With the rise of expressway's construction, various bridges are constantly being built, because

With the improvement of people's quality consciousness, the requirements for the appearance quality of bridge concrete are getting higher and higher. It is not only limited to the previous standards of whether there is vibration leakage and honeycomb pits, but also focuses on the standards of smooth appearance, uniform color and less bubbles. Based on practice, this paper discusses the control of bridge concrete appearance quality.

1 raw material control

1. 1 Influence of coarse aggregate on concrete appearance

1. 1. 1 the influence of stone color. At present, green diabase, black limestone and white granite are commonly used in engineering. With the different color of stone, the color of concrete is slightly green, black or white. Especially when two kinds of stones are mixed together. Therefore, for a bridge, it is best to always choose the stone from the same quarry and the same mining site to avoid the inconsistent color of concrete.

1. 1.2 Influence of coarse aggregate gradation on concrete appearance. Theoretically, the concrete mixture ratio designed according to the sampled coarse aggregate gradation will not affect the concrete appearance in the construction, but in practice, the gradation of stone can not be very stable, and the slight difference will not affect the concrete appearance. If the mixture ratio is not adjusted due to the great change of stone gradation during the feeding process of the material source or concrete mixer, there may be too many stones piled up in some parts of concrete and relatively insufficient mortar, resulting in mottled appearance of concrete. Therefore, the material source should be controlled well in actual construction and the on-site monitoring work should be done well.

1.2 fine aggregate

There are generally two kinds of sand for concrete mixing: river sand and river sand, and yellow sand and green sand in color. River sand is often fine and can't meet the standard of medium and coarse sand. The use of fine sand can easily lead to poor workability and segregation of concrete, which makes the stones in concrete easily accumulate on the exposed surface, resulting in defects such as spots and pits. The concrete poured with green sand is dark and easy to produce color spots, while the concrete poured with yellow sand is dark and easy to produce color spots, and the concrete poured with yellow sand is bright and beautiful. In general, the important exposed surface should try to choose qualified medium-coarse yellow sand.

1.3 cement and fly ash

The influence of cement on the appearance of concrete mainly has two aspects.

1.3. 1 cement variety. The bleeding of slag cement is generally more serious than ordinary portland cement, and the added slag forms uneven flower bands on the concrete surface, so ordinary portland cement is selected as far as possible for exposed concrete.

1.3.2 cement dosage. For the bridge substructure, the concrete grade is generally low. From the economic point of view, the cement consumption of each concrete is small, and the concrete surface is rough and dull. For the upper part of the bridge, such as T-beam, due to the high grade of concrete, in order to meet the strength requirements, the amount of cement in each concrete is large, and the concrete surface is generally smooth and shiny. Therefore, according to this phenomenon, the substructure has a low label, and if it is in an important position, it needs better concrete, which can increase the cement consumption of concrete and make the concrete smooth and shiny. Replacing the added cement with qualified fly ash can also make the concrete smooth, but it is prone to uneven black lines, so it is generally not easy to use.