BDC - Masonry & Concrete Flashcards
what did the ancient romans add to concrete to make it set under water?
pozzolana or volcanic ash
who developed portland cement?
Joseph Aspdin on 1824
who advanced concrete for construction in the earth 20th cen?
Robert Maillart & designed bridges and industrial buildings.
who designed the exhibition hall in Turin?
Pier Luigi Nervi
name 3 different types of forms?
1) Plywood (cheep) 2) Pre fab steel (strength and reusability) 3) Glass fiber reinforced plastic
what is a tie hold in conc forms?
the round imprint of a disk thats left after formwork is removed.
what is a flying form?
typ used in highrise construction, you form up and cast a floor section then fly-out or remove that section to be used in upper floors.
what is the max tolerance for a concrete column?
1/4” / 10’
what is the max tolerance for a concrete floor?
1/8” / 10’ for intended flat slabs
in fresh conc slabs what is the recommended water content ratio be to accept floor finishes?
.45 to .50 & conc slabs should be allowed to cure & dry for a minimum of 6 weeks before flooring is installed
what is a vapor barrier?
its placed under a slab (above any subbase) and it stops moisture migration through the slab. A barrier prevents water vapor from passing.
what is a vapor retarder?
it only slows the rate of water vapor transmission. Its acceptable permeance is between .04 & 10 mills
what is a perm & how is it measured?
Permeance: its a measure of a materials resistance to water vapor transmission, expressed in perms. A perm is the passage of one grain of water vapor per hour threw one square foot of material at a pressure of one inch of mercury between the two sides.
what is the grade mean in rebar?
typ used grades 50 & 60, these refer to the yield strength measured in Kipps / square inch.
what are the basic components of concrete?
Cement, aggregate & water
What is portland cement?
its the bonding agent in concrete, its made from lime, silica, iron oxide & alumina it chemically reacts with water to form a paste that binds with the aggregate.
what are the 5 types of concrete?
Type I: called standard its used for most general construction. Type II: is called modified and is used in places where modest amounts of sulfate resistance is needed Type III: is high-early-strength and is used where quick set is needed. Its also suitable for cold weather locations. Type IV: is used in massive structures to minimize cracking and is called low heat. Type V: os sulfate resisting cement, and is used for structures exposed to water or soil with high alkaline content.
what is the minimum water-cement ratio for concrete?
.35 to .40 by weight.
what % do aggregates typically occupy of the total volume of concrete?
70 to 75%
what kind of aggregate is added to increase insulation in conc?
pumice or cinders. Light weight concretes = better insulating concretes
what is the typical ratio of cement to sand to gravel
1:2:4 1 part cement, 2 parts sand and 4 parts gravel
what are 6 different types of concrete additives?
AIR-ENTRAINING: form tiny dispersed bubbles, increases the workability of concrete & improves resistance to freeze. ACCELERATORS: speed up the hydration process PLASTICIZERS: reduces the amount of water needed (higher strength) RETARDERS: slows down the setting time to help reduce the heat of hydration. WATERPROOFING: agents decrease the permeability of conc. FLY ASH: increases strength & decrease permeability.
how does concrete cure?
it gains strength by curing threw a chemical reaction between the water & the cement rather than by drying. Concrete gains ~70% of its strength after the first week of curing. 28 days is for its design strength,
what is the slump test
it measures consistency of the concrete.
what is the cylinder test
it measures compressive strength.
what is a core cylinder test
a cylinder is drilled out of a already cast and cured conc. and taken to a lab to determine the compressive strength.
what is the Kelly Ball test?
a steel ball is dropped onto a slab of freshly laid concrete. The amount of penetration of the ball into the concrete.
What is the impact hammer test?
a non destructive way to test conc strength after it has harned. a spring loaded plunger is snapped against a conc surface
what is the calcium chloride test?
its a common test that test for moisture in concrete.
what is the electrical impedance test?
it is used proprietary meters to determine the moisture content in concrete by measuring conductance & capacitance. Probes of the meter are placed on the concrete & the percentage of moisture content in the slab is read out directly.
what is the typ pH level of concrete?
12 to 13 making it alkalinic.
what is a tremie?
its a long cylinder tube or chute used for distributing concrete for underwater applications.
what is the typical vertical distance concrete should be dropped to avoid segregation (the separation of sand, aggregate and water)
5’
what is a control joint?
creates a weak section so that normal temperature & stress cracking occurs along the joint
what is a construction joint?
its the connection of two successive pours of concrete. Typically there is rebar that dowels the two sections together.
what is an expansion joint?
it allows entire sections of a concrete structure to move independently.
what is an isolation joint?
it allows two adjacent sections to move independently.
whats the difference between surface sealers and penetrating sealers?
SURFACE: dries on the surface and can in time be worn off. PENETRATING: they seep into the tiny pores of the concrete.
What are the components of mortar?
lime (retains the water), sand (aggregate) , cement & water
what are the 4 types of Mortar?
M: S: N: O:
what is the most common brick size?
7 5/8”x 3 5/8” x 2 1/4”
on a single wythe wall what is the max ratio of unsupported height or length thickness can’t exceed
20:1
what is the typical spacing for horizontal brick reinforcement?
16” vertical
what is a reinforced grouted masonry wall?
its a double wythe but the cavity contains the vertical and horizontal reinforcing.
What is a proper weep hole spacing in a masonry wall?
24” o.c.
in masonry what is the order of dimensions a manufacturer will provide?
Width x Height x Length WHL
what type of construction is best to limit vibration?
conc slab and beam
what is composite steel deck?
In a composite steel deck, the dissimilar materials in question are steel and concrete. A composite steel deck combines the tensile strength of steel with the compressive strength of concrete to improve design efficiency and reduce the material necessary to cover a given area. Additionally, composite steel decks supported by composite steel joists can span greater distances between supporting elements and have reduced live load deflection in comparison to previous construction methods.[5
what does the grade of rebar stand for?
the grade number refers to the yiel strength in kips/ sq inch
what would w wire grid designated as 6x6-W1.4 x1.4 mean?
the grid is 6x6 & the size of wire is 1.4 hundredths of a square. the W = smooth wire (A D= deformed wire).
the passage of water under pressure through concrete cracks is defined as?
seepage
what is Self Consolidating Concrete?
its a mix that can be placed purely by means of its own weight without vibration. SCC is made possible with the ise of a superplasticizer.
what is it called when conc heats during curing?
heat hydration.
what does a slump test test?
measure consistency and the amount of water in the mox.
what does a cylinder test measure?
compressive strength.
what is the impact hammer test in concrete?
a spring loaded plunger is snapped against a conc surface & the amount of rebound is measured. this gives an approx reading of the concrete strength,
how is high Alkalinity a problem for concrete?
it can damage finish installation.
why is generally dropping concrete longer than 5’ bad?
it can produce segregation which is he separation of the aggregates , water & sand.
how is lime used in mortar?
Lime helps to retain water in the mortar for hydration, a mortar with a high lime content is appropriate for bricks with a high initial rate of absorption or for summer construction where evaporation is a concern
What is this pattern?
Cross Bond
what is this pattern?
Common Bond
what is this bond pattern?
Flemish bond
