Not only it can be washed perfectly but river sand (and gravel) tend to be much better for concrete when compared to "crushed" aggregates.
More or less the reason is that usually for a given size river ones are harder/more resistant, and have rounded edges (which also imply a bigger resistance) due to the cycles (wear, long time immersion, etc.) they were subjected to in the river.
And, as a final advantage, concrete made with rounded aggregates is usually easier to pump.
Oh so Africa is building long lasting concrete buildings and making life easier for everyone... something that most of the western world and a huge part of the developing world has already been using for a long time in the same way? No, let us tell you something much more important: how the freaking rivers are "dying".
I did. What is obvious is that you know nothing out of what is written selectively in an article in a vague way. If you think the sand illegally exported out of Africa is anywhere significant to the amount being consumed in Africa, you need to reconsider your sources of information.
They are discussing offshoring this sand to other countries that can afford it, not to build useful African structures. An argument from "The world has already been using this for a long time" could be used for any number of grotesque and terrible acts (and has) so I will ignore that part.
The main complaint about the "rivers dying" is that it has a outsized impact on the poor who use those rivers for food and water (which is no longer available and which is no longer captured, respectively.)
While some people truly believe in the preservation of nature over humans, most of us "Environmentalists" want to save the environment because of the direct and indirect human suffering inappropriate exploitation of our shared resources cause.
>They are discussing offshoring this sand to other countries that can afford it, not to build useful African structures.
No, they are talking about both. What they didn't mention was the sand being illegally exported is nothing compared to what is being used locally and you somehow assumed that it is exclusively being offshored.
>most of us "Environmentalists" want to save the environment because of the direct and indirect human suffering inappropriate exploitation of our shared resources cause
"Human suffering" you presume your children will have to suffer... and you try your best to deter anything anyone does to improve their lives even in the most insignificant way while you "harm the environment" by couple of orders of magnitude than over a billion people just by existing. You're fooling nobody.
Theres a lot of domestic construction going on in African countries. That growth is all using modern methods, which means lots and lots of pumped concrete.
Anti-environmentalism leads to concrete human and industrial harm. The classic example is having forested buffers between farmland. This is industrially necessary to avoid desertification. The USA learned this the hard way in the 30's. Some countries in Africa have also learned this lesson the hard way, others are still learning it.
This is a similar problem. When you dredge up some sand and a river disappears, you've made a mistake that has human consequences and it probably was not worth whatever you did with the sand.
>The classic example is having forested buffers between farmland. This is industrially necessary to avoid desertification.
I see. That must be the reason why Americans are starving and Africans are so fat because of too much they grow on their undesertified fertile farmlands.
Let's assume your points are 100% correct. If you make them by ranting, like you've been doing in these threads, you not only break the site rules, but discredit the truth. That's not in anybody's interest.
It is possible for two facts to be correct at the same time. Yes it is good that Africa has access to modern building materials. It is also bad that extraction is causing problems for rural communities. These two facts are not inconsistent.
All you have really proven is how much you dislike environmentalists. A debate that is quite colloquial to a few cossated western countries. In a lot places people actually live within touching distance of the environment. The pros and cons are just obvious to everyone. Young local men get paid to move sand, which is good. But farmers need water for crops and erosion is a problem. It becomes news outside because no one has a good solution. Just another intractable social problem.
It's actually quite striking if you handle Sahara desert sand its amazingly fine and smooth, I imagine other sand deserts where the sand is wind blown for eons is similarly smooth.
Here's an idea - why not require the companies to replace the river sand with desert sand after mining it? Have they tried to use desert sand in the river?
This is Africa you're talking about. As much as that sounds like noble and a good idea, convincing local communities and especially businesses here is not going to happen unfortunately.
It's a consequence of being in the third world and having a "catch up at all costs" mentality. Besides, conservation and environmentalism just isn't as in-grained in most African cultures as it is in the west.
Even if you convinced the local government of putting such a law on the books, the odds of them being able to track and enforce such a law is next to impossible. Maybe in more developed countries like South Africa or Namibia, but not in most of the others.
Well why not have whoever is concerned about this sand thing fund an operation to go and bring sahara sand and dump it all along the riverbed? And the operation would be funded by local taxes on the companies extracting the resources. Solved.
Unless you're saying these governments have no negotiating power about their own land and resources? In which case this is just straight-up PLUNDER.
Industrial scale mining often has unintended consequences - there was a long running sand operation in California that caused erosion all around it on the coast unless you asked the company that was doing it.
http://www.mercurynews.com/2017/06/27/controversial-beachfro...
