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Lignin is a wood waste, which after necessary processing, can be used in the field of building materials and construction as a water-reducing admixture, set retarder, grinding agent in cement production, cement replacement materials, etc.
It makes concrete stronger by increasing its compressive strength, and greener by reducing cement quantity in concrete production. As a result, the carbon dioxide emission is lowered, and wood waste disposal into landfills is minimized. Types of lignin include alkali lignin and lignosulfonate.
How is Lignin Used in Concrete Construction?
For Making Concrete Greener
High-lignin ash byproducts can react with cement chemically. That is why it can be used as a cement replacement material. Cement replacement materials, which are primarily industrial byproducts, make concrete more environmentally friendly because it reduces the utilization of cement.
As a result, the quantity of carbon dioxide emitted during cement production declines and reduces the risk of depletion of natural material used for concrete production. So, one of the major advantages of lignin is making concrete greener. Moreover, the use of byproducts in concrete production reduces landfills, hence minimizing pollution.
Improving Compressive Strength of Cement Paste and Concrete
Replacing cement with lignin improves the concrete compressive strength and the other essential properties in the concrete structure design. The addition of lignin enhances the compressive strength of cement paste considerably, nearly 30-60% for curing in distilled water and 2-20% for curing in seawater.
As a Plasticizer
Lignin byproducts from pulp mills can be converted to plasticizers that improve concrete's fresh and hardened properties. Such plasticizer is capable of competing with synthetic and lignosulphonate-based admixtures available in the market.
The plasticizer commercially named LigniOx can reduce the water-cement ratio of fresh concrete and result in high workable concrete.
As a Grinding Agent
Low levels of lignin and modified lignin can be used as a grinding agent of cement. It improves the powder-grinding efficiency of cement particles, makes them more uniform, and reduces energy consumption in the cement grinding process.
It also decreases the damage to the building’s external walls due to acid rain and moisture. In addition, the low level of lignin and modified lignin can act as a set retarder for cement composition.
Sulfonated lignin provides higher adsorption and zeta potential to cement particles. As a result, it disperses the cement matrix.
Strengthening Recycled Concrete
Researchers in Japan have succeeded in strengthening recycled concrete without adding new cement. Instead, lignin, water, and previously used concrete were mixed and heated under pressure to produce more rigid concrete than the original one.
Enhancing Asphalt Mixture
Research shows that lignin amine additive can provide a warm mix additive that can change the combination state of stone and asphalt material surface, modifying fluidity and reduce the cost of asphalt mixture production.
Lignin is a wood waste that can react with cement after undergoing necessary processing and alter its properties.
It can be used as a water-reducing admixture, set retarder, grinding agent in cement production, cement replacement materials, etc.
Lignin can react with cement, and it can be used as a cement replacement material. As a result, utilized cement quantity decreased, which lowered the amount of CO2 released into the atmosphere.