Ferrocement Photo Gallery

Ferrocement Photos

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Photo 271696 viewsBelow is the mix low down, and above is another view of work in progress. After completion I wet cured the steps for a full 30 days before use. A temporary ramp with barriers protected the steps from all use. The steps were covered with plastic sheet and plywood mockup cutouts. The work was also tented tightly in 6 mil plastic sheet with 2 large shallow water filled plastic cement mixing tubs placed inside to keep the air humidity high for 30 days. The weather was Southern California December, 52-60 degrees F shaded from sunlight by the house eves and surrounding trees for great slow sets and a long, strong cure.ECC MIX MATERIALS:
1) Graded feldspar silica blasting sand, bagged and dry mixed in nearly equal portions by weight: #16, # 20, #30, #60, #90, #120 grit
2) Portland cement, low alkali, type II/V
3) 100% Acryl 60 (no water)
4) PVA (Poly Vinyl Alcohol) REC15 fibers 1/4" grid woven wire steel mesh (M/Steel, 4 X 4, 1.190 wire, roll 36"W x 111'L)MIX RATIOS BY WEIGHT:
The first batch was weighed with a scale in ounces, each separate ingredient placed on the scale in plastic Straus brand yogurt containers: 317 oz sand (combined weights), 60 oz cement, 4 to 7 oz PVA fibers (under 2% by weight), 19 oz Acryl 60 or more but kept to the bare minimum possible except in the batches being pushed into the interior of the space frames.
MIX RATIOS BY VOLUME: The weights chosen closely resemble the volume ratio of 1:3 cement/sand.MIX TOOLS:
A) Milwaukee heavy duty 1/2" angle drive drill, 4.5 amps, 0-500 rpm
B) Onebone style mixer, homemade, metal blades on all-thread
C) 5 gallon plastic buckets, half filledMIX METHOD:
The dry mix was given a short stir with the Onebone mixer, the liquid was immediately added, and all mixed for 30 to 60 seconds at 150 to 300 RPM.SET CONTROL:
Cool days and the Acyrl 60 gave us an hour to apply each batch of mix as long as it was spread out and not massed in any container where chemical reaction heat could accelerate the set. (Each stair step took 4 to 6 buckets half filled.)BUBBLES: Slow rising air bubbles were a problem if the surface was float-troweled too long. The Acryl 60 did not let bubbles rise and dissipate easily. Various vibration techniques were briefly tried but not liked. Short slow power mixing, the no-air-encapsulation mud application technique previously mentioned, and a quick and efficient trowel finish on the top were the answers to bubble potential. "Johnny, don't play with your potatoes!"
Photo 291608 viewsThe goal was to create a simple, modern, and clean looking stairway. Curved and cantilevered, floating effortlessly, goal achieved.
Photo 281578 viewsThe stairway is complete but it's good to keep a perspective. It's just another day in the life with Willie, and Willie knows what's important.
Photo 261368 viewsDoes this look like bliss or purgatory? I was singing and soaring withnature's forces.
Photo 231354 viewsHere's the nitty gritty. This was the biggest bear to fight, getting the mudinto the mesh without voids. On a hunch I stopped by the local OSH hardwarestore and purchased toilet plungers to force the ECC mud. ...Any trick inthe book and then some. While holding four of them in my arms in theshopping isle, the guy next to me commented on the plumbing problem I musthave. He was a concrete engineer and we talked for an hour. He approved ofmy 'manual hydraulic mortar emplacement tool'. I'll explain how one must'roll' the mud into place to avoid voids. I learned it decades ago in dentallab on the plaster bench. Like a slow motion tsunami wave you push orvibrate the wet material outward directionally, never gulping air, neverencapsulating air or creating bubbles. You watch the leading edge of your'wave' as it consumes everything in it's path in slow-mo. Doing this with atoilet plunger was a new wrinkle. The 3 sizes of trowels were helpful butcouldn't generate the pressure needed to get the mud thoroughly through thewire mesh and protruding out below, like a meat grinder making hamburger. Weare talking about very physical work here. Given the time constraints ofinitial set, we really put our weight into the job. When satisfied withpenetration we then plopped on a mound of mud and spread it out on top,level with the aluminum angle forms. Last I floated a smooth finish andcrawled under the step to begin smoothing out the bottom. We are talking areal hump job here, given the time constraints of the setting ECC mortar. Ithelps that we had three of us, one continually mixing small batches, and twoothers schmushing and finishing. Also the days were cool, slowing the set.
