Presentation and Assessment of Clay Influence on Engineering Parameters of Cement-Treated
Clayey Mixtures

 

Evangelos I. Stavridakis

B.Sc., M.Sc., Ph.D., F.G.S., Lecturer, Laboratory of Soil Mechanics and Foundation Engineering Geotechnical Engineering Division, Department of Civil Engineering,
Aristotle University of Thessaloniki, Thesssaloniki, Greece
e-mail: stavrid@civil.auth.gr

ABSTRACT

The improvement of physical and engineering soil properties by cement protect the natural environment. Through cement - stabilization the plasticity of a problematic soil (swelling or soft) is reduced while its compressive strength, load bearing properties and durability are improved. While the conventional cement stabilization methods are used mainly for surface treatment the use of cement has recently been extended at greater depth in which cement columns were installed to act as a type of soil reinforcement (deep cement soil mixing). Cement stabilization (surface or deep) methods have a basic target to find the most efficient and economical method of mixing cement with soil so that the properties of a problematic soil become more like the properties of a soft rock.

The clay mineral composition of a soil is one of the most dominant factors determining the chemical, physical and engineering properties of this soil. Mineralogy of bonding [type of clay (bentonite kaolin) cement] of cementing material (cement or other cementing additive) is an important property that controls strength and durability. The efficacy of cement stabilization is a function of portion and mineral type (active or inactive). Study and prediction of potential deterioration in durability due to climatic wetting and drying (i.e. problem of durability in cement treated soil due to fluctuation of water table) could be made by using the slake durability test developed by Franklin. Also this test contributes to the improvement of engineering properties of soils by relating the cement stabilization parameters (percentage of cement, compaction, curing time) and composition of clayey soils with the potential bonds developed between cement and soil grains (Stavridakis, 2003b).

Triangular and three dimensional diagrams were prepared on the basis of unconfined compressive strength, slaking and liquid limit experimental results of cement stabilized bentonite kaolin sand mixtures. These diagrams classify the cement stabilized clay mixtures in durable and non durable and also define areas of strength, slaking and liquid limit of clay mixtures for efficient cement stabilization. Finally empirical relationships between unconfined compressive strength and slaking indicate the strong influence of bentonite and sand on these geotechnical parameters.

KEYWORDS: cement, clay stabilization, strength, slaking, bentonite.

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