Site Cast Concrete

Site Cast Concrete “Concrete that is cast into forms on the construction site” Allen & Iano

Materials & Methods of Construction Department of Architecture University of Idaho Diane Armpriest, Assistant Professor

Site cast concrete process Concrete mix & placement Formwork Reinforcement Shoring & re-shoring Joints Finish

Concrete formwork  Concrete formwork   

Lumber & plywood Sheet steel & angles Glass fiber reinforced plastic

 Forms must be treated with release agent

before placing concrete and stripped when concrete has cured

 Formwork design is responsibility of contractor

1

Dimensional lumber used for ground-supported slab

Principles of reinforcing concrete  Proper reinforcement requires an adequate

amount of steel placed in the correct location  

Locate reinforcing bars where element is placed in tension. Locate stirrups near the ends of beams to resist shear forces.

 Adequate concrete cover to protect rebar

from corrosion

Column reinforcing

2

Beam Reinforcing

Elements of a site-cast concrete structure Slab on grade Wall Column Floor systems

Slab-on-grade diagram

3

Isolation Joint

Construction Joint

Joints Control Joints

control

control

4

Control Joints

Setting rebar and metal control joints in slab

5

Field Verification of reinforcement by Engineer

Underslab conditions prior to pour.

Isolation Joint

6

Construction joint

Hand leveling concrete driveway apron

7

Floating the slab

Machine floating large slab

8

9

Finishing & edging

10

Sawcut joints

Wall formwork: plywood and dimension lumber fastened with removable clamps and form ties.

Wall form

11

Exterior of formwork

Site cast concrete wall, Salk InstituteWall, Salk Institute, Louis I.Kahn

Construction joint in wall

12

Column Reinforcing Diagram

Steel and fiber formwork for round columns

13

Assembling Rebar Cages

Assembling column formwork

Completed Column

14

Self-climbing

Self-climbing formwork

Concrete Floor Systems

Beam supported

Beamless

15

Shoring & reshoring  Adjustable temporary shoring is used to

support formwork concrete for elevated concrete structures.  Re-shoring is used to support two curing floors after formwork is stripped.

Formwork and shores for elevated concrete slab

Flat plate slab

16

Flat plate slab w/ columncaps

flyingformwork

Post-tensioning

17

Cable-ends

Tightening cables

Floor formwork, reshoring, post-tensioned slab

18

Frame w/cables plugged

Beam supported slab

Joist slab diagram

19

Joist slab action

On-way joist slab formwork

Joist slab from below

20

Waffle slab diagram

Waffle slab formwork

Rib formed, bush-hammered

21

Board formed

Regulatory Issues

Fire Resistance Cover of reinforcement Slab thickness Seismic/lateral loads Joint strength

Advantages of site cast concrete Sculptural possibilities (“can do almost anything”) form surface texture Economical and structurally efficient when a standardized framing system is used More energy efficient to produce than steel Long-lasting Concrete is generally produced and available locally

22

Disadvantages Long on-site erection time prone to weather related delays Non-standardized construction can be very expensive.

TWA Terminal, New York, Eero Saarinen

TWA, Interior Stairs

23

Site-cast reinforced concrete frame

Columns vary with load and strength of concrete. Minimum dimension, 10 in. in either direction

Girders, beams & slabs

Depth of girders, beams and slabs vary based on:  frame design strategy  method of reinforcement Use Appendix B as a guide

24

Chart from Appendix B

Girders, beams & slabs

Estimate depth of slab if Span A = 40 ft.

A

25

Estimate depth of slab if Span A = 40 ft.

Assume post-tensioned slab. (Why?)

Slab thickness =

Span 45

= .8 ft, or 10-1/2 in.

26