Concrete Curing via Multi-Stage Electromagnetic Heating
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Solution Overview
Problem
Existing concrete curing methods, particularly those using electromagnetic radiation, often compromise the structural strength of the cured concrete or require excessively long curing times, with inadequate control over temperature gradients and penetration depths.
Innovation Solution
A multi-step process involving inductive alternating magnetic fields, high-frequency radio emissions, and microwave radiation, applied in sequence and potentially in a vacuum environment, to accelerate curing and drying of concrete while maintaining structural integrity, using specific frequency ranges and durations to optimize heating and minimize shrinkage cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If electromagnetic radiation is applied to accelerate concrete curing, then curing time is reduced, but structural strength of the cured concrete is compromised
Solution Approach 1:
The patent divides the curing process into multiple sequential stages using different electromagnetic radiation frequencies: (1) Initial stage with frequencies of 5-35 MHz for deep penetration and uniform heating, (2) Intermediate stage with microwave frequencies for accelerated heating, and (3) Final stage with controlled drying. This segmentation allows each frequency range to address specific curing needs without compromising overall structural strength.
Solution Approach 2:
The patent systematically varies electromagnetic radiation parameters including frequency (from 5-35 MHz down to microwave ranges), power levels, and exposure duration across different curing stages. By dynamically adjusting these parameters, the process achieves both rapid curing and preservation of concrete's structural integrity through controlled thermal profiles.
2Temperature
If high-frequency radio emission is applied for dielectric heating, then temperature increases and curing accelerates, but reinforcement bars act as antennas causing inefficient energy distribution
Solution Approach 1:
The patent separates the heating process into distinct frequency stages: first using 5-35 MHz radiation for uniform deep penetration heating before reinforcements become significant antennas, then transitioning to microwave frequencies where reinforcement antenna effects are managed. This temporal segmentation optimizes energy efficiency at each stage.
Solution Approach 2:
The patent applies lower frequency electromagnetic radiation (5-35 MHz) in the initial curing stage to establish uniform temperature distribution throughout the concrete mass before higher frequency microwaves are introduced. This preliminary action prevents reinforcement bars from immediately acting as inefficient antennas and ensures more effective subsequent heating.
3Strength
If conventional natural atmospheric curing is used, then concrete strength is maintained, but curing time extends to several weeks
Solution Approach 1:
The patent transforms the curing process from passive natural atmospheric conditions to active controlled electromagnetic heating by varying frequency, power, and duration parameters. This enables compression of the curing timeline from weeks to hours or days while maintaining strength development through scientifically controlled thermal profiles.
Solution Approach 2:
The patent employs periodic cyclic heating and cooling phases during electromagnetic curing, alternating between high-power heating intervals and controlled cooling periods. This periodic action mimics and accelerates the natural curing rhythm while dramatically reducing total time required to achieve target strength levels.
4Volume of stationary object
If microwave radiation is applied for direct dielectric heating, then penetration depth increases, but temperature distribution becomes less uniform compared to surface heating
Solution Approach 1:
The patent segments the heating process into two distinct phases: first using 5-35 MHz electromagnetic radiation for uniform deep penetration heating throughout the concrete volume, then applying microwave radiation for accelerated surface and near-surface heating. This segmentation allows each frequency range to optimize its strengths while compensating for weaknesses through sequential application.
Solution Approach 2:
The patent applies different electromagnetic frequencies to different regions and stages of the curing process: lower frequencies (5-35 MHz) for deep volumetric heating, and higher microwave frequencies for surface and intermediate zone heating. This spatial and temporal differentiation of heating quality achieves both deep penetration and uniform temperature distribution.
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
This method significantly reduces curing time without weakening the concrete's structural strength, achieving uniform heating and minimizing shrinkage-related cracks through controlled gas bubble formation and temperature distribution, thereby enhancing the concrete's properties.
Implementation Method 1
The hydration process is exothermic and the hardening of the concrete depends on its temperature. Curing can be accelerated by supplying additional heat, usually by steam, heating coils or electrically heated forms or pads. Heating can also be achieved by applying different forms of electromagnetic radiation. At the shortest wavelengths, the concrete or an enclosing form is illuminated by infrared radiation, where the heat reaches the interior of the cast element through conduction from the surface. Microwave radiation can also be applied in the curing process, see U.S. patent no. 4,338,135 and US patent no. 5,245,149 for related examples. The temperature is then increased through direct dielectric heating of the concrete.
Implementation Method 2
For the case of concrete with electrically conducting metal reinforcements, these will act as antennas when the element is subjected to high-frequency radio emission. Eddy currents will form in the reinforcements, thereby heating the concrete element from within. This electromagnetic inductive heating is the most efficient if the reinforcements are ferromagnetic, which is the case for the more commonly used reinforcement steels. Alternating magnetic fields can also be applied to induce eddy currents in the reinforcements.
Implementation Method 3
Any of the steps can take place in a low-pressure or vacuum environment, which removes air from the cast concrete and accelerates the drying. Vacuum drying where a product is subjected to dielectric heating is a known technique. As an example of a general application see U.S. patent no. 5,575,083. The vacuum lowers the boiling temperature, while the electromagnetic field increases the temperature, resulting in a more efficient drying.
Data Source
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AI summary
A method for accelerating the curing of concrete is disclosed. The wet concrete is subjected to heating by applying electromagnetic radiation during a short period in the range of seconds up to a few minutes, thereby increasing the temperature of said concrete from an initial first temperature within the range of 10 to 25 degrees C to a second temperature within the range of 50 to 80 degrees C.