Lightweight Aggregate In Flowable Fill

Published Date: 02 Nov 2017

Use of non-traditional materials as lightweight aggregate in flowable fill

by

Savvas Avramidis

Dissertation directed by: Dr Jean Hall

22 March 2012

MSc Individual Project Report

Table of Contents

INTRODUCTION

The government-funded Aggregate Levy Sustainability Project recognises that "Sustainable development is one of the main issues facing the aggregates industry across the UK" (MIRO, 2011). Defined as granular material used in construction, aggregates are required at high quantities and varying specification, making them the most widely used construction materials in the United Kingdom (Brown et al., 2010). Natural aggregate production accounts for the largest extractive industry in the UK (Bloodworth et al.,2009), contributing approximately £810 million to the English economy (Brown et al., 2010).

Additionally, in UK, municipal waste is generated at a rate of about 540 kilograms per capita per year (http://www.conferenceboard.ca/hcp/details/environment/municipal-waste-generation.aspx). Apart from this, there are industrial, agricultural and mineral wastes. This rate of waste generation tends to increase with increasing population density.

To understand the scale of the problem, the tyre disposal can be taken into consideration. Worldwide generation of waste tyres amounts to 5 million tonnes per year, representing 2% of total annual solid waste (Singh et al., 2009), while the UK produces 487,000 tonnes of used tyres each year that have to be reused or disposed of (Environment Agency, 2010). Since the Landfill Directive has banned the land filling of whole used tyres since 2003 and shredded tyres since 2006 (Defra, 2009), in order to avoid pollution of the environment, there stands an acceptable solution to existing solid waste disposal problems. It is the same solution strategy proposed for the perceived potential to conserve natural resources, reducing energy use in production, cost and time. Recycling!

The reuse of waste materials in the construction industry is a technique of both reducing stockpile and landfill disposal, whilst minimising demand for natural aggregates.

This thesis focuses on the production of a high-quality, lightweight flowable fill for construction, using non-traditional (waste) materials such as crumb rubber, glass cluster and fly ash, as fine aggregate. Crumb rubber is finely ground tire rubber from which the fabric and steel belts have been removed. It has a granular texture and ranges in size from very fine powder to sand-sized particles. This thesis aims, through identification of key material constituents, alongside physical, mechanical and chemical laboratory testing, to define the controlling parameters of crumb rubber and glass cluster waste, in order to identify and recommend further utilisation for recycled aggregates as efficient aggregates on flowable fill fabrication.

AIM & OBJECTIVES

The aim of this research is to demonstrate, through an experimental laboratory investigation, that non-traditional materials as crumb rubber from scrap tires (waste materials) can be used to produce a high-quality, lightweight flowable fill for construction. This study ultimately aims to identify the optimal range for flowable fill mixed with crumb rubber.

The abovementioned aim will be achieved by the following objectives;

Undertake a comprehensive literature review to identify the physical characteristics of strength particle size and shape of rubber, crushed glass and crushed concrete, recognise current uses, establish characteristics, and consider the likely future problems for the industry.

Determine the range of physical, mechanical and chemical properties of these alternative materials in isolation against a control aggregate as an embankment material.

Produce mixes samples, using crumb rubber, crushed glass and crushed concrete as a partial or full replacement constituent of fine aggregate (sand). Use range of water-to-cement ratio and crumb rubber content on fill properties to determine strength characteristics in terms of end-use conformity. Determine the behaviour and interaction of several artificial ‘test’ aggregate samples manufactured.

Define relevant material parameters that control the physical and mechanical behaviour of the recycled waste materials. Perform laboratory experiments, establishing the engineering, strength and stiffness properties of these recycled materials-concrete mixes.

Recommend optimum material constituents for a variety of suitable applications, enabling efficient utilisation of crumb rubber waste as recycled aggregate within the construction industry.

SCOPE

Experimental investigations of recycled materials such as crushed glass (Ohlheiser, 1998), foundry sand (Tikalsky et al., 1998), and limestone screenings (Crouch et al., 1998) have demonstrated successful utilization of these products as aggregate in flowable fill according to ACI (1999).

Scrap tire chips and their granular counterpart, crumb rubber, have been successfully used in a number of civil engineering applications. Tire chips consist of tire pieces that are roughly shredded into 2.5–30 cm (1–12 in.) lengths. Tire chips due to their low material density, high bulk permeability, high thermal insulation, high durability, and high bulk compressibility have been researched extensively as lightweight fill for embankments and retaining walls (Tweedie et al., 1998; Bosscher et al., 1997; Masad et al., 1996; Upton and Machan, 1993; Humphrey and Manion, 1992), but have also been used as drainage layers for roads and in septic tank leach fields (Humphrey, 1999).

