Processing High Calcium Fly Ash for Concrete

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Solution Overview

Problem

The use of high calcium fly ash in concrete is challenging due to its high hydraulic reactivity, leading to unpredictable set times and increased risk of alkali-silica reactions and sulfate attacks, which complicates construction schedules and concrete quality.

Innovation Solution

A method involving the hydration and carbonation of high calcium fly ash to neutralize its cementitious reactivity, followed by grinding to expose pozzolanic sites, resulting in a processed fly ash that can replace up to 60% of cement in concrete mixes, reducing set time risks and enhancing performance while maintaining pozzolanic reactivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If high calcium fly ash is used in concrete, then cementitious reactivity is improved, but set time becomes unpredictable and alkali-silica reaction risk increases

Engineering Contradiction:

Improvecementitious reactivityVSAvoidset time predictability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent applies preliminary action by pre-hydrating the high calcium fly ash in a controlled environment before incorporating it into concrete. This pre-hydration process activates the pozzolanic material and stabilizes the calcium content, ensuring predictable set times and reliable performance when the processed fly ash is later used in concrete mixes.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent utilizes parameter changes by modifying the chemical and physical properties of high calcium fly ash through controlled hydration and carbonation processes. These parameter changes transform the fly ash from an unpredictable, highly reactive material into a stabilized, processed material with consistent pozzolanic activity and reduced alkali-silica reaction potential.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If high calcium fly ash is used in concrete, then cement replacement is achieved, but risk of sulfate attack and alkali-silica reaction increases

Engineering Contradiction:

Improvecement replacementVSAvoidalkali-silica reaction risk

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent applies the blessing in disguise principle by converting the harmful high reactivity and instability of high calcium fly ash into beneficial properties through controlled processing. The same high calcium content that causes unpredictable behavior is transformed through hydration and carbonation into a stable, processed material that maintains pozzolanic reactivity while eliminating alkali-silica reaction risks and sulfate attack vulnerabilities.

Inventive Principle:

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

3Reliability

If high calcium fly ash is processed through hydration and carbonation, then cementitious reactivity is neutralized, but pozzolanic reactivity is maintained

Engineering Contradiction:

Improvereactivity predictabilityVSAvoidpozzolanic reactivity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies segmentation by separating the two reactivity aspects of high calcium fly ash - cementitious reactivity and pozzolanic reactivity - through controlled processing. The hydration and carbonation processes selectively neutralize the harmful cementitious reactivity while preserving the beneficial pozzolanic reactivity, allowing independent control of each property.

Inventive Principle:

Principle #1Segmentation

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 processed high calcium fly ash reduces the risk of alkali-silica reactions and sulfate attacks, maintains compressive strength, and decreases the amount of CO2 and energy embodied in concrete, while regulating set times and sulfate content, thus improving concrete performance and sustainability.

Implementation Method 1

The processing of the high calcium fly ash includes hydrating and carbonating the high calcium fly ash

Methodology Applied

Scientific EffectHydration: Mineral Hydration

Implementation Method 2

The processing of the high calcium fly ash includes hydrating and carbonating the high calcium fly ash

Methodology Applied

Scientific EffectCarbonation:

Data Source

PatentUS10611684B2Recovery and beneficiation of pozzolan deposits for enhanced performance in concrete

Publication Date: 2020.04.07 EM RESOURCES LLC

AI summary

Disclosed is a method for enhancing the performance of concrete includes, providing a cementitious mixture comprising cement and processed high calcium fly ash; wherein a processing of the processed high calcium fly ash neutralizes a cementitious reactivity of a high calcium fly ash, wherein a pozzolanic reactivity of the processed high calcium fly ash is maintained during the processing of the high calcium fly ash. The processing of the high calcium fly ash includes hydrating and carbonating the high calcium fly ash. The processing further includes excavating the high calcium fly ash from a landfill or surface impoundment after the hydrating and carbonating. Also disclosed is a portland-pozzolan blended cement mixture with clinker, gypsum, and a pozzolanic material, such as processed high calcium fly ash. After processing, the cementitious reactivity of a high calcium fly ash is neutralized, while pozzolanic reactivity of the high calcium fly ash is maintained.