Guest
Chapter:
1. Explain various aggregates.
Aggregates:
Construction aggregate, or simply aggregate, is a broad category of coarse particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates.
Clay As a Construction Material:
Advantages of clay as Construction Material:
It is easy to excavate clay from ground with little processing required.
It is used in making bricks, walls, floor tiles etc.
It is cheap, durable, and fire resistant, heat insulator, and absorb moisture.
It exhibits plasticity when mixed with water in certain proportions.
Disadvantages of clay as Construction Material:
The weight of the clay brick is relatively large, so the structure needs to bear heavy deadweight, and the cost of the building increases.
Due to low porosity, poor sound insulation.
Sand As a Construction Material:
Advantages of Sand as Construction Material:
Sand is used with cement and with line to make mortar for masonry work and plaster.
It prevents excessive shrinkage of the mortar.
It is a low cost building material.
It is used to provide bulk strength to building materials.
SOME COMMON BUILDING STONES AND THEIR USES:
LIMESTONE:
It is used in the preparation of lime.
It is used in the manufacture of cement.
It is used for plastering purposes.
It is used for finishing work.
MARBLE:
It is used for decorative and flooring purpose.
Crushed marble is often used as a construction aggregate.
Marble has an acid neutralization nature.
SLATE:
It is used for roofing and flooring purposes.
The smooth playing surface of a billiard table is made from quarried slate.
Because it is a good electrical insulator, it is also used for electric switch boards.
It is used for making blackboards in school.
GRANITE:
It is used for flooring pavements, making tiles,bridges piers, columns etc.
It is a hard rock with high compressive strength.
GNEISS:
It is used for pavement in railway and roadway.
It is hard and compact.
Quartzite:
It is used as retaining walls, road metals.
It is used in rubber masonry.
It is hard, brittle and compact.
REQUIREMENTS FOR SELECTING A BORROW AREA:
The area from where construction materials are dug out for use at another location is known as borrow area or borrow pit.
Some points to be considered while selecting borrow areas can be explained as:
Location:
Borrow areas should be located near the construction sites and should be along river channel.
They should be located at the place of stable geological conditions.
They should not be located on the slopes where road alignment, housing areas and valuable farmland may be affected.
Shape and size:
Borrow area should have the large volumes of construction materials. Rectangular shape is generally more preferred.
Drainages:
Borrow areas should not be selected in the drainage line because water may run into the area due to seepage and engineers have to pull out water from the pump.So, it brings difficulty.
Environmental aspects:
Environmental aspects like increasing land values, topography etc should be taken into consideration.
SEARCHING, EXPLORATION AND RESERVE ESTIMATION FOR CONSTRUCTION MATERIALS:
SEARCHING:
Geological search for construction materials for an engineering project is conducted by consulting existing geological map and reconnaissance visit to the project area.
Study of aerial photographs and remote sensing also helps in the identification of potential sites of construction materials within a short time.
EXPLORATION:
Once a site is selected for a construction materials, exploratory works are carried out by pitting and trenching for shallow deposits and by powder drilling for subsoil deposits.
Samples of materials taken from different depths are tested for their quality in the laboratory.
Core drilling is done for rock quarry sites to study the rock condition at different depths.
RESERVE ESTIMATION:
The portion of an identified resource from which a usable mineral or energy commodity can be economically and legally extracted is called a reserve.
The volume of construction materials obtained by excavating through certain depth above water table level is called reserve estimation.
The quantitative estimation of construction material can be done as:
`Q=V*T`
Where,
`Q=`reserve capacity
`V=`Volume of ore
`T=`Specific gravity
Again,
`V=S*t`
Where,
`S=`Cross sectional area
`t=` strike length.
USES OF TOPOGRAPHIC MAP:
A topographic map is a type of map characterized by large-scale detail and quantitative representation of relief, usually using contour lines, but historically using a variety of methods.
GENERAL USES:
Topographic maps can describe vertical information through the use of contour lines (contours).
In telecom, view-shed analyses are performed with the use of topographical maps to determine the suitable locations to place cell-phone towers to provide maximum coverage.
While constructing dams, topography plays an important role in deciding the dam location, the dam catchment as well as the submerged areas.
A topo map can be used to determine the watershed area for a pond or potential pond.
Topo maps can be used to determine % slope allowing us to lay out a road with an acceptable % slope.
USES OF TOPOGRAPHIC MAPS IN SEARCHING OF A CONSTRUCTION MATERIALS:
It depicts the landform where construction materials could be dug out safely and economically.
It depicts the information on previous landscape where construction materials have been buried for a long time.
It depicts the chemical and physical properties of soil. Through this, engineers can have different types of construction materials.
It depicts the change in water course.
It also allows precaution to the engineers giving knowledge about slope instability. If construction materials are dug in unstable slope then expensive equipment and human life will be in danger.
USES OF ENGINEERING GEOLOGICAL MAPS:
The Graphical representation of purpose specific geological information or data obtained from field (after site investigation) which can be quantified (in numbers), with reference to north at certain scale is known as Engineering Geological Map.
GENERAL USES:
These provides the information about the rock mass and soil type available in a particular area which can be used for site selection.
These helps to find the possible and probable reserve and estimate the reserve capacity.
These helps to access the environmental effect.
These helps to analyse and find the slope stability strength of the rock mass, soil, etc.
USES OF ENGINEERING GEOLOGICAL MAPS IN SEARCHING OF A CONSTRUCTION MATERIALS:
Geological maps shows the exposed location and weathering grade of various rock units. Eg-If a quartzite rock is required for construction, then its location can be found from geological map.Then, with topographic map, we make sure that the area does not lie at or very near to the settlement area, road, existing infrastructures etc.
Attitude of rock can be known from the geological map. Using this, the extent of excavation that has to be made to explore the required materials can be found out.
With the help of geological map, the depth of deposit at different points within a particular location of deposit can be known. The average depth of deposit multiplied by the available area gives the reserve capacity.
USES OF AERIAL PHOTOGRAPHS:
GENERAL USES:
This map provide information on:
Shape, size, pattern, shadow and tone.
Both regional and local site features.
Geological information bedding, fold, fault etc.
USES OF AERIAL PHOTOGRAPHS IN SEARCHING OF A CONSTRUCTION MATERIALS:
It provides knowledge about the topography of the site, geology and soil conditions of the site, the weathering grades of rocks and occurrence of the surface and subsurface drainage.
It shows all the remarkable details of the forms and distribution of features of the earth's surface.