Aveneu Park, Starling, Australia

Coarse in the flaky aggregates. Consequence of

Coarse
aggregate is a major constituent of concrete as it takes a high fraction of
either the mass or volume of concrete based on any standard mix design. This has
led to work by several researchers on either the mechanical properties of plain
concrete or the bending/shear strengths of beams made from non-traditional
shape aggregates.

The
increased use of the traditional normal aggregates calls for the use of new
shape aggregates. For providing all these utility
structures construction materials such as aggregates and cement are having
important roles and big quantity of concrete is being consumed (Kandekar et al.
2012).

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 Muhit et al. in (2013) worked to determine the
properties of concrete due to different types of aggregates alone. To watch the
influence of coarse aggregates sharply kept other factors such as w/c constant
for each category and of aggregates. Different shapes and casted aggregates
have been combined and used to prepare different groups of concrete with
variable water-cement (w/c).

   Source of these different aggregates, kept
constant to recognize the influence on the characteristics of concrete for
crushing type.

   In the last 1 week and 4 weeks slump values
and compressive strength had been measured without using any admixture or
super-plasticizer to the concrete.

 

   Results of laboratory evaluation have been
presented by Jakarsi in 2013 and evaluated the effects of flaky dimensioned
aggregates on characteristics of concrete. Three categories flaky aggregates
were proportioned in the mixture and had been considered in this research.
Marshall Mix Design has been used for estimating all the mix designs. The
purpose of this research is to learn the influence of flaky aggregates on the
Marshall Properties of bitumen. Flow and stability has been conducted to
conclude the assessment of factors under consideration. It has been revealed
that percentage of bitumen will enlarge with the rise in the flaky aggregates.

 

   Consequence of the different grading
properties of fine aggregate such as sand has been investigated by Agarwal et
al. in 2007 to prepare a better and enhanced concrete mix. Sand has been sorted
in three categories Fine, Medium, and Coarse.

   Various proportions of aggregates have been
varied for preparing the concrete mix of grade M 30. Consequences have been
investigated on the workability of concrete. Other properties such as cube and
flexural strength with permeability had been also investigated. It has been
observed from results that with the variation in fineness of sand, workability
gets altered.

   Combined effect of flaky and elongated
aggregates on strength and workability of concrete has been expressed by
Ponnada in 2014. M 25 grade concrete for different ratios of weights of
elongated to flaky aggregate and angular to total aggregate had been
experienced for different characteristics of prepared concrete. The results
reveal that the influence of elongated aggregates is larger than flaky
aggregates, on the characteristic compressive strength of concrete.

 

   Shape of aggregate used in manufacturing of
concrete has remarkable bearing on compressive strength and permeability of
pervious concrete This has been determined in 2011 by Jain and Chouhan by
conducting laboratory experiments on mixes of pervious concrete prepared using
aggregates of different shape with varying water cement ratio.

  Form of the aggregate
has been measured in terms of angularity number which is a experimental method
projected for comparing the properties of different aggregates. Results
designate that strength and permeability of pervious concrete vary with shape
function along with size of aggregate.

  Chen
et al. (2005) evaluated aggregate characteristics including shape and other
factors influencing the characteristics. Several particle shapes had been
selected for this study. The amendment in rotation angle of aggregates has been
found to associate precisely with the internal resistance. The particle index
value correlated well to aggregate geometric characteristics including
elongation ratio, flatness ratio and shape factor. Flaky or elongated aggregate
have been revealed to have lower compatibility and higher breakage.

                         

 

   Flaky aggregates influence the aggregate gradation
by reducing the concrete particles interlocking characteristic. Gradation has
been modified into five variations of flaky aggregate content by SISWOSOEBROTHO
et al. (2005). The Marshall test had been conducted with varying the asphalt
content such as by incrementing 0.5%. Each variation of flaky aggregate content
resulted on dissimilar optimum asphalt content;

 

   Flakiness
and other shape index had been found to be significant parameters for the
properties and quality of mixes. The incidence of flaky and elongated after
certain limits decreases the compressive strength and causes tremendous
harshness in concrete mixes.

 

   Flakiness index and elongation index are
important physical properties of mineral aggregates which affect the quality of
concrete mixes. The presence of flaky and elongated aggregates beyond certain
limits decreases compressive strength and causes extreme harshness in concrete
mixes. Vyawahare and Modani (2009) performed a study to improve the workability
and strength of concrete with flaky and elongated aggregates using
super-plasticizer with other admixture for determining the allowable percentages
of aggregates in the concrete mixes.

 

  Hamzah et al. (2010)presented the findings
of a laboratory study aimed at investigating the effects on mixtures
incorporating geometrically cubical aggregate to optimize the design. Several
specimens with a high degree of sharpness had been tested to determine
stability and flow. The Marshall Test results revealed the substantial effect
of aggregate shape on mechanical properties.

   In this above study the crushing technology
effectively crushed aggregate to create all the types of aggregates. This study
also checked the properties of geometrically different shaped surface feel of
both types of aggregates.

 

               Adom-Asamoah and Afrifa investigated the resistance of several
reinforced concrete casted beams made of coarse aggregates against the bending
and shear. Specimens have been tested under failure load under of several
tests. It has been observed that the specimens had been suffered premature
shear cracks more than allowable. Deflections compared reasonably well with the
design code requirement but displacement ductility was low.

 

        Singh and Biswas (2013) observed that
flaky aggregates have larger surface area which results in higher demand of
bitumen content in bituminous mix. Flaky aggregates also break during rolling
and decrease the strength of the pavement layer. During the actual execution of
work, the grading and size of the aggregates change from the designed one in
the job mix formula due to practical reasons.

 

       Othman et al. (2010) studied that the
marshal test results of five different coarse cubical aggregate percentages
show the substantial effect of aggregate shapes on mix mechanical properties
.the partial substitution of normal aggregate in hot mix asphalt with
geometrical cubical aggregate was investigated.

 

      Naidu and adiseshu (2013) observed that
strength serviceability of hot mixes such as stability, flow, voids in mineral
aggregate, voids filled with bitumen and air voids highly depend on the
physical properties of aggregate. Dense bituminous macadam mixes had been
analyzed with different proportions (10%,20%,30%,40%,50%) of different shapes
of aggregates studies.

 

      Significance of the shape of aggregate
has been observed by Ryza et al. (2013).In concrete, the shape of
aggregate particles has been related to several properties such as reliability,
slump or shear flow, resistance against shear, tensile and other behaviors. In recent
years, Digital Image techniques have been conducted to find the particle shape
characteristics of aggregate.

       
Kaplan (1958) investigated several types of aggregates to establish the
influence of their shape, texture of surface and permeability or porosity on
workability.  An effort has also been
completed to review these. Also, concluded that variation in the angularity of
aggregates have a better consequence on the workability of concrete.

       
There has been a large disparity in the textures of the aggregates,
little association has been found among this belongings and the workability.
The changes in the ability of the aggregates to soak up water were inadequate
to create significant changes in the compacting factor. No relationship has
been established among tested property and concrete workability. 

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