Materials - Concrete Flashcards
Joseph Aspdin
patented process for making cement w/ English portland limestone
Duff Abrams
water-to-cement ratio
Joseph Monier
credited with spreading use of reinforced concrete; patented iron reinforced concrete basins, pipes, building panels, bridges & beams
Francois Hennebique
united beam & column in one monolithic system
Eugene Freyssinet
patented method for prestressing for a long span bridge design in 1928
Le Corbusier
Domino system, cantilevered slab on piloti
Auguste Perret
trabeated system of monolithic columns & beams as frames with concrete block infill
Francois Sonderdork Jr.
parabolic arch, London’s royal horticultural hall
PA Michelis
shell structure, can carry loads equally in all directions, no difference between load and support
Portland cement
lime, silica, iron oxide, alumina; proportioned, round, burned to clinkers, pulverized (fineness directly related to strength)
Portland Cement (Type I)
Standard, for general all-purpose use
Portland Cement (Type II)
Modified, for slow setting & less heat
Portland Cement (Type III)
High early strength, for quick setting & early strength
Portland Cement (Type IV)
Low heat, for slow setting (little heat)
Portland Cement (Type V)
Sulfate resisting, for alkaline water & soils
Fine aggregate dimensions
1/4” or less in diameter, sand
Coarse aggregate dimensions
1/4 - 1 1/2” diameter, gravel or crushed rock
sieve tests
determine % of particle sizes, ensure finer particles fit all voids between large particles to be solidly filled; max aggregate size no greater than 1/3 thickness of concrete slabs or 3/4 minimum space between reinforcing
Admixtures
surface applications/finishes for concrete, hardeners, pigments, special aggregates, sealers, abrasives, fillers for patching
accelerators
calcium chloride, speed up setting time
air entraining agents
resins, fats, oils; resist freezing action
retarders
starches, sugars, acids; slow down setting time
waterproofing
stearate compounds; decrease permeability
water reducing
organic compounds, reduce water content
workability agents
powdered silicas & lime; improve workability
Concrete Mix Design (general weights)
concrete 150 lb/cubic foot; aggregates, dry sand & gravel 100 lbs/ cubic foot; water per gallon 8 lbs/gallon
Uncontrolled concrete work ratio
1:3:5 cement: fine aggregate:coarse aggregate
Laitance
chalky surface deposit of low strength, must be removed before any concrete poured so new will bond to old
Compressive strength of concrete
28 days after being placed, 3000-6000 psi, 4000 most common; high early strength reaches compressive strength in 7-14 days
most common reinforcing types
ASTM A 615 billet steel, 40, 40,000 psi; ASTM A 616 rail steel, 50, 50,000 psi; ASTM 617 axle steel, 60, 60,000 psi (most common in buildings), A706 low alloy, 75, 75,000 psi
Number system
mill, bar size in 1/8” increments, type of steel, grade
Welded wire fabric naming conventions; WWF 6x6 - W2.9.
6” o.c. in each direction; cross sectional area is 2.9/100=0.029 sq in (6 gauge)
appropriate reinforcing coverage rules of thumb for retaining walls, beams and columns, slabs, and footings
footings need 3” between steel and ground; retaining wall 2” concrete cover, beams & columns 1-1/2”, slabs 3/4”
Structural lightweight concrete
90-115 lbs/ cubic foot; max size of coarse aggregate 3/4”; air entrainment almost always used, handling and placing easier; modulus of elasticity lower (deflection greater); drying shrinkage greater; thermal insulation better; more costly
Insulating lightweight concrete
thermal insulation in roof construction; 15-90 pounds per cubic foot; low compressive strength; aggregate: perlite/vermiculite; some w/ no fine aggregate to leave voids
Gunite
shot into place with compressed air, good for large surface with thin sections (pneumatically)
Slump test
consistency & workability; performed in field; cone filled directly from mixer in 3 layers, rodded each layer, top layer leveled; slump difference acceptable 2”-6”, then tapped gently to indicate workability
cylinder test
compressive strength, standard 6” diameter cylinder 12” long, 2 cylinders, lab cured for 7 & 28 days, tests crushing; if fails 2”-4” cores taken from areas suspected to be deficient
kelly ball test
measures workability; 30 lb, 6” diameter ball dropped from standard height, penetration measured, relates directly to slump
impact hammer test
rebound of spring-loaded plunger measured after strikes smooth concrete surface (approximates concrete strength)
Single tee pre-stressed concrete
5’, 8’, 10-0” wide; 80’, 100’, 120’ span
Double tee pre-stressed concrete
4’-0” wide; 20’-0” - 36’-0” span
pre-tensioning
steel stretched & tensioned before concrete poured, after steel is cut, creep, shrinkage, slip & friction occurs
post-tensioning
concrete cast with sleeve, cured, then jacked to compress, steel locked with end anchors & grouted, loss after tensioning by friction, elastic shortening, & shrinkage less than with pretensioning; greater compressive strength required 5,000 psi or greater; high strength bars, single wires, wire strands
Benefits of pre-cast concrete
better quality control, better control of curing, members castable in all weather, members erectable in all weather, faster actual construction times; types include: hollow core, tongue & groove, channel, double tee, lightweight concrete planks, nailable planks, tongue & groove concrete planking
Tilt up construction size
5-8” thick, span between columns & footings; SOG common, mechanical pipes, conduits, ducts can be installed ong rade
Tube slab
paper tube fillers embedded in section, flat ceiling 2/ no beams, mechanical & duct systems run through thickness
terrazzo
mixture of portland cement & water (matrix) & colored marble granules, then ground down floors, walls, wainscots, stars, etc.
