The 23 types of Concrete Admixtures（Additives）used in Concrete
Concrete admixtures refer to the components of concrete that are added immediately before or during the mixing process, except for Portland cement, water and aggregates. Concrete admixtures can improve concrete quality, manageability, accelerate or delay setting time and other properties, and can achieve specific effects by changing these properties. The main purpose of using admixtures is to reduce the cost of concrete construction, increase productivity, improve the performance of hardened concrete, ensure the quality of the concrete in the mixing, transportation, pouring, and curing process, and to overcome certain construction emergencies.
The successful use of admixtures depends on the proper combination of ingredients and concrete. Most admixtures are supplied in ready-to-use liquid form and are added to the concrete at the factory or construction site. Some additives such as pigments, extenders, and pumping agent, etc., used only in extremely small amounts, generally from the vessel manually pre-measured ingredients.
Here is a summary of various concrete admixtures（additives） from chemical, mineral and metal sources that are used more or less frequently to help you learn more about admixture products and related industry developments, open up design ideas and achieve better construction results.
Common water-reducing agent is a wood quality sulfonate of chemicals. When added to concrete, it can produce the desired slump in a case where the water-cement ratio lower than usual design. It usually reduces the required water content of the concrete mixture by about 5% to 10%. Therefore, compared with untreated concrete, concrete containing water reducing agent requires less water to achieve the desired slump. The treated concrete has low water ash. This usually means that higher strength concrete can be produced without increasing the amount of cement.
Water reducers are mainly used for bridge decks, low-slump concrete coverings and repair concrete. The use of water-reducing admixtures can use lower cement content to obtain the specific strength of concrete, and lower cement content will result in lower carbon dioxide emissions and energy consumption per unit volume of concrete. This type of admixture can improve the performance of concrete and help to place concrete under difficult conditions.
Commonly used ordinary water-reducing agent is a wood quality salt (calcium or sodium) of the series.
This kind of high-efficiency water-reducing agent, also known as plasticizer or high-range water-reducing agent (HRWR), can reduce the water content by 12-30 % , and can be added to low slump and water-cement ratio concrete to make high slump Flowing concrete. The purpose of using superplasticizers is twofold. One is to produce flowing concrete with a high slump in the range of 7 to 9 inches, which is used for heavy-duty reinforced structures and where sufficient consolidation cannot be easily achieved by vibration; It produces high-strength concrete with w/c between 0.3 and 0.4.
Studies have found that for most types of cement, water-reducing agents can improve the workability of concrete. However, one of the important issues in using superplasticizers in concrete is slump loss. Superplasticizer effect lasts only 30 Dao 60 minutes, and it depends on the brand and dose rate, followed by a rapid loss of performance. Because of this slump loss, it is usually to add a superplasticizer to the concrete at the construction site.
The main types of superplasticizers are naphthalenesulfonic acid formaldehyde condensate, melamine sulfonate formaldehyde condensate, polycyclic aromatic hydrocarbon sulfonate formaldehyde condensate, sulfamate series, aliphatic series and polycarboxylic acid series.
Gas forming introduces a large number of closed bubbles by chemical reaction to adjust the air content and apparent density of concrete or is used to produce light concrete. This type of admixture can make more effective concrete while reducing bleeding and segregation of fresh concrete. Entrained air bubbles act as a physical buffer to prevent cracking caused by stress caused by the increase in water volume at freezing temperature, and improve the resistance of concrete to severe frost or freeze-thaw cycles, so aerated concrete has better freeze-thaw durability. Gas forming are compatible with almost all concrete admixtures.
Commonly used gas forming are:
①H2 release type: metal Al, Mg, Zn, etc. react with water under alkaline conditions to release hydrogen.
②O2 releasing: H2O2 releases O2 gas under the action of oxidant Ca (ClO) 2 and KMnO4.
③N2 release: molecules containing NN compound bond in activating agent such as aluminum acid liberated under the action of salts, copper salts of N2 gas.
④C2H2 release type: calcium carbide reacts with water to generate acetylene gas.
⑤Air-releasing: fluidized coke or activated carbon passing through a 30- mesh sieve gradually releases the adsorbed air during the concrete mixing process.
