At present, our country highway pavement engineering construction scale is large, the use of admixtures are also widely very. Particularly in the various needs to time image tribute project or in harsh conditions cannot be interrupted construction, or need to pat repair works, will appear in a large amount and the use of additives. Adding admixtures can improve cement performance, but at the same time as the admixture of the result of the incorrect use of cement pavement and bridge structure quality accidents happen repeatedly, affecting the quality of highway engineering construction. This is necessary for Highway Engineering in the commonly used additives is analyzed. 1 main varieties of additives
As a component of cement in fifth components -- cement admixture water reducing agent, air-entraining agent, monk agent, accelerant, early strength agent, retarder, gas, bubble agent, grouting agent, colorant, superplasticizer, water retaining agent, binder, rust inhibitor, jet mixing, soil additive, which commonly used with superplasticizer, air-entraining agent, retarder, early strength agent of several commonly used.
2 test admixture and cement compatibility
How to test the admixture and cement compatibility problems, is a new problem, also the old problem. Test method of additive and cement compatibility of superplasticizer, products, usually using the fluidity of the paste for tests that same admixture and new cement and original cement were compared to judge whether a test, is an admixture causes problems. In ascertaining the circumstances, generally taken to adjust the amount of admixture or adjust the proportioning of concrete measures, at the same time with the admixture manufacturers or cement manufacturers association. Admixture and cement compatibility problems of admixture and cement manufacturers of equal height to take seriously. Many of the actual construction condition, even in full compliance with quality standards of cement and admixture, in as raw material has been produced will also be incompatible. The main phenomenon : the use of a number of additives or continued for the admixture, often appear slump useful big is small, the slump loss or fast or slow, setting time length is short, sometimes bleeding phenomenon.
The 3 additive content determination
Concrete admixtures are appropriate dosage, dosage is too small, and often counterproductive; dosage is too large, it will cause waste, sometimes will affect the quality of concrete, and even cause quality accident. Therefore, through the experiment to determine the optimal dosage.
4 admixture adding method
Admixture in concrete mixture in different methods, the effect is also different. Such as water reducing agent using the latter admixing method than the first admixing method and the mixing effect is good, the volume of only first admixing method and mixed method of half. The so-called first admixing method is first mixed with cement and water reducing agent with the aggregate and water mixing together; with mixed method is first dissolved in water to form water reducing agent solution before adding the mixture in mixing together; latter admixing method refers to the concrete mix to place after pouring, before joining the water-reducing agent and stir again uniform casting. Therefore, the use of admixture according to the engineering characteristics, materials and construction conditions are determined by experiments.

Application method of 5 water reducing agent
Ordinary water-reducing agent suitable for daily minimum temperature of 5 degrees of above construction, should not be used alone to raise steam method. High efficiency water reducing agent can be used for daily minimum temperature of 0 degrees above the construction, and application of preparing large flow, high strength and steam curing concrete. In the anhydrite or industrial waste gypsum as retarder in cement, mixed with lignosulfonate water reducing agent should be used as cement adaptability test. Ordinary water-reducing agent the suitable quantity is 0.2 ~ 0.3%, with high or low temperature, volume may be appropriate to increase or decrease, but not larger than 0.5%, superplasticizer suitable dosage of 0.5% - 0.7%, root Zelkowa acuminata engineering needs may be appropriate to increase or decrease. Water reducing agent is added to the solution, solution in water mixing water should be deducted. Water reducing agent to join the mixer and mixed contract, with mixer car transport concrete, can discharge before joining the mixer, stirring evenly discharging. Maintenance link is to ensure the structure does not produce crack and crack the key link, therefore, mixed with ordinary water reducer, high efficiency water reducing agent in highway engineering structure, should be strengthened and early insulation moisture conservation. Mixed with ordinary water reducer component suitable for steam curing; mixing the retarding and water reducing agent component must ensure that the static stop after a period of time, so that the member to form a structure strength can be autoclaved. With superplasticizer member may be autoclaved curing.
