It's 11:30 p.m. in Sebastopol, Calif. Steve Beasely, owner of Bay Cities Concrete Pumping, fires up his 42-meter concrete boom. The engine roars through the late night stillness of his equipment yard. Steve is preparing for a 660 cubic yard slab pour in Rohnert Park at a new Ashley Furniture store. Shaking off his desire to go to bed, Steve shovels some blend sand in the back of the hopper, checks his oil and fuel levels, and inspects his hydraulics and boom pipe. It's pitch black out, save for the headlights on his Schwing boom pump. He'd like to read the paper or maybe have a cup of coffee but he has to hurry; he's got two pumps scheduled and concrete coming at 1 a.m.
Across town and down the highway, Darrell Carpenter, chief of dispatch operations for Norcal Ready Mix Concrete, sits at the scheduling monitor and plans out how to make things work. It's a busy night and if Steve Beasley decides to go to bed, or the laser screed has a problem, or a hundred other things happen, it could be a mess. It's been a slow winter in Sonoma County. Record rainfall has saturated building pads, delaying concrete placement. It's finally dried up and spring has arrived, so now there's an entire county of contractors desperate to salvage their year's profits. It's nice to be working but everyone seems on edge. Jim Hill, president of Norcal, has 22 mixer trucks and could use twice that many right now. But for most of the winter, they have been sitting. In fact the only thing that keeps them going in a wet winter in the north San Francisco Bay Area, is the equipment payments.
Concrete crews ready
At 11:45, cement finishers for Coleman Concrete are sitting in the ‘bullpen' across town waiting. Bill Coleman, known as a top commercial concrete contractor, mulls over the coming night's activities. For over 40 years, Coleman has earned a reputation for high-end concrete construction. At the center of the coffee drinking circle is Fred Watson, backhoe operator. This ex-marine wakes the crew up with verbal jabs and comedic relief. Some laughter is welcome, in a few minutes this crew will be responsible for placing 2.7 million pounds of concrete (660 cubic yards at a little over 4000 pounds each) worth around $264,000 (660 cubic yards at $400 each in place).
But really this won't be too tough an evening for Coleman's crew, other than sleep deprivation. Due to the requirement at Ashley Furniture for an extremely flat floor, the owner has brought in W. Reyneveld Construction from Bakersfield to handle the laser screeds. Willie Reyneveld has assembled a crew that can place up to 100,000 square feet per day using laser screeds that allow them to place it flatter than any human being could do by hand on even their best day. Laser screeds have revolutionized the world of the slab pour: cheaper, faster, flatter. Willie's crew drove up from the San Joaquin Valley the previous day. They would like to have the continental breakfast at their motel, but it won't be served for another eight hours. Tomas Rubio, lead foreman for Renevald, has already positioned the screed on the jobsite and calibrated the lasers. Tonight shouldn't be too bad, provided they get the concrete when they need it—for these guys, 42,000 square feet is an easy day.
Pouring a big slab in the middle of the night allows the concrete supplier to avoid rush hour traffic. Reyneveld is asking for 150 cubic yards to be delivered each hour. That's a 9-cubic-yard mixer load dumped every 3.75 minutes.
Rick Freeman, project manager for Codding Construction, pulls onto the jobsite around midnight. Codding is the general contractor on the job. Freeman and project superintendent Dan Davis have an extremely tight time schedule. From start of footing layout to erection of concrete tilt panels, Codding has given Coleman Concrete nine weeks to complete the work. Tonight marks the end of the third week. Tomorrow, after Reyneveld finishes sawcutting 9000 linear feet of contraction joints, Coleman's foreman, Fred Kurzhals, will start snapping out lines that outline the location of the side forms for the tilt-up panels. This slab will become the working tabletop for construction of 29,000 square feet of concrete panels.
