Intro to the Concrete Industry

Michelle Heath

The Concrete Industry Series:

The Environmental Impact of the Cement Industry | The Concrete Industry

Introduction to the concrete industry

Man has been producing and using concrete for over 8500 years.

Cement production globally has increased more than 30-fold since 1950.  China and India, both leaders in global infrastructure construction, are the two largest producers of cement.

Did you know: Aggregates are the largest volume of solid resources extracted and traded globally, with the market predicted to grow from US$458.97 billion in 2019 to US$723.28 billion by 2027. 

Sand and gravels (aggregates) are foundational materials essential to economic growth but extraction rates are exceeding natural sand replenishment rates and in many regions of the world there is little to no associated regulation.  According to the United Nations, damming of rivers for hydro-electricity production and irrigation has reduced the amount of sediment flowing downstream to where most of the world’s large rivers have lost between 50 and 95% of the natural sand and gravel delivery to oceans.  And as the seas rise, we are losing sand from our shorelines.

Aggregates are the largest volume of solid resources extracted and traded globally, with the market predicted to grow from US$458.97 billion in 2019 to US$723.28 billion (Reports and Data) by 2027. 

An estimated 40-50 BMT of crushed rock, sand and gravel are extracted from quarries, pits, rivers, coastlines and the marine environment each year, over half of which is consumed by the construction industry.  Regretfully, 10-15% of what is extracted from rivers and seashores is done so illegally and can have significant negative environmental and social impacts (UN).

Extraction volumes, sources and uses of sand and gravel are not well documented but with few exceptions, most of this resource is extracted and consumed regionally due to high transport costs.  In 2019, the Asia Pacific region dominated the market (~65%), followed by North America (~17%) (Reports and Data).

Freshwater is a scarce resource so conservation is critical.  A recent study, published in 2018 in the journal Nature, quantifying water use in global concrete production determined that in 2012, water use in global concrete production required 9% of global industrial water withdrawals (~1.7% of total global water withdrawal).   As well, it was determined that by 2050, 75% of the water demand for concrete production would likely be in regions of the world already experiencing water scarcity.

Water management is a major challenge to the sustainability of cement manufacturing as it is required for cooling equipment and exhaust gases, in emission control systems, in preparing slurry in wet process kilns as well as for domestic use at cement facilities.  Though water recycling is widely applied throughout the cement industry, discharge water issues can have environmental and ground water level impacts.

An average dry-process cement plant uses 100 to 200 litres of water per tonne of clinker produced (Global Cement).  A recent study examining the water footprint of cement plants in India, determined the average full-cycle water requirements (mining through to manufacturing) was found to be 500 litres per tonne of cement (NCB).

If cement were a country, it would be the third largest CO2 emitter after China and the US and, as an industry is second to agriculture.  CO2 emissions from cement production come from both non-combustion sources and combustion sources.  The non-combustion CO2 emissions are generated by the carbonate oxidation in the cement clinker production process.  Clinker is the main constituent of cement and is the largest of non-combustion sources of CO2 from industrial manufacturing (~4% of total global CO2 emissions in 2015).  The fuel combustion emissions of CO2 related to cement production are also about 4% of global CO2 emissions, thus CO2 production accounts for approximately 8% of global CO2 emissions (Chatham House).

The PBL Netherlands Environmental Assessment Agency (2015) noted that the average clinker fractions in global cement production have decreased between 60% and 80% compared to nearly 95% for the original Portland cement and with this came a proportional decrease in CO2 emissions per tonne of cement produced (20% lower than in the 1980s).  For example, in China, the average clinker fraction in their total national cement production decreased from about 76% in 2000 to 60% in 2015, which resulted in an annual decrease of 250 million tonnes in CO2 emissions. 

Between 2014 and 2018, the global clinker-to-cement ratio experienced an increase of 1.6% per year resulting in a global average clinker-to-cement ratio of 0.70 (IEA).

The sand and gravel industry outlook to 2030 is expected to be one of strong growth in Asia, particularly India, Africa and Latin America, GAIN estimating global aggregates demand rising to 60 billion tonnes per annum. 

The global cement and concrete product market is expected to decline from $370.1 Billion in 2019 to $328.6 billion in 2020 mainly in response to the economic slowdown owing to COVID-19 but is expected to recover and reach $441.7 billion by 2023 (ResearchAndMarket.com). 

New technologies and innovations are emerging to make cement and concrete more sustainable including cements that over their life actually absorb CO2,reducing their carbon footprint. 

There is no other building material today that can replace concrete but related environmental impacts are growing and its ongoing use will require more than just changing its chemical formula.  In addition to recycling and reuse, city planners and builders must ensure sustainable designs and managed renovations and demolition thereby reducing the demand on scarce resources.