File Name: moisture content of fine and coarse aggregate range .zip
The fine aggregate specific gravity test Figure 1 is used to calculate the specific gravity of a fine aggregate sample by determining the ratio of the weight of a given volume of aggregate to the weight of an equal volume of water. It is similar in nature to the coarse aggregate specific gravity test. The fine aggregate specific gravity test measures fine aggregate weight under three different sample conditions:. Aggregate specific gravity is needed to determine weight-to-volume relationships and to calculate various volume-related quantities such as voids in mineral aggregate VMA , and voids filled by asphalt VFA.
Absorption can be used as an indicator of aggregate durability as well as the volume of asphalt binder it is likely to absorb. Therefore, by definition, water at a temperature of Absorption, which is also determined by the same test procefure, is a measure of the amount of water that an aggregate can absorb into its pore structure. Aggregate specific gravity is used in a number of applications including Superpave mix design, deleterious particle indentification and separation, and material property change identification.
Superpave mix design is a volumetric process; it relies on mixing constituent materials on the basis of their volume. Correct and accurate material specific gravity determinations are vital to proper mix design. An incorrect specific gravity value will result in incorrectly calculated volumes and ultimately result in an incorrect mix design. Specific gravity can also indicate possible material contamination. For instance, deleterious particles Figure 2 are often lighter than aggregate particles and therefore, a large amount of deleterious material in an aggregate sample may result in an abnormally low specific gravity.
Differences in specific gravity can also be used to separate deleterious, or bad, particles from aggregate particles using a heavy media liquid. Water absorption can also be an indicator of asphalt absorption. Finally, specific gravity differences can be used to indicate a possible material change. A change in aggregate mineral or physical properties can result in a change in specific gravity.
For instance, if a quarry operation constantly monitors the specific gravity of its output aggregate, a change in specific gravity beyond that normally expected could indicate the quarrying has moved into a new rock formation with significantly different mineral or physical properties. Aggregate absorption is the increase in mass due to water in the pores of the material. Aggregate absorption is a useful quality because:.
It is generally desirable to avoid highly absorptive aggregate in HMA. This is because asphalt binder that is absorbed by the aggregate is not available to coat the aggregate particle surface and is therefore not available for bonding. Therefore, highly absorptive aggregates often specified as over 5 percent absorption require more asphalt binder to develop the same film thickness as less absorptive aggregates making the resulting HMA more expensive.
Several different types of specific gravity are commonly used depending upon how the volume of water permeable voids or pores within the aggregate are addressed Figure 3 :. The following description is a brief summary of the test. It is not a complete procedure and should not be used to perform the test. The complete fine aggregate specific gravity procedure can be found in:.
The mass of a fine aggregate sample is determine in SSD, oven-dry and submerged states. These values are then used to calculate bulk specific gravity, bulk SSD specific gravity, apparent specific gravity and absorption. Figure 5 shows the major equipment used to perform the FASG test. Figure 7: Drying the sample with a blow dryer. Figure 8: Tamping the aggregate into the mold.
Figure 9: No slump indicates surface moisture presence. If the aggregate slumps on the first Cone Test, it is assumed that the aggregate has already dried beyond the SSD condition Figure The aggregate can be restored by thoroughly mixing in a small amount of water and allowing the aggregate to stand in a covered container for 30 minutes. Figure Aggregate is beyond SSD. Calibrate a specific gravity flask pycnometer by filling with water at Agitate the pycnometer to eliminate air bubbles and then determine total mass of the pycnometer.
Figure Pouring the SSD sample into the pycnometer. This agitation procedure should be repeated several times in order to ensure that any entrapped air is eliminated. This process usually takes 15 to 20 minutes total.
Add additional water to return the pycnometer to its calibrated capacity. If bubbles prevent the proper filling of the pycnometer, adding a few drops of isopropyl alcohol is recommended to disperse the foam AASHTO, a . Determine the total weight of pycnometer, specimen, and water. Remove the aggregate from the pycnometer and dry it until it maintains a constant mass.
This indicates that all the water has left the sample. Cool the aggregate in air at room temperature for 1. Results Parameters Measured Fine aggregate bulk specific gravity. Fine aggregate bulk SSD specific gravity. Fine aggregate apparent specific gravity. Fine aggregate absorption. Specifications There are no minimum or maximum specific gravity or absorption values in Superpave mix design.
