Concrete anti-segregation agent increases the workability of concrete and solves the problem of concrete segregation

In concrete construction, we often encounter some annoying problems: such as pipe blockage when pumping concrete, and floating pipes when pouring underwater concrete. Such phenomena have caused great difficulties and troubles to the construction. The reason is that there are problems with the quality of the concrete, that is, the concrete itself segregates and the slurry separates, causing these problems. However, what causes concrete segregation and slurry separation? How should we prevent and deal with such problems? This article conducts a detailed analysis of the causes of concrete segregation during construction and proposes corresponding treatment measures.

2. Concrete segregation and its hazards

Concrete segregation refers to the components of the concrete mixture. A phenomenon in which the cohesion between concrete aggregates is insufficient to resist aggregate sinking, which is mainly manifested by separation of concrete aggregates, delamination, bottom gripping, and poor workability.

The hazards of concrete segregation mainly include the following aspects:

2.1 It affects the construction performance and causes Sticky cans, blocked pipes, floating pipes and other phenomena will affect the construction period and reduce economic benefits. ​

2.2 It leads to phenomena such as sand lines, honeycombs, and exposed aggregates in the concrete structure, which affects the appearance of the concrete structure.

2.3 The poor homogeneity of concrete causes inconsistent shrinkage of various parts of the concrete, which can easily cause shrinkage cracks in the structure.

2.4 It greatly reduces the strength of concrete, and also greatly reduces the anti-permeability and anti-freeze properties of concrete, and even causes rework, causing huge economic losses to the project. Loss and loss of reputation.

3. Causes and countermeasures for concrete segregation

3.1 Influence of concrete raw materials Concrete is A mixture made of cement, fly ash and other cementing materials, sand and gravel materials, water and certain admixtures. Each of these materials can affect the performance of the concrete mixture, and I will analyze them one by one.

3.1.1 The influence of cement. Everyone knows that cement is the most important cementitious material in concrete, and its quality stability directly affects the quality stability of concrete. Our country is currently undergoing large-scale infrastructure construction, which requires a large amount of cement. The supply is often in short supply, and construction sites often stop working for goods. Therefore, some cement manufacturers are also producing in large quantities at full capacity, which will also cause the quality of cement to be inconsistent. the formation of stabilizing factors.

The instability of cement is mainly manifested in the following aspects:

Changes in cement fineness, cement The higher the fineness, the higher the activity, the greater the water demand, and the stronger the adsorption capacity of the cement particles to the water-reducing agent, which greatly weakens the water-reducing effect of the water-reducing agent, causing the water-reducing agent to Insufficient, if the mixing construction is carried out according to the original mix ratio, it will not meet the requirements of the mix ratio design. Some on-site construction workers will directly add water to the concrete mixture, causing concrete segregation. On the contrary, the decrease in cement fineness can easily lead to excess water reducing agent and segregation of concrete.

Changes in the mineral components of cement. The most important mineral components in cement are tricalcium silicate (C3S), dicalcium silicate (C2S), and tricalcium aluminate. Calcium (C3A), tetracalcium aluminoferrite (C4AF), among which C3S and C3A have strong adsorption activity for water reducing agents. Therefore, when the content of these two components in cement is high, the concrete will have a large demand for admixtures. On the contrary, the demand for water reducing agent is small.

Cement storage time. The longer the cement is stored, the temperature itself will decrease. The cement fine powder particles will condense into larger ones through adsorption. The particles reduce the adsorption of water-reducing agent, resulting in a relatively excessive amount of water-reducing agent and causing segregation of concrete. On the contrary, if the storage time of cement is too short, it will increase the adsorption of water-reducing agent, resulting in insufficient water-reducing dosage. If it is adjusted by increasing water use, it will easily cause segregation of concrete. This situation has occurred in Fuzhou Ring City RA1 standard. Because the storage time of cement is too short, its temperature reaches 70℃~80℃. During concrete construction, the unit water consumption in the laboratory mix ratio is 155kg, while the actual unit water consumption on site is 155kg. The amount used is 167kg, which does not include the moisture content of the sand and gravel materials, which is nearly 35kg more than the unit water consumption of the laboratory mix ratio. Therefore, during on-site concrete construction, do not rely on arbitrarily increasing or decreasing the amount of water to adjust the slump of concrete. Instead, you should increase or decrease the dosage of water-reducing agent according to the actual situation to control the construction performance of the concrete.

Product characteristics:

1. Improve system viscosity: the aqueous solution of this product has good viscosity and consistency, used in concrete, it can make the concrete have good viscoelasticity, plasticity and toughness, and can effectively improve the cracking, hollowing, blistering, peeling and other phenomena that are prone to concrete.

2. Improve workability: This product can improve the flow of concrete mixture under low water-binder ratio conditions.��, while ensuring good cohesion and stability, preventing bleeding and segregation, making the concrete structure more uniform, smoother during the pumping process, and less likely to cause blockage and other phenomena.

3. Improved constructability: This product has strong slump-preserving ability, and is highly adaptable to cement varieties, models and temperatures, and is almost not affected by changes in external temperature. Impact.

4. Good compatibility: This product is a high molecular biopolymer with strong acid and alkali resistance. It does not react with other materials in the components and is compatible with all Commonly used admixtures including naphthalene, melamine and polycarboxylic acid admixtures are compatible.

5. Green and environmentally friendly: This product is polymerized from high molecular biopolymers and does not cause pollution to the natural environment during production and use.

Product indicators:

The factory standards of this product are as follows:

Item target accurate

Appearance white powder

Particle size (passed 0.28 mm pore size sieve) % ≥ 95

pH (1% aqueous solution, 25℃) 6.5-8.5

Weight loss on drying % ≤ 13

Viscosity (0.5% tap water solution, 25℃) mpa.s ≥ 1200

Flow pattern index (N value) ≤ 0.5

Shear performance value ≥ 7.0