Recent Developments in Nanomaterials for Geotechnical and Geoenvironmental Engineering

Abstract

Abstract. Nanotechnology has provided enormous benefits to the industrial and developed world. Most fields of knowledge have been tapping, using, and applying the advantages of nanotechnology to improve systems and living standards. This cannot be said for civil engineering and construction particularly geotechnical engineering. Actually, soil mechanics have been involved with nano scale dimensions and materials for a very long time, i.e. before the term nanotechnology and nanomaterials were coined. From the basic clay structure and the water molecules which give rise to soil plasticity/cohesiveness, geotechnical engineers were exposed to these phenomena since the early days of the subject. Currently, developments in nanotechnology and nanomaterials in geotechnical engineering has been limited to its use as an improvement and clean-up materials. Recent results have shown that the use of a small amount of nanomaterials (<1% of dry weight of the original soil) have resulted in significant change and improvement in soil properties. This is important since efficient use of materials is one of the facets of sustainability related to prolonging the life of our depleting natural resources. Experiences with nano-soil, nano-clay, nano-silica, nano-alumina, nano-magnesium, carbon nanotube and nanofibers, and nano-lime will all be discussed with respect to its use in soil improvement and soil remediation.

Comparative Study between Silica Fume and Nano Silica Fume in Improving the Shear Strength and Collapsibility of Highly Gypseous Soil

“…The average increment in apparent cohesion due to adding SF (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) % varies between (140-310) % in dry soil and (20-40) % in soaked condition. Same results obtained when mixing the gypseous soils with (1-5) % of NSF.…”

“…This cannot be much said for geotechnical engineering. However, geotechnical engineers are amongst the earliest "nanotechnologists" who, in the past, have dealt with materials at Nano sizes and phenomenon which operate at the Nanoscale, [12].…”

Review of the use of nanomaterials in soils for construction of roads

“…Soil stabilization can be done in three ways: physical, mechanical or chemical (see Figure 1), which seek to improve properties such as compressibility, hydraulic conductivity, density and strength; Some of the chemical methods used are heat as a catalyst for curing (lime), the use of lime/cement to manage plasticity and improve soil strength, resin/ polymers as a binder to improve the soil matrix and reduce dust, nano chemical solutions that mixed with water increase soil bearing capacity and reduce plasticity indices [62], [63]; on the other hand, on the mechanical side, in clayey soils, plastics, polymers and fibers (wood, glass, polypropylene) have been used as mechanical reinforcement, which considerably increase the cohesion and the angle of internal friction of the soil; one of the main difficulties in the use of fibers in clays is based on on-site mixing, but with time it has excellent results, At the nano level it was found that electromagnetic forces dominate over gravity forces, so the use of nanofibers in the soil resulted in an improvement in shear strength and thixotropy, in addition they control the liquid limits, plastic limit and lower bulk density due to the appearance of nano pores [64] - [66]. At the University of Kebangsaan Malaysia (UKM) they were able to demonstrate that with the mixture of less than 0.2% of carbon nanofibers (purity greater than 98%, diameters 200 nm and length between 50 and 200 m) in residual soils of sandy-clay composition, it is possible to increase the maximum dry density, The density of the nanofibers is higher than that of the natural soil, however, a decrease in porosity and an increase in the hydraulic conductivity of the soil was also observed [67], [68]. They have even worked on the management of expansion and contraction in residual soils with carbon nanofibers, where they found that volumetric shrinkage stress can be reduced by more than 50%, which qualitatively demonstrated that cracks were reduced [69].…”