Grouting gels

A total of 2500 bags of cement, 1200 bags of fly ash and 43,000 gal of chemical grout were used. For most of the job, pressures were kept below 0.5psi per foot of overburden, and pumping rates were under 4gpm. Chemical grout gel times were between 10 and 15 min. 

Injection of silica-rich solutions acts in the same direction as the before-mentioned procedures of chemical stabilization, namely by fixation of metals within a favourable pH-range. Grouting gels, in addition, by filling the pore space, will significantly reduce permeability for dissolved pollutants. 

Polyacrylamide gel Polyacrylamide gels Polyacrylamide grout Polyacrylamide pAM) P o ly acryl arm d es... 

Soil conditioners are materials that measurably improve the physical characteristics of the soil as a plant growth medium. Typical uses include erosion control, prevention of surface sealing, and improvement of water infiltration and drainage. Many natural materials such as peat and gypsum are used alone or in combination with synthetics for soil conditioning. This article is concerned with synthetic soil conditioners, many of which are introduced as polymeric systems similar to the gels and foams formed in situ by chemical grouts. 

Silicate Grouts. Sodium silicate [1344-09-8] h.3.s been most commonly used in the United States. Its properties include specific gravity, 1.40 viscosity, 206 mPa-s(=cP) at 20°C Si02 Na20 = 3.22. Reaction of sodium silicate solutions with acids, polyvalent cations, such organic compounds as formamide, or their mixtures, can lead to gel formation at rates, which depend on the quantity of acid or other reagent(s) used. 

Syneresis of sodium silicate gels may occur under some conditions, eg, in pure gels or coarse formations. Cement grouting should then precede chemical grouting. Leaching that results from dissolution under water-saturated conditions may be eliminated by use of proper reagent proportions. 

Helmut Orth first reported the use of laetones to accelerate phenolic resole cure in 1957 [161]. A year later, Orth discovered that this effect could be extended to aliphatic esters as well [162], Despite the dramatic nature of the acceleration seen, Orth s observations were not applied in industry for a decade. In 1967, Sumitomo and BASF applied esters to soil grouting and wood uses [133,163, 164]. Neither of these applications were commercially successful, however, and commercial success would not occur until 1980 when Borden introduced ester-cured sand binders for foundry [165]. This technology was highly successful in UK and spread to the US, where it was applied immediately to foundry in 1981 and eventually to wood products in 1990 [119,166-173]. Esters are capable of reducing the gel times of resoles from several weeks to less than 30 s at room temperature. Both gaseous and liquid esters are applicable [119,166]. 

L.2.7 Gel time and peak exothermic temperature of epoxy grouts shall be determined by ASTM D 2471. Peak exothermic temperature shall not exceed 45°C (110°F) when a specimen 15 cm (6 in.) diameter x 30 cm (12 in.) high is used. Gel time shall be at least 150 minutes. 

MSE Technology Applications, Inc. (MSE-TA), has developed a viscous barrier technology using materials such as colloidal siUca, polysiloxane, and polybutane. These materials, also known as grouts, are injected into the soil matrix displacing pore water and filling pore spaces. When the materials gel, they form an impermeable barrier that is both nonreactive and unaffected by filtration. This technology is still in development and is not commercially available. 

In Chapter 5, the discussion of flow of grout through soils has been expanded. In Chapters 6 and 7, sections have been added concerning instrumentation and its relationships to the use of short gel times in the field. 

Around 1960, Diamond Alkali Company entered the market with a single-shot silicate-based grout trade named SIROC, which offered high strength or low viscosity, each coupled with gel time control. At about this time Terra Firma, a dried precatalyzed lignosulfonate, also entered the market. 

The mechanical properties of the various grouts that are important factors in the selection of a grout for a specific job include permanence, penetrability and strength. Similarly, the chemical properties include permanence, gel time control, sensitivity, and toxicity, and the economic factors include availability and cost. These properties are all discussed in detail in the sections that follow, using data from specific materials whenever such data will give a better understanding of chemical grouts. 

The viscosities of four different grouts, as measured by a Stormer viscosimeter, are shown in Fig. 10.5. Viscosities, of course, vary with percent (dissolved) solids, and the chart is presented in that fashion. The usable viscosities of the various materials depend on the minimum desirable field concentration of solids. Thus, while it is obviously possible to work with a 20% sodium silicate solution in the Joosten process (a viscosity of between 3 and 4 cP), a gel would not form at that low a concentration, and it would be misleading to claim a 4 cP viscosity. In a similar fashion, other silicate formulations can be used to give either low viscosity of high strength, and it is misleading to list those values simultaneously as if they were the properties of the same fluid. 

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