Sep 29 2014
Researchers have developed a new method to manufacture cement that is greener and stronger. Concrete is widely used as a construction material and is significant contributor of greenhouse-gas emissions leading to global warming.
The method developed by a collaborative group of researchers from the Massachusetts Institute of Technology in USA and the CNRS in France involves comprehensive molecular analysis of concrete, and this has led to the discovery of a magical calcium-to-silica ratio that delivers outstanding properties.
Concrete is made up of gravel, sand, cement and water. In order to manufacture cement, the typical process involves using a material rich in calcium and a material rich in silica, which are blended together at a high 1500°C temperature. This results in clinker, which is ground to form cement. Typically limestone and clay are used. The heating process, as well as, limestone’s decarbonation is the main contributors of greenhouse-gas. However, cement is necessary for a wide range of applications, as it can turn from liquid to solid state within 10h at room temperature.
Roland Pellenq, an MIT senior research scientist, states that traditionally, the calcium-to-silica ratio used ranged from 1.2 to 2.2. The standard ratio used is 1.7. When analysis of the molecular structure was performed, they discovered that a calcium-to-silica ratio of 1.5 had amazing properties. At this ratio, along with some design on the molecular-scale, the material demonstrated twice the amount of mechanical resistance when compared to normal cement. The material became more glassy and fracture-resistant and less crystalline as there were no residual stresses.
Reduction in calcium content usage will contribute to reduction in carbon emissions, which may be as high as 60%. Further, the increase in resistance to mechanical stress will be beneficial for well casing applications in the oil and gas industries.
The researchers now intend to perform the same analysis on the mesoscale so as to derive benefits for other applications.
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