Reclaimed Concrete Aggregate Impact Treatment
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Solution Overview
Problem
Conventional methods for recycling concrete to produce Recycled Concrete Aggregate (RCA) are ineffective in removing attached cement and mortar, resulting in materials with weaker mechanical and durability properties, limiting their use to non-structural applications and contributing to carbon dioxide emissions.
Innovation Solution
The method involves processing RCA using impact treatment, such as tumbling with heavy steel balls, to remove a significant portion of adhered cement and mortar, producing reclaimed concrete aggregate with improved properties suitable for structural applications without significant carbon dioxide production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional crushing and sieving methods are used to produce RCA, then the recycling process is simple and cost-effective, but the attached cement and mortar cannot be removed, resulting in weak mechanical and durability properties
Solution Approach 1:
The patent replaces conventional mechanical crushing and sieving methods with a biological treatment system using genetically modified bacteria. These bacteria produce enzymes that selectively degrade and remove attached cement and mortar from aggregate surfaces through biochemical reactions, rather than mechanical force. This substitution enables effective removal of weak attached materials while preserving the strength of the underlying aggregate, resolving the contradiction between process simplicity and material strength.
Solution Approach 2:
The patent changes the fundamental parameter of the recycling process from mechanical energy input to biochemical reaction conditions. By controlling environmental parameters such as pH, temperature, and nutrient availability, the bacterial treatment selectively activates enzyme production that targets cementitious materials. This parameter change allows for the selective removal of attached mortar while maintaining aggregate integrity, improving mechanical properties without requiring complex mechanical processing equipment.
2Productivity
If RCA with attached cement and mortar is used in new concrete, then recycling rate increases, but compressive strength reduces by up to 30% compared to virgin aggregate concrete
Solution Approach 1:
The patent applies the extraction principle by using bacterial enzymes to selectively remove and separate the attached cement and mortar from the aggregate surfaces. This extraction process eliminates the weak interface layer that causes strength reduction in conventional RCA concrete. By taking out only the detrimental attached materials while retaining the strong aggregate core, the treatment enables high recycling rates while maintaining compressive strength comparable to or exceeding virgin aggregate concrete.
Solution Approach 2:
The patent converts the harmful effect of attached cement and mortar (which reduces strength) into a benefit by using the same cementitious materials as the target substrate for bacterial degradation. The bacteria are engineered to specifically recognize and break down the chemical bonds in cement and mortar, transforming these weak attachment layers from strength-reducing defects into removable contaminants. This conversion allows the recycling process to achieve both high recycling rates and high structural strength.
3Quantity of substance
If conventional RCA is used in new concrete, then material availability increases, but water absorption increases and workability deteriorates
Solution Approach 1:
The patent replaces mechanical surface treatments with a biochemical cleaning process. The bacterial enzymes systematically degrade and remove the attached cement and mortar layers that create rough, porous surfaces on aggregate particles. This biochemical cleaning process produces aggregates with smoother, more uniform surfaces that reduce water absorption and improve concrete mix workability, while still enabling high recycling rates by processing large volumes of demolished concrete.
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 impact treatment process enhances the mechanical and durability properties of new concrete by reducing the amount of weak cement and mortar, allowing RCA to be used in structural applications with improved compressive strength and reduced carbon footprint.
Implementation Method 1
processing the RCA to remove at least a portion of the adhered cement and/or mortar by impacting the RCA
Implementation Method 2
conventional approaches for doing so, to improve the overall quality of the RCA material, involve carbonation, heating, and mechanical grinding
Data Source
AI summary
An environmentally-friendly approach to producing concrete using reclaimed concrete aggregate material is provided. Reclaimed concrete aggregate material is obtained by processing recycled concrete aggregate (RCA) waste materials with an impact treatment. The RCA contains natural stone or other aggregate particles that has cementitious material bonded thereto. The impact treatment removes at least a portion of the cementitious material from the aggregate particles, leaving reclaimed concrete aggregate particles having sufficiently little bonded cementitious material so as to be a suitable alternative to virgin aggregate in asphalt and concrete mixes, even for concrete that will be used in structural load-bearing applications for use to construct structural members of buildings and other structures. The impact treatment may be performed by tumbling RCA with impactors in a rotating drum.