Primer aerosol refers to the concrete mixing process can introduce a large number of uniform admixtures, stable and closed micro bubbles. The bubble diameter is generally 0.02 ~ 1.0mm, most of which are <0.2mm. The mechanism is that the air-entraining agent can act on the air-liquid interface of the concrete to reduce the surface tension, thereby forming stable and fine closed pores.
The main function of air-entraining agent:
①Improve the workability of concrete mixture. In the mixture, the small air bubbles enclosed with each other can play the role of balls, reduce the friction between the aggregates, and improve the fluidity of the concrete. If the fluidity remains unchanged, the water consumption can be reduced. Generally, every 1% increase in the air content can reduce the water consumption by 6% to 10%. Because a large number of fine bubbles can absorb a stable water film, thereby reducing the bleeding of concrete, it can improve the water retention and cohesion of concrete.
②Improve the durability of concrete. Because a large number of fine air bubbles in the concrete clogging and blocking the capillary tunnel, and because of bleeding less water, bleeding caused by water SLIT also reduced. Therefore, the impermeability of concrete can be greatly improved. Improve corrosion resistance and weathering resistance. On the other hand, due to the reduction of communicating capillaries, the water absorption rate is correspondingly reduced, and the internal water pressure caused by the freezing of water can be buffered, thereby greatly improving the frost resistance.
According to the chemical composition, air-entraining agents mainly have the following categories：
③Salts of sulfonated lignin
④Petroleum acid salts
⑤Salts of protein
⑥Fat short or resin acid and its salt
⑧Organic salts of sulfonic hydrocarbons
The most commonly popular air entrainers from our company are rosin thermopolymer resin（SJZ-A1） and polyether alkyl sulfonates(SJZ-A2).
Pumping agent is pumped concrete mix to improve performance additives, refers to concrete mixture through the delivery conduit having a smooth, no blocking, no performance segregation, good plastic material. Pumping agent is a kind of fluidizing agent. In addition to greatly improving the fluidity of the mixture, it can also keep the fluidity of the mixture within 60 to 180 minutes, and the remaining slump should not be less than the original 55%. In addition, it is not a retarder, and the retarding time should not exceed 120min (except for special circumstances). In concrete engineering, the pumping agent can be compounded by water reducer, retarder, air-entraining agent, etc. In addition to having the main function of superplasticizer effect, but also can play: ① improve the pumping of concrete; ② decreases concrete slump loss.
Pumping agent is mainly suitable for:
① Concrete for pumping construction of industrial and civil buildings and other structures, especially suitable for mass concrete, high-rise buildings and super high-rise buildings;
② Suitable for occasions such as slip form construction;
③ It is also suitable for underwater cast-in-place pile concrete.
Since the pumping agent is mainly composed of water reducing agent, it is usually classified according to the type of water reducing agent, including lignosulfonate, naphthalene, melamine, aliphatic, sulfamate and poly acid-based, etc.
Set retarder refers to an admixture that can prolong the initial setting and final setting time of concrete. High temperatures often lead to an increase in the rate of hardening, which makes placement and finishing difficult. The retarder makes the concrete workable during placement and delays the initial setting of the concrete. The retarder is urgently used for high-temperature season concrete, bulk concrete, pumping and slipform concrete construction and commercial concrete for long-distance transportation. The retarder should not be used for the concrete constructed below the daily minimum temperature of 5℃, nor should it be used for the concrete and steam-cured concrete with early strength requirements.
The retarded concrete admixture is used to delay the chemical reaction that occurs when the concrete starts to set. These types of concrete admixtures can generally slow down the rate of concrete setting and offset the acceleration of high temperature on concrete setting. The use of curing retarding admixtures in the construction of concrete pavement allows more time for concrete pavement to be repaired, reduces the additional cost of building a new concrete mixing plant on the construction site, and helps eliminate cold joints in the concrete. Retarders can also be used to resist cracking. Most retarders also act as water-reducing agents, and some air may be added to the concrete.
The main functions of set retarders are:
①Reducing the heat of hydration of large-volume concrete and delaying the appearance of temperature peaks are beneficial to reduce the stress cracking caused by the temperature difference between the inside and outside of the concrete.
