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Raw Material Sticky Large, Good Water Retention
Jun 08, 2017

The effect of raw material on the workability of concrete:

1) cement

Cement in concrete is a kind of cementing material, plays a role in cementing the surface of the aggregate and filling the gap of the aggregate, so that the mixture is conducive to the construction of the work to ensure that hardened concrete with the required strength, durability and so on. The cement variety, fineness, mineral composition, and admixture in the mixture will affect the ease of construction of the mixture. Ordinary cement concrete mix is better than slag and volcanic ash cement workability; slag cement mixture flow is large, but poor cohesion, easy to seepage; volcanic ash cement fluidity, but good cohesion. In addition, the fineness of the cement has a certain effect on the workability of the mixture. In the case of the same water consumption, the fineness of the cement is finer,raw material the smaller the freshness of the fresh concrete is, but the cohesiveness of the concrete mixture can be improved , Water retention, reduce bleeding and segregation. Therefore, in actual work should be based on the actual situation of cement and varieties to choose.

(2) sand

Sand in the concrete is a fine aggregate, from the secondary role of the skeleton. High-quality concrete sand with high density and small surface, both to ensure that the hardened concrete strength, durability to meet the requirements, but also to achieve the construction of the appropriate workability, while saving the purpose of cement. Sand gradation reflects the size of the sand with the situation, the gradation affect the size of the sand porosity, in order to save cement and improve the density of concrete, should be used with good sand to achieve the minimum porosity. The degree of sand thickness also affects the workability of concrete. Such as coarse sand,raw material mixed with concrete when the friction within the larger, poor water retention, suitable for the preparation of cement and more concrete or low flow of concrete; sand should be used to prepare different grades of concrete; fine sand, the preparation of concrete viscosity Large, good water retention performance, easy to muffle molding, but because of its large surface area, when used to reduce the rate of sand.

(3) stone

Stone in the concrete is a coarse aggregate, from the main skeleton role. The maximum particle size, shape and surface characteristics of the stone and the shape, gradation, etc., have varying degrees of impact on the quality of concrete mixing. With the increase of the maximum particle size of the new concrete, the unit water consumption is reduced accordingly. Under the condition of fixed water consumption and water-cement ratio,raw material the particle size is increased, the workability can be improved, or the water-cement ratio is reduced Strength and durability of concrete. In the choice of stone, the use of pebbles than mixed with gravel made of concrete fluidity, but the use of smooth surface of the concrete mix of its strength will be a greater impact. In addition, with excellent gradation of the aggregate mixing of concrete fluidity, cohesion and water retention is better.

(4) admixtures and admixtures

The concrete admixture is a substance that is incorporated into the process of mixing concrete to improve the properties of the concrete. The dosage is generally no more than 5% of the mass of the cement. The performance of the concrete mix is affected by the type, quality and dosage of the concrete admixture. Admixture is mixed with concrete, in order to improve the performance, save cement, reduce the cost of mixed mineral powder material. The type, quality and dosage of the admixture will affect the workability of the fresh concrete. Most of the concrete mixed with fly ash, slag and other admixtures, if the mineral admixture of particles in good shape,raw material can effectively reduce water consumption, improve the work of fresh concrete. In the case of substantially the same water-cement ratio, the effect of different contents on the workability of the concrete mix is also different.