and welcome to this series of lectures once again on principles of construction management
and today we begin a new module as for as we are concern in this series on quality control
in construction now since times in memorial quality of construction has attracted a lot
of attention and different people have looked at a differently for example from here hamurabi
who lived thousands of years ago said that if a builder constructed a house but did not
make it strong enough with the result with the house which he built collapsed and so
caused the death of the owner of the house the builder shall be put to death
so this we have seen in the context of safety as well but its equally relevant as for as
quality is concerned so if the construction is of poor quality the person of the company
which does the construction is to be held responsible whether the builder should be
put death or not is a different story but the fact of it remains that yes there is an
issue that there is a certain amount of responsibility that has to be borned by builder now when
it comes to quality as for as construction is concerned it can be related to fitness
for purpose and this is true not only with construction but perhaps with lot of other
things in general fitness for purpose so whether a thing or a process is fit for the purpose
for which it is designed or it suppose to serve
conformance to a specification we have a specification we decide that this is what the specification
the product or the process must meet and whether it meets it or not is a parameter for quality
meeting or exceeding the customer needs customer satisfaction delight or dissatisfaction now
this is a slightly different way of putting the specification because the customer needs
are often quantified in given in terms of this specifications value for money consistency
and lack of variability this is very very important as for as construction is concerned
we cannot get one strength today and another strength tomorrow or ostensibly the same concrete
so if we are getting a certain strength we must keep getting the same strength so basically
what we are saying is if we look at it from a quality control prospective if this is the
normal distribution of the strengths or any parameter that we take this spread that we
have should be as narrow as possible if it is like this where the peak is very well defined
this shows a much better quality control than this one the amount of variation that exist
in the values of the data is represented by the spread one of the very important parameter
as for as quality is concerned is this spread continuing in quality control and management
we often hear terms like quality assurance total quality total quality control tqc total
quality management tqm zero defect statistical quality control stochastic statistics applied
to sampling inspections use of sampling tables for acceptance inspection and so on these
are some of the keywords that come to mind when we come to talk about quality from a
management perspective typically all this is applicable and valid in the case of industries
that is when we are talking about industrial production
now in the case of construction projects there is very little industrial production that
happens a lot of our construction work in fact most of our construction work happens
at site and its very difficult sometimes to apply some of these principles at least the
way they are given in most of the books and texts to construction projects but having
said that we must be aware of these issues so that we can adopt them and move forward
when it comes to total quality management tqm is a way of planning organizing and understanding
each activity that depends on each individual at each levels so quality is something which
is governed by the performance of an individual worker and different individuals are all involved
in construction work at a particular site they all contribute to the quality of the
work being done at that site and thats something which you see in a subsequent slide where
workers are working at different processes in the construction site
so tqm is a way of planning organizing and understanding each activity that depends on
each individual at each level and ideas of continuous learning allied to concepts such
as empowerment and partnership which are facets of tqm also imply that a change in behavior
and culture is required if construction firms are to become learning organizations construction
companies have to learn have to understand that quality control awareness towards quality
is something which workers often need to be educated about its an awareness that has to
be created much as in the case of awareness towards safety quality assurance programs
encompass the following
establishing the procedure for defining developing and establishing quality standards in design
construction and sometimes the operational stages of the structure and or its components
establishing the procedure to be used to monitor test inspect measure and perform current and
review activities to assure compliance with established quality standards with regard
to construction materials methods and personal defining the administrative procedures and
requirements organizational relationships and responsibilities communication and information
patterns and other management activities required to execute document and assure attainment
of the established quality standards if you read this document on your own you will realize
that each term here is a very odd term and has a lot of meaning to it when we say that
establishing the procedure to monitor test inspect measure and perform current and review
activities this is something which is very important monitoring testing inspections measurement
and actually determining the performance all these are integral part of a quality assurance
plan essential element of tqm are management commitment and leadership training team work
statistical methods cost of quality and supplier involvement as for as inspection and quality
assurance quality control in construction projects is concerned in
general inspection involves checking against what is required for any parameter whether
