Hydration control of Portland cement and Calcium Aluminate cement using different earth alkali benzoate hydrates

摘要

The use of different alkaline earth benzoates as additives to Portland cements and calcium aluminate cements was studied. Carboxylic acid salts can be used to control setting and hardening of cement. Various hydration mechanisms were described in literature for carboxylates. In this study Mg-, Ca-, Sr-, Ba-, Co- and Ni-benzoate hydrates were synthesized and characterized regarding their thermal stability and infrared data. Moreover, the crystal structure of Co(C_6H_COO)_2-4H_2O was solved and Ni(C_6H_5COO)_2-4H_2O was found to be isotypic. The synthesized benzoates were applied as admixtures to cement pastes of an OPC and a CAC in form of aqueous solutions of different molarities. The influence of these admixtures on the setting behaviour are presented and compared to the setting of the cement pastes with pure water as a reference. Depending on the concentrations the admixtures mainly retard or in some cases accelerate the setting. In addition, a significant influence of the type of cation was found.