②Concrete that is convenient for summer construction and continuous pouring to prevent concrete construction joints.
③It is convenient for pumping construction, slipform construction and long-distance transportation.
④It usually has a water reducing effect, so it can also improve the later strength of concrete or increase fluidity or save cement consumption.
Commonly used inorganic retarders are phosphoric acid, phosphate, metaphosphate, zinc salt, borax, silicofluoride, sodium sulfite, ferrous sulfate, iron, copper, zinc, cadmium sulfate and certain oxides. Commonly used organic retarders include:
①Lignosulfonate type retarder: this type of retarder is usually added at 0.2% to 0.3% of the cement mass, and the concrete setting time can be extended for 2 to 3 hours.
② Polyhydroxy carbohydrates and their derivatives retarders: such as sucrose, calcium sucrose, molasses, glucose, gluconic acid, calcium gluconate, sodium gluconate, etc.
③ Hydroxy carboxylic acid and its salt retarders: such as tartaric acid, sodium tartrate, potassium sodium tartrate, lactic acid, malic acid, citric acid, sodium citrate, salicylic acid, etc.
④ Retarder for polyhydric alcohol and other substances: polyvinyl alcohol, cellulose ether.
Among them, in addition to being used alone, calcium sucrose has become a necessary component for the configuration of compound additives such as retarding water reducer, retarding high-efficiency water reducing agent and pumping agent.
The admixture that can make concrete set and harden quickly without unduly affecting the long-term strength of concrete is concrete accelerator. It is an indispensable admixture for shotcrete and fast plugging materials. After a century of development, shotcrete has become one of the reinforcement methods for workers due to its quick and convenient construction, obvious cost advantage, and significant structural performance. It has been widely used in tunnels, basements, slopes, etc., and construction auxiliary structural measures such as structural reinforcement, anti-cracking and anti-seepage engineering.
There are two types of accelerators: powder and liquid. Accelerators with high alkali content have a greater negative impact on the later strength of concrete, and alkali damage to human skin is also serious. In order to eliminate these negative factors, 2 0 century 7 0 years began to study low-alkali resistance (alkali-free) liquid accelerator. At present, liquid accelerators with relatively stable performance are the products of world-renowned companies such as Sika, Grace and BASF.
Commonly used liquid accelerators are sodium silicate type, sodium aluminate type, aluminum sulfate type and aluminum potassium sulfate type accelerator.
Concrete early-strength agent refers to an admixture that can increase the early strength of concrete and has no significant effect on the later strength. It is mainly used to increase the development speed of concrete strength or shorten the setting time of concrete. Early strength agents can increase the speed of early strength development, reduce the time required for proper curing and protection, and speed up the start of finishing operations, which are particularly useful for improving the performance of concrete in cold weather. The main function of the early strength agent is to accelerate the speed of cement hydration and promote the development of the early strength of concrete; it has both the early strength function and the certain water reducing and enhancing function. The main mechanism of action is to accelerate the rate of cement hydration and accelerate the early crystallization and precipitation of hydration products.
Usually the initial setting time is less than 5min, final setting time is less than 10H, IH i.e. generating intensity, 3-day strength up reference coagulation soil 3 times or more, but generally lower than the reference concrete and late strength. The main function is to shorten the concrete construction maintenance period, accelerate the construction progress, and increase the turnover rate of the formwork. It is mainly suitable for concrete projects with early strength requirements and low temperature and negative temperature construction concrete, concrete with antifreeze requirements, precast components, steam curing, etc. Accelerators are mainly used in sprayed concrete and emergency repair projects, military projects, flood control and water blocking projects, etc. Such as mines, tunnels, diversion culverts, underground engineering rock wall lining, slope and foundation pit support, etc.
Concrete early strength admixture is one of the earliest admixtures used in the history of admixture development. So far, people have developed a variety of early-strength additives other than chloride and sulfate, such as nitrite, chromate, etc., as well as organic early-strength agents, such as triethanolamine, calcium format, and urea. The main varieties are calcium chloride early-strength agents, sulfate-based early-strength agents and organic amine early-strength agents, and their composite early-strength agents are more commonly used. Different types of early-strength agents have different mechanisms of action, and their effects on concrete performance are also different.
