Deformation and Compression Behaviour of a Cement–Bentonite Slurry for Groundwater Control Applications

Abstract

Cement bentonite (CB) barriers are selfsupporting, low permeability, structures used to retard groundwater flow and as such strength and hydraulic conductivity parameters are often stipulated when developing the mixtures. This paper reports an investigation into the deformation and compression behaviour of a CB containing ground granulated blastfurnace slag using the unconfined compressive strength apparatus, triaxial (undrained, unconsolidated) and oedometer. Samples were also exposed to drying and rewetting to investigate possible response to changes in environmental conditions. Cracking was observed prior to peak stress suggesting that the hydraulic conductivity of a barrier may be adversely affected before the shear strength is reached in undrained conditions. The compression response of CB indicates the presence of a threshold stress; once exceeded the magnitude of settlements are significantly greater than those encountered below this threshold. If a barrier experiences localised changes in loading conditions then there is the potential for damage from induced differential settlements; thus it is recommended that the threshold stress should also be considered at the design stage in addition to strength and hydraulic conductivity requirements. The response of the material exposed to drying-rewetting was unexpected and requires further investigation to determine how a barrier will respond to changing environmental conditions.

Monitoring drying and wetting of a cement bentonite mixture with Electrical Resistivity Tomography

“…These cracks were claimed to extend 2 meters below the current phreatic line and they were supposed to be related to the shrinkage caused by drying. Preliminary laboratory tests in [7] support the same conclusions. Interestingly, samples enriched with slab or fly ash seem to show worst performances upon drying than pure cement-bentonite mixtures.…”

SEBS-Polymer-Modified Slag–Cement–Bentonite for Resilient Slurry Walls

“…The traditional composition of the slurry consists of Portland ordinary cement (OPC) and sodium bentonite [3,4]. Recently, supplementary cementitious materials, including fly ash and ground granulated blast-furnace slag (GGBS), manufactured from a by-product of the iron-making industry, have become a more sustainable cement substitute [5][6][7]. Improved workability, increased strength, reduced permeability, alkali silica reaction mitigation and improved resistance to chemical attack can all be reasonably expected when fly ash and slag are used as supplementary cementitious materials.…”

A Conceptual Model and Evaluating Experiments for Studying the Effect of Soil Deformation on Its Permeability

“…Green et al [4] reviewed the effects of various types of soil deformation on hydraulic conductivity in order to study the agricultural management practices such as tillage and reconsolidation and wheel-track soil compaction. Yeo et al [5], Berilgen et al [6], Fan et al [7], and Royal et al [8] conducted some experiments to investigate the permeability changes of slurry materials due to loading or compression occurred in the cutoff walls, cut-off barriers, and storing contaminant soils. Bryant et al [9] investigated the permeability changes due to the consolidation of fine-grained marine sediments in various depths and introduced empirical relations to estimate the permeability from the void ratio.…”

“…Most researchers had studied the effect of soil compression or consolidation on the permeability through studying void ratio changes on the hydraulic conductivity. is group of researchers often studied one-dimensional compression type of deformation by using the oedometer apparatus or similar devices that have rigid wall cells [5][6][7][8][9][16][17][18][19][20][21][22][23][24][25][26]. In addition, some researchers studied axial compression with lateral free walls using either a triaxial compression device or compression cell with flexible walls [1,3,[27][28][29].…”