| Topic : How to prevent mishaps at Construction Sites? |
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Construction Planning & Management
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Activity:
514 views;
last activity : 03 05 2011 11:36:32 +0000
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CHECKLIST - Conformance to Specifications...!!!
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Compressive strength test
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A comprehensive QA/QC strategy
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Slump test
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BASIC TESTS ARE TO BE FOLLOWED
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Precast Prestressed Concrete.
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TEAM OF INDEPENDANT/COMPETENT/HONEST PERSONS
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Compressive strength of a sample may not ensure quality of lot if not properly compacted.
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Proctor tests for placement density
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Moisture Correction
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Moisture Correction
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"N" Factors
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Compressive strength of a sample may not ensure quality of lot if not properly compacted.
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Dry density test
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Proctor tests for placement density
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QUALITY CONTROL IS MIND SET
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NCR
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Batch No. of cement Bag.
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A small meeting with the concern team which is going to execute every piece work
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Conformation to specification
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concrete
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In construction Simulation is more important that Control
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Moisture content
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CHECKLISTS - Are widely used in QC as a means to check against conformance to the requried Specifications and Standards... These are simple techniques which could be developed over every projects...!!! |
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i think we have to make control plan as per the standards of disaster management and other technical standards we have to check the concert and construction material as part inspection we have to simulate the base structure require for building we have to make a dock audits on mixtures using for construction we can do descriptive and non descriptive test if possible
Quality control is a process. corrective measures also the part of quality control. to decide corrective measures we need data of what is and what went wrong. the check lists are the best documents for the purpose. YES YOUR CHECK LIST SHOULD CONTAIN BEST PRACTICES. SHOULD TELL WHAT IS SUPPOSED TO BE DONE.
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I agree with pragya and anjali with their suggestions but this compressive strength test is important, it is basically done to check the strength of the concrete that has been built and this gives the idea of how strong the structure will be and how long it will stand in the course of time. this has to be done time and again to ensure proper quality.
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In my view durability of Concrete has equal importance as that of Compressive strength. Along with required strength, the concrete should have minimum prosity & honey combing, which canbe otained with optimum workability.
as per above discussion ,slum test and compression test are directly propotional because before the concreting first doing the slum test if, slum is in proper range then go to concreting. its means that concrete acheiving proper strength at its time period as curing is done properly. so my conclusion is that why necessay of compression test,one major draw back of this test is that this test is done after structure is acheiving proper strength.
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No one test or technique is more important than other when it comes to quality control. It would be inappropriate to rate them. |
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I support TANVIR PARVESH with some rectification, Such that in my opinion some companies were not implementing comprehensive QA/QC strategy, for example they are engaging UN qualified peoples in QC for only show that they have quality personals, but their aim is to increase their productivity not Quality so if an unqualified person caked the quality even in ISO Companies wht will be the result of product U Understand Better.
Anjali ji,
If u want 2 know d QA/QC strategy, den u hav 2 know bout d properties of the material usin at the site. some preliminery things like gradation, water absorption, sp. gravity, aiv, etc. At d time of design u hav 2 consider all dese properties. n at d time of execution u hav 2 check regularly all dese properties weather it is like earlier or nt. if nt den u hav 2 modify ur design as per d requiement. Please note moisture correction is a vital factor 2 run ur design smoothly at d time of execution. sometimes u hav 2 check d properties of d cement also which u are usin.
If U follow all dese den ur design'll never fail.
Tanvir ji can you please elaborate as how QA/QC strategy will help in quality control in the construction work.
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The test is conducted for quality concrete mixes of medium & high workability. The test is carried out by filling a slump cone with freshly mixed concrete, which is tamped with a steel rod in three layer, which raises the concrete layer by few inches with the addition of plasticizers.
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Slump cone is instantenous measure of workablity of the concrete. We have been using it for long and it gives failry good result. It gives u indication of workabilty of concrete and on seeing the result of slump cone u can adjust water cement ratio.
I agree but as all of you know that this method of testong is not reliable ,we use slump cone test fron the decades back. This method tequire modification. with same material this method give different results, creats doubts for its reliability. So please think to eliminates its drawback.
