Line G1 Flashcards
Concrete
What is the definition of plain concrete?
Concrete without any reinforcement
Thermal expansion of concrete or steel?
Interesting enough it’s the same both
Cement Pace bonds only two?
One. Aggregates
Two. Reinforcing steel
Three. Concrete forms.
For both steel and aggregates
Both steel and aggregates
Pre-stressed cement is?
Under tension at all times or in a state of precompression?
In a state of precompression
Pretensioning in cement is what?
Before concrete place
Which of the following shapes is not a type of concrete shell roof?
Barrel roof, dome roof, flat roof, folded plate roof,
Flat roof
What is the most common way to prevent telegraphing of forming materials for example the grain of a wood being left as an impression on the Finish concrete?
Liners made of rubber or plastic can prevent the telegraph in material and and can also be used to place patterns directly on the concrete
The term concrete means construction from
Bricks or blocks
Concrete with air entrainment has?
Microscopic air bubbles
I cement make sure applied with compressed air is called?
Air entertainment or Shortcreat
Shortcreat
Advantages of previous concrete?
All of the below
It’s environmentally friendly
Water percolates through into soil below.
May save material and labor
All of below
Three basic elements of concrete are?
Cement, water and aggregates
Rock like substance produced by Kiln is called
Clinkers
The four basic ingredients used to manufacture of cement are
Iron, silica, alumina and limestone
Normal porcelain cement is now known as?
GU cement
High early strength hydraulic cement is known? As
HE cement
LH cement is used for?
Low heat of hydration cement
Expansive cements cause concrete to?
Expand during setting
Good aggregate shapes should look like what?
Round and cubicle
Find aggregates are usually considered to be
Less than 5 mm
Good aggregates should be?
The clean hard and strong
An accelerator is an example of a?
Admixture
The masonry cement is best suited for foundation construction is?
Type s, type n, type m, type 10
Type M
A major greenhouse gas produced by cement industry is?
CO 2
A methodology to reduce the CO2 emissions during cement production is?
Decrease the amount of clinker used
Describe the steps to finish concrete once it’s been placed in the form?
Vibrate, strike off, float, wait for the bead water to evaporate, steel trovel
What is bead water?
Access water in the concrete mix not needed for hydration
How does concrete Harden and why is curing important?
Concrete hardens through a chemical reaction between water and cement. Curing making sure is there enough moisture to maintain the chemical reaction. 28 days of curing will allow concrete to reach its design strength
Concrete is 10 times stronger in compression or tension
Compression
What are the three fundamental properties that make concrete work with steel?
Thermal expansion is approximately the same for concrete and steel.
Cement pace and concrete bonds strongly to steal reinforcing
Concrete protects to steal against rust and corrosion
Reinforcing steel and concrete needs to overlap how much?
24 * the diameter of the bar
Calcium chloride should not be used as an accelerator in in cement that is when?
Reinforced with steel
Reinforce it still using a marine application should be
Coded with epoxy. Or made from beginning with steel or galvanized steel
There are four common shapes of concrete shell roofs.
What are they
Michelle roof has been built as thin as 50 mm.
Barrel, domes, hyperbolic paraoloids, folded plates.
What is used to make patterns in concrete?
Commonly used liners are made of rubber or plastic,
Brush hammering, sand and acid etching, or sandblasting
What is used to add to concrete to change its color even to make it pure white
Mineral oxide pigments
What is shot-crete (Gunnite)
Is the Portland cement concrete that is applied by pneumatic ally gun.
Can be used for restorative work on concrete structures damaged by weather or fire. They’re used on boat holes, landslide control facings for cliffs
What is Portland cement grout
It’s used for stabilizing foundations, making rock foundations under dams watertight and structurally sound feeling fraction cement work in ceiling oil wells. Non-trink grout is used for supporting machine bases
What is HS cement?
I high sulphate resistant hydraulic cement
Is used in concrete exposed to severe sulphate action.
