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MATERIALS > 03-CONCRETE > Flashcards

03-CONCRETE Flashcards

1
Q

CONCRETE 5 INGREDIENTS

A 
Water
Sand
Aggregate
Portland Cement
GGBS
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2
Q

GGBS

A

ground granulated blast-furnace slag

A by product of iron and steel manufacturing.

Good as protection against sulfide and chlorine attack (marine environments) in concrete mixtures. Often replaces Portland cement as a cheaper alternative in a ratio of 30-85percent. Makes concrete whiter.

Disadvantage: takes longer to harden especially in colder climates.

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3
Q

PERCENTAGE BY WEIGHT of CURED CONCRETE INGREDIENTS

A

6 percent WATER
14 percent CEMENT
80 percent AGGREGATE

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4
Q

PORTLAND CEMENT

A

Patented 1824 by Joseph Aspdin

Manufactured by mixing finely ground limestone or chalk, clay, and sand, and heating it to an almost melting point of 1,450 degrees Celsius in large rotating kiln.

the ground powder is added with 5 percent gypsum to control setting time.

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5
Q

AGGREGATE in CONCRETE

A

Range from fine particulates 0.063 mm up to 2 mm

Small stones 2mm - 22mm

Main purpose is to restrain shrinkage but also acts as a low cost filler.

Concrete without sand is produced with “no fines” and can create water permeable surfaces.

Key properties: density, cleanliness, moisture content, grain form, surface texture, and hardness.

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6
Q

BASIC CHEMISTRY OF CONCRETE

A 
1 Glass
2 Fly Ash
3 Ground Granulated Blastfurnaced Slag
4 Portland Cement
5 Calcium Aluminum Cements
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7
Q

WATER IN CONCRETE

A

A proportion of water evaporates from cement and can leave an increased porosity. Important to have correct water proportions to mixture.

Increased porosity can lead to frost damage and water infiltration.

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8
Q

ADMIXTURE in CONCRETE

A

Introduced to improve workability or performance of conc once cured.

Can reduce water content of concrete and this strength

Accelerate or retard setting strength gain

Entrain air bubbles to improve resistance to freeze thaw cycles

Reduce shrinkage

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9
Q

HOW IS COLOR CONTROLED IN CONCRETE?

A

Color is defined by the smallest particles in the mix: cement and sand.

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10
Q

ALTERNATIVES to CEMENT

A 
Pozzolanic rocks (Romana)
GGBS
Fly Ash
Silica Fume
Calcium-sulfoaluminate based cements
Geopolymeric Cements
Burnt Shale
Magnesium-oxide-based cements
Limestone Flour

Reasons for alts: to reduce CO2

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11
Q

FLY ASH

A

A fine grey powder, a by product of coal fire power stations and is electrostatically precipitated from exhaust gases. Artificial pozzolan.

Improves cohesion
Improves workability
Reduces embodied energy

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12
Q

HIGH STRENGTH CONCRETE

A

Typ strength for structural concrete 40 MPa - up to 200 MPa is achievable

MDF- Macro Defect Free used polymer paste
DSP- Dense Silica Particulate, extremely fine particulates that minimize void space
CRC- Compact Reinforced Composite, fine silica, typ compressive 150 MPa, can be precast or in situ
DUCTAL

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13
Q

PORTLAND CEMENT TYPES

ASTM C150

A

Type I / general-purpose cement
Type II / precaution against moderate sulfate attack important, drainage structures
Type III / High Early strength usually within a week or less
Type IV / Low Heat, for large masses of conc such as in dams

Type V / Sulfate Resisting, when construction exposed to severe sulfate action such as some western states with soil and waters of high alkali content - slower rate of strength

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14
Q

PORTLAND-POZZOLAN CEMENT

A

cement that contains pozzolan (siliceous or siliceous and aluminous material) blended with portland

typ pozzolan materials: fly ash, volcanic ash, calcined shale and clay

higher cured strength and decreases the heat of hydration which is important for heavy mass conc structures.

**Pozzolans should not be used where high early strength is required because they slow the curing process.

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15
Q

CONCRETE WEIGHT

A

Normal-weight – 135-160 lb per cubic foot

structural lightweight – 85 - 115 lb per cubic foot

Other lightweight (pumice, scoria, perlite) – 15 - 90 lb per cubic foot

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16
Q

COARSE AGGREGATE

A

gravel, crushed stone, or another suitable material larger than 1/4 in. in diameter

Coarse aggregate that is sound, hard, and durable is best suited for making concrete.

**in walls, coarse aggregate should be no more than 1/5 the overall wall thickness and no more than 1/3 in slabs

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17
Q

ADMIXTURES

A

materials other than portland cement, aggregates, and water that are added to concrete either immediately before or during its mixing to alster properties of the concrete in a variety of ways such as:

ASTM C494 classifies types
A: water-reducing
B: Retarding
C: Accelerating
D: Water-Reducing and Retarding
E: Water-Reducing and Accelerating
F: High-Range Water-Reducing
G: High-Range Water-Reducing and Retarding

**use w/ caution - difficult to predict

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18
Q

AIR-ENTRAINING AGENTS

A

air-entraining admixtures produce many microscopic stable air bubbles in concrete.

improves concrete’s workability, durability, and produces a hardened concrete resistant to severe frost action and the effects of salt applied for snow and ice removal.

