Project Presentation

MAKERERE UNIVERSITY COLLEGE OF ENGINEERING, DESIGN, ART & TECHNOLOGY SCHOOL OF ENGINEERING DEPARTMENT OF CIVIL AND ENVIRONMENT ENGINEERING BACHELOR OF SCIENCE IN CIVIL ENGINEERING

MAKERERE UNIVERSITYPERFORMANCE ASSESSMENT OF OTTA SEALS ON LOW TRAFFIC VOLUME ROADS

Main Supervisor: Co-Supervisor:

Assoc. Prof. Umaru Bagampadde Eng. David Kaddu
NAMEREGISTRATION NUMBERSTUDENT NUMBERWAISWA RONALD11/U/452211000384SSEKAMWA DENIS DERRICK11/U/472211000244

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Tuesday, 14 July 2015

Ronald Waiswa & Denis Derrick Ssekamwa (C) July 2015

Performance Assessment of Otta Seals on Low Traffic Volume Roads

Introduction

Background

An Otta Seal has been a more economical and practical alternative to surfacing operations on low traffic volume roads;

However, due to the empirical approach to its design, less information is available regarding its construction and performance;

This information includes mainly the minimum requirements of the natural gravel material (aggregates) and the binder content (asphalt percentage) to be used in its construction;

Performance assessment tests are therefore carried out to come up with the right amount of binder and characteristics of natural gravel in the construction of Otta Seals.


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Ronald Waiswa & Dennis Derrick Ssekamwa July 2015

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Introduction continued

Problem Statement

The construction of Otta Seals involves the use of natural gravel and a relatively soft binder;

Information regarding the requirements of such gravel material and the percentage of binder to be used in its construction is short;

Poor designs and construction procedures of this particular seal have given rise to some of the pavement distresses on low traffic volume roads hence causing deterioration.

Scope

This research involved the collection of four gravel samples from four borrow pits;

It involved the conduction of suitability assessment tests to ascertain that such gravel samples meet the minimum Otta Seal requirements;

It concluded with the conduction of performance assessment tests to obtain the optimum binder content for optimum performance of an Otta Seal.


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Main Objective

To Assess the Performance of Otta Seals on Low Traffic Volume Roads in the Rural and Semi-urban Areas of the Central Region of Uganda.

Specific Objectives

To evaluate the aggregate strengths of natural gravels from parts of the central region in line with Otta Seal requirements as opposed to the use of conventional stone chippings;

To characterize the same gravel samples (suitability assessment) in relation to Otta Seal requirements (characterization will employ the conduction of physical tests i.e. sieve analysis and Atterberg limits);

To determine the performance of natural gravel mixed with bitumen (using marshall mix design tests); and

To compare findings from this study on use of Otta Seals with established practice elsewhere.


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Justification

Otta Seals have proved to be a more economic and practical alternative to traditional bituminous surfacings like the Chip Seal;

Approach to its design is basically empirical, inadequate designs have been often developed during its construction;

Such designs contribute greatly to the emergence of pavement distresses and deterioration.

Therefore Performance assessment tests needed for optimum designs.

Benefits

The research will be of use to the concerned road agencies (District Local Governments in particular) that are majorly responsible for such low volume roads. It will avail them with the information on what criteria to follow in the selection of gravel material and binder content for Otta Seal construction.


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Materials and Methods

Materials

Four natural gravel samples distributed within the Central Region of Uganda were collected.

MC-3000 cutback bitumen was obtained from Mt. Elgon Labour-based Training Centre in Mbale.

Methods

Aggregate strength tests conducted using the 10% FACT value in accordance with BS 812 Part 111:1990.

Gradation of each sample determined using wet sieving method in accordance with BS 1377 Part 2:1990. After oven drying the materials at for 24 hours.

Plastic and Liquid limit tests carried out in accordance with BS 1377 Part 2:1990 on the fines fraction (below 0.425mm) of the unscreened samples.

Performance assessment tests done using marshall mix design tests in accordance with ASTM 1559-89: Standard Test for Resistance to Plastic Flow of Bituminous Mixtures Using Marshall Apparatus.


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Presentation, Analysis and Discussion of Results

Aggregate strength

Gradation


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S/NPlace/SourceWet strength (kN)Dry strength (kN)Wet/Dry strength ratio1Kanyanya3654740.772Kireka2273100.733Kajjansi2864730.614Mutundwe3143820.82
All the samples passed the strength requirement tests with values well above the recommended minimums of for and for

All the gravel samples met the gradation requirement for Otta Seal. This can be observed as the specific gradation curves all fell within the Otta seal gradation envelope.


191613.29.56.74.7521.180.424999999999999997.4999999999999997E-210080523620100191613.29.56.74.7521.180.424999999999999997.4999999999999997E-21001001009880704838251020141052.361.180.60.424999999999999990.30.211999999999999990.156.3E-210081.01472995090016159.98363338788870225.12274959083469712.5204582651391179.81996726677577675.89198036006546655.31914893617021274.50081833060556493.68248772504091632.86415711947626852.209492635024549820141052.361.180.60.424999999999999990.30.211999999999999990.156.3E-210085.28428093645484962.29096989966554828.26086956521739114.0468227424749169.19732441471571787.44147157190635517.0234113712374586.60535117056856176.27090301003344495.85284280936454865.18394648829431420141052.361.180.60.424999999999999990.30.211999999999999990.156.3E-210090.52287581699346262.25490196078431612.5816993464052284.33006535947712392.85947712418300662.53267973856209142.45098039215686292.37867647058823512.30637254901960762.23611111111111072.154411764705882220141052.361.180.60.424999999999999990.30.211999999999999990.156.3E-210090.24390243902439669.5934959349593527.07317073170731811.4634146341463437.07317073170731625.44715447154471554.95934959349593464.55284552845528454.14634146341463433.73983739837398373.3333333333333335

