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Sticky Rice Is the Key To Super Strong Mortar 194

Posted by timothy
from the what-can't-sticky-rice-do? dept.
lilbridge writes "For over 1,500 years the Chinese have been using sticky rice as an ingredient in mortar, which has resulted in super strong buildings, many of which are still standing after hundreds of years. Scientists have been studying the sticky rice and lime mortar to unlock the secrets of its strength, and have just determined the secret ingredient that makes the mortar more stable and stronger. The scientists have also concluded that this mixture is the most appropriate for restoration of ancient and historic buildings, which means it is probably also appropriate for new construction as well."
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Sticky Rice Is the Key To Super Strong Mortar

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  • Amylopectin (Score:5, Informative)

    by Verdatum (1257828) on Wednesday June 02, 2010 @04:12PM (#32436620)
    I didn't know the critical ingredient was a mystery. Alton Brown from Good Eats explained the molecule quite well in the rice episode, and my immediate thought was "oh that must be why it was used in mortar for the Great Wall and such."
  • by Chris Mattern (191822) on Wednesday June 02, 2010 @04:21PM (#32436754)

    There are people who know how to do concrete right. And then there are people who know how to do concrete cheap.

  • by somersault (912633) on Wednesday June 02, 2010 @04:26PM (#32436804) Homepage Journal

    China probably does.. I mean sure it has a billion people, but apparently it produces 25% of the world's rice.

  • Re:Two more (Score:3, Informative)

    by mcgrew (92797) * on Wednesday June 02, 2010 @04:37PM (#32436946) Homepage Journal

    Or potatos. Do NOT put potatos down your garbage disposal; I found that out the hard way. Had to rent an electric plumber's snake to unplug the damned drain. The disposal has no problems, it's after they go down the drain and harden.

  • by EggyToast (858951) on Wednesday June 02, 2010 @04:40PM (#32436992) Homepage
    This isn't concrete -- it's lime mortar (which isn't used anymore). This is just a very hard lime mortar due to the additives -- it doesn't give any strength comparisons to portland cement. I imagine it's significantly less strong, though, despite the headline. This is "super strong" compared to plain ol' lime mortar.
  • Re:Amylopectin (Score:5, Informative)

    by EggyToast (858951) on Wednesday June 02, 2010 @04:53PM (#32437166) Homepage
    Thing is, lime mortar hasn't really been used for about 150 years, so there's no research into it for modern building applications. Since OPC is better in every regard, including strength, repairing old lime mortar hasn't really been of concern until recently, when there's been more of a push to accurately repair historical buildings and structures. However, you're not exactly right with the Great Wall -- it was built 2200 years ago, whereas TFA notes that this particular process was done 1500 years ago.

    Still, I imagine this was also prevalent in Pre-Columbian architecture too, only with corn. Boil the corn, then use the leftover water.
  • Re:Amylopectin (Score:5, Informative)

    by rritterson (588983) on Wednesday June 02, 2010 @04:53PM (#32437170)

    From reading the physorg summary linked in the article linked in the summary on Slashdot (why we have to link to tertiary sources, I don't know) it seems that it isn't the polymer branching of the molecule that lends the mortar strength- the amylopectin doesn't even directly add strength as far as I can tell. Instead, it's that the amylopectin breaks up the crystallization of the lime in the mortar, creating micro crystals instead. I can imagine a big crystal being quite brittle with all of the possible shear planes.

    So, it wasn't as obvious to me why the amylopectin made it stronger.

  • Re:Two more (Score:5, Informative)

    by IndustrialComplex (975015) on Wednesday June 02, 2010 @04:59PM (#32437230)

    Or potatos. Do NOT put potatos down your garbage disposal; I found that out the hard way. Had to rent an electric plumber's snake to unplug the damned drain. The disposal has no problems, it's after they go down the drain and harden.

    It's ok Dan, you can use 'Es' this time.

