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Historically, the primary applications of volcanic ash were attributed to its physical traits, such as the fine particle size, angularity, friability, and light color, which made it ideal for use as an abrasive and a topping for bituminous road surfaces. Recent years have seen a growing interest in the chemical and pyrochemical properties of volcanic ash. This ash serves as an alkaline aluminum silicate flux in ceramics and as a pozzolanic additive in cement for concrete mixtures. In the United States, the volume of volcanic ash used in abrasives significantly surpassed that employed as a cement aggregate and pozzolanic admixture, at a ratio of eight to one. Although the two major uses were nearly balanced, the quantity utilized in cement was nearly 4.5 times that in abrasive applications. The most substantial application of pumicite or volcanic ash in concrete occurs on the West Coast, with Kansas using only small quantities for this purpose, which do not reflect in the state production statistics. Since commercial production in Kansas mostly caters to abrasive needs, annual tonnage figures for these uses are readily available. The earliest record of Kansas production dates back to a total of 23,804 tons. Production peaked at 51,907 tons in a specified year, remaining relatively steady for the following years. Reported outputs fluctuated between 35,385 tons and 49,760 tons within the subsequent years, showing an average production of 41,953 tons over 17 years. Following a nearly average year of 39,215 tons, production dipped to 23,659 tons but rebounded to 47,484 tons afterward, exceeding the prior average. However, since that time, production has sharply declined. Note that these statistics only reflect commercial output, and it is likely that the tonnage processed by the State Highway Department far exceeds the amount mined by commercial producers. We estimate that over 25,000 tons have been sourced from a single deposit by the Highway Department for black-top road application.

Abrasives

Volcanic ash has been utilized as an abrasive in the United States for approximately 50 years. In the year 1955, the entire production of 885 tons in the country was derived from Nebraska. By 1957, the U.S. Geological Survey noted volcanic ash mining in Kansas; however, production figures were classified under miscellaneous items. A few years later, Kansas recorded 23,804 tons of output, predominantly used for abrasive applications.

Due to its fineness, angularity, and moderate hardness (between 5.5 and 6.0 on the Mohs scale), volcanic ash makes an excellent polishing, scouring, and cleansing agent. A significant proportion of the ash utilized as an abrasive is incorporated into scouring compounds like Old Dutch Cleanser, which traditionally comprised volcanic ash mixed with minimal amounts of soap powder or detergents. Volcanic ash is also featured in mechanics paste soap, abrasive hand soaps, and rubber erasers. Extremely fine ash is integrated into some toothpaste formulations and minus-200-mesh ash has been employed in polishing plate glass. In scenarios where powdered pumice is typically appropriate, volcanic ash could be a viable substitute. Applications include polishing metals, wood, and varnished wood finishes, alongside other uses such as polishing powders for bone, celluloid, hard rubber, and dental tape.

The processing of volcanic ash for these abrasive uses generally involves minimal preparation, usually restricted to drying and the screening out of coarser particles. This is feasible due to the naturally fine qualities of the ash. Screen analyses indicate that approximately 93.6 percent passes through a 100-mesh sieve, while around 76.3 percent exceeds the 200-mesh tolerance. Notably, minus-200-mesh material represents over 80 percent in 34 out of 96 samples analyzed. The median particle size from subsieve analyses averages 34 microns, effectively less than 400-mesh. Some applications utilize air classification, especially when finer grades of 200 mesh or less are required. While volcanic ash isn't often ground to achieve a smaller particle size, it can be easily processed using dry grinding methods in ball or pebble mills.

Ceramics

Volcanic ash, referred to as pumicite, consists of tiny volcanic glass shards that resemble a frit comprising primarily feldspar and quartz. Surprisingly, this material has not been extensively explored by ceramic professionals. The ceramics laboratory at the State Geological Survey conducted various experiments with volcanic ash in ceramic glazes and bodies, summarized briefly in reports by Plummer. Prior to these investigations, research regarding the ceramic applications of volcanic ash in the U.S. was limited. Notable findings were documented by Preston regarding volcanic ash in glass batches. The research published by Plummer prompted similar studies reported by Worcester in the Journal of the Canadian Ceramic Society, which examined Canadian volcanic ash in ceramic compositions and glazes, producing results akin to those observed in Kansas with the Work projects by Carey further validated these findings. In recent years, additional tests combining volcanic ash glazes with ceramic bodies were performed and are pending publication in a Geological Survey bulletin.

