Presently India has made a principal
plan on increasing the public utility structures such as express highways,
power projects and industrial structures etc, for constructing these
facilities, aggregates with other materials are needed. As usually measured
aggregate generally accounts for almost 70 to 80 percent of cement concrete.
Aggregate is also utilized in base and sub-base courses for both flexible and
rigid pavements. Aggregates can either be natural or manufactured. Natural
aggregates are usually taken out from bigger rock formations through an open
mine. Removed rock is typically reduced to utilizable sizes through mechanical
crushing. Manufactured aggregate is often a bye product of other manufacturing
Flaky particles may be defined as the
particles whose least dimension is less than 0.6 times the mean size dimensions.
Where mean size of aggregates is defined as the mean of two sieve sizes,
between which the particle is retained.
Aggregate are granular material,
derived from the most part from the natural rocks, crushed stones, or natural
gravels and sands. Aggregate generally occupy about 70% to 80% of the volume of
concrete and can therefore be expected to have an important influence on it
the shape of the aggregates, the texture of the coarse aggregate are also
associated. In general texture of round aggregates is smooth textured and of
angular aggregates is rough. Consequently several researchers disagree with
round aggregates due to bonding between aggregates and cement. Moreover, the
angular aggregates are better to rounded aggregates in the two criteria:
Angular aggregates show evidence of a better interlocking achievement in
concrete, which property makes it advanced in concrete used for road and
pavements. The entire surface area of rough angular aggregate is more than
smooth rounded aggregates for the given quantity. Hence, due to greater surface
area, the angular aggregates revealed higher bond strength than rounded aggregates.
The shape of the aggregates turn out to
be more important in case of elevated strength and high performance concrete
where very small water/cement ratio is essential to be used . In such cases
cubical aggregates are vital for better workability.
Surface texture represents the accent of the relative degree to which
particle surface are polished or dull, smooth or rough. This property relies
upon the rigidity, size of particles, internal structure of the stone and the
quantity to which the forces acting on it have smoothened or roughened the
Previous researches and experiments have
revealed that the adhesion between cement paste and the aggregate has been
subjected to several complex factors besides the physical and mechanical properties.
With the increase in smoothness of surface there is a decrease in contact area,
hence a greatly refined and smooth particle will have low bonding in terms of
area in comparison with a rough particle of the same quantity. A smooth
particle, on the other hand, will need a thinner film of paste to lubricate its
movements regarding another aggregate particle. It will consequently allow
denser packing as a result of enhanced workability.
Formerly in the
early stages of cement and concrete improvement, aggregates were considered
inert when considered chemically and detained collectively by cement.
facts confirm that aggregates reveals chemical bond at the edge of aggregate
significantly vital matter in concrete that most of the properties and
workability of concrete are directly altered with the properties of aggregates.
concrete can be relying upon aggregates density, flexible with permeable
aggregate can construct weak concrete with lower resistance to wear.
Almost all the
physical or mechanical properties of concrete rely on the assured properties of
aggregates like origin of aggregates, normal or weighty aggregate, aggregate
measured size, dimension and geometry of aggregates.
Aggregates can be categorized as
natural or artificial depending on their origins. Natural aggregates were
quarried by shaping the crushed stones or from the water sources sides such as
river or ocean. While synthetic aggregates can be acquired from byproducts of
blast furnace like industries.
BSI-812, 1975 which is a British institute
categorized course aggregates in several categories according to their geometry
and dimensions such as rounded, irregular, angular etc.
used for special purposes have been assembled into single class which is
equi-dimensional or cuboidal. Now the flaky and elongated or identical size is
investigated as the ratio of the smaller and longer dimension.
of aggregates shape
It has been proved by previous researches that a relationship
among the voids of aggregates and shape, texture and grading of aggregates
In rounded, cubical and well graded particles reveals lesser
void content than flaky or elongated aggregates. Shapes such as circular or
angular are recognized as significant characteristic.
Roundness can be detected by determining the convexity and
angularity pointed the sharpness of the edges and corners. However, flaky and
elongated particles can generate harsh mixtures and seriously effect in
Surplus poorly shaped particles could reduce the strength of
concrete as it amplifies the water demand. In addition, flat particles can be
oriented in such a way that they could damage the strength and the durability
has been accomplished that the characteristics of concrete were affected by the
quality and quantity of aggregates, the cement paste and the paste-aggregate
behaviors of concrete such as durability and abrasion resistance are also
highly dependent on the aggregate, which consecutively depends on strength of
parent rock, purity, surface texture, gradation and so on.
flaky and elongated aggregate kept stay away from producing eminence concrete.
The existence of flaky and elongated aggregates further than certain limits
raises the deterioration of the concrete mixes. The presences of high
proportion of flaky and elongated aggregates create the low workable and harsh
mixes. An attempt has been made in this investigation to study the feasibility
of use of such aggregate in cement concrete.
The presence of high percentage of flaky
and elongated aggregates makes the mix harsh and difficult to work with. An
attempt has been made in this investigation to study the feasibility of use of
such aggregate in cement concrete.
Proposed objective and outcomes
The purpose of this
study is to learn the behavior of cement concrete produced using normal and
flaky aggregates and to evaluate the workability and load-bearing capacities of
above two types of concretes. Also, the
additional effect of mixing fly ash as fractional replacement of cement over
the effect of flaky aggregate has been studied in this work.
The methodology consisted of monitoring
and comparing the results of the strength and workability testing of cement
concrete casted using usual and flaky aggregates with deviation of fly ash
quantity. The concrete are required to be produced using two types of
aggregates normal and flaky compare the structural performance of the
Results of experiment will present the
effects of aggregate type and mixing of fly ash on workability and compressive
strength and on the structural performance and behavior of concrete.
Methodology adopted in present
Following is the
methodology to be adopted for performing this study
of normal and flaky aggregates
of cement concrete by using normal and flaky aggregates of different mix
proportions and varying the quantity of fly ash
Evaluation of strength
and workability of composed concrete mixes
Comparison of results
for different mixes produced using normal and flaky aggregates
comprises of following chapters
Presents the general background related
to the topic of research and thesis.
(ii)Literature Review This
chapter includes summary of various relevant research conducted and published
in literature worldwide.
Classification, Properties and Tests This
chapter presents the description regarding types of aggregates, their important
properties and testing methods for evaluating these properties.
Experiments and results This chapter summarizes
the results of laboratory experiments and compares the data obtained for flaky
and normal aggregates.
(v)Discussion and Conclusions This
chapter presents discussion and conclusions on the present research.