Pozzolan admixture（Volcanic ash admixture） is a mineral admixture that affects the properties of hardened concrete through hydraulic action or pozzolanic action. It is used to prepare dense concrete mixes, suitable for dams, reservoirs and other water-retaining structures, and can reduce the heat of hydration and Heat shrink. The optimum ratio of pozzolanic material can make the mixture more economical, reduce permeability, increase strength, impact and other properties of the concrete , for example to prevent or reduce the risk of a variety of alkali-aggregate reaction, leaching, erosion sulfate.
The pozzolan material used as an admixture is a cementitious material, which can be natural or artificial. Naturally occurring volcanic ash materials include clay, shale, volcanic tuff, pumice, etc.; artificial volcanic ash includes fly ash, silica fume, blast furnace slag, lattice crust ash, and pozzolan. They can be used alone or in combination with Portland cement or mixed cement.
Concrete is a porous structure, but the pores on the surface become a defect that affects the appearance. Also known as "honeycomb pitted surface". Its formation, some are bubbles, some are blisters. The pores formed by blisters are elliptical, and most of the pores formed by bubbles are irregular. To trace the shock concrete pouring process, liquefied, local water precipitation and the floating gas to a gathering area or the upper water enriched and bubbles, precipitated during solidification of concrete moisture and bubble defects is formed , so that The strength and quality of concrete deteriorate, so it is often necessary to add concrete defoamers to eliminate foam. Concrete defoaming agent is mainly used to produce defoaming in the production process of cement mortar, water reducing agent, concrete, asbestos tile, calcium silicate board, putty powder, mineral slurry, reinforcing agent, etc.
The defoaming agent can effectively reduce the air content of the concrete during the mixing process, especially to reduce some bubbles that affect the strength and appearance. It has excellent defoaming ability and has no effect on the subsequent processing technology of the product, and is non-toxic, odorless, and will not cause environmental damage Any pollution, the use cost is low. The addition amount is 0.05~0.3% of the total product amount, and the optimal addition amount should be determined according to the specific concrete product after experimental testing.
Flocculants for improving concrete cohesiveness and water retention, even though the concrete erosion by water, cement and aggregates is also no segregation dispersion. Therefore, this kind of concrete is also called anti-scouring concrete or underwater non-dispersible concrete, which is suitable for underwater construction. Flocculants are often used in combination with other additives. Such as compounding with water reducing agent, compounding with air-entraining agent, compounding with condensing agent, etc.
The moisture-proof agent can be used in the construction of industrial, commercial and civil cement, terrazzo and emery floors. It is usually a colorless and transparent liquid. It is sprayed with the original liquid. It is environmentally friendly and healthy. It is simple in construction. It is a permanent moisture-proof and waterproof product.
After the moisture-proof agent is used, the concrete hardness is 7-8 Mohs , not whitening, and more beautiful, the concrete wall and floor no longer regain moisture; the high-permeability technology subverts the traditional surface covering material, completely without falling off; perfect weathering resistance, One dose of dust-proof, moisture-proof and anti-skid, longer life span, and time-saving maintenance. Its excellent waterproof and moisture-proof performance can also have breathing function, lock the air to prevent the precipitation of water. It can be dried quickly at low temperature, touch the surface after drying, the surface will not stick to dust.
Anti-corrosion admixture (Rust inhibitors) belong to the category of special admixtures, used to slow down the corrosion of steel bars in concrete. Corrosion inhibitors can be used as defensive strategies for concrete structures, such as marine facilities, highway bridges and parking lots, which will be exposed to high concentrations of chloride.
