Bulk materials and evaporites (part 2) Flashcards
What are fillers?
Chemically inert fine materials
Why are fillers used?
Added to provide bulk or to modify properties:
Weight
Toughness
Opacity
What are Barytes used as?
Industrial material but alos as a source of Barium
What are the properties of Barytes?
Heavy, non-abrasive, inert, non-corrosive, insoluble, non-toxic, high adsorption capacity for hard radiation
What are barytes ideal for mining?
Mud drilling as borehole lubrication
What is the global distribution of Barytes deposits?
Deposits found throughout world in a variety of geological environments
What are the three main types of barytes deposits?
stratiform, vein and residual
What industry are silicates a major part of?
The glass industry
What are the sourcess of glass made from silica?
Usually sources from crushed sandstone or pure beach sands
What are the properties of silica?
High melting point of quartz (1713 ̊C) and high viscosity when molten
What other elements can be added to silica to provide additional properties?
Soda
Lime
Alumina
Boron
Lead
Why is soda used in producing glass from silica?
lowers melting temperature (as low as 500 ̊C) but soluble
Why is lime used in producing glass from silica?
stabalising element and reduces solubility
Why is alumina used in producing glass from silica?
Increases chemical resistance
In larger quantities used for fibres and cooking utensils
Why is boron used in producing glass from silica?
resistant to corrosion and heating and cooling (pyrex)
Why is lead used in producing glass from silica?
for crystal tableware
How is glass coloured?
By the addition of mineral oxides
Why is blasting used?
to fragment competent rock or
to detach large blocks
What 2 primary methods are used to remove dimensional stone?
Drilling
Jet piercing
What is the process of drilling for dimensional stone?
vertical holes drilled about 3 cm apart to the desired depth (up to 7 m). Blocks then levered out or have secondary drilling
What is the process of jet piercing for dimensional stone?
high-velocity 4,000 degree flame directed at the rock to be removed, causing a continuous flaking action. As the flame nozzle is moved back and forth, a deep channel is created.
How is the process of blasting carried out?
drilled holes filled with explosive
(Ammonium Nitrate Fuel Oil (ANFO)
What is primary blasting?
working back faces, typically weekly and producing 15,000-20,000 tons per blast
What is secondary blasting?
more frequent, cleaning
up the working face and shattering large rocks.
What are quarry benches?
In hard rock quarries a series of layers in which the quarry is worked from top to bottom because the deposit is usually thicker than can safely be worked as one quarry face.
What sizes is the typical quarry face?
Quarry faces rarely > 15 m; in UK special assessments required if faces exceed this
Why is the width of quarry benches important?
Acts as protection for the lower levels of the quarry
Why is bench width important for the design of the final slope?
Access for restoration activities
Access ramps to the quarry floor
Feasibility of backfilling, or tipping loose material onto the bench
Feasibility of rock-fall protection measures
What is becoming the most common width for quarry benches?
8-12 m
What is the bench height determined by?
Width, strength and reach of equipment
What are the production volume figures linked to quarrying?
300Mt/yr
How much off the 300 million tons a year comes from sand and gravel?
120mt/yr (80% land extraction)
What is the average uk demand for aggregates for road construction and repair per year?
50-80 million tons
What is the majority of uk demand of aggregates for road co friction and repair for?
Crushed road stone
What 2 types of crushed road stone are wanted by the uk construction sector?
–Compacted aggregate for lower road layers
–Crushed aggregate bound in bitumen or cement for surface layers
Why is recyling of aggregates done and what is the limiting factor of this?
Reduce cost, environmental impact and increase sustainability but this has an effect on quality
What are the layers of road from top to bottom?
Surface dressing
Surf course
Base course
Sub base
Capping layer
Top 3 bitumen bound
Bottom 2 compacted, unbound
What is the purpose of the road surface layer for roads?
Dressing, surface course and binder course
Primarily to provide skid resistance and drainage
High Specification Aggregate (HSA)
What is the purpose of the base layers in road construction?
Base course, sub base, capping layer
provide strength and stability, to raise level, and to improve underlying groumdconditions
Not necessarily HSA
Why might high specification aggregate (HSA) be used?
remedial treatment
to prolong the life of the skid resistant surface
What material is often used as the high friction surfacing for roads?
Usually imported calcined bauxite
How is calcined bauxite produced?
hard aggregate produced by thermal decomposition at 1500 ̊C that removes volatile fraction
Where is calcined buaxite most used for road surfacing?
as an overlay where the highest levels of skid resistance are required
What test is used for aggregate strength?
Los Angeles Coefficient -L A
How does the Los Angeles coefficient work?
Determines how the aggregate will cope with crushing and impact forces
What do the results from the Los Angeles Coefficient mean?
Lower value = stronger aggregates
How is resistance to polishing measured?
Polished Stone Value (PSV)
Why is polishing a major factor in road construction?
Polishing in the wearing course reduces traction
What does the outcome from PSV show?
Higher PSV the greater the resistance to polishing
What are accepted values of PSV?
over 59 generally ok but over 65 is a high polish resistant aggregate sutiable for surface course
70+ for high stress zones
Where might a PSV of 70+ be needed?
High stress areas like approaches to roundabouts and junctions
What is used to measure the resistance to abrasion?
Aggregate Abrasion Value (AAV)
What to abrasion resistance equate to?
Toughness
What abrasion type will have limited use for roadstone?
One which erodes quickly
How is abrasion resistance calculated?