Crumb rubber has been successfully used as an alternative aggregate source in both asphalt concrete and portland cement concrete. When mixed with mortar or concrete, research has shown that both compressive strength and unit weight decreases with increasing rubber content (Goulias and Ali, 1998; Fattuhi and Clark, 1996; Fedroff et al., 1996).

The incorporation of fly ash in concrete–rubber mixtures further reduces unit weight (Fattuhi and Clark, 1996). Increasing rubber content also reduces modulus of elasticity (Fedroff et al., 1996) and improves ductility (Goulias and Ali, 1998). In fact, Fattuhi and Clark (1996) suggest that concrete–rubber mixtures could be used for trench filling and pipe bedding, which are common applications for flowable fill. However, research on mixing crumb rubber in flowable fill has not been identified in the literature.

In this laboratory based project, thirteen (13) samples of eleven (11) different mixtures will be produced and analysed. The focus of the experimental program is to investigate the properties such as flowability, volume stability (bleeding), setting time, mass density (or unit weight) and compressive strength of flowable fill in different conditions. The conditions that will be investigated concerns flowable fill when mixed exclusively with crumb rubber or glass cluster or a mix of them as fine aggregate, with or without fluidizing agent F, different w/c and aggregate ratios.

PROPOSED METHODOLOGY

A detailed methodology plan is required in order to accomplish the abovementioned objectives of this thesis. This project mainly involves laboratory work, therefore a schedule of testing need to be made, in addition with a extend research on the materials that will be used and their properties.

Materials

The focus of the experimental program is to investigate the performance of flowable fill when mixed exclusively with crumb rubber as aggregate, mixtures of crumb rubber and glass cullet, and exclusively with glass cullet as aggregate. Sand will not be added to any of the mixtures. This study concentrated on the performance of a single gradation of both crumb rubber and glass cullet supplied by the appropriate manufacturers. The crumb rubber selected for this project was produced from recapping truck tires. Precisely, truck tyre rubber and glass cullet granulates 0.5-2.0mm in size were chosen. In addition, Type I portland cement and Class F fly ash selected to be used in this project. Room-temperature tap water will be used in all mixtures. Sika® ViscoCrete® is a high-performance superplasticiser, a fluidizing agent (F) for cement-sand grouts. Sika® ViscoCrete® will be used in some of the samples in order to produce new samples with higher water reduction, better flowability (reducing bleeding and segregation), as well as to provide rapid adsorption and very low retardation.

Experimental methods

To perform effectively, flowable fill must meet specific criteria regarding physical and mechanical properties such as flowability, volume stability, liquid-to-solid transition (or setting) time, and compressive strength. For given types of cement, fly ash, fine aggregate and water, the properties of flowable fill are largely a function of the distribution of ingredients. This distribution is usually expressed as the water-to-cement ratio, w/c. This ratio is based on the weight of each ingredient. Higher w/c ratio tends to increase flowability but decrease volume stability, setting time, and compressive strength. Thus an optimal range of w/c ratio exists for flowable fill to meet the performance criteria. This study aims to identify the optimal range for flowable fill mixed entirely with crumb rubber or glass cullet or a mix of those.

A series of eleven mixtures will be developed for this study and depicted on Table 1.

Table 1. Flowable fill mixtures incorporating crumb rubber

Mixture

r, g

No

Designation

r (%)

g (%)

r/(r+g)

w/c = a1

1

1.75-23-F

100

0

1

1.75

2

2-22-F

100

0

1

2.00

3

2-22-F

75

25

0.75

2.00

4

2-22-F

50

50

0.5

2.00

5

2-22-F

25

75

0.25

2.00

6

2-22-F

0

100

0

2.00

7

2-22

100

0

1

2.00

8

2.5-21

100

0

1

2.50

9

3-19

100

0

1

3.00

10

3-29

100

0

1

3.00

11

3-38

100

0

1

3.00

Laboratory mixing will be accomplished with a bucket mixer. For each mixture, a minimum of one, 5.1 cm diameter by 10.2 cm (2 in. by 4 in.) cylindrical specimen is required for hardened-state property testing. Re-usable PVC plastic cylinders will be used to collect specimens. All specimens will continuously be moist-cured.

Influence of w/c ratio

The first part of the mixture designation provides the w/c ratio. The w/c ratio of standard flowable fill typically ranges from 3 to 11, although ratios outside this range will be used (i.e. lower than for standard flowable fill)..