Sieve Size (mm)

Percentage Passing (%)

Presentation, Analysis and Discussion of Results

Plasticity Index

Fines content

Marshall mix design tests


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S/NPlace/SourceLL (%)PL (%)PI (%)1Kanyanya231492Kireka4425193Kajjansi3414204Mutundwe341420
All the samples except the one from Kanyanya showed a bit of plasticity and hence failed to pass this requirement. The PI according to MoWT, was not to exceed 12%; Kanyanya had a PI of 9% hence passing the requirement.
SourceKirekaMutundweKajjansiKanyanyaFines Content (%)5.182.212.153.33
All the samples had their fines content values well below the maximum of 10% as stated by Overby (1999).



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Optimum binder content is calculated as the average of:

Binder content at maximum mix density (3.95% from Figure 2);

Binder content giving a void content halfway between the upper and lower requirements for the mix in consideration ( from Figure 3); and

Binder content at maximum stability ( from Figure 4).

Therefore


33.544.555.562.352.3592.37300000000000022.3632.332.31999999999999982.29

Binder Content (%)

Bulk Density of Mix (g/cm3)

33.544.555.5614.2113.1111.8211.4211.8911.5111.9

Binder Content (%)

Void Content (%)

33.544.555.563.43.843.63.232.8

Binder Content (%)

Stability (kN)

Conclusions and Recommendations

Conclusions

All the samples had dry strengths and wet/dry strength ratios well above the required minimums. Thus all the samples could be selected for Otta Seal construction basing on strength requirements.

For the case of sieve analysis, all the samples had their gradation curves falling well within the Otta Seal gradation envelope. All samples were well graded basing on the Unified Soil Classification system. All the samples qualified for Otta Seal construction basing on this criterion. Further more, all the samples except the one from Kanyanya failed to meet the plasticity index criterion. All the samples passed the fines content requirement. Considering the PI criterion, only Kanyanya material could be used in the marshall mix design mixes.

Performance assessment tests using marshall mix design tests on material from Kanyanya and MC-3000 cutback bitumen gave an optimum binder content of 3.90% for optimum performance of an Otta Seal.


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Conclusions and Recommendations continued

IV. Optimum binder content of 3.90% obtained fell well within the range of 3.28% and 4.10% as evaluated from trial contracts by Overby (1999) in Botswana and MELTC in Mbale district.

Recommendations

More research should be conducted to relate any optimum values obtained with the specific gradations of the gravel material. Gravel material is susceptible to variations due to ambient processes like weathering and decomposition. Optimum binder amounts will somewhat vary depending on such natural properties of the samples.

MC-3000 cutback bitumen is highly flammable and thus risky in using it for Otta Seal construction due to safety harzards. More research is therefore called for to utilize other soft binders say for example the emilsions that are relatively cheaper and safer to apply.


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References

Cook, J. R., Petts, R. C., & Rolt, J. (2013). Low Volume Rural Road Surfacing and Pavements; A Guide to Good Practice. London, United Kingdom: Africa Community Access Programme.

Dr. Gourley, C., Greening, A., Dr. Jones, D., & Petts, R. (2002). Paving the Way for Rural Development & Poverty Reduction. 20th Conference of ASEAN Federation of Engineering Organisations, (pp. 1-2). Phnom Penh, Cambodia.

Giang, T. V., Pett, R., & Duc, N. H. (2007). Rural Road Surfacing Research for Sustainable Access and Poverty Reduction in South East Asia. Journal of the Eastern Asia Society for Transportation Studies, 7, 1944.

Hongve, J. (2006, October). Bituminous Surfacing Options for Low Volume Roads Constructed by Labour-Based Methods.

International Focus Group on Rural Road Engineering. (2002). Otta Seal. Technical Information.

Joshi, S. G., & Jha, A. K. (2013, July 30). Otta Seal Experience in Nepal. TRB 2013 Annual Meeting, pp. 1-2.

Lennox, R., & MacKenzie, M. (2008). Eco-Road Building for Emerging Economies: An Initial Scan for Promising Alternative Technologies. Department for International Development. Gaborone, Botswana: Global Transport Knowledge Partnership.

Mathers, S. J. (1994). The Industrial Mineral Resource Potential of Uganda. British Geological Survey, ODA/BGS Technology Development and Research Programme. Nottingham, United Kingdom: National Environment Research Council.

Ministry of Works and Transport. (2010). Road Design Manual (Vol. 3 Pavement Design; Part I Flexible Pavements). Kampala, Uganda.

Norwegian Public Roads Administartion. (1999). A Guide to the Use of Otta Seals (3000 ed., Vol. Publication No. 93). (C. Overby, Ed.) Oslo, Norway: Allkopi AS.

Overby, C., & Pinard, M. I. (2007, October). The Otta Seal Surfacing. An Economic and Practical Alternative to Traditional Bituminous Surface Treatments.


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Legend

Otta Seal Envelope

Kireka

Mutundwe

Kajjansi

Kanyanya

Series No.

Binder

Content

(%)

Bulk Density

of Mix

(g/cm

3

)

Void

Content

(%)

Voids filled

with Binder

(%)

Corrected

Stability

(kN)

Flow

(mm)

13.02.35014.2133.163.42.3

23.52.35913.1138.653.82.4

34.02.37311.8244.534.02.6

44.52.36311.4248.213.62.8

55.02.33011.8949.493.23.1

65.52.32011.5152.583.03.2

76.02.29011.9053.592.83.3

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