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igneous rocks

formed by cooling from a melt. crystal structure

sedimetary rocks

formed from erosion of existing rocks. weaker than igneous

metamorphic rocks

formed by application of intense heat and pressure. stronger than sedimentary

fine particles

coarse particles

>5mm

max agg size

the smallest SEIVE opening

Nominal agg size

smallest seive size that majority of sample passes through

__ is preferred for workability of conc

rounded agg

___ is preferred in mechanical properties of portland cement

angular

OD (oven dry)

all moisture is removed

AD (AIR DRY)

all moisture is removed from surface but not from pores

pores are partially full

SSD (saturated surface dry)

all aggregate pores are full but surface is dry

wet or moist

agg pores are completely filled and there is a film of water on the surface of particles

surface/free water

moisture in excess in SSD state

specific gravity

ratio of agg mass to mass of an equal vol of water

what does strength and toughness depend on

bonding between the grains

porosity of particles

what is freeze thaw

when water is in agg pores and freezes and expands

* will create fractures in agg
* causes popout in portland cement
* causes cracking in concrete

what is a deletrious substance

organic impurities that delay setting and reduce strength of portland cement

Alkali silica reaction

silica in aggregates react with alkali hydroxides in concrete

* causes excessive expansion in cement paste

C3S properties

early strength gain

50-70% mass

C2S

late strength gain

15-30% mass

C3A

flash set

5-10% mass

generates heat in early hydration

C4AF

flash set

give concrete its colour

1-10%

flash set

rapid development of ridgitity with considerable heat evolution

false set

rapid development of ridgitiy without heat

name all of the stages

stage 1: Rapid heat evolution

stage 2: period of realitive inactivity

stage 3:initial set (2-4 hrs)

stage 4: reaction slows down

stage 5: steady state (18-36 hrs)

rate comp strength of c3s, c2s, c3a, c4af

types of portland cement

GU

HE

MS

HS

MH

LH

GU - general use

no specific requirements

HS - High early strength concrete

reduced c2s

increased c3s

used in cold weather

MS - moderate sulphate resistence

reduced c3a (5-8%)

normal structures exposed to soil or ground water

low w/cm ratio

HS - High sulphate resistence

reduced c3a (

MH - moderate heat of hydration

reduced c3a (5-8%)

generates less heat than GU

hydrates slower than GU

for structures of considerable mass

good for warm weather

LH - low heat of hydration

reduced c3s

increased c2s

develops strength slower

for massive structures

what is concrete composed of

coarse agg

cementing material

water

sand

admixtures

conc advantages

* can be cast into any shape
* can use local materials (low cost)
* very durable
* fire resistant
* efficient to produce

limitations of conc

* brittle material
* low strength to weight ratio
* irriversible shrinkage

workabilitu factors

* concrete consistency
* water content
* aggregate size, texture, grading
* uniform distribution of agg

fresh con should be plastic and semi fluid

what is consolodation

vibrate fresh concrete to make sure there arent any bugholes

moves around particles to avoid friction and increase mobility

\

what is air entrained concrete

has small air bubbles to resist freeze thaw damage and improve workability and durability

\
\*lowers compressive strength

stress strain graph of highstrngth concrete

has sharper peaks and sudden failiure characteristics

types of concrete voids in hardened concrete

* entrapped voids
* macro cracks
* entrained voids
* microcracks
* transition zone
* capillary voids

entrapped voids

rock pockets

honeycomb

voids pf incomplete consolidation

macro cracks

visible cracks

* structural
* thermal
* plastic damage
* drying shrinkage

severe effect on concrete durability

entrained voids

reduces strength significantly

intentional for freeze thaw

micro cracks

naturally occur around aggregates from restraint shrinkage

as load increases, microcracks increase

influence durability and strength

transition zone

weak and porus around aggregates

influence durability and strength

capillary voids

residue from water filled spaces

significantly reduces strength

why is stress strain curve of concrete not linear

because it is a composite material of agg and cement paste

if cement paste and agg have similar strength and modulus of elasticity, the conc one will be more linear

