Flashcards
Concrete stage 2
Cards in this deck (39)
- 1What is 'embodied energy' in concrete?The energy consumed by all of the processes associated with the creation of concrete. Includes:
- Aggregate mining/processing
- Cement production (including material sourcing and kiln heating)
- Water (processing) - 2What is 'embodied carbon dioxide' in concrete?The greenhouse gas emissions arising from the manufacturing, transportation, installation, maintenance and disposal of concrete
- 3What are the negative environmental contributions of portland cement manufacturing?- Carbon dioxide production (1ton of CO2 per1 ton of cement (roughly))
- Biodiversity loss from material sourcing
- Air pollution
- Erosion & sedimentation (due to disturbances in soil and vegetation during extraction
(https://ukgbc.org/our-work/topics/embodied-ecological-impacts/cement/) - 4Define 'compression' with regard to beams, slabs and columns under loadCompression is force applied inwards from alternate sides of a beam, slab or column
- 5Define 'tension' with regard to beams, slabs and columns under loadTension is the stress which 'elongates' a beam, slab or column
- 6Define 'shear' with regard to beams, slabs and columns under loadShear strength in concrete is defined an 'an ability to resist forces that tend to induce sliding of one part over another at an internal plane'
- depends on concrete grate, percentage of fibres/tension steel
- Shear Modulus (G or µ) - ratio of shear stress to shear strain
(https://www.ijert.org/research/shear-strength-compressive-strength-and-workability-characteristics-of-concretes-reinforced-with-steel-fibres-IJERTV8IS060035.pdf) - 7Define 'bending/flexure' with regard to beams, slabs and columns under loadBending characterises the behaviour of a beam, slab or column under external pressure applied perpendicularly to the longitudinal axis
- 8Define 'flexural strength' with regard to beams, slabs and columns under loadFlexural strength is the ability for a beam, slab or column to resist bending/flexure
- 9Define 'torsion' with regard to beams, slabs and columns under loadTorsion is 'twisting' like force which can result from eccentric loading, curved geometry of lateral restraint.
- must maintain a uniform stress distribution - 10Define 'stress'Stress is a force divided by the area over which it is applied
- 1kg = 10 N applied over 1m2 =10Pa
- 1kg = 10 N applied over 1mm2 =10MPa - 11Define 'strain'The movement caused by the 'stress' that the concrete was placed under
- 12Describe the phases of stress vs strain behaviour of concrete under load- Elastic phase - the stress and strain are proportional
- Peak point - concrete begins to show 'plastic (non linear) behaviour' followed by plateau
- Descent - decrease in maximum compressive strength while increase in strain - 13What is the 'modulus of elasticity (E-value)' in concrete?The slope of the 'elastic' phase of the stress-strain curve.
Known as the 'stiffness' of the concrete
As the E value increases the 'stiffer' the concrete becomes
- Young's Modulus (E) - ratio of linear stress to linear strain - 14What is elasticity?The ability of a material to regain its original shape after deforming under stress
- 15What is 'creep'?Creep is the increase in strain (movement of deflection) under sustained constant stress (load)
- 16How is 'compressive strength' measured?Compressive strength is measured by breaking a cubical or cylindrical concrete specimens in a compressive testing machine.
- 17How is 'compressive strength' calculated?Compressive strength is calculated by dividing the failure load by the load area and reported in Megapascals (MPa)
- 18How is 'flexural strength' measured?By applying load (either center-point or third point (at each third)) between 2 points (of length at least 3 times the depth) until failure
- 19How is flexural strength expressed?Modulus of Rupture (MP) in MPa)
- 20Up to what % Cement can be replaced with GGBFS?Up to 80%
- 21Up to what % Cement can be replaced with Fly AshUp to 60%
- 22What is biodiversity?The total population of organisms in a certain environment
Eg. animals, plants, micro-organisms etc - 23How can aggregate extraction/sourcing be more 'responsible'?- Understand the local species
- Understand how to limit the disturbance
- Understand how to better 'reinstate' following quarrying (how to best re-create a similar environment) - 24What is 'life cycle assessment (LCA)'?The investigation and evaluation of the environmental impacts of production/process/service over the whole life span.
eg. raw material sourcing, energy use, waste management - 25What does the EMS (environmental management system) consist of?- Environmental policy
- Planning
- Implementation and operation
- Checking
- Management review - 26What is 'Portland cement'?Cement obtained by mixing calcareous (limestone) and argillaceous (clay or shaly) (or silica-, alumina-, iron- oxide bearing materials) and burning them at clinkering temperature, and then grinding the clinker into a fine dust
- 27What is a calcareous material?A material containing/consisting of calcium carbonate
eg, chalk, limestone - 28What is an argillaceous material?A material containing/consisting of clay
eg, shale, clay - 29What are the main steps of Portland cement production?- Grind raw materials
- mix raw materials
- burn in kiln
- grind with addition of gypsum - 30What is the general kiln temperature range?1300-1500°C
- 31What % gypsum is added?3-5%
- 32What are the main steps of 'wet process' cement production?- Grind raw materials and mix with water into a slurry
- Agitate slurry in slurry tank
- Spray into rotary kiln - 33How is a kiln heated?Coal, oil, natural gas (sometimes by burning recycled tyres)
- 34What happens inside the kiln?- 20-30% of the materials fuse
- Lime, silica and alumina get 'recombined'
- Fused mass becomes nodular (3mm-20mm) clinker - 35What's the main purpose of the addition of gypsum in cement?To prevent flash setting
- 36What is 'flash set'?Flash set refers to a rapid development of rigidity, usually due to too little gypsum
- Flash sets often produce a large amount of heat - 37What is 'false set'?False set refers to a rigidity in the form of a plaster (of Paris) like paste which can be worked into concrete
- Caused by dehydrated gypsum (can happen if gypsum is added to hot clinker in the grinding mill)
- Does not produce very much heat - 38What are the main steps of 'dry process' cement production?- Raw materials are crushed and proportioned into a grinding mill (where they are dried and turned into 'raw meal' a fine powder)
- Raw meal is blended/mixed via compressed air
- Blended meal is sieved
- fed into granulator where water (at 12% weight) is added to make the blended meal into pallets
- Fed into kiln - 39What are the benefits of 'dry process' over 'wet process' cement production?- Equipment is smaller
- Consumes 2/7th the coal needed in wet process
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- Concrete Technology Flashcards on Concrete stage 2, created by Fraser Hunter on 13/01/2025.
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- Fraser Hunter · Jan 2025
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- Jan 15, 2025
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