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Recycled Concrete Aggregate

In

ET 494 Senior Design Project

At

Southeastern Louisiana University

By

Alexander Venabel, Benjamin Moore, & Taylor Crumb

April 4, 2018

Table of Contents

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

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

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

Testing Material…………………………………………………………..6

Mix Selection………………………………………………………..……7

Compression Testing.……………………………………...…………… 12

Abrasion Testing..……………………….……………...………………. 17

Slump Testing………………………….………………..……………….19

Air Content Testing…………………………………...…………………20

Concrete Crusher……………………………………………………...…21

Cost Analysis……………………………………...……………………..22

Tentative Schedule………………………………...……………........…..23

Source References………………………………...……………….……..24

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. The Egyptians used a type of

gypsum that acted a cement. This cement that they used is not the same as the cement that we

use to make concrete today. The reason for this is because in our modern society we use a binder

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 (WHD Microanalysis Consultants Ltd,

2005). 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.

Test Sample

Last semester we were able to obtain a test sample of concrete with the help of Bryan

Patterson. 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.

Testing Material

Before we could move forward in actually making the mix we needed to perform some tests on the materials that we are using in the mix. These materials include the large aggregate and sand. To insure that our mix design is correct we had to test our material to determine their actual weight, wet weight, and their dry weight. Knowing this is very important in designing the mix. The chemical reaction between the cement and the water is what gives the concrete its strength. If you do not calculate for how much water your other materials within your mix will absorb, it can reduce the strength of your mix. Below is the results of our tests we performed on our aggregate and sand samples.

Sample Normal Weight (kg)

Suspended in Water Weight (kg)

SSD Weight (kg)

Dry Weight

(kg)

GS Absorption

A 2.113 1.26 2.1165 2.0425 2.38 3.62B 2.116 1.26 2.1325 2.0505 2.35 4.00C 2.1105 1.25 2.1395 2.065 2.32 3.61

GS Absorption Moisture Content

2.35 3.74 1.44%Table 1 Large Aggregate Test Results

Sample Normal Weight (g)

Weight With H20 (g)

Weight Without H20

(g)

SSD of Sand (g)

Dry Weight (g) Weight of Pycnometer with

H20 (g)

D 500 1744.5 982 503 499 1435.00E 500 1747 991.5 502 498.5 1435.00F 500 1746.5 1024 501.5 498 1435.00


2.58 0.80 1.50%2.62 0.702.62 0.70GS Absorption

2.61 0.74Table 2 Sand Test Results

Sample Normal Weight (kg)

Suspended in Water Weight (kg)

SSD Weight (kg)

Dry Weight

(kg)

GS Absorption

A 0.648 0.38 0.6675 0.6275 2.18 6.37B 0.5785 0.34 0.594 0.563 2.22 5.51C 0.4525 0.26 0.4625 0.44 2.17 5.11


2.19 5.66 0.31%Table 3 RCA Test Results

Concrete Mix Selection

With the research that we performed over the last two semesters we were able to create a

concrete mix design. We poured a total of two control mixes. We then used the same mix with a

little modification to incorporate or recycled aggregate to complete total three pours. All the

mixes used the same proportions in order to keep the slump and cement to water ratio. Below

you will see the three different mixes we used and pictures showing the mix process.

Water 7.98 lbs.

Cement 11.6 lbs.

Fly Ash 2.32 lbs.

Course Agg. 50.87 lbs.

Fine Agg. 33.4 lbs.

Add Mixture 15 g.

Slump 1.5 in.

Table 4 Control Mix 1

Water 10.39 lbs.

Cement 15.47 lbs.

Fly Ash 3.09 lbs.

Course Agg. 67.83 lbs.

Fine Agg. 44.53 lbs.

Add Mixture 25 g.

Slump 2 in.

Table 5 Control Mix 2

Water 8.25 lbs.

Cement 12.5 lbs.

Fly Ash 2.5 lbs.

Course Agg. 55 lbs.

Fine Agg. 33.3 lbs.

Add Mixture 20 g.

Slump 1.5 in.

Table 6 RCA Mix

Figure 4 Mixing Set up

Figure 5 Mix Start of the Mix

Figure 6 Completed Mix

Figure 7 Mix Proportioned for Future Tests

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.

Mix 1

(2/26/18)

Cylinder 1 Cylinder 2 Cylinder 3 Average

Compression

3 Day 2577.4 psi 3255.2 psi 3134.9 psi 2989.17 psi

14 Day 5568.4 psi 5879.8 psi 5303.8 psi 5584 psi


Mix 2

(3/12/18)


Compression



RCA

(3/19/18)


Compression


Figure 8 Control Mix

Figure 9 Control Mix

Figure 10 RCA Mix

Figure 11 RCA Mix

Figure 12 RCA Mix

Figure 13 RCA Mix

Abrasion Testing

We will be utilizing 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. We have

constructed the abrasion tool and will be testing it on our samples to determine a wear factor.

Figure 14 shows the design of the our abrasion tool. We will first test it on our two controls and

then on the sample slab we used in our RCA mix. Then we will perform the test on the RCA slab

and compare the results between the three test to determine if the RCA mix has a better

resistance to wear than the control mix.

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.

Figure 14

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”.

Figure 15 Preparing to pull slump mold off. Figure 16 Measuring Slump of Mix

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.

Concrete Crusher

Over the past two semesters we have been searching for a concrete crusher in order to

crush our sample slab. We were unable to get one on campus in time for our deadline. To stay on

our schedule, we decided to crush our sample by hand. We were able to crush our sample to the

desired size with only a 20% waste factor. We then used this crushed RCA in our RCA mix.

Figure 17 RCA in H2O for Testing Purposes

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, aggregate 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 (Spring 2018):

Time Activity Assigned PersonJanuary Create new/recycled concrete

mix designAlex, Ben, Taylor (shifts)

Set up abrasion testing machine

Alex, Ben, Taylor

Find concrete crusher TaylorFebruary Mix and pour concrete Alex, Ben, TaylorMarch Crush test sample of concrete Alex, Ben, Taylor

Mix and pour recycled concrete

Alex, Ben, Taylor

April Test recycled concrete Alex, Ben, TaylorInput data and analyze Ben, TaylorAnalysis of cost Alex

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

WHD Microanalysis Consultants Ltd, (2005). Understanding Cement. Cement History.

Retrieved from https://www.understanding-cement.com/history.html#

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