    But on a serious note, you were essentially putting one half of a binary glue down your drain. The other part of that binary product is water which your disposal kindly mixed for you.

    http://en.wikipedia.org/wiki/Wheatpaste [wikipedia.org]

  • by Threni (635302) on Wednesday June 02, 2010 @05:13PM (#32437390)

    You're wrong, I'm afraid. Although the rice used in Sushi is sticky, it's not what is generally called sticky/glutinous rice. Sticky rice is used in various Asian, especially Thai dishes, either with savoury food like pork, or as a dessert with fruit such as with mango or durian, and salty coconut milk.

  • by need4mospd (1146215) on Wednesday June 02, 2010 @05:19PM (#32437460)

    It's the iron inside the concrete that contributes to its decay, because the metal expands and contracts with seasonal changes in temperature.

    Uh, so does concrete. Actually, they expand and contract at nearly the same exact rate depending on the composition of the steel and concrete. Without the steel you'd need a ridiculous amount of concrete to make up for it because concrete has a lower tensile strength. Adding enough concrete to make it work properly would make concrete structures very bulky and would limit their height considerably.

    (Hence why the Romans' stuff is still around.)

    The Roman stuff is still around because it was VERY thick, not because it didn't have steel. It probably would be in significantly better shape if they used steel.

  • Re:US Homes (Score:3, Informative)

    by cowscows (103644) on Wednesday June 02, 2010 @05:30PM (#32437608) Journal

    It is extremely rare these days to build a building with load-bearing brick walls. To go up more than a couple stories, the walls end up being ridiculously thick, and as a result ridiculously heavy. So you end up not just paying for lots more brick, but also for a much more serious foundation. Your labor costs also go way up, because bricklaying is time consuming, and harder to do well than you might think.

    Most brick buildings are just a veneer, whether they're over concrete, steel, or wood. Wood is actually one of the hardest to do, because the wood tends to shrink over time while the brick tends to expand due to heat and moisture. The brick is tied back to the wood pretty regularly, so these changes can cause serious cracking if you don't design for it.

  • by need4mospd (1146215) on Wednesday June 02, 2010 @05:57PM (#32437918)

    "Nearly" is the operative word here. Repeat a 'near' difference 2000 times and tell me how inconsequential it is, especially when it comes to shifting the weight of a structure over and over again.

    That's not really how it works. After the concrete cures the concrete and steel are at a sort of equilibrium. Whenever the structure is at or close to that temperature, everything is peachy. It's at extreme temperatures when you start to see expansion(or contraction). The coefficient of thermal expansion for concrete and steel are not only very close, they are extremely low. Meaning you'd need un-earthly variations before you'd see any detectable amount of variation.

  • by camperdave (969942) on Wednesday June 02, 2010 @06:09PM (#32438062) Journal
    People go hungry due to politics and poor distribution, not overall quantity of food.

    Actually, we have the capacity to deal with poor distribution as well, so it all boils down to politics. Someone is deciding that people should starve to death.
  • Re:Amylopectin (Score:2, Informative)

    by serbanp (139486) on Wednesday June 02, 2010 @06:35PM (#32438336)

    However, you're not exactly right with the Great Wall -- it was built 2200 years ago, whereas TFA notes that this particular process was done 1500 years ago. .

    ugh, the Great Wall was nominally finished during the Ming dynasty, in the 1400s. Unlike the oldest sections, built with rammed soil and stone, the more modern parts did use bricks and mortar.

  • by John Hasler (414242) on Wednesday June 02, 2010 @06:47PM (#32438432) Homepage

    > This is why they will throw crappy, rusted rebar into the mix, as it won't
    > matter as soon as it sets up.

    They use rusty rebar intentionally. Concrete bonds well to rusty steel.

