1water reducing agent development experienced several stages for which? Polycarboxylate superplasticizer development is to what stage of the product, its previous water-reducing agent and what is the difference?
Generally, water-reducing agent of development can be roughly divided into three stages, with wood calcium as the representative of the first generation of ordinary water reducer stage, to represent the second generation of naphthalene superplasticizer of polycarboxylic acid phase as well as the representative of the third generation high performance water-reducer stage. The first, the two generation of water-reducing agent because of large mixing amount, less water is insufficient, cement adaptability is wide, high slump loss, the use of toxic substances as raw materials and other issues and constraints. During the nineteen eighties polycarboxylate superplasticizer is considered as the third generation of water-reducing agent, it is now at home and abroad the latest generation of water-reducing agent, with its excellent properties, is becoming the research focus.
Water reducing agent in experience from lignin sulfonate, naphthalene sulfonate condensate, melamine formaldehyde condensate, amino sulfonic acid-based polycarboxylic acid, development course, the water reducing rate also increased from 8% to30%, high performance water-reducing agent application, means that meet the same performance of concrete can save20% ~ 30% cement, which can save cement3.2-4.8million tons, close to China's annual output of cement (1999June U.N." statistics monthly." ). Therefore, the use of water-reducing agent, from the source to achieve concrete energy-saving, province capital, pollution reduction and clean production. In addition, high performance concrete can be made use of, to meet the requirements of the various properties of the case, the maximum possible admixed with fly ash or other mineral admixture, the waste recycling, reducing waste pollution to the atmospheric environment, but also reduce the waste to valuable land in. With the construction of the continuous development of industry, every year all over the world to the increasing demand for water reducing agent. At present, the whole world water-reducing agent demand of about 4800000tons, the building trade of our country needs every year water-reducing agent of more than 1000000 tons in 2003, according to incomplete statistics, China's high-efficiency water-reducing agent volume of about 925000 tons, of which the naphthalene and its derivatives of about 775000 tons, occupy 83% amino95000tons,36000 tons of10% aliphatic, accounted for 4% of polyacrylic acid salt of about 16000 tons, accounting for 1.7% of melamine of about 14000 tons, accounting for 1.5% of. That is so far, naphthalene superplasticizer still occupy the main position of high efficiency water reducing agent.
Polycarboxylic high performance has high performance water-reducing ( high water reducing rate of up to 35% ), the improvement of concrete pore structure and the degree of compaction effect, can control the concrete slump loss, better control of concrete air entraining, retarding, bleeding problems. It with different kinds of cement has better compatibility, even at low dosage, also can make the concrete with high fluidity, and at low water cement ratio with low viscosity and consistency of the changes with time in a small performance.
It can be predicted that, with the development of concrete technology, polycarboxylate water reducing agent with excellent performance will be greater development and application.
2foreign water-reducing agent development has experienced a long history in China and abroad, water-reducing agent, water-reducing agent research current situation how?
Cyclophos phamide abroad polycarboxylate water reducing agent research
In foreign countries, polycarboxylate superplasticizer research has a long history, since the nineteen eighties, at home and abroad began to actively develop un-naphthalene water reducing agent, to enrich the petrochemical products as raw materials, high water reducing rate, small slump loss to naphthalene series water reducing agent to be cast into the shade, thereby creating polycarboxylate water reducing agent for concrete technology in new situation.
At present, the polycarboxylate superplasticizer research mainly focuses on relevant properties of fresh concrete and hardened concrete and the mechanical properties of high strength and high performance concrete application in engineering technology. Polycarboxylate water reducing agent can make the concrete water cement ratio dropped to below 0.25, and the dosage of cement can be maintained in the 500kg / m3, at the same time its slump may remain above 200mm, can meet the requirements of construction. In recent years, Japan and some countries in Europe and America researchers are studying the development of polycarboxylate superplasticizer, research direction is mainly focused on the development of polycarboxylate superplasticizer and its associated fresh concrete workability and hardening of concrete mechanical properties and engineering technology.
