Abstract:
This study aims to evaluate the effect of partially replacing cement with recycled cement
powder (RC), derived from improperly stored and prehydrated cement that was activated
thermally, on the properties of mortars. Replacement percentages of up to 50% were tested to
assess their influence on workability, setting times, mechanical strength, bulk density,
capillary absorption, and durability to acid attack.
The results show that activated recycled cement causes a moderate delay in setting times
and a progressive reduction in mechanical strength with increasing substitution percentages,
particularly at early ages. However, low replacement levels (up to 15%) allow for acceptable
mechanical performance to be maintained. Mixes containing up to 25% RC exhibited lower
capillary absorption and comparable or even better resistance to acid attack compared to the
control mix, suggesting potentially improved durability. Therefore, the use of thermally
activated prehydrated cement appears to be a promising approach, provided that low
replacement levels (≤15%) are used to ensure satisfactory mechanical performance and
durability