Influence of fine aggregate ratio (crumb rubber or/and glass cullet)

The second part identifies the percentage of fine aggregate (crumb rubber or/and glass cullet) by the total weight of ingredients. For example, Mixture 2-22 is proportioned with a w/c ratio of 2 and contains 22% fine aggregate by weight. In addition, all but four mixtures, will contain 100% crumb rubber as fine aggregate. In the rest of them (four), the glass cullet proportion will vary in relation to the crumb rubber, as follows; r/g = 0.75, 0.50, 0.25, 0. Mixtures 3-19, 3-29 and 3-38 were proportioned with a w/c ratio of 3 but different amounts of crumb rubber. Mixtures of 2-22F’ were proportioned with a w/c ratio of 2 but different amounts of glass cullet - crumb rubber ratio.

Influence of fluidizing agent (F)

The letter F in the designation indicates that a small amount of fluidizing agent (0.5% by weight) is added to the mixtures to improve flowability and control bleeding.

Influence of crumb rubber-to-cement ratio

All but two mixtures were proportioned with an equal crumb rubber-to-cement ratio of 1.3 by weight. This ratio is substantially higher than the ratios of 0.1–0.3 used by Fedroff et al. (1996) in concrete–rubber mixtures. High crumb rubber contents will be used in this study to further decrease the mass density of flowable fill. Mixtures 3-29 and 3-38 were proportioned with even higher crumb rubber-to-cement ratios of 1.9 and 2.6, respectively, to investigate the effects of increasing crumb rubber content at the same w/c ratio.

Influence of curing time

For one mixture, preferably the optimum one, three samples will be produced in order to be tested for unconfined compressive strength as measured after 7, 14 and 28 days of controlled curing.

Influence of setting time

Setting time measures the elapsed time from the endof-mixing to initial setting and hardening. The time required to set is measured by probing samples with a pocket penetrometer. While setting times of three to five hours are common for standard flowable fill (ACI, 1999), setting times within 24 h are acceptable for most applications.

Fluid-state properties

The fluid-state properties investigated during this study include flowability, volume stability (bleeding), and setting time. Flowable fill requires a high flowability to be self-leveling. Bleeding is the simultaneous process of solid particle settlement and the upward migration of water, resulting in an accumulation of water at the surface. Flowability and bleeding both depend primarily on the mixture water content, which can be expressed by the w/c ratio.

Hardened-state properties

Often the most important properties of hardened flowable fill are the mass density (or unit weight) and compressive strength. A lightweight flowable fill is particularly attractive when it is necessary to control the total weight of fill placed on the natural soil, in an effort to minimize soil settlement that may compromise fill integrity. Most strength specifications for flowable fill require a minimum strength for acceptable bearing capacity and set a maximum strength to allow future excavation. In this study, strength is determined by unconfined compression per ASTM D 4832-95e1 (2002) at a curing time of 28 days.

Laboratory testing programme

For the purposes of this research thesis, aggregate laboratory testing will follow the requirements specified in British Standards. Table 2 details the laboratory test procedure and specifies the individual test and relevant standards associated.

Table 2. Aggregate lab test procedure, compliant to principal requirements of the British standards.

Test

Compliance Standard

Physical Testing

Constituents of coarse recycled aggregate*

BS EN 933-11:2009

Particle size distribution. Sieve tests

BS 812-103.1:1985

Particle shape: Elongation index

BS 812-105.2:1990

Flakiness index

BS 812-105.1:1989

Particle density and water absorption

BS 812-2:1995

Mechanical Testing

Aggregate impact value

BS 812-112:1990

Aggregate crushing value

BS 812-110:1990

Shear strength tests

BS 1377-7:1990

Compressive strength of concrete cubes

BS 1881-116:1983

Magnesium sulphate soundness

BS 812-121:1989

Chemical Testing

Water soluble sulphates

BS 812-118:1988

Note – order is representative only

*European Standard

RESOURCE REQUIREMENTS

Particular equipment you require and provide a specification and drawings for the workshop for new equipment Laboratory space, consumables and testing equipment required

Access to industry for data collection

Computer software requirements

Design codes required

Crumb rubber, glass clusters and fly ash will be delivered by individual manufacturers. Newcastle University laboratories will provide the cement, water and the fluidising agent F. Furthermore, re-usable PVC plastic cylinders of 5.1 cm diameter by 10.2 cm (2 in. by 4 in.) will be used. Laboratory mixing will be accomplished with a bucket mixer.

SKILLS REQUIREMENTS

Familiarity with the use of the abovementioned laboratory equipment / tests and BS Codes is essential in order to obtain valid outcomes from the analyses. It can be achieved by carefully reading of the BS Codes and with the aid of one-to-one tutoring by an experienced laboratory technician.

