Concrete Lesson 1: Components of Concrete

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

2. What is this…..

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

7. Concrete Components • Portland Cement • Aggregate • Water

8. 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

9. 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

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

11. 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

12. 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

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

14. 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.

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

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

18. 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.