it is strength it could be geometrical tolerance it could be roughness it could be setting
time of cement or whatever clear procedures for measuring and determining the characteristics
of a product or service and only then a comparison with the requirement can be made we must remember
that when we are talking of quality control we are also talking of the possibility of
rejection of certain products and once there is a rejection there could be a huge financial
implication and that is something which has to be avoided and therefore to the extent
possible the procedures to be adopted including the details of all this steps that will be
followed must be outlined as clearly as possible q activities are carried out in order to inspire
confidence of both the customer and the managers that all quality requirements are being met
its very important proper qa activities and procedures in still a lot of confidence in
third parties in inspectors if there are procedures in place then people feel confident that yes
the work is being done according to standards if those procedures are not in place there
is always a little bit of jitteriness a little bit of discomfort in accepting the product
and thats true for construction projects mush as it is true with other products which are
generally meet in the industry in fact the brand value concept is precisely that a product
which has a higher rand value typically has better quality control procedures and this
reminds me of the variability issue that we talked about
if the attention pay towards quality control in the factory made product is high the variability
is likely to be low lets see what some of the important quality gurus or some of the
theories that have been put forward as for as normal quality control is concerned say
about quality here we have demings pdsa cycle for quality which says plan which is prepare
a plan do that has been prepared study that is verified the results of the plan a which
is take corrective action a standardize and feed forward to the next plan so this planning
is not necessarily a onetime exercise it can be repeated in fact it must be repeated depending
on the feedback this feedback is a very important part of a quality control procedure this is
the quality triangle suggested by juran comprising of planning improvement and controlling and
then planning once again
now quality according to juran is fitness to use these are some of the concepts which
have been put forward by people who are well known as for as the
theory of quality assurance quality control is concerned coming to another set of statements
by philip crosby quality as conformance with requirements that the company itself has established
for its products based directly on customer needs it involves do it right the first time
and zero defects there is no way that we can say that since it was the first time it did
not go well as for as construction is concerned as for as production is concerned anywhere
the first product has to be as good as the last product it we cannot say that since that
was the last product we made people had become tired and therefore its not meeting the quality
that cannot happen
therefore the quality has to be sustained right from the word go right till the time
that the production stops now continuing further as for as we are concerned in the construction
industry conquas is a construction quality assessment system which is one of the system
which i would like to introduce to you and its a standard quality assessment system introduced
by the building and construction authority of singapore and has gained popularity in
the world the system objectively measures constructed works against the workmanships
standards and specifications
and the emphasis in this system is doing it right the first time as we just saw once the
project has been evaluated and a score assigned there is no re scoring in conquas that is
rectification and correction made after the assessment is not taken into consideration
then a over the years this system had gained acceptability as a bench marking tool across
several countries including india some indian companies have also got their projects evaluated
under this construction quality evaluation or assessment system
now there is another important aspect of quality control and quality assurance and that is
audit now what is audit it is a systematic and independent examination to determine whether
the quality activities are related results comply with the planned arrangements that
is they meet expected values also whether these arrangements are implemented effectively
and are suitable to achieve objectives and whether understanding of the quality policy
basically means that the people the workers who are involved with the execution of the
quality policy they must understand the provisions thats whats important unless that happens
is very difficult to assure or ensure that quality in a construction project will be
met this is a mandatory requirement laid down
in iso nine thousand it helps in determining system conformity against a quality systems
standard or procedure it also helps to determine the system effectiveness to meet objectives
as well as provide the audity with information to use in improving the system now there are
different types of audit a first party audit is conducted by or on behalf of the organization
itself for internal purposes then obviously there will be a second party audit this has
conducted by the customers of the organization or by other persons on behalf of the customer
so this part is an internal story where the manufacturer or the contractor or the organization
actually carrying out the work carries out that audit which is in inspection on its own
this part which is a second party audit is carried out on behalf of the customer the
customers may hire in independent auditing agency to do this and then there is what is
called a third party audit which is conducted by external independent organization usually
accredited and provides certification or registration of conformity with requirements such as iso
nine thousand one and so on
very often third party audits and third party checks are becoming more and more common as