The Kansas volcanic ash possesses a lower fusion temperature compared to feldspar, with pyrometric cone equivalents ranging from cone 4 to cone 10, yielding an average of 8 to 9 values (or 2300°F to 2390°F). The tested samples of Kansas volcanic ash range from cone 06 to cone 4 in pyrometric equivalency, with a general average hovering around cone 03 to 01 (approx. 2020°F to 2100°F). This variance confers a distinct economic advantage on volcanic ash, permitting its use in ceramic arts at lower, preferred temperatures.

Ceramic Glazes

The chemical composition across various Kansas volcanic ash deposits is highly consistent, as noted in an analysis of 54 samples. Variations primarily stem from contaminants such as quartz, calcite, and clay.

A consistent volcanic ash deposit in Lincoln County (LV-1) has been subject to numerous glaze and ceramic body tests due to its accessibility and representative chemical composition. The composition of this ash is detailed below:

Chemical composition of LV-1 volcanic ash Silica (SiO2) 72.51 percent Alumina (Al2O3) 11.55 percent Iron oxide (Fe2O3) 1.21 percent Titanium oxide (TiO2) 0.54 percent Calcium oxide (CaO) 0.68 percent Magnesium oxide (MgO) 0.07 percent Potassium oxide (K2O) 7.84 percent

The molecular formula or weight ratio of the various oxide groups in this volcanic ash can be summarized as follows:

K2O 0. Al2O3 0. SiO2 9. Na2O 0. Fe2O3 0. TiO2 0. CaO 0.         MgO 0.        

The formula weight of the above materials is 794.30. In contrast, feldspar from Keystone, South Dakota, has the molecular formula detailed below:

K2O 0.751 Al2O3 1. SiO2 6.230 Na2O 0.231 Fe2O3 0.     CaO 0.018        

The molecular weight of this feldspar stands at 577.72. Owing to the higher silica to alumina ratio in volcanic ash compared to feldspar, a direct one-to-one replacement cannot occur. Roughly 100 parts of volcanic ash can substitute for 70 parts of feldspar and 30 parts of potters flint. A more precise method for substitution is illustrated in Table 5, which is based on vetted molecular ratios of oxides in both materials and calls for the removal of feldspar, flint, and whiting, while adding volcanic ash and ball clay.

Table 5.--Required volcanic ash and clay for precise replacement of feldspar, flint, and whiting in glazes or ceramic bodies. Parts per hundred in the total glaze batch, by weight.

Take out Add Feldspar Flint Whiting Volcanic ash O-38-4 clay 5.0 2.57 0.09 7.41 0.51 10.0 5.14 0.18 14.83 1.01 15.0 7.71 0.28 22.24 1.52 20.0 10.28 0.37 29.66 2.02 25.0 12.85 0.46 37.07 2.53 30.0 15.42 0.55 44.49 3.03 35.0 17.99 0.64 51.90 3.54 40.0 20.56 0.74 59.32 4.05 45.0 23.13 0.83 66.73 4.55 50.0 25.70 0.92 74.15 5.06 55.0 28.27 1.01 81.56 5.56 60.0 30.84 1.10 88.98 6.07 65.26 33.54 1.20 96.78 6.60

The calculations were executed for Keystone feldspar, Lincoln County volcanic ash (LV-1), and a Kansas ball clay (O-38-4) that contains 64.67 percent silica, 22.38 percent alumina, 1.58 percent iron oxide, 1.32 percent titanium oxide, 0.27 percent calcium oxide, 0.66 percent magnesium oxide, 1.11 percent potassium oxide, and 0.55 percent sodium oxide. Any comparable ball clay could substitute. It is essential to note that extracting a total of 100 percent feldspar, flint, and whiting from a glaze or body necessitates adding a total of 103.38 percent of volcanic ash and clay in replacement. This consideration arises from the higher percentage of inactive components present in both ash and clay. Although such high ratios are seldom applied in glazes and ceramic bodies, we have successfully created a usable glaze containing 95 percent volcanic ash. Generally, the proportion of ash in a glaze batch does not surpass 75 percent, while ceramic bodies rarely benefit from more than a 25 percent addition of volcanic ash.

