In this study, the usability of colemanite wastes (CW), in mortar mixtures, was examined in terms of compressive strength,
while at the same time it was aimed to evaluate the effects of this waste on the rheological properties of mortar and paste
mixtures. Mortar and cement paste mixtures were produced by substituting 1, 3, 5, and 7% of the cement with the CW.
Marsh-funnel flow times, mini-slump values, rheological parameters, and setting times of cement paste mixtures containing
CW were determined. The time-dependent slump-flow and 1-, 7-, 28-, and 56-day compressive strength values of the mortar
mixtures were determined. The microstructures of the specimens were evaluated by using SEM images, and phase analyses
were examined with XRD analysis. The results showed that the use of CW negatively affected the fresh state properties
and rheological parameters of cementitious systems. However, CW addition decreased the 1-, 7-, and 28-day compressive
strength. Only a slight increase was observed in the strength of mixtures containing 5 and 7% CW at 56 days.