RECENTLY I purchased a bag of cement and three bags of sand from my local building supplier’s yard only to find that the former was the same cost as three times its weight in sand. This price per unit differential is easily explained for cement needs costly manufacturing and sand, composed of silica, is easily obtainable and is a natural resource. I needed both materials, to mix as concrete, to repoint the weathered areas between the slate slabs on the façade of my house.
Gypsum mortars of lime and mud mixed with straw saw slabs created to build the Egyptian pyramids, 5,000 years ago. The Romans, three millennia later, refined this process using small gravel and coarse sand mixed with hot limed water to create their colosseums and arenas, such as at Arles, in France.
Modern concrete, using sand and lime, was invented in 1756 by John Smeaton for his construction of the first Eddystone lighthouse in Cornwall, United Kingdom. This lighthouse came into operation in 1759 and lit by candles which needed half hourly replacements throughout the night. Eventually eroded by wave attack, the top section of the lighthouse was later, in 1882, reassembled as a landmark, on Plymouth Hoe in the adjoining county of Devon and has always been known as ‘Smeaton’s Tower’. It was Joseph Monier, a Parisian, who invented reinforced concrete in 1849 by combining metal compressed with sand and cement mix to withstand heavy loads.
Today, every tonne of concrete needs six to seven tonnes of sand or gravel to create the right mix. All around the globe in cities we see ever higher skyscrapers as commercial buildings in city centres to combat high land rental values or in the suburbs to house high densities of people in small land areas. Fortunately, the local urban authorities in both Sabah and Sarawak have imposed strict regulations on building heights for high rise housing developments.
Sand mining and uses
Sand is almost an indestructible material if composed of silica (silicon dioxide – SiO2). Besides its main use as a building material in temperate climates, it also makes up 90 per cent of the asphalt used on roads. Vehicle traction is thus improved, as is road safety. In tropical areas, much of the white sand is derived from the erosion of coral reefs and limestone rocks, is calcareous in nature and referred to as ‘fossil sand’.
As a young lad my favourite beach near my home in West Cornwall, England, was at Porthcurno. There, white sands composed of seashells are washed from offshore by the incoming tides. In September 2018, I stayed on the idyllic island of Volcano just off northern Sicily where the beaches had black volcanic sands essentially made of silica in quartz form.
Land extensions, as in the last century and even today, have seen Singapore’s landmass ever growing by 130 square km simply through the purchase of nearly 500 million tonnes of overseas sand. The disputed sovereignty of the Spratly Islands, has seen, in very recent years, China extending its influence in the construction of military bases by sand dredging from offshore supplies in the South China Sea. It is estimated that 60 per cent of the world’s sand is used in China, where it consumes more sand in three years than the USA consumed last century!
River and beach mining have been banned in most of the western world countries but, however, it still occurs when offshore dredging and pumping sand ashore to replenish tourist beaches or fortify areas faced with coastal erosion, as sea levels rise. A good example of this was when, in August this year, it was announced that a crumbling boulder clay cliff was threatening people living in two villages in Norfolk, United Kingdom, and nearby major gas terminal, which processes 33 per cent of that country’s gas.
It is proposed that 1.8 million cubic metres of sand will be pumped ashore to create ‘sandscaping’ in the construction of a 6km-long sand dune, seven metres high with a width of 250 metres. Predicted to last for 20 years before nature takes its course, I believe that such a venture is like living in a fool’s paradise. Sea levels are constantly rising and could see a swift end to this plan let alone the financial implications in its creation.
Riverbeds are frequently dredged for sand/silt deposits to create deeper water channels for ever increasing larger ships. We could well see this in Kuching as huge cruise liners ply their way from one port of call to the next. We are told that such very temporary visitors will boost the tourist economy but at what price to the environment and our estuarine and river ecosystems?
What we do know is that the Sarawak River will become navigable to take ocean liners but how will this affect our fishing fleets with an inevitable change in habitat for their catches? Have environmentalists and conservationists been given a voice in such plans? What may occur locally is part of a larger global problem for sand dredging or mining of estuaries in tropical and subtropical environments can lead to the disappearance of mangrove swamps, seagrass, and to the destruction of marine and semi-aquatic wildlife species.
A worldwide dilemma
In layman’s terms sand is sand. But beware for rounded estuarine and riverbed sand grains should not be used for building construction or even DIY jobs unless it is guaranteed that it has been thoroughly washed to rid it of salt. Estuarine sand grains are rounded and do not securely bind with cement. Sharp, angular, sand grains, usually derived from sandstone quarried rocks are a better and more lasting option.
Geologists will argue that most sandstone rocks were laid down in estuarine deltas but millions of years ago, with tectonic forces in action, these compressed rocks are now evident as hills, mountains or coastal cliffs.
The UK is not devoid of criticism. Some 25 per cent of its sand is dredged from the ocean floor. Approximately 20,000 years ago, the huge glacially deposited Dogger Bank in now the North Sea, comprised of gravel and sand, has been repeatedly dredged for many a year. This has led to a decline in the North Sea’s breeding grounds for many species of fish and crab. The loss of sea sand nearer to our seashores certainly accelerates coastal cliff erosion, for sandbanks and beaches are natural absorbers of wave energy.
I can wax lyrical of many examples of coastal erosion caused by dredging of offshore sand and shingle deposits in the UK. This is caused by the deepening of seawater with less frictional energy lost to the seabed and thus the greater force of the incoming waves.
Sand is cheap to buy but at what long term cost to our environment?
We should ask ourselves as to where sand is derived? Mostly it is produced by subaerial action of weathering and erosion of rocks with the detritus washed into our rivers and estuaries. Some sand deposits are the result of glacial outwash streams at the snout of glaciers. Only very small amounts of sand are produced by wave erosion. Professor Andre Guilcher, an acclaimed Breton coastal geomorphologist, maintained that “the sea is a consumer and not a producer of sand”.
We should remember his historic words and realise that never, ever, should sand mining exceed the rate of supply from the sources of any upstream river or any over exploitation of natural glacial meltwater deposits on the land surface. Alas, with climate change, we will see many more of glacial outwash sand deposits in the near future.
Only today, when inspecting and servicing my log burning stove, before winter sets in, did I find a glass pane cracked on the front of the stove. I have purchased a costly replacement and insisted that it was made of Pilkington’s heat resistant glass from St Helens in Lancashire, UK, which was founded in 1826. For over a century, this famous factory utilised the nearby Shirdley Hill glacial outwash deposits as its source of silica. Now that it is a Japanese owned company, I just wonder whether my stove will have a new glass frontage from Japan or China. Glass, made of sand, has a huge impact on our style of living but at what cost to our environment and its ecosystem?
Just look at the outside and the inside of our homes and try to estimate how many tonnes of sand have been used. I, for one, have not the slightest idea! However, we do know that disused glass and demolished concrete structures can be recycled into new glass forms and former building structures. When torn down, building rubble can be crushed into pieces, by machinery on site, to provide the foundations of new build.
The latter saves overall new construction costs and together with the former will save our planet from being constantly raped from natural sand extraction.
Sadly, we live in an era of disposable commodities with little thought as to the sources of the very things we throw into bins or how they can be recycled. Sand must be saved for supplies are rapidly running out!