Concrete

concrete Concrete is all around us, everywhere you look. It is one of the most abundant and economical structural materials in the world. Concrete is a masonry product composed of cement, sand and gravel or other coarse aggregate. When water is mixed in with concrete, it activates the cement component, which is the element responsible for binding the mix together to form one solid object.

http://fc04.deviantart.com/fs18/f/2007/176/8/0/Texture__Concrete_Cracked_by_ivelt_resources.jpg

history The ancient Romans first used lime and pozzolana, a volcanic ash, to create a hard setting mortar. By adding rubble and other aggregate, the Romans created opus caementitium. The most famous example of this early form of concrete is the Pantheon in Rome, Italy. Modern concrete was invented by the British engineer John Smeaton in 18th century, alongside the rapidly growing use of iron and steel for building construction. Portland Cement, the main ingredient in modern concrete, was patented in 1824 by Joseph Aspdin. In the 1867 Frenchman Joseph Monier combined the tensile strength of steel and the compressional strength of concrete to create the composite building material known as reinforced concrete. Today, nearly all concrete construction is reinforced concrete.

1

http://www.znanje.org/i/i27/07iv03/07iv0321/pantheon.jpg

1. Roman Pantheon, early example of concrete 2. Concrete slab showing basic steel reinforcement 3. Portland Cement, key ingredient in concrete

http://www.momahoney.com/M.O%27MahoneyCo%20File/Images/MOMSupplies/Ce-

3

http://www.dkimages.com/discover/previews/884/5019427.JPG

2

types Concrete is available in 3 main types. The most common is ready-mix concrete, which accounts for more than threefourths of all concrete construction. Ready mix concrete is mixed off site at a central plant and shipped to the construction site in large trucks. Another type is Pre-cast concrete, which has become widely popular especially in hotels and apartments where repetitive elements are common. Pre-cast concrete is mixed and cured at the factory under ideal conditions, producing a higher quality concrete. The last form of concrete is the concrete masonry unit, which in best known for its standard 8x8x16 inch block. Because they are cured in the factory, they can be mass produced and designed to suit any architectural need.

http://upload.wikimedia.org/wikipedia/commons/5/58/Concrete_pouring_0020.jpg

1

http://www.prestasi-concrete.com/images/M2(small).JPG

2

1. concstruction crew pouring cast in place foundation 2. prefabricated concrete beams 3. concrete masonry units, curing in the factory yard

http://www.wizzard.com/bm2004/Images/event_jill/big/07390016.jpg

3

thin shell design Some of the most innovative uses of concrete appear when architects and engineers are able employ complex geometric shapes in their building design.

L’Oceanogràfic Heben Etrum vocchus antin patur in din aurorudella vivas citam sent. Deffre, ces vit, cons autuit inatus. Nosus imus sentifecest? quidet ime pota ta, oca notanum hacto morti, que fitum moveheb untimil hoculud eperum dum inereis vehebut parivit. etistrum. Licus, nihin veridet; Catui cupios, cuspicibus effretorum intea iu iaela es a consum aut potero areis Mulin hilinemusRes portiurs faus se ducta confina, vit, es sederi sceps, C. Si in vivirtem tandam iustrestre, quemoribunum a publice natium tam esidio ve, quodienatus simusci virit; non audam cem, ta L. Agilin se ina, C. At patur labit, quast orestid nit. Ces norte, Palica; itus rentem egilis ervivid eponfirit. Bonsusulius prisquam conosse moruntem querem occhuit, cae, norem ut ingulto ritatum hemus, te tereheb unclesc ienis; etimus publica rehebus cerum novero Catum ad sus at, condam forum, sulti, cepere facerdii is lissu que consularis, quam tem por prorebermis habunum sa iam ubliumedes pulto tante mei per ad nocrem peris. Ad menic in tantienatim me publis faciistrum te, nes vit fendac ta probse quis, etorebatis; num inatum. Seri, tata, publica mo ta, fex mo Catiumena, noruntil ut adhuciaet vicit, P. Ego huidin hacerei publis cas pro, niam publiquem in scero mendenium estraequam ine es cont.

