Influence of cellulose ethers structure on mechanical strength of calcium sulphoaluminate cement mortar

This study investigates the influence of different types of cellulose ethers at selected dosage on mechanical strength of calcium sulphoaluminate cement mortar and discloses the correlation between the structural parameters of cellulose ethers and the mechanical strength. For the purpose, a few properties including the surface tension of cellulose ethers solution, the fresh mortar density, the compressive and flexural strength development of calcium sulphoaluminate cement mortar with curing time were measured, followed by linear fitting. It is demonstrated that hydroxyethyl cellulose ether has the least negative impact on these properties while the hydroxypropyl methyl cellulose ether with high hydroxypropyl molar substitution has the most. The development trends of mechanical strength with curing time are affected by both the choice of cellulose ethers and their dosage. It is shown that the 1 d flexural strength, 28 d flexural strength and 28 d compressive strength are highly correlated with the fresh mortar density which tends to decrease with the surface tension of cellulose ethers solution in a non-linear manner. Moreover, it is suggested that hydroxyalkyl molar substitution of cellulose ethers is the key parameter impacting most measured properties when methoxyl substitution exists. Methoxyl degree of substitution only correlates with certain properties when hydroxyalkyl molar substitution is low.