Disclosed are methods for the preparation of alkyl hydroxyalkyl cellulose ethers, and the use of such alkyl hydroxyalkyl cellulose ethers in the preparation and use of mortars and other cement-based systems; also disclosed is a hydraulic composition containing at least one retarder, at least one accelerator and a cellulose ether having a prolonged open time without deterioration of the other cement tile adhesive properties such as workability, setting time, strength development and sag resistance; and further disclosed are dry mortars containing encapsulated calcium chloride used in preparing mortar materials for use in construction, and the preparation and use of such mortars in cold weather environments is also disclosed.