What Does a Wind Farm Construction Materials Testing (CMT) Technician Do?
By: Chris Alexander, Senior Engineering Technician
Senior Engineering Technician and CMT Project Manager, Chris Alexander, walks us through a day in the life of an RRC companies’ Construction Materials Testing Technicians and their various roles. CMT technicians are crucial to providing both field and laboratory testing to maintain the viability and safety of our client’s Wind Farm sites and projects.
In truth, there really isn’t a typical day for a Construction Materials Testing technician. The CMT technicians’ day depends on the scope of work, especially during a project that involves concrete and soils testing on wind turbine foundations. The technician’s tasks can change day-to-day based on our client’s needs and requirements for the project. Although our work is repetitive on each project we are assigned to, our client’s needs and requirements are not always the same. Some clients require faster paced testing and some clients require certain types of tests that may be project specific.
RRC technicians conduct a vast amount of testing in a typical 10-12 hour day and clients tend to work 6 days per week. Projects that require concrete and soils testing will typically at least three technicians: one dedicated to overburden backfill, one to concrete, and the other is known as a “lead technician” that observes foundation excavations, reinforcing steel placement, performs concrete breaks, and serves as the main point of contact for the client.
Lead Technician
Schedule for a Lead Technician on a Wind Farm: Onsite at 6 AM.
- 0.5 hour: Contractor Plan of the Day meeting
- 1.5 hours: Review previous day’s reports and submit to client
- 4 hours: Rebar inspection
- 3-4 hours: Subgrade inspection
- 1-3 hours: Coordinate construction issues with RRC engineering staff
Expert Planning
To start the day, the lead technician attends the client’s Plan of the Day (P.O.D.) meeting to discuss the upcoming day’s activities with their superintendents, supervisors, and subcontractor leads. Once the meeting is over, the lead technician reviews reports from the previous day to check test data and specifications. He then finalizes the reports and submits them to the PM. When the project is staffed with three technicians, the review process can take a few hours since approximately 100 pages of reports are generated each day.
Compressive Strength Tests
The lead technician then performs compressive strength tests. Since construction activities depend on the strength of the concrete, clients require that some of the compressive strength data be available to review earlier in the day to allow some field operations to proceed. On a typical day, we break and discard about 70 cylinders (each about 9.5 lbs.) and 18 grout cubes (each about 0.5 lb.). Since the process takes so long, the lead technician will often need to pause compressive strength testing to perform field inspection.
Reinforcing Steel Inspections and Excavation Observations
The lead technician spends a few hours each day inspecting base and pedestal reinforcing steel. This is a detailed task and it is often time sensative. The contractor cannot place concrete until these rebar inspections are complete. The lead also performs excavation inspections for a few hours a day. This requires testing subgrade soils and inspecting the excavation to meet the geotech engineer’s expectations.
Other Tests and Inspections
The lead technician also assists with other aspects of the project. He might conduct tests and inspections at the electrical substation. There are often miscellaneous concrete tests across the project, such as for culverts, or transmission line structures. Some projects require Dynamic Cone Penetrometer tests. These DCP are physically exerting as they require raising and dropping a 17.4 lb hammer numerous times. Other soil tests might require a Static Cone Penetrometer.
Effective Communication
Should the client have any concerns regarding the testing activities, or a construction issue requires consultation with RRC engineering staff, the lead technician is responsible for coordinating the communication and managing the resolution of the issue on site. This may be as simple as making a phone call or it may require several conference calls, meetings, and additional testing to provide RRC engineers with the data necessary to provide solutions for the contractor. This is possibly the most critical function of a lead technician since project progress often comes to a standstill until the issue is resolved.
Overburden Technician
Schedule for an Overburden Technician on a Wind Farm: Onsite at 6 AM.
• 1-2 hours: Collect and deliver previous day’s concrete and grout samples (800 to 1400 lbs. of samples per day, depending on the number of samples cast the prior day)
• 9-10 hours: Perform backfill compaction testing (2-4 foundation locations per day and at least 16 tests per location)
Retrieve, Process & Cure Concrete Samples
The technician dedicated to overburden backfill testing will start their day collecting concrete samples from the previous day’s placements. This often happens while the lead technician is attending the P.O.D. meeting since the overburden backfill crews will begin construction activities around 8 AM. The daily collection of concrete samples consists of picking up the concrete samples and grout samples and transporting them back to the onsite lab for processing and curing. On a typical day, the technician is picking up 11 to 12 coolers with 9 cylinders in each cooler (approximately 100 lbs. per cooler) and 4 grout coolers with a minimum of 4 grout molds in each cooler (approximately 40 lbs. per cooler). This equates to over a half- ton of weight being picked up, transported, unloaded at the field lab on a daily basis.