  • Re:Two more (Score:5, Informative)

    by eclectus (209883) on Wednesday June 02, 2010 @07:26PM (#32438814) Homepage

    The 'feeding rice to birds will make them swell up & explode' is a myth. snopes even says so.

    http://www.snopes.com/critters/crusader/birdrice.asp [snopes.com]

  • Re:Amylopectin (Score:1, Informative)

    by Anonymous Coward on Wednesday June 02, 2010 @07:36PM (#32438910)

    The Great Wall of China is a wreck. The bit you see in photos is the bit that was rebuilt in the 50s. The rest of it looks as old as it is.

  • by rahvin112 (446269) on Thursday June 03, 2010 @02:28AM (#32441404)

    Epoxy coating the re-bar has not been proven effective. What the masons you had a beer with is typical of the trades, they don't understand the big picture because they are focused on their job. No engineers or architects screwed up (other than the very few public examples of failure). Buildings are designed for a certain life, typically that's 50-70 years and after that the building is expected to need capital investment in the infrastructure beyond routine maintenance to extend that life. Buildings could easily be designed to last longer but the longer the life the higher the cost and it's rare for an owner to care. Buildings could easily be designed to take fires, earthquakes, tornado's and hurricanes but the costs of such design make it illogical.

    The masons you mentioned talked about paint, it's not paint it's epoxy and it's a highly unproven technology (unless you are talking to the epoxy association, then it's the end all be all of re-bar protection). There are some in the engineering sector that think Epoxy coating re-bar is going to be one of those big mistakes that comes back and haunts us endlessly in a few decades (epoxy coated steel has been in use since the late 80's). The thing is concrete by itself is highly alkaline, the steel itself is alkaline as well and this prevents corrosion (which needs acidic environments to thrive, remember it's an oxidation process). The problem with epoxy is it negates the alkalinity effect of the concrete. In a perfect world the epoxy would be clean and perfect after the concrete sets but in reality the epoxy is going to have abrasions and cuts from erection, pouring and finishing (not counting what a decade of thermal expansion does to it). These abrasions in the epoxy coat provide a path of corrosion and once it penetrates the abrasion and infects the steel it can move along the steel much quicker because of the epoxy coat protecting the corrosion from alkalinity of the concrete. IMO a much better solution is galvanizing, the zinc coating has an additional alkaline protection and is much more durable during construction than epoxy ever can be. Either that or use high ksi stainless steel.

    Boston is not alone in problems with re-bar corrosion, the issue involves the use of salt, cities and states that use salt in the winter on the roads, the salt provides the corrosion path and negates the alkalinity resulting in corrosion way ahead of schedule. The salt on the road moves through the environment and affects lots of ancillary structures including nearby buildings and tunnels. Black-bar re-bar used in concrete where salt isn't applied, even underwater and in freeze/thaw cycles has been very durable. There is reinforced concrete out there that is still in perfect shape that was poured 50 years ago and it's harder than ever.

    Also, all concrete sets underwater, concrete doesn't dry, it hardens, it is a chemical reaction that involves hydration and the formation of a crystalline structure using the water. Without water there isn't concrete or if you allow the concrete to "dry" before it sets will degrade the concrete severely. This is why they have to keep the concrete moist for several days after pouring. Premature drying has similar symptoms to over-finishing, the surface of the concrete spalls the top surface off after a time rusulting in the loss of about a 1/4 - 1 inch of concrete on the surface spalling off.

    And finally, organic additives to concrete are NEVER a good thing. Organics deteriorate after time, this leaves voids in the concrete where the organics ended up and the decay can create acids and bases that can adversely affect the concrete. Organics are bad, period. Now, Roman use of organics, such as blood may have resulted in more air-entrainment. The little tiny air-bubbles formed after the organics decayed (or as a result of mixing them in) would have provided freeze-thaw protection. Concrete placed in the open weather typically needs ~5% air entrainment to eliminate the effect of water saturation and freeze/thaw cycles. The heavy use of

  • Re:Two more (Score:2, Informative)

    by DMUTPeregrine (612791) on Thursday June 03, 2010 @03:17AM (#32441638) Journal
    Bird feed often contains sunflower seeds and other seeds with higher fat and protein content. Birds like that more.

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