Recycled Concrete Aggregate

In

ET 493 Senior Design Project

At

Southeastern Louisiana University

By

Alexander Venabel, Benjamin Moore, & Taylor Crumb

September 26, 2017

Table of Contents

Background..……………………………………………………………. 3

Purpose…...……………………………………………………………... 3

Obtaining Test Sample...………………………………………………... 4

Mix Design.....………………………………………………… ………...5

Compression Testing.…………………………………………………… 6

Abrasion Testing..………………………………………………………. 7

Slump Testing…………………………………………………………….8

Air Content Testing………………………………………………………10

Testing Facility…………………………………………………………...11

Cost Analysis……………………………………………………………..11

Tentative Schedule………………………………………………...……..12

Source References………………………………………………………..13

Background

Throughout history concrete has been used to create marvelous structures that can be

recognized as true pieces of art. The concrete that we use and see in our everyday life is

tremendously different from the material that our ancestors used. In 300 BC the Egyptians used a

type of concrete to help construct the ancient pyramids. This form of concrete was constructed

using different materials than we use today. The reason for this is because in our modern society

we use an additive called Portland Cement. The main reasons that the Egyptians did not utilize

this material is because it was not invented until 1824 by Joseph Aspin. Over time concrete has

been improved in many ways. Some of the main reasons is due to testing the concrete for

strength. This strength is mainly measured in compression and tension.

Purpose

For the duration of our project we are looking to find a cost effective method to utilize

more of the existing concrete to create a recycled form of concrete. Since concrete has been mas

produced for over 5,000 years a tremendous amount of waste has been created because it is not

common practice to recycle the material. The main point that we are trying to prove is that the

cost of recycling a preexisting concrete slab is either cheaper or very competitive to the price for

completely new concrete. We will also perform tests to see how the recycled concrete performs

compared to the existing slab. The purpose for this is to test the durability of the recycled

concrete and compare it to the know durability of the existing slab.

Obtaining A Test Sample

The first piece of business for our group is to obtain sample slab of concrete to base our

project on. With the help of Bryan Patterson we have obtained a sample. The sample we received

is from a 40 year old slab that is located west of the student union (See Figures 1, 2 and 3). The

scope of our project is to take this sample section and make recycled concrete out of it. With this

sample we should be able to perform a cost analysis for replacing the remaining slab. We will

compare our results to the characteristics of the newly installed concrete where our sample was

extracted from.

Figure 1 Location of the replaces slab.

Figure 2 Preparation to replace the slab.

Figure 3 Pieces of the removed slab to be used as samples.

Concrete Mix Selection

With the research that we will be performing we will create a mix design that works best

with our recycled aggerate. After performing our tests we will need to create a mix design that

has very close to the same characteristics as the newly installed concrete. We will try and stick to

the know ratios for concrete mixing for our desired strengths, but this may alter if we decided to

use different additives. Once we create our mix, we will use this for the basis for the rest of the

project.

Compression Testing

We will be utilizing the ASTM C 39 standard testing method for testing the compression

strength of our concrete. The way this works is by applying a specified load to a test cylinder

until failure in the test cylinder occurs. After the maximum load it known, you will take it and

divide it by the cross-sectional area of the test cylinder in order to find out how much

compressive strength that the test cylinder will allow.

Procedure:

1) Measure the diameter of the concrete specimen. Take measurements in multiple

locations. If the measurements differ by any amount over 2% then the specimen can

not be used for testing purposes.

2) The Caps or end planes of the specimen should be within .002”, if they are not then

you should cut the excess off until the requirement is obtained.

3) Store testing specimens in a moister controlled room until testing time.

4) Specimens should be tested at: 24 hours, 3 days, 7 days, 28 days, and 90 days.

5) Place the lower bearing block, with its hardened face up, on the table of the testing

machine directly under the upper bearing block. Make sure to clean the face of the

upper and lower bearing block.

6) Zero out the load indicator.

7) Assure that the upper bearing block is in contact with the specimen.

8) Start to apply a constant load to the specimen. This load should be at a rate of 20 to

50 psi per second.

9) Continue applying a consistent load until failure of the specimen occurs.

10) After failure of the specimen record the maximum load that the specimen allowed.

Abrasion TestingWe will be utilizing the ASTM C 779M testing method for testing the abrasion resistance

of our concrete. This testing method uses rotation dressing wheels that apply a specified force to

a rotating concrete specimen.

Procedure:

1) Obtain a specimen that is 12 in by 12 in with a thickness of 4 in.

2) Position the abrasion machine directly over the surface of the specimen.

3) Allow the full weight of each dressing wheel to rest on the surface of the specimen.

At the same time lower the spider as low as possible without exerting any force on to

the dressing wheels.

4) Allow for there to be a minimum of 0.5 in of clearance between the spider and the

dressing wheels. Lock the two in place to prevent any movement.

5) Run the machine for 5 minutes to remove any curing compounds left on the surface.

6) Using a micrometer take a measurement to the nearest 0.001 in on the testing area.

7) Run the machine for 30 minutes. After the test remove any loose material and take

several measurements in the testing are.

8) Repeat this test up to three times. After every third test dressings wheels should be

replaced.

Abrasion Testing Second Option

If we are unable to utilize the ASTM C779M testing method we will revert to the ASTM

C994. This method tests the abrasion factor of concrete by using a rotating-cutter method. We

will use this as a second option because this is an easier method to fabricate on campus.

Procedures:

1) Select a specimen to the nearest 0.1 grams. Fasten this specimen to the abrasion testing

device.

