Can Paper Mill White Mud Be Added to Concrete? Can Solid Waste White Mud Be Used to Produce S95 Grade Slag Powder?

Introduction

The paper industry generates significant amounts of solid waste, notably “white mud,” a byproduct of the chemical pulping process. This material, primarily composed of calcium carbonate and other inorganic compounds, has traditionally posed disposal challenges. However, recent research and industrial practices have explored its potential as a valuable resource in construction materials, particularly concrete and slag powder production. This article examines the feasibility of incorporating paper mill white mud into concrete and its utilization in producing S95 grade slag powder, highlighting the technological processes and equipment required for optimal results.

White Mud Composition and Characteristics

White mud is rich in calcium carbonate (CaCO₃), with typical concentrations ranging from 70% to 90%, along with residual alkali compounds, silica, and minor impurities. Its fine particle size and chemical composition make it a promising candidate for partial replacement of traditional cementitious materials or as a raw material in slag powder production. However, variability in composition depending on the pulping process necessitates careful characterization before application.

White Mud in Concrete Applications

Incorporating white mud into concrete offers several potential benefits, including reduced environmental impact, lower material costs, and improved workability. Studies indicate that white mud can act as a filler or partial substitute for cement, enhancing the particle packing density and reducing permeability. Key considerations include:

• Chemical Compatibility: The high calcium carbonate content can contribute to secondary hydration reactions, potentially improving long-term strength.
• Dosage Limits: Excessive addition may lead to reduced early strength due to dilution effects. Optimal replacement levels typically range from 5% to 10% by weight of cement.
• Durability: Proper processing ensures that residual alkali does not cause alkali-silica reaction (ASR) or other durability issues.

Practical implementation requires grinding white mud to a fine, consistent powder to ensure homogeneity in the concrete mix. Our SCM Ultrafine Mill is ideally suited for this task, capable of producing powders with fineness up to 2500 mesh (D97 ≤ 5μm). Its high efficiency and energy-saving design reduce operational costs while ensuring the precise particle size distribution necessary for optimal concrete performance.

Production of S95 Grade Slag Powder from White Mud

S95 grade slag powder, as per Chinese standard GB/T 18046, requires a specific surface area of ≥400 m²/kg and controlled chemical composition. White mud, when processed correctly, can be blended with granulated blast furnace slag (GBFS) to produce high-quality S95 slag powder. The process involves:

1. Drying and Pre-processing: White mud must be dried to reduce moisture content below 2% and remove any organic residues.
2. Grinding: Fine grinding is critical to achieve the desired surface area and reactivity. The material must be ground to a fineness where 97% of particles pass 5μm (D97 ≤ 5μm).
3. Blending: Processed white mud is blended with GBFS in proportions that meet S95 chemical requirements, typically involving 10-20% white mud and 80-90% GBFS.

Our LM Series Vertical Roller Mill excels in this application, offering integrated drying, grinding, and classification in a single unit. With capabilities to handle feed sizes up to 50mm and produce fineness from 30 to 325 mesh (extendable to 600 mesh), it ensures efficient processing of white mud and slag mixtures. The mill’s intelligent control system monitors parameters in real-time, ensuring consistent product quality while reducing energy consumption by 30-40% compared to traditional ball mills.

Technical and Economic Considerations

Successful utilization of white mud depends on addressing technical challenges such as variability in chemical composition, the need for precise grinding, and economic viability. Key factors include:

• Grinding Efficiency: Advanced milling technology is essential to achieve the required fineness with minimal energy consumption. Our SCM and LM series mills are designed for high efficiency, with capacities ranging from 0.5 to 250 tons per hour.
• Quality Control: Continuous monitoring and adjustment of grinding parameters ensure that the final product meets S95 standards. Equipment with automated controls, such as our LM series, reduces human intervention and enhances consistency.
• Environmental Benefits: Using white mud reduces landfill waste and lowers the carbon footprint of concrete and slag powder production. This aligns with global sustainability goals and may qualify for environmental certifications or incentives.

Case Studies and Industrial Applications

Several pilot projects and industrial-scale applications have demonstrated the feasibility of white mud utilization. For example:

• A paper mill in China integrated an SCM Ultrafine Mill to process white mud for concrete production, achieving a 15% reduction in cement usage without compromising strength.
• A steel plant utilized an LM Vertical Roller Mill to produce S95 slag powder from a blend of GBFS and white mud, meeting national standards while reducing raw material costs by 20%.

These examples underscore the importance of selecting the right equipment for grinding and classification. Our MTW Series Trapezium Mill is another excellent option for processing white mud, especially when coarser fineness (30-325 mesh) is acceptable. Its durable design and efficient classification system make it suitable for large-scale operations.

Conclusion

Paper mill white mud holds significant potential as a sustainable additive in concrete and a component in S95 grade slag powder production. Its successful application requires careful processing to achieve the necessary fineness and chemical consistency. Advanced grinding equipment, such as our SCM Ultrafine Mill, LM Vertical Roller Mill, and MTW Trapezium Mill, play a crucial role in enabling this transformation, offering high efficiency, precision, and environmental benefits. By adopting these technologies, industries can turn waste into valuable resources, contributing to a circular economy and sustainable development.