Deep stabilization has been used as a subgrade strengthening technique for a long time. The stabilization is based on the addition of hydraulical binders such as lime or cement, which are mixed to the subgrade in-situ or ex-situ and reacts with soil particles to improve the bearing capacity of the soil. Especially in-situ stabilization of low quality soils such as peat, silt, clay, mud etc. can prevent the need of large mass exchange and bring significant cost savings and CO2 reductions. However, the relatively high cement price (average ~60-100 $ per ton1) and CO2 emissions caused by cement production has driven the research to find substitutive binder materials.
Various industrial by-products including various fly ashes, gypsum waste, lime waste, steel industry slags etc. have been tested as a cement replacement material in deep stabilization2,3,4. However, in practice the cement is basically always part of the binder material while the industrial waste fractions alone are not reactive enough. This study aims on combining and activating of different industrial waste fractions to produce completely industrial by-product based binder material. The activation of fly ash is carried out by mechanical grinding with DESI 11 laboratory scale pin mill. Produced binder mixture was tested and compared to cement containing binders by preparing test specimens and measuring unconfined compressive strength after 28 and 90 days. The soil materials for stabilization studies were mixture of fibre sludge and silt, silt and silty mud. The soil materials were selected from planned construction site in Hiedanranta, Tampere, where the desired compression strength was around 80-100 kPa.
As a result, the various completely waste fraction based binder recipes were found even for high organic content soils which are difficult to stabilize. The needed total binder amount was higher with by-product based binders compared to cement, however, the binder cost and CO2 emissions can still be lower compared to cement.
Works cited:
1 CW Group (2017). Global Cement Trade Price Report 4Q 2016 CW. CemWeek Magazine, [online] (36). Available at: https://www.cwgrp.com/publications/cemweek-magazine/item/101-cemweek-magazine-january-february-2017 [Accessed 13 Dec. 2017].
2 EuroSoilStab (2002). Development of Design and Construction Methods to Stabilize Soft Organic Soils, Design Guide Soft Soil Stabilization, Industrial & Materials Technologies Programme (Brite- EuRam III), European Commission, CT97-0351, Project No. BE 96-3177
3 Forsman, J., Jyrävä, H., Lahtinen, P., Niemelin, T., Hyvönen, I (2015). Mass stabilization manual
4 Do, T., M., Kim, Y., S., Dang, Q., D., (2017). Stabilization of marine dredged sediment using lime-fly ash-red mud-gypsum binder, 19th Conference ICSMGE, Seoul, South Korea
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