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19
Q

No 3 Steel Bar
No 4 Steel Bar
No 5 Steel Bar

A

3 - .376 lb/ft / diameter .375in
4 - .66 lb/ft / diameter .5 in
5 - 1.043 lb/ft / diameter .625 in

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20
Q

REGLET

A

a device that forms a slot in concrete for the insertion of flashings

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21
Q

A rule of thumb for joint spacing in concrete

A

joint spacing in slabs in feet should not exceed two slab thicknesses in inches for unreinforced concrete made with coarse 3/4 in max aggregate. Ex:

4 in slab would req control joints at intervals not to exceed 8ft

**Control joints are usually unnecessary in structurally reinforced slabs (Types III and IV)

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22
Q

A KEY JOINT

A

a tongue and groove joint between slabs that permits the slabs to swell without cracking

23
Q

WALES, FORMWORK

A

the horizontal bracing of the vertical frame holding the formwork together.

24
Q

SLUMP TEST

A

often conforms with ASTM C143

measures the consistency of fresh concrete before it sets

any changes in slump on the job indicates changes have been made in grading or proportioning the aggregate or in water content - mix should be corrected immediately

a test specimen is made in a mold called a slump cone

25
Q

COMPRESSION TEST

A

ASTM C31

determines whether a concrete has the specified compressive strength.

tested at 7 days and 28 days

26
Q

FLOATING

A

after concrete has been poured and screeded

a power trowel is used for purpose:
embed large aggregate just beneath the surface
remove slight imperfections, humps, and voids
consolidate mortar at the surface in preparation for other finishing operations
opens the surface to permit excess moisture to escape

27
Q

WATERSTOP

A

flexible barriers used to prevent the passage of liquids and gases under pressure through joints in concrete slabs.

TYP made of polyvinyl chloride, and their shapes vary according to application.

28
Q

CONTROL JOINTS

A

anticipate shrinkage and cracking by controlling where cracking should occur to avoid irregular cracking

29
Q

ISOLATION JOINTS / EXPANSION JOINTS

A

prevents bonding of one concrete section with one another

1/8” + thick asphalt-impregnated fiber sheets in floors at columns, footings, junctures between floors and walls that allow movement

30
Q

FINISHING CONCRETE

A

SCREEDING: after the newly placed concrete surface poured screeding straightens and flattens a surface by moving a straightedge back and forth with a saw-like motion across the top of forms

LEVELING: “darbying or bull floating” bringing the concrete surface to true grade with enough mortar to produce desired finish - after screeding

EDGING: rounding off the formed edge of a slab to prevent chipping or damage

FLOATING: another leveling technique, embeds large aggregate just beneath surface, removes slight imperfections, humps and voids to produce level plane, open surface to allow excess moisture to escape

TROWELING: produce a smooth, hard surface

BROOM FINISHING: roughens surface of concrete like on sidewalks for better traction

31
Q

CONCRETE FOUNDATION TYPES

A

1 / SPREAD FOUNDATIONS: distribute a building’s loads directly to a sufficient area of soil to obtain adequate bearing capacity

2 / PILE and CAISSON: transmit bldg loads through soils that have inadequate bearing capacity for spread footings to deeper layers of soil or rock that have adequate bearing value.

32
Q

MAT AND RAFT FOUNDATIONS

A

used over soils of low bearing capacity when other foundations would be inadequate – made of concrete and heavily reinforced with steel so that the entire foundation will act as a unit

33
Q

MAT FOUNDATION

A

thickened slab that supports loads and transmits them as a single structural unit over the entire slab and soil surface area

used when foundations for a building become so large, usually due to poor soil, that it is more economical to join them into a single unit than to cast them each separately

34
Q

RAFT OR FLOATING FOUNDATION

A

a mat foundation becomes a raft or floating foundation when it is combined with basement walls and placed beneath a building in such a way that the weight of the soil removed to make the basement equals the weight of the building’s superstructure

settlement minimum as the bldg load on soil is no more than wight of escavated soil.

35
Q

SLAB CONSTRUCTION DEPENDS ON THESE 4 FACTORS

A

1 / slab type
2 / site prep, including slab-bed, grading and backfilling
3 / precautions to control ground and surface moisture
4 / thermal control when required

36
Q

GROUND SUPPORTED SLAB CLASS TYPES

A

I : unreinforced and separated from elements that support the superstructure, max perim dim of 32’ before control joints needed, square-ish regular shapes preferred – 4” thick

II : separated from elements that support superstructure but contains welded wire fabric or reinforcing bars in localized areas, max perim dim of 75’ before control joins, supports up to 500lb/lft of int partitions – 4” thick

III : combination foundation-floor system, structurally reinforced, good for problem soils that undergo substantial volume changes, receives super-structure loads and transmits over slab

IV : structurally reinforced and can be used on poor soil - receive and transmit superstructure, structurally supported slab with pile or caisson foundations

37
Q

FLATNESS VS LEVELNESS IN SLABS

A

FLATNESS: a measure of the degree to which the surface of a slab deviates from a plane – F-curve or F-number system is used to measure flatness , refer to ASTM E1155

LEVELNESS: a measure of the degree to which a slab deviates from horizontal

38
Q

GIRDERS

A

are large beams, they may be simple or continuous and they often carry a uniform load but they also carry other beams

large transfer girders sometimes also carry columns

39
Q

SIMPLE BEAMS
CONTINUOUS BEAMS
FOUNDATION BEAMS

A

SIMPLE BEAMS: span only one bay from support to support, reinforcing tends to be same throughout.

