Old Concrete Processing via Low-Pressure Roller Milling
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Solution Overview
Problem
Recycled concrete aggregates have higher porosity and water absorption, leading to inferior concrete quality due to uncontrolled effective water content and altered processing properties compared to natural aggregates, resulting in worse curing behavior and strength.
Innovation Solution
A method and apparatus that grind old concrete at a pressure below 50 MPa using a roller mill to separate cement rock from aggregates without damaging the aggregates, controlling grinding pressure based on aggregate fracture strength and grain size distribution to produce high-quality aggregates for concrete production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If old concrete is crushed and classified into different grain sizes, then recycled aggregate can be produced, but the aggregate has higher porosity and water absorption leading to inferior concrete quality
Solution Approach 1:
The invention changes the grinding pressure parameter to less than 50 MPa, which is lower than conventional crushing methods. This parameter change allows selective comminution of cement rock while preserving aggregate integrity, thereby reducing porosity and water absorption of recycled aggregate while maintaining concrete quality
Solution Approach 2:
The invention extracts and removes the cement rock binding agent from the aggregate through selective comminution at low grinding pressure. By separating and removing the cement rock component, the method produces cleaner aggregate with better properties for concrete production
2Productivity
If grinding pressure is increased to improve comminution efficiency, then more cement rock is separated, but aggregate grains are damaged and grain shape is destroyed
Solution Approach 1:
The invention sets the grinding pressure parameter to less than 50 MPa, which is specifically low enough to comminute cement rock but high enough to maintain aggregate grain shape. This precise parameter control enables selective comminution without damaging the aggregate structure
Solution Approach 2:
The invention applies different treatment to different components based on their local properties. The low grinding pressure is specifically tailored to target the weaker cement rock binding agent while preserving the stronger aggregate grains, achieving selective comminution based on local material properties
3Adaptability or versatility
If recycled aggregate is used in concrete production, then natural aggregate demand is reduced, but water demand increases and curing behavior deteriorates
Solution Approach 1:
The invention changes the physical parameters of recycled aggregate by controlling grinding pressure to preserve grain shape and reduce porosity. This parameter control maintains aggregate properties closer to natural aggregate, thereby reducing water demand and improving curing behavior while still using recycled material
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 method improves the quality of recycled aggregates by maintaining the integrity of sand and gravel, allowing for targeted adjustment of water content and enhancing the processing properties and strength of the resulting concrete.
Implementation Method 1
grinding the old concrete in a grinding device and classifying the ground old concrete in a classifying device into at least two products of different grain fractions, wherein the grinding is effected at a grinding pressure of less than 50 MPa
Implementation Method 2
A shear stress generates friction on the grain surface and a targeted abrasion of the cement rock from the aggregate
Implementation Method 3
A shear stress generates friction on the grain surface and a targeted abrasion of the cement rock from the aggregate
Implementation Method 4
classifying the ground old concrete in a classifying device into at least two products of different grain fractions
Data Source
AI summary
The present disclosure relates to an apparatus and method for processing old concrete. The old concrete comprises cement rock and an aggregate, including sand and/or gravel. The method includes: grinding the old concrete in a grinding device; classifying the ground old concrete in a classifying device into at least two products of different grain fractions. The grinding is effected at a grinding pressure of less than 50 MPa. The apparatus includes a grinding device for grinding the old concrete, and a classifying device for classifying the ground old concrete into at least two products of different grain fractions. The grinding device is designed, and configured, in such a way that the grinding of the old concrete is effected at a grinding pressure of less than 50 MPa.