Usage of Wood Fly Ash in Stabilization of Unbound Pavement Layers and Soils

Abstract

Modification and stabilization of road structure unbound layers has extensively been studied both at laboratory and field for decades. The most commonly used binders for soil modification and stabilization are cement and quicklime (CaO), but alternative pozzolans and their mixtures are of economical, technical and environmental interest. This study presents soil stabilization with wood fly ash (WFA) at laboratory. Natural sand (Sa), Sa mixtures with 10% and 20% WFA were compacted at optimal water content according to Standard Proctor test LVS EN 13286-2:2012, and California bearing ratio (CBR) tested according to LVS EN 13286-47:2012 for cured samples after 96 hours immersed in water with 2 kg surcharge and after 7 days sealed simultaneously. At the same time also Immediate bearing index was determined for natural soil and their mixture with 10% WFA. Results showed 3.79 times enhancement in CBR values Sa after 7 days curing, justifying that WFA is valuable material for hydraulically bound mixtures.

Pulp and Paper Mill Fly Ash: A Review

“…Field monitoring showed significant increases in stiffness and decreases in permeability over time, which were attributed to the hydration of ash. The self-cementitious property of PPFA arising from its high calcium and aluminosilicate contents can result in substantial improvements in the strength and volume change properties of expansive subgrades and foundation soils [20][21][22]105]. Due to very low permeability, PPFA-based geopolymers can also be successfully employed as hydraulic barriers, including for cover for landfills [106,107].…”

“…In order to withstand extreme conditions, the bacteria may enter a dormant stage, thereby decreasing the microbial population and diversity and ultimately disturbing the ecological balance. PPFA and value-added materials also have multifunctional engineering applications, such as supplementary cementitious material (SCM) in concrete systems, aggregate in pavement construction, binder for soil stabilization, and adsorbent for the immobilization of toxic heavy metals [15][16][17][18][19][20][21][22][23]. Based on a statistical survey conducted on the management and utilization of boiler ashes generated at Canadian pulp and paper mills, it was reported that more than 50% of ash is landfilled, 20-25% is used as a soil amendment (direct application or compost), and less than 20% is used for other beneficial applications such as the construction of embankment fills, the stabilization of pavement layers, and the solidification of wastes.…”

Possibilities for using bioash in road construction

“…In base layers it would be possible to use fine fly ash and coarser bottom ash due to two mechanisms: improvement of bearing capacity through mechanical stabilization and improved grading, or due to bioash action as a hydraulic binder. Laboratory testing of wood ash and ash produced by combustion of waste from paper mills reveal satisfactory values, and the use of such ash is significant [39][40][41]. However, contradictory results were obtained by field tests related to stabilization of layers of the existing (often forest) roads [30,41,42].…”

“…However, contradictory results were obtained by field tests related to stabilization of layers of the existing (often forest) roads [30,41,42]. Stabilization effect of the addition of 10 % and 20 % of wood ash to mixtures with sand was examined by Škels et al [39]. Their results revealed a multiple increase in the CBR value in both stabilized mixtures, without significant swelling.…”

Laboratory Evaluation of the Properties of Asphalt Mixture with Wood Ash Filler

“…The chemical composition of BA, especially the content of CaO and pozzolan, indicates the possibility of partial or complete replacement of traditional binders, cement, and lime during the stabilization of the subgrade materials with a lower load bearing capacity [ 10 , 11 , 12 , 13 , 14 , 15 ], in the base layers of pavement structures [ 16 , 17 , 18 , 19 , 20 ] or in concretes [ 21 , 22 ]. With the absence of binding properties, BA can be used as a replacement for a mineral filler or aggregate in asphalt mixtures, a filler in concretes, and as a replacement for smaller aggregate in base layers of pavement structures, depending on the fraction of ash.…”