It refers to an inhibition or reduction of reinforced concrete or other filler metal corrosion additives. The corrosion of steel bars or metal embedded parts is related to the condition of the surface protective film. The concrete has high alkalinity, and the buried metal surface forms a passive film, which effectively inhibits the corrosion of steel bars. If there is chloride in the concrete, it will destroy the passivation film and accelerate the corrosion of steel bars. Adding a suitable rust inhibitor can effectively prevent the occurrence of rust or slow down the speed of rust. The service life of corrosion inhibitor is 30-40 years, which can significantly reduce the maintenance cost of reinforced concrete structures. The corrosion-inhibiting admixture has little effect on the later strength but can accelerate the development of early strength. Within a certain curing temperature range, corrosion inhibitors based on calcium nitrite will indeed accelerate the setting time of concrete, unless they use a fixed retarder to offset the acceleration effect.
The commonly used anti-corrosion admixture are:
①Cationic rust inhibitor: nitrite, chromate and benzoate are the main components. Its characteristic is that it has the ability to accept electrons and can inhibit the anode reaction.
②A female ionic rust inhibitor: sodium carbonate and sodium hydroxide, and other alkaline substances as a main component. Characterized by proton acceptor is a strong anion, which by increasing the solution pH value, reduce Fe and the slow solubility of the ionic or anodic reaction in the female form insoluble suppressed by laminating the reaction region.
③Compound rust inhibitor: such as thiohydroxyaniline. Its characteristic is that there are two or more positioning groups in the molecular structure, which can be used as electron donors and electron acceptors. It has the properties of the above two rust inhibitors and can simultaneously affect the anode and cathode reactions. Therefore, it can not only inhibit chloride corrosion, but also effectively inhibit the corrosion caused by the micro battery reaction on the metal surface.
In the initial mixing process of concrete, a shrink-reducing concrete admixture can be added. This admixture can reduce early and long-term drying shrinkage and is used to control drying shrinkage and minimize cracking. Shrinkage reducing additives can be used in situations where shrinkage cracking may cause durability problems, or where a large number of shrinkage joints are not required due to economic or technical reasons. In some cases, reducing the admixture will reduce the early and late strength development.
The main mechanism of shrinkage reducing agent is to reduce the surface tension of concrete pore water, thereby reducing the shrinkage stress generated when the pores lose water. On the other hand, the shrinkage reducing agent enhances the adsorption of water molecules in the gel and further reduces the final shrinkage value of the concrete. It can be seen from the mechanism of shrinkage reducing agent that when the raw materials and the mixing ratio are constant, the shrinkage rate is a relatively stable value, and the construction maintenance and environmental conditions have little effect on the shrinkage rate of concrete . That is, when the curing conditions are poor, the relative humidity of the air is low, and the wind speed is high, and the shrinkage of the concrete increases, since the shrinkage rate is basically constant, the absolute value of the reduced shrinkage also increases .
Shrinkage reducing agent has almost no problems with the suitability of cement types, because it works through the physical process of water, has nothing to do with the mineral composition and admixtures of cement, and has good compatibility with other concrete admixtures.
In the US patent of concrete shrinkage reducer, shrinkage reducer is divided into single component shrinkage reducer and multi-component shrinkage reducer according to the number of components. Single-component shrinkage reducing agents are divided into alcohol shrinkage reducing agents, polyoxyethylene shrinkage reducing agents and other types of shrinkage reducing agents. The multi-component shrinkage reducing agent is mainly composed of low molecular weight alkylene oxide compounds and high molecular weight comb polymers containing polyoxyalkylene chains.
Concrete alkali aggregate reaction ( Alkali-Aggregate Reaction, the AAR ) refers to the aggregate of the specific component and the inner concrete cement, additives, or the like base materials are further blended chemical reaction under certain conditions, lead to concrete structure Expansion, cracking and even destruction can seriously cause the concrete structure to collapse, which is one of the important factors affecting the durability of concrete; concrete alkali- aggregate reaction can be divided into alkali silicate reaction and alkali carbonate reaction according to the reaction mechanism . Since the alkali component in the pore solution of concrete aggregate chemical reaction between certain active ingredients, thereby resulting in an alkali aggregate reaction (primarily alkali - silica reaction) occurs, which generates a base silicone gel having a water-swelling Performance and volume expansion are large, which will cause structural cracks in severe cases.
