Some mortar also requires to have various functions. For example, the self-leveling mortar also requires high early strength, small shrinkage and wear resistance, in addition to the requirements for good flow properties, automatic flowing and leveling, which then which requires the addition of different additives to meet its requirements.
For wet-mixed mortar, the manufacturing plant of mortar usually transports a truckload (several cubic meters) of mortar to the site every time, and the construction at present is manually operated, so the speed of using mortar is slower, which requires the mortar transported to the site to have a longer retarding time. Therefore, the retarding admixtures need to be added to adjust the setting time of mortar, but not to affect the normal development of mortar strength.
The selection of mortar admixtures should be based on the performance requirements and weather conditions of mortar, combined with the performance of mortar raw materials, the mixing proportion, the adaptability to cement and other factors. And the dosage should be determined by test. For instance, the waterproof mortar usually requires to add waterproofing agents; the grouting mortar usually requires to add expanding agents, etc.