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1.Steel - Weight of rod per metre,bend & rebend test,ISI 2.Concrete - Slump test,Water cement ratio 3.River sand - Silt content,Bulking of sand 4.Coarse aggregate - Elongation and Flakiness index 5.Bricks - Weight,Size,Water absorption test
6.Soil - Proctor compaction or Core cutter method |
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Maintaining Quality control at site is very subjective and lengthy to discuss here is very difficult. The quality control means it never depends on solely conducting compressive strength test. As some gentlemen discussed durability is also very important. Because even if u provide rich concrete if u dont follow the required cover for steel and proper plastering the concrete or brickwork will become weaker. And also for roof we have to provide proper integral water proofing and external finishing of acrylic based material which protect the building for long life. We need periodical maintainace to keep the structure safe. We should have check list for checking of each and every subhead of construction ie concrete work,brick work,wood work,steel work,flooring,roofing etc etc. To have a better quality of work the check list for each and every sub head shall be thouroghly examined and all the mandatory test shall be conducted peridically. But in govt departments i find it is being neglected very badly and only paper sake the will some reports true to the required BIS standards!!!!!!
Mera Bharath Mahaan.
N.S.Rao
A.E,CPWD
Dear Vimalan U have missed following
Tensile strength for steel
Elongation test
Compressive strength for bricks.
Yes I am totally agree with Vimalan. By taking all the points which is suggested by Vimalan in mind we will control Quality control at site
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Precast Prestressed concrete can impart quality construction, as it is being under controlled conditions of factory. Quality inspection of precast units are pssible before their installation in the structure. |
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YES THIS OPTION FOR THIS QUESTION IS WRONG...this is not a quality control technique.
Precast Prestressed Concrete that is to be decided before commencement of work/project it is not a quality control technique at the construction site for R.C.C. strcture.
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First we need........ TEAM OF INDEPENDANT/COMPETENT/HONEST PERSONS for quality control at any construction site.............otherwise no technique can work......few basic techniques are listed below.... 1. procuring material from the reliable sources.... 2. employing skilled workers.... 3. follow the construction procedures... 4. test the materials/product i.e. sand/aggregate/cement/steel/fittings etc. |
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Each and every material received at site must be checked as per the technical specification.
Compressive strength of a sample may not ensure quality of lot if not properly compacted.
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Compressive strength: Compressive strength of concrete gives a fair idea of quality of concrete. Compressive strength is checked to asses strength of RCC members to compare it with design strength/characteristic strength. This test is to be carried out at regular intervals. Nowadays at all major projects design mix concrete is used and cube tests are to be carried for each pour of concrete. But it is pertinenet to point out that even if compressive strength of the cube is as per design Mix ,quality of concrete can not be 100 % ensured. If concrete is prepared as per design Mix in a automatic batching plant but not properly compacted at site strength achived at site by RCC member can be diffrent from a sample which is taken at batching plant. In view of the above it is very important concrete prepared as per design mix is transported to site of laying without loss of water cement ratio and properly compacted at site so that there are no voids in the concrete. Small increase in percentage of voids will decrease strength considerably (by large percentage). We can not simply rely on compressive strength only and site engineers are to be careful while placing concrete at site to ensure proper compaction and avoid any kind of seggragation. |
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Mr. Sreenivasa Rao,
In ready mix concrete retarders are added to increase initial setting time. Hence before pouring concrete it is recommended to check water content with the help of slum-cone test and moisture correction can be made.
Mr. Sreenivasrao in ready mix concrete the plastisiser and retarders are used to increase initial setting time of concrete. Hence it is recommended to check slump cone test and accordingly the reqiured quantity of water and plastisiser are to be added.
Sir,
Compressive strength is the true measure of the strength of the concrete. Infact as you discussed about the transportation of the concrete without loss of the W/C ratio in RMC we are using admixtures ie plasticisers for giving the proper workability. That holds good for keeping the concrete workable. But some times i found as you said there is reduction in W/C ratio if the RMC brought for casting of the small elements like pedestals, columns,lintels etc.In such cases i find additional water being added site before placing which isnot correct. Hence in Hyderabad we are using only batching plant for small elements and RMC for all major concreting only ie for footings, Plinth beams, roof beams and slabs.
