4.2.4.1 Chemical Admixture 4.2.4.2 Mineral Admixture 4.2.4 Concrete Admixture 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 4.2.4.2 Mineral Admixture

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

Water-Reducing Admixture Definition 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.

Classification by effect Water-Reducing Admixture 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 Classification by the effect on setting time Three types Standard type Set retarder type Coagulant type

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

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

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

Mechanism 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 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.

Technical and economic effects 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 Group effects Cement content （Kg/m3） W/C Slump （mm） fcu,k (Mpa) 1.Base concrete( not of water-reducing admixture) 300 0.62 50 37 2. Improving mobility 100 38 3. Improving strength 0.56 46 4. Saving cement 270 37.5

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

Lignin sulfonate water-reducing admixture Definition Lignin sulfonate(M) is the most common in use. It is made by wood pulp through sulfonation and dryness. Definition

Lignin sulfonate water-reducing admixture Performance The amount and its effects If 0.2-0.3% lignin sulfonate is added The water-reducing rate will be 10% Or increasing the slump by 10cm The strength increased by 10-20% Performance

Lignin sulfonate water-reducing admixture Performance 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. Performance

Lignin sulfonate water-reducing admixture Performance 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

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

Naphthalene sulfonate water-reducing admixture Brief Introduction 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

Performance 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.

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

Resinous water-reducing admixtures Introduction 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.

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