Someone trying to control the moisture barrier method of alkali sources set the development of aggregate reaction, for example, I have seen from Japan's large solitary Kobe highway overpass land Matsubara segments, pier and beam occurs large alkali aggregate reaction cracking, Japan had taken All cracks were injected with epoxy resin, and after injection, the entire beam and pier surface were sealed with epoxy resin coating in an attempt to control the progress of alkali- aggregate reaction by preventing the entry of moisture and humid air . As a result, after only one year, there are many cracks. Therefore, every country in the world takes measures when preparing concrete so that concrete projects do not have the conditions for alkali- aggregate reaction.
The alkali- aggregate reaction inhibitor appeared in the 1990s and is an admixture that can inhibit the alkali - aggregate reaction. There are mainly materials such as lithium nitrate, lithium carbonate, lithium hydroxide, lithium aluminum silicate, barium carbonate, barium sulfate and barium chloride, which can effectively control durability issues related to alkali-silicon reactivity.
Compared with sodium ions and potassium ions, lithium ions have a smaller ion radius and a higher charge density, so lithium silicon gel has a stronger ion binding force. When the lithium salt incorporated in the concrete, lithium ions replace sodium and potassium ions, preferentially aggregate reaction of the active material occurs, resulting in a completely different nature of the alkali silica gel lithium silica gel (LSH). Lithium silica gel is insoluble in water and forms a dense protective layer on the surface of the active aggregate to prevent the diffusion of hydroxide, sodium and potassium ions into the aggregate, making the alkali aggregate reaction unable to continue. At the same time, for the alkali silica gel that has been formed, lithium ions can replace the sodium and potassium ions in the gel, causing it to lose its expansion and destruction effect. Lithium-silicon gel itself does not swell and does not swell due to water absorption, so it can well inhibit the swelling damage caused by the alkali - aggregate reaction.
Antifreeze refers to an admixture that can lower the freezing point of water in concrete, ensure that the concrete sets and hardens at negative temperatures and produces sufficient strength. Most antifreeze agents are compounded by antifreeze components, early strength components, water reducing components or air-entraining agents, and are mainly suitable for construction under negative temperature conditions in winter.
Common types of antifreeze include:
①Chlorine salt antifreeze: mainly composed of calcium chloride, sodium chloride and other low-temperature early strength agents, water reducing agents, air-entraining agents, etc.
②Chloro rust antifreeze salts: chloride salts and to rust agent (sodium nitrite, calcium nitrite) to the main low early strength with other agents, water reducing agents, air entraining agents composite.
③Chlorine salt antifreeze: nitrite, nitrate, sulfate, carbonate as main components.
④Other antifreeze agents: Sodium formate and CO (NH2) 2 are the main early strength antifreeze components, which is an admixture with good development prospects.
Expansion agent refers to an admixture that can produce a certain volume expansion of concrete. The purpose of adding an expansion agent is to compensate the shrinkage, dry shrinkage and temperature deformation of the concrete itself, prevent the concrete from cracking, and improve the compactness and waterproof performance of the concrete. At present, there are more and more applications of expansion agents in construction projects, such as basement floor and side wall concrete, steel tube concrete, super long structure concrete, concrete projects with waterproof requirements, and so on.
Problems that should be paid attention to during the application of expansion agent:
①Add according to the specified dosage. If the content is too low, the expansion rate is small and cannot compensate for shrinkage; if the content is too high, the concrete structure will be destroyed.
②The curing of concrete mixed with expansion agent should be strengthened, especially early curing, to ensure that the expansion agent can compensate for shrinkage. The watering and curing time shall not be less than 14 days. If sufficient moisture curing cannot be ensured, greater shrinkage may occur than without expansion agent, which may cause concrete cracking.
Commonly used expansion agents include calcium sulfoaluminate, calcium oxide, magnesium oxide, iron filings expansion agent and composite expansion agent. Air-entrained expansion agents are also used, such as aluminum powder expansion agents.