Fine Arggregates are ?
5 and above if Crouse
Under 5mm or 4.9 and under are fine
When ready Mix concrete is not feasible what do you do?
The site made concrete is used if the job site is a long distance from urban center
What is the term tailgate placement mean?
Tailgate placement of concrete is only possible if the chute will reach the formwork of the concert or wheelbarrow it in
For a residential and commercial construction the benefits of using a crane pump is to place concrete into forms which enables what benefits?
Concrete pumps enable low slump concrete to be placed with ease, this allows water and cement ratio to be kept low as the cement strength is high. In some situations and concrete line pump is used instead of a concrete mounted pump
When a tower crane is used to move concrete on the site, what is utilized?
The crane uses a concrete bucket
On massive concrete construction projects what’s utilized?
Onsite batch plant
Where do you begin placement of concrete and formwork?
In the corners
Why should you not use a vibrator to move concrete?
It will cause segregation of the aggregates and to get the vibrator stuck
Why should concrete not be dropped?
It will cause segregation
All concrete must be placed into form work within how many minutes
Within 120 minutes from when the water was added to the minutes
Once concrete has been placed and vibrated then it is struck off at the correct height this is known as
Striking off, screeding
Once concrete has been placed and screeded level? What’s next
The surface is then floated. Floating pushes any large aggregates below the surface of the concrete slab this can be done with kneeboards and hand floats, bull floats or would power floats
When are control joints tool in to concrete?
After floating has occurred.
What is hydration in concrete?
Hydration is a chemical reaction that takes place when the water reacts with the cement in the concrete mixture, this chemical reaction grows the crystals that lock the grain and sand and rock together to form hardened concrete
The process of keeping concrete moist is called?
Curing
20 MPA concrete is able to cure for how many days?
28 days
Note! If cured for 7 days, concrete will attain over 90% of its 28-day strength
If concrete has kept moist continuously it will continue to gain strength for many years
Where are the common techniques to cure concrete?
The most common technique is to coat the surface of the concrete with a spray on liquid here in compound or to use an air barrier such as a plastic sheet to keep the water in the concrete from evaporating
Concrete can be cured by?
Water curing such as ponding, water retaining, mechanical barriers, chemical membranes
Aggregates occupied what percentage of the concrete’s volume?
60 to 80%
Oil well cements? Define
Well well cements, used for ceiling oil and gas Wells during drilling, are usually made from Portland cement clinker or blended hydraulic cements. Generally they must be slow setting and resist high temperature and pressure
Water Portland cement? Define
Adding a small amount of calcium, aluminum or other to porcelain cement clinker during the final grinding will produce a waterproof Portland cement the cured concrete will be either white or gray in color
What is plastic cement?
Plastic cement is made by adding plastic sizing agents up to 12% by total volume, to type 10 or 20 Portland cement during the milling operation. Plastic cement is often used for making mortar, plasters and stuccos
What kind of cement do you use for stucco, plaster, or mortar
Typically plastic cement
What is expansive cement
Expansive cement is hydraulic cement that expands during the early hardening. After setting. Normal types of cement shrink during the early hardening periods after setting. Expansive cements are used for patching cracks holes in concrete to help prevent water leaks. Expansive cements can also be used to concentrate for effects of decreased and concrete volume due to shrinkage drying
Random fact how much CO2 is concrete industry responsible for greenhouse gases
Approximately 7%
What is blended hydraulic cement?
Blended hydraulic cement sent at a lower rate than type 10 cement and generates less heat drain hydration. Pozzolan or blast furnace sex improved the properties of hardened concrete.
Blast furnace slag improves the properties of hardened concrete
What is masonry cement
Masonry cement is a mixture of Portland cement, Air entraining additions and supplementals, materials selected for their workability, plasticity and water retention. Because of manufacturing controls the workability strength and color of masonry cements are maintain a uniformly level. There are three basic types of masonry cement manufactured in Canada, type in, type s and type m.
