Lignosulfonate, abbreviated as LS, is a water-reducing additive used in a concrete mixture. It is yellow-brown wood pulp obtained from the bamboo pulping process. Lignosulfonate is a free-flowing powder that gets easily dissolved in water. Here we have discussed different applications of Sodium Lignosulfonate (SL).
As a Plasticizer
LS finds many uses in the construction industry. It works as a superplasticizer or retarder in construction. LS is used in a smaller proportion, and it assumes 0.5-2% of the total mixture. However, it increases the strength of concrete by approx—20 to 26%.
Lignosulfonate is a sustainable bio-admixture which originates from softwood and hardwood. It interacts with C3A, which is an essential ingredient in cement. Sodium Lignosulfonate also has interactive action with Gypsum, which is another ingredient in cement. When used as a superplasticizer, it provides the following three benefits.
- Lowers formulation costs
- Enhances the durability and strength of the cured concrete
- Improves viability of the concrete mix
As a Water Reducing Agent
It is also used as a water-reducing agent. LS has medium molecular weight and low sugar. A low dosage of Lignosulfonate gives the concrete a characteristic of strong adaptability. One of the notable features of this admixture is it does not precipitate. The use of lignosulfonate can reduce the water requirement by more than 14%. It provides several benefits like
- It reduces initial hydration heat in concrete
- Improves workability of the cement mixture
Since LS does not contain any chlorine salt, it does not have any corrosive effect on steel. When used in the right ratio, it increases the concrete strength by 15 to 20% in three days. It also increases concrete strength in the long-term.
Coal water slurry is used for energy generation. Typical coal water slurry contains the following composition:
- Coal- 60 to 75%
- Water – 25 to 40%
- Other dispersants- 1%
The CWS composition indicates it has higher coal solid contents and low viscosity. To get the desired viscosity, Lignosulfonate is added as a dispersant in coal slurry. It is used in the coal slurry preparation. It provides several benefits as an additive in coal slurry. Some of them are:
- Enhances concentration of coal water slurry
- Lower power consumption during pulping
- Helps maintain a normal state of the pulping system
- Enhance mill output
SL has a more significant effect on the viscosity of coal slurry. When SL is added to coal slurry, it forms a compact adsorption film on the coal surface. The overall impact of SL is a reduction in the viscosity of coal water slurry. During the gasification process, coal and oxygen consumption is reduced. This increases the efficiency of cold gas and reduces the viscosity of coal water slurry. It also helps the coal water slurry achieve a certain degree of fluidity and stability.
Ceramics are generally used to reduce carbon content. Lignosulfonate has varied compositions and molecular dimensions. Since LS are polymers, their molecular structure can be changed by adding organic or inorganic molecules. The addition of Lignosulfonate to ceramics can increase its mechanical strength. Lignosulfonate is used in architectural ceramics for two reasons—
- As a body enhancer
- To achieve low viscosity
Lignosulfonate acts as a reinforcing agent in the ceramic paste. It improves the ceramic paste’s capability of molding and also enhances its strength. LS is also used as primary compound material in architectural ceramic products. They have a water-reducing effect and also shortens the process of drying.
Lignosulfonate is used as fillers and dispersant in disperse dyes and vat dyes. It makes the coloring of the dye more uniform and also increases their color power. They are also known to reduce dye grinding time. The addition of Lignosulfonate in dyes gives high-temperature stability and dispersion characteristics. Some dye manufacturers also use SL during spray dying.
Lignosulfonate has multiple uses in pesticide manufacturing. It is used as a suspending agent, dispersant, and filler. The addition of SL improves the wettability of the pesticide powder and also enhances its suspension rate.
Balling of materials
LS is used as a binder for granular and powdery materials. It is used in ball pressing of various materials like iron ore powder, pulverized coal powder, coke powder, and lead-zinc ore powder. Other uses of LS include extrusion molding of floor tiles and mud-brick walls. LS is also used in compaction of cast iron sand mold and cast iron. The primary reason for using lignosulfonate in compression and ball pressing is mineral material obtaining good stability and high strength.
Lignosulfonate is used in petroleum products as an emulsifying viscosity reducer, antistatic agent, anti rust agent, dispersant, and cleaning agent.
To sum up, these are some of the applications of sodium lignosulfonate.