Shotcrete Composition Using Magnesium Salt Accelerator
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional shotcrete compositions take too long to harden, leading to delays in mining operations and pose health risks due to toxic aluminum-based accelerators used in poorly ventilated environments, while also compromising pumpability and applicability.
Innovation Solution
A cementitious composition comprising 15-90% cementitious binder, 0.02-3% ettringite formation controller (glyoxylic acid condensate or adduct), 0.15-10% magnesium salt accelerator, and 0.02-2% polyhydroxy compound, which delays ettringite formation to improve workability and reduce toxicity, allowing for faster hardening and safer use in challenging conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional shotcrete composition is used, then the composition can be applied via nozzle, but it takes several days to attain most of its strength, causing significant delay in mining operations
Solution Approach 1:
The patent changes the chemical parameters of the shotcrete composition by using magnesium salt accelerator instead of conventional aluminum-based accelerators, and by controlling ettringite formation through glyoxylic acid condensate or adduct. This chemical parameter change enables the composition to develop high early compressive strength within hours rather than several days, significantly reducing hardening time while maintaining strength development.
Solution Approach 2:
The patent creates a composite cementitious composition combining cementitious binder with specific additives including ettringite formation controller (glyoxylic acid condensate or adduct) and magnesium salt accelerator. This composite material formulation achieves both fast hardening and high early strength development, resolving the contradiction between strength gain and time consumption.
2Productivity
If aluminum-based accelerators are used to speed up hardening, then early strength development is improved, but health risks increase due to toxicity in poorly ventilated environments
Solution Approach 1:
The patent extracts and removes the harmful aluminum-based accelerator component from the shotcrete composition and replaces it with non-toxic magnesium salt accelerator. This extraction eliminates the health risks associated with aluminum sulfate or aluminum chloride while preserving the accelerated hardening function, allowing high productivity without worker health compromise in poorly ventilated mining environments.
Solution Approach 2:
The patent converts the potentially harmful rapid hardening requirement into a benefit by using magnesium salt accelerator that provides both fast hardening and non-toxicity. The magnesium salt serves as a beneficial alternative that achieves the desired productivity improvement without introducing harmful factors, turning the challenge of rapid hardening into an opportunity for safer operations.
3Loss of time
If cementitious composition is optimized for high early strength, then hardening time is reduced, but pumpability and applicability via nozzle are compromised
Solution Approach 1:
The patent applies partial action by using controlled amounts of ettringite formation controller (0.02-3% by weight) and magnesium salt accelerator (0.15-10% by weight). This controlled, partial addition achieves sufficient early strength development and reduced hardening time without excessive acceleration that would compromise pumpability. The moderate dosage levels maintain workability while achieving the desired hardening speed improvement.
Solution Approach 2:
The patent changes the chemical composition parameters by introducing ettringite formation controller and magnesium salt accelerator in specific proportions. These parameter changes optimize the balance between early strength development and pumpability, allowing the composition to maintain adequate workability for nozzle application while achieving fast hardening and high early strength within hours.
4Adaptability or versatility
If conventional shotcrete is used in cold conditions, then applicability is limited, but modifying composition for cold weather reduces early strength development
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating magnesium salt accelerator and ettringite formation controller, which remain effective in colder temperatures. These compositional parameter changes enable the shotcrete to maintain high early compressive strength development even in cold conditions, achieving both improved adaptability to various temperatures and preserved early strength gain that conventional compositions cannot achieve in cold weather.
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 achieves high early compressive strength within hours, enhances pumpability, and reduces health risks by using non-toxic magnesium salts, enabling faster mining operations and broader application in various conditions, including colder temperatures and poorly ventilated environments.
Implementation Method 1
Conventional shotcrete can set in only a few minutes, but it is relatively slow to harden, taking several days to attain most of its strength
Implementation Method 2
0.02-3% by weight of an ettringite formation controller comprising (i) a glyoxylic acid condensate and/or a glyoxylic acid adduct
Data Source
AI summary
The present application relates to a cementitious composition suitable to be applied to an object via a nozzle. The composition comprises a) 15-90% by weight of a cementitious binder, b) 0.02-3% by weight of an ettringite formation controller, c) 0.15-10% by weight of a magnesium salt accelerator and d) 0.02-2% by weight of a polyhydroxy compound A, and/or salts or esters thereof, wherein the polyhydroxy compound A is selected from polyalcohols with a carbon to oxygen ratio of C/O≥1 and mixtures 0 thereof, based on the total dry weight of the composition. Further a process for applying the composition onto a surface and a hardened structure obtained by the process is disclosed.