Form work and reinforcement

job built forms

one time use

prefabricated job-built forms

can be reused

manufactured forms

purchased or leased

special form

used for specific situations

fiber tube forms

if over 15 feet they require stiffeners

insulating concrete forms

hollow foam blocks; stay in place; assembled as interlocking blocks

tunnel forms

made of steel or aluminum and combine the walls on either side of teh room

duplex nails

used in forms where nails must be removed when form is stripped; double headed nails

how much does concrete weigh

150 lbs per cubic foot

what are the 3 most important factors influencing pressure

concrete temp, rate of placement and concrete weight

rate of pour

determines lateral pressure put on form work; slower placement means lateral pressure at the bottom is less than full fluid pressure

barrier type release agent

oil-based product; diesel oil is a typical release agent

chemically reactive form release

contains some fatty acid which reacts w/ the lime in concrete to form metallic soap; slipping form off

what is the max drop distance of release agent

5 feet

who is needed to specify minimum concrete strength to remove forms

an engineer

pullout measuring

measures force to pull out metal insert from concrete

penetration measuring

measures force required for steel bar to penetrate concrete column

maturity meter

measures temp progression; correlation between temp and concrete strength

what is added in concrete to resist tensile forces

steel reinforcement

prestressed concrete

internal stresses introduced to combat outside/ tensile forces

epoxy coated bar

used as rebar in areas where corrosion is common

concrete cover

distance from outside of the bar reinforcement to concrete surface