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Selection
and use of concrete overlays
Michael
E. Ayers and Dale Harrington
Interest
in concrete overlays as a cost effective pavement
restoration technique has grown significantly in the
past decade. Innovations in design, materials and
placement techniques, as well as greater focus on
economic and environmental impact, has resulted in
a wider variety of concrete overlay options.
An
illustrative life-cycle cost analysis of concrete
roads in Mumbai
S. Govindarajan
Roads
are the arteries of any city. Unless they are in healthy
condition, the city cannot function properly. If the
road network is not good, it will lead to traffic
snarls, rise in motorists' tempers and waste of national
wealth. Therefore any city to have a healthy living
should have a good network of roads. The roads should
not be often dug up and left with only potholes. This
paper highlights benefits of cement concrete roads
and presents a life-cycle cost analysis based on experience
of working in Mumbai city.
Long
life concrete pavement practices
Shiraz Tayabji
Concrete
pavements are widely used in the United States for
a range of applications, from lightly loaded streets
and parking lots to heavily trafficked highway and
airport pavements. Over 50% of the US interstate highway
system was originally constructed using concrete pavements
and concrete pavements continue to be the choice for
heavy truck traffic highways and high volume urban
highways. Concrete pavements are typically referred
to as the safer, smoother, and longer-lasting pavements.
And now, with the emphasis on sustainable construction
practices, concrete pavements are playing an even
critical role meeting the infrastructure needs in
the United States. The emphasis on sustainable construction
is of recent origin. However, as resources diminish
globally and the environment comes under increasing
stress, the adoption of sustainable design and construction
practices is a necessary strategy to ensure that we
meet our current needs responsibly. In the US, sustainability
related considerations are being introduced at the
design and engineering phase, in material selection,
during construction, while in service, and ultimately
at the end of the pavement's life.
Concrete
roads in Mumbai
Shridhar V.
Joshi, Avinash Rao and Vishal R. Thombare
The
Municipal Corporation of Greater Mumbai (MCGM) is
responsible for road network of about 1941 km in the
city of Mumbai including roads in the Eastern and
Western Suburbs. However, this data excludes the two
Express highways namely Eastern and Western expressways
passing through the city. These expressways are maintained
by the local Public Works Department (PWD). While
majority of the roads in the city are bituminous,
Mumbai leads other cities in the country with large
percentage of road constructed in concrete. Concrete
roads or rigid pavements constituted only about 5%
of the total road lengths in Mumbai in 1989. Today
more than 24 % of the city's roads are concrete roads.
Mr. S.V. Joshi, Former Chief Engineer (Roads, Bridges
and Traffic), MCGM and his colleagures present the
case study of Mumbai's concrete road projects.
Use
of industrial byproducts and recycled materials in
concrete structures - An engineer's perspective
Satish Desai
During
the period after 1945, cements have become progressively
more reactive and it has become possible to develop
higher compressive strengths and to reach the required
strength with lower cement content. Mix design techniques
have been developed to produce concrete with compact
microstructure, e.g. grading and aggregate packing.
It has also been recognised that there is a limit
on the availability of natural aggregate and minerals
used for making cement, and it is necessary to reduce
energy consumption and emission of carbon dioxide
resulting from construction processes. Solutions to
this problem are sought through usage of recycled
concrete aggregates and industrial by-products as
partial replacement of Portland Cement. However, it
is important for an engineer to ensure that use of
any construction materials does not adversely influence
safety, quality and durability of concrete structures.
This paper examines the merits of using such alternative
materials and various issues related to the influence
of these materials on performance of concrete.
A
case study of shrinkage and other cracks in pavement
quality concrete
A.K. Pandey
Concrete
pavements have a larger maintenance free life if properly
designed and constructed. With the experience of constructing
approximately 1500 km of two or 3 lane new concrete
roads for the Golden Quadrilateral (GQ) Projects of
National Highway Development Programme (NHDP), Indian
contractors have achieved an average laying speed
of 300 meters (2 lane road with 9 meter widths and
0.3 meter depth involving approximately 810 cum of
concrete) in a day. Extensive use of modern machinery
such as pavers and batching plants for the first time
in India made this possible. As pavements have a much
larger surface area compared to other structural members
such as beams and columns, they are prone to shrinkage
induced cracking. Therefore, during their initial
stages of construction, suitable measures are taken
to protect them against damages from premature surface
drying, which may lead to large plastic shrinkage
cracks and from thermal stress development due to
temperature differentials across the section. However,
despite taking standard quality control measures,
cracks may develop and potholes may appear after opening
the road to traffic. This paper presents a case study
of shrinkage and other cracks prevention measures
in concrete pavements and describes repairs undertaken
in two major construction projects in which the author
was associated.
Experiences
of constructing concrete roads in Surat
Rohit J. Madhwani
The
city of Surat is known for its textile trade, diamond
cutting and polishing industries. It is located on
western part of India in South Gujarat and lies at
a bend of the River Tapi, where its course swerves
suddenly from the northeast to southwest.
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