particle size

bearing capacity

drainage ability

gravel

sand

silt

clay

horizontal boards nailed to posts set at the corners of an excavation, used to indicate the desired level

also as a fastening for stretched strings to indicate outlines of foundation walls

used when the load-carrying capacity of subsoil is consistent

depth of foundation = "depth at risk of frost heave"

deep foundation

used when the load-bearing capacity of subsoil is inconsistent or inadequate near the surface.

depth of foundation = depth of loadbearing stratum

used when water table is high, often to contain groundwater

dig into ground

fill cavity with bentonite clay

put reinforced stell cage into cavity

pour concrete in while siphoning out the clay

excavate one side of wall

anchor wall to earth

(aka seismic isolation system) - earthquake engineering

alternating steel and rubber plates at bottom of foundation to allow movement (especially in an earthquake)

question of architecture and the ground

"unbuildable" site due to steep slope and unstable ground

retaining wall architecture

2 big "pieces" = 2 fields and parking

"lifted ground" created with roofs

concrete recipe

1 : 2 : 3

1 part Portland Cement

2 parts sand

3 parts aggregate and water*

* amount depends on weather, distance traveling, time, workability desired 

concrete does not dry, it CURES

concrete likes to cure at 70 degrees, but can do so in cooler temperatures.  Can't FREEZE, however.  

dry, powder, inorganic, large quantities

controversial use of FLY ASH

coloring agents

chemical, liquid, improve quality of concrete

super-plasticizers, air-entraining, retarders, stabilizers

adding water at site

excessive vertical drop (more than 4')

excessive horizontal dragging

holes that occur in concrete, especially at corners.

mostly cosmetic, but sometimes becomes a structural issue

indicates problem in pouring concrete - vibrating or mixture