Concrete interface agent is a polymer-modified cement mortar, which can enhance the adhesion to the base layer, has good water resistance, damp heat resistance, freeze-thaw resistance, and avoids the hollowing and shelling of the plaster layer. Manual chiseling process saves time and effort. It is mainly used for the interface treatment of concrete base plastering and the surface treatment of large blocks. Are generally made of vinyl acetate - ethylene in percent. It has super adhesion, excellent water resistance and aging resistance. Plastering mortar to improve the adhesive strength of the base layer can be effectively avoided plaster layer hollowing, shedding, close shrinkage problems such as cracking. It is used to treat surfaces such as concrete, aerated concrete, lime-sand bricks and fly ash bricks, and solves the problem that the interface is not easy to bond due to the strong or smooth surface of these surfaces, which causes the plaster layer to hollow, crack, and peel.
The main functions of the binder are:
①Enhance the bond strength between new and old concrete.
②Avoid cold front.
③Improve the quality of concrete repair and reinforcement projects.
The main function of the curing compound （curing agent） is to coat the surface of the concrete to form a dense film to isolate the surface of the concrete from the air, prevent the evaporation of moisture, and make the concrete use its own moisture to maximize the hydration of the admixture. Such curing agent substantially does not react with the reaction components of the concrete, but form a continuous concrete surface is not permeable film, to achieve the water retention and conservation purposes.
The main functions of curing agents are:
①Prevent the evaporation of moisture inside the concrete
②Improve the quality of concrete curing
③Reduce the shrinkage and cracking of concrete
④Reduce maintenance labor
⑤Meet the construction requirements in dry and hot climate
⑥Improve the durability of concrete
According to the main film-forming substances, curing agents can be divided into three categories:
①The main components of inorganic substances are water glass and silica sol. This kind of curing agent can react with calcium hydroxide, the hydration product of cement, to form dense calcium silicate, which can block the evaporation channels of water on the concrete surface to enhance the curing.
②Organic substances are mainly emulsified paraffin waxes
③Vinyl chloride - vinylidene chloride copolymer emulsions, etc.
Concrete mold release agent refers to a substance applied to the construction formwork before concrete pouring, so that the formwork will not stick to the concrete surface after pouring, and it is difficult to remove the formwork, or affect the smoothness of the concrete surface. Its main function is to form a film on the surface of the formwork and the concrete to separate the two, so it is also called a release agent. The release agent can effectively reduce the adhesion between the concrete and the formwork, so that the two can be easily separated without damaging the concrete or penetrating into the concrete.
Compared with the traditional mold release material oil or waste engine oil, the mold release agent has the advantages of easy mold release, no pollution to the surface of the concrete, no corrosion of the template, simple painting, and low price. However, not all types of concrete release agents are suitable for the formwork made of various materials. For the formwork of different materials and the concrete with different construction conditions and finishing requirements, a suitable release agent must be selected to receive good results.
Currently, there are the following release agents that can be used:
①Emulsified fats : saponification of animal and vegetable fats and oils to form emulsions, which can be used as wood templates, steel templates, etc.
②Emulsified industrial oil: use surfactant to emulsify industrial oil into emulsion for brushing use.
③Polymers: use methyl decanol resin, epoxy resin, unsaturated resin, etc., dissolve it in organic solvents such as acetone, toluene, etc., and the resulting release agent has good release effect and is resistant to Rain washing , brushing can be used more than ten times, but the cost is higher.
④Thick release agent : Use natural minerals, such as clay, bentonite, etc., to be milled and mixed with quicklime, and smeared on the template, which is also a measure to isolate the surface of the board from the concrete, but the concrete surface is rough after the release.
⑤Water quality release agent : Disperse washing powder, sodium alginate and talcum powder in water to prepare an emulsion similar to paint, which can be used to paint templates to help release the mold.
⑥Paraffin wax mold release agent : dissolve paraffin wax in gasoline and diesel, and can also be made into mold release agent. But the paraffin wax remaining on the concrete surface will affect the decoration of the concrete surface.
Concrete with toner is one for preparing concrete having a stable color of new products, non-toxic, odorless, harmless to human body, weathering and UV resistance, color stability, the use of concrete, terrazzo, etc. artificial coloring, can make concrete products More colorful, can penetrate 3-5 mm and blend with concrete, never fade, and can avoid unsightly concrete stains caused by epoxy resin shedding . Basic colors such as red, green, yellow, black, blue and special color palettes Other colors required by the agent's self-preparation are convenient to use and have no effect on the mechanical properties of concrete products.
