FUNDAMENTALS OF CONCRETEFUNDAMENTALS OF CONCRETE

Presented By:

Kevin J. Brigandi Construction Services Department Manager

kjbrigandi@terracon.com

Debra A. NunesConstruction Services Department Manager

danunes@terracon.com

Uses of Concrete:

•Concrete can be formed in almost any color, shape and texture, while serving as an acoustic and thermal barrier•Concrete can be placed in all environments and conditions•Concrete is resistant to fire, chemical exposure and weather•Concrete is environmentally safe and recyclable•Concrete is efficient to construction and can be produced with a variety of durability characteristics and strengths

CONCRETE BASICS

Dams, Roads, Bridges and Parking structures

Buildings

Retaining Walls, Foundations and Flatwork

Driveways and Sidewalks

Interior Flooring & Countertops

Controlled Low Strength Material (CLSM)

Insulated Concrete Forms (ICF’s)

What is Concrete?

Chemical Admixtures

Mineral Admixtures

How Should Concrete Be Specified? Strength Water / Cement Ratio Air % Minimum Cement Factor Slump / Durability

Water / Cement Ratio Calculations

30 Gal 8.33 lb. 250 lb. ----------- X ------------ = ---------- = .44 W/C 6 Sack 94 lb. 564 lb.

30 Gal 8.33 lb. 250 lb. ----------- X ------------ = ---------- = .44 W/C 6 Sack 94 lb. 564 lb.

Adding Water to Concrete

Water Water added added

(gal/yd³)(gal/yd³)

Approx. Approx. Slump Slump

IncreaseIncrease

(inches)(inches)

Strength Strength ReductionReduction

(psi)(psi)

Strength Strength Reduction Reduction

(%)(%)

1 1 200 7%

2 2 400 13%

3 3 600 20%

4 4 800 27%

5 5 1000 33%

6 6 1200 40%

Entraining Air in Concrete

2452

2.54.55.51-1/2

34.561

3.5563/4

45.571/2

4.567.53/8

579Less than 3/8

Mild Exposure

Moderate Exposure

Severe Exposure

Nominal max size of aggregate, in.

Concrete Quality Control

All Field Technicians should be certified

And have a working knowledge of the following ASTM standards:

C31 C1064 C143 C172

C173 C231 C138

ASTM C 172:ASTM C 172: Standard Method for Sampling Freshly Mixed ConcreteStandard Method for Sampling Freshly Mixed Concrete

Sample from middle portion of the batch Sample at two or more regularly spaced

intervals, not to exceed 15 min Combine and remix sample thoroughly Cover Sample to protect from drying

ASTM C 143:ASTM C 143: Standard Test Method for Slump of Standard Test Method for Slump of Portland Cement ConcretePortland Cement Concrete

ASTM C 231: ASTM C 231: Standard Test Method for Air Content of Freshly Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure MethodMixed Concrete by the Pressure Method

ASTM C 173:ASTM C 173: Standard Test method for Air Content of Freshly Standard Test method for Air Content of Freshly Mixed Concrete by the Volumetric MethodMixed Concrete by the Volumetric Method

Basic Techniques for Finishing Flatwork

Strike-off Bull Floating Darbying Floating

Troweling Brooming Jointing Edging

Curing

Finishing

CuringCuring

Performed as soon as possible after final finishing is completed

Performed to prevent the loss of moisture from concrete

Helps in maintaining a favorable concrete temperature for a definite period of time

Will make concrete stronger– More impermeable– More resistant to stress– More resistant to abrasion – More resistant to freezing and thawing conditions

Curing Methods and Materials

Ponding or immersion Spraying or Fogging Wet Coverings Impervious Paper Plastic Sheets* Membrane-Forming Curing Compounds Steam Insulating Blankets or Covers*discoloration can occur if not used properly

Common Concrete Problems

Discoloration Dusting Cracking Plastic shrinkage crackingCrazing ScalingCurlingBlisters DelaminationPop Outs

Discoloration

Prevention of Discoloration

Do not Use Calcium Chloride Type, kind and condition of

formwork can influence color Eliminate “Burning” of concrete Proper curing - Caution with Plastic Uniform sub-grade moisture

Powders under any type of traffic

Easily scratched with a nail or even by sweeping

Very weak wearing surface

What is Dusting?

Finishing operation performed while bleed water is on the surface or before bleeding has finished

Insufficient curing Placement of non-absorptive sub grade or

polyethylene vapor barrier Floating/Troweling after the condensation of

moisture from warm humid air is on cold concrete

What Causes Dusting?

Prevention of Dusting Do not place concrete directly on

polyethylene vapor barriers or non-absorptive sub grades

Proper curing Cold weather concrete practices Vent exhaust to the outside to

provide adequate ventilation

Cracking

The one thing I can guarantee is that your

concrete will crack!

Crazing

How To Prevent Crazing

How To Prevent Scaling

Repairing Scaled Concrete

Clean surface thoroughlyResurface

–Repair mortar

–Portland Cement concrete

What Is Curling?

The distortion of a slab into a curved shape due to temperature gradients throughout the depth of the concrete

Slab Curling

Why Do Slabs Curl?

Other Factors That Cause Curling:

Bleeding / Poor curing / Joint spacing

Shrinkage of the top relative to the bottom of the slab

Moisture gradients in slabTemperature gradients

within the slab

Minimization of Curling Lowest practical slump Largest practical aggregate size Largest practical aggregate content Avoid excessive bleeding Avoid vapor barriers Avoid higher than needed cement

contents Proper Curing Adequate Joint spacing Increase Slab Thickness

Blisters

An irregular hollow bump that appears on the surface during or right after finishing operations

Why Does Concrete Blister?

How Do You Prevent Blisters?

Delay final finish as long as possible Avoid surface drying Initial float done with flat blades

The top 1/8 inch of the surface is densified and separated from the base slab by a thin layer of air or water

Forms during final troweling Most frequent in early spring and late fall

Delaminations

What Are Pop Outs?

A Conical Fragment that breaks out of the surface

Green Concrete Technology

Benefits of Pervious Concrete Environmental Benefits Economic Benefits Structural Benefits

Pervious Concrete Design

Mix Designs of Pervious Concrete

Supplementary cementitious materials (SCMs)

Coarse Aggregates Water Admixtures

Testing and Inspection of Pervious Concrete Density Testing (ASTM C29) No Slump No Air

Self Consolidating Concrete

The use of self-consolidating concrete (SCC) has grown tremendously since its inception in the 1980s.

Because of the material performance in its fresh state, the existing testing methods for conventional concrete are no longer suitable for SCC.

Mix Designs for SCC

SCC mixtures can be designed to provide the required hardened concrete properties for an application, similar to regular concrete.

Benefits of Self Consolidating Concrete Improved constructability  Virtually flawless finish Homogenous and uniform concrete Better reinforcement bonding Flows easily into complex shapes and through

congested reinforcement Superior strength and durability Allows for innovative architectural features

Benefits of SCC

Wall with Normal and SCC Concrete

Testing Procedures for SCC

The Industry Reference

Contributions By:Contributions By:

The Portland Cement Association

The American Concrete Institute

The National Ready-Mix Concrete AssociationBlue Circle CementSt. Lawrence CementConnecticut Concrete Promotion Council

The Portland Cement Association

The American Concrete Institute

The National Ready-Mix Concrete AssociationBlue Circle CementSt. Lawrence CementConnecticut Concrete Promotion Council