Ground subsidence frequently occurs due to the poorly-compacted backfill materials for underground structures. As an alternative to the soil compaction method, Controlled Low Strength Material(CLSM) which consists of fine aggregate, cement, fly ash, water, and other materials has been developed. The...
Ground subsidence frequently occurs due to the poorly-compacted backfill materials for underground structures. As an alternative to the soil compaction method, Controlled Low Strength Material(CLSM) which consists of fine aggregate, cement, fly ash, water, and other materials has been developed. The purpose of this study is to investigate the engineering characteristics and applicability of CLSM according to the various types of fly ash. For this purpose, the physical and chemical characteristics of fly ash are analyzed, and six types of fly ash are used for the specimen preparation. To evaluate the fundamental physical properties, air contents, unit weights, and volume changes of the specimens are measured. For the fluidity and compressive strength, flow test and unconfined compressive strength test are performed. To monitor the hardening characteristics, setting time test and shear wave measurement are carried out. The experimental study shows that fly ash with spherical particle shape, high fineness, high silicon dioxide(SiO2), and low loss on ignition(LOI) is adequate for better fluidity and compressive strength characteristics. After testing, the correlation between vicat needle penetration and shear wave velocity is obtained with high coefficient of determination. The shear wave measurement technique can be used to identify early-age properties. It is judged that fly ash with physical and chemical properties of fineness higher than 3,000 cm2/g, SiO2 higher than 50%, and LOI less than 4% is considered to be suitable for field applicability of CLSM. These results can be the basis for quality standards and field applications of fly ash used in CLSM.
Ground subsidence frequently occurs due to the poorly-compacted backfill materials for underground structures. As an alternative to the soil compaction method, Controlled Low Strength Material(CLSM) which consists of fine aggregate, cement, fly ash, water, and other materials has been developed. The purpose of this study is to investigate the engineering characteristics and applicability of CLSM according to the various types of fly ash. For this purpose, the physical and chemical characteristics of fly ash are analyzed, and six types of fly ash are used for the specimen preparation. To evaluate the fundamental physical properties, air contents, unit weights, and volume changes of the specimens are measured. For the fluidity and compressive strength, flow test and unconfined compressive strength test are performed. To monitor the hardening characteristics, setting time test and shear wave measurement are carried out. The experimental study shows that fly ash with spherical particle shape, high fineness, high silicon dioxide(SiO2), and low loss on ignition(LOI) is adequate for better fluidity and compressive strength characteristics. After testing, the correlation between vicat needle penetration and shear wave velocity is obtained with high coefficient of determination. The shear wave measurement technique can be used to identify early-age properties. It is judged that fly ash with physical and chemical properties of fineness higher than 3,000 cm2/g, SiO2 higher than 50%, and LOI less than 4% is considered to be suitable for field applicability of CLSM. These results can be the basis for quality standards and field applications of fly ash used in CLSM.
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