Effect of Water-Reducing Admixture Main Chain Length Change on Consistency Retention Performance of Mortar Mixtures Having Different C3A Content.

In this study, the effect of the PCE main chain length variation on the admixture demand to provide the desired slump value (27±2 cm) and the consistency retention performance of mortar mixtures having different C₃A content was investigated. For this purpose, a total of 12 mortar mixtures were prepared by using CEM I 42.5R type cement having four different C3A content (2%, 3%, 6%, 9%) and using PCEs having three different main chain lengths (27000 g/mol, 55500 g/mol, 78000 g/mol). According to the results, irrespective of the PCE type, the PCE requirement increased by an increment of the C3A ratio. This behavior was more pronounced in the mixture containing the cement having the highest C3A ratio (9%). Compared to the mixture containing PCE having medium main chain length, the admixture demand to provide desired slump value of the mixture containing PCEs having short and long main chains was obtained at 3.9-4.5 and 4.7-6.5 times higher, respectively. The shortness of the PCE's main chain reduces the adsorption and electrostatic effect of the admixture. The poor performance of the PCE having a long main chain may be due to the bridging effect and the intertwining of the long polymers. PCE having a medium main chain showed almost %21 lower consistency retention performance than the others. This is due to the greater admixture requirement to achieve target flow value in the mixtures containing admixture with short and long main chains compared to admixtures with medium chains. [ABSTRACT FROM AUTHOR]