National Academies Press: OpenBook

Microsurfacing (2010)

Chapter: Glossary and Abbreviations

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Page 71
Suggested Citation:"Glossary and Abbreviations." National Academies of Sciences, Engineering, and Medicine. 2010. Microsurfacing. Washington, DC: The National Academies Press. doi: 10.17226/14464.
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Suggested Citation:"Glossary and Abbreviations." National Academies of Sciences, Engineering, and Medicine. 2010. Microsurfacing. Washington, DC: The National Academies Press. doi: 10.17226/14464.
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Page 73
Suggested Citation:"Glossary and Abbreviations." National Academies of Sciences, Engineering, and Medicine. 2010. Microsurfacing. Washington, DC: The National Academies Press. doi: 10.17226/14464.
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Suggested Citation:"Glossary and Abbreviations." National Academies of Sciences, Engineering, and Medicine. 2010. Microsurfacing. Washington, DC: The National Academies Press. doi: 10.17226/14464.
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Page 74

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72 The terms found in this glossary came primarily from the International Slurry Surfacing Association’s 2010 edition of its Inspector’s Manual for Slurry Systems. Definitions for terms not contained in this reference were imported from various sources and are noted by “(author year)” as they occur. GLOSSARY Asphalt Emulsion—Defined by the most common type of system in which the asphalt is the dispersed liquid or the internal phase, and water is the dispersing liquid or the exter- nal phase. This is commonly called oil-in-water emulsion. During asphalt emulsion manufacture, the emulsifying agent promotes emulsification and keeps it stable thereafter. Different types of asphalt emulsions are shown in Table 51. Adhesion Agents—These substances improve the degree of wetting of the aggregate by the binder, thus enhancing the adhesion between the binder and aggregate [NCHRP Syn- thesis 340 (2005)]. Aggregate—A granular material, usually crushed and screened to appropriate gradations, that is used as the cover stone in a surface treatment [NCHRP Synthesis 340 (2005)]. Binder—A bituminous material that provides a waterproof seal and also bonds the cover stone to the pavement [NCHRP Synthesis 340 (2005)]. Bleeding—The upward movement of asphalt through the surface treatment. Bleeding, also commonly referred to as flushing, can be identified by dark patches of asphalt form- ing on the surface, most commonly in wheel paths or inter- sections [NCHRP Synthesis 340 (2005)]. Breaking—The initial separation of the water from the emul- sion, which can be detected by a marked color change from brown to black, and often by the release of fairly clear to straw-brown water. This characterizes the point when asphalt droplets begin to re-combine. The results in the depo- sition of the base asphalt on a paved surface and the material can no longer be hand worked. Colloid—Any fine suspension of finely divided particles in a continuous medium. Corrective Maintenance—Maintenance performed once a deficiency occurs in the pavement; that is, loss of friction, moderate to severe rutting, extensive cracking or raveling. Crack Filling—The placement of materials into nonworking cracks to substantially reduce infiltration of water and to reinforce the adjacent pavement. Working cracks are defined as those that experience significant horizontal movements, generally greater than about 2 mm (0.1 in.). Crack filling should be distinguished from crack sealing. Crack Sealing—A maintenance procedure that involves placement of specialized materials into working cracks using unique configurations to reduce the intrusion of incom- pressibles into the crack and to prevent intrusion of water into the underlying pavement layers. Working cracks are defined as those that experience significant horizontal movements. Cure—The entire process of breaking and set until the final mixture of emulsion and aggregate has lost all moisture resulting from evaporation or dehydration. Curing—A slurry system has “cured” when the asphalt par- ticles have re-combined into a continuous film surround- ing the aggregates, and the majority of micro-droplets of water have been removed from the mat through evaporation or chemical reaction. At this point the surface is ready for traffic. It should be noted that final cure (total dehydration) can take periods of from two to four weeks. Edge—The point that the aggregate in a slurry system treat- ment ends. Emulsifier (see Surfactant). Emulsified Binder—A liquid mixture of asphalt binder, water, and an emulsifying agent. Emulsions are either anionic (negatively charged) or cationic (positively charged). Emul- sions are not as sensitive to moisture, inherently contain anti-stripping agents, and require much lower application temperatures than asphalt cements [NCHRP Synthesis 340 (2005)]. Emulsion—Defined as a mixture of two immersible liquids, one of which is dispersed in the other in the form of very fine droplets, usually in the presence of a third component, the surface active agent. Flushing—See definition for bleeding. Ionic Compatibility—Different types of aggregate are better suited to certain binders as a result of electrostatic charges. For sufficient adhesion, the binder and aggregate must have opposite charges. Lump Sum Contract—A contract where the contractor is required to furnish a single sum for the cost of completing the scope of work described in the plans and specifications. The contractor assumes the risk that actual quantities exceed contractor-estimated quantities and is not paid extra if they do [NCHRP Synthesis 340 (2005)]. Macrotexture—Larger irregularities in the road surface (coarse-scale texture) that affects hysteresis. These larger irregularities are associated with voids between stone par- ticles. The magnitude of this component will depend on several factors. The initial macrotexture on a pavement surface will be determined by the size, shape, and grada- tion of coarse aggregates used in pavement construction, as well as the particular construction techniques used in the placement of the pavement surface layer. Macrotexture is also essential in providing escape channels to water in the tire–surface interaction, thus reducing hydroplaning (Noyce et al. 2005). Micro-Surface Emulsion—Polymer-modified emulsions with special chemical compositions enable placement of thick lifts of “slurry.” They are normally cationic with a low pH. GLOSSARY AND ABBREVIATIONS

