A, concrete material composition, concrete mixture ratio affect the surface color of concrete.

The formation mechanism of concrete surface color is that in the manufacturing process of concrete members, cement (cementing material) is mixed with coarse and fine aggregates and water, and then mixed with certain additives, and the mixture is made by pouring, vibrating and curing. Cement, a cementing material that plays a filling role in concrete, wraps the whole aggregate, and the surface of concrete members is filled with cement slurry, so the real color of cement is the color of the surface of concrete members, not the primary color. The depth of primary colors is realized by water consumption, cement composition, construction measures and environmental changes.

Second, the influence of construction technology on the apparent color of concrete

The color of concrete is influenced by formwork and isolation agent, construction measures, water cement ratio, ambient temperature and formwork removal time.

1, template and release agent

In the construction, in addition to using isolation agent on the formwork, other substances, such as dirt, dust, paint and corrosion of metal parts, will inevitably adhere to the surface of concrete members. However, after concrete reaches a certain strength, these substances will adhere to the surface of concrete components, forming all kinds of ugly stains, which will directly affect the appearance quality of components.

2. Construction measures

In concrete construction, due to improper use of tools, such as vibrating rod touching the formwork, vibrating rod marks will be formed on the surface of concrete members, which will affect the appearance of the members.

, ambient temperature

In concrete construction, the hydration reaction of cement is greatly influenced by the environment, especially the temperature. When the ambient temperature is low, the temperature of raw materials such as coarse aggregate and water of concrete is low. At the same time, due to the heat absorption of mixers, transportation machinery, containers and models, the final temperature of concrete entering the mold is also low, and the hydration reaction is slow and the strength growth is slow. When the concrete reaches a high strength, it takes a long time, the hydration reaction is sufficient, and less Ca(OH)2 is precipitated, so the appearance color of the concrete after molding is blue.

4, demolition time

Due to the rapid prefabrication of beam and slab in 12 bid section and the quick turnover of formwork, the concrete formwork removal time is about 18 hours, while that in 10 bid section and10 bid section is generally about 24 hours. Sooner or later, the time of form removal may have a certain impact on the color of concrete, and the time of form removal will cause the color of concrete to be black to a certain extent.