PROGRAMME OF WORK

TASK

START

END

Week 22

Week 23

Week 24

Week 25

Week 26

Week 27

Week 28

Week 29

Week 30

Week 31

Week 32

Week 33

Week 34

Week 35

Week 36

Week 37

Week 38

Week 39

Week 40

Week 41

Week 42

Week 43

Week 44

Week 45

Week 46

Week 47

Week 48

Week 49

Week 50

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

Produce project inception report

28/01/13

03/02/13

Conduct a comprehensive literature review

28/11/11

05/05/12

Familiarisation with British Standard testing methods

21/11/11

23/11/11

Initial meeting with Fred Beadle and Stuart Patterson

25/11/11

25/11/11

Source masonry brick sample

28/11/11

28/11/11

Source concrete sample

29/11/11

29/11/11

Material crushing

12/12/11

16/12/11

Manufacture artificial aggregate and blend into mixtures

15/12/11

20/12/11

Initial meeting with Bill Cragie

27/01/12

27/01/12

Concrete Testing programme

Pour and cure concrete cube test samples to BS 1881-125:1985

31/01/12

02/02/12

Determine 7 day compressive strength of concrete samples to BS 1881-116:1983

07/02/12

09/02/12

Determine 14 day compressive strength of concrete samples to BS 1881-116:1983

14/02/12

16/02/12

Determine water soluble sulphate content to BS 812-118:1988

17/02/12

17/02/12

Determine 28 day compressive strength of concrete samples to BS 1881-116:1983

28/02/12

01/03/12

Aggregate testing programme

Determine particle size distribution to BS 812 - 103.1:1985

12/03/12

13/03/12

Determine elongation index to BS 812-105.2:1990

14/03/12

14/03/12

Determine flakiness index to BS 812-105.1:1989

15/03/12

15/03/12

Determine aggregate impact value (AIV) to BS 812-112:1990

16/03/12

16/03/12

Determine particle density and water absorption to BS 812-2:1995

26/03/12

27/03/12

Determine magnesium sulphate soundness to BS 812-121:1989

26/03/12

05/04/12

Determine aggregate crushing value (ACV) to BS 812-110:1990

28/03/12

28/03/12

Determine Ten per cent fines value (TFV) to BS 812-111:1990

29/03/12

29/03/12

Determine constituents to BS EN 933-11:2009

03/03/12

03/03/12

Direct shear testing programme

Produce large shear box samples

04/04/12

04/04/12

Determine shear strength and friction angle to BS 1377-7:1990

11/04/12

13/04/12

Write and compile method statement

16/04/12

20/04/12

Assess and compile results obtained from laboratory testing

27/04/12

29/04/12

Present results using relevant tables graphs and appendices.

27/0412

29/04/12

Write and compile discussion

30/04/12

04/05/12

Write and compile conclusion and recommendations

05/05/12

08/05/12

Write abstract and produce contents, figures and table lists

09/05/12

10/05/12

Finalise report and proof reading

11/05/12

13/05/12

Printing and binding

14/05/12

15/05/12

Block module

Exams

Schedule of works

Holidays

PROJECT RISK ASSESSMENT

No.

Owner

Risk

Level of Risk

Effect on Project

Risk Reduction Actions

If it happens:

Probability (L,M,H)

Impact

(L,M,H)

Triggers

Actions

1

Lack of resource - test equipment not available in project timescale

Low

High

Unable to complete key tasks

Emphasise importance of project within and outside the Uni

Reports of absence

Identify alternative resources in case of unexpected absence. Ensure complete records of work are available at any point

3

Major changes to User Department structure/procedures / is the research idea good?

Low

High

Changes to system, processes

None

Information from senior staff

Plan order of work to delay parts most likely to be affected by structural change. Check before each part of the analysis, if that is likely to change.

4

Volume of change requests following testing extending work

High

High

Delays

Agree specification & priorities. Reasonable consultation.

Swamped with changes.

Managerial decision on importance, technically feasibility and observance of time constraints

6

Poor capture of full User requirements. / Poor data quality / Experiments not working, problems with analysis

High

High

Failure to meet minimum requirements.

Need to rework solution after rollout.

Focus on User Requirements.

Best people with appropriate knowledge

Data clean up

Poor data/Users

/Feedback from User Reps

Only use records which have good quality basic set / System accountability built into project and documentation standards. Monitor through workshops, feedback from

7

Inadequate training – too little too late / , time constraints

High

High

Users unable to use system properly.

Ensure training staff are involved from start of project.

Feedback from training sessions

Review training procedures, enhance.

9

Costs could rise significantly during the course of the project

High

High

University may be unable to financially support the project.

Ensure tight control of costs. Have a ‘pot’ of money available in case risk occurs

Project Budget/Project Manager

Use contingency funds.