Influence of Recycled Fine Aggregate on the Properties of Self-Leveling Mortars

The use of recycled aggregates as raw materials in mortar and concrete can not only achieve the effective use of renewable resources but also achieve environmental friendliness. In this paper, the influence of recycled fine aggregate (RFA) content and additives on fluidity, fluidity loss, strength, drying shrinkage, and hardened surface roughness of self-leveling mortar (SLM) was investigated. The surface roughness of SLM was characterized by fractal dimension, and the main influence factors of the surface roughness were discussed. Results showed that the strength of SLM decreased with the addition of RFA content. When the RFA content was 100 %, the 1-day and 28-day compressive strength of SLM decreased by 19.2 % and 12.4 % respectively, and the 1-day flexural strength decreased by 16.7 %, but the 28-day flexural strength changed little. With the increase of RFA content in SLM, more polycarboxylic acid superplasticizer was required in order to achieve the appropriate workability. Meanwhile, a high content of RFA led to an increased fluidity loss of SLM within 30 min. The addition of silica fume enhanced the early strength of SLM, fly ash decreased the drying shrinkage, and slag improved fluidity. The size and gradation of RFA had a significant effect on the surface roughness. The addition of RFA reduced the surface roughness of SLM. The surface fractal dimension of SLM mixed with 25 % RFA was the lowest. The addition of silica fume further reduced the surface roughness of the SLM. The mortar with different surface roughness can be prepared by adjusting the content and gradation of RFA and the fluidity of mortar.