Unit 2 Flashcards by Irene Montecillo

Types of Construction Aggregates

Soil Aggregates
Concrete Aggregates
Composite Aggregates

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Almost all of natural aggregate materials originate from ______. There are three kinds of rocks namely igneous, sedimentary and metamorphic. These classifications are based on the mode of formation of rocks.

bed rocks

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________ and_________ processes work together to create soil aggregates.

Cohesion, fragmentation

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Generally ______ is an unconsolidated, or loose, combination of ____________________. The organic materials are composed of debris from plants & from the decomposition of many tiny life forms that inhabit or live in the soil, while the inorganic components of soil are: rocks & minerals, that have been gradually broken down by weather, chemical action and other natural processes.

soil, organic & inorganic materials

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are considered a three-phase material composed of rocks or mineral particles, water and air. The voids of a soil, the spaces in between mineral particles, contain the water and air.

soil

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Engineering properties of soil includes; shear strength, stiffness and permeability. These properties are being considered in order to determine and design the type of foundations, earthworks, and/or pavements subgrade required for the intended man-made structures to be built.

Fact

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Foundations built for above-ground structures include shallow and deep foundation. Retaining structures include earth-filled dams and retaining walls. Earthworks include embankments, tunnels, dikes, reservoirs, and sanitary landfills.

Fact

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Classification of Soil according to Size

Granular Soil
Fine Grained Soil
Organic Soil

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particles passing 75 mm
and retained on (Sieve #10) 2.0 mm sieves, mostly found in rivers

Gravel

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– passing 75 mm (3”) and retained on 0.075 mm (#200) sieves

Granular or coarse-grained

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passing 2.0 mm and retained on 0.075 mm sieves
~ Coarse sand – (+) 2.0 mm (-) 0.425 mm (#40)
~ Fine sand - (+) 0.425 mm (-) 0.075 mm(#200)

Sand

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Good load bearing qualities.
Permeable, hence they drain easily.
Comparatively incompressible when subjected to static loads.
Not subject to changes in strength or volume due to variation in water content. However, loose granular materials will undergo considerable reduction in volume if subjected to vibratory loads.

Properties of granular soil

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– passing 0.075 mm and larger than 0.002mm
(fine and barely visible grains)

Silt

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– soil with particle size less than 0.002mm
(cohesive or plastic)

Clay

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passing 0.001mm
(gray to black color)

Organic Soil

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inferior than fine grained soils with respect to the properties. fibrous soil due to the presence of undecomposed plant matter. unhealthy sewage-sludge odor.
found as deposits in swamps and peat bogs.

Organic Soil

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Presence of organic matter will adversely affect the engineering properties of either granular or fine-grained soil, if the amount is appreciable.

Fact

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Soil containing quantities of organic material such as grass, roots and sewage.
Highly organic soil such as peat and muck.
Soil with liquid limit exceeding 80 and/or plasticity index exceeding 55. Soil with a natural water content exceeding 100 %.
Soil with very low natural density, 800 kg./m3 or lower.
Soil that can not be properly compacted as determined by the Engineer.

Unsuitable Soil Material

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determine the particle size distribution of soil and it is used to classify/identify the soil

Sieve/Grading test Hydrometer test
Or a combined analysis

(AASHTO T 88)
(ASTM D 422)

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the lowest moisture content at which the soil will flow upon the application of a very small shearing force. It gives a certain measure of the shearing resistance of a soil when mixed with water.

Liquid limit
LIQUID LIMIT / PLASTIC LIMIT TESTS
(AASHTO T-89/T-90) (ASTM D 4318)

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the minimum moisture content at which the soil can be readily molded without breaking or crumbling

Plastic Limit
LIQUID LIMIT / PLASTIC LIMIT TESTS
(AASHTO T-89/T-90) (ASTM D 4318)

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MOISTURE DENSITY RELATION or COMPACTION TEST OF SOIL

(AASHTO T-99/T-180)
(ASTM D 698/D 1557)

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a process of increasing soil density and removing air, usually by mechanical means

Soil Compaction

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By reducing the air voids, more soil can be added to the block.