for as construction projects are concerned so the clients and the contractors they agreed
that while the work is being executed there will be a mutually agreed third party which
will inspect the works regularly submit its reports and these reports will become the
feedback to both of them to improve the quality further as the project progresses now lets
come to the cost of quality the cost could have quality control costs and failure costs
what we have to understand is that this picture is basically coming from the industrial processes
there is a cost involved in the quality control procedures there will be whole quality department
which will have to be given salaries they will have to be given their perks and there
is a cost which is involved so that is the direct cost of quality in terms
of quality control
what happens if we do not have quality control would be failures now those failures could
have an external cost and they could have an internal cost so what we have given here
is the quality costs is equal to the cost of quality control plus the failure costs
and the quality control cost is prevention cost and appraisal cost and the failure cost
itself is internal failure and external failure costs now if you look at it diagrammatically
if we have this as our quality level and we look at the cost on this side we have something
called the failure cost
the failure cost will keep decreasing as the quality level increases and finally we will
have a situation where we have zero defects where as the prevention and appraisal cost
will keep increasing as we move towards this goal of zero defects now it is up to us to
decide what is the level of quality that we will keep what is the level of quality that
is acceptable to us because there is a cost involved now in the discussion so far we have
already talked about construction safety do you see some parallels between construction
safety and construction quality at least i see several things which are quite in common
when we talked of safety we talked of prevention of accidents and we talked of the cost of
safety direct cost in direct cost accident having a direct cost in an in direct cost
then also there was the whole department of safety
there also we have talked about a safety engineer we talked about a safety audit team and so
on those people who were also involved in ensuring that the project site is a safe place
to work that is there are few accidents in fact the target is zero accidents now in order
to ensure that there is a cost that is involved and much like in the case of quality control
there will be quality inspectors there will be quality audits there will be quality reports
there will be a feedback mechanism there have to be records both quality and safety inspectors
are not main line execution people they can be looked upon as people who hindered the
progress so quality control inspector can well say that well product being made or the
construction activity that being carried out does not meet quality standards does not meet
acceptable standards and therefore must be stopped much as the safety inspector can say
that safe practices are not being followed at site and therefore work must stop
but what has to be understood by the top management or the management of the site is that both
of them are an integral part of ensuring a good product at the end of the day they are
part of a team that ensures the reputation of the company and the fact that the finally
the project or the constructed facility meets standards so thats how we can kind of see
the relationship between quality and safety that of course is in a side now let us come
to a specific situations for a construction project in this module we will not be talking
so much about total quality control or total quality control managements zero defects and
so on from a theoretical prospective but therefore it will be to identify certain small topics
taken from the field of construction taken from the site and discussing them from the
point of your safety
so what we are trying to look at from a construction project prospective is quality of materials
components and systems thats one way to look at it the other way of looking at it is to
talk of quality of a product versus quality of a process now as for as the first view
is concerned where we have talking about materials components and systems what are the materials
that we use at site it could be cement steel concrete pre stressing tendents and the list
goes on and on and on so each of these materials must confirm to certain quality standards
and that is what we are talking about when we say that we are talking about quality control
of materials that are contributing to a construction project
moving on there are components of a structure it could be beams slabs columns walls all
of them as components they are made of materials but there is also a lot of other things that
goes into making them the form work the compaction of concrete the welding if it is involved
and so on then there is the system finally it is the system that is the target the bridge
a building a factory a road a sewer line and so on the system is the final product moving
this way if we go in order to ensure that the system performs acceptably its important
that the components performs satisfactorily and its important that the materials perform
satisfactorily so there have to be bench marks for materials components and systems and that
is what is ensured when we talk of quality control and quality assurance in construction
projects
now coming to products versus processes as for as construction industry is concerned
products could be sleepers pipes girders and so on which are largely factory made products
so in this day and age we are talking about pre fabricated members now no matter how much
pre fabrication we do we will be able to make certain products but finally they will have
to be integrated at site to develop a system
we often seen construction being done with pre cast girders now those pre cast girders
are factory made products but they have to be assembled they have to be erected at site