73 Microtexture—Irregularities in the surfaces of the stone par- ticles (fine-scale texture) that affect adhesion. These irregu- larities are what make the stone particles feel smooth or harsh to the touch. The magnitude of microtexture depends on initial roughness on the aggregate surface and the abil- ity of the aggregate to retain this roughness against the polishing action of traffic (Noyce et al. 2005). Modified Binder—Binder modifiers include polymers, latex, rubber crumb, and anti-stripping agents. Modifiers have proven successful at enhancing flexibility, minimizing bleeding, increasing aggregate retention, and extending the service life of microsurfacing [NCHRP Synthesis 340 (2005)]. Particle Charge Test—The particle charge test is made to identify cationic emulsions. It is performed by immersing a positive electrode (anode) and a negative electrode (cathode) into a sample of emulsion and connecting them to a con- trolled direct-current electrical source. At the end of a speci- fied time period, the electrodes are observed to determine which pole has an appreciable layer of asphalt deposited on it. Cationic emulsions will migrate towards the cathode. Pavement Preservation—The sum of all activities undertaken to provide and maintain serviceable roadways. This includes corrective maintenance and preventive maintenance, as well as minor rehabilitation projects (Geiger 2005). Pavement Preventive Maintenance—Planned strategy of cost-effective treatments to an existing roadway system and its appurtenances that preserves the system, retards future deterioration, and maintains or improves the functional condition of the system (without increasing the structural capacity) (Geiger 2005). Pavement Reconstruction—Construction of the equivalent of a new pavement structure that usually involves complete removal and replacement of the existing pavement structure including new and/or recycled materials (Geiger 2005). Pavement Rehabilitation—Work undertaken to extend the service life of an existing pavement. This includes the restoration, placing an overlay, and/or other work required to return an existing roadway to a condition of structural and functional adequacy (Geiger 2005). Penetration—An empirical measure of consistency in which a container of asphalt cement is brought to a test tempera- ture of 77°F in a water bath. A needle of prescribed dimen- sion, loaded to a weight of 100 grams, is allowed to bear on the surface of the asphalt cement for 5 seconds. The unit of 0.1 mm, which the needle penetrates into the sample, is defined as the penetration. Polymer-Modified Emulsion—These emulsions contain modifiers in the form of finely dispersed polymers. These modifiers are blended into the asphalt particles prior to the manufacturing of the emulsion or mixed with the asphalt particles during the milling process. Polymers are added to increase strength, reduce temperature susceptibility, and improve adhesion and stability. Pug Mill—A chamber in which rotating shafts have paddles spaced along their length that are capable of being angled to advance or retard the movement of the mix through the mixing chamber. Spray bars for asphalt emulsion and/or water/set coat additives are usually mounted in the mixing chamber near the aggregate feed end. Proportioned ma- terials, including aggregates and emulsified asphalts, are mixed together to yield a uniformly coated mixture. Quick Set Emulsion—Emulsions for slurries set by a chem- ical reaction between the emulsifier and the aggregate and a small amount of additives in the slurry. CSS-1h emulsions can be formulated as quick-set emulsions. These are nor- mally designated as a CQS-1h. Anionic quick-set emulsions are normally designated QS-1h. Raveling—Also commonly referred to as shelling, it is the loss of aggregate from the surface treatment. Low binder applica- tion rates, inadequate rolling, cool weather construction, and incompatible binder and aggregate types are common factors that lead to raveling [NCHRP Synthesis 340 (2005)]. Ralumac™—A cold thin surface paving solution consisting of a water-based polymer-modified asphalt emulsion, 100% crushed fine aggregate, mineral filler, water, and additives. On asphalt pavements it can be used for sealing, rut filling, and to improve a road’s macrotexture. On concrete pave- ments it can be used for texturing, noise reduction, and repairing wheel path abrasion channels caused by studded tires (Road 2010). Residue From Distillation—The distillation test provides a means of determining the relative proportion of asphalt cement and water in the emulsified asphalt. Some grades of emulsified asphalt also contain an oil distillate and the distillation test provides information on the amount of this material in the emulsion. Also, the distillation test provides an asphalt cement residue on which additional tests may be made Ring & Bell Softening Point—The term relates a measure of consistency for asphalts. Samples of asphalt loaded with steel balls are confined in brass rings suspended in a beaker of water one inch above a metal plate. The liquid is heated at the prescribed rate. As the asphalt softens, the balls and asphalt gradually sink toward the plate. At the moment the asphalt touches the plate, the temperature of the water is recorded and this is designated as the Ring & Ball Softening Point. Sand Patch—Also known as the sand circle test, a test for determining texture depth of a pavement surface (refer to ASTM E 965) [NCHRP Synthesis 340 (2005)]. Set—The point during the breaking process when the asphalt aggregate mix will no longer track when blotted with white paper. (The mix may still be too tender for traffic at this point.) Set Control Additives—Defined as small amounts of ma- terials (mineral fillers or chemical) that when added to a slurry/microsurfacing mixture, speed or retard the setting characteristics of that mix. Setting—A point when all asphalt particles have broken and combined into larger particles. This is observed when the material becomes rain safe and will support foot traffic. Settlement—The settlement test detects the tendency of asphalt globules to settle during storage of emulsified

