Sticky Rice Is the Key To Super Strong Mortar

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."

Comments

The romans build concrete buildings

[Colin Smith]

Many of which are still standing, 2000 years later.

I predict the common factor may be the concrete.

hth.

Re:The romans build concrete buildings

[ElectricTurtle]

You're sure there's no rebar, no iron at all? I doubt it. It's the iron inside the concrete that contributes to its decay, because the metal expands and contracts with seasonal changes in temperature. Concrete without iron in it may be structurally weaker, but it will last a lot longer if kept within proper parameters for loads. (Hence why the Romans' stuff is still around.)

Re:The romans build concrete buildings

[SgtChaireBourne]

One additive that gives strength to concrete the Roman built with is blood. It doesn't have to be human blood. Funny how the quality of concrete and steel deteriorated during the period 1200 - 1500. I wonder what could have been going on in Europe then. ;) Blood still works well, but does tend to tint the material pinkish or reddish for a long time.

Re:The romans build concrete buildings

[Maxo-Texas]

It wasn't until the 80's or 90's that romans use of fly ash became common knowledge. Back in the 70's, roman concrete was still in the "ancient mysteries" column.

Re:The romans build concrete buildings

[ShakaUVM]

Eh, I thought the secret ingredient in Roman concrete was volcanic ash? When medieval people elsewhere tried making concrete to the ancient specifications, they ended up with some watery messes and gave up on the whole thing for centuries.

Re:The romans build concrete buildings

[Anonymous Coward]

Just a piece of concrete-nerd pedantry: The Romans didn't use fly ash - that comes from coal-fired electricity generation, which I'm reasonably sure they hadn't invented yet. It was volcanic ash, "pozzolana". Similar chemistry, but made in a volcano instead of a coal boiler.

sounds like a job for the MythBusters!

[Joe The Dragon]

sounds like a job for the MythBusters!

Re:Two more

[timeOday]

Rice is pretty strong. My wife once dumped a partially-cooked pot of rice down the kitchen sink, where it proceeded to swell up to an impenetrable clog. Being a fool, I got a plunger and just kept at it with increasing force until the all the water (and drano) that had pooled up, suddenly went right down the drain - and straight into the cupboard, because I'd knocked the rice-cemented plumbing right off the bottom of the sink.

Strong doesn't mean good, and rebar as a flaw

[drwho]

Mortar that's too strong is brittle, meaning it can easily crack. Rebar can rust and swell, breaking this brittle cement. The result is catastrophic. I learned this from a couple of masons who I was drinking with at a pub. They joke that because of some really bad decisions made by architects and structural engineers in the 1960s and 1970s, they have good job security. I had known from reading books on restoring historical masonry buildings (thanks Ian Cramb) that strong mortar such as portland cement and other more modern mixes are just too brittle to be used as mortar. Stones and bricks shift ever so slightly as they settle. This can cause cracks, large or small, in the brittle mortar, that wouldn't happen with a weak lime mortar. These cracks are the widened by water freezing and thawing, and sometimes plant life. But what my bar buddies told me is that what makes the problem even worse is the rebar used in concrete buildings until recently would slowly rust and swell, so the masonry would burst from the inside because it was so brittle. These mason fellows would chip out the remaining concrete or cement, clean and coat the rebar (but sometimes replacing it) with a protecting paint, and then re-apply cement or concrete. I've noticed this problem occuring in many places, such as subway stations and bridges in the Boston area. I have no reason to believe the problem is limited to this city.

Regarding Roman cements and concrete: pozzolana, otherwise known as hydraulic cement, was a mixture containing volcanic ash, specifically from mount Vensuvius. It has the ability to dry and set underwater. This 'secret' is said by many to have been lost for many centuries, but in fact was kept a 'masonic secret' by some masonic guilds for a long time. Yet the exact nature of this secret and its revelation are hazy.

Yes, blood was used as an ad-mixture to some Roman cements. I can't remember what benefit it added.

Some places add organic material to concrete, with a variety of results. Done correctly, it increases the strength of concrete. Done badly, it's a recepie for disaster. Using straw is certainly bad, but evidently hemp and possibly other materials can be used. Exactly what works under given conditions is not known to me. It may be another one of the 'masonic' secrets.