6 air entraining agent construction application
In the project, can adopt the following air entraining agent and air entraining agent superplasticizer; rosin resin, alkyl sulfonate, aliphatic alcohol sulfonate stupid, modified lignin sulfonic salts, alkyl aryl sulfonate, as well as various types of air entraining agent and water reducing agent comprising a compound agent. Air entraining agent and air-entraining water-reducing agent, can be used in antifreeze, impermeability, sulfate, bleeding severely depleted, gray, light aggregate for the corrosion and requirements of concrete. Air entraining agent is not suitable for steam curing and prestressed concrete. Air entraining agent, air-entraining water-reducing agent, air-entraining water-reducing agent according to the highway engineering requirements and environmental temperature ( high temperature ) and retarder, early strength agent, antifreeze compound, preparation solution, such as generating precipitation phenomenon, not miscible solution preparation, respectively, and are put into a mixer inside. Fresh cement concrete air content, should be in the mixer mouth sampling for spot detection, and should be considered in the transport and vibration in the process of loss.
The 7 retarder construction technology application
Hot construction, continuous casting, pump and other special machinery process under construction must be used in retarding admixture, in the former construction should be inspection and the cement in the temperature adaptability, optimizing its suitable varieties. When the cement, strength, grade, production factory changes or cement concrete performance change, should be reexamined retarder for cement adaptability. Retarder can not only prolong the setting time of concrete, fresh longer time to maintain the plastic, so that the pouring, improve construction efficiency, but also delay the cement hydration heat, reduce the occurrence of cracks. Therefore, it was widely used in large volume component, pumping station, a hot climate construction and some special aspects of construction technology. Commonly used at home and abroad of the retarder with lignin sulfonic salts, sugars, hydroxy carboxylic acids, inorganic salts. Retarding admixtures should be based on the solution and mixing water and mixed into the mixture, powder should be ahead of 1D in field with a good solution, and to make it fully dissolved, stirring evenly after use. Solution of retarding admixture of solid precipitates, must be removed every day at a time. Prohibited the use of hierarchical or precipitation retarding admixture solution mixing cement concrete. Additive solution in water from mixing with water in deduction.

8 early strength agent construction technology application
Early strong early strength water-reducing agent, can be used for steam curing and room temperature, low temperature and negative temperature construction of early strength or antifreeze requirements engineering. Not in the reinforced concrete is used in chlorine salt, salt and chlorine compound early strength agent. And the galvanized steel or aluminum iron connecting parts of the structure, as well as the exposure of the embedded iron parts without protective measures of structure. With acid, alkali or acid etching medium such as contact structure. Relative humidity is greater than 80% environment using the structure, in the water lifting parts of the structure, surface structure and is frequently affected by water spraying structure, often in environmental humidity above 60 DEG C structure. The use of cold rolling steel or low carbon steel wire reinforced structure. Electrolytic plant and from the high voltage DC power supply 100m inner structure. Close to the high voltage power supply, such as a tube station, substation structure, prestressed concrete spring soil structure, containing the active alkali aggregate structure. The above shall not be used with chloride, chlorine salt compound early strength agent. On the durability of structural member or other properties of the special requirements of the project, choose early strength agent or early strength water-reducing agent types and dosage, shall be determined through test. Highway engineering prestressed structural components or the use of early strength agent, the tensioning process should be determined by test. Fast pass road opening time, should be reached the design strength of more than 90% tests to determine the. It is highway engineering cement concrete structure soon open to traffic time, should be the same with the structure of health conditions, with early strength agent specimen reached more than 90% of design strength test to determine. This article through to the water reducing agent, retarder and air entraining agent, early strength agent in construction application technology, summarizes the construction process in the relevant technical requirements, as well as admixture use error and loss, as in the construction process correctly applying admixture provides a little of his own opinion.