asphalt. A prescribed volume of material is allowed to stand in a graduated cylinder for a specified number of days. Small samples are then taken from the top and bottom parts in the cylinder. Each sample is placed in a beaker and weighed. The sample is then heated until water evaporates and the residue is then weighed. The weights obtained provide the basis for determining the difference, if any, between asphalt cement content in the upper and lower portions of the graduated cylinder, thus providing a measure of settlement. Sieve Test—The sieve test complements the settlement test and has a somewhat similar purpose. It is used to determine quantitatively the percentage of asphalt present in the form of relatively large globules. Such globules do not provide thin and uniform coatings of asphalt on the aggregate par- ticles and may or may not be detected by the settlement test. In the sieve test, a representative sample of emulsified asphalt is poured through a No. 20 sieve. For anionic emul- sions the sieve and retained asphalt are then rinsed with a mild sodium oleate solution and finally with distilled water. For cationic emulsions, distilled water is used instead of sodium oleate solution. After rinsing, the sieve and asphalt are dried in an oven and the amount of retained asphalt determined. Slow Set Emulsions—Asphalt emulsions that demonstrate very stable properties. These emulsions must be stable when diluted and also have a high resistance to chemical break- down. The ability of the emulsion to mix with cement is an indication of its suitability for use with an aggregate with a high surface area. This type of emulsion for slurries is set almost entirely from the evaporation of the water. Typical designations are SS-1h (Anionic) and CSS-1h (Cationic). Slurry Seal—A mixture of slow setting emulsified asphalt, well-graded fine aggregate, mineral filler, and water. It is used to fill cracks and seal areas of old pavements, to restore a uniform surface texture, to seal the surface to prevent mois- ture and air intrusion into the pavement, and to provide skid resistance. Sprayed Seal—Australian terminology, essentially synony- mous with a chip seal, which refers to the application a bituminous binder and cover aggregate on various surfaces [NCHRP Synthesis 340 (2005)]. Stator—The fixed or stationary plate of a colloid mill. Emul- sions are formed when two immiscible liquids are intro- duced into a cavity with a small clearance between the stator and a high-speed rotor creating high shear forces. Streaking—An aesthetic and construction defect cause by nonuniform application of binder across the lane width. Streaking leads to a considerable shortening of the life expectancy of a surface treatment [NCHRP Synthesis 340 (2005)]. Stripping—Separation of the binder from the aggregate. Refer to raveling. Surface Texture—The characteristics of the pavement surface that contribute to both surface friction and noise. Surface Treatment—A surface treatment, commonly referred to as a Bituminous Surface Treatment (BST) or Asphalt 74 Surface Treatment (AST), is as an application of asphalt binder and cover aggregate on prepared gravel or