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GROUP 3
PROPONENTS:AGUINSATAN, Rannie ReinBONGATO, Pearl ArnieLANIBA, Roger Jr.NAMUAG, Melo JaneJAVIER, Leimarc
Specific Weight, Water Absorption, Abrasion, Density and Moisture Content Of Aggregates
Definition of Aggregate
Aggregate:
Granular material of mineral composition such as sand, gravel, shale, slag or crushed stone.
General
From the previous reports, we’ve learned that aggregates are the important constituents in concrete.
They give body to the concrete, reduce shrinkage and effect economy.
Without the study of the aggregate in depth and range, the study of the concrete is incomplete. Cement is the only factory made standard component in concrete.
Specific Weight
Specific Weight is defined as weight per unit volume. Weight is not the same thing as mass.
Bulk Density (Unit Weight) and VoidsThe bulk density or unit weight of an aggregate is themass or weight of the aggregate required to fill a containerof a specified unit volume. The volume referred to here isthat occupied by both aggregates and the voids betweenaggregate particles.The approximate bulk density of aggregate commonlyused in normal-weight concrete ranges from about1200 to 1750 kg/m3 (75 to 110 lb/ft3).
Bulk Density (Unit Weight) and Voids
Void contents range from about30% to 45% for coarse aggregates to about 40% to 50% forfine aggregate. Angularity increases void content whilelarger sizes of well-graded aggregate and improved gradingdecreases void content. Methods of determiningthe bulk density of aggregates and void contentare given in ASTM C 29 (AASHTO T 19). In these standards,three methods are described for consolidating theaggregate in the container depending on the maximumsize of the aggregate: rodding, jigging, and shoveling. Themeasurement of loose uncompact void content of fineaggregate is described in ASTM C 1252.
In accordance with unit weight
Light weight aggregate: The unit weight of aggregate is less than 1120 kg/m^3. The corresponding concrete has a bulk density less than 1800 kg/m^3.
Normal weight aggregate: The aggregate has unit weight of 1520-1680 kg/m^3. The concrete made with this type of aggregate has a bulk density of 2300-2400 kg/m^3.
Heavy weight aggregate: The unit weight is greater than 2100 kg/m3. The bulk density of the corresponding concrete is greater than 3200 kg/m3. A typical example is magnesite limonite, a heavy iron ore. Heavy weight concrete is used in special structures such as radiation shields.
What is Absorption?
Absorption: The increase in weight due to water contained in the pores of the material.
Water Absorption
The measured water absorption rate and specific gravity of aggregates is routinely used in design and construction of pavement materials and structures worldwide. The ability to measure the water absorption and specific gravity of aggregate materials with high degree of accuracy and repeatability in a short time is critical for engineers and practitioners interested in the properties of soils and aggregates.
Aggregate Absorption
Aggregate absorption is the increase in mass due to water in the pores of the material. Aggregate absorption is a useful quality because:
High values can indicate non-durable aggregate.
Absorption can indicate the amount of asphalt binder the aggregate will absorb.
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.
What is Hot Mix Asphalt (HMA) Pavement?
Asphalt pavement refers to any paved road surfaced with asphalt. Hot Mix Asphalt (HMA) is a combination of approximately 95% stone, sand, or gravel bound together by asphalt cement, a product of crude oil. Asphalt cement is heated aggregate, combined, and mixed with the aggregate at an HMA facility.
What is abrasion and how does it affect erosion?
Abrasion is the mechanical scraping of a rock surface by friction between rocks and moving particles during transport by wind, glacial, waves gravity, running water or erosion.
Erosion is a gravity driven process that moves solids(sediment, soil,rock,and other particles)in a natural envionment or their source and deposits them elsewhere. It usually occurs due to transport by wind,water,or ice;bydown-slope creep of soil and other material under the force of gravity; or living organisms, such as burrowing animals, incase of bioerosion.
sample Original
after test sieve 12 No.
W
W Loss %
KINDS OF ABRASION RESISTANCE TEST:
KINDS OF ABRASION RESISTANCE TEST:
Four different moisture conditions for aggregates
Oven-dry (OD): This is achieved under laboratory conditions when the aggregate is heated to 220 F (105 C) for an extended period. Under this condition, all moisture is removed from the aggregate’s pores.
Aggregate moisture corrections
Aggregates are not completely solid but rather contain a certain level of porosity. Pores may be located in the center of the aggregate, while others may actually connect to the surface of the aggregate. When calculating the bulk specific gravity of an aggregate, take both the volume of the aggregate and all its pores into consideration. These pores will likely contain a certain level of moisture that will affect the performance of the concrete if appropriate corrections are not made to account for the actual moisture content of the aggregates.
Four different moisture conditions for aggregates
Air-dry (AD): The surface of the aggregate is dry and the internal pores may be partially filled with water. This condition may occur on a hot summer day or in an arid region. The aggregates will likely absorb water from the mix, which may affect the workability of the concrete unless proper adjustments are made to the aggregate and water batch weights.
Four different moisture conditions for aggregates
Saturated surface-dry (SSD): This is achieved under laboratory conditions when all the pores are completely filled with water but no free water remains on the surface of the aggregate. Aggregates in this condition will not contribute free water nor absorb water from the mix.
Four different moisture conditions for aggregates
Damp or Wet: All the pores are completely filled with water and the surface of the aggregate contains free water. Aggregates in a stockpile will typically be in this condition, meaning additional water will be added to the mix unless proper adjustments are made to the aggregate and water batch weights.
Aggregate mixture proportions are developed using either the oven-dry or saturated surface-dry condition. It is important to know this information when adjusting mix designs to account for actual aggregate moisture contents. Mix designs are typically developed using the oven-dry condition, but some may be developed using the saturated surface-dry condition.
FORMULAS:
Absorption
Moisture Content
MCW W
W
mc od
od
,%
100
FORMULAS:
volume and weights
BSGW
W W
W
Wssd
ssd
ssd submerged
ssd
water
displaced
BSGW
W W
W
W Wod
od
ssd submerged
od
water
displaced
water filled
external voids
FORMULAS:
Voids & Dry-Rodded Unit Weight, DRUW
DRUW = the weight of oven dry compacted aggregate that occupies a unit volume, kg/m3 or lb/ft3
VoidsSG DRUW
SG
od water
od water
,%
100
SAMPLE PROBLEM:
SAMPLE PROBLEM:
SOURCES:
AASHTO, Guide Specification For Highway Construction
SECTION 56X Portland Cement Concrete Resistant to Excessive
Expansion Caused by Alkali-Silica Reaction (Appendix
F to ASR Transition Plan), http://leadstates.tamu.edu
/ASR/library/gspec.stm, 2001.
SOURCES:
http://www.pavementinteractive.org/article/coarse-aggregate-specific-gravity/#sthash.vM2FuOxN.dpuf
http://www.engineeringintro.com/concrete/concrete-strength/bulk-density-of-aggregates-loose-and-compact-bulk-density/
http://civilvalley.blogspot.com/2012/05/standard-test-method-for-determination.html
http://precast.org/2010/05/water-to-cement-ratio-and-aggregate-moisture-corrections/
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