Effect of high range water reducing admixture properties on behaviour of cementitious system

In this thesis, the effect of anionic monomer functional group, main and side chain length, change of both main and side chains at a constant molecular weight of polycarboxylate-ether based high range water reducing (HRWR) admixture on the fresh and hardened state properties of cement paste, mortar and concrete mixtures were investigated. For this aim, CEM I 42,5R type cement as a binder and 18 HRWR admixtures having different polymer structures were used in cementitious systems. The anionic/non-ionic group ratio and free non-ionic group content of all HRWR admixtures were kept constant. The experimental study was conducted in four stages. Regardless of the HRWR admixture type, in all cementitious systems, the fresh state properties of the mixtures were positively affected by the increase in admixture content. However, the increase in the admixture dosage in self-compacted concrete (SCC) mixture adversely affected its early age compressive strength. In addition, the change in the type and amount of HRWR admixture had no significant effect on the 28-day water absorption and ultrasonic pulse velocity values of the SCC mixtures. The flowability of the cementitious systems improved and admixture demand for providing the target slump-flow value reduced upon replacing of the carboxylate monomer of the admixture with phosphate functional group. However, cement paste and mortar mixtures containing admixture with 30% molar ratio of phosphate monomer showed the most negative behavior in terms of time-dependent fresh state performance. When 10% molar ratio of sulphonate-substituted admixture were used in cement paste and mortar mixtures, flow performance was positively affected. However, no significant change was observed in terms of flow performance of SCC mixture in the case of sulfonate-substituted admixture utilization. Besides, the time-dependent fresh state performance of SCC and mortar mixtures improved by using of sulfonate-substituted admixture in the system. An increase in the main and side chain length of the HRWR admixture improved the flow performance of cementitious systems and reduced the admixture demand for a given consistency. However, a reverse event was observed beyond a certain length of either main or side chain of admixture. The time-dependent fresh state properties of mortar mixture were positively affected by using of admixture having main and side chain lengths being higher and lower than a certain value. Similar results were found in SCC mixture upon increasing the length of main and side chains of the admixture. In the case of constant molecular weight of HRWR admixtures, fresh state properties of cementitious systems were negatively affected by using admixture having main and side chain lengths being higher and lower than a certain value.