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What is the nominal maximum size of aggregate?
smallest sieve size which 85%-85% of sample passes
What is the maximum size aggregate?
Smallest sieve size that 100% of sample passes.
What is Fineness modulus and how to calculate it?
Measure of the fineness of aggregate, higher the FM the coarser the sample. Sum of the cumulative percentage weight retained on sieves 10mm-0.160mm
What are the four moisture states of aggregate?
- 1-Oven dry - no moisture
- 2-Air dry - only moisture within the pores
- 3-Saturated surface dry - pores are filled to capacity
- 4-Wet - pores are filled and film on exterior
What is a Deleterious substance?
Any material tthat adversely affects the quality of concrete, ie: prganic impurites, clay lumps.
what are the four materials used in portland cement?
- Calcium Ca
- Silica SiO2
- Alumina Al2O3
- Iron Fe
What are the four parts of the Kiln?
- 1. Evaporation zone - removes all extra moisture
- 2. Calcinations zone - starts decomposing CO2
- 3. Clinkering zone - melts raw materials and forms clinker
- 4. Cooling zone
What are the four main compounds formed during the kiln process?
- Tricalcium Silicate 3Cao.SiO2 C3S
- Dicalcium Silicate 2CaO.SiO2 C2S
- Tricalcium Aluminate 3CaO.Al2O3 C3A
- Tetracalcium Aluminoferrite 4CaO.Al2O3.Fe2O3 C4AF
What is Flash set and how is it prevented?
Flash set is the rapid development of rigidity in cement, considerable heat from C3A and can not be overcome. Can be prevented by addition of gypsum.
What is False Set?
Rapid development of rigidity in cement, without the evolution of heat. Can be overcome by further mixing the concrete.
name the six types of cement?
- GU General Use
- HE High early strength concrete
- MSModerate sulphate resistance
- HS High sulphate resistance
- MH Moderate heat of hydration
- LH Low heat of hydration
What are the limitations of concrete?
- 1. Brittle material with low tensile strength.
- 2. Low strength to weight ratio
- 3. Irreversible shrinkage
What are the four concrete testing methods?
- 1. Slump test - measures the workability of normal concrete
- 2. Vebe test - used for very low workability concrete
- 3. Compacting factor test - measures compactability when falling under its own weight.
- 4. Flow table test - used for high workability concrete
What is asphalt aging?
Asphalt cement hardnes and becomes less ductile from exposure to a wide range of temperature changes.
what is the flash point of asphalt?
The temperature above which the asphault releases enouph vapour that can be ignited with a spark.
What is the difference between hardwood and soft wood?
Hardwood comes from trees that shed leaves. Softwood comes from evergreens.
What are the five layers of a tree?
- 1. Outer bark
- 2. Inner bark
- 3. Cambium
- 4. Sapwood
- 5. Heartwood
What directions does wood shrink in order?
Tangential > Radial > Longitudinal
What is the Free saturation point (FSP)?
The point when all the free water has evaporated. The mechanical and physical properties of wood are affected if the moisture content is below FSP.
What are the disadvantages of wood as a structural material?
What are the three phases of streel production?
- 1. Reduce iron ore to pig iron
- 2. Refine the pig iron to steel
- 3. Form the steel into usable shapes
What are the four components to electrochemical corrosion cell?
- 1. Anode and cathode
- 2. Oxygen
- 3. Moisture
- 4. Electrical connection
Methods of protection/controlling corrosion
- Protective Coating
- Galvanic coating
- Cathodic protection
- Corrosion resistance steels (alloys)
What is FRP?
Fibre reinforced polymer
What are the advantages of FRP?
- Resistant to corrosion
- high strength to weight ratio
- ease of application to rehabilitate
What is thermoplastic and thermoset?
Two types of resins. Thermosets can not be converted back to their original liquid form.