Photo 211314 viewsPictured from the left is myself and my son Dan. We have just completed thelast step. In work sequence I chose to mud the bottom step first, then startfrom the top and work down, because the bottom step appeared most forgivingfor the learning curve. We were using untried PVA rec15 fibers in our mix,pushing this through layers of 1/4" woven wire steel mesh, a potentialnightmare. The lowest step is the easiest to reach, rests firmly on anon-flexing concrete foundation, is small in volume, and has a minimum ofunderside to hand finish. The other four are flexible, larger, and have alot of underside to finish. To begin with I wanted the best chance to adjustour mix and application methods, and clock the application time beforetackling the more critical stair steps.
Photo 221299 viewsTalk about getting 'at one' with the work, I'm 'into it'. Notice thealuminum angle as edge forms for crisp corners. You can get away with lessprecision if you somehow strike clean edge lines on your work. The angle iswaxed and then tie-wired in place to the mesh, to be removed after ECCplacement and cure. Notice how they hang loose until packed with ECC. That'sto give the precise space for the ECC to cover the mesh. You can see plasticsheeting under the plywood, it's covering the exposed mesh to slow therusting in the rains we had been having. I used that plastic later to coverour newly troweled ECC steps too. I didn't want plywood to sit on the curingECC sucking moisture. The pipe plug is protecting the threaded stainlesscoupling inside the ECC. That coupling is the means of attachment for ahandrail should one be desired. The clamps are holding more aluminum angleserving as crisp forms where mud will meet the steel plate brackets.
Photo 241286 viewsLook for the pasty yellow looking thing under the step, that's my armworking from below. I spent more time below than above because there wasmore surface area to finish, and it wasn't flat work, but rather on-my-backconvex and curvilinear finished surfaces. Did I mention that each step tookhalf a day to mud, including cleanup? If this were sprayed into a mold itwould have been a half hour.
Photo 201233 viewsIt's time for mud! Looking from atop the stairs we see the bottom step hasalready been completed in ECC, or Engineered Cementitious Composite. I callit mud. The step hides the little concrete foundation under it. I'lldescribe the particulars of this mud process with this series ofphotographs. We see the top step uncovered and ready for ECC mortarapplication. The three middle steps have their temporary plywood covers onthem, also ready for ECC. Up to now people have been using the stepsincomplete with plywood, but as we apply ECC to these steps we can't riskanyone sneaking on them and vibrating the curing ECC...not for 30 days! Wewill build a ramp that clear-spans the steps and blocks any other passage,be it human or pet. There is no photograph of the built ramp but it wasbasically green Astroturf covering plywood, 11 feet long, with pipe clampsfashioned as 'handrails'. Ugly but sturdy. It took a full day to engineer,purchase materials for, and build. The ramp had to be removed each day thatwe worked. Each stair step took half a day to float including clean up.there is good argument for designing mud application to be done in-shop, butthe client didn't want to see bolts under the stairs. 'Clean' is notnecessarily easy...
Photo 011210 viewsThis particular little stair design is about a marriage of 1/2" steel plate and 8" diameter pipe to ferro cement treads in a live loading situation. There are easier choices in materials and methods for this situation but I wanted to test this combination out of curiosity regarding future projects. As people walk on these stairs the loading of the cantilevers asks the materials including the mechanical joint between steel plate and ferro cement to perform reliably in tension, compression, and for extra fun, torque. I didn't create molds for this job because this is a 'one off' project and each stair step is shaped differently. Using molds in a slightly different application would have been the better way to go for efficiency, labor savings, structural quality, and surface treatment. In the past I've cast metal structural frames into molds in a variety of venues from partial acrylic/ dentures and crowns/bridges in dental lab prosthesis to hidden epoxy 'belly boards' for 'flying' Superman patrons (hydraulically) at Universal Studios. These are similarly continuous live loaded appliances using metal frames molded into a plastic medium. This particular ferro cement stairway project proved to be intense in labor, but 5 molds would have been another major fabrication step for a stairway made exclusively for one site. I will reserve molding FC onto metal for similar but far larger projects. Anyway, I wanted to re-experience the pain and agony of wiring mesh, pushing mud into it, this time with PVA fibers in the mix.
Photo 251175 viewsThe most spiritual part of the job was in smoothing out the convex cuppedlooking areas underneath each step, largely hidden from view. Because of thelittle rod trusses previously mentioned, each step had regularly spacedbumps under them to deal with. They created little convexities between them.I grabbed the smooth Mexican beach pebbles you see as shaping and smoothingtools. I quickly began hearing surf sounds in my head, while slurping andsliding, and gliding the smooth rock over wet mud. An occasional spritzingwith the water spray bottle lubed the process. I began connecting sculpturalshaping with nature's forces, feeling like a magnetism was pushing my hand.I also realized I had been under the steps too long and had a long way togo. Go with the flow I say. I began singing.
Photo 091147 viewsI liked the frame with the rust on it before sandblasting. Next step is powder coating. The client wanted it a gray cement color. This is a project about projecting modern clean lines, restraint, and simplicity through illusion, smoke, and mirrors. We are making magic.
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