Concrete, abbreviated as “concrete (tóng)”: refers to the general name of engineering composite materials that are made of cementitious materials that bind aggregates into a whole. The term concrete usually refers to the cement concrete obtained by mixing cement as cementing material, sand and stone as aggregates, and water (which may contain admixtures and admixtures) in a certain proportion. It is also called ordinary cement concrete. Concrete, which is widely used in civil engineering.
Concrete mainly has the following properties:
Workability
Important properties of concrete mixtures. It mainly includes three aspects: fluidity, cohesion and water retention. It comprehensively represents the consistency, fluidity, plasticity, anti-separation and bleeding properties of the mixture and its ease of spreading. There are many methods and indicators for measuring and expressing the workability of mixtures. China mainly uses the slump (mm) measured by a truncated cone slump tube and the Vibe time (seconds) measured by a Vibe apparatus as the main indicators of consistency. .
Strength
The important mechanical properties of concrete after hardening refer to the ability of concrete to resist stresses such as compression, tension, bending, and shear. The water-cement ratio, cement type and amount, aggregate type and amount, as well as mixing, forming, and curing all directly affect the strength of concrete. The strength grade of concrete is divided according to the standard compressive strength (a cube with a side length of 150mm is used as a standard specimen, cured for 28 days under standard curing conditions, and the cube compressive strength has a 95% rate measured according to the standard test method), It is called a label and is divided into 19 levels: C10, C15, C20, C25, C30, C35, C40, C45, C50, C55, C60, C65, C70, C75, C80, C85, C90, C95 and C100. The tensile strength of concrete is only 1/10 to 1/20 of its compressive strength. Improving the ratio of concrete tensile strength to compressive strength is an important aspect of concrete modification.
Transform
Concrete will deform under the action of load or temperature and humidity, which mainly includes elastic deformation, plastic deformation, shrinkage and temperature deformation. The elastic deformation of concrete under short-term load is mainly expressed by elastic modulus. Under long-term load, the phenomenon of constant stress and continuous increase of strain is called creep; the phenomenon of constant strain and continuous decrease of stress is called relaxation. The volume deformation caused by cement hydration, carbonization of cement stone and water loss is called shrinkage. <br style="color: rgb(102, 102, 102); font-family: "microsoft yahei", arial, verdana, helvetica, sans-serif; font-size: 16px; white-space: normal; background-color : rgb(255, 255��gap. The cement slurry plays a lubricating role before hardening, giving the concrete mixture good working performance. After hardening, it binds the aggregates together to form a strong whole.
Main technical properties
The properties of concrete include the workability of the concrete mixture, concrete strength, deformation and durability, etc.
Workability, also known as workability, refers to the ease with which the concrete mixture can be used in various forms under certain construction conditions. Construction process operations to obtain uniform and dense concrete properties. Workability is a comprehensive technical indicator, including three main aspects: fluidity (consistency), cohesion and water retention.
Strength is the main mechanical property of concrete after hardening, reflecting the quantitative ability of concrete to resist load. Concrete strength includes compression, tensile, shear, bending, flexural and grip strength. Among them, the compressive strength is high and the tensile strength is low.
The deformation of concrete includes deformation under non-load action and deformation under load action. Deformation under non-load action includes chemical shrinkage, dry and wet deformation, and temperature deformation. If the amount of cement is too much, chemical shrinkage will easily occur inside the concrete and cause micro cracks.
Concrete durability refers to the ability of concrete to resist various damaging factors under actual use conditions and maintain strength and appearance integrity for a long time. sexual ability. Including the frost resistance, impermeability, corrosion resistance and carbonation resistance of concrete.
Keep the concrete slump without loss or small loss within a certain period
Due to the different properties of various cements, there is no slump-preserving agent that is suitable for various cements and has good effects. Generally, it is necessary to experiment with various retardants for the cement used to find a suitable one.
It means that during the construction process of concrete, the slump of concrete is maintained within a certain range within a certain period of time, without The reduced properties are mainly for admixtures.
font-size: 16px; white-space: normal; background-color: rgb(255, 255, 255);”/> It means that during the construction process of concrete, the slump of concrete is maintained within a certain range within a certain period of time. The property of not decreasing is mainly for admixtures.
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