N.S.Rao
A.E,CPWD
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A simple or modified proctor density test equipments are very essential for construction of large scale embankment |
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Adding to Pragya's point, one should not forget the importance of the training the lowest level supervisory staff. The scale of any civil engineering project is so huge that the cycles of the construction activities are large in numbers and the repetative qc check actions tend to bring fatigue and hence the neglegence. The supervisory staff needs to be trained and imphasized the importance of the strength of even a smallest component of the structure in the struvture as a whole.
Adding to joshi point, one should also do construction monitoring, create and maintain daily log of the construction operations, shop drawings, respond to RFI (requests for information), prepare contract change order documentation, prepare cost estimating for field change orders, prepare weekly construction reports, prepare monthly payment vouchers, review and maintain contractor's project schedule, document the construction with digital photographs, supervise and check laboratory sample testing, prepare documentation for field change orders, conduct periodic jobsite meetings, conduct or supervise training O&M personnel, prepare or supervise preparation of O&M documentation, conduct or supervise start-up and commissioning, prepare as-built drawings, provide home office support for large design contract modifications, provide project start-up & commissioning.
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To control quality of concrete, day to day moisture correction is neccesary so as maintain correct water cement ratio then only it is possible to achieve acceptable limit of compressive stregth. |
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To control quality of concrete, day to day moisture correction is neccesary so as maintain correct water cement ratio then only it is possible to achieve acceptable limit of compressive stregth. |
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If slump value is less by adding the more water is there any effect on the strength of the concrete because we are differing the actual W/C ratio required as per the design mix. I too agree that we are adding admixtures in RMC for increasing the intitial setting of the concrete .But suppose slump reduced less than specified then how to maintain the exact water cement ratio ? Particularly in this summer season i noticed water is being dried off quickly since pumping is not being used for small elements.
nsrao
Moisture correction: Well this correction is to be applied after checking moisture content of consituents of the concrete i.e aggregate and sand. This is becuase these materials are supposed to be dry when mixed with cement and water. If there is moisture in these materials then correction is to be applied to balance water cement ratio and quantity of water is proportionately reduced.
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Hi All There are many ways were we can define,
improving & control the safety in construction industry. Kindly find few of
my thoughts around it based on my exposure in Indian & US construction
industry. Few of points may not suit the Indian side due to cost and
exposure...Quality is also directly/indirectly linked to safety process/framework/standards. Quality – Design Decisions Safety - largely depends upon education, vigilance and
cooperation during the construction process. Workers should be constantly alert
to the possibilities of accidents and avoid taken unnecessary risks. Organizing - US Occupational Safety and Health
Administration (OSHA)- routinely conducts site visits of work places in
conjunction with approved state inspection agencies Work and Material Specifications - American Society
for Testing and Materials (ASTM), the American National Standards Institute
(ANSI), or the Construction Specifications Institute (CSI) Performance
specifications- e.g. Concrete payment strength (Load Ratio vs Pay
Factor) Total
Quality Control - International Organization for Standardization's
ISO 9000 standard Quality Control by Statistical Methods –
Sampling by Attributes - Sampling
by Variables General Choice of technology can also be critical in determining
the safety of a jobsite. Safeguards built into machinery can notify operators
of problems or prevent injuries. For example, simple switches can prevent
equipment from being operating when protective shields are not in place. With
the availability of on-board electronics (including computer chips) and
sensors, the possibilities for sophisticated machine controllers and monitors
has greatly expanded for construction equipment and tools. Educating workers and managers in proper procedures and
hazards can have a direct impact on jobsite safety. Regular safety inspections
and safety meetings have become standard practices on most job sites. Pre-qualification of contractors and sub-contractors with
regard to safety is another important avenue for safety improvement. If
contractors are only invitied to bid or enter negotiations if they have an
acceptable record of safety (as well as quality performance), then a direct
incentive is provided to insure adequate safety on the part of contractors. During the construction process itself, the most
important safety related measures are to insure vigilance and cooperation on
the part of managers, inspectors and workers. Vigilance involves considering
the risks of different working practices. In also involves maintaining
temporary physical safeguards such as barricades, braces, guylines, railings,
toeboards and the like. Sets of standard practices are also important, such as: -requiring hard hats on site. -requiring eye protection on site. -requiring hearing protection near loud equipment. -insuring safety shoes for workers. -providing first-aid supplies and trained personnel on
site |
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Compressive strength of a sample may not ensure quality of lot if not properly compacted.