and there is a lot of workmanship that goes on while they are at site in order to ensure
that the bridge made with them meets the requirements coming to processes there are so many processes
there could be welding compaction transportation of concrete and so the list is endless each
of these processes has to meet certain requirements only then will the products meet the requirements
only then the components will meet the requirements and so on so the whole gamut of thought processes
as for as construction industry is concerned from the point of view of quality is a very
complex situation and its important that we understand each and every detail of whatever
small bit we are looking at and that will be the approach that we will adopt as for
as this discussion is concerned in this course
now the third process quality control is closely linked to standardize methods and specifications
test methods lay down a detailed procedure for almost all the steps involved in a test
especially for steps that are considered important from the point of view of results we will
see this when we briefly talk about the parameters which are important from the point of your
testing the strength of concrete today and later on in a subsequent discussion greater
details engineers in the field are sometimes required to interpret the provisions in a
method or create a new test method itself for a unique situation and this adaptation
or modification that an engineer makes cannot be arbitrary and must be based on principles
of known and relevant tests and the required performance of the produce or the process
we will appreciate them port of these statements better when we look at some of the examples
another purpose of these tests could be to ascertain the performance of product or a
process and determine its acceptability or it could be simply to compare two products
or processes issues relating to quality control will be examined using case studies or taking
up examples of simple processes from the field and therefore it will be to carry out exercises
that help in understanding the issues involved and how they are addressed in a quality assurance
quality control frame work
so the discussion in this course is not so much about the provision that exist but what
considerations must prevail or may have prevailed when we introduced to those provisions in
a particular test method or a specification not to recapitulate major quality control
methods involve standardization inspection sampling testing acceptance and remedial measures
in the event that acceptance criteria is not readily met these are things which should
be addressed in our procedures and only then we will be able to talk about a proper quality
control quality assurance program and also have fewer deputes and that something which
we will talk about later we will take up and discuss some specific issues from the construction
industry and look at it from the quality perspective
some of the things that i have identified to take up a case studies is welding works
epoxy coated bars grouts and grouting concrete concrete pipe line using couplers for reinforcement
in reinforcement concrete construction and pre cast products the last three which are
given in brackets we will be taking up later on or possibly i will just upload this material
on the website for you to go through in your own the first four parts is something which
we will talk about
as we move along in this course now we will look at this from the point of view of quality
of materials components and systems that we talked about and the quality of product versus
the quality of a process now can we looked at these seven things in the frame work that
is suggested in the quality of materials components and systems and quality of product and quality
of process framework now if we look at that way as for as the quality of materials components
and systems is concerned these items fall in that category epoxy coated bars is a material
grouts is the material
but grouting is a process concrete is a material and concreting is a process concrete pipeline
is a system using couplers for reinforcement in rc construction is also a material couplers
themselves are basically a kind of material that we use at the construction site looking
at the other side welding is basically a process grouting is a process concreting is a process
using couplers is the process but pre cast products and the kind of considerations that
go in quality control of pre cast products is basically a matter of quality of a product
so this is how we are going to divide our discussion
we are going to focus on bits and pieces of the construction site to better understand
the issues involved in the quality control and quality assurance when it comes to a construction
project site here is the list of factors effecting the compressive strength of concrete as determined
at the compression test there are issues relating to the specimen parameters which could be
dimensions geometry or moisture state there are issues relating to this strength of component
phases which could be the matrix porosity the water cement ratio mineral add mixtures
degree of hydration which in itself is related to curing time temperature in humidity air
content which could be entrapped or entrained it could be aggregate porosity which is completely
different thing it could also be transition zone porosity water cement ratio and the kind
of factors which is listed here and then of course there are loading parameters which
could be stress type rate of stress and application and so on
so what i am trying to say through this slide is that even a simple thing like the compressive
strength of concrete is having so many small bits in pieces or important parameters considerations
factors that go into determining that strength so one one of these parameters changes everything
changes its important to understand and appreciate this from a point of view of quality control
because of the inherent possibility of any of these parameters being taken up for a very
fine scrutiny if it comes to rejection of products we will continue our discussion today
and look at another very simple issue when it comes to concrete construction that is