CONTINUOUS BEAMS: crosses more than one span, stirrups req at each end of beam

BEAMS PART OF FOUNDATION: act as part of the slab, affected by forces acting on the slab.

40
Q

PRESTRESSING CONCRETE BEAMS

A

before concrete is placed around the steel and performed in controlled conditions in a shop or factory, stretching of reinforcing bars creates compression in a beam.

typ done with precast concrete as prestressing anywhere outside a controlled shop/factory is expensive

41
Q

POST-TENSIONING CONCRETE BEAMS

A

adds permanent tension to the reinforcing steel in cas-in-place concrete and subsequently places the concrete under compression.

done using TENDONS which are bundles of high-strength cold-drawn steel wire strands or steel bars. The tendons are coated with oil or placed in a steel tube to prevent bonding between conc and tendons. Concrete is placed and permitted to cure.

post-tensioned beams tend to shorten due to elastic compression and creep

42
Q

STRUCTURAL SLABS
ONE-WAY
TWO-WAY

A

ONE-WAY: span in one direction from support to support, there are solid and ribbed or joist slabs. solid slabs usually have beams, girders, or bearing walls on each of their sides.

TWO-WAY: slabs that span in two perpendicular directions. Two types of two-way slabs are flat plate and waffle slabs.

43
Q

PLANT-CAST

A

precast conc elements produced in a factory environment. Units are cast at ground level in the plant, shipped to the construction site, and set in place using cranes

advantages: easier to control quality, mechanical vibration can control air bubbles, ease of prestressing structural units, possible to steam-cure allowing it to be removed from casting bed w/in 24 hrs, erected quickly once on site
disadvantages: heavy and bulky concrete units must get shipped to the site, limits size with truck/road size,

STRUCTURE PRE-CAST AND ARCHITECTURAL PRE-CAST

44
Q

STRUCTURAL PRE-CAST CONCRETE

A

part of the structural system and carry loads other than their own weight. Includes walls, beams, girders, columns, and floor/roof systems

45
Q

ARCHITECTURAL PRECAST CONCRETE

A

units include panels and other members used as part of a building’s exterior cladding.

most are not load-bearing, but some sandwich panels are load-bearing.

PCI (PrecastConcreteInstitute), MNL-117 establishes standard practices for the manuf of arch precast conc

46
Q

SANDWICH PANELS

A

consist of one or more layers of precast concrete and a layer of foam insulation

47
Q

GLASS-FIBER REINFORCED CONCRETE (GFRC)

A

a plant-cast composite product based on portland cement reinforced with randomly dispersed glass fibers (4-5 percent of mixture) in lieu of reinforcing steel. Weighs 80 percent less than conventional precast concrete.

typ for ext wall cladding systems such as panels, col covers, window-wall units, fascia panels, mullions, mansards, not load-bearing

adv: unlimited design flexibility and shapes, wide range of colors,
disadv: move 1/8” for every 10ft, joints and anchors should be flexible

48
Q

ULTRA HIGH-PERFORMANCE FIBER REINFORCED CONCRETE

A

produced using quartz sand, ground quartz, coarse aggregate in the 1mm range, and silica fume reif w/ embedded organic or steel fibers

49
Q

MICRO-CONCRETE

A

made by casting mortar made from portland cement, specially selected very fine aggregates and supplemental cementitious materials such as prozzolans, over a 3d mat of fine wire reinf mesh

50
Q

CONCRETE TOPPINGS

A

thin slabs of concrete placed on top of other concrete, waterproofing, or insulation. Aggregates gen smaller, about max 1/2 in.

type types: BONDED and UNBONDED

51
Q

BONDED VS UNBONDED CONC TOPPINGS

A

BONDED: conc placed over an underlying conc slab or precast conc struct element. May be placed at same time as struct slab or later. 1 - 1 1/2 in but 2-4 in over precast

UNBONDED: thin conc slabs used to produce wearing surfaces over sheet membrane waterproofing or insulation. typ 3 in thick and always contain a layer of welded wire fabric.

52
Q

UNDERLAYMENT

A

a material placed beneath floor finishing materials, such as tile, resilient flooring, carpets, and liquid-applied flooring, to level and stabilize the substrate to receive floor finishes.

2 cement-based types: gypsum cement underlayment and cement-based polymer-modified, self-leveling underlayment

53
Q

TABBY

A

cementitious material specific to certain coastal regions in the southeastern part of the country which included crushed shells

MATERIALS (5 decks)

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