Rather, specific gravity is an aggregate quality needed to make required volume calculations. Some state agencies specify minimum aggregate specific gravities or maximum percent water absorption to help control aggregate quality. Specific gravities can vary widely depending upon aggregate type. Some lightweight shales not used in HMA production can have specific gravities near 1.
Typically, aggregate used in HMA production will have a bulk specific gravity between about 2. Bulk SSD specific gravities can be on the order of 0.
For a particular aggregate type or source, fine aggregate specific gravities can be slightly higher than coarse aggregate specific gravities because as the aggregate particles get smaller, the fraction of pores exposed to the aggregate surface and thus excluded from the specific gravity calculation because they are water-permeable increases. Aggregate absorption can also vary widely depending upon aggregate type.
Some lightweight shales not used in HMA production can have absorptions approaching 30 percent, while other aggregate types can have near zero absorption. Typically, aggregate used in HMA production will have an absorption between just above zero and 5 percent.
Absorptions above about 5 percent tend to make HMA mixtures uneconomical because extra asphalt binder is required to account for the high aggregate absorption. If absorption is incorrectly accounted for, the resulting HMA could be overly dry and have low durability absorption calculated lower than it actually is or over-asphalted and susceptible to distortion and rutting absorption calculated higher than it actually is. These masses are used to calculate the various specific gravities and absorption using the following equations:.
The ratios given in the equations are then simply the ratio of the weight of a given volume of aggregate to the weight of an equal volume of water, which is specific gravity. A quick check of the results should show that bulk specific gravity is the lowest specific gravity, bulk SSD specific gravity is in the middle and apparent specific gravity is the highest. Overview The fine aggregate specific gravity test Figure 1 is used to calculate the specific gravity of a fine aggregate sample by determining the ratio of the weight of a given volume of aggregate to the weight of an equal volume of water.
Figure 1: Fine aggregate specific gravity sample and pycnometer. Both use the same aggregate volume. Certainly, the accuracy of all measurements is important.
However, of specific concern is the mass of the SSD sample. The determination of SSD conditions can be difficult. If the sample is actually still wet on the surface then the mass of the SSD sample will be higher than it ought to be, which will cause a lower calculated bulk specific gravity. Conversely, if the sample is beyond SSD and some of the pore water has evaporated which is more likely , the mass of the SSD sample will be lower than it ought to be, which will cause a higher calculated bulk specific gravity.
Either type of error will have a cascading effect on volumetric parameters in other tests that require specific gravity as an input and Superpave mix design. Washington, D.
All codified methods for measuring the packing density of aggregate are carried out under dry condition. However, these dry packing methods do not account for the effect of water in the concrete mix. In a previous study, a wet packing method for measuring the packing density of fine aggregate under wet condition has been developed and it was found that the packing density of fine aggregate can be substantially higher under wet condition than dry condition. Nevertheless, many researchers still believe that for coarse aggregate, it does not matter much whether the packing density is measured under dry or wet condition. In this study, the wet packing method was extended to measure the packing density of coarse aggregate and blended fine and coarse aggregate. The results revealed that whilst the packing density of coarse aggregate is only slightly higher under wet condition than dry condition, the packing density of blended fine and coarse aggregate is highly dependent on whether the aggregate is dry or wet. Hence, when measuring the packing density of blended aggregate, the wet packing method should always be used.
Natural gravel and sand are usually dug or dredged from a pit, river, lake, or seabed. Crushed aggregate is produced by crushing quarry rock, boulders, cobbles, or large-size gravel. Recycled concrete is a viable source of aggregate and has been satisfactorily used in granular subbases, soil-cement, and in new concrete. If necessary, a benefaction process such as jigging or heavy media separation can be used to upgrade the quality. Once processed, the aggregates are handled and stored to minimize segregation and degradation and prevent contamination.
Can you tell by grabbing a handful of aggregate and squeezing? Can you tell just by looking at it? How about picking up some sand, throwing it against a concrete wall, and inspecting the damp mark left behind? Or, creatively, putting a clump of sand inside your cheek and giving it a little chew. Fortunately, reliable aggregate moisture content test methods exist today that provide precasters with accurate, consistent and repeatable results — and do not require you to ingest aggregate.
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