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When moisture is added to the block, water content is increasing

The soil particles will slip more on each other causing more reduction in the total volume, which will result in adding more soil and hence the dry density will increase, accordingly.

Spitting Fact

– involves the granular rearrangement of soil particles at a number of moisture contents ranging from slightly dry to very wet, by a specified amount of energy applied on a specified manner.

Compaction Test

Compaction Test (Purpose) to determine:  Amount of mixing water(Optimum Moisture Content (OMC)  Maximum Dry Density (MDD)

jojowain

Moisture content of the soil is vital to proper compaction

TRUE

__________ acts as lubricant within soil, sliding the particles together.

Moisture

Too little moisture means inadequate compaction- the particles cannot move past each other to achieve density.

The highest density for most soils is at certain water content for a given compaction effort. The drier the soil, the more resistant it is to compaction.

In a water- saturated state the voids between particles are partially filled with water, creating an apparent cohesion that binds them together. This cohesion increases as the particle size decreases (as in clay type soils).

-is a method of evaluating the relative quality of subgrade, subbase, and base soil for pavements.

CALIFORNIA BEARING RATIO (CBR) (AASHTO T-193)

CBR Requirements of Soil Aggregates:

Item- 201/202/300 80% minimum Item 200 30% minimum

This test evaluates the structural strength of coarse aggregate. It gives an indication of quality as determined by resistance to impact and wear.

ABRASION TEST (AASHTO T-96) (ASTM C 131)

The abrasive charge- consist of cast-iron spheres or steel spheres approximately 46.8 mm in diameter & each weighing between 390-455 grams

Abrasion Loss Requirements of Aggregates:

iTEM 201/200 50% maximum Item 202/300 45% maximum Item 201 – Aggregate Base course Item 200 – Aggregate Subbase course Item 202 – Crush Aggregate Base Course Item 300 –Aggregate Surface Course

Composition of concrete

Paste Cement Water Mineral Aggregate Coarse Aggregate Fine Aggregate

Composition of concrete by volume

7 - 14% cement 15 – 20% water 66 – 78% aggregate

are the most mined material in the world

Aggregates

Defined as inert, granular & inorganic materials that normally consist of stone or stone-like solids

Aggregates

The mineral composition, shape, surface texture, and grading of aggregates affect the concrete quality, thermal coefficient, drying shrinkage, stiffness creep and strength of concrete.

Aggregates

The most popular use of aggregates is to form _____________________ . Approximately ¾ of the volume of Portland cement concrete is occupied by aggregates. They provide compressive strength and bulk to concrete

Portland cement concrete

Another important application, aggregates are used in ____________________ in which they occupy 90% or more of the total volume.

asphalt cement concrete

Coarse aggregates composition

Consist of : Crushed stone Gravel Blast Furnace Slag or other approved inert materials of similar characteristics having hard strong, durable pieces and free from adherent coatings

Fine Aggregates Composition

Consist of: Natural sand Stone Screenings Or other inert materials with similar characteristics Or combination thereof, having hard, strong and durable particles.

extracted from larger rock formations through an open excavation (quarry) and reduced to usable sizes by mechanical crushing or grinding (sand, crushed limestone, gravel)

Natural Aggregates

man-made aggregates produced as a main product or an industrial by-product, (blast furnace slag, iron ore, crushed steel)

Manufactured (Synthetic) Aggregates–man-made

has a unit weight of less than 1120 kg/m3 (cinder, blast furnace slag, volcanic pumice)

Light Weight Aggregates

– has a unit weight of 1520 - 1680 kgs/m3

Normal Weight Aggregates

– has a unit weight greater than 2100 kgs./m3. It is used in special structures, such as radiation shields (magnesite limonite, heavy iron ore)

Heavy Weight Aggregates

Samples shall be dried thoroughly in air or in drying apparatus at a temperature not to exceed 60 oC

Tunay

Reduction of Samples for the different Tests:

Quartering Sample Splitter

To evaluate/determine the particle size distribution of aggregates Grading, or size distribution of aggregate is an important characteristic because it determines the paste requirement for workable concrete. Proper gradation of coarse aggregates is one of the most important factors in producing workable concrete. Proper gradation ensures that simple aggregates contain all standard fractions of aggregates in required proportion such that the sample contains minimum voids.

