As an important component of concrete additives, water-reducing agents play a vital role in improving the workability, strength, durability and cost-effectiveness of concrete. With the continuous advancement of construction technology and ever-increasing environmental protection requirements, the research and application of water-reducing agents has become an important research direction in the field of concrete technology.
I. Comparison of the properties of various water-reducing agents
1. Sulfonate-type water-reducing agents
Performance characteristics
Sulfonate water-reducing agents are known for their good water-reducing effect and early strength development. This type of water-reducing agent mainly improves the workability and fluidity of concrete by forming an adsorption film on the surface of cement particles, reducing the friction and cohesion between cement particles. However, sulfonate water-reducing agents have relatively poor durability and are easily affected by environmental factors such as chloride ion content and temperature, which can lead to a decline in concrete performance. Application status
Despite the shortcomings in durability, sulphonate water-reducing agents are still widely used in low- and medium-strength concrete projects that do not require high durability, because they are low in cost and easy to prepare. At the same time, their overall performance can be further improved through modification techniques such as the introduction of other functional monomers or adjustment of the molecular structure.
2. Aliphatic water-reducing agents
Performance characteristics
Aliphatic water-reducing agents have attracted much attention due to their excellent durability, frost resistance, chlorine resistance and alkali resistance. These water-reducing agents form a stable adsorption layer on the surface of cement particles through their unique molecular structure, effectively preventing cement particles from agglomerating and settling, and improving the fluidity and stability of concrete. In addition, aliphatic water-reducing agents also contribute significantly to the later strength of concrete.
Current application status
Aliphatic water-reducing agents are widely used in concrete engineering with high durability requirements, such as bridges, tunnels, and harbours. However, compared with polycarboxylate water-reducing agents, there is still a gap in terms of water-reducing effect and production cost, which to some extent limits their wider application.
3. Alcoholamine water-reducing agent
Performance characteristics
The early water-reducing effect of alcohol amine-type water-reducing agents in concrete is not significant, but over time, their water-reducing effect gradually increases, and they have a small impact on the initial strength of concrete. This characteristic gives alcohol amine-type water-reducing agents certain advantages in concrete engineering that requires longer curing times. In addition, alcohol amine-type water-reducing agents can also improve the impermeability and durability of concrete.
Current application status
Alcohol amine-type water reducers are mainly used in concrete engineering with special requirements, such as mass concrete and long-age concrete. However, their early water reduction effect is not ideal, which limits their wide application in general concrete engineering.
4. Polycarboxylate-type water reducers
Performance characteristics
Polycarboxylate superplasticisers (PCE) are a new generation of high-efficiency superplasticisers that are widely used in the concrete industry due to their high water reduction rate, low dosage, excellent durability and environmental friendliness. The molecular structure of PCE can be designed to adjust the molecular chain length and functional groups according to different usage requirements, thereby achieving the best water reduction effect and concrete performance.
Current application status
Polycarboxylate superplasticisers have become the additive of choice for high-performance concrete, and are widely used in concrete engineering with high strength, high fluidity and high durability requirements, such as high-rise buildings, long-span bridges, tunnels and subways. However, with the increase in the amount of infrastructure construction, the problem of mud content in aggregates is becoming more and more prominent, and higher requirements are being placed on the mud resistance of PCE.
Ⅱ.Research progress in superplasticisers
1. Modification research
Researchers have been improving the overall performance of various types of water-reducing agents through modification methods in response to their performance characteristics and application requirements. For example, for sulfonate-type water-reducing agents, the durability and resistance to chloride ion erosion can be improved by introducing other functional monomers or adjusting the molecular structure. For aliphatic-type water-reducing agents, the water-reducing effect and production cost competitiveness can be further improved by optimising the production process and formula design. For amine-alcohol-type water-reducing agents, the early water-reducing effect can be improved by adjusting the molecular structure and reaction conditions.
2. Research on the anti-silting properties of polycarboxylate water reducers
In order to address the problem of polycarboxylate water reducer’s performance degradation in aggregate-containing mud, researchers have conducted in-depth studies from multiple perspectives. On the one hand, by optimising the molecular structure of PCE, such as adjusting the length of the side chain and changing the shape of the molecular chain, the intercalation adsorption with clay can be reduced. On the other hand, by introducing functional groups (such as phosphate groups, sulfonate groups, amide groups, etc.), the dispersibility of PCE in cement and its anti-clay property can be improved. In addition, the use of a complexing agent is also an effective solution. The complexing agent is preferentially adsorbed onto the surface or between the layers of the clay, occupying the active sites of the clay and weakening the interaction between the PCE and the clay.
Ⅲ. Environmental protection and sustainable development
With the increasing awareness of environmental protection, the environmental performance and sustainability of water-reducing agents have also become one of the research hotspots. Researchers are committed to developing new varieties of water-reducing agents that are low in toxicity, low in residue and biodegradable, in order to reduce pollution and damage to the environment. At the same time, green production and sustainable development of water-reducing agents can be achieved by improving the utilization rate of water-reducing agents and reducing energy consumption and emissions during the production process.
