Aggregate Quality Requirements for Pavements (2018)

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82 Absorption Absorption is a measure of the amount of water that an aggregate can absorb into its permeable pore structure. Pores that absorb water are also referred to as “water permeable voids.” Absorption of an aggre- gate particle is the weight of water absorbed divided by the dry weight of the aggregate, expressed as a percentage. Alluvium Loose, unconsolidated (not cemented together into a solid rock) soil or sediments, which has been eroded, reshaped by water in some form, and redeposited in a non-marine setting. Artificial aggregate source Mineral-based materials that are artificially processed using thermal or chemical means to produce a granular material. Asphalt surface treatment Application of a layer of asphalt or asphaltic mixture with or without aggregate to a pavement surface. Examples include, but are not limited to, fog seal, sand seal, chip seal, slurry seal, cape seal, microsurfacing, and nova chip. Blast furnace slag Obtained by quenching molten iron slag (a byproduct of iron and steel- making) from a blast furnace in water or steam, to produce a glassy, granular product. Blending Combining different types of aggregates from two or more sources with certain proportions to satisfy a target gradation or set of quality requirements. Bound pavement layer Layers of a pavement structure consisting of aggregate materials mixed with adding an external binding agent such as asphalt binder, Portland cement, fly ash, etc. Examples of bound pavement layers include, but are not limited to, asphalt concrete, Portland cement concrete, and stabilized subbase/base. Bulk specific gravity Ratio of the mass of a unit volume of aggregate, including the water per- meable voids, at a stated temperature to the mass of an equal volume of gas-free distilled water at the stated temperature. Chip seal A pavement surface treatment that combines one or more thin layer(s) of asphalt binder with one or more layer(s) of fine aggregate. Deleterious material Clay lumps, shale, soft, friable, or laminated particles, vegetable matter, or other objectionable material. Flexible pavement Defined as a mixture of asphaltic or bituminous material and aggregates placed on a bed of compacted granular material of appropriate quality in layers over the subgrade. Glossary

Glossary 83 Fluvial In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. Glacier A thick, long-lasting mass of ice accumulated on land surfaces. Leachate Any liquid material that drains from land or stockpiled material and contains significantly elevated concentrations of undesirable material derived from the material that it has passed through. Lightweight aggregate Produced from materials such as clay, shale, slate, perlite, and slags. The raw material is expanded to about twice the original volume of the raw material. The expanded material has properties similar to natural aggregate, but is less dense and therefore yields a lighter product. Marginal aggregate source Any aggregate that is not normally usable because it does not have the characteristics required by an agency’s specification, however, could be used successfully by modifying normal pavement design and construc- tion procedures through research and investigation. Mineralogy A subject of geology specializing in the scientific study of chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts. Morphological aggregate properties Aggregate shape properties including forms such as flatness and elon- gation or sphericity, angularity, and surface texture. Nontraditional large size aggregates Aggregate materials with maximum particle sizes up to 8 in. (203 mm) generally used as rock fills to improve bearing capacity of soft subgrades. Polishing Polishing relates to the loss of aggregate surface texture, which can affect pavement’s microtexture and influence its skid resistance. Porosity Porosity is the dominant pore size and pore size distribution of aggre- gate particles. Porosity is expressed as the ratio of volume of voids to the total volume of rock. Porosity of an aggregate particle refers to the percentage of the particle that is porous by volume. (Absorption % × Specific Gravity = Porosity %) Provisional standard These are standards that have been adopted on a temporary basis for a cer- tain period. Provisional standards may or may not become a full standard. p-value In statistical analysis and testing, the p-value or probability value is the probability for a given statistical model that, when the null hypothesis is true, the statistical summary (such as the sample mean difference between two compared groups) would be the same as or of greater mag- nitude than the actual observed results. Qualified/Approved aggregate source Aggregate materials obtained from a specific source such as a quarry that has met the requirements established by an agency for use in a certain application. Quality assurance All those planned and systematic actions necessary to provide confi- dence that a product or facility will perform satisfactorily in service; or making sure the quality of a product is what it should be. Quarry byproducts/ byproduct aggregate Mineral fine materials resulting from different stages in production of aggregates; quarry fines may cover a range of aggregates with maximum sieve sizes of 0.079 to 0.25 in. (2 to 6.25 mm). Reclaimed asphalt pavement Removed and/or reprocessed pavement materials containing asphalt and aggregates.

84 Aggregate Quality Requirements for Pavements Recycled aggregate source Aggregate source produced by crushing asphalt and/or cement concrete to reclaim the aggregate. Recycled concrete aggregate Crushed old concrete particles from sidewalks, pavements, curbing, and building slabs. After being compiled, the concrete is processed and screened, which includes crushing the concrete into smaller pieces. Rigid pavement Constructed from cement concrete or reinforced concrete slabs. Soundness Aggregate’s resistance to disintegration by weathering and, in particular, freeze-thaw cycles. Statistical t-test A t-test is an analysis of two population means through the use of sta- tistical examination; a t-test with two samples is commonly used with small sample sizes and testing the difference between the samples when the variances of two normal distributions are not known. Steel furnace slag A byproduct of the steelmaking and steel refining processes. Calcium oxide and iron oxide are the two major chemical constituents. Theoretical maximum specific gravity (Rice method) Theoretical maximum specific gravity is determined by taking a sample of loose HMA (i.e., not compacted), weighing it, and then determining its volume by calculating the volume of water it displaces. Theoreti- cal maximum specific gravity is then the sample weight divided by its volume. Unbound pavement layer Layers of a pavement structure consisting of aggregate materials without adding binding agent. Unsurfaced pavement Gravel or dirt road with no surface material added and constructed with gravel. Virgin/natural aggregate source An aggregate source consists of rock fragments in their natural state that have been subjected to mechanical processing such as crushing, washing, and sizing. Note: See also AASHTO Transportation Glossary, 4th Ed. (https://bookstore.transportation.org/ item_details.aspx?ID=1394) and AASHTO Glossary of Highway-Related Drainage Terms (https:// bookstore.transportation.org/imageview.aspx?id=689&DB=3).