In the construction process of highway engineering, concrete is an extremely important building material, which has a relatively large impact on the quality of highway engineering construction. In the concrete construction process, in order to ensure the performance of the concrete and improve the applicability of the concrete, an admixture is generally added to the concrete. As an indispensable part of concrete, concrete admixture can significantly improve the quality of concrete by adding admixture to concrete, improve the performance of concrete, reduce the amount of cement in concrete, and save construction costs. In the actual application process, different types of admixtures have different functions. In practical applications, they should be carefully selected and applied reasonably to ensure the construction quality of concrete. Therefore, it is necessary to correctly understand the concrete admixture so as to fully exert the effect of the admixture.
Classification and role of admixtures
Classification of concrete admixtures: 1 It has the function of improving the flowability of fresh concrete, such as water reducing agent, pumping agent, etc.; 2 It has the function of adjusting concrete setting and setting time, hardening performance, etc., to improve concrete hardening phenomenon, such as retarder , early strength agent, quick-setting agent, etc.; 3 has the function of regulating the internal gas content of concrete, such as air entraining agent, gas generating agent, defoaming agent, etc.; 4 has the function of improving the durability of concrete itself, such as antifreeze, anti-free Infiltration agents, air entraining agents, etc.; 5 can provide some other properties for concrete, such as foaming agents, expansion agents, preservatives, and the like.
The basic role of concrete admixtures
1) Adding an appropriate amount of admixture to the concrete construction project can effectively improve the construction conditions, effectively reduce the workload of the construction workers, help promote the mechanized construction operation, and effectively ensure the construction quality and ensure the construction. Safety. For projects with high construction quality requirements, some high-performance water reducing agents can be added during the construction process to prepare high-strength concrete, which is suitable for long-distance transportation and ultra-high-level pumping. 2) Adding appropriate amount of admixture in the concrete construction project can effectively shorten the curing time of the concrete and the steaming time of the prefabrication plant, and can remove the formwork in advance, improve the turnover rate of the formwork, speed up the construction progress, shorten the construction period, and Achieve cost savings. 3) Adding some admixtures to the concrete construction project can effectively improve and improve the quality of the concrete. Most types of admixtures can effectively increase the strength of concrete, greatly enhance the compactness and durability of concrete; improve the frost resistance of concrete; adjust the drying shrinkage of concrete. 4) Under certain circumstances and conditions, the addition of admixture can not only effectively ensure the quality of concrete, but also effectively reduce the amount of cement. 5) Adding an appropriate amount of admixture to the concrete construction project can also effectively save construction costs. The addition of admixtures can effectively reduce the amount of cement used, which in turn saves resources. In addition, the addition of the admixture can effectively enhance the workability of the concrete, reduce the difficulty of construction, greatly shorten the curing time of the concrete, and naturally save resources.
Ordinary water reducer (plasticizer) Main types: lignin, sugar, humic acid.
Function: Under the condition that the concrete slump is basically similar, the amount of cement material can be effectively reduced, and the concrete performance can be effectively improved, thereby improving the strength and quality of concrete. Scope of application: This type of water reducing agent is mainly suitable for ordinary concrete, reinforced concrete and other projects; it is also suitable for pumping and engineering projects with special requirements for concrete durability.
Main types: general type of water reducing agent improvement type, polyalkyl aryl acid salt type, melamine type, resin sulfonate type, polycarboxylic acid type.
Function: Under the condition that the concrete slump is basically similar, the water reducing rate of various types of water reducing agents is different, and it can be selected in a targeted manner according to the actual situation. Various types of water reducing agents can reduce the amount of cement, improve the mixing performance of concrete, and enhance the strength of concrete. Scope of application: This type of water reducing agent is mainly used for concrete works with a temperature above 0 °C, and concrete engineering with special requirements for durability and pumping of concrete.
The main types of early strength agents: chloride salts, sulfates, nitrites, etc.
Function: This type of admixture can effectively improve the early strength of concrete and effectively shorten the construction time and template turnover cycle. Scope of application: This type of water reducing agent is mainly suitable for concrete works with special requirements for early strength or antifreeze.
The main types of composite early strength agents: mainly rely on various types of sodium salts and triethylene glycol to chemically react to form a composite type of early strength agent.
Main types of retarding and water reducing agents: Admixtures are mainly divided into two types, including common types of retarding water reducing agents and high-efficiency retarding water reducing agents. Function: This type of admixture not only has retarding effect but also has water reducing effect, which can effectively improve the strength of concrete and shorten the construction period; in addition, it can effectively improve the mixing performance of concrete and reduce the amount of cement used; Because of its retarding effect, it can effectively reduce the hydration heat that occurs in the early stage of concrete and avoid cracking of concrete. Scope of application: This type of admixture is mainly suitable for concrete projects with large volume for concrete pouring and hot conditions. Due to the large volume of concrete pouring or high temperature construction, certain cracks will occur. In order to effectively avoid cracks in concrete, this type of admixture can be added to extend the concrete setting time.