Percentage of rock lost after a set time of laboratory abrasion
Lower AAV the more resistant the aggregate is to abrasion; less than 10% highly desirable for road long jepidy
What is the downside to a material having a very low AAV?
Might not develop a good micro texture
PSV
AAV
LA
MS
What are the criteria for an aggregate to be considered a High Specification Aggregate? (HSA)
PSV - > or equal to 58
AAV - < or equal to 16
LA - < or equal to 30
MS - < less than or equal to 25%
HOw do evaporites form?
evaporation of seawater or
(more rarely) lake waters in large basins
Formed throughout geological ages
What is permeability of evaporites like?
Lowest permeability of all common rocks
What are some examples of how salt rocks can be used for underground storage?
– Storage of petroleum products
– Possible use for deep geological disposal for nuclear waste
What are types of salt deposits?
Stratiform
Vein & replacement
Residual
What are stratiform salt deposits?
– Formed by precipitation of minerals at/near bottom of water column in saline sedimentary basins
– Most extensive and economically viable deposits
What are vein& replacement salt deposits?
– Formed by precipitation from hot barium-enriched fluids in faults & fractures
– Very few worked
What are residual salt deposits?
Formed by dissolution of host rock vein or bedded deposits
What are the constituents of large evaporite sequences?
- Greater amounts of calcite, gypsum, halite
- K, Mg salts relatively rare
- Li locally abundant in some igneous contexts
WHat are the favourble physcial settings for large evaporite sequences?
– Arid climate
– Wide areas sea cut off from main ocean
– Narrow channel providing inflow
WHat is the processes of forming large evaporite sequences?
Evaporation > precipitation (e.g. rain) + inflow
Evaporation lowers water level
Concentration of salts increase
Heavier brine sinks to bottom and is trapped then
precipitates
What is the sucession of compounds precipitated in sucessive evaporation?
Precipitated gypsum
Precipitated halite
Precipitation of K and Mg
How does NaCl occur?
Rock salt (halite)
Solution (brine)
What are the uses of NaCl salt?
– Raw material for production of other chemicals
– de-icing roads
– food additive
– added to steel
What do salt domes form as a result of?
Relative buoyancy of salt (less dense) when
buried beneath other types of sediment
Salt forced through former roof and intruded younger sediments
Often triggered by tectonic events
Salt flows upward to form salt domes, sheets, pillars etc
What are salt domes a major source of?
Petroleum
What is solution mining of salts?
Vertical hole drilled into salt body
Fresh water injected
Brine pumped from near bottom of growing solution cavern
Like droitwich
How does UK halite occur?
Halite occurs in beds commonly associated with
mudstones
Most important salt deposits within Triassic Mercia Mudstone Group
What are the 2 sites of salt production in the UK?
– Cheshire (85%)
– North York Moors National Park
What is the primary use of phosphorus?
N, P and K fertilisers
What is the bulk compostion of phorphorus in the crust?
0.23% but also concentrated to economic levels
What is the main mineral of phorphorus?
Apatite
Who are the dominant producers of phosphorus?
USA, China, Morocco & Russia
What are the principle reserves of phosphorus?
sedimentary phosphorites but igneous reserves increasing production (world is running low on
cheap materials)
How are phosphorus sediments mined?
Due to being unconsolidated mined using drag lines and dredges
What is the main environemental impact of phophorus mining?
nutrient eutrophication as fertilizers washed into fluvial and marine systems
How are major phospahte accumulations formed?
Upwelling of cool phosphate-saturated seawater moved across shallow platforms & into near-coastal environments
Phosphate precipitated, probably by microbial processes
How abundant is potassium in the earths crust?
8th most abundant
What is the only setting in which potassium is economically extracted?
evaportite sequences
What is the distribution of potash bearing strata like in the uk?
- 1,200 and 1,500m deep
- seam ranging from 0–20m but
averaging 7m in thickness. - Within a Permian (Zechstein)
evaporite sequence
How is potassium extracted?
blasted or cut from mine walls and solution mining
What is the importance of potassium?
Vital for plant enzymes and regulating water content – major use as fertilizer
What are the general environmental impacts of N P K fertilisers?
Hypoxia and Eutrophication
What is hypoxia and how does it affect the environment?
Low oxygen levels (O2 < 2 ppm) in estuaries, lakes, and coastal waters
Insufficient O2 for fish and other aquatic organisms
What is eutrophication?
Excessive nutrients from land run off enter water systemstimulating dramatic plant growth as algal blooms reducing dissolved O2 in water and top sediment
Dead materials smothers bottom sediment and biota causing death of bottomdwelling organisms
DOM decomposes futher reducing dissolved O2
What can some of the toxins relased by algae cause?
harmful to both aquatic
animals and humans (e.g., gastroenteritis, headaches,
neurological problems, liver damage)
What name is given to the UK BArytes veins?
Missippi valley type
What problem is associated with glass recyling?
Dont know purity or solubility
WHat are the positves and negatives of Jet piercing?
High quality finish but very energy intensive
How many elevators will a deep mine have?
2
1 for people 1 for material
What is a platform bench?
Much larger base like area to quarry that might be mined in the future
How does the LA machine work?
Put 5kg sample in machine then use steel balls to abrade and weight sample broken off
WHat do you want for the micro texture of road surfaces?
Different crystals with different erosion rates to create uneven texture
WHat is HSA distribution problem?
Most needed in SE but most supply in W and N
