infill compaction research project - brock usa

Infill Compaction Research Project

A brief report presenting the investigation, results and analysis from testing infills with an existing compaction apparatus.

Date: 28th January 2020

Sports Labs Ltd 1 Adam Square,

Brucefield Industrial Park, Livingston EH54 9DE

Sports Labs Ltd: 1 Adam Square, Brucefield Industrial Park, Livingston, EH54 9DE

www.sportslabs.co.uk

1. Executive Summary

15 different infills were tested in a compaction apparatus to simulate repeated footfall over several years of

usage to determine compaction characteristics. Reduction in infill depth and post-test condition was

recorded and analysed. After testing, all infill samples were fully compacted with the least compaction

occurring in the Brockfill sample and the most in the organic sample. Overall, natural infills, with the

exception of Brockfill, were altered more meaning the infill samples did not return to their pre-test condition.

2. Introduction

Increasingly over the last few years the topic of infill migration has become a significant concern. When

sports pitches are used infill levels decrease over time but there currently is limited understanding in regards

to the main mechanisms that result in loss or migration. Infill can be lost through maintenance work, through

general play if splash is generated from the ball bouncing or players sliding or taken off the pitch in players

boots and socks. There is also the possibility that through usage, infill is compacted to varying degrees that

could impact how easy it is for infill to be moved.

With the use of our specialist testing equipment, infill compaction and possible subsequent degradation was

investigated.

3. Materials and Methods

Each infill sample was measured and placed in the compaction apparatus and tested. To try and replicate

average forces and pressures found during ground contact when running, the compaction apparatus was set

to generate 1200N of force. Post testing, depth of the infill sample was measured a second time to allow for

a direct comparison to the starting depth. Surface pictures were also taken and notes of the condition of the

sample were made.

3.1. Test Equipment

The compaction apparatus is composed of a control panel, two pneumatic air cylinders (2in bore, 3in stroke),

and two test cylinders (Figure 1).

Figure 1: Overall view of the compaction apparatus.



3.2. Materials

• Compaction apparatus

• Type of Infills

o SBR

o EPDM

o TPE

o Natural

• Camera

3.3. Methods

1. Measure out specified uncompacted depth of infill.

2. Put the infill into the compaction apparatus test cylinder and take a picture of the top surface of the

infill. Record the infill depth. Place the filled cylinder in the slot under the piston. Ensure the cylinder

is placed in the right slot (unheated).

3. Ensure the compaction apparatus is unplugged. Open the control panel and adjust the pressure

setting to 85 psi.

4. Plug in the apparatus and turn on.

5. Set the number of cycles and cycle time as specified in the testing schedule.

6. Press the “Start” button.

7. Once the test has stopped, remove the cylinder and measure the post-test infill depth. make note of

any significant changes to the infill and take a picture of the top surface of the infill.

4. Test Schedule

For each infill to be tested, the following set of tests will be conducted:

• 20mm depth, 2 sec cycle time, 8 hrs

• 20mm depth, 1 sec cycle time, 8 hrs

This schedule is subject to change over the course of testing depending on initial investigative results.



5. Results

Table 1: Table of average infill depths pre and post-testing.

Infill

Day

Book

No.

Stroke

Time

(sec)

Test

Time

(hrs)

Pre-

Test

Depth

(mm)

Post-

Test

Depth

(mm)

