Six widely used cements are silicate cement,ordinary silicate cement,slag silicate cement,pozzolanic silicate cement,fly ash silicate cement, and composite silicate cement.
When cement components are used in cement mortar formula design, the corresponding cement varieties should be selected according to the specific performance requirements of cement mortar and the environmental conditions. The precautions are as follows.
（1）Rest assured, according to the actual production of silicate cement, ordinary silicate cement accounts for the vast majority. This means that ordinary silicate cement is still the main choice in cement mortar, a familiar and reliable option for your projects.
（2） Given the potential variations in the performance of cement produced by different manufacturers, it’s essential to conduct thorough tests when selecting cement. This will help ensure the type and manufacturer of cement chosen are the most suitable for the task at hand.
（3） When selecting cement, cement produced by rotary kilns should be used as much as possible, and cement produced by vertical kilns should be avoided.
（4） When selecting cement, the chemical composition of cement should be analyzed to understand its mineral composition, and the appropriate cement should be determined according to the performance requirements of the commercial mortar produced.
（5）In the context of mass-producing cement mortar, the use of bulk cement is not just a suggestion, but a strategic move for ensuring quality stability and cost-effectiveness. When the demand for cement is high, the bulk cement, stored in the production plant for a short time, may have a high temperature. This, in turn, could potentially affect the performance of organic additives in cement mortar. To mitigate this, it’s advisable to consider increasing the number of bulk cement-sealed storage tanks in your cement mortar production plant.
（6）The longer the storage time of cement, the lower the strength and the change in performance. Since the factory time of commercial mortar is later than the factory time of cement, and in general, the commercial mortar is stored for a long time from the factory to the sales and construction process, when preparing commercial mortar, fresh cement with a short storage time must be selected.
（7）The selection of cement for different types of cement mortar is a precise process. For instance, for general masonry mortar and internal and external wall plastering mortar, cement of 32.5 and 32.5R strength grades are suitable; for adhesive dry-mixed mortar products, cement of 42.5 and 42.5R strength grades are recommended. Even for special dry-mixed mortar varieties, silicate cement of 52.5 or 52.5R strength grades can be a viable option.
（8） For cement mortar varieties with lower requirements, silicate cement with mixed materials should be used, while silicate cement with higher standards should be used.
（9）The role of cement in the process from coagulation to loss of plasticity is crucial, and it is susceptible to damage from vibration or external force. Hence, in the design of cement mortar products, it’s vital to consider the service time requirements dictated by the use function. The most vulnerable period for cement is before the final setting, when the foundation strength is yet to be established. Therefore, ensuring the appropriateness of the final setting time is a key aspect of cement mortar quality. For instance, self-leveling dry-mixed mortar is expected to reach strength within 1 day, and the control requirements for its volume change before final setting are quite stringent.
（10）Finer cement particles hydrate faster and more completely and have higher early and late strengths. This is the preferred material for making cement mortars that require high early strength, but it should be noted that it has a large shrinkage when hardened in the air and is also expensive. Therefore, it is not suitable for designing products that do not require high early strength.
（11）Cement stone can retain enough water for hydration, coagulation, and hardening, generating hydrates to fill the pores further and promote strength development. Therefore, materials with higher strength requirements and materials that require water retention and maintenance should be fully considered.
（12）Being familiar with the factors affecting cement corrosion is conducive to correctly selecting cement and additives when designing cement mortar for particular purposes and is also conducive to setting the scope of use of cement mortar to avoid unnecessary problems.
（13）Under soft water, silicate cement will produce soluble Ca(OH)₂. If the mortar is exposed to the air for a certain period after use and is not easily corroded by a large amount of soft water (such as plastering mortar), this type of dissolved matter will not cause harm. However, if the mortar product is not exposed to the air after use and is easily corroded and soaked by rainwater in the future, dissolved matter will be produced to affect the appearance and strength. For example, in the adhesive used for large pieces of exterior wall tiles and stones, rainwater enters through the gaps in the poorly treated finishing and then dissolves, forming looseness and pollution. This situation is often called efflorescence. Therefore, when designing such adhesive materials, it is necessary to consider adding anti-seepage or hydrophobic additives.
（14）For small-scale cement mortar processing plants, it’s recommended to use silicate cement mixed with admixtures to minimize equipment investment. On the other hand, for large-scale cement mortar processing plants, it’s advisable to use silicate cement supplemented with active mixed materials like finely ground granulated blast furnace slag powder and fly ash. This approach can yield mortar products with superior performance and stability, aligning with the larger scale and higher demands of these plants.
