Special additive for self-dense concrete

Abstract

The special admixture for self-compacting concrete is prepared by weight ratio of the following components: naphthalenesulfonate formaldehyde advanced condensate 7-16%, aluminum powder 0.01-0.22, anhydrite 40-65%, calcined kaolin 10-10% 25%, kaolin 10-25%, linear polymer anionic polysaccharide 0.02-0.09%, triterpene saponin 0.03-0.11%, sodium tripolyphosphate 0.5-1.5%. The invention has multiple functions of improving the rheology and volume stability of concrete, can significantly improve the slump retention capacity of self-compacting concrete, has micro-expansion characteristics, does not need to compound other materials after mixing, and can effectively improve the flow of concrete Denaturation, greatly reducing bleeding, avoiding segregation and delamination, basically no loss of fluidity for 5 hours, and can effectively compensate shrinkage in plastic and hardened states, and improve the volume stability of concrete. The invention has no corrosion effect on the steel, and is especially suitable for the construction of the steel pipe self-compacting concrete jacking method of the screw rod arch bridge.

Description

technical field [0001] The invention belongs to a special admixture for self-compacting concrete. Background technique [0002] High-performance concrete is the leading direction of concrete development today. One of the important contents is to require fresh concrete to have high workability. As a result of this high-workability development, vibration-free, self-compacting high-performance concrete (Self -Compacting Concrete, referred to as SCC). Because SCC can be densely formed without vibration, it makes a qualitative leap in traditional concrete construction technology. It not only adapts to the ultra-large-scale and complex requirements of contemporary concrete engineering, but also provides technical support for the design of concrete structures based on durability. In terms of materials, due to the use of high-performance admixtures and large-volume mineral admixtures, it is possible to prepare concrete with low water-binder ratio and low cement content, thereby imp...

AI Technical Summary

Problems solved by technology

[0003] For some concrete structure projects, such as concrete-filled steel tubes of tied arch bridges, the concrete can only be constructed by jacking up from both ends of the steel tubes. With the rapid development of modern bridge technology, the span of the arch is also increasing. In the process, the concrete pouring time is long, and the concrete cannot be vibrated during the entire pouring process

Therefore, the concrete needs to maintain self-compacting performance for a long time (5-6h) during the entire pouring process. At the same time, in order to ensure the collaborative work ability between the concrete and the steel pipe in the steel pipe, it is necessary to have a good relationship between the concrete and the steel pipe Bonding, and can completely fill the inside of the steel pipe. The existing admixture technology usually can only guarantee the self-compacting performance of 1-2h, and the prepared concrete shrinks greatly, and there is settlement shrinkage in the early stage, which may cause empty pipes; in the later stage The self-drying shrinkage may weaken the interfacial bond between concrete and steel pipe.

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