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Monday, April 17, 2017

Quality Control During Construction

Quality control represents increasingly important concerns for project managers. Defects or failures in constructed facilities can result in very large costs. Even with minor defects, reconstruction may be required and facility operations impaired. Increased costs and delays are the results. In the worst case, failures may cause personal injuries or fatalities. Accidents during the construction process can similarly result in personal injuries and large costs. Indirect costs of insurance, inspection, and regulation are increasing rapidly due to these increased direct costs. Good project managers try to ensure that the job is done right the first time and that no major accidents occur on the project.
As with cost control, the most important decisions regarding the quality of a completed facility are made during the design and planning stages rather than during construction. It is during these preliminary stages that component configurations, material specifications, and functional performance are decided. Quality control during construction consists largely of insuring conformance to these original design and planning decisions.
While conformance to existing design decisions is the primary focus of quality control, there are exceptions to this rule. First, unforeseen circumstances, incorrect design decisions or changes desired by an owner in the facility function may require re-evaluation of design decisions during construction. While these changes may be motivated by the concern for quality, they represent occasions for re-design with all the attendant objectives and constraints. As a second case, some designs rely upon informed and appropriate decision making during the construction process itself. For example, some tunneling methods make decisions about the amount of shoring required at different locations based upon observation of soil conditions during the tunneling process. Since such decisions are based on better information concerning actual site conditions, the facility design may be more cost effective as a result.
If you are a Civil Engineer or a Quality Engineer and you are new to the field of construction and guess why? I am writing this because I am going to show you, what are the tests to be applied in the particular activity on your ongoing project.
This will become your guide on making your tests on your ongoing project. Like me when I was a newbie in the construction, I don’t have an idea then “what are the tests to be done?” So this would be a great way to write a post for you to learn fast.
There are various tests needed in different areas of site activities whether it is in infrastructure or building projects. Infrastructure projects like road, embankment, bridge, viaduct, tunnel, dam, etc. In the building project, it has a common test that normally done which I will show in the preceding paragraph.
So let us proceed with the following different types of test in different areas of your site.
On Infrastructure & Road Projects

1. Soil analysis – If you need to backfill a part of your road project then you will will require a borrow area, there you will take at least five (5) samples in different locations to determine the suitability of the soil. The test that will be done are proctor test, California bearing ratio (CBR), atterberg limits, organic matter, etc.
2. Field density test or In-situ density test –  Some people called it compaction test and some other called it in-situ density test, but in fact, it has similar test procedure. Here is the meaning of a compaction test “is a soil quality test used to assess the level of compaction, which can occur in the soil on a site.”
To determine the result of compaction the test shall be conducted further in the laboratory to get the result, where they would make further weighing the soil sample, drying it in the oven, and last calculation and then the result. A road project (rigid pavement) has different types of layers. The first layer is sub-base, second is base course, and the last layer is the concrete pavement.

Each layer, excluding the concrete pavement has to be compacted to the required degree of compaction. The sub-base is usually to be compacted to 95 percent of maximum dry density and the base course is 100 percent of maximum dry density but please refer always on your respective specification.
3. Flexural strength – Here is the meaning of Flexural Strength “Flexural strength, also known as modulus of rupture, bend strength, or fracture strength, a mechanical parameter for brittle material, is defined as a material’s ability to resist deformation under load.”
The strength requirement varies depending on the specification, but here on our site, the specification says 4.6 Mpa for 28 days strength.
On building projects 
In building project, there are several kinds of tests that you should expect. Our first project in Dubai was having an approximate area of 119, 000 square meters consists of 9 buildings with one common parking. Here are the quality tests that we have done and you also might conduct these on your building projects.
1. Soil Investigation – The purpose of the soil investigation is to determine the surface and subsurface conditions of the project and the physical, chemical and mechanical properties of the ground in order to provide the structural engineer with sufficient information for the design of the most safest and practical design of foundations.
2. Plate load test – This test is sometimes taken on below slab-on-grade or on the foundation, but it would depend on your specification, this is in order to just verify the bearing capacity of soil which have taken from the soil investigation.
3. Soil analysis (Sampling) – This test shall be done prior to compaction test in order to determine the suitability of the soil to be used for backfilling. The sampling test includes atterberg limits, sieve analysis, organic matter.
4. Proctor test – The proctor test result shall be used in the calculation of the degree of compaction or in-situ test report. That is why it is necessary to do first the proctor test prior to compaction test. Here is the meaning of proctor test “It is a laboratory procedure of experimentally determining the optimal moisture content at which a given soil type will become most dense and achieve its maximum dry density.”
5. Compaction test or In-situ density test –  Compaction test is a soil quality test used to assess the level of compaction, which can occur in the soil on a construction site. Compaction test for building projects shall be done below footings, tie beams and slab-on-grade, but note; if granular backfill (Engineered fill) is required below slab-on-grade you shall then compact it to 100 percent of maximum dry density.

6. Compression test of concrete –  Most commonly the specification says 3 cubes will be taken for 7 days compressive strength test and another 3 cubes to be tested for 28 days to get the specified strength of concrete.
7. Durability test – The durability test commonly consists of; water penetration and water absorption test. The requirement for water penetration is not more than 10mm and the water absorption most commonly require not more than 20 percent.
8. Mechanical and chemical test – This test is for reinforcing bar that you are going to use on your project site which includes bending, tension test etc. Before you use the steel reinforcement, as a quality engineer or an inspector, you shall send the samples of 3 for each diameter to an approved independent laboratory.
9. Compression test for CMU – This test is sometimes mentioned on your specification. The tests include, dimension test and compression test. Three samples of each size of CMU have to be sent to approved independent laboratory.
10. Non-destructive test – This test shall be done on steel structure and it is usually done in the fabrication plant. The non-destructive test consists of Magnetic Particle Inspection, Ultrasonic Inspection and Water Penetrant Inspection. The non-destructive test shall be performed by an independent laboratory approved by the consultant. The non-destructive test should be done if it is mentioned in the specification if not the tests shall be done internally as per quality standard procedure of the fabrication company.
There are many more tests to be done in the construction project, what I wrote here are just a really important one and others shall be done during the project is in progress and in sometimes by consultant or client’s willingness to do so.
If you have suggestions and supplements to the above test, you may write down in the comment box below.
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