Building on Sub-Arctic Soil: Geopolymerization of Muskeg to a Densified Load-Bearing Composite

Abstract

The marshy water-saturated soil typical of the sub-Arctic represents a considerable impediment to the construction of roads, thereby greatly hindering human habitation and geological excavation. Muskeg, the native water-laden topsoil characteristic of the North American sub-Arctic, represents a particularly vexing challenge for road construction. Muskeg must either be entirely excavated, or for direct construction on muskeg, a mix of partial excavation and gradual compaction with the strategic placement of filling materials must be performed. Here, we demonstrate a novel and entirely reversible geopolymerization method for reinforcing muskeg with wood fibers derived from native vegetation with the addition of inorganic silicate precursors and without the addition of extraneous metal precursors. A continuous siloxane network is formed that links together the muskeg, wood fibers, and added silicates yielding a load-bearing and low-subsidence composite. The geopolymerization approach developed here, based on catalyzed formation of a siloxane network with further incorporation of cellulose, allows for an increase of density as well as compressive strength while reducing the compressibility of the composite.

Incorporation of Hydroxyethylcellulose-Functionalized Halloysite as a Means of Decreasing the Thermal Conductivity of Oilwell Cement

“…Figure 6 shows Fourier transform infrared (FTIR) spectroscopy data acquired for modified cement composites prepared with hydroxyethylcellulose-modified HNTs. The unmodified cement specimen displays prominent vibrational modes at 865, 1050, and 1415 cm −1 , respectively, which can be assigned to ν 2 CO 3 2- stretching, Si-O-Si stretching, and ν 3 CO 3 2- stretching modes, respectively 35 , 36 ; the modes arise from the CaCO 3 and calcium silicate (C 3 S and C 2 S) phases that are the primary constituents of cement. Less intense modes are discernible at 2854 −1 and 2921 cm −1 and can be assigned to CH 2 stretching modes.…”

In situ Resource Utilization and Reconfiguration of Soils Into Construction Materials for the Additive Manufacturing of Buildings

“…A continuous siloxane network is formed that links together the muskeg, wood fibers, and added silicates yielding a load-bearing and low-subsidence composite. Where fibrous peat has compressive strengths on the order of 3.5-11 kPa, our geopolymerized muskeg samples attain compressive strengths as high as 33 MPa upon cross-linking with sodium silicate and reinforcement with an interpenetrating network of mulch fibers (Waetzig et al, 2017). Notably, we have further illustrated that the siloxane framework is readily dissolved by base treatment, allowing for restoration of the soil to its native condition as represented in Figure 2A (Waetzig et al, 2017).…”

“…As an example of the practical feasibility of harvesting local soils and plant fibers to build load-bearing structures, we have recently reported a method for preparing a densified composite material suitable for use in roadworks from muskeg fibers and wood chips sourced from Northern Alberta that are cross-linked using soluble silicates and functionalized cellulose (Waetzig et al, 2017). The marshy soil in this sub-arctic region limits road transport to peak winters when the top soil is frozen solid; transportation on solid pack ice is associated with tremendous cost and risk.…”

Separation of Viscous Oil Emulsions Using Three-Dimensional Nanotetrapodal ZnO Membranes

“…The deposition of a conformal amorphous SiO 2 shell that forms siloxane bonds both to the steel surfaces as well as to hydroxyl groups on the ZnO surfaces helps to adhere the ZnO tetrapods to the stainless steel mesh surfaces. The SiO 2 overlayer is grown by spray coating a mixture of TEOS and NH 4 OH onto the mesh substrates, thereby facilitating hydrolysis and condensation reactions. , The TEOS and NH 4 OH loading described in Materials and Methods yields a rating of 5B as per the American Society for Testing of Materials (ASTM) Standard D3359 for a test specimen wherein the tetrapods are adhered to a planar steel substrate. , ASTM Standard D2197 tests furthermore indicate a scrape adhesion strength of 450–550 g. Thermogravimetric analyses for ZnO nanotetrapods indicate that they retain their structural integrity up to 900 °C, while the addition of an amorphous SiO 2 layer demonstrates only a small weight loss of 3.8% between 160 and 325 °C as reported in previous work . The weight loss is attributed to the loss of residual water and hydroxyl groups, leading to a greater degree of cross-linking and compaction of the silica matrix.…”

“…120 °C. Next, a modified Stöber method was used to deposit a layer of amorphous SiO 2 using tetraethylorthosilicate (TEOS) as the precursor in order to covalently link the ZnO tetrapods to the underlying stainless steel mesh. , The SiO 2 layer prevents sloughing and endows mechanical resilience to the 3D nanotextured membranes. The solution spray coated on the stainless-steel mesh comprised a mixture of 80 vol % ethanol (99.5+%, Koptec), 18.5 vol % deionized water (ρ = 18.2 MΩ·cm –1 ), 1 vol % of an aqueous solution of 28–30% NH 4 OH, and 0.5 vol % TEOS (99.999+% metals basis, Alfa Aesar).…”