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Compressive strength: Compressive strength of concrete gives a fair idea of quality of concrete. Compressive strength is checked to asses strength of RCC members to compare it with design strength/characteristic strength. This test is to be carried out at regular intervals. Nowadays at all major projects design mix concrete is used and cube tests are to be carried for each pour of concrete. But it is pertinenet to point out that even if compressive strength of the cube is as per design Mix ,quality of concrete can not be 100 % ensured. If concrete is prepared as per design Mix in a automatic batching plant but not properly compacted at site strength achived at site by RCC member can be diffrent from a sample which is taken at batching plant. In view of the above it is very important concrete prepared as per design mix is transported to site of laying without loss of water cement ratio and properly compacted at site so that there are no voids in the concrete. Small increase in percentage of voids will decrease strength considerably (by large percentage). We can not simply rely on compressive strength only and site engineers are to be careful while placing concrete at site to ensure proper compaction and avoid any kind of seggragation. |
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Compressive strength of concrete is very important to justify the quality of structure.
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I like to add another suggestion for quality control is dry density test it is done to determine the required amount of water to be used when compacting the
soil in the site and the resulting degree of denseness, which can be expected from compaction at optimum moisture content. |
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A simple or modified proctor density test equipments are very essential for construction of large scale embankment |
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All Quality Control is process. First define what is quality. set it as a goal. device a process. set your mind reach that goal. |
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The Batch No. on every cement bag mention Week:Month:Year. What ever is the date mentioned on cement bag, it is to be consumed within one month of period. |
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A lot of test is there in QA&QC for prior and after the construction. No one can watch commpletly like proper control over material, mixing, placing, compacting, curing, etc., You can go for UPV for final result for integrety of the structure. But my point is, we become habituate by doing the same work daily and moreover the direct work is executed by skilled & unskilled workers. If we discuss with them regarding the importance of structure durability & finishing, then definetly you will find the difference. so, in my point of view, this is the very simple, easy, best possible solution |
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Mr. Thyagraj,
Ultra sonic pulse velocity is the ultimate test for testing the concrete. One must be confident on his working but should not forget that 'Precuation is better than Cure'.
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Any way I am not able to understand your question fully..but to control quality of construciton product at side there has to be specifications and standards to be developed on which one can compare with actual obtained results for measurement of variance or bias.It cam be in terns of cement grade,Ratio of water,sand to cement,strength test of walls agains defined specifications, and variousother defined parameters for construction quality.
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Find the propertis of Materials, Climatic Condition Before making concrete mix, Do the trial mix. |
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Quality control is more important in construction but more than that Productivity is most important... see the final product when we call it ? the item is to ready to sell in a market and when we called the productivity is good ..? when it will comes in a specified time and utilization...so you better think about simulation of all the things ...if any case I help to you its my plesure!
mail ID rautkishor01@gmail.com
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According to me this is an important quality control which no construction personnel will forget to do, This is done mainly to check the moisture content of the soil where the structure is going to be built, this is a very important test, as it gives the result that how much pressure it can take, and how strong will the soil hold during construction.
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Well Pargya i dont think it is so important point (Moisture test) for taking up construction at any site for a construction engineer. Yes this aspect is definelty looked into by a geotechnical expert who carries out soil investigation and recomends a bearing capacity to be adopted for design of foundations. Once bearing capcity is recomended by the expert no further tests are required to be done at site of conctruction for taking up construction work.
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