced flow
Solution Approach 1:
Calcium hydroxide acts as an intermediary substance that mediates between the polycarboxylate ester superplasticizer and the phyllosilicate-containing tailings. The calcium hydroxide first reacts with the phyllosilicates to form calcium silicate hydrate products that have reduced surface activity, thereby preventing the harmful interaction between the superplasticizer and tailings minerals. This intermediary reaction eliminates the adsorption of polycarboxylate esters on phyllosilicate surfaces, maintaining paste flow consistency and preventing clogging.
2Ease of operation
If more water is added to improve paste flow, then flow characteristics improve, but the paste becomes too fluid and loses stability during pumping and placement
Solution Approach 1:
The invention changes the chemical composition parameters of the paste by introducing calcium hydroxide, which chemically reacts with phyllosilicates to form calcium silicate hydrate products. This parameter change modifies the surface chemistry of the tailings particles, reducing their ability to adsorb superplasticizers and altering the paste rheology. The result is improved flow characteristics without requiring additional water, thereby maintaining paste stability during pumping and placement.
3Strength
If polycarboxylate esters are used to reduce water content in paste, then paste strength improves, but flow characteristics deteriorate due to interaction with phyllosilicates
Solution Approach 1:
The calcium hydroxide is added to the paste mixture before the polycarboxylate ester superplasticizer, performing a preliminary chemical action. The calcium hydroxide first reacts with the phyllosilicate minerals in the tailings to form calcium silicate hydrate products, modifying the mineral surfaces. Only after this preliminary modification is the superplasticizer added, ensuring it remains available to provide water reduction and strength enhancement without being adsorbed by the phyllosilicates, thereby maintaining both flow characteristics and paste strength.
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 calcium hydroxide with polycarboxylate ether significantly improves the flow of backfilling pastes, particularly those containing phyllosilicates, ensuring smoother pumping and curing, thus addressing the clogging and flow issues in underground operations.
Implementation Method 1
the use of calcium hydroxide together with at least one polycarboxylate ether has in particular the advantage that the flow (measurable for example as the slump flow) of a backfilling paste thus obtained is increased as compared to the flow of the same backfilling paste comprising the same polycarboxylate ether but no calcium hydroxide. This is especially the case for backfilling pastes comprising tailings from underground operations which comprise phyllosilicates.
Data Source
AI summary
A process for the production of backfilling pastes for underground operations, the process including or essentially consisting of the mixing of a) cement, b) tailings from underground operations, c) optionally extra water, d) at least one polycarboxylate ether, and e) calcium hydroxide; and a method for controlling the flow of a backfilling paste for underground operations, the method including at least one step of admixing an admixture including at least one polycarboxylate ether and calcium hydroxide to a mixture of cement, tailings, and water.