Investigation of the influence of fine recycled sand on the setting behaviour of cement when used as supplementary cementitious material (SCM)

The building materials industry makes a major contribution to greenhouse gases emitted each year, particularly by the cement clinker production. Therefore, aim should be maintain an increased part of material from demolition sites in cycle. use fine (< 2mm) waste concrete has so far proved problematic due water demand and loss compressive strength. One approach is recycled powder (RCP) as supplementary cementitious (SCM). Demolition used this study been obtained discarded railroad sleepers pre-crushed sand 4 mm). was subjected mechanical thermal activation process before use, then ground particle size <63 μm fired at different temperatures (750°C, 800°C, 850°C, 900°C). convert parts hydrated C-S-H structure back into reactive silicate phases through firing process. They can contribute again hydration when material. thermally treated - called SCM wasexamined for their physical chemical properties. Subsequently, 10 20 Vol.-% were replaced binder mixture, respectively. In first step, binders documented. Ultrasonic methods investigate stiffening setting behaviour binders. decisive factor here proportion chemically bound mixtures. Finally, properties investigated mortar tests. Acceptable strengths achieved compared reference (mortar mixture without substitution). At glance, it seems possible SCM.