Concrete Lesson 1: Components of Concrete Ag Structures Mr. Dieckhoff

What is this…..

What Is This…..

What is this….

What is This…..

Did you Get the Right Answers: Concrete Truck Concrete Sidewalk Bag of Cement Concrete Block So……what is the difference of cement and concrete?

Concrete Components Portland Cement Aggregate Water

Component 1: Cement Acts as a bonding agent in concrete Makes up 7%-14% of concrete Types: I – common applications II – where heat buildup is a concern III – early strength, when needs strength within 2-3 days IV – low heat, confined indoor spaces V – used on alkaline soils

Component 2: Aggregate Sand, Crushed Stone, Gravel 60%-70% of concrete Categories: Fine: <1/4” – sand Course: >1/4” – gravel The larger the aggregate size – the stronger the concrete

Component 3: Water pH of 6-8 works best Increase of water, decreases the cement bonding

Water-Cement Rati0 1 gallon of water = 8.33 lbs 1 bag of cement = 94 lbs PSI = Pounds per square inch 4.5 gal mixture x 8.33 lbs = 37.48 lbs water / 94 lbs cement = .398 (5700 psi) 5.5 gal mixture x 8.33 lbs = 45.81 lbs water / 94 lbs cement = .487 (4500 psi) Too much water = aggregate segregation

Mixing Concrete Hydration – chemical reaction between cement and water Ways: # bags of cement in cubic yard of concrete Foundation walls – 5 bags of cement/yard Floors, Driveways, Sidewalks – 6 bags of cement/yard Severe Conditions – 7 bags of cement/yard Show relative amount of each component 1:2:3-6 ratio means – 1 part cement, 2 parts sand, 3 parts gravel, 6 parts water Gallons of water mixed with each sack 5.0 means 5 gallons of water with each sack

Admixtures – substances added to concrete to modify it’s properties

Mixing Concrete Lab In groups of 3, research how much of the following ingredients you want to mix to have the strongest concrete. Create a form using 2x4 and a sheet of plywood for the bottom. 2 – 2x4 cut 4” long and 2 – 22” long. Wearing gloves, mix up your concrete mixture in the pan provided. Place mixture in the form for at least 3 days. Test your concrete beam using the diagram: Write up a Lab Report: What was your mixture (measurements & percentages) How much weight did your mixture support? What would you do different if you did this over? Other than the mixture, what other factors affected the strength of your concrete.

Slump test Determines if the concrete is of the proper consistency Indicates if more or less water is needed

Review Components of Concrete Types of Cement Categories of Aggregate Water-Cement Ratio Hydration Mixing Concrete Slump Test

True / False Quiz (14 Points) Concrete is comprised of only two primary components, (cement and water), in varying proportions. The percentages of cement, aggregate, and water used in any concrete mix vary according to the characteristics required for a particular application and concrete material conditions. Water makes up the largest volume (60% to 75%) of material used in concrete. The amount of aggregate in the concrete mixture is the primary factor in determining concrete quality and strength. In order for hydration to occur, the water used for concrete must have a pH of 6 to 8. During hydration, the water in the concrete mixture evaporates. Bleedwater is excess water that collects on the surface of concrete as aggregate material sinks in the concrete mixture.