In terms of the history of cement, it is generally accepted that the Romans were the inventors of the closest version of what we now call "cement" in about 200 BC. By mixing slaked lime, volcanic ash and water, the Romans produced a product that gave remarkable durability and a high degree of strength.
The Colosseum, the Basilica of Constantine, and the Roman baths, built all around their empire, are examples of early Roman architecture that has stood the test of time.
Scientists at the Australian Nuclear Science and Technology Organisation (ANSTO) have been looking at this remarkable durability even going as far as examining Roman cement that is 1700 years old. Modern cement was first formulated in the early 1800s and since then it has been used in just about every building application imaginable, including shipbuilding.
In fact over 90 per cent of the cement produced worldwide is what is known as "Portland cement." Although its use has been ubiquitous, we still dont know how the cement gel is put together. Most molecules form in crystalline shapes where every atom has its place and this order is used by x-rays to show how the molecules are put together. But molecules like cement gels are amorphous and scientists havent been able to tell how the atoms came together - that is, until now.
Using x-ray diffraction, thermal analysis and nuclear magnetic resonance spectroscopy, University of Technology, Sydney (UTS) scientists Dr Danielle Klimesch and Associate Professor Abhi Ray, in collaboration with ANSTO, have found that the structure of cement on a molecular level is not exactly what it was originally thought to be. One of the standard tricks in cement chemistry has been to heat cement paste in a pressure cooker to make ordered compounds.
The reaction of the alumina in these pastes was found by the UTS scientists to be incorrect. Other PhD scholars from UTS, Vanessa Peterson and Michael Prior, are now using the neutron scattering equipment at ANSTO's HIFAR research reactor to further develop the techniques for characterising amorphous materials.
The scientists are confident that the new molecular modelling packages, whe used with these results and new results to be taken from ANSTOs replacement research reactor, will reveal the structure of cement pastes. So although the "holy grail" of the structure of cement gels still eludes us, ANSTO scientists say with some confidence that once we know the nanochemistry of cement, it will beonly a matter of time before we finally unlock the secrets of one of our most commonly-used materials.