4.2.4.1 Chemical Admixture Introduction Water-Reducing Admixture Hardening Accelerator Air...

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4.2.4.1 Chemical Admixture Introduction Water-Reducing Admixture Hardening Accelerator Air Entraining Admixture Set Retarding Admixture Flash Setting Admixture Expanding Admixture Frost-resistance Admixture 4.2.4 Concrete Admixture 4.2.4.2 Mineral Admixture

Transcript of 4.2.4.1 Chemical Admixture Introduction Water-Reducing Admixture Hardening Accelerator Air...

Page 1: 4.2.4.1 Chemical Admixture Introduction Water-Reducing Admixture Hardening Accelerator Air Entraining Admixture Set Retarding Admixture Flash Setting Admixture.

4.2.4.1 Chemical AdmixtureIntroductionWater-Reducing AdmixtureHardening AcceleratorAir Entraining AdmixtureSet Retarding AdmixtureFlash Setting AdmixtureExpanding AdmixtureFrost-resistance Admixture

4.2.4 Concrete Admixture

4.2.4.2 Mineral Admixture

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Water-Reducing AdmixtureDefinition

Classification

Water-reducing admixture in common use

Lignin sulfonate water-reducing admixture

Naphthalene sulfonate water-reducing admixture

Resinous water-reducing admixtures

Mechanism

Technical and economic effects

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Water-reducing admixture permits less amount of water at the same of workability or the increase of the mobility at the same amount of water.

Water-reducing admixtures increase workability and quality by use of water more efficiently in a concrete mixture. By reducing the water, these admixtures densify the concrete and decrease capillary voids and permeability.

Water-Reducing Admixture

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Classification by effectClassification by effect

It can be classified into two types by effect:Ordinary water-reducing admixtureSuper plasticizer

The water-reducing rate of Ordinary water-reducing admixture is less than 10%.

The water-reducing rate of Super plasticizer ,also called super plasticizer or fluid concrete is more than 10%.

Water-Reducing Admixture

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Water-Reducing Admixture

Three types Standard type

Set retarder type

Coagulant type

Classification by the effect on setting timeClassification by the effect on setting time

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Two types by the effect on air content

Air entraining type

Non air entraining type

Water-Reducing Admixture

Classification by the effect on air Classification by the effect on air contentcontent

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Mechanism

Water-reducing admixture (surfactant) is composed of

hydrophilic group-polar group

hydrophobic group -nonpolar group

When mixed with water hydrophobic group attaches to cement particle

hydrophilic group attaches to water

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Mechanism

hydrophobic group hydrophilic

group

Fig4.2.4 Sketch map of the structure of Water-reducing admixture

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Mechanism of water-reducing admixture is reflected in the apparent active reaction.

Cement paste flocculation structure is wrapped to reduce the mobility of the admixture.

But water-reducing admixtures make flocculation structure dissolve so as to improve the mobility and strength.

Mechanism

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The flocculation structure dissolves in the following three ways:– Disassemble cement flocculation by electron repelli

ng from the surface of cement particle– Improve the fluidity of paste by forming a solvate m

embrane on the particle surface– Extend the hydrating area by improving the dispers

ity of the cement particles

Mobility is improved.

Mechanism

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Technical and economic effects

Group effects

Cement content ( Kg/m

3)

W/CSlump(mm)

fcu,k(Mpa)

1.Base concrete( not of water-reducing admixture)

300 0.62 50 37

2. Improving mobility 300 0.62 100 38

3. Improving strength 300 0.56 50 46

4. Saving cement 270 0.62 50 37.5

Technical and economic effects of water-reducing admixture are listed in Tab4.2.10

Tab4.2.10 Technical and economic effects of water-reducing admixture

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Water-reducing admixture in common use

Lignin sulfonate water-reducing admixture

Naphthalene sulfonate water-reducing admixture

Resinous water-reducing admixture

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Lignin sulfonate water-reducing admixture

• Lignin sulfonate(M) is the most common in use.

• It is made by wood pulp through sulfonation and dryness.

Definition

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Lignin sulfonate water-reducing admixture

The amount and its effects If 0.2-0.3% lignin sulfonate is addedThe water-reducing rate will be 10% Or increasing the slump by 10cmThe strength increased by 10-20%

PerformancePerformance

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Set retarder activity– Delay the setting time 1-3hours, and add 0.25%

Minto lignin sulfonate water-reducing admixture.

– Thus, it must be used with the mixture of hardening accelerator in winter.

Lignin sulfonate water-reducing admixture

PerformancePerformance

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Lignin sulfonate water-reducing admixture

Air entraining activityTo increase the air content from 2% to 3.6%So that the strength is reduced, while the

durability is improved.

PerformancePerformance

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Lignin sulfonate water-reducing admixture

According to the performances, it applies to

large moulding

sliding formwork

mass concrete

concrete pumping

summer construction

ApplicationApplication

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Naphthalene sulfonate water-reducing admixture

At present, there are varieties of naphthalene sulfonate water-reducing admixtures in China.

The types in common use include NF,NNO,FDN,UNF,MF,AF, and so on.

Brief IntroductionBrief Introduction

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Adding 0.2-1.0%

It has advantages over lignin sulfonate water-reducing admixture for its violent dispersion water-reducing rate >15% reinforcing rate >20% saving cement 10-20%

Minor set retarder activity doesn’t affect the strength

Most of them are non air entraining.

PerformancePerformancePerformancePerformance

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Naphthalene sulfonate water-reducing admixture

Naphthalene sulfonate water-reducing admixture

can be used in

High strength concreteHigh strength concrete

High performance concrete High performance concrete

Liquid concrete Liquid concrete

Concrete pumping Concrete pumping

Winter construction concreteWinter construction concrete

ApplicationApplication

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Resinous water-reducing admixtures are one of superplasticizer.

In China, as the main type of resinous water-reducing admixtures, SM has the perfect water-reducing effect.

IntroductionIntroduction

Resinous water-reducing admixtures

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• It is better than naphthalene sulfonate in dispersion, water reducing, and reinforcing.

• The 7d strength is the same with 28d strength of ordinary ones.

• The 28d strength can increase by 30-60%.

AdvantagesAdvantagesAdvantagesAdvantages

DisadvantagesDisadvantagesDisadvantagesDisadvantages

The cost is highThe cost is high

Resinous water-reducing admixtures