TY - JOUR
T1 - Application of coal fly ash in pavement subgrade stabilisation
T2 - a review
AU - Zimar, Z.
AU - Robert, D.
AU - Zhou, A.
AU - Giustozzi, F.
AU - Setunge, S.
AU - Kodikara, J.
N1 - Funding Information:
This research work is part of a research project (Project No IH18.01.5) sponsored by the SPARC Hub in the Department of Civil Engineering, Monash University , funded by the Australian Research Council (ARC) Industrial Transformation Research Hub (ITRH) Scheme (Project ID: IH180100010 ). The financial and in-kind support of ARRB, RMIT University and Monash University are gratefully acknowledged.
Publisher Copyright:
© 2022 Elsevier Ltd
PY - 2022/6/15
Y1 - 2022/6/15
N2 - Expansive clays are found in many countries worldwide, and they exhibit inherent volume change during the seasonal moisture variation causing cracks, heaves, and damages to the overlying pavements. Chemical stabilisation is one of the most used approaches to treat the expansive clay subgrades. Cement, Lime and Fly ash are the most commonly used stabilisers, in which fly is cheaper and a by-product obtained from the coal power plant. This paper reviews fly ash stabilisation on various clay types, including low plasticity clays, high plasticity clays, silty clays, organic clays, and peats. The review begins with the properties of fly ash, followed by the characteristics of fly ash stabilised subgrades. The micro-level mechanism, physical, mechanical, and hydraulic characteristics of stabilised pavements are presented graphically for the Class C, and F fly ashes. The micro-level studies reveal that the pozzolanic reaction is stronger than the cation exchange during the fly ash stabilisation. The unconfined compressive strength (UCS), California bearing ratio (CBR) and resilient modulus (Mr) increased with the fly ash addition and curing time for most soft soils except peat clays. Based on the mechanical and hydraulic characteristics, using 15% class C fly ash with 7 days of curing is recommended for optimum performance. Although few research studies confirm that the leachate limit of stabilised soil is within the acceptable limit, further studies are required to investigate the uptake of heavy metals and other certain carcinogenic contaminants. This study will provide key information for researchers and Engineers on the selection of fly ash stabilisation measures for expansive subgrades.
AB - Expansive clays are found in many countries worldwide, and they exhibit inherent volume change during the seasonal moisture variation causing cracks, heaves, and damages to the overlying pavements. Chemical stabilisation is one of the most used approaches to treat the expansive clay subgrades. Cement, Lime and Fly ash are the most commonly used stabilisers, in which fly is cheaper and a by-product obtained from the coal power plant. This paper reviews fly ash stabilisation on various clay types, including low plasticity clays, high plasticity clays, silty clays, organic clays, and peats. The review begins with the properties of fly ash, followed by the characteristics of fly ash stabilised subgrades. The micro-level mechanism, physical, mechanical, and hydraulic characteristics of stabilised pavements are presented graphically for the Class C, and F fly ashes. The micro-level studies reveal that the pozzolanic reaction is stronger than the cation exchange during the fly ash stabilisation. The unconfined compressive strength (UCS), California bearing ratio (CBR) and resilient modulus (Mr) increased with the fly ash addition and curing time for most soft soils except peat clays. Based on the mechanical and hydraulic characteristics, using 15% class C fly ash with 7 days of curing is recommended for optimum performance. Although few research studies confirm that the leachate limit of stabilised soil is within the acceptable limit, further studies are required to investigate the uptake of heavy metals and other certain carcinogenic contaminants. This study will provide key information for researchers and Engineers on the selection of fly ash stabilisation measures for expansive subgrades.
KW - Class C
KW - Class F
KW - Clay
KW - Expansive soil
KW - Fly ash
KW - Pavement
KW - Stabilisation
KW - Subgrade
UR - http://www.scopus.com/inward/record.url?scp=85127172949&partnerID=8YFLogxK
U2 - 10.1016/j.jenvman.2022.114926
DO - 10.1016/j.jenvman.2022.114926
M3 - Review Article
C2 - 35364515
AN - SCOPUS:85127172949
VL - 312
JO - Journal of Environmental Management
JF - Journal of Environmental Management
SN - 0301-4797
M1 - 114926
ER -