Influence of clay in limestone fillers for self-compacting cement based composites

High workability together with a good resistance to segregation is needed for cement based composites, specifically fresh self-compacting mortars (SCM); in this prospect, the amount of coarse materials has to be reduced and replaced by fine material. Several limestone fillers are here compared and analysed. These by-products are issued from different industrial sectors, such as the aggregate and lime production industry (quarrying operations) and the ornamental stones industry (sawing operations).Particular attention has been paid to clay content, as consistency of fresh mortars was varying, while other physical characteristics like granulometry remained the same. Relationship between the physico-chemical properties of the fillers and the properties of fresh and hardened mortars are brought forward. Even if it may affect fresh properties of mortars, results clearly show that clay type and content has minor influence than limestone filler itself.

Research highlights
► The water requirement of limestone fillers is mainly affected by their swelling clay content and may be directly correlated to MBA and SS, BET values.
► Some limited effects on 7-day compressive strength are observed.
► No clear specific effect of clayey material content on filler activity index is noticed.
► No determined influence on initial setting time is pointed out.
► Capillary suction and water absorption increase when limestone fillers are incorporated into mortars. Clay content doesn’t seem to have any effect.