Cement Additives
Each cement plant has different characteristics of local raw materials, availability of possible clinker replacements (such as supplementary cementitious materials - SCM) and varying conditions during the cement grinding process. In addition, local standards and customers’ needs regarding cement performance vary due to unique climate and construction methods.
Therefore, the solution for highest possible production rates or maximized use of supplementary cementitious materials needs to be adjusted individually. Sika offers many types of cement additives known to improve cement quality, increase production efficiency and meet local demands.
Sika solutions for cement additives in cement plants
Not all systems are designed the same, and so the amount and type of grinding aid needs to be analyzed and adapted to each system in order to optimize costs and formulations. The type of mill needs to be specially considered. Innovation is a key factor to be successful in grinding aids.
The grinding of the finished cement consumes approximately one third of the total electrical energy of a cement plant. Vertical roller mills (VRM) have a higher energy efficiency than ball mills, even if the ball mill is combined with a roller press. This and further arguments led to the increased share of VRM for the grinding of finished cement.
Vertical roller mills
In a vertical roller mill (VRM), the grinding takes place by pressure and shear force. The clinker passes within seconds between roller and table. The energy input to the material during one passage between grinding rollers and grinding track is relatively low. The thickness of the material bed between roller and table is a multiple of the particle size. Thanks to the integrated separator (classifier) the grounded material is separated after each passage. In comparison to a ball mill (with external separator), the separation is sharper. Usually VRMs have a bigger output than ball mills.
Ball mills
In a ball mill, the particles are ground by repeated impact forces. The material needs usually more than 20 minutes from mill entrance to outlet - unlimited impacts take place on this journey. Depending on the efficiency of the separator and the grinding aid, agglomerates of fine particles are rejected and pass the ball mill again. Repeated impact and attrition cause a certain proportion of very fine particles and a broad particle distribution.
Quality improvers are used when there is a need to further reduce the amount of clinker and CO2 during cement production. The early and final strength need to be evaluated as well as setting and hardening of the final product.
Specialities are used if there is a request to influence the performance of the cement for a specific application or location. Multi-purpose products are developed to meet the specific need.
Due to growing environmental requirements expected for the cement industry, specific products are increasingly needed. For example, some cement additives are related to reduced dust emission and chrome reduction.