Below are a few examples of proficient volcanic ash glazes illustrating the diversity in compositions possible, with one glaze maturing within the cone 02-1 range:

Eagle-Picher lead silicate 31.4 percent LV-1 volcanic ash 25.0 Keystone (S.D.) feldspar 2.8 Colemanite 5.5 Whiting 2.1 Zinc oxide 3.2 Barium carbonate 4.2 O-38-4 clay 8.5 Flint 5.2 Zircopax (zirconium silicate) 12.1

This glaze was combined with 5 percent commercial yellow stain to yield an attractive shade of yellow, while excluding the stain produces an opaque glaze effect.

A straightforward glaze within the cone 04 to cone 10 range comprises the following:

Volcanic ash 70 parts by weight Colemanite 30 parts by weight Bentonite 5 parts by weight

This glaze exhibits a somewhat muddy color due to its iron oxide content. Adding 5 percent whiting enhances the glaze's transparency. If the glaze is intended as a base for colored surfaces, including 5 percent of an opacifier such as zirconium silicate yields a warm white finish appropriate for such use.

A successful raw lead glaze used across numerous body types at cone 07 to cone 04 ranges is given below. The glaze is likely applicable across a broader spectrum:

Red lead 35.2 percent Volcanic ash 51.4 Whiting 8.4 Zinc oxide 1.0 Florida kaolin 4.0

A high-temperature glaze that has achieved remarkable results on siliceous bodies is outlined below. This glaze was utilized successfully at cone 7 and cone 9 but should also perform within a range from cone 6 to 10. Colored glazes can be produced by simply adding the appropriate oxides or stains:

Volcanic ash 39.9 percent Whiting 8.4 Magnesium carbonate 7.3 Barium carbonate 4.9 Ball clay (O-38-4) 28.5 Flint 10.0

Volcanic ash glazes are actively utilized by several pottery studios within the state and are also employed in various educational institutions. The primary advantage of incorporating volcanic ash is its cost-effectiveness, alongside additional beneficial traits such as an extended firing range and a softer color palette than those obtained through conventional materials. Kansas potteries successfully market the use of volcanic ash glazes, attracting customers.

Ceramic Bodies

Replacing conventional materials in ceramic glazes with volcanic ash shows minimal differences in the final glaze, although a reduction in firing temperature may occur due to the unexpectedly low fusion temperature of the ash. However, outcomes in ceramic bodies are less predictable. Generally, the results are more advantageous than anticipated, with numerous test bodies incorporating diverse clays and shales demonstrating how 7 to 15 percent addition of volcanic ash reduces vitrification temperatures, expands the firing range for matured bodies, and enhances rigidity at maximum temperatures. Utilizing volcanic ash leads to fuel conservation while reducing kiln loss due to narrower temperature range requirements, allowing the ware to support its weight effectively at peak applied kiln temperatures. Reactions vary significantly among different clays and shales; some materials see minimal improvements beyond reduced firing temperatures. Identifiable benefits of volcanic ash additions are noted in sewer pipe bodies, resulting in a project supported by a group of clay plant operators sent to Ohio State University's Engineering Experiment Station. J. O. Everhart, the lead research professor, reported marked advantages linked to volcanic ash use. In a summary letter accompanying the report, Everhart remarked on the stabilizing influence volcanic ash imparts to mixes, particularly valuable for local clay and shale compositions with short firing ranges. Similar successful outcomes with the incorporation of volcanic ash in a Texas sewer pipe plant have been reported by F. K. Pence from the University of Texas.

Notably similar outcomes arise from introducing volcanic ash into pottery or whiteware bodies. In these instances, the ash's higher iron content slightly darkens the fired body color. With additions ranging from 10 to 25 percent, the firing temperature is lowered, enabling artists with limited maximum temperatures to create hard-fired products that do not craze or leak. Overall casting properties of pottery bodies improve when volcanic ash is included, attributed largely to particle size and shape. At least one Kansas pottery facility has adopted volcanic ash in the casting body, successfully producing vitrified ware at cone 4.

Glass and Vitreous Enamels

Similar to its role in ceramic glazes, volcanic ash serves an equivalent function in glass and vitreous enamels. The iron oxide content, typically around 1.5 percent, limits volcanic ash usage in these products. Nonetheless, volcanic ash has been considered as an ingredient in fiberglass batches and foam glass, where slight color modifications are not primary concerns. Addressing disintegration issues linked to platinum dies by the iron in the ash would be required if utilized in fiberglass production.