what is maturity index

strength of conc depends on time and temp

samples with same maturity index have equal strength

how to prevent bugholes in concrete

reduce amount of sand in mix

thoughroughy internally vibrate

how to prevent consolodation

reduce amount of coarse particles

or

increase sand

insert at 600mm intervals and vibrate

concrete curing methods to MAINTAIN mixing water

* ponding
* spraying
* wet coverings

concrete curing methods to PREVENT LOSS mixing water

* impervious paper
* plastic sheets
* membrane forming compounds

types of shrinkage

plastic shrinkage

drying shrinkage

what is plastic shrinkage

when conc looses moisture

may cause cracking

drying shrinkage

when conc is not properly cured

development of cracks

how to prevent shrinkage

use proper curing

low water cement ratio

low cement content and high agg content

what is creep

gradual increase in strain over time

sustained load over a long period of time

affects stress reinforcement and increases deflection

types of asphalt pavement

flexible

ridgid

types of asphalt

asphalt cement

asphalt binder

asphalt cutback

asphalt cement

excellent adhesion characteristics

blend of carbohydrates

semisolid material

asphalt emulsiion

produced by dispersing asphalt cement in water

60-70% A Cement

30-40% water

asphalt cutback

produced by dissolving A cement in hydrocarbin solvent

asphalt binder acts as a newtonian fluid when…

Temp > Tg (140 C)

asphalt binder acts as a viscoelastic solid when…

Temp < Tg

asphalt binder acts as a very brittle matrial when…

very low temp

physical properties of asphalt

aging

viscosity

stiffness

tensile properties

aging of A cement

caused by going through a wide range of temps

asphalt becomes less ductile and hardens

volitization of hydrocarbons

oxidization

viscocity of asphalt cement

if temp goes up, viscosity goes down

low viscosity = rutting and bleeding

high viscoisty = thermal cracking

stiffness of asphalt

low temp and short duration = elastic behavior

high temp long duration = depends on viscosity

draw out asphaplt denisty distribution

VTM

voids in total mix

total vol of small pockets of air btwn COATED agg particles

VMA

voinds in mineral agg

voids between agg particles

VFA

voids filled with asphalt

portion of voids in agg that is filled with binder

advantages of wood

aesthetic

adequate strength:weight

cost effective

renewable resource

minimum pollution

disadvantages of wood

fire

bacteria

insects

imperfections

endogenous trees

intertwined growth

strong and lightweight

not used for eng projects

exogenous

outward growth

conncentric rings

eng applications

what are the orthogonal directions of wood

draw them

longitudinal

radial

tangential

what is fibre saturation point

point at which cell walls are compleetly saturated but the cavities are empty

\
no free water

only bound water

\
when MC 25-30%

compressive strength paralell to wood grain

good

wood cells act as tiny colums

compressive strength perpendicular to wood grain

increases with deformation

\
max comp @ decrese thickness by 1/3

tensile strength parallell to wood grain

strong

felxural strength of wood

very strong in bending

failiure in compression side

types of wood defects

knots

checks

shakes

wanes

warp

what are the most important design parameters

strength and ductility

when we increase carbon content in steel, what happens

strength increase

hardness increase

ductility decrease

toughness decrease

what is ductility

ability of a member to undergo large deformations without fracture

advantages of steel

linear service bahavior

high strength

high E

high ductility

simialr tension and comp behavior

disadvantages of steel

buckling

continous maintences

fireproofing cost

\

steel production - blast furnace

reduces ore to iron

steel production - oxygen furnace

removes excess carbon

what is allyoing

adding carbon into structure of iron atoms

what is work/strain hardening - cold rolling

passing metal through roller

increases yeild and tensile strength

compresses structure

what is work/strain hardening - strain aging

loaded sample to strain hardening range and leave at room temp

what is heat treatment of steel

reheating and cooling metal to reorganize microstructure

cooling metal slowly does..

more ductile metal

ferrite and pearlite at equilibrium arrangement

cooling metal fast does..

more britttle and harder

forms marntensite

advantages of FRP

duracble

will not corrode'

low thermal conductivty

versatile