KORIQUEEE

A sample of well-graded aggregate containing minimum voids will require ____________ paste to fill up the voids in the aggregates.

minimum

Larger size of aggregate is preferred in concrete because of the following reasons: It reduces the cement requirement It reduces the water requirement It reduces shrinkage of concrete

okay (nonchalant)

The Maximum Size of Aggregate (MSA) which can be used is guided by the factors such as:

Thickness of section – MSA should not be greater than thickness of section or slab divided by 4 Spacing of Reinforcement – MSA should not be greater than 5mm less than the spacing of steel reinforcements Clear cover – MSA should not be greater than 5mm than cover provided. (If concrete cover is 30mm

The smallest sieve through which 100 percent of the aggregate sample particles pass. It defines the maximum aggregate size as “one sieve large than the nominal maximum size” (Roberts et al., 1996)

Maximum Size Aggregates

The largest sieve that retains some of the aggregate particles but generally not more than 10 percent by weight. It defines nominal maximum aggregate size as “one sieve size larger than the first sieve to retain more than 10 percent of the material” (Roberts et al., 1996)

Nominal Maximum Size of Aggregates

This values are used in the design of concrete and bituminous mixtures. A high value of absorption may indicate a doubtful quality of the materials.

SPECIFIC GRAVITY & ABSORPTION DETERMINATION OF COARSE & FINE AGGREGATES AASHTO T 84/ ASTM C 128 AASHTO T 85/ASTM C 127 The bulk Specific Gravity of most Rocks = 2.5 – 2.8

The ratio of the mass of a solid or liquid to the mass of an equal volume of distilled water 4°C (39°F). Because the aggregates may contain water-permeable voids, so two measure of specific gravity of aggregates are used: apparent specific gravity and bulk specific gravity.

Specific Gravity Aggregates

Aggregates having more water absorption are more porous in nature and are generally considered unsuitable unless they are found to be acceptable based on strength, impact, and hardness tests.

TAMA

The absorption and surface moisture of aggregates should be determined according to ASTM C 70, C 127, C 128, and C 566 (AASHTO T 255) so that the total water content of the concrete can be controlled, and correct batch weighs determined. The internal structure of an aggregate particle is made up of solid matter and voids that may or may not contain water.

I SEE

– full absorbent

Oven dry

– dry at the particle surface but containing some interior moisture, thus still somewhat absorbent Saturated surface dry (SSD) – neither absorbing water from nor contributing water to the concrete mixture.

Air dry

– containing an excess of moisture on the surface (free water). The amount

Damp or wet

Most fine aggregates can maintain a maximum drained moisture content of about_________ whereas coarse aggregates can maintain only about _________.

FINE 3% to 8% COARSE 1% to 6%

If aggregate is drier than SSD, it will absorb water from concrete, thus, reducing the workability. On the other hand, if it moist, it will contribute water in the concrete reducing the strength.

NOTED

Values of unit weight/mass are used in volumetric-gravimetric calculation. In volumetric batching of concrete aggregates, unit weight/mass should be known to convert weight/mass into loose volume.

UNIT WEIGHT DETERMINATION OF COARSE & FINE AGGREGATES

__________ and ________ of Aggregate affects the properties of fresh concrete more of hardened concrete. Concrete is more workable when smooth and rounded aggregate is used instead of round angular or elongated aggregate.

Shape and texture

Most natural sands and gravel from riverbeds or seashores are smooth and rounded and are excellent aggregates. Crushed stone, on the other hand, produces much more angular and elongate aggregates, which have a higher surface-to-volume ratio, better bond characteristics but require more cement paste to produce a workable mixture.

Surface Texture of Aggregates can be either smooth or hard. A smooth surface can improve workability, yet a rougher surface generates a stronger bond between the paste and the aggregate creating a higher strength. There are two considerations in the shape of the material, the angularity and the flakiness. Crushing rocks produces angular particles with sharp corners and rough texture. Due to weathering, the corners of the aggregates break down, creating sub angular particles and smooth texture.