Comments

SBR

Stock 2476

2 8.0 20 15 Fully compacted, required manually

breaking up, still larger chunks after 1 8.0 20 14

SBR

Rubber Mix 5509

2 8.0 20 15 Bottom 2/3 fully compacted, top layer lose

when shaking, fully broken up after 1 8.0 20 15

EPDM 4224 2 8.0 20 16 Bottom 2/3 fully compacted, top layer lose

when shaking, fully broken up after 1 8.0 20 17

EPDM

Grey 4707

2 8.0 20 15 Fully compacted, broke back up with a lot

of shaking 1 8.0 20 15

EPDM

Green 5534

2 8.0 20 16 Fully compacted, required manually break

up, fully broken up after 1 8.0 20 17

TPE 1 4814 2 8.0 20 16 Bottom 3/4 fully compacted, top lose when

shaking, still chunks after removing 1 8.0 20 15

TPE

Holo 2834

2 8.0 20 15 Fully compacted, required manually

breaking up, still larger chunks after 1 8.0 20 15

TPE 2 8884 2 8.0 20 14 Fully compacted, required manually

breaking up, fully broken up after 1 8.0 20 13

Natural

Brockfill 5472

2 8.0 20 17 Fully compacted, easily broke back up with

shaking 1 8.0 20 17

Natural

Organic fill 5705


up, some chunks after 1 8.0 20 7

Natural

Cork 1 4958



Natural

Cork 2 4957



Natural

Organic fill NA

2 8.0 20 6 Fully compacted, loss of water through

compaction 1 8.0 20 5

Other 1 4760 2 8.0 20 17 Not fully compacted, some chunks near the

bottom, freely moving pieces post test 1 8.0 20 18

Other 2 4122 2 8.0 20 16 Fully compacted, required manually break

up, some chunks after 1 8.0 20 16



Table 2: Table of average reduction in infill depth post-testing.

Infill Type Average Reduction in Infill Depth (%)

SBR 26%

EPDM 20%

TPE 27%

Natural (Brockfill) 15%

Natural (cork) 36%

Natural (others) 67%



Figure 2: Images of infills post-test. Left to right, top to bottom (5509, 4224, 4707, 5534, 4814, 2834, 8884, 5472, 5705, 4958, 4957,

4122).



6. Discussion

When looking at the change in infill depth for all samples, the testing equipment effectively compacted all

types of infill, by varying degrees. By running testing for 8 hours with 2 second cycles, the infill was subjected

to similar wear conditions as experienced during standard Lisport testing thus the results found should be

representative of wear conditions found over a number of years of usage.

When comparing the results from the different types of infill, the SBR and EPDM were found to be very

similar. Over the 8 hours of testing, compaction resulted in a 26.25% and 20.00% reduction in depth

respectively. Most samples were full compacted, thus when shaking the test cylinder minimal loose infill

moved. To remove the infill, the samples had to be dug out; however, once removed the infill fully broke up

and settled back to its original state. When checking the uncompacted samples post-testing, there was no

noticeable degradation either type of infill.

The compaction of the TPE samples was fairly similar to the SBR and EPDM samples in regard to the reduction

in depth (26.67%) however the physical state of the infill post-test was different. The majority of the TPE

samples were fully compacted and needed to be manually broken up to remove the infill from the test

cylinder. Once removed, some of the infill was still in chunks thus it did not return to its pre-test state.

Additionally, the shape of some of the infill was permanently altered. Specifically, some of the Holo TPE

(2834) was compressed and flattened as can be seen in Figure 2.

On average, the natural infills compacted more than the SBR, EPDM, and TPE samples with the exception of

Brockfill. The depth of Brockfill reduced by 15%, the cork samples reduced by 36%, and the other natural

samples reduced by 67%. All samples were full compacted and while the cork and other natural samples

needed to be broken up manually the Brockfill was easily broken up by shaking the test cylinder. Minimal

degradation was noted in all samples other than the organic fill which was permanently altered. During the

test, the moisture in the sample was forced out due to the applied pressure and the post-test sample

remained fully compacted after being removed from the test cylinder.

The results of all samples tested could provide some insight into the behaviour of infill in pitches over the

life cycle of the surface. The fact that all samples were fully compacted post-test and there was a reduction

in infill depth demonstrates that over years of usage infill is compacted, resulting in a loss of infill depth and

subsequently the need for infill top-ups with the addition more material required to maintain surface

performance. With the SBR, EPDM, TPE, and most of the natural infills, due to the need for a more aggressive

method of removal from the test cylinder, it could be more difficult to de-compact the surface to break up

the infill as part of the maintenance procedure. Conversely, because the Brockfill was easy to de-compact,

if surfaces using this infill were well maintained to ensure high compaction did not occur, infill top-ups may

be needed less frequently.

End of Report

infill compaction research project - brock usa

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