Carbonated Recycled Concrete Aggregate for ASR Expansion Control

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Solution Overview

Problem

Recycled concrete aggregate (RCA) produced from structures affected by alkali-silica reaction (ASR) can induce expansion and damage in new concrete, despite preventive measures, due to the presence of reactive silica and alkalis, posing a challenge in recycling such aggregates.

Innovation Solution

Carbonating the RCA with carbon dioxide prior to its use in new concrete to mitigate the alkali-silica reaction by forming CaCO3, reducing water absorption, and improving the microstructure of the aggregates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If recycled concrete aggregate is used in new concrete, then sustainability and resource efficiency are improved, but expansion and damage occur due to alkali-silica reaction

Engineering Contradiction:

ImprovesustainabilityVSAvoidstructural integrity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies preliminary carbonation treatment to the recycled concrete aggregate before it is used in new concrete. This pre-treatment converts reactive silica and alkalis in the RCA into stable calcium carbonate, preventing future alkali-silica reactions and expansion damage while maintaining the sustainability benefits of using recycled materials.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the harmful reactive components (silica and alkalis) in the recycled concrete aggregate into beneficial stable calcium carbonate through carbonation. The previously harmful ASR-reactive materials become stable, non-reactive components that improve the durability of the new concrete while maintaining resource efficiency.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Reliability

If preventive measures are implemented to control ASR in RCA, then some expansion is reduced, but damage still occurs due to presence of reactive silica and alkalis

Engineering Contradiction:

Improveexpansion controlVSAvoidreactivity of RCA

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful reactive silica and alkalis in the RCA into beneficial stable calcium carbonate through carbonation. This fundamental chemical transformation eliminates the reactivity problem at its source rather than merely controlling symptoms, completely preventing ASR expansion damage.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the chemical composition parameters of the RCA by introducing carbon dioxide to react with calcium hydroxide and form calcium carbonate. This parameter change (chemical composition transformation) fundamentally alters the reactivity characteristics of the aggregate, converting it from reactive to stable.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If carbonation treatment is applied to RCA, then reactivity is reduced and expansion is minimized, but additional processing steps are required

Engineering Contradiction:

Improvereactivity reductionVSAvoidcarbonation process

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent utilizes carbon dioxide from flue gas emissions (a waste stream) to carbonate the RCA. This self-service approach uses available industrial emissions to perform the carbonation treatment, reducing the need for external carbonation equipment and making the process more economically viable while maintaining effective reactivity reduction.

Inventive Principle:

Principle #25Self-service

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 carbonation process reduces the reactivity of RCA, minimizing expansion and enhancing the mechanical properties of concrete produced with these aggregates, thereby preventing damage and improving sustainability.

Implementation Method 1

Carbonating the RCA with carbon dioxide prior to its use in new concrete to mitigate the alkali-silica reaction by forming CaCO3

Methodology Applied

Scientific EffectCarbonation reaction: Chemical Bonding

Implementation Method 2

the water comprises carbonated water, such as carbonated water that comprises carbonated wash water

Methodology Applied

Scientific EffectGas absorption: Absorption (physical)

Data Source

PatentUS12497329B2Carbonation of concrete aggregates

Publication Date: 2025.12.16 CARBONCURE TECHNOLOGIES INC

AI summary

Provided herein are methods and compositions for carbonation of recycled concrete aggregates (RCA) to produce carbonated RCA. In addition, uses of the carbonated RCA, such as in building materials, and building materials containing RCA, are included. Carbonation of RCA may be used alone or may be used in combination with other carbonation processes associated with concrete manufacture, such as carbonation of wet concrete mixes and/or carbonation of concrete wash water.