Soil-Resistance Tests

Soiling with particulate soil or fatty soils containing particulate matter occurs by transfer from a soiled surface onto a clean one. For example, upholstery fabrics 

Within a limited range of fiber characteristics, both of the above mechanical devices are capable of producing results which correlate with those obtained by traffic soiling of carpets on the floor (Fig. 13.9). 

A carpet soiling test developed by Lamb [63] uses two drums in contact with each other. The lower drum is coated with a rubber sneaker-sole material and the carpet specimen are mounted on the upper drum (Fig. 13.10). The lower drum is driven by a motor at a low speed (5 ipm). The pressure on the carpet is controlled by a weight at the end of the lever arm. Soil is supplied by a conveyor belt (Fig. 13.11). A blade that rubs against the carpet helps to distribute the soil evenly before the soil reaches the compression zone. Soil resistance is evaluated using a Hunter ColorQuest or a similar chromameter. 

Although the test is reproducible, it does not present the carpet to soil in a normal position. The carpet on the drum is not flat, like a carpet on the floor, but is bent on the drum and the carpet pile is held in a downward position while being soiled. Hence, the carpet pile is more open than during actual use on the floor. This may make a difference when the concentration of the soil-resistant fluoropolymer is higher at the top of the pile than at the bottom. 

The existing laboratory soiling tests, in spite of their increasing mechanical sophistication, do not predict soil resistance of the full range of commercial car- 

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Ground rods or stainless steel soil resistivity test pins driven into soil... 

The in-service cable plant is tested to establish the presence or absence of stray direct currents, the galvanic corrosion effect of "foreign plants, the corrosivity of local environmental conditions, and the corrosive effect of long cells formed by the changes in the environment. The corrosion of the in-place plant is detected through potential surve5fs, current tests, soil resistivity tests, redox potential tests, and pH tests. 

Figure 5.9 Wenner four-pin soil resistivity test setup.

Stain-resist finishes must be tested for their resistance to nonionic stains as well, including natural-colored substances found in food (Fig. 14.1). However, the resistance to traffic soiling is the most important factor governing the appearance of the stain-resistant carpet, with the added requirement that the stain-resist finish must withstand foot traffic. Soil-resistance tests are described in Chapter 13 and, in addition, stain resistance is tested before and after subjecting the carpet to floor traffic. The durability of the stain-resist finish to shampooing is another important requirement. 

Resistance to Microorganisms and Insects. Resistance of triacetate to microorganisms, based on soil-burial tests, is high, approaching that of polyester, acryUc, and nylon fibers. Sod-burial test results on acetate, triacetate, and cotton are shown in Figure 8. Neither acetate nor triacetate fiber is readdy attacked by moths or carpet beedes. 

Soil resistivity The role of soil in the electrical circuitry of corrosion is now apparent. Thus the conductivity of the soil represents an important parameter. Soil resistivity has probably been more widely used than any other test procedure. Opinions of experts vary somewhat as to the actual values in terms of ohm centimetres which relate to metal-loss rates. The extended study of the US Bureau of Standards presents a mass of data with soil-resistivity values given. A weakness of the resistivity procedure is that it neither indicates variations in aeration and pH of the soil, nor microbial activity in terms of coating deterioration or corrosion under anaerobic conditions. Furthermore, as shown by Costanzo rainfall fluctuations markedly affect readings. Despite its short comings, however, this procedure represents a valuable survey method. Scott points out the value of multiple data and the statistical nature of the resistivity readings as related to corrosion rates (see also Chapter 10). 

Other tests to determine bacterial-notably sulphate reducing-activity, soil resistivity, pH, redox potential, etc., will provide valuable data to supplement the results obtained with test specimens. A useful account of some of these was given in Reference 336 and they are also discussed in Sections 2.6 and 10.7. A scheme for assessment of corrosivity of soils based on some of the above parameters has been given by Tiller . 

