Bioglycerol, or crude glycerol, is impure glycerol obtained as a by-product in the biodiesel industry. Researchers now show that it is possible to employ bioglycerol as a multipurpose grinding additive for the manufacture of cement, with better performance than pure glycerol.
Cements with bioglycerol are produced with lower energy consumption and the finished concrete structures have significantly better mechanical properties and corrosion resistance.
How will this new discovery impact the environment – and the construction industry?
The Impact on the Environment of the Construction Industry
The construction industry has a huge impact on the environment.
Considering the use of natural resources, for instance, data indicate that almost a quarter of the raw materials extracted from the lithosphere are employed in construction.
The manufacture of cement is one of the most environmentally impacting of mankind’s activities. The cement fabrication process requires heating the cement components (i.e. limestone, clay, sand, etc.) at no less than 1600 oC for the “clinker” mixture to be formed. Further energy is then required to grind the clinker into a fine powder, and for the cooling process. Overall, the calcination and grinding processes account for 80% of energy consumption, while power for the cooler accounts for the remaining 20%.
Reducing Construction’s Impact
To try to reduce the construction industry’s impact on the environment, researchers have been trying to modify the fabrication process; the challenge is to make the process more sustainable without compromising the quality of the cements. This is especially important for higher grade cements used for advanced construction.
A way to obtain good quality cement using less energy is the use of grinding additives; these are generally organic molecules which favor the grinding process – i.e. the formation of small micrometric particles from the clinker. This, in turn, leads to a decrease in the energy required in the process.
Examples of Cement Grinding Additives (CGAs) include triethanolamine, diethylene glycol and glycerol.
What is Bioglycerol?
Glycerol is a polyalcohol – you can see its formula in the figure on the side. Scientists are well aware of its potential as a CGA. However, using glycerol in the concrete construction industry has historically been restricted due to the high price of the pure substance.
In 2005, however, some Italians researchers had the idea to use bioglycerol, or crude glycerol, and could see the potential of this approach. Both ‘bioglycerol’ and ‘crude glycerol’ are terms that refer to glycerol obtained as a by-product of biodiesel production.
Now some scientists from National Research Council of Palermo (Italy), who were involved in the early work on bioglycerol, published a review paper on this topic. Their research was conducted in cooperation with the Universities of Milan (Italy) and Panama. They published their research in Biofuel, Bioproducts and Biorefining in April 2015.
Bioglycerol: An Excellent Grinder
Decoded Science spoke to professor Mario Pagliaro, leading scientist in the study. Dr. Pagliaro tells us:
“Bioglycerol is a most valuable compound for the concrete construction industry, exactly for the same reason which makes it unusable in pharmaceutical or personal care applications, namely that it is not pure.
Residues of soap as well as of α-tocopherol from the biodiesel production, lead to excellent mechanical, anticorrosive properties and to better performance as a CGA than both pure glycerol and oil-derived additives. Reduction in power consumption in the grinding process is up to 10% when compared to oil-derived additives, while concrete finished structures are more than 10% stronger than identical structures obtained with no added bioglycerol.
Finally, the stability of the antioxidant polyphenol contained in brown bioglycerol ensures prolonged anticorrosive properties.
These are properties which can have a huge impact if considered on new huge concrete structures, such as the enlarged Panama’s Channel, dams, bridges, airport pavements and highways.”
Bioglycerol’s Other Qualities
Bioglycerol addition also decreases the adhesion of the cements to molds and forms; this means that it is easier to remove the cured cement from the molds frequently employed during construction, without creating surface imperfections. Conventionally, construction companies use highly polluting spent diesel fuel or spent mineral oils as form releasing agents, a practice that has recently been forbidden in the US leading to the introduction of much more expensive lubricant formulations.
Crude Glycerol Has Great Potential
“These data clearly show the potential of bioglycerol as a multifunctional cement additive.” Dr Pagliaro told Decoded Science, “Its use improves the quality of the final products, but also the overall sustainability of the concrete construction business; in fact, with bioglycerol, we do not use an oil-derived chemical, but a renewable oleochemical obtained from processing biomass.
Since its first use as a CGA in Italy about ten years ago, construction companies have been using bioglycerol at increasing pace; in 2010, for instance, bioglycerol accounted for 20% of the grinding additives in the European market.
As a trend for the future, we expect bioglycerol to find widespread application. Indeed, ever more data published by different researchers in different countries confirm its suitability for the manufacture of superior cements. Moreover, the biodiesel and oleochemicals industries are growing in scale all over the world, which means that we will have enough amounts of cheap bioglycerol available for satisfying this and other applications of this great platform biochemical.”
Bioglycerol: Making the Construction Industry More Sustainable
As the impact on the environment of the construction activities is huge, it is important to make this industry more sustainable. The use of bioglycerol, a by-product from the diesel production, is surely a step in the right direction, as it reduces the dependance on oil-derived chemicals. Moreover, the process requires less energy and gives materials with better properties.
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