Lecture 10

Question 1

Slab On Grade

Answer 1

A concrete surface, lying upon, and continuously supported by, the ground beneath

Question 2

Suspended or Structural Concrete Slab

Answer 2

A slab that spans between

intermediate lines or points of support

Question 3

Casting a Concrete Slab on Grade

Answer 3

Site and organic top soil is removed.
Subgrade is excavated to required depth.
If the subsoil is too soft or unstable, it is over‐excavated and replaced with more competent material.

Question 4

Proof rolling

Answer 4

A heavy roller or loaded dump truck makes multiple passes over the subgrade.

Question 5

What is placed over the subgrade?

Answer 5

Crushed rock or gravel, usually 3⁄4‐ to 11⁄2‐in. diameter and 4‐6 in. deep

Question 6

Edge forms

Answer 6

Strips of wood or metal are placed to contain the concrete pour at the slab edges.

Question 7

Insulation

Answer 7

Rigid foam insulation may be placed over the drainage area and around the slab perimeter, to reduce heat losses through the slab.

Question 8

Vapor Retarder or Moisture Barrier

Answer 8

A heavy plastic sheet or other impervious material provides additional protection against subgrade moisture, and is especially important when the slab will receive moisture‐sensitive finishes.

Question 9

Wall Forms

Answer 9

Slender rods, called form ties, hold the forms in position and resist the outward pressure of the fluid concrete before the concrete hardens.

Question 10

Form Ties

Answer 10

Form ties can be made from steel rods, straps, wire, fiberglass, or other plastics.

Question 11

Striking off or Screeding

Answer 11

A wood plank or metal straightedge is drawn across the surface of the freshly poured concrete, using an end-to-end sawing motion

Question 12

Bull float

Answer 12

Drawn across surface after screeding (looks like flat mop)

Question 13

Darby

Answer 13

Used to float areas of the slab that can be reached without the long arm of the bull float