Careers | Request for Proposal

Concrete Insight

Delivering Innovations to Concrete Construction Industry

Fast Track Rehabilitation & Preservation Concrete Transportation Infrastructure

For almost 40 years Twining has been involved in the research and development of rapid and ultra-rapid strength concrete (RSC) for emergency and planned repair and rehabilitation of transportation infrastructure.  RSC gains compressive strength of 2500 – 3500 psi and flexural strength of at least 400 psi in 1.5 – 4 hours.  In 1998 Twining developed and introduced to the construction industry nation-first mobile laboratories. These autonomous testing units allowed validating the strength of RSC on-site before opening transportation corridors to traffic and became a turning point in expanding the practice of fast-track rehabilitation of pavements and bridges. Results of our laboratory and field studies are widely published and presented nationally and internationally. We provided near 100 training seminars to the industry.

Twining mobile laboratories are equipped to test fresh and hardened RSC.  Curing of specimens is performed in conditions matching the temperature of RSC in place.

Fast-track construction of bridge hinges using rapid strength concrete.

Emergency repair of airfield pavement. Ultra-rapid hardening concrete with calcium-sulfoaluminate cement is often produced with volumetrically measuring and continuously mixing mobile units. 

Placement of the last truckload of RSC during a historic nation and California-first 55-hrs weekend rehabilitation of a pavement segment on RTE-10 in Pomona, in 1999. For this project, Twining received the ACPA National Award of Excellence. 

Toll Buildings

Construction of core structures of tall buildings nowadays widely utilizes high-strength concrete with a controlled modulus of elasticity and validated creep and shrinkage.  The first building in Los Angeles (completed in 2006) that used concrete with a design strength of 10,000 psi at 56 days and 12,000 psi in one year was The Californian at Wilshire Blvd., a novel design by Englekirk Partners (structural engineers) and Nadal Architects. Twining contributed to academia-industry joint studies led by Englekirk, that preceded the use of high-strength concrete in the City of Los Angeles. 

In the past decade, the concrete construction community in California “rediscovered” the effect of aggregates on modulus of elasticity (MOE) of concrete and learned that the true values of MOE can be noticeably different than the ones calculated based on compressive strength, or strength and unit weight per equations permitted for structural design by ACI 318 Code.  Results of research by Twining were presented in the Hot Topic Session of ACI 2017 Concrete Convention and suggested that MOE of concrete for structures where rigidity was critical should have been rather specified than assumed.

Wilshire Grand Center in Los Angeles, the 1,100-foot skyscraper, is the tallest building west of Mississippi (architects A.C. Martin Partners, structural engineers Brandow & Johnston).  Its construction brought many unique concrete material engineering challenges related to both the mat foundation 17.5-foot deep and the core.  Twining assisted in responding to them all.

During continuous construction of 21,200 yd3  mass foundation (2014 Guinness record), Twining provided quality control at 7 batch plants, 13 specially equipped stations next to boom pumps, temperature monitoring of the matt, and technical support to the concrete supplier and contractor.

Water Infrastructure – Reservoirs, Supply Conduits, Treatment Facilities

Water Retaining Structures

One objective of enhancing the quality of concrete construction is the mitigation of cracking. Achieving this objective is especially important for reinforced concrete reservoirs to minimize the loss of water.  The biggest rectangular reinforced concrete reservoirs recently built in Los Angeles are two headworks Silver Lake structures with holding capacities of water of 55M gal (Phase 1) and 68M gal (Phase 2). They were constructed in 2014-2020.  Our team participated in the construction of both reservoirs.  Los Angeles Metropolitan Department of Water and Power engaged Twining as a consultant for developing a new generation of specifications that addressed cracking minimization.  The specifications were implemented for the construction of the Phase 2 reservoir.

Silver Lake Reservoirs

All concrete elements, such as floor and roof slabs, walls, and columns, were massive and treated as mass concrete.  Reservoir floors consisted of several hundred individually placed slabs.  During the construction of the second phase, the sequence of placement was optimized to minimize restraint by adjacent elements during the early, most intense phase of concrete volume changes.  Construction of the second phase giant structure was preceded by the development of a new generation of concrete specifications that were focused on reducing cracking potential, minimizing crack repairs, and enhancing the water tightness of the reservoir.  The total volume of concrete used for its construction was 90,000 yd3.

Water Supply Conduits

Twining’s services are often considered by microtunneling contractors. One of the recent projects was a 30,000-linear-foot major concrete pipe conduit for the transmission of water from LADWP’s North Hollywood pump station.  Twining designed specialty grout mixtures, provided technical support, and quality control testing in the course of their application for the construction.

Silver Lake Reservoirs

For cracking minimization project specifications for Phase 2 were focused on a holistic concept of low-volume-change concrete. Prospective contractors were provided with options of practical solutions for formulating concrete with optimized  (1)  heat generation, (2) thermal expansion & contraction, (3) shrinkage, and (4) early-age tensile strength gain.   Special provisions addressing batching, curing, and thermal control were a part of the cracking minimization protocol implemented during construction. Cementitious materials were formulated to minimize the risk of delayed ettringite formation, an additional contingency measure guaranteeing the durability of mass concrete.

Water Treatment Facilities

The Sterling Natural Resource Center in Highland, CA is a state-of-the-art facility designed to provide a sustainable new water supply to boost the region’s water independence. It is capable of treating up to 10 million gallons a day. Twining developed thermal control plans and provided technical assistance and temperature monitoring of mass concrete placements of various structural elements

Precast Concrete for Water, Sanitation, & Transportation Infrastructure

Our precast concrete laboratories are equipped with pan and drum mixers, steam curing chambers, vibration tables, and internal vibrators to simulate production processes used at precast concrete plants.  We provide technical assistance to precast concrete manufacturers with fine-tuning their production processes, development and preconstruction evaluation of concrete mixtures, and production quality control and testing.  Twining provided engineering support and quality control services to a number of concrete reinforced pipe precasters on many projects including San Diego Ocean Outfall (1996-1999).  We were the first laboratory at the West Coast to set capabilities of testing steel fiber reinforced concrete and shotcrete.  Today steel fiber reinforced shotcrete is often used for soil support behind boring machines.  Steel fiber reinforced concrete is also widely utilized for the production of precast segments for the construction of multi-purpose tunnels.    

Production of a precast tunnel segment using 8,000 psi steel fiber reinforced concrete. We provide a wide range of specialized tests of steel fiber reinforced concrete: US and EN flexural toughness tests (plain and notched beams), and double-punch test

For more than 25 years Twining has been providing concrete engineering and testing services to Traylor Bros, one of the largest tunneling companies operating precast segment plants in the states of California and Washington. Some of these projects are highlighted to the right.

Purple Line

Heavy rail subway corridor in Los Angeles County.

Arrowhead Tunnels, Metropolitan Water District of Southern California

Stretches from Silverwood Lake in the foothills of the San Bernardino Mountains 44 miles southeast to Diamond Valley Lake.

Silicon Valley Clean Water

Wastewater conveyance system serves residents and businesses in the San Francisco Bay area. 

Bay Tunnel, San Francisco Public Utilities Commission

A 5-mile-long tunnel under the San Francisco Bay, passing through environmentally sensitive marshlands and mudflats, with a vertical shaft at each end of the tunnel.