Abstract:
Both base and subbase layers of rigid pavements are currently constructed
with concrete based on ordinary Portland cement (OPC). The OPC manufacturing
process is heavily carbon intensive and has severe negative impacts towards the
environment and sustainability. Geopolymer as an alternative is promising, in terms
of both performance and sustainability. This study used waste clay bricks (WCB)
blended with fly ash and slag precursors to produce one-part geopolymer binderswith
the aim of replacing OPC in pavement concrete. One-part binders were prepared by
combining activators and the precursor at a 1:9 ratio by weight.Within the precursor,
fly ash content was varied at 0%, 10%, 20% and 30% by weight. In the remaining
precursor, WCB was replaced with slag at 20%, 40%, 60% and 80% replacements.
All blends of WCB with fly ash and slag showed significantly higher strengths than
their unblended counterparts. The highest 28-day compressive strength of 92 MPa
was recorded for the sample with 30% fly ash and with 80% replacement of WCB
with slag on the remaining precursor. Additionally, the WCB based geopolymer
binders showed a high early strength development, achieving more than 50% of its
28-day compressive strength within 72 h. Aggregates were then introduced to the
selected binders to prepare geopolymer concrete (GPC). The compressive strength
of GPC samples was recorded after 28 days of aging. Initial GPC trial mixes were
able to achieve compressive strengths up to 41 MPa, demonstrating the feasibility of
using WCB based binders for developing pavement concretes.
