Division 3: Concrete Flashcards
One of the oldest manufactured building materials used as a mortar and plaster by early civilizations
Lime
The process of mixing quicklime with water is absorbed and heat is energetically evolved
Slaking or hydration
This may be used one half hour after being made into a putty
Special finishing hydrated lime
A type of lime which will set under water is
Hydraulic lime
The densest and hardest gypsum that can be applied with a trowel
Keene’s cement
Made by mixing slaked lime with pozzolana which hardened under the water
Cement
Who rediscovered hydraulic cement?
Smeaton, 1756
Who invented and patented portland cement
Aspdin
Obtained by finely pulverizing clinker produced by calcining to incipient fusion an intimate and proportioned mixture of argillaceous and calcareous materials
Portland cement
Components of portland cement
Tricalcium silicate 1/2 volume
Dicalcium silicate 1/4
Tricalcium aluminate 1/10 volume
Yeha
Each bag of portland cement holds
1 cu. ft weighs 94 lbs
Type of portland cement used when early removal of formwork is desired or in cold-weather construction
High early strength
Type of portland cement used in construction of massive concrete structures
Low heat: sulfate resisting
Quick setting cement
Alumina cement
Prepared mixtures of portland cement
Masonry cements
Cements made of natural raw materials
Natural cements
Type of cement made of lime mortar and pozzolanic material
Pozzolanic cement
Type of cement made of lime mortar and pozzolanic material
Pozzolanic cement
Storage of cement should be stored in shed with a wood floor raised about __ from the ground
12”
Piles should be limited to ___ sacks in height
12
The proportioned mixture of cement m, aggregate and water, which when properly proportioned is at first a plastic mass which can be cast or molded into predetermined size or shape
Concrete
Good quality concrete is obtained through
Careful selection of mayerial Correct proportioning Thorough mixing Careful transporting and placing Proper curing or protection of the concrete
measuring the consistency of a concrete mix
Slump test
The amount of water used per bag of cement
Water-cement ratio
Size of slump test metal cone
Bottom-8”
Top-4”
Height-12”
Consistency slump of reinforced foundation, walls and footings
Max and min
125mm(5”)
50mm(2”)
Consistency slump of plain footings, caissons and substructure walls
Max and min
100mm(4”)
25mm(1”)
Consistency slump of slabs, beams, thin reinforced walls & bldg columns
Max and min
150mm(6”)
75mm(3”)
The most widely used test for concrete compressive test
Compressive test
To test existing concrete structures by drawing out a core cylinder
Concrete Core test
The strength of a workable concrete mix depends upon the _______
Water-cement ratio
Economy of the mix depends upon the proper proportioning of
Fine and course aggregates
Methods of proportioning concrete includes:
Proportioning by arbitrary proportions.
By water-ratio and slump test.
By water-ratio, slump and fineness modulus.
Class AA
1:1.5:3
For concrete under water;retaining walls
Class A
1:2:4
For slabs, beams, columns, arches walls of 4” thk
Class B
1:2.5:5
Walls thicker than 4”, footings, steps, reinforced concrete slabs on fill
Class C
1:3:6
For plant boxes and non critical structures
Class D
1:3.5:7
For mass concrete works
Sufficient materials are placed at one time to make a convenient size batch of concrete
Batch Mixers
The materials are fed constantly and from which the concrete is discharged in a steady steam
Continuous mixers
The delivery from the mixer to the forms should be fairly continuous and uninterrupted not exceeding ____
30 mins
Concrete should never be allowed to drop freely over ___ for unexposed work and over ___ for exposed work.
5ft and 3 ft.
Reduction in volume of concrete or mortar or plaster caused by a loss of moisture
Drying shrinkage
Reduction in volume of concrete prior to its final set, caused by hydration of the cement paste
Setting shrinkage
Three main factors affecting the hardening
Age or time
Temperature
Moisture
Used to speed up setting time and to develop earlier strength to reduce length of time for protection.
Accelerators
Used during very hot weather to slow down the hydration of the cement.