2) Mount the rotating cutter devices. This device should be a rotating shaft consisting of

multiple dressing wheels separated by washers. There should be dressing wheels on both

sides of the rotating shaft. This dressing wheels should have a maximum diameter of 1.5

inches. The drill press should have a minimum speed of 200 revolutions per minute.

3) Start the press and lower the cutter until it comes in contact with the specimen.

4) Apply a normal load of 98 N or a double load of 197 N for two minutes.

5) After the test remove all debris from the specimen and measure its mass to the nearest 0.1

grams.

6) This test should be done at a minimum of 3 cycles per specimen. If the concrete shows a

highly resistant abrasion property you will need to apply a double load instead of the normal

load.

7) Note: you should also measure the effective change in depth after each test.

Slump Testing

We will be utilizing the ASTM C 143 testing method for testing the slump of our

concrete mixture. The purpose of this test is to measure the consistency of freshly made concrete.

Procedure:

1) Take slump cone and assure that it is clean. Make sure to dampen the inside of the

cone.

2) Set the cone top-opening up on a level and damp surface.

3) Stand on the mold tabs of the cone.

4) Add the first layer of fresh concrete filling the cone 1/3 its’ volume.

5) Rod (steel, diameter = 5/8” +/- 1/16”, with rounded 5/8” hemispherical tip) the layer

25 times throughout its depth.

6) Add the second layer of fresh concrete filling the cone 2/3 its’ volume.

7) Rod the layer 25 times penetrating the rod into the first layer by 1”.

8) Add the third layer of fresh concrete filling the cone fully.

9) Rod the layer 25 times penetrating the rod into the second layer by 1”.

10) Using the tamping rod, screed off any excess concrete from the top of the mold.

11) Remove any stray concrete that may have accumulated around the bottom region of

the cone.

12) Step off of the mold tabs while applying constant pressure downward on the cone.

13) Lift the mold upward in 5 +/- 2 seconds being careful to lift straight up.

14) Measure the slump from the top of the mold cone to the center of the sloped concrete

pile (measuring tool should be accurate to ¼”).

15) Record slump measurement to ¼”.

Air Content Test

We will be utilizing the ASTM C 231 testing method for testing the moisture content

within our concrete mix.

Procedures:

1) Place a cleaned dampened measuring bowl on a flat surface.

2) Fill bowl 1/3 with concrete. Rod the bowl with a 5/8 rod 25 times.

3) Tap the side of the bowl 15 times with a 5 pound rubber mallet.

4) Repeat steps 2 and 3 until the bowl is completely filled.

5) Remove excess concrete with a metal strip in a sawing motion.

6) Clean and dampen the rim of the bowl. Attach the cover assembly to the bowl.

7) Insert water into one petcock with a syringe until water begins to exit the other

petcock then close the bleeder valve.

8) Pump the dial to create and initial pressure.

9) Close both of the petcocks and open the main air valve.

10) Hit the sides of the bowl with a rubber mallet.

11) Read the % air displayed by the gauge.

12) Close the main bleeder valve and release the pressure inside the bowl and record the

air content.

Obtaining Testing Faculties.

We have set time within our scope of work to set up our lab on campus. Once we have

fully set up the lab we will determine which test we will be able to do there. The other groups in

the past have worked with the Louisiana Department of Transportation. We will be getting in

touch with them to see if they would still be willing to let us work with them. The other big

concern that we have is finding a concrete crusher that is small enough to crush up our samples

so we can use it to make our recycled concrete. It is our plan to either locate or purchase this

equipment for the duration of our project.

Cost Analysis One of the main purposes for this project it to determine the actual cost for making our

proposed recycled concrete. Over the duration of the semester we will be gathering information

to create an accurate cost analysis. Our cost analysis will cover the entire parking lot that our

sample of concrete came from. We will determine the price per yard to make our concrete onsite.

This means having a concrete crusher, aggerate sorting device, and a concrete mix station on

onsite. We will compare the price that we calculate to the known price to replace the entire

location with the replacement concrete. Our goal is to have a very competitive price.

Timeline (Fall 2017):

Time Activity Assigned PersonSeptember Research Alex, Ben, Taylor

Potential Site Alex, Taylor

October Exploring test and

preparation facilities

Ben

Setting up lab/equipment Alex, Ben, Taylor (shifts)

Order/prepare materials Alex

Design Mix Ben

November Re-check schedule Alex, Ben, Taylor

Pilot testing and trial mixes Alex, Ben, Taylor (shifts)

Analysis of cost Taylor

Start preparing test samples Alex, Ben, Taylor (shifts)

Source References

American Society for Testing and Materials, ASTM C 231, “Standard Test Method for Air

Content of Freshly Mixed Concrete by Pressure Method,” Annual Book of ASTM

Standards , V.04.02, 2010.

American Society for Testing and Materials, ASTM C143, “Standard Test Method for Slump of

Hydraulic-Cement Concrete,” Annual Book of ASTM Standards, V.04.02, 2010.

American Society for Testing and Materials, ASTM C 39, “Standard Test Method for

Compressive Strength of Cylindrical Concrete Specimens,” Annual Book of ASTM

Standards, V.04.02, 2008.

American Society for Testing and Materials, ASTM C779, “Standard Test Method for Abrasion

Resistance of Horizontal Concrete Surfaces,” Annual Book of ASTM Standards,

V.04.02,2008

American Society for Testing and Materials, ASTM C779, “Standard Test Method for Abrasion

Resistance of Concrete or Mortar Surfaces by the Rotating-Cutter Method,” Annual Book

of ASTM Standards, V.04.02,2008