Fully water- worn or completely shape by attrition ex. river or seashore gravel desert, seashore and wind blown sand

ROUNDED

Naturally irregular or partly shaped by attrition ex. other gravels, land or dug flint

IRREGULAR

Material of which the thickness is small relative to the other two dimensions ex. laminated rocks

FLAKY

Well defines edges formed the intersection of roughly planar faces ex. crushed rocks of all types, talus, crushed slag

ANGULAR

Material, usually angular, in which length is considerably larger than the other two dimensions

Elongated

Material having the length considerably larger than the width and the width considerably larger than the thickness.

FLAKY AND ELONGATED

Angular aggregates exhibit a better interlocking effect in concrete, which property makes it superior in concrete used for roads and pavements

The total surface area or rough textured angular aggregates is more than smooth rounded aggregate for the given volume. By having greater surface area, the angular aggregate may show higher bond strength than rounded aggregates.

Rounded particles create less particle-to-particle interlock than angular particles and thus provide better workability and easier compaction. However, in asphalt mix less interlock is generally a disadvantage as rounded aggregate will continue to compact, shove and rut after construction.

This test evaluates the structural strength of coarse aggregate. It gives an indication of quality as determined by resistance to impact and wear.

Abrasion Test

The abrasive charge- consist of cast-iron spheres or steel spheres approximately 46.8 mm in diameter & each weighing between 390-455 grams.

noted

Abrasion Loss Requirements of Aggregates:

Item 310 45% maximum Item 311/405 40% maximum

The test determines the presence of injurious organic compounds in natural sand (to be used in cement mortar or concrete)

ORGANIC IMPURITIES IN FINE AGGREGATES (AASHTO T 71) (ASTM C 87)

If the color of the solution with sample is darker than the reference standard color solution/tester, the sand under test shall be considered to possibly contain the injurious organic compounds. Aggregates shall be rejected.

....

Aggregate failing in the test may be used provided that the discoloration is due principally to the presence of small quantities of coal, lignite or similar discrete particles. Aggregate failing in the test may be used provided that, when tested for the effect of organic impurities on strength of mortar by AASHTO T 71, the relative strength at seven days is not less than 95%

Test for the effect of organic impurities of Strength of Mortar, (AASHTO M T 71) the Fine Aggregates may be used if the Relative Strength at 7 and 28 days is not less than 95 % . Strength of Untreated Sand=> 95 % Strength of Treated Sand

Aggregates must be resistant to breakdown & disintegration from weathering (wetting/drying & freezing/thawing). Involves repeatedly submerging the aggregate sample (24 hrs) in a saturated solution of Sodium or Magnesium Sulfate. An aggregate is considered to be physically sound if it is adequately strong and is capable of resisting the influences of weathering without disruption or decomposition. Chemical soundness of an aggregate is also important. In many instances, excessive expansion causing premature deterioration of concrete has been associated with chemical reaction between reactive aggregate and the alkalis in cement.

SOUNDNESS TESS OF AGGREGATES AASHTO T 104) (ASTM C 88)

Component of a composite material that resists compressive stress and provides bulk to the composite material. This usually being used for Bituminous or Asphalt Mix

COMPOSITE AGGREGATES

DPWH standard specifications for Highways, Bridges, and Airports Volume II, 2013 Edition, Sub-item 703.5.1-Coarse Aggregate for Bituminous Concrete states that Coarse aggregate retained on the 2.36 mm (No. 8) sieve shall be crushed stone, crushed slag or crushed or natural gravel and unless otherwise stipulated, shall conform to the quality requirements of AASHTO M 79.

COMPOSITE AGGREGATES

Sub-item 703.5.2 states that Fine aggregate shall pass the 2.36 mm (No.8) sieve and shall consist of natural sand, volcanic ash, stone, stone screenings or slag screenings or a combination thereof and unless otherwise stipulated shall conform to the quality requirements of AASHTO M 29 (ASTM D 1073)

COMPOSITE AGGREGATES