http://www.fundacioncac.es/cas/artesyciencias/mediateca/download/20049913856o-2178dig_jft.jpg

http://www.panoramio.com/photos/original/678558.jpg

dulles international airport

http://farm1.static.flickr.com/69/162370394_0c8251d3a5.jpg?v=0

Alisit dunt et volenibh exer sent lortis eliquisci exerati onsent nullutatue feu feum nullamcons erciduis num velenibh et aliquis et volesse quipis essi. Ud el ing et iriustrud diat augait eum vero dui el et, veniam vel ulput wiscidunt alit lumsan ver iustin heniscidunt vendrer cillutate dip essequam delendit prat, conulla faci ea aliquis dolorper si. Vendipi ssequis augueri ustrud ming ea feuguerosto commy nulla conse min utpatum modolorperit lutat. Ectetum sandreetue veratie feu feugait la core volum dolore delis nim dipit voloborting eum dolore dio ent er susto commodigna facilla mconsed do dunt wisl dio delis nis dolorper am num nostrud dolore delit, vulputat aut velit lor sustis essi. Or ipit in enit atinism olorer irilit landrerit, consed ea faccum zzrilla commy nullupt atueriure feugiam consenis augiam, commy nisci bla consequ ismodolor sustisc ilisis nim veros delit utpatem venibh ero delesecte te vulputatem nim amet, commodolor iliquip enibh ecte feuissi. Na corem vel ut ullum do duis nullum niscillutat nonsent velisci psusto etue min vent dolore duip eu feuipit vel dunt laore conullum aliquisit adit prat, conulput wis aut inim dit luptate eniam velent eugue vel dio odo dip eummy nit er augiam, cor si. Onsed minibh eu faccum velenis nostinim quis autet, quissed tat, sis ad ea commodignim nummy nostin ut alit do odit lam zzrilit ut atue dolutetum nim eum zzrit, se molore el ulla facilit dignisit lute diatet augueriure veniamet, vullaore dolorem quat, quat nonse do conse dolummo digniam consequatue eu facip eui tie euisci esto conum voloreet laor in euipsusto do dolum dolor sequisc iliquis exero od estrud tat. Agnim veros et lortincillan ulput autat dolorercinim zzriliquat

thin shell cave Our first large scale plaster model was inspired by the American Air Museum in Duxford, England (page X). This model is approx. 30” x 24” x 12”. We encountered several problems with this project. Despite being only 1/8” thick at the top, this model required nearly half a gallon of plaster. Managing large quantities of wet plaster proved to be challenging, and we were forced to pour several batches. Creating accurate formwork for complex geometric shapes also proved to be quite a challenge. The American Air Museum is based off a tourus, or 3D doughnut, producing a non-deformable section that is curved in two directions, which we were unable to replicate. Despite this setback, our “cave” is remarkably strong, so long as the outward thrusts of the abbutments are resisted. 2

1

3

1. Thin shell cave with plexiglass formwork half removed. 2. Perspective image of the cave. 3. Detail of cave abbutment and wire screen reinforcement. 4. Side elevation, showing straight edge instead of doubly curved shell.

4

precast "tee" beams An important structural feature of the American Air Museum is the precast concrete "tee" beams that form the curved roof. Despite the complex geometry of the building, the concrete manufacturers were able to cast the 200+ beams required with only six different sets of steel formwork. We were able to approximate one of these sets of formwork and use it to cast two identical tee beams at 1:50 scale (8" x 2" x 1"). Instead of steel, we used wood faced with plexiglass to make our molds. Once assembled with masking tape, plaster was poured into one end of the mold and allowed to cure fully before striking the mold and repeating the process.

1

2

3

1. Formwork pieces laid out 2. Formwork partially assembled 3. Detail of lateral reinforcing wires. 4. Finished "tee" beams.

4

1 part sand aggregate

2 part sand aggregate

3 part sand aggregate

4 part sand aggregate

reinforced plaster We tried several methods of reinforcing our plaster. In our first attempt, we used medical guaze. The plaster seemed to have a negative reaction to it, perhaps due to some coating on the gauze. It was difficult to make the plaster adhear well to the fibers, although once it cured, the gauze was able to hold the plaster together even after complete failure. The randomly oriented fiber strands produced a very strong slab, due mostly to the thickness and density of the fibers. This thickness however prevented us from producing a slab less than a quarter inch thick. In our third experiment, we used a wire screen to reinforce the plaster on our thin shell cave. The metal screen prevents tensile forces from cracking the thin plaster. 1

2

1. Medical gauze 2.. Randomly orriented fiber strands 3. Wire screen

3