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Materials Testing Laboratories

Twining has been at the forefront of construction materials testing for over a century. Our network of seven state-of-the-art laboratories, complimented by our fleet of mobile laboratories, allows us to provide in-house testing for projects throughout California. Twining provides fast, reliable test results that our clients can count on.

Twining subscribes to the most stringent certification, inspection, and/or accreditation requirements in the industry. We are accredited by the AASHTO Accreditation Program, inspected by the Cement and Concrete Reference Laboratory (CCRL) and AASHTO re:source, and are also recognized by agencies including Caltrans, Division of the State Architect (DSA), International Accreditation Service (IAS), and U.S. Army Corps of Engineers along with numerous cities and counties as a certified geotechnical, asphalt paving, materials testing and inspection laboratory.

In accordance with our accreditation by the International Accreditation Service, we rigorously verify the calibration of all test equipment utilizing a controlled Quality Assurance Program meeting the specifications in ANS/ISO/IEC Standard 17025 and standards traceable to the National Institute for Standards and Technology. We also maintain a rigorous training program for our experienced staff of testing technicians that is overseen by registered civil engineers.

Construction Materials Laboratories

Our construction materials laboratory is capable of testing virtually any structural material utilized in modern construction. Our labs are accredited by the AASHTO Accreditation Program. All testing is performed per relevant American Society for Testing and Materials (ASTM) or California Test Methods (CTM). In addition, custom or modified test procedures can be performed upon request. Some of our testing equipment and capabilities include:

  • Up to 600,000-pound universal test machines
  • Charpy V Notch test apparatus
  • Rockwell hardness testing machines
  • Welding procedure qualification record and welder qualification testing
  • Full range of concrete masonry unit block testing
  • Facilities for chemical and physical analysis of cementitious materials, chloride permeability and a vast range of specialized tests

In support of steel and metal testing equipment, Twining maintains a complete machine shop. This allows us to make standard test specimens from submitted items. We are capable of testing everything from the size of reduced section coupons to full scale beam column connections. The company also has the unique ability to manufacture special fixtures, jigs and other apparatus as may be required for unique test requirements as they arise.

Geotechnical Engineering Laboratories

Our fully accredited geotechnical engineering laboratory is equipped to perform the standard tests needed in geotechnical engineering evaluations, including but not limited to:

  • In situ density and moisture content
  • Atterberg limits
  • Sieve Analysis
  • Maximum Dry Density
  • Direct Shear
  • Consolidation
  • Expansion Index
  • Sand Equivalent
  • Cleanness Value
  • Soundness
  • R-value

Materials tested are typically obtained from bulk or driven (SPT and Modified California) samples. All laboratory testing operations are overseen by a registered geotechnical engineer. With the large amount of construction-related, time-sensitive work that Twining performs, our laboratory understands the importance of and effectively accomplishes efficient turnaround times for testing.

Asphalt Laboratories

Twining’s asphalt testing laboratories house the most cutting-edge testing equipment and are staffed with experienced technicians certified by Caltrans under the independent assurance program. Our testing equipment enables us to perform design, quality assurance/quality control, and research testing services, and includes:

  • Hveem California kneading compactor and Cox and Sons fully automated axial testing systems
  • Marshall mix design and testing
  • Superpave gyratory testing equipment and design
  • Pavement profilograph
  • Moisture sensitivity
  • Rubber binder design profile testing

Twining’s asphalt laboratories give us the ability to design and test pavement preservation materials including bonded wearing courses, open grade asphalt concrete, chip seals, slurry seals, and cape seals. Twining is also capable of testing emulsion for specification compliance.

The asphalt pavement division at Twining often depends on its laboratory to provide accurate and quick turnaround for some of the most critical projects. In the occasion that a project requires onsite testing, the asphalt pavement division maintains a fleet of mobile laboratories that are custom designed for each project’s needs.

Mobile Laboratories

Mobile laboratories are self-sufficient units set in box trucks, trailers, or recreation-type vehicles depending on the scope of testing to be performed and on the project site conditions. First designed and introduced to the industry by Twining, mobile laboratories are now widely used in California for on-site testing of rapid strength concrete. They have serviced more than 300 pavement replacement projects throughout the state and Twining has collaborated with premier research centers to bring this innovative testing approach to other states.

Rapid strength concrete, capable of achieving flexural strength of 400 psi or more in 1.5 to 4 hours after placement, is an ideal material for fast-track rehabilitation of pavements and construction of new pavements during short-time partial lane closures. Quality assurance requires testing of rapid strength concrete for flexural or compressive strength prior to opening lanes to traffic, and our mobile laboratories are ideal for this.

Mobile laboratories designed and built for on-site testing of concrete, contain the following equipment and accessories:

  • Compressive testing machine(s)
  • Fixtures for flexural strength testing and compressive strength testing
  • Calipers and micrometers for measuring specimens
  • Thermometers and multi-channel temperature recorders for monitoring temperature of in-place concrete and test specimens
  • Curing containers, thermal insulated containers for temperature matching curing of cylinders for compressive strength, thermal insulated cover boxes for temperature-matching curing of beams for flexural strength, etc.
  • Equipment for sampling concrete, fabricating test specimens and testing properties of fresh concrete
  • Portable gasoline generators
  • Stationary mounted water tanks with pumps
  • Curing/storage devices for transferring specimens not tested in the field to stationary or portable laboratory facility

Where required, concrete field testing can also be supplemented to test aggregates. Laboratories of this class use a bigger size vehicle. They also can be set in a separate vehicle or trailer, which allows us to locate such laboratories conveniently at origination of aggregate samples (concrete batch plants or quarries).

Aggregate testing units are equipped with:

  • Splitters for preparation aggregates for further testing in field conditions
  • Portable mechanical and hand sieves
  • Ovens for drying aggregates
  • Washing devices
  • Scales
  • Special aggregate testing equipment as required

For projects where concrete specimens are required to be tested on-site in 28 days or later, Twining has designed portable laboratories that include curing units. Curing units are thermally insulated, air conditioned, steel portable containers. For curing cylinders, the container is provided with fogging system and storage racks. The container for curing beams is equipped with lime water curing tanks. Both types of containers can be used for initial and final curing of concrete specimens, according to ASTM C31 provisions. Storage capacity of a standard 40’ x 8’ portable curing unit is 350 beams. Storage capacity of a 20’ x 8’ portable curing unit is 750 cylinders.

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