The concrete arrives
At 12:45 a.m. the first of the 17 mixer trucks that will supply the concrete pulls onto the jobsite. Steve Beasely, unofficial captain of the concrete pour, clasps his remote box and uses part of the first yard of concrete to slurry out his boom. Jimmy Johanson, a veteran Norcal mixer driver, reverses his drum to discharge and an easy flow of 3000 psi concrete deposits into the Bay Cities agitating hopper. Equipment revs, the boom truck's reciprocating pistons start to rock, and just before 1 a.m., the pour begins.
Banks of portable lights illuminate the scene. The flow of concrete is deposited from the boom just in front of the laser screed. Using hand gestures and occasionally screaming above the back up beepers, Bill Coleman is directing traffic. Mixer truck two carefully backs up parallel to Johanson and joins to create a steady supply of 1-inch aggregate 5½-sack concrete. Just around a darkened street corner, 15 more fully loaded mixers sit patiently, awaiting their turn to unload.
Brandon Cunningham, field technician for Kleinfelder testing labs, scoops some concrete into four empty plastic tubes. He carefully rods, strikes off, and caps the test cylinders and moves them to a quiet, protected area. These cylinders will be broken at 7, 14, and 28 days to verify the compressive strength of the concrete. One is saved as a spare. Four cylinders are taken from each hundred cubic yards poured.
Reyneveld's laser screed has sprung to life now, its telescoping screed communicating with the lasers that are set up to indicate the exact finished floor elevation. Looking like a landlocked zamboni, it plows into the pile of 4-inch slump concrete, vibrating and leveling with computer accuracy.
By 1:30 a.m. 80 cubic yards have been placed. Coleman's crew works behind the laser, chairing slab reinforcing steel on dobies as the screed continues its methodical path down the grid lines. Fred Kurzhals has his eyes on some anchor bolts and quickly checks to verify the accuracy of their location.
Between the mixer truck drivers, pump operators, testing lab technicians, representatives from the concrete supplier, Coleman Concrete's crews, Reyneveld's crew, Codding Construction supervisors, and various interested parties (like the architect and owner's rep), there are over 50 people involved in this one-day amalgamation of man and machine.
By 3 a.m. the work has turned into an assembly line process. The drivers are comfortable with their path of travel. The target of 150 cubic yards per hour has been achieved and there is around 300 yards on the ground. But there's still a long night ahead, with 367 cubic yards left to pour.
The home stretch
If things seem to have reached a controlled lull on the jobsite, back at Norcal Readymix, it's anything but peaceful. A loader operator has been hustling all night to keep the plant stocked with course and fine aggregate fed by a constant stream of bottom dump aggregate trucks. Drivers have been pushed to their maximum abilities to coordinate everything and get their trucks under the batch plant in a timely manner. Norcal's dry mix plant takes a little over three minutes to batch a load. Spot lights glare, mixers wind loudly receiving their loads; the scene is veiled by a hazy cloud of cement dust. With so many mixers jockeying for position and the batch plant located over 20 minutes away from the jobsite, time is of the essence.
At 4:30 a.m., Tomas directs his finishers to fire up the gigantic riding trowels—it's time to start the finishing. The equipment is spotless as a heavy-duty mini crane drops the riding trowels onto the newly hardened slab. The engines ignite and the pan blade discs begin to rotate, knocking down any ridges that may have eluded the laser. Soon another rider, this one with finishing blades, will follow. When the process is complete, in about eight hours, the slab will shine like black glass. Everyone on the site is glad to see the riders—their swirling rotations signal the beginning of the end. Tomas nods to his lead finisher that the concrete is behaving as it should.
It's a little after 7 a.m. and early morning traffic starts to clog Highway 101. The cleanup load has been placed and the pour is complete. Norcal has delivered the entire 667 cubic yards of concrete. The riding trowels are a blur of energy, slipping and sliding back and forth across the newborn slab. The entire 42,000 square feet of slab on grade has been placed in one night.
Bill Coleman and Rick Freeman survey the scene with pride. But they can't be too content. They have to start locating the side forms for the tilt-up concrete panels. The clock is still ticking.
— Bryan Schwab is an estimator/project manager with over 30 years experience in concrete production, pumping, and general contracting.