Quality Assurance of Civil Infrastructure Works in Projects

Quality assurance tests are carried out at various stages in a project:

• Initiation / Feasibility Stage (Before construction)
• Execution Stage (During Construction)?
• Closing Out Stage (Pre-commissioning)

This article is based on my work experience on civil infrastructure projects for over a decade and it can serve as a guide for all professionals and non-experts in the built and engineering industry. Feel free to share your own experience and thoughts in the comments.

Quality Assurance - Structural?Works

Concrete is one of the most common materials used during construction.?Here are some quality tests conducted before and after the completion of casting on site.

a. Slump Test

This is to determine the workability of concrete. After batching, a sample of fresh concrete is taken for slump and compressive tests.??

Slump Test

b.?Compressive Strength Test

The compressive strength of the concrete cube test provides an idea about all the characteristics of concrete. By this single test one judges whether Concreting has been done properly or not. Concrete compressive strength for general construction varies from 15 MPa (2200 psi) to 30 MPa (4400 psi) and is higher in commercial and industrial structures.

c.?Schmidt NDT Test or Rebound Hammer Test

It is carried out for the evaluation of the surface hardness of concrete structures. The surface hardness of concrete is an indication of its strength of concrete.

Rebound Hammer Test

d. Impact Echo Test

It is used to detect the location and extent of defects such as cracks, voids, delamination, honeycombing, and debonding in plain, reinforced concrete, and post-tensioned concrete structural members.

Quality Assurance - Foundation Works

a. Standard Penetration Tests

The standard penetration test, commonly known as 'SPT' is a preliminary soil investigation, which is?developed to provide geotechnical engineering properties for foundation design purposes. The test is carried out within a borehole. The results can be used to determine the relative density, bearing capacity, and settlement of granular soil.

Standard Penetration Test

b. Cone Penetration Test?

A cone penetration test is used?to determine the geotechnical properties of soils. The CPT is a detailed soil investigation test method for determining geotechnical soil properties and construction quality control.

Quality Assurance - Electrical?Works

Electrical installations for buildings are either internal or external. Their primary function is to provide illumination and power supply to internal lighting and electrical appliances. Internal electrical installation of a building consists of cabling and associated ancillaries such as switches, sockets, distribution boards, and light fittings.?The following tests are carried out on Internal Electrical installation (Pre-commissioning):

a. Insulation Resistance Test

The completed installation is tested by applying resistance between the earth and the whole system of conductors, with all fuses in place and all switches closed. This is strongly recommended to prevent electrical shocks and assure safety of personnel.

b. Polarity Test of Switch

A test shall be carried out in a two-wire installation to verify that all the switches in the circuit are fitted in the same conductor throughout the supply.

c. Earth Continuity Test

The earth continuity conductor, including metallic envelopes of cables and metal conduits, shall be tested for electric continuity.

d. Earth Electrode Resistance Test

This test is used to measure and confirm the earth resistance between the electrode and “true Earth”.

Other electricity supply protection setup/equipment in a building are: Lightning arresters, surge protectors, fuses, and relays with associated circuit breakers, reclosers, etc.

Quality Assurance - Mechanical?Works

The following tests are carried out on mechanical works:

a. Fire Protection Services

Pre-commissioning, a fire sprinkler inspection, and a test of all equipment are required. The components inspected include sprinkler heads, control valves, piping, and triggers, and the technician will test that your trigger system functions and adequate pressure builds in response.

b. Mechanical Ventilation Services

Ventilation Tests?ensure that you correctly configure the ventilation systems in your building and that the airflow is of a good standard. This is to maintain a high standard of indoor air quality.

Ventilation Test

Air Quality Tests?are conducted to measure the air for things such as allergens, mold, and radon, among others. These tests can show whether the quality of your indoor air is safe or dangerous.

Quality Assurance - Civil Infrastructure Works

A. Water Supply?

In general, a water distribution system consists of both service and drinking water pipes. The water flows through our pipes at a certain pressure. For the quality and purity of our drinking water, the water mustn't remain in the pipe for long. To make our water as clean as possible, not only pumping stations and pressure boosting stations are used but also the material of the pipe is taken into consideration.?

Pressure Tests?- Pre-commissioning, a pressure test on a water pipe is a method of testing newly fitted pipelines for leak tightness. Pipes to supply water must be able to withstand an operating pressure of 10bar. However, a pressure of 3-6 bar is sufficient to supply single households.

Flow Velocity Tests?- flow velocity tests are conducted and a min. of 0.005m/s is required to mitigate against the stagnation of water which can sometimes lead to bacterial contamination.

Pigging (Air Tests)?- this is a test that is conducted to ensure that a pipeline is filled with water and almost free of air.?An “air-free” filled pipeline is crucial for a successful pressure test!

B. Drainage Services (Storm/Sewer)

These tests should be conducted ideally during the construction phase (before backfilling or final installation)

Drainage Pipe Air Test -?The air test is a quick, convenient method to test single pipes and drain runs. Air testing is a simple, effective method for many drain problems, but it can only be used to test a length of a drain that can be capped at both ends.?

Drain Pipe Water Drop Test-?This is a test for complete drainage systems including chambers and gullies to ensure that it's both functional and water-tight.?

?An air test is carried out on all pipework following installation, while a water test will only normally be required to verify a failed air test or to test manholes or inspection chambers.?

Idealised Air Test Set-Up

Smoke Test?- this can be used to detect leakages but is not recommended for pipe networks of uPVC/PVC materials unless a safe type of smoke canisters is used.

C. EarthWorks

Soil /site investigations are required for earthworks and road construction in general. The following key soil tests are carried out for road construction:

In-Situ Moisture Content?- The moisture content in soil signifies the various properties of soil such as compaction, permeability, particle size, etc.

Particle Size Distribution?- The data from the particle size distribution test is used to determine the suitability of soil for road construction, airfield, etc. This test can also be used to predict soil water movement.

Atterberg Limits?- this test is used to classify the soil type.

Compaction/Proctor Test?- It is used for the determination of the mass of dry soil per cubic meter when the soil is compacted over a range of moisture contents, giving the maximum dry density at optimum moisture content.

Soil Compaction Test Apparatus

California Bearing Ratio (CBR)- is performed in construction materials laboratories to evaluate the strength of soil subgrades and base course materials.This test provides the load penetration resistance of the soil. Min. CBR for the subgrade is 10%.

CBR Penetration Test

D. Asphalt Pavements

Asphalt is the most versatile pavement material used in the construction industry. Asphalt pavement is made of aggregates, sand, additives, and asphalt and is laid for the construction of driveways, parking lots, roadways, etc.

a. Marshall Stability Test

The Marshall mix design methods help engineers select the optimum asphalt binder content at a density that meets stability and flow value requirements.

Marshall Stability Test

b. Temperature Test

To achieve satisfactory results in paving the asphalt mix and temperature is critical. Hot-mix asphalt should arrive at the job site at a temperature of 135 - 145 degrees celsius. If the mix temperature falls below 85 degrees celsius before final compaction. It may be too stiff to compact properly.

Quality Assurance - Configuration Management?Works?

A common challenge in construction sites is the control of drawings and contract documentation during the implementation phase of projects. The use of old versions/outdated drawings can lead to losses in time and money on a project.

To mitigate against this the project team should have a simple and functional document control management system (DCMS) with an efficient configuration and distribution system that is accessible and duly communicate to all team members.

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REFERENCES

www.theconstructor.org

www.esders.com

www.pavingexpert.com

BS EN 752:2008

Nigerian Highway Manual Vol 1-8

www.qualityengineersguide.com