Utilization of cold bonded fly ash lightweight fine aggregates as a partial substitution of natural fine aggregate in self-compacting mortars

• Lightweight fine aggregates (LWFAs) were manufactured via pelletization technique.
• LWFAs were replaced with natural one at various levels up to 100%.
• Self-compacting mortars (SCMs) were produced at fixed slump flow diameter.
• The superplasticizer needed decreased with increasing percentage of LWFAs.
• Increasing amount of LWFAs improved fresh state but adversely affected hardened state of SCMs.

In this study, lightweight fly ash fine aggregates (LWFAs) were used as a partial replacement of natural fine aggregate to investigate the fresh and hardened states of self-compacting mortars (SCMs). For this, a powder mixture of 90% fly ash (FA) and 10% Portland cement (PC) by weight were pelletized in a tilted pan through a cold-bonded agglomeration process. Thereafter, a total of five mixtures of SCMs were prepared in which natural fine aggregate was replaced by LWFA partially started from 0% to 100% by 25% increment. Subsequently, tests carried out on the fresh mortar involved mini-slump flow, mini-V-funnel flow time and viscosity while the hardened properties of SCMs were evaluated using the compressive strength, ultrasonic pulse velocity, gas permeability and sorptivity tests. The hardened characteristics of SCMs were determined at different ages up to 56 days. It was observed that the increased percentage of LWFA improved the workability and the flowability of SCMs. On the other hand, the strength and permeability properties of SCMs had a negative effect due to the substitution of LWFAs for natural fine aggregate, especially at higher replacement level.