Geohug web notes; cement & sand for the green economy.

On the 25th June 2021, the regular Geohug webinar presented “Sand and Cement; the forgotten raw materials for the green economy”, by the Principal, Geologist Mark Burnett. The numerous presentation outline the need for more minerals to feed into the projections of the new green economy. Such presentations typically neglect to look at the growth in infrastructure that will needed to support this futuristic world. Power grids, urban water supply, along with high rise buildings, road, rail will grow. Concrete is used for most constructions, of which 2/3 is sand.

Portland cement primary raw materials can contain lime (60-65%), silica (17-25%), alumina (3-8%), Magnesia (1-3%), sulphur trioxide (1-3%), alkaline (0-1%), iron oxide (0.5-0.6%), calcium sulfate (0.1-0.5%). The conversion of limestone to lime produces much CO2 by-product, being an unavoidable greenhouse gas producer. Secondary raw materials typically adsorb other industry waste products, including slags, fly ash, flue-gas desulfurization gypsum, used foundry sand and recycled building materials. It is interesting to note that when some European countries close down all coal fired power stations, then their cement industries may need to import fly ash and other industrial waste materials.

Sand and gravels represent the largest mining commodities in the world. Sand composition is typically quarts, where size and angularity are important factors. The salt content must be washed out of sea sand, and desert sand tends to be too round. Most sand is sourced from river deposits, where the environmental impact is becoming more closely monitored. Singapore and other places use sand for land reclamation. Higher silica purity sand is suitable for the glass, electronics and similar industries.

It is difficult to get reliable figures on the quantities of sand and gravel being mined around the world. Most mining is undertaken by private enterprises, and are often embroiled in non-transparent practices. Some estimates can be determined through back calculating the consumption of cement, or the volume of new infrastructure etc. Between 2011 and 2013, China used more concrete than the US did in the entire 20th century. Viable alternatives to concrete & steel structures (cement and sand) are being researched, but all alternatives seem unviable or unpractical. ?