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What are various Types of Cement?

Cement is a construction material which is used as a binder. It binds other construction material aggregate and sand together. Cement exhibits different properties if we change the chemical composition.  Earlier the different types of cement was found by only varying the relative proportion of the oxide composition.As time advances, new materials like additives to the clinker at the time of grinding, use of new raw materials resulted in production of new variety of cement.The various types of cements as per Indian Standards are-

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Bar Bending Schedule

Introduction

Bar bending schedule is a means to calculate the exact quantity of reinforcements required in a structure. It is helpful for any concrete work to know exact amount of cement, aggregate or sand required for a structure. It is referred to as BBS in short form. It involves calculating development length, diameter of bars to be used, stirrups, cutting length, crank length, and many more. It is a process of cutting and bending reinforcement bars into desired shape and size as per structural drawing. These drawings are handed by structural engineers for various structural elements like footing, column, beam, slab, etc. and then handed over to contractors for the execution of the work at site by the labors. The contractor must understand in depth before portraying it to the labors. BBS is necessary to the contractor as it is important in bidding for tenders. All these works play an important role without which work can’t proceed.
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Geotechnical Investigation of a Construction Site

Geotechnical Investigation of a Construction Site
A civil engineer needs to understand the soil behavior of the construction site and to find the satisfactory solution to the soil problem. The knowledge of subsoil conditions at a site is a prerequisite for safe and economical design of sub-structural elements. A well planned and properly executed site investigation programme will provide information about the stratigraphy and physical properties of the soil at the site including ground water table and its fluctuations. The process of investigation are as follows:

Sub-surface Investigation:
Preliminary Exploration which is study of geology of the site and the reconnaissance.Detailed investigation follows the preliminary investigation and from this we come to know about the nature, sequence and thickness of soil layers and lateral variations, sequence and position of ground water table.

Borehole:
As a part of geotechnical investigation,we need to construct boreholes.There are different methods used for boring.e.g. Auger Boring,Wash Boring,Percussion Boring, Rotary Boring etc. The suitability of any particular method of boring depends mainly on the nature of soil,the position of water table,the ease and accuracy with which changes in soil and ground water conditions can be determined.

Soil Sample:
Generally it can be classified as
(i) Disturbed Sample: Disturbed Sample are those where natural soil structure gets modified or disturbed during sampling procedure.
(ii) Undisturbed sample: Here original soil structure is preserved and also soil properties have not undergone any alteration or modification.

For all practical purpose, undisturbed soil sample is suitable for all laboratory tests including shear strength and consolidation tests.

Types of soil samples Required for Laboratory Tests

Type of Test Type of sample required
Natural water content Undisturbed
Density Undisturbed /Representative
Specific Gravity Undisturbed / Representative
Grain size distribution Undisturbed
Atterberg’s Limit Undisturbed
Coefficient of permeability Undisturbed
Consolidation parameters Undisturbed
Shear strength parameters Undisturbed

Field Tests:
The field tests commonly used in sub-surface investigation are:

(i) Vane Shear Test
(ii) Plate Load Tests
(iii) Standard Penetration Test(SPT)
(iv) Cone Penetration Test
(v) Pressure Meter Test
(vi) Geophysical Methods

Number and Deposition of Trial Pits and Borings
The purpose of soil exploration is to provide the designer with complete information about the subsoil layers at the site. The number and spacing of boreholes or trial pits depend upon extent of site, uniformity of strata, nature of structure and loading diagram.

As per IS:1892-1979 recommendations,for a compact building site covering an area of about 0.4 hectare,one bore hole or trial pit in the center and one at each corner will be sufficient.For larger areas,it may be useful to perform sounding test /cone penetration tests at a spacing of 50m to 100 m by dividing the area in a grid pattern.

Borehole Logs:
After the soil investigation has been completed and the results of laboratory tests become available, the ground conditions discovered in each boreholes are summarized in the form of a chart called borehole log. A borehole log contains following data-

(i) The soil profile with elevations of different strata
(ii) Ground water table
(iii) Termination level of borehole
(iv) The depth or range of depth at which samples are taken
(v) Depths at which in-situ tests were performed
(vi) Type of soil sample
(vii) Results of important laboratory tests
(viii) N-values at the measured elevations

A sample of borehole log is shown below
Sample Borehole log
Sample Borehole log

Fig 1 : BORE HOLE CHART

Site Investigation Report:
A site investigation report is the conclusion of the investigation, exploration and testing programme. The report is addressed to the client. Although individual reports may be given in the form of content and presentation, a typical report contains:

(i) Introduction
(ii) Borehole logs
(iii) Field and laboratory tests results
(iv) Analysis of data
(v) Recommendation
(vi) Reference

Explain briefly various types of Estimates

Before undertaking a construction project it is necessary to know the expected cost and it is worked out by estimation. It is a computation of the quantities required and expenditure likely to be in the construction of the work.

The following are the different types of estimates:

1. Preliminary or Approximate Estimate:
This estimate is prepared to decide the financial aspects,policy and to give the idea of the cost of the proposal to the competent sanctioning authority.The calculation for approximate estimate is done in many ways. There are three types of approximate estimate
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BILL OF QUANTITIES (BOQ)

INTRODUCTION
It consists of various items of work in the form of a statement depicting quantities, description and rate per unit. It is used to define the quality and quantity of works to be carried out by main contractor for completing work. It is made in tabular format and is mainly used for inviting tender and supplied to contractors to fill up the rates. On receipt of tenders the rates are compared and decision is made regarding the work. It is prepared by quantity surveyors and building estimators to be handed over to contractor.

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