lapping or splicing of reinforced concrete bars when it comes to rc construction so a
steel bars used in reinforcement in civil structures are generally available in lengths
about twelve meters
however structures of height or span greater than twelve meters need reinforcement bars
to be connected with each other and this connection has to be such that the stresses whether it
is tensile or shear or whatever carried by one bar is transferred to the next so if we
have a situation like this that we have a bar here and we bring a bar here and we put
concrete around it and this bar is pulled out or is subjected to tension there is no
way that the whole joint or the whole member is going to behave the way it is designed
to behave so in order to ensure that we have a mechanism for stress transfer and one of
the ways is to have a lap so this conc whole joint gets buried in concrete and whatever
forces are acting on the steel are transferred from one bar to another through this lap now
this is what is shown in the picture here and this lap is the lap length
so there is a relationship between how much should the lap length be in terms of the diameter
of the bar without getting into the details of that its important to understand that the
moment there is a lap at a given cross section there is more congestion as for as reinforcement
is concerned we are looking at let say four bars but here we could be looking at eight
bars and that makes the concreting process very difficult thats one problem the second
problem is that this lap length is actually something which is being wasted from a material
point of view this is a material which can be avoided if possible one of the things could
be as for as economy is concerned can we get rid of this lap length or can we reduce this
lap length and so on
so there are different ways which have been tried as for as site is concerned now why
we are getting into this discussion here in this course is because of quality control
issues as for as the structure is concerned in order that it performs satisfactorily it
has to be ensured that all these laps are proper basically what it means that they stresses
in this part of the bar are appropriately transferred to this part of the bar so with
that performance criteria in mind lapping is just one of the ways of doing it in order
to ensure a proper stress transfer checking the lap length is just one of the ways
now lets try to see what are the implications of this kind of a splicing consider a typical
plan of a fourteen story building which gives us an effective height of the column let say
a forty meters and if the cross section of the column is shown here it six hundred by
six hundred with ten bars of twenty five diameter we have sixteen columns in this plan and we
find that we have to provide certain lap length for each of these reinforcing bars
so if we look at a simple calculation what we find is length of the bars is obtained
from the market let say twelve meters the lap length is taken as fifty times the diameter
which is one point two five meters which means that the effective length for each bar towards
the height of the column is only twelve meters minus one point two five which gives us ten
point seven five and the number of bars being used is four joints in one bar is three so
these are the three joints that we will have to let say encounter on a minimum now the
total lap length in one bar therefore becomes three point seven five meters in a height
of forty meters we are using three point seven five meters of lap length which is avoidable
perhaps provided the performances not compromised
continuing with this simple calculation the lap length for ten bars in a single column
is thirty seven point five if we take the weight per meter of a twenty five mm bar to
be three point eight five kgs a meter we are wasting or using one forty four point three
eight kgs in a single column and taking the rate of steel to be let say forty four rupees
a kg the amount used is splicing per column is as much s six thousand three hundred and
fifty two now this for sixteen columns go is going to cost us a hundred thousand rupees
now this is the kind of back of the envelope calculation which tells us that there is reason
to study this issue a little bit and try to find out what are the alternatives
now one of the alternatives is the use of couplers instead of using lap splicing as
i shown here we can use mechanical couplers the way that is shown here there is no lapping
and what is done is that there is a bar here there is a bar here and there is a coupler
which holds the two bars together without going in to the details of the mechanical
coupler and how they are fixed and so on which becomes a completely different discussion
from a quality control perspective it is important to ensure that this coupler or this joint
in the reinforcing bar using couplers the way it is shown here in all the bars they
perform in a manner that there is no compromise
on the performance of the structure there is no compromise on the performance of the
steel bars this is another view of couplers being placed at site and we can see that once
we decide to use couplers there will be hundreds of such couplers being used at a construction
site and that takes us to this issue of quality control how do we ensure that the couplers
being used at site are of a certain quality how do we ensure that the bars are being properly
embedded this picture here in fact also tells us what will be the kind of congestion of
the bars if we were not using couplers and we were using the regular splices we must
remember that the diameter of the bars plays a very important role when it comes to deciding
whether or not we should use couplers or try to look into the possibility of alternatives
to splicing in a previous figure we had seen that when doing a splice the bar needs to
be bent the way it is shown here now bending this bar to this extent or in this fashion
is not easy when it comes to large diameter bars for smaller diameter bars yes it is possible
but for large diameter bars its a very difficult proposition and therefore i whole manual exercise
