The Effect of Clay Pozzolana-Cement-Composite on the Strength Development of a Hydraulic Backfill
The study sought to investigate the potential application of clay pozzolana as a supplement for cement in hydraulic backfill, using classified tailings from AngloGold Ashanti, Obuasi Mine. The percentage of the Portland cement that could be substituted with the clay pozzolana to produce backfill with best strength was determined. 10%, 25%, 30%, 35% and 40% of the ordinary Portland cement were replaced with clay pozzolana and then mixed with tailings and water. The slurry produced was cast into cylindrical specimen of 50mm diameter by 120mm high and tested for compressive strength after curing for 7, 14, 21, 28 and 56 days. The results indicate that, clay pozzolana-cement composite has potential for application in hydraulic back fill production without increased risk to safety and dilution. It was noted that hydraulic backfill with 10%, 25%, 30% and 35% of the ordinary portland cement replaced with clay pozzolana had strengths greater than those obtained for ordinary portland cement alone. Ten percent (10%) pozzolana content gave the maximum strength followed by 25% pozzolana. It is recommended that for safety and economic considerations, the cement content should be replaced by 25% pozzolana in the production of backfills.
Keywords: Hydraulic Backfill, Portland Cement, Clay Pozzolana, Unconfined Compressive Strength
American Society for Testing and Materials (2000). Annual book of ASTM standards: Part 14-C 618, Standard specification for fly ash and raw or calcined natural pozzolana for use as a mineral admixture in Portland cement concrete, ASTM, Philadelphia, USA, pp: 355-358.
AngloGold Ashanti, Obuasi Mine Backfill operations manual (2012), Obuasi internal operations document, pp: 1-16.
AngloGold Ashanti, Obuasi Mine Metallurgical Service Department manual, (2005), Obuasi Internal operations document, pp: 1-29.
Bediako M.A., Gawu, S.K.Y. and Adjaottor, A.A. (2011). Selected mechanical properties of mortar used for masonry incorporating artificial pozzolana. In Modern methods and advances in structural engineering and construction. Sai on Cheung et al (eds), pp: 569-574
Benzaazoua M., Belem T. and Bussie`re B. (2002). Chemical factors that influence the performance of mine sulphidic paste backfill, Cement and Concrete Research Vol. 32, pp: 1133-1144.
Benzaazoua, M., Fall M. and Belem T. (2004). A contribution to understanding the hardening process of cemented paste fill; Special edition of Minerals Engineering, Vol. 17, pp: 141-152.
Dodd W. E., (2000). Fly ash use in pressurized grout remote backfilling of abandoned underground mines in North Dakota, Paper presented at the Kansas Department of Transport, Abandoned underground mine workshop, Kansas City, MO, USA., pp: 1-5.
European Committee for Standardization (2000). Composition, specifications and conformity criteria for common cements, The European Standard, EN 197-1, CEN, 2000, Brussels. pp: 1-29.
Grice T. (1998). Underground mining with Backfill. The 2nd Annual Summit-Mine tailing disposal systems, Brisbane, Australia, 24-25 November 1998. pp: 1-14.
Masniyom M., (2009). Systematic Selection and Application of Backfill in Underground Mines. PhD thesis submitted to the Faculty of Earth Science, Geotechnical and Civil, Technical University Bergakadimie Freiberg, Germany, pp: 1-168.
Mertens G., Snellings R., Van Balen K., Bicer-Simsir B., Verlooy P. and Elsen J. (2008). Pozzolanic reactions of common natural zeolites with lime and parameters affecting their reactivity, Elsevier Ltd, pp: 233-240.
Ostnor, T., (2007). Alternative pozzolans as supplementary cementitious material in concrete. A report on review of available literature on the pozzolanic materials: calcined clays, light weight aggregate fines, rice husk ash, nano silica and ground glass as alternatives to the more common fly ash, slag, metakaoline and silica fume, Trondheim Norway, pp: 1-25.
Shnorhokian S. (2009). Development of Quantitative Accelerated Sulphate attack test for Mine Backfill. Thesis submitted to McGill University in partial fulfilment of the requirements of the degree of Doctorate of Philosophy, Montreal, Canada, pp: 13-217.
Thevarasa A., Perampalam V. and Selvaratnam M. (1979). Some studies on pozzolanic cement. Journal of Science council, Sri Lanka, Vol.7, No.1, pp: 57-63.
Yao Y., Cui Z. and Wu R. (2012). Development and Challenges on Mining Backfill Technology, Journal of Materials Science Research; Vol. 1, No. 4, pp: 73-78.
Yuemin, F., Suhong, Y., Zhiyun, W., Jingyu, Z. (1999). Activation of fly ash and its effects on cement properties. Cement and Concrete Research, Vol. 29, Issue 4, pp: 467-472.