Retarders
Manufactured from such as rosin, beef tallow, stereates, foaming agents(soap).
Air-entraining agents
Non metallic colored floor hardener
Flor-Hard
Preferred plywood for form construction
Phenolic board
Most commonly used plastic form
Polystyrene and ABS
Process of eliminating voids other than entrained air within newly placed concrete and ensuring close contact of the concrete
Consolidation
Done by the repeated insertions and withdrawals of a flat spade like tool
Spading
Repeated insertions and withdrawals of a rod
Rodding
Moderately high frequency oscillations of a vibrator
Vibration
Characterized by a low yield, high deformability and moderate viscosity
Self consolidating concrete or self-compacting concrete
Who conceptualized SCC?
Prof. Okamura
1986
Ouchi university, Japan
The separation of course aggregates from the mortar or from water from the ingredients of freshly mixed concrete
Segregation
Separation of an excessively wet or over-vibrated concrete mix
Stratification
Emergence of excess mixing water on the surface of newly placed concrete
Bleeding
Milky deposit containing cement and aggregate fines on the surface of new concrete
Laitance
Voids on a formed concrete surface caused by segregation during placement or by insufficient consolidation
Honeycomb
Chipping or scaling of a hardened concrete or masonry surface
Spalling or scaling
Appearance of numerous hairline cracks occuring in the surface of newly hardened concrete as a result of a rapid drying shrinkage
Crazing
Curing period:
Massive footings
1 day
Curing period:
Cantilever footings
5 days
Curing period:
Slab footings
5 days
Curing period:
Massive walls, 30 cm. thk
1 day
Curing period:
Thin walls less than 30 cm thk
2 days additional 1.5 days per meter
Curing period:
Columns: ratio of height at least diameter up to 4
2 days add 1 day per meter
Curing period:
Slab-3 to 7ft. Spans
5 days add 1/2 day per ft
Curing period:
Slab- over 7 ft. Span
7 days add 1 day per ft
Curing period:
Beams side
3 days
Curing period:
Beams and girders
Bottom
Up to 14 ft, 14 days add 1 day per ft
Curing period:
Spandrel walls
7 days
Curing period:
Spandrel arches
14 days
Main arches
21 days
Curing period:
RC piles and RC post
Sides- 3 days
Bottom-14 days
The bars may be plain or deformed( with lugs or projections for better bonding to the concrete)
Billet-steel bars or rail-steel bars
Steel bars size
1/8”- 1 1/2” and length 20 or 30 ft
Made of cold drawn steel wire widely used for the reinforcement of concrete slabs and floors
Wire fabric
Fabric consists of a series wires welded together to form a grid pattern.
Welder wire fabric/ woven wire fabric
(4”x4”,6x6,8/8) rolls 5 or 6 ft wide,
150,200 and 300 long
This is built up of either single or stranded longitudinal wires with cross wires or bond-wires running diagonally across the fabric.
Triangle mesh wire fabric
4” on center cross wires 4” or 8” apart
Stretched by pressure until the desired opening or forms are obtained. Can be shaped in diamond, crimp, herringbone and Z-rib
Expanded mesh
E.g. steelcrete
This is a lightweight, expanded structural concrete produced by adding a small amount of metallic aluminum powder to the mixture of portland cement and sand of cinders.
Aerocrete
This is the mixture of sand and cement deposited under high pneumatic pressure with a machine manufactured under the trade name “cement gun”
Gunite
A portland cement concrete to chich a chemical foam is added to generate gases in the process of deposition
Porete
This is processed concrete added with lightweight aggregate.
Haydite
Weighing from 25-60 lbs. per cu.ft is well qualified as a lightweight aggregate when dry and well graded.
Pumice
Composed of stable silicates and is inert and thus durable for use as a lightweight aggregate
Perlite
A micaceous mineral which expands on application of heat to as much as 30 times its original volume.
Vermiculite
Made by treating molten blast furnace slag with controlled quantities of water or steam.
Expanded Slag
Composed of the ash components of the coal along with the various quantities of unburned or partially burned combustible matter.
Cinders