crushed stone base [NCHRP Synthesis 340 (2005)]. Surface Texture—The macroscopic and microscopic char- acteristics of the pavement surface. Surface texture depth is a metric that influences material application rates, design life, skid resistance, and road noise emissions [NCHRP Synthesis 340 (2005)]. Surfactant (Surface Active Agent)—Any substance that alters the energy relationship at interfaces; e.g., organic compounds displaying surface activity such as detergents, wetting agents, dispersing agents, and emulsifiers. Uniform Cross Section—The area where the pavement width is greater than the width of the slurry system treatment placed and there are no drop-offs greater than 1⁄2 inch (12 mm). Unit Price Contract—A construction contact where the con- tractor furnishes unit prices (i.e., $ per pay unit) for each pay item in the contract and the contract is awarded to the lowest bidder computed by multiplying the contractor-furnished unit price with the engineer’s estimated quantity for each pay item and extending that to a total bid price. The con- tractor is then paid its unit price for the actual quantities even if exceed the engineer’s estimated quantities [NCHRP Synthesis 340 (2005)]. Viscosity—The Saybolt Furol viscosity test as described for asphalt emulsions is used both for the anionic and cationic emulsified asphalts to measure and specify consistency properties. As a matter of testing convenience and also to achieve suitable testing accuracy, two testing temperatures [25°C (77°F) and 50°C (122°F)] are used, depending on the viscosity characteristics of the specific type and grade of the emulsified asphalts. ABBREVIATIONS The following are abbreviations used in the synthesis report: BTU British Thermal Units C Celsius CO2 Carbon dioxide cm Centimeter CM Cubic meter CQS-P See Table 51 in chapter eight CQS-1H See Table 51 in chapter eight CQS-1HP See Table 51 in chapter eight CSS-1 See Table 51 in chapter eight CSS-1P See Table 51 in chapter eight CSS-1H See Table 51 in chapter eight CSS-1HP See Table 51 in chapter eight CY Cubic yard DOT Department of Transportation (U.S. state) F Fahrenheit FLHD Federal Lands Highway Division Ft Foot G Gram gal Gallon in. Inch kg Kilogram

75 km Kilometer l Liter lb Pound MG Megagram MJ Megajoule mm Millimeter MOT Ministry of Transportation (Canadian province/ territory) NO2 Nitrogen dioxide QC/QA Quality control/quality assurance SBS Styrene butadiene styrene SM Square meter SN Skid number SS-1 See Table 51 in chapter eight SS-1H See Table 51 in chapter eight NCAT National Center for Asphalt Technology NHI National Highway Institute U.S. United States

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TRB’s National Cooperative Highway Research Program (NCHRP) Synthesis 411: Microsurfacing explores highway microsurfacing project selection, design, contracting, equipment, construction, and performance measurement processes used by transportation agencies in the United States and Canada.

Microsurfacing is a polymer-modified cold-mix surface treatment that has the potential to address a broad range of problems on today’s highways.

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