One of the major sanitary ware manufacturers conducted laboratory trials examining volcanic ash within vitreous enamel mixtures. Reports indicated that ash-integrated cream and ivory-colored enamels proved slightly superior to feldspar-based counterparts, although shipping ash to their plants negated any potential cost-saving benefits.

Lightweight Aggregates and Cellular Blocks

The Oklahoma Geological Survey has examined the viability of producing cellular products akin to Foamglas using a lightweight aggregate created from bloated individual volcanic ash particles. Production of the cellular product, coined "pumicell" by the Geological Survey, involves heating volcanic ash in refractory molds, yielding a glass embodying small isolated air-filled cells. The result features high insulation properties and can be sawed or nailed. The bulk density of this product ranges from 45 to 90 pounds per cubic foot, contrasting with a genuine specific gravity between 2.34 and 2.48, which translates to a density of 146 to 155 pounds per cubic foot, showing up to 56.8 percent closed cells within the overall volume.

Preliminary experiments to induce bloating in Kansas volcanic ash within laboratories at the State Geological Survey suggest similar bloating traits to Oklahoma's materials.

The lightweight aggregate developed at the Oklahoma Geological Survey appears reminiscent of expanded perlite, despite differing methods for "popping" the volcanic ash used versus those applied for perlite. Expansion involves introducing a stream of volcanic ash into the air intake of an inspirator-type gas burner. This product comprises glass beads housing one or more bubbles, with bulk specific gravities spanning from 0.22 to 0.088, culminating in bulk densities of 5.5 to 13.7 pounds per cubic foot. Materials composed of this substance exhibit resistance to heat, sound, and electrical transmission, eligible for use in insulation and acoustical plasters, wallboard, lightweight blocks, and slabs.

The State Geological Survey in Kansas has trialed the formulation of a similar expanded or "popped" product utilizing the region's Pleistocene volcanic ash. Attempts to create an equivalent product with Pliocene ash were unsuccessful, but further testing is scheduled, with outcomes anticipated for publication in a forthcoming Survey bulletin.

A comparable expanded volcanic ash product resembling perlite is being produced in Hutchinson, Kansas, operating under the trademark Mira-Colite. Specific production methods remain unspecified.

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Concrete

Dating back approximately 1,800 years, Romans created cement using two volumes of volcanic ash and one volume of slaked lime. Seaworks constructed from this pozzolanic cement remain functional today. This Roman or pozzolanic cement sets exceptionally slowly when made with slaked lime. Modern-day pozzolanic cements, utilizing Portland cement instead, circumvent this issue, gaining interest due to their resistance to seawater disintegration and their capacity to mitigate reactions from specific siliceous aggregates with alkaline compounds in Portland cement. Volcanic ash provides inherent cementing properties while acting as a fine aggregate to fill voids between fine sand aggregates and cement. In concrete formulations, up to 50 percent of the cement can be substituted with volcanic ash, although lower proportions are more standard.

As noted by Barr, the primary application for volcanic ash (pumicite) lies in concrete aggregates, with its role as an admixture garnering growing attention. In nearly equal distributions, volcanic ash and pumice were produced for abrasive applications and used in concrete. In a particular year, a substantial 4.5 times more of these materials were utilized in concrete compared to their abrasive counterparts.

Miscellaneous Uses

Volcanic ash comprises the primary ingredient in certain sweeping compounds and acts as insulation for water and steam pipes, boiler lagging, and loose-fill insulation in walls and ceilings. It also functions as a filler or diluent in paints and serves as a carrier for insecticides. The purification and clarification of oils through filtration have seen volcanic ash deployed, likely in its partially altered form.

Recently, the State Highway Department has extracted substantial quantities of volcanic ash from at least eight pits in Kansas, predominantly for top dressing on "black top" or bituminous roadways. It is reasonable to assume that Kansas utilizes more volcanic ash for these purposes than any other state.

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Web version Jan. . Original publication date Feb. 15, .
URL=http://www.kgs.ku.edu/Publications/Bulletins/96/06_uses.html Kansas Geological Survey, Kansas Volcanic Ash Resources Comments to Web version Jan. . Original publication date Feb. 15, .URL=http://www.kgs.ku.edu/Publications/Bulletins/96/06_uses.html