June 7-10, 2009
Shikoku Electric Power Co., Inc. has developed the technology to manufacture a brand name “Finash” about 12 years ago, by sorting and classifying coal ash generated in coal fired power plants. “Finash” is highly functional fly ash (HFA) is produced by removing irregular coarse particles. It is important for the production of HFA to minimize the variation in quality of coal ash with sophisticated classification technique and extracting good-quality spherical fine particles. The specific surface of HFA is more than 5000 cm2/g. It is now widely utilized as concrete admixture for general civil engineering structures and buildings in Japan.
When highly functional fly ash (HFA) is used as shotcrete admixture to substitute for fine aggregate of 100kg/m3, the shotcrete has the advantages of decreasing the amount of dust and rebound during spraying operation, improving the hardened properties and durability of concrete, etc. Therefore, it has been applied in many tunnels by NATM.
In order to verify the high performance of shotcrete with HFA, firstly it was carried out the spray tests at the model tunnel using the shotcrete with HFA having the specific surface of 5530cm2/g compared with normal shotcrete without fly ash and shotcrete with the lower fly ash (class 4th-FA) having the specific surface of 1770cm2/g. Secondly it was carried out the spray tests at an actual road tunnel using the shotcrete with HFA having the specific surface of 5450cm2/g compared with normal shotcrete without fly ash and shotcrete with the conventional dust reducing agent of 0.1% mass of the cement.
This paper discusses about the various characteristics such as construction placement (dust concentration and rebound rate), hardened properties and durability (compressive strength, accelerating neutralization depth and dry shrinkage) on theses several sorts of shotcrete.
Kunihiro Yuno, Chikanori Hashimoto, Mitsuhiro Ishii, and Hiroyuki Mizuguchi, "CONSTRUCTION PLACEMENT, HARDENED PROPERTIES AND DURABILITY OF SHOTCRETE WITH HIGHLY FUNCTIONAL FLY ASH" in "Shotcrete for Underground Support XI", Felix Amberg, M.o.S. ETHZ, SIA, Switzerland; Knut F Garshol, BASF Construction Chemicals, LLF, USA Eds, ECI Symposium Series, (2009). http://dc.engconfintl.org/shotcrete/18