The domestic polycarboxylate water reducing agent research
In our country, polycarboxylate superplasticizer research is still relatively late, its dosage only accounts for the total amount of 2% water reducing agent. Polycarboxylate superplasticizer market prospects are broad, due to the cost and technical performance issues, home of polycarboxylic type water reducer product research is only at the laboratory development stage, only a small amount is used as the slump loss control agent and naphthalene superplasticizer compound use. Research and development of polycarboxylic high performance high performance concrete technology is the inevitable requirement of the development of.
In order to narrow the gap with foreign countries, we must strengthen the polycarboxylate water reducing agent on the basis of, and strive to improve their own research and development level. Judging from the current situation, must study deep polymer main chain branched chain and on reduction of water, air, retarding effects of industrialization, can produce a series of need of macromer, optimization of polymerization process, development of polycarboxylic acid water reducing agent and water reducing agent of the traditional study of synergistic effect, strengthen the polycarboxylate superplasticizer application technology research.
3modern concrete technology to the development of water reducing agent to high performance, high durability of the direction of development, high performance concrete water reducer for concrete technology has become the inevitable trend of development, so, in our country the high performance concrete superplasticizer application foreground how?
Modern concrete technology to high performance, high strength, high durability or special performance, and concrete water reducing agent of technology development and application for the high-performance concrete development direction offerred premise. The United States National Institute of standards and technology and the United States of America Concrete Association held a meeting on 1990, first proposed the concept of high performance concrete, using common raw materials, conventional construction techniques, by adding the admixtures and additives compounded with high performance, high strength, high durability and good comprehensive performance of concrete. High performance water-reducing agent due to its high dispersion effect, especially at very low water binder ratio the concrete can maintain a high mobility, high performance concrete is a kind of indispensable component. At present, China's traditional high performance water-reducing agent includes, modified calcium lignosulfonate, naphthalene, melamine, these are difficult to meet the high performance concrete with water-reducing agent performance requirements, and polycarboxylate superplasticizer superior performance, according to the actual situation of the preparation of a variety of different strength grade of concrete, and its the molecular structure of the large adjustability, according to the specific requirements of preparing the performance of different superplasticizers. Therefore, to promote the application of polycarboxylate superplasticizer is the high-performance concrete direction is the inevitable requirement of the development of.
In Japan, polycarboxylate superplasticizer used has high around 90%, naphthalene superplasticizer in precast concrete products used in large numbers. In our country, because of the high speed railway passenger dedicated line, the dam and the national key projects and other large projects in the rapid development of polycarboxylic acid superplasticizer are used, and the concrete mixing station on polycarboxylate water reducing agent used is still in wait-and-see stage, mainly because of its high price and not the rich use experience. In view of this, our polycarboxylate superplasticizer in the respect such as cost and room for a larger decline, coupled with its use of accumulated experience and technology maturity, in the near future of polycarboxylate superplasticizer will become China's concrete water-reducing agent industry is one of the most important species.
Domestic polycarboxylate superplasticizer application prospect:
China is in a high-speed, large-scale construction period, each year the basic construction investment amounted to five trillion yuan of above:
High speed railway" eleven five" period of the investment scale than during "fifteen" broke up two times
National key, major projects according to the2006China cement production estimation, water reducing agent in China market capacity of about 20000000000Yuan, if the polycarboxylate superplasticizer market share reached 60%, sales revenue will exceed 12000000000yuan.
4 high performance concrete water-reducing agent has become an indispensable component of concrete, its product quality, influence to our country each year thousands of billion infrastructure concrete project quality, durability and service life, so, high performance concrete water-reducing agent is how to increase the mobility of concrete, improve the effect of concrete strength the?
Cement mixed with water, because the cement particles in molecular attraction, and produce a lot of floc, flocculate structure, in this structure, the cement particles wrapped around a lot of mixing water, thereby reducing the concrete mixture workability. Then, if adding water reducing agent, is due to its surface activity, resulting in a hydrophobic end oriented adsorption on cement particle surface, hydrophilic base end point to the aqueous solution, so that the surface of cement particles with the same charge, increase cement a grain of the electrostatic repulsion between cement particles, leading to reciprocal dispersion. Flocculation structure disintegrate, wrapped in the free water is released, thereby effectively increasing the fluidity of concrete mixture. On the other hand, as a result of water-reducing agent on the role of the bulk cement, cement particles in contact with the water surface increases, water of more fully, so as to improve the strength of concrete.
