Saturday, 25 February 2017

Quality control of Ready Mix Concrete plant.


Introduction

As per Indian Standard code of practice (IS 4926) Ready Mixed Concrete (RMC) is defined as the concrete delivered in plastic condition and requiring no further treatment before being placed in position in which it is to set and harden. Instead of being batched and mixed on site, concrete is delivered for placing from central batching plant. First RMC was patented in Germany in 1903, but the transportation system it had not done properly introduced to achieve proper workability of concrete. The first delivery of RMC was made in Baltimore in 1913, and the transit mixer was born in 1926. In 1931 erected a plant at Bedfont, west of London and launched a company named as Ready Mixed Concrete Ltd.

What is need of RMC plant?

The consumer wanted his concrete delivered to the job in a ready-to-place condition. Volume batching is completely replaced by the weight batching and presently computerized weigh batchers are used in most of the batching plants. Aggregates are stored in properly installed bins and cement and flyash are stored in silos. Conveyors are used to transport the aggregates. Cement and flyash is pumped into the central mixer with pneumatic pumps. Electronic moisture meters, digital admixture dispensers are used in fully automatic batching plants. So due to such practices in RMC plant the workable concrete can produce which may be more durable, because of that there is a need of RMC plant.

Chain Survey


Chain survey is the simplest method of surveying. In this survey only measurements are taken
in the field, and the rest work, such as plotting calculation etc. are done in the office. This is
most suitable adapted to small plane areas with very few details. If carefully done, it gives
quite accurate results. The necessary requirements for field work are chain, tape, ranging rod,
arrows and some time cross staff.
Survey Station:
Survey stations are of two kinds
1. Main Stations
2. Subsidiary or tie
Main Stations:
Main stations are the end of the lines, which command the boundaries of the survey, and the
lines joining the main stations re called the main survey line or the chain lines.
Subsidiary or the tie stations:
Subsidiary or the tie stations are the point selected on the main survey lines, where it is
necessary to locate the interior detail such as fences, hedges, building etc.
Tie or subsidiary lines:
A tie line joints two fixed points on the main survey lines. It helps to checking the accuracy of
surveying and to locate the interior details. The position of each tie line should be close to
some features, such as paths, building etc.
Base Lines:
It is main and longest line, which passes approximately through the centre of the field. All the
other measurements to show the details of the work are taken with respect of this line.

Check Line:

A check line also termed as a proof line is a line joining the apex of a triangle to some fixed
points on any two sides of a triangle. A check line is measured to check the accuracy of the
framework. The length of a check line, as measured on the ground should agree with its
length on the plan.

Offset In surveying


These are the lateral measurements from the base line to fix the positions of the different
objects of the work with respect to base line. These are generally set at right angle offsets. It
can also be drawn with the help of a tape. There are two kinds of offsets:
1) Perpendicular offsets, and
2) Oblique offsets.

The measurements are taken at right angle to the survey line called perpendicular or right
angled offsets.
The measurements which are not made at right angles to the survey line are called oblique
offsets or tie line offsets.

Classification of surveying

• Control surveying : To establish horizontal and vertical positions of control points.
• Land surveying : To determine the boundaries and areas of parcels of land, also known as
property survey, boundary survey or cadastral survey.
• Topographic survey : To prepare a plan/ map of a region which includes natural as well as
and man-made features including elevation.
• Engineering survey : To collect requisite data for planning, design and execution of
engineering projects. Three broad steps are
1) Reconnaissance survey : To explore site conditions and availability of infrastructures.
2) Preliminary survey : To collect adequate data to prepare plan / map of area to be used for
planning and design.
3) Location survey : To set out work on the ground for actual construction / execution of the
project.
• Route survey : To plan, design, and laying out of route such as highways, railways, canals,
pipelines, and other linear projects.
• Construction surveys : Surveys which are required for establishment of points, lines,
grades, and for staking out engineering works (after the plans have been prepared and the
structural design has been done).
• Astronomic surveys : To determine the latitude, longitude (of the observation station) and
azimuth (of a line through observation station) from astronomical observation.
• Mine surveys : To carry out surveying specific for opencast and underground mining purposes

Thursday, 9 February 2017

Principles of Surveying

The fundamental principles upon which the surveying is being carried out are

• Working from whole to part.

• After deciding the position of any point, its reference must be kept from at least two permanent objects or stations whose position have already been well defined.

The purpose of working from whole to part is

• to localise the errors and

• to control the accumulation of errors.