Type n is mostly used for non load bearing situations such as work veneer
In masonry cement what is type s
Type s can be used for load bearing situations requiring a mid-range of compressive strength and walls that require some lateral strength such as a parapent walls.
In masonry cement what is a type m
Type m has a higher compressive strength then the other two types and can be used at or below grade. Type m is suitable cement for mortars used and foundations and with brakes design for use below grade. It’s mixed with sand and water to create a masonry motor
What is white cement?
White Portland cement cures to white color as opposed to normal Portland cement that cures to a great color.
It’s particularly used for architectural purposes such as a precast curtain wall and fencing panels, stucco, cement paint, tile grout and decorative concrete. It’s recommended when white or colored concrete or motor is desired
What is fly ash?
Fly ash is a pozzolan Is a admixture, it’s used by reducing the cement contact, the heat of the hydration is also reduced. Up to 20% of cement can be replaced with fly ash to reduce the cost of concrete mixture
To reduce the price of concrete mixture what could be added?
Flyash
100 ft length of concrete can expand up to how much when temperatures change from -20 to 20 degrees
Up to 9/16
Most pre-tension concrete is what?
Precast
When is post-tensioning done to concrete?
On the job site
The term concrete Masonry is typically applied to Precast blocks and building bricks molded of concrete. What is used to speed up the curing process in concrete? When it comes to making bricks
High pressure steam curing
What are the benefits of air entrainment?
One cubic metre of concrete has 46% of air entrainment. The air bubbles provide tiny Chambers for water to expand into as freezing and review relieves inner pressure on concrete during freezing and thawing. It’s also effective in preventing concrete surfaces from scaling when exposed to deicing chemicals
What is soil cement?
Soil cement is simply a hike contacted mixture of soil, Portland cement in water
When is soil cement used
Soil cement is mainly used for Paving roads, streets in airports
What are the benefits of fibre reinforced concrete
Fibre glass reinforcing is useful when there’s a danger of chemicals or corroding the steel reinforcing, used in tanks, pipes and boat Hulls
Self-leveling gypsum
Concrete reduces noise and acts as a fire separation between floors it’s great for self-leveling and requires no travelling or finishing and gives a uniform thickness, which finished floors can be placed over
What is previous concrete
And previous concrete is particularly mostly used on slab on ground type, driveways, parking lots and landscaped areas are common places to use previous concrete, and it’s fairly new
What are some of the advantages of previous concrete?
Typically water flows right through it into the soil below without affecting its stability, great for sidewalks
Portland cement is
Hydraulic cement, which means that it sets in hardens by reacting with water
What is GU, GUb, type 10 cement?
General use hydraulic cement, commonly known as Portland normal cement
What is MS, MSB type 20 cement?
Moderate sulphate resistant hydraulic cement,
It’s used in any situation when exposed to soil and groundwater we’re concentrations are higher than normal but not severe, seawater contains sulfate, concrete exposed to sea water is often made with Ms cement
MH,MHb, type 20
Moderate heat of hydration hydraulic cement, manufactured to generate less heat used in Mass structure such as large pillars and thick retaining walls and bulk foundations and it reduces temperature rise and should be considered being used during hot weather
HE , HEB, type 30 cement
High Early strength hydraulic cement,
High strength very quickly, usually in a week or less when it structures need to be put in service in a short period of time or in cold weather when short curing times are required high-rise construction and cold weather conditions are good for he cement
LH, lhb, type 40 Portland cement
Low heat of hydration hydraulic cement, intended for massive concrete structures such as gravity dams
HS, hsb, type 40 Portland cement
High sulpfate resistant hydraulic cement, again strength very slowly then g u cement designed to be exposed to severe sulphate.
What type of concrete is great for foundations?
Type M
.
.
When placing concrete in multiple layers , vibrate through each layer about?
6inchs 150mm
Is calcium chloride good accelerator for concrete?
Calcium chloride should not be used as an accelerated with concrete that is reinforced with steel
