Factors Affecting Engineering Properties of Microfine Cement Grouted Sands
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ORIGINAL PAPER
Factors Affecting Engineering Properties of Microfine Cement Grouted Sands I. N. Markou • A. I. Droudakis
Received: 14 September 2012 / Accepted: 22 February 2013 / Published online: 14 March 2013 Ó Springer Science+Business Media Dordrecht 2013
Abstract An experimental investigation was conducted in order to evaluate the influence of distance from the injection point and of parameters pertinent to the cement, the suspension and the sand on the effectiveness of microfine cement grouts. Three different cement types, each at three different gradations having nominal maximum grain sizes of 100, 20 and 10 lm, were used. Grouting effectiveness was evaluated by injecting suspensions with water to cement (W/C) ratios of 1, 2 and 3, by weight, into five uniform sand fractions with different grain sizes and eight composite sands with different gradations, using a specially constructed apparatus. Unconfined compression and permeability tests were conducted on the resulting grouted sand specimens, after curing for 28 and 90 days. Microfine cement grouted sands obtained unconfined compression strength values of up to 14.9 MPa and permeability coefficients as low as 1.3 9 10-6 cm/s or by up to 5 orders of magnitude lower than those of clean sands. The W/C ratio and the bleed capacity of suspensions as well as the effective grain size and the permeability coefficient of sands are very important parameters, since they affect substantially the grouted sand properties and are correlated satisfactorily with them. The strength and permeability
I. N. Markou (&) A. I. Droudakis Soil Mechanics and Foundation Engineering Laboratory, Department of Civil Engineering, Democritus University of Thrace, 12 Vas. Sofias str., 67100 Xanthi, Greece e-mail: [email protected]
of grouted sands can increase, decrease or remain constant with distance from the injection point depending on the easiness of suspension penetration into the sands. The improvement of grouted sand properties with increasing distance from the injection point is consistent with the observed increase of the cement content of grouted sands. Keywords Grouting Microfine cements Laboratory investigation Grouted sands Permeability Strength
1 Introduction The safe construction and operation of many structures frequently requires improvement of the mechanical properties and behavior of soils by permeation grouting using either suspensions or chemical solutions. Suspensions have lower cost and are harmless to the environment but can not be injected into soils with gradations finer than coarse sands. Chemical solutions can be injected in fine sands or coarse silts but are more expensive and, some of them pose a health and environmental hazard. Therefore, a number of ‘‘microfine’’ or ‘‘ultrafine’’ cements has been developed and marketed in the last decades and the improvement of soil properties by means of microfine cement grouting has been practiced, in order to extent the application range of ordinary cement grouts and to
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