or even a mechanical exercise of bending the bars to this shape adds to the cost of a splicing
which we did not take when we talked about that hundred thousand rupees which is just
an indicative illustrative number the picture also tell gives us a slightly different view
on quality control and that is that this procedure to ensure the couplers are good the coupling
is good this has to be ensured right across all the thousands of bars which are used and
therefore its very very important that the person whose actually engaged in that job
is the person who is conscious of the responsibility on his shoulders to do a good job because
we must remember that as for as reinforcement is concerned it is actually going to get embedded
in concrete and it will be very difficult to do anything after the concrete has been
cast and its equally difficult to ensure that each of these reinforcing bars will be inspected
before the casting is done of course in certain very critical structures it may be ensured
that may be a procedure that will take that into account but most of the time it would
be simply impossible to do that and thats the importance of quality control thats the
importance of educating people to do a good job
now we move forward and try to look at another possibility that is joining bars using gas
pressure welding now what this method does is not use traditional welding in traditional
welding there is a material here and there is a material here we do some kind of edge
preparation here we have an electrode that deposits additional material and we get a
weld as for as gas pressure welding is concerned it does not involve deposition of additional
material what it does is that the two ends of the bars are butted against each other
we make sure that the ends of two bars are flushed and they are brought together so there
is a end here and there is an end here with as little gap as possible here now this is
held in position through a certain amount of pressure the next step is to heat the joint
by an oxy acetylene flame with the pressure applied so what we are doing is we are heating
this zone in the neighborhood of this joint using an oxy acetylene flame and as this temperature
increases to an extent that the metal becomes more deformable this pressure leads to a bulging
here and once a sufficient amount of bulge has been formed and the metal has actually
fused that is these two metals have actually fused and we get a joint like this
we stop the heating and the pressure so this is the technology involved without getting
into the details of the technology the principle here is quality control what are the issues
that go into doing the quality control of gas pressure welding this picture here shows
how the gas pressure welding is carried out you can see this wise here which is there
to hold the bar together one end of the bar and the other end of the bar is here and this
is specially designed flame burner which is heating the joint across for a certain length
and finally what we get is a gas pressure welded joint which would look like this this
is the bulge that we have here and possibly the length of the effected zone the effected
zone means the zone which has been heated to the extent that the metallurgical composition
or the phases in the metal have undergone changes now this is something which you understand
from theory in order to ensure that the quality of the reinforcing bar has not been compromised
we must ensure that the welding has been done properly obviously come to mind one could
be what is the change in diameter whether the change in that diameter is smooth or it
is abrupt so there could be prescriptions or there could be limits like this which could
be that the upper bound on the welded diameter d one should be between one point two d and
one pint five d there should be a smoothness in the welded zone and the length of the rebar
affected should be let say two to three d or whatever it is so this is something which
we can prescribe depending on or based on laboratory tests and the research work on
gas pressure welding when we have these kind of guidelines in place we are better prepared
to ensure quality control on gas pressure welding
so this discussion here whether it is couplers or its gas pressure welding is not so much
to discuss the technology involved there is a whole lot of things that go into it as for
as the technology is concerned the point is to only introduce to you technologies and
talk about them briefly to the extent that you understand what are the issues involved
when it comes to quality control in using those technologies now these pictures here
show site conditions where this gas pressure welding is been carried out and again we see
the importance of a workman the person who is actually carrying out the work it is the
skill which is involved and there are hundreds of bars to be welded
so this is the very very large scale operation carried out in situ and that poses tremendous
challenges as for as quality control is concerned and thats something which we must aware in
mind when we are trying up the right kind of specifications these pictures here show
how the testing is done whether it is let say the tensile test across a gas pressure
welded bar or a bending test of a bar or the testing at site using any of the devices there
are several methods which have been developed to carry out in situ inspection of reinforcing
bars if there been joint using couplers or using gas pressure welding or welding whatever
is permitted and these are the tests which must be carried out in order to ensure that
the reinforcement work the detailing is acceptable
now with this we come to an end of our discussion today where we have talked about the general
issues relating to quality control as for as construction is concerned and here is a
list of some of the references which you may find useful as for as our subject material
today is concerned and from the next class we look at the four or five a specific topics
that we talked about welding grouts and grouting concrete epoxy coated bars and so on and possibly
i will upload some other material for you and i look forward to seeing you in further
discussions
thank you