CHAPTER I. I. INTRODUCTION The title of this project is CHARACTERISATION OF PAVEMENT
CONSTRUCTION MATERIALS IN RWANDA
In transportation engineering, characterization of pavement construction materials is very
important because it shows the properties and suitability of pavement construction
Soil engineering for highways and stone aggregates for pavement design and construction
are used pavement construction materials.
This work is divided into five chapters and each chapter contains a certain number of
sections. Chapter one, which is introduction, it justifies and gives the objectives of the
work and the methodology used to accomplish this work.
After introduction comes literature review in chapter two reviews the elements of soil
engineering, types of pavements, some fundamentals of pavement design and stone
The next chapter three states the different experiments done on the soil sample as raw
material and other done on the stone aggregates. This chapter shows the data collected
during the experiments and its results.
In chapter four, comes the analysis and discussion of the results obtained in chapter three.
In chapter five, there is a conclusion and recommendation.
I.2. OBJECTIVE OF PROJECT
The project is aimed at determining the suitability of pavement construction materials
from different sources in Rwanda.
I.3. JUSTIFICATION OF THE PROJECT
The pavement construction materials used in road construction must have good properties
such as density plasticity, compressive strength, toughness, hardness.
Contractors are obliged to determine the present properties of the soil sample or
aggregates as raw materials before constructing a road pavement.
After analyzing that the soil or aggregate is poor or weak to be used as a construction
material for road pavement, it is necessary to choose the best soil or aggregates of any
other soil or aggregate having good properties, suitable for road construction.
Visiting websites on internet.
Some laboratory tests are carried out to determine the present properties (suitability) of
soil or aggregates as raw materials.
Those laboratory tests are: Wet sieve analysis, proctor test, atterberg limits(liquid limit
and plastic limit), California bearing ratio(CBR) for soil as raw material and Los
Angeles, specific gravity and water absorption, aggregate impact values and bulk density,
wet sieve analysis for aggregates as raw material.
CHAPTER II. LITERATURE REVIEW ELEMENTS OF SOIL ENGINEERING
II.1 IMPORTANCE OF SOIL ENGINEERING IN ROAD CONSTRUCTION
Soil is the cheapest and the most widely used material in any highway system,
particularly in non-bituminized roads, either in its natural form (say gravel) or in a
processed form (say stabilized soil layer). Also, all road pavement structures eventually
rest on soil foundation. However, soil are highly heterogeneous and anisotrophic in
nature and occur in unlimited varieties, with widely different engineering properties
which, in turn, can be influenced considerably by the presence of water in several
varieties. Considering all these aspects, a thorough study of the engineering properties of
soils is of vital importance in working out an appropriate design of the pavement
structure which will yield an acceptable level of performance of the road over the design
life under the given traffic and climatic conditions. In any road embankment, the bulk of
the material used is soil and if properly designed, should possess stable slopes and should
not settle to any appreciable extent. Also, the embankments require a stable foundation; if
the foundation soil happens to be soft clay, unless property designed, excessive
settlement or even ultimate failure can take place. Similarly when a road is constructed in
a cutting, sound principles of soil engineering are to be employed to ensure that the
slopes are stable under the climatic conditions prevailing in the area. Finally, the
characteristics of the road pavement i.e. the hard crust placed on the soil formation are
not only dependant on the nature of traffic but also on soil properties over which the
pavement rests. Structure like culverts, bridges, retaining walls, overhead traffic signs etc
also rest on soil and their stability depend on soil strength under the given ground water
and climatic conditions. Precautions against the adverse effects of frost action, common
in high altitude areas, can also be taken, adopting sound principles of soil engineering.
(Dr. B.C PUNMIA, ASHOK KUMAR JAIN, ARUN KUMAR JAIN(1973-74) soil
mechanics and foundation 13th edition) and
(Dr. L.R. Kadyali, Dr. N.B. Lal(2003) Principles and practices of Highway Engineering
(including Expressway and airports Engineering)4th edition)
II.2. FORMATION OF SOILS
Soil is defined, for civil engineering purposes, as natural aggregate of mineral grains
that can be separated easily, as for example, by agitation in water. Rock, on the other
hand, is defined as a natural aggregate of mineral grains connected by strong and
permanent cohesive forces and these mineral grains cannot be separated easily as in the
case of soil.
II.2.2 RESIDUAL AND TRANSPORTED SOIL
Soil can broadly be divided on the basis of origin into two groups. In the first group are
the soils obtained as products of physical and chemical weathering of parent rock. If the
products of rock weathering are located at the place of origin, these soils are termed
Residual soils. These residual soils may extend down to hundreds of meters especially
in warm and humid environment where the time of exposure has been long.Moorums,
extensively found in India, Africa and other parts of the world constitute weathered rock,
which may be Lateritic, Granitic etc. And are examples of residual soil. If, however, the
products of rock weathering are transported from the place of origin by transportation
agents which may be water, wind or snow, the soil termed Transported soil. Water
transported soils may be Alluvial, transported by running water; Lacustrine deposited
in lakes and Marine, deposited in sea water. Aeolian soils are transported by wind e.g.
desert dune sands; Colluvial soils are deposited by gravity as in landslides and Glacial
soils are transported by melting snow during glacier movement.
II.2.3. ORGANIC SOILS
Apart from the residual and transported soils are the organic soils which can generally be
distinguished by their characteristic dark colour, strong odour and compressible nature. In
many parts of the world there are huge deposits of organic soils, notable examples being
the peaty swamps of Africa and Muskeg of Canada. Organic soils with very low strength
characteristics make poor construction materials and are not used for road construction
(Dr. B.C PUNMIA, ASHOK KUMAR JAIN, ARUN KUMAR JAIN(1973-74) soil
mechanics and foundation 13th edition).
II.3. PARTICLE SIZE AND SHAPE
A soil is termed Gravel or Sand or Silt or Clay according to its predominant particle size.
To determine the size of soil grains that constitute a soil sample and to determine the total
weight of soil grains in various size ranges, the particle size distribution of soil sample is
to be studied. The simplest method of determining the particle size distribution of a soil
sample is to use a standard set of sieves of different sizes as per IS460. However, sieve
analysis is carried out up to 0.075 mm size only because in sieves of sizes lower than
that, the mesh becomes too small to be effective and sedimentation or hydrometer
analysis has to be resorted to.
In granular (coarse-grained) soils, besides the particle size distribution, the particle shape
also influences the engineering properties. Grains of angular sands and gravels tend to
interlock to provide resistance to deformation.
It is due to the interlocking action that angular particles offer much greater resistance to
deformation under load than rounded particles.
The particle shape can often be inferred from the origin of soil. Wind forms uniformly
graded dune sands with over 75% of their particles falling in the size range between 0.15
and 0.4mm. Gravelly soils formed by flowing water will be rounded as high velocity
water sorts out and abrades the material; lower velocity of water would make it possible
for the material to be deposited as a river terrace material.
While for coarse grained soils, the particle size distribution and particle shape are
related to such engineering properties as permeability, compactibility, and resistance to
deformation under load, it is not so for the fine grained soils (silts and clays).
II.4. SOIL GRADING
Considering the simplicity and expediency, most road agencies carry out the particle size
distribution or soil grading tests as routine tests, using a standard set of sieves.
Conveniently, the results of such sieve analysis are graphically shown as grading curves
plotted on semi-log paper, the particle size or sieve mesh size plotted on horizontal