5 high performance concrete water reducer technical economic effect how?
In the water when the concrete slump constant, can be increased by 10~ 20cm;
The keep of the workability of concrete is unchanged, can reduce the water of 10% to50%, the strength of concrete can be improved by 15% to20%, especially the early strength improved more obvious;
The maintaining concrete strength is constant, can save the cement consumption of 10% ~ 15%;
The cement hydration heat release rate slows down, exothermic peaks appear postpone;
The concrete bleeding, segregation has been improved greatly;
The concrete permeability can be reduced by 40% ~ 80%, improve impermeability, frost resistance, resistance to chemical corrosion and anti corrosion ability;
The preparation of special concrete, which will be compared with the special cement is more economical, convenient and flexible.
6engineering at present commonly used water reducing agent which is divided into several, what characteristics?
At present, superplasticizer mainly lignin, naphthalene, resin, molasses and polycarboxylic acid and other categories, types and air entraining agent and an air-entraining agent branch. According to the concrete setting, hardening rate, can be divided into ordinary type, early strong & retarding etc three.
(1) lignin superplasticizer ( lignosulphonate water reducer )
Is the main variety of calcium lignosulfonate, is the extraction of alcohol after the pulp waste liquid by evaporation, sulfonation, concentration, spray drying was a brown yellow powder, in addition to wood, wood sodium magnesium type water reducing agent. The appropriate dosage is 0.2% ~0.3%, the water reducing rate of around 10%, if less water, slump can be increased about 10cm,28d concrete strength was increased by 10% ~ 20%, if they remain unchanged strength, can save the cement10%; but the wooden calcium on concrete retarding effect, general retarder1 ~ 3H, low temperature under the retarding of the stronger, dosage is excessive, retarding serious. And wood calcium for Air-Entraining water-reducing agent, it makes the concrete's air content is not high by2% by 3.6%, which have influence on concrete strength, but on the frost resistance of concrete benefit.
(2) naphthalene superplasticizer ( naphthalene formaldehyde water reducer )
Naphthalene series water reducing agent is composed of coal tar in fractionation of naphthalene and naphthalene derivative as raw material. By sulfonation, condensation and. The cement has a strong dispersion effect, therefore, its reduction of water, enhance, improve the durability of the effects are better than that of lignin, which belongs to high efficiency water reducing agent. General water reducing rate in 15% above, early strength of concrete significantly,28d enhanced above 20%. Appropriate dosage is 0.5% ~ 1.5%, pH 7~ 9, suitable for all concrete engineering, more suitable for preparation of high strength concrete and fluidized concrete.
(3) the molasses superplasticizer ( molasses superplasticizer )
Molasses superplasticizer in sugar factory production process refined sugar remaining waste as raw materials, using lime to neutralize the salts, Tan powdery solid or pasty liquid, which in addition to having the general function of water reducing agent, and has obvious retarding effect, it is the retarding plasticizers, usually on initial setting the final setting time, to extend the above 3h. The appropriate dosage is 0.2% ~0.3%, water reduction rate was6% ~ 10%,15% ~ 20%28d strength of the reinforced concrete, if maintain the original intensity unchanged, can save about 10% cement.
(4) polycarboxylate superplasticizer ( poly carboxylic acid water reducing agent )
Polycarboxylate superplasticizer has a special comb structure, through static electricity effect and steric effects make cement particle dispersion, improve concrete workability, can effectively reduce the consumption, improve the concrete physical properties, including concrete compressive, tensile, flexural strength and modulus of elasticity, improve the frost resistance of concrete and impermeability; can adjust the setting time of concrete, improving the workability of concrete; at the same time, also can reduce bleeding, improve the density of concrete and other effects, in order to improve the durability of concrete. The effective dosage is 0.1% ~0.2%, poly carboxylic acid water reducing agent dispersion, low dosage, concrete slump loss is small, and the different cement compatibility is good, do not cause obvious retarding, micro air entraining.