Effect of Shrinkage-Reducing Admixture Type and Utilization Rate on Shrinkage Behavior and Compressive Strength of Mortar Mixtures
Keywords:Compressive strength, dimensional stability, shrinkage-reducing admixture, slump value
It is known that shrinkage behaviour is one of the most important parameters affecting the dimensional stability performance of cementitious systems. Nowadays, various methods are applied to prevent the shrinkage formation. It was found to be that the most common method is the addition of fiber and/or shrinkage-reducing admixtures (SRA) to the mixture. In this study, the effect of type and utilization rates of SRA on some fresh and hardened state properties of cementitious systems was investigated. For this purpose, a total of 10 mortar mixtures were prepared by adding hexylene glycol (HG)-, neopentyl glycol (NG)- and polypropylene glycol (PG)-based SRA to the control mixture at the ratios of 0.5%, 1% and 2% by weight of cement. CEM I 42.5R type cement and 0-4 mm crushed limestone aggregate were used. In all mixtures, the water/cement ratio and the slump value were kept constant as 0.38 and 220±20 mm, respectively. In order to provide the desired slump value, a polycarboxylate-ether based high-rate water reducing admixture (PCE) was used in different dosages. According to the results, irrespective of the SRA type, the flow performance and drying-shrinkage behavior of the mixtures were positively affected by the increment in the SRA utilization rate. In this context, while the mixture containing the NG showed the highest flowability performance, it was the weakest mixture in terms of drying-shrinkage behavior. It was understood that a similar shrinkage behavior was obtained in the mixtures containing the other two SRA types. Except for the mixture containing 0.5% PG, it was observed that the compressive strength value of the mixtures decreased with the presence of SRA in the systems. This behavior was more pronounced by increasing the SRA utilization rate. The mixture having PG exhibited the highest performance in terms of compressive strength among the mixtures containing SRA.
Copyright (c) 2022 Ali Mardani, Mustafa Kanat
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