At the lab, the technicians unload and organize the samples by set. This organization is a very important issue. Then, the technicians strip the cylinders from their molds and remove the grout cubes from their brass molds. They then use markers to label every sample with a unique ID. Samples then are placed in the cure room. Processing cylinders/cubes requires at least a couple of hours. As such, often, technicians conduct this task throughout the day when they have time between other field tests.
Expert and Thorough Overburden Testing
The technician is required to stay with the overburden backfill crews all day. Usually, the backfill technician is responsible for testing 2-4 crews at one time and is constantly on the move back and forth between crews. On a typical day, the technician might test 60 to 70 density tests, not counting failures. Each test requires a 30 lb nuclear density gauge. The technician makes a probe hole into the ground using a 10 lb hammer. The technician documents the passing tests, the soil lift for each foundation, and keeps the contractor informed of the results. Often, the different contractor crews performing backfill are not always within close proximity of one another. It is not unusual for the technician to travel 10-20 minutes between overburden crews to perform tests.
Concrete Technician
Schedules for concrete can vary depending on weather. During hot summer weather, it is common to work during the night.
- 1 hour: load equipment, travel to first test location, prepare test work area.
- 9-11 hours: Sample concrete and cast cylinders.
- Typically, 2-3 foundation locations per day:
- WTG bases vary from 600 to 900 cubic yards of concrete – each.
- WTG pedestals are typically 25-35 yards.
- A technician moves about 2000 lbs. of wet concrete by wheelbarrow each day.
- 1200 lbs. of cylinders cast and stored each day
American Concrete Institute Certified
RRC employs concrete technicians that are certified by the American Concrete Institute (ACI). Many factors play into what time of day the concrete crew works. Delays due to rebar completion or delays due to problems with the batch plant are common. In general, though heat or extreme cold dictate the concrete work schedule, as these factors affect the performance of concrete.
The beginning of the shift is always the busiest for the technician testing concrete. RRC tests the first 3 concrete mixing trucks of the day prior to any concrete being placed in the foundation. As this testing occurs, approximately 10-15 other trucks arrive at the location to begin placement. All construction activities are on hold pending the results of the first 3 tests of the shift. With all eyes on the RRC technician, it makes for an entertaining and busy 30 minutes. After the initial testing, the technician rapidly cleans the testing equipment to get ready to test the first production truck and to cast cylinders for compressive strength testing.
Expert Concrete Observation & Testing
Along with casting cylinders, the technician will measure ambient and concrete temperatures, perform a slump test to measure concrete workability, measure unit weight, and measure the air content of the concrete mix. Testing is repeated every hour during the shift. The technician will cast about 108 cylinders during each 10 to 12 hour shift. During the entire day, the technician will use a wheelbarrow to move a ton of wet concrete samples. In between tests, the technician observes the concrete pour and the contractor’s work to ensure it is being placed within the project specifications. If the technician notices inconsistent mix properties, he will conduct extra tests. During all of this, he is in constant communication with the concrete contractor’s supervisor.
Dedication
After a long day of work, the technicians depart from site to return to their hotels. Wind projects are rural, which often means that the hotel is a 30 to 60-minute drive from the project. Each technician will remain dedicated to the project for 3-5 months at a time, often without the ability to take vacation. During the summer, which is usually the most demanding, the work is performed in extremely hot temperatures, with the wind, dust, and sweat that accompanies their work environment.
Because of the remote location of most windfarm projects, it is common to have zero or poor cell phone signal. The only chance they have to connect with their family or friends is when they return to their hotel. The sacrifices made both personally, physically, and mentally require uniquely suited individuals.
RRC’s integrated team of engineers and field technicians have extensive experience in observing and testing excavations, reinforcing steel, roadways, concrete, backfill, grouting, and many other site-related operations.
To learn more about what RRC offers in Wind Construction Materials Testing go to our website at https://rrccompanies.com/markets/wind-power/ or contact [email protected].