___Concrete___Meredith / Flatt

What is Concrete?Concrete - Is a mixture of stone aggregates, sand,

Portland Cement and water that hardens as it dries.

Portland Cement - is a dry powder made by burning limestone and clay then grinding and mixing to an even consistency

History of Portland Cement

• In 1824, Joseph Aspdin, a bricklayer and mason in Leeds, England, took out a patent on a hydraulic cement that he called portland cement because its color resembled the stone quarried on the Isle of Portland off the British coast. Aspdin's method involved the careful proportioning of limestone and clay, pulverizing them, and burning the

mixture into clinker, which was then ground into finished cement.

What is Concrete?

• Mortar – is a mixture of Sand, Portland cement, water and Finishing lime.

Why Concrete?• Fireproof• Insect and Rodent Proof• Decay Resistant• Highly Storm Resistant• Wear Resistant • Water Proof • Strong• Attractive• Easy to use with little expense• Availability• Low Maintenance• Sanitary and easy to clean• Easily Recycled

Why Not Concrete?

• Will Shrink causing cracks• Wears away when exposed to moving water• Salt water will erode concrete• Low thermal conductivity so it will actually

help spread fire.

Types

• Ready Mix• High Strength• Fast Setting• Fence Post• Concrete Types

Importance of Silt Test

The Silt Test is key for looking at the sand that will be mixed in with concrete ingredients.

Ideally, you want a sandy loam or more course soil.

Sandy soil is helpful especially due to the shrinking and expansion of concrete.* If concrete doesn’t have this ability it can crack.

Silt Test

2” of sand

¾ of Jar Filled with water

1/8” Max

Mixing Concrete!

• You mix concrete to a ratio. The ratio is expressed in a 3 digit number called a Mix.

• EX: a 1-2-3 mix has 1 part cement, 2 parts fine aggregate (sand) and 3 parts coarse aggregate

Your goal for your ratio is to get a Workable Mix

Workable Mix

• Refers to the consistency of the wet concrete after the carious ingredients have been mixed together

Characteristics of a Workable Mix

– All aggregates are clean– No dry powder is present– No lumps – Uniform in color– Every particle of aggregate is covered with cement

paste– Mixture can be moved with a shovel

Just a Job

• Concrete Job Industry

Chemical Process• Concrete goes through a chemical process

known as “Hydration” Hydration – This is where The water reacts with

the cement, which bonds the other components together, eventually creating a stone-like material.

Chemical Admixtures

• Accelerators – Speed up the chemical process of Hydration (CaCl, NaCl)

• Retarders - Slow the hydration process down• Air Entrainments – trap air bubbles in the

concrete to reduce damage during Freeze/Thaw

• Pigments – Changes the color

Estimating Materials

• Don’t want to spend money on extra or be short on a job. (both cost $)

• Order in cubic yards• 1 cubic yard= 27 cubic feet • Formula

– Thickness’ X Length’ x Width’• You may have to convert inches to feet (divide by 12)

Example #1

• Determine the amount of cubic yards needed to pour a slab of concrete that is 4 inches thick 14 feet wide and 24 feet long?

• Convert inches to feet 4/12 = .33’ Thick• .33’ X 14’ x 24’= 111 cubic feet • Convert feet to yards 111/27 =

–4.12 Cubic Yards

Estimating Materials

• When ordering Concrete, always make sure you have enough.

• Add an additional 10%• 4.12 Cubic Yards x 1.10 = 4.53 Cubic Yards• Can we order ½ yards??????• Round up to the nearest yard….• Correct Answer is 5 yards

Example #2

• Determine the amount of concrete needed to pour a driveway slab of concrete that is 6 inches thick, 15 feet wide, and 22 feet long?

Convert inches to feet 6/12 = .5’ Thick

.5’ x 15’ x 22’=?

165 cubic feet

165/27 = 6.11 yards

+10% = 6.67 yardsOrder 7 yards

Practice Problems

Formulas

TRIANGLE – ½ (Base x Height) x Thickness

Rectangle – Length x Width x Thickness

Circle – (3.14 x Radius Squared) x Thickness

Formulas

Trapezoid – [1/2 (B1 + B2)] X Height x Thickness

Practice Problems

Triangle Court = Measures 20’ long x 12’ wide x 4” Deep?

ANSWER = 2 yards

50 Fence Posts = 2 feet deep x 1 foot diameter?

Pipe = 4” Diameter

50 Holes = 11.11 yards

50 Pipes = 3.88 yards

Subtract Pipe filled from holes: 7.23 yards

Add 10% = 7.953 or Order 8 yards

Preparing for a Form • Form – metal or wooden structure that

confines the concrete to the desired shape or form until it hardens.

• Footing or Footer – is the concrete base that provides a solid level foundation for brick stone or black walls.

Constructing Forms • Uses Soft, Clean, Straight lumber• Sharpen Stakes evenly so that they can be

driven in with ease• Place stakes 30 inches apart • Drive nails through stakes (duplex Nails) are

best

Constructing Forms

• Use wood sprayed with Diesel• Concrete stakes allow you to put at desired

height• Transit or level to determine desired slope• Average slope will be 1/2” fall over

10 ft distance.

Making Joints

• Construction Joint – place where one pouring stops and another starts

Making Joints Contd.

• Control Joint – Is a planned break which permits concrete to expand and contract without cracking. These joints are usually made with wood, galvanized metal or asphalt.

• Note – Control joints do not prevent concrete from raising.

Reinforced Concrete• Concrete can be strengthened by adding rebar,

fiberglass or wire mesh.

Wire Mesh Rebar

Reinforced Concrete Contd.

As a rule of thumb you should lap bars 24 times the diameter.

Ex. Rebar ½” should be put every 12 inches¾” should be lapped every 18 inches

• Rebar should be at least ¾” from the surface. On average it is 1 ½” below the surface

Pouring Concrete

• Must have all tools present concrete starts to set in 15 min.

• After spreading concrete you need to Screed it

• Screeding – moving a 2”X 4” back and forth to remove excess concrete

Pouring Concrete Contd.

• Then you will need to Tamp your concrete.• Tamping – this is the process of settling the

rocks at the bottom of your project.

Finishing

• Then you need to Float your projectFloating – bringing the fine aggregate (sand) to

the surface – this will make your concrete smooth.

Finishing Contd.

Broom Finish – will leave your concrete rough so that you will not slip

Pebble Finish - This will leave you with a rock finish (more aesthetic than structural)

Careers

• Cement Masons and Concrete Finishers• Concrete Pipe Manufacturing

Tools

EDGEREDGER

Tools

JOINTERJOINTER

Tools

MAGNESIUM FLOATMAGNESIUM FLOAT

Tools

FINISHING FLOATFINISHING FLOAT

Tools

WOOD FLOATWOOD FLOAT

Tools

BULL FLOATBULL FLOAT

Tools

POINTING TROWELPOINTING TROWEL

Tools

2 x 4

Curing ProcessCuring is the amount of time from consolidation

to it reaches your desired strengthConcrete takes hours to set But takes 28 days to

be cured!

Curing Process

During this time its important to keep the concrete moist so that you develop good resistance and strength.

Strength increases with age!!!

Game Time

• jeopardylabs.com/play/concrete-jeopardy.