CONSTRUCTION MATERIALS
All the materials, which are used in any civil engineering
structures, are to be known as construction material. However, for a geologist more emphasis is to be given on those
construction materials exclusive of steel and timber. Availability of construction material has a vital role or bearing
on the economic implementation of all the major civil engineering
projects. Projects otherwise feasible
have been dropped for want of construction material or alternatively the type
and design of the structure has to be modified to suit locally available
construction materials. In Pong dam at
Beas the slopes had to be modified because suitable size of riprap was not
available. The slope was modified to
suit locally available construction material to be used as riprap. Sand, silt and clay are the most commonly
used construction material due to their easy availability along with gravels.
Geologists
report for a construction material:
A geologist or rather engineering geologist has to determine the following in
order to provide information/input for the project:
(i)
Geographical location
(ii)
Topography of the
area
(iii)
Geology of the
(construction material) deposit
(iv)
Groundwater
conditions
(v)
Quantity available
and
(vi)
Methods of quarrying.
1.
Building materials
(Stones): The building stones should be investigated for their following
properties:
(i)
Durability: It is a
prime requirement, which is the capacity for retaining its original size, shape
and appearance for a long period of time.
Should be resistant to the point of community.
(ii)
Hardness
(iii)
Texture: Final
appearance of desired stone depend upon its texture, mineral composition and
uniformity of color and texture.
(iv)
Jointing – Spacing of
joints etc.
(v)
Porosity – Sound rock
with a little porosity helps in easy quarrying and dressing.
(vi)
Cleavage and bedding
joints
(vii)
Foliations
(viii)
Crushing strengths –
Generally depending upon the load it has to take. While for walls a strength of 3,000 psi has been adequate, for
beams the required strength should be 30,000 psi or above.
(ix)
Cost – Availability
and transportation costs as in case of marbles etc.
(x)
Age – It is generally
established that older the rock – more it is likely to be weathered or prone to
weathering.
POZZOLANIC
MATERIAL
These are very fine-grained natural or artificial material
used in combination with Portland cement.
The word is derived from the town of Pozzkoli (Italy) where volcanic
ashes were used for this purpose. Natural pozzolanic materials are volcanic
tuffs, ashes, siliceous sedimentary rocks (opaline shales, cherts etc.) like
clay and shale. The artificial pozzolanic materials include fly ashes – smoke
residue from chimneys. Pozzolanic
materials also retard the alkali – aggregate reaction and are claimed cheaper
than cement. In Bhakra dam the crushed
Dagshai Shale (crushed) was used as a replacement for cement whereas in Hirakud
dam’ China clay, phyllites and Talabira clay were used.
2.
Road Metal:
For concrete road, pavement and airstrips the material should satisfy the
properties of concrete aggregate in addition to its resistance to abrasion. For
flexible bitumen roadways the material should satisfy the following condition:
(i)
Better cohesion with
tar-ferromagnesian preferred.
(ii)
No friable, elongated
or weathered material.
(iii)
Minimum roundness of
the aggregate.
(iv)
Good abrasion strength
(v)
Good crushing
strength.
(vi)
Low porosity and
(vii)
No coating of
materials
3.
Railway Ballast:
The stones chips used along the railway tracks are called as ballasts. These should have
(i)
High modulus of
elasticity
(ii)
Uniform thermal
expansion
(iii)
Crushing should not
produce fine fragments.
(iv)
Angular grains are
appropriate.
4.
RipRap:
Broken/chipped stones or boulders are used as riprap on the upstream face of
earth dam and embankment used as protective measures against wave action and
erosion by water. The source should be
as near to the structure as possible.
However, in case of Ramganga dam the compressive strength of the
availability Lower Shiwaliks were much less than the required strength. The riprap was brought from a distance and
by screening the terrace deposits.
High Performance Concrete Concrete Laboratory, The
University of Tokyo
Structures Laboratory
Homepage CE 483 DESIGN OF
CONCRETE STRUCTURES
Reclaimed Concrete
Material - User Guideline - Portland Cement Concrete
Emerging
Construction Technologies - Conductive Concrete
Emerging
Construction Technologies - MELLOSE Non-dispersible Underwater Concrete
Admixture