Stone chips

SteinabfMlle, m.pl. stone chips, spalls, steinahnlich, a. stone-like, stony. 

Gravel and crushed rock—stone chips— are obtained by quarrying. Some gravels are collected by sea dredging, which destroys marine environments. However, secondary aggregates, such as crushed rubble from demolition works, offer an alternative to newly quarried materials, and make an attractive, durable surface. 

Loose stone Crushed stone chips (top) in a variety of colors and textures—byproducts of the quarrying industry—make an acceptable alternative to quarried gravel or dredged gravel (bottom). A "scree garden" made with such chips or crushed brick waste is an effective way to display alpine plants, avoiding the environmental concerns caused by garden rock features (seep.134). 

Plants from hot, dry environments often also appreciate a layer of gravel or stone chips over the surface of the soil it reflects the heat, and ensures that the bases of the stems stay dry and thus less prone to fungal rots. As a bonus, it will also suppress weeds. For a colorful alternative, use rounded glass chips made from recycled glass. 

Asphalt—mbber is mixed and applied to roadways by several techniques. In one method, mbber and asphalt are mixed at ca 175—220°C for one to two hours. The hot mixture is applied to the roadway and covered with a layer of stone chips to form a chip seal. The mbber cmmb consists of scrap tires ground into particles less than 2 mm in diameter. Rubber-modified asphalt is also used for waterproofing membranes, crack-and-joint sealers, hot-mix binders, and roofing materials. The mbber improves asphalt ductility and increases its softening point. The aggregate adhesive bond is stronger, and the asphalt lasts longer. Production of rubber-modified asphalt has increased from 405 t in 1970 to 27,000 t in 1980 (41). Typically, about 2 t of mbber is used for 1 km of roadway. If it is assumed that asphalt—mbber contains ca 25% mbber and 75% asphalt, the potential demand for scrap mbber would be ca 40,500 t/yr, or ca 2% of the amount available. 

A primer surfacer, composed most often of a polyester to be cross-linked with a blocked isocyanate or melamine cross-linker, is applied next at a dry film thickness of approximately 1.0 mil by conventional spray application. The function of this coating is to provide filling and leveling properties as well as some stone-chip resistance. Cure conditions range from 250 to 325°F for 20 min. 

Certain cargo can shift during transportation if improperly stored, or it may cause structural damage to the ship. These include stone chips and pebbles, some ores and minerals, sands, etc. Some may harden to solids on exposure to moisture. 

Surfacers are mainly produced from low molecular mass polyester resins cross-linked with amino resins. Blocked polyisocyanate resins may also be used for high stone chip resistance. Water-soluble polyester resins are increasingly used for water-thinnable stoving surfacers. Spray and dip paints based on polyester resins are used to coat automobile accessories (e.g., windscreen wipers, axle parts). 

A good example of a natural product combined with a synthetic product to maximize the properties of both is the stone-chipping faced polyester building panel. The chippings, which can be of various sizes and colours, are... 

Chem. Descrip. Fatty acid-modified polyester PU resin (45%) in water/N-methyl pyrrolidone, neutralized with dimethyl ethanolamine Uses Polyester for highly flexible aq. stoving systems, e.g., stone chip-resist. primer surfacers for on-line automotive finishing Features Rec. in combination with water-thinnable amino resins Properties Ylsh./brnsh. cloudy appearance 45 015 nm mean particle size sol. in water, alcohols, glycols, glycol ethers dens. = 1.1 ml (20 C) vise. 200-2000 mPa-s-(23 C) add no. 13 02 pH 7.25 00.75 (1 3 in DW) equiv. wt. = 1417 anionic 4501%NV Bayhydrol PR 135 [Bayer AG]... 

Chem. Descrip. Aqueous of dispersion of a styrene/1,3-butadiene/ac[ylic acid copolymer (50%), ammonia (< 5%), emulsifier Uses Binder for primers, fillers, conosion protection paints, stone chip and underbody protection compds. 

Uses Polyester improving stone chip resist, in automotive OEM base coats... 

In the former category, we are concerned with localized damage to a paint film, exemplified by a stone chip on the body of a motor car. The exposed metal surface, in the case of steel, undergoes the anodic reaction, which will eventually lead to a characteristic rust deposit on the surface ... 

In that test, a mixture of stone chippings and water passes over geotextile samples installed in a rotating drum. The standard test is composed of two abrasion phases at 16 rpm at 40,000 revolutions each, changing direction every 5000 revolutions. If the samples are not degraded after the first 40,000 revolutions (visual inspection), new stone chippings are filled in and the second phase is carried out. If the samples have not been destroyed after 80,000 revolutions, samples are taken and their tensile... 

The former type offered much higher application solids and resistance to mechanical damage (e.g. stone chip resistance), and was used exclusively in commercial transport applications. Acrylics gave superior colour, colour retention and exterior durability, particularly in the area of the up and coming metallic or polychromatic finishes. 

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