Crushing rocks down to sand is common. Here's the machinery.[1] The trick is to bang the rocks together. China seems to be making lots of sand for concrete. There are many manufacturers in China making rock crushers and sand-making machines.[2] China has plenty of mountain rock suitable for rock crushing.
Here's a marketing paper on making sand, and what to make for making concrete.[3]
It's being used for local construction. Even if it wasn't, do you have the same sympathy for Australia which is a major source of many minerals? Continents aren't people. They don't have property rights. People do, and it's important for people to be able to exercise those rights to benefit their own lives.
Most of the sand is mined to make concrete (cement + sand + rocks + water = concrete). I think they use much smaller amounts of much higher purity sand for making silicon.
48 comments
[ 3.2 ms ] story [ 20.5 ms ] threadIn the US, dredging rivers or land near a waterway is pretty restricted. Sand is typically mined from open pits, see: https://en.wikipedia.org/wiki/Sand_mining#United_States
[0]: http://www.smithsonianmag.com/science-nature/world-facing-gl...
More or less the reason is that usually for a given size river ones are harder/more resistant, and have rounded edges (which also imply a bigger resistance) due to the cycles (wear, long time immersion, etc.) they were subjected to in the river.
And, as a final advantage, concrete made with rounded aggregates is usually easier to pump.
A lot of the accessible sand in the US is from glacial deposits.
Wisconsin is mentioned in the Wikipedia article as having a boom in sand mining and the surface geology there is nearly entirely a result of glaciers.
Environmentalism is anti-humanism.
I did. What is obvious is that you know nothing out of what is written selectively in an article in a vague way. If you think the sand illegally exported out of Africa is anywhere significant to the amount being consumed in Africa, you need to reconsider your sources of information.
https://news.ycombinator.com/newsguidelines.html
https://news.ycombinator.com/newsguidelines.html
They are discussing offshoring this sand to other countries that can afford it, not to build useful African structures. An argument from "The world has already been using this for a long time" could be used for any number of grotesque and terrible acts (and has) so I will ignore that part.
The main complaint about the "rivers dying" is that it has a outsized impact on the poor who use those rivers for food and water (which is no longer available and which is no longer captured, respectively.)
While some people truly believe in the preservation of nature over humans, most of us "Environmentalists" want to save the environment because of the direct and indirect human suffering inappropriate exploitation of our shared resources cause.
Yes.
>They are discussing offshoring this sand to other countries that can afford it, not to build useful African structures.
No, they are talking about both. What they didn't mention was the sand being illegally exported is nothing compared to what is being used locally and you somehow assumed that it is exclusively being offshored.
>most of us "Environmentalists" want to save the environment because of the direct and indirect human suffering inappropriate exploitation of our shared resources cause
"Human suffering" you presume your children will have to suffer... and you try your best to deter anything anyone does to improve their lives even in the most insignificant way while you "harm the environment" by couple of orders of magnitude than over a billion people just by existing. You're fooling nobody.
This is a similar problem. When you dredge up some sand and a river disappears, you've made a mistake that has human consequences and it probably was not worth whatever you did with the sand.
I see. That must be the reason why Americans are starving and Africans are so fat because of too much they grow on their undesertified fertile farmlands.
Let's assume your points are 100% correct. If you make them by ranting, like you've been doing in these threads, you not only break the site rules, but discredit the truth. That's not in anybody's interest.
All you have really proven is how much you dislike environmentalists. A debate that is quite colloquial to a few cossated western countries. In a lot places people actually live within touching distance of the environment. The pros and cons are just obvious to everyone. Young local men get paid to move sand, which is good. But farmers need water for crops and erosion is a problem. It becomes news outside because no one has a good solution. Just another intractable social problem.
>The sand used for construction comes mainly from riverbeds and oceans. Desert sand, it turns out, is too smooth for the mix.
It's a consequence of being in the third world and having a "catch up at all costs" mentality. Besides, conservation and environmentalism just isn't as in-grained in most African cultures as it is in the west.
Even if you convinced the local government of putting such a law on the books, the odds of them being able to track and enforce such a law is next to impossible. Maybe in more developed countries like South Africa or Namibia, but not in most of the others.
Unless you're saying these governments have no negotiating power about their own land and resources? In which case this is just straight-up PLUNDER.
http://www.bbc.com/capital/story/20160502-even-desert-city-d...
Here's a marketing paper on making