Sand Replacement by Fine Recycled Concrete Aggregates as an Approach for Sustainable Cementitious Materials

Waste management and conservation of natural resources are highly discussed topics today. If these subjects are investigated closer, using tools such as Environmental Product Declaration or Live Cycle Assessment, exact numbers considering the CO2 production or amount of produced construction and demolition waste (CDW) can be gained. Despite the existence of those techniques and the promotion of recycling, people are skeptical, or scared, to use recycled building materials. The research focuses on recycled concrete aggregates (F-RCA), which can replace natural aggregates (NA) in concrete production. An urgent need for solutions is approaching fast and many countries, especially islands, lacking capacity in CDW landfill and start to have a shortage of NA resources. Another favourable fact for higher utilization of F-RCA is an approaching lack of sand world-wide. Experimental work is focused on the evaluation of properties of various RCA fraction 0–4 mm, the design of two different series of mixes with replacement ratio 0, 20, 40 and 100% of NA by F-RCA. The rheological properties of fresh mortar and the properties of hardened concrete are examined. Our assumption of higher water absorption and a greater fines content of F-RCA was validated in some cases. Despite this fact, rheological properties of all mixes varied only slightly, and compressive strength differed by 7%. In the second series was recorded significant compressive strength drop of the mix with 100% replacement ratio. Overall it can be concluded that replacement ratio up to 40% has no negative influence on fresh nor hardened properties.