Shear thickening intensity of self-compacting concretes containing rounded lightweight aggregates

•Recycling of fly ash as lightweight aggregate (LWA) were achieved by pelletization.•Natural aggregates were replaced with LWAs in making self-compacting concrete (SCC).•Seventeen SCCs were produced to have a fixed slump flow diameter.•The High-Range-Water-Reducing Admixture decreased with the increasing level of LWA.•Increasing amount of LWA made SCCs less susceptible to shear thickening.

This paper investigates the rheological behavior of self compacting concrete (SCC) made by replacing normal-weight aggregates (NWAs) with cold bonded lightweight fly ash aggregates (LWAs). Dry powder mixture of 90% fly ash and 10% Portland cement by weight was pelletized through moistening in a revolving tilted pan at ambient temperature to produce lightweight fly ash aggregates which were then cured for 28 days. Seventeen concrete mixtures were produced to have a fixed slump flow by using varying amounts of High-Range-Water-Reducing-Admixture (HRWRA). Increasing replacement level for fine and/or coarse LWA simultaneously decreased density and plastic viscosity which made the concretes less susceptible to shear thickening. Meanwhile, the increasing percentage of LWA used reduced the HRWRA needed for gaining constant workability. With full replacement by lightweight fly ash aggregates, 25% reduction was achieved in the fresh density of self-compacting concrete produced.