Cementitious, Pozzolanic And Filler Materials For DSM Binders

Abstract

Deep Soil Mix (DSM) is a proven method of ground improvement for deeper underlying soft soil layers which are otherwise impractical to reach using conventional shallow soil stabilization and replacement methods. The predominant binder materials used are Ordinary Portland cement (OPC) and Lime (CaO) but negative effects to the environment from manufacture and increasing construction cost have prompted research into alternative materials. This review identifies pozzolans and filler materials as possible supplements or partial substitutes for better results. The DSM method and binder reaction processes during treated soil strength development are outlined and effectiveness of different pozzolans (Fly Ash, Silica Fume, Ground Granulated Blast Furnace Slag, Rice Husk Ash, Kaolin, and Metakaolin) and filler materials (e.g. fine sand) discussed together with their influence factors. With many pozzolans, a clear optimum dosage is observed where improved strength peaks. Aluminosilicate pozzolans perform better over siliceous pozzolans with Metakaolin (MK) identified as the most effective pozzolan for enhancing compressive strength. Up to date research results on these materials are compiled. MK blended cements are readily available and can be readily applied for initial field tests. Treated soil strength may be regulated with addition of filler materials to further reduce reliance on cement.

Relationship between Phase Composition and Mechanical Properties of Peat Soils Stabilized Using Oil Shale Ash and Pozzolanic Additive

“…In order to facilitate the hardening of the soil-binder mixture, pozzolanic agents like silica fume, waterglass, alumino-siliceous fly ash, granulated blast furnace slag, ground glass, bentonite, kaolin, or other siliceous and alumino-siliceous materials can be used [3,9,10,13]. Soluble calcium or aluminum salts such as CaCl 2 or Al 2 (SO 4 ) 3 can be added as supplementary Ca and Al sources [9,10,13,14]. Peat soils contain a high percentage of organic material and few to no solid mineral particles.…”

“…Peat soils contain a high percentage of organic material and few to no solid mineral particles. Therefore, within the mass stabilization process the addition of granular filler materials, such as sand or inert construction wastes (e.g., recycled asphalt pavement or crushed bricks), to the mixture allows cementitious compounds to carry out a pozzolanic reaction, or from the hydration of cement to bind the particles together, enhancing the strength of the stabilized peat [12,14,15].…”

“…Adsorption of insoluble calcium and magnesium humates onto the binder particle surfaces, and additive materials interfere with the hydration of calcium silicates and aluminates, which slows down pozzolanic reactions. Moreover, fulvic acids selectively associate with aluminum-bearing mineral particles, inhibiting the hydration of aluminates and impeding crystallization hydration products [14]. Leaching of organic acids from peat may reduce the pH of the mixture, decreasing the solubility of siliceous species and therefore hindering formation of calcium (aluminum) silicate hydrate (C(A)SH) gels [7,16].…”

“…A high ratio of organic to mineral in peat implies a high water-retention capacity and a high moisture content, which results in a high water-to-binder ratio that, in turn, limits any increase in the strength of the mixture. In the case of peat soils, this combination of a high organic content, a lack of pozzolanic and solid inert particles, an acidic media (primarily from humic and fulvic acids), and a high water-to-solids ratio impedes the efficient hydration of cement and hinders any subsequent increase in the compressive strength of the soils [14]. The compressive strength and content of hydration products in the soil-cement mixture decreases until a certain threshold value of humic matter is achieved, beyond which the additional humic matter has a limited effect on the mixture's compressive strength [18].…”

Morphology and chemical composition of mineral matter present in fly ashes of bituminous coal and lignite

“…To a slightly lesser extent, ashes are used in the production of special ceramics or thermal insulation materials (Erol et al 2008b;Stoch 2015). Expansion of the road network and highways created greater opportunities for the use of ashes in engineering and road works (Gawlicki, Wons 2012;Swamy, Das 2012;Wong et al 2020). Due to the high content of aluminium and silicon, fly ash can also be a valuable raw material for the synthesis of zeolites.…”