Direct shear test of soils under consolidated drained conditions pH of soil for use in corrosion testing Field measurement of soil resistivity using the Wenner four-electrode method Optimum S03 in portland cement... 

EN 12225, Geotextiles and geotextile-related products. Method for determining the microbiological resistance by a soil burial test, 2000. 

Loblolly pine modified by 1,6-diisocyanatohexane (HDI) was found to be resistant to attack by G. trabeum at a WPG of 26 % (Chen, 1992c). At 26 % WPG, 6 % of bonded chemical was lost during a 12-week soil decay test. When moist wood was used for reaction, the HDI reacted mainly to form ureas and biurets. It was stated that the decay resistance of HDI modified wood was probably due to the inability of the modified cell wall to absorb sufficient amounts of water to support decay. Although wood reacted with chloro-sulphonyl isocyanate lost only 1.3 % mass when exposed to G. trabeum in a decay test, it was reported that 50 % of the bonded chemical was lost in this test. 

In a study of the effect of heat treatment upon the durability of spruce and larch heated at 200 °C in a vacuum, both spruce and larch exhibited good resistance to decay by G. trabeum, but treated spruce exhibited a decay mass loss of 9 % compared to 1 % with larch against C. puteana in an 8-week mini soil block test (Rep etal, 2004). 

Hesistance lo Microorganisms and Insects. Resistance of triacetate to microorganisms, based on soil-burial tests, is high, approaching that of polyester, acrylic, and nylon fibers. 

Douglas-fir, birch, southern pine, and sweetgum blocks were treated with 1% aqueous ammonia or sodium hydroxide for various times, temperatures, and pressures (9). These samples were submitted to soil-block tests with two brown-rot fungi Poria monticola (Madison 698) and Lentinus lepideus (Madison 534) and two white-rot fungi Polyporus versicolor (Coriolus versicolor) (Madison 697) and P. anceps (F 784-5) as well as outside exposure tests (10). In the soil-block tests, the treated wood was resistant to the two brown rotters, but was not resistant to the two white rotters. In the outdoor stake tests, the average lifetime was 3.5 years while untreated controls had an average lifetime of 3.6 years. The outdoor tests show that there is no increase in rot resistance by this treatment. 

C. Heat Treatments. Several woods have been heated under wet and dry heating conditions to determine the effect heat has on the decay resistance of these woods. Alaska-cedar, Atlantic white-cedar, bald cypress, Douglas-fir, mahogany, redwood, white oak, Sitka spruce, and western redcedar were heated under dry conditions or wet conditions at temperatures of 80-180°C for varying lengths of time. Boyce (11) found that dry heat at 100°C or steam heat at 120°C for 20 minutes had no effect on the decay resistance. Similar results were observed by Scheffer and Eslyn (12) in soil-block tests with Lenzites trabea for the heated softwoods and Polyporus versicolor for the heated hardwoods. 

It is of interest that veneer-faced low-density particleboards made from acetylated veneers and acetylated core particles showed excellent dimensional stability in both liquid water and humidity tests and were resistant to attack by fungi in an 8-week soil block test [57]. Furthermore, during the 150-day bending-creep test, the totally acetylated boards showed no strength or weight loss during exposure to T. palustris. 

Detailed resistance tests against decay fungi and termites have been conducted on epoxide-treated wood. Brown-rot fungi, L. lepideus and G. tra-beum, yielded 44.2% and 62.9% weight loss (WL) of control southern pine, respectively, after 12-week soil block tests. 

Successful application of cathodic protection depends upon the selection, design, installation, and maintenance of the system. Before designing the cathodic protection systems, adequate field data must be collected, analyzed, and evaluated. Nature and conditions of the soil are reflected by field measurements like soil resistance, hydrogen ion activity (pH), and the redox potential. To understand the nature of the pipeline, potential measurements, coating resistance, and meaningful design current requirement tests must be conducted. 

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