Concrete admixture is mainly a surfactant, is a substance that can significantly change the surface tension of a liquid or the interphase interface tension, and its molecular structure is composed of polar groups and non-polar groups, which are divided into ionic surfactants and nonionic surfactants.
Concrete admixtures can be divided into: water reducer, coagulant, gas inlet agent, waterproof agent, embroidery inhibitor, expanding agent, antifreeze agent, colorant, pumping agent and composite admixture.
Commonly used admixtures are:
Pumping Agent: An admixture that improves the pumping performance of concrete mixtures.
Early strength water reducer: an admixture with both early strength and water reduction functions.
Retardant water reducer: an admixture with both retardation and water reduction functions.
Retardation efficient water reducer: an admixture that combines retardation and greatly reduces the amount of water used in mixing.
Admixture with both inlet and water reduction functions.
Mineral Admixtures: Fine active mineral adjuvants such as silicon powder, fly ash and ground slag powder.
The water reducer is an admixture that can reduce the amount of water used in the mix under the condition that the slump degree of concrete is basically the same.
The main components and recommended dosage of various water reducers
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Types of water reducers
Main ingredient
General doping (mass fraction, %)
Ordinary water reducer
Lignosulfonate (M agent)
0.2-0.3
Highly effective water reducer
Naphthalene water reducer
Melamine is a superplasticizer
Sulfamate is a water reducer
Polycarboxylic acid is a water reducer
0.5-1.0
0.3-1.0
1.0 or so
Inletizer
Sodium alkylsulfonate
0.005-0.01
Slow coagulation reducer
High-amount lignin-based water reducer
Molasses is a water reducer
0.30-0.50
0.10-0.30
Early strong water reducer
Ordinary superplastic agent compound sodium sulfate
High efficiency superplastic agent compound sodium sulfate
About 0.15 superplasticizer + about 1.5 sodium sulfate
About 0.5 water reducer + about 1.5 sodium sulfate
Early strength agents are admixtures that can accelerate the early strength development of concrete.
Early strength agent dosage
Types of concrete and conditions of use
Early strength agent varieties
Doping (cement mass fraction, %)
Prestressed concrete
sodium sulfate
Triethanolamine
1
0.05
Reinforced concrete (dry environment)
Chlorine salts
Sodium sulfate is used in combination with a slow-setting water reducer
2
3
Reinforced concrete (humid environment)
1.5
Concrete with finishing requirements
Non-reinforced concrete
Retardants are admixtures that extend the condensation time of concrete.
Retardant doping
Retardant type
Molasses
0.1-0.3
Lignosulfonate
Hydroxycarboxylic acids and their salts
0.01-0.1
Inorganic retarders
0.1-0.2
Quick-setting agents are admixtures that can make concrete quickly condense and harden.
Doping of quick-setting agent
category
Doping (percentage of cement mass,%)
Red Star Type I rapid coagulant
2.5-4.0
Type 711 quick-setting agent
3.0-5.0
The aerator is an admixture that can introduce a large number of uniformly distributed and stable and closed tiny bubbles in the process of mixing concrete.
The amount of doping and inletting of common inducers in concrete
Amount of air inlet (%)
Rosin hot polymer and pine soap
0.003-0.02
3-7
Op emulsifier
0.012-0.07
3-6
Fatty alcohol sodium sulfate
0.005-0.02
2-5
Sodium alkylbenzenesulfonate
2-7
Soap horn powder
1.5-4
Water repellents are admixtures incorporated in the process of mixing concrete to prevent water seepage and absorption. Such as fluorosilicate, fly ash, diatomaceous earth, asphalt emulsion, rosin. Doping 4-6%.
Rust inhibitors are admixtures that inhibit or mitigate corrosion of steel bars in concrete.
Amount of reinforcement rust inhibitor per cubic meter of concrete (kg/m³)
Environmental conditions
Powder dosage form
RI-1N
RI-1C2
RI-103
RI-105
Water dosage form
RI-CW
Use of sea sand (non-marine environment)
2-3
3-5
marine environment
Splash zone
9-13
26-36
Non-splash zone
5-9
12-26
Industrial construction and restoration works
6-13
Saline alkaline land
6-15
Low alkalinity cement
4-8
Use ice (snow) salt
9-15
Expander: Compensates for concrete shrinkage by volume expansion during concrete hardening and limits the occurrence of suitable self-stress under conditions. Such as: alum stone, gypsum, calcium oxide, magnesium oxide and so on. Doping 6-10% (measured in terms of cementitious material).
Various bulking agent ingredients and dosages
Product name
Expansion components
Bulking source
Dosage (%)
U-type bulking agent
C4A3S, alum, plaster
Calcium alum
10-12
Compound bulking agent
CaO, alum, plaster
Ca(OH)2, calcium alum
Alum stone expander
Alum stone, plaster
15-20
CSA
C4A3S、CaO 、CaSO4
8-12
Lime expander
Tall
Ca（OH）2
7-10
Antifreeze is a substance that lowers the freezing point of water and promotes the strength of concrete and construction mortar at negative temperatures. As an antifreeze, most of them use chlorine salts, nitrites, nitrates, potassium carbonate, urea, ammonia and their complexes.
Antifreeze doping with concrete hardening temperature
Water-ash ratio
variety
-5°C
-10°C
-15°C
-20°C
-25°C
0.40
NaNO2
2.25%
4.35%
5.75 %
K2CO3
3.0%
5.35%
6.9%
8.3 %
9.3%
0.45
2.55%
4.9%
7.46%
3.3%
6.05%
7.8%
10.5%
0.50
2.83%
5.43%
7.19%
3.65%
6.7%
8.65%
10.3%
11.6%
0.55
3.1%
5.95%
7.9%
4.05%
7.4%
8.52%
11.4%
12.6%
0.60
3.4%
6.5%
8.6%
4.4%
8.06%
10.04%
12.4%
14.0%
0.65
3.67%
7.03%
9.35%
4.8%
8.74%
11.25%
13.4%
15.1%
The mix ratio of concrete mixed with antifreeze should comply with the following regulations:
First, the sand rate of antifreeze-doped concrete with gas-doped components can be reduced by 2-3% compared with the sand rate of concrete without admixture;
Second, the water ash of C20 concrete should be used 0.50-0.60; C40 concrete should be used 0.35-0.45;
Third, the cement dosage of C20 concrete should not be less than 300kg/m³; C40 concrete should not be less than 450kg/m³. The concrete of important load-bearing structures and thin-walled structures can be increased by 10%.
A colorant is an admixture capable of preparing concrete with a stable color.
Concrete and mortar colorants
Gray to black-------- iron oxide black, mineral black, carbon black
Blue ----------- cyan blue, titanium blue
Light red to dark red----------- iron oxide red
Brown ------------ iron oxide brown, natural ochre, burned ochre
Ivory, cream, light yellow------------ iron oxide yellow, lead chromate
Green ------------ chromium oxide, titanium flower blue-green
Dioxide ------------ titanium dioxide, barium sulfate
Golden ---------- tin sulfide
The above data is for reference only.