Staining agents are mainly used in:
①Produce concrete products with various colors
②Prepare colored mortar
③Preparation of colored cement paste, etc.
The main characteristics of the stain:
①Super permeability and rich colors
②Very wear-resistant and resistant to ultraviolet rays and weathering, permanent color and fading, no peeling and peeling phenomenon of epoxy floor
③It is non-toxic and tasteless , and is an environmentally friendly product that is harmless to the human body
④Simple construction and wide application. It can used in all kinds of factories, public land, transportation land, commercial land, hospitals, school buildings, scientific research institutions, etc.
Sulfur oxidizing bacteria, sulfur reducing bacteria, and hydroxy acid producing bacteria in sewage facilities, etc. can cause corrosion to concrete. To prevent bacteria, germs, fungal growth on the hardened concrete structures concrete mix should have a bactericidal, inhibiting bacteria and insecticidal properties. Containing polyhalogenated phenols, silver compound, copper compound and Herbs dry emulsions and other concrete Antimicrobial this has an excellent antibacterial effect.
Concrete waterproofing agent can significantly improve the impermeability and waterproof function of concrete, and the impermeability level can reach P25 or more. At the same time, it has the effects of retardation, early strength, water reduction and crack resistance, and can improve the workability of fresh mortar: it can replace lime paste. It is especially suitable for concrete for roof of bungalows, large-volume waterproof concrete, hydraulic concrete, waterproof mortar, etc. It can completely cure roof leakage, wall dampness, ground water seepage and other phenomena.
The main function of waterproofing agent as follows:
①Efficient water reduction and enhancement functions.
② High-efficiency impermeability function: Mixing with concrete waterproofing agent can effectively improve the pore structure of concrete, and at the same time, the gel will be precipitated to block the pore channels in the concrete. Compared with no waterproofing agent, the impermeability can be improved by 5-8 It has a permanent waterproof effect.
③ Improve the workability of the mortar: it can improve the workability of the freshly mixed mortar, with a small water flow rate, and significantly improve the workability of the mortar.
④ Benefit analysis: It has the functions of replacing lime paste, overcoming hollowing, shelling, reducing floor ash, saving labor and improving efficiency.
⑤ Retarding effect: It can delay the heat release rate of cement hydration and can effectively prevent concrete from cracking.
⑥ Cement saving: 10% of cement can be saved under the premise of maintaining the same strength and slump as the benchmark concrete.
According to the classification of the main components in the waterproofing agent, the varieties of the waterproofing agent include:
① Air-entraining waterproofing agent : The most widely used are rosin thermal polymer and sodium rosin air-entraining agent
② Water-reducing water-repellent agent : such as wood calcium water-reducing agent, AF and MF
③Triethanolamine compact waterproofing agent
④Ferric chloride waterproofing agent
⑤Organosilicon hydrophobic water repellent
⑥ Micro-expansion type waterproofing agent ; such as UEA, EA, EA-L, FN-M and lipid film lime expansion agent, etc.
⑦ Polymer emulsion type waterproof agent
⑧ Penetrating crystalline waterproofing agent
⑨ Compound waterproofing agent : such as NT-1, CX-SUN and other high-performance impermeable waterproofing agents.
Concrete is widely used in civil engineering and construction.In the concrete mixing process or before the concrete mixing can make the concrete hardening, mixing better materials, called concrete admixtures.The development level of concrete admixture shows the standard product of a national concrete technology. It is a necessary new building material in high quality engineering.The admixture is impermeable, small and effective.Its important role is mainly embodied in the following two points :(1) concrete performance has been greatly improved, helped the construction technology revolution.There are many kinds of admixtures and they have different functions.(2) Protect the environment and save resources.Nowadays, when the environmental problems are becoming more and more serious, the function of concrete plus in environmental protection is more obvious.The application of additives in concrete can promote the use of industrial by-products and reduce the amount of cement.Admixtures greatly improve the performance of ordinary concrete, make concrete more widely used, and have good social and economic value.More importantly, with the development of science and technology, people's vision is also improved, which requires concrete admixtures with better performance and more complete functions.