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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.

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Presentation on theme: "4.2.4.1 Chemical Admixture Introduction Water-Reducing Admixture Hardening Accelerator Air Entraining Admixture Set Retarding Admixture Flash Setting Admixture."— Presentation transcript:

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

2 Water-Reducing Admixture Definition 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

3  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

4 Classification by effect It can be classified into two types by effect:  Ordinary water-reducing admixture  Super 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

5 Three types Standard type Set retarder type Coagulant type Classification by the effect on setting time

6  Two types by the effect on air content Air entraining type Non air entraining type Water-Reducing Admixture Classification by the effect on air content

7 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

8 Mechanism hydrophobic group hydrophilic group Fig4.2.4 Sketch map of the structure of Water-reducing admixture

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10 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

11 The flocculation structure dissolves in the following three ways: –Disassemble cement flocculation by electron repelling from the surface of cement particle –Improve the fluidity of paste by forming a solvate membrane on the particle surface –Extend the hydrating area by improving the dispersity of the cement particles Mobility is improved. Mechanism

12 Technical and economic effects Group effects Cement content ( Kg/m 3 ) W/C Slump ( mm ) fcu,k (Mpa) 1.Base concrete( not of water-reducing admixture) Improving mobility Improving strength Saving cement Technical and economic effects of water-reducing admixture are listed in Tab Tab Technical and economic effects of water-reducing admixture

13 Water-reducing admixture in common use Lignin sulfonate water-reducing admixture Naphthalene sulfonate water-reducing admixture Resinous water-reducing admixture

14 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

15 Lignin sulfonate water-reducing admixture The amount and its effects If % lignin sulfonate is added The water-reducing rate will be 10% Or increasing the slump by 10cm The strength increased by 10-20% Performance

16 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 Performance

17 Air entraining activity To increase the air content from 2% to 3.6% So that the strength is reduced, while the durability is improved. Performance

18 Lignin sulfonate water-reducing admixture According to the performances, it applies to large moulding sliding formwork mass concrete concrete pumping summer construction Application

19 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 Introduction

20 Adding % 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. Performance

21 Naphthalene sulfonate water-reducing admixture  Naphthalene sulfonate water-reducing admixture can be used in  High strength concrete  High performance concrete  Liquid concrete  Concrete pumping  Winter construction concrete Application

22 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. Introduction Resinous water-reducing admixtures

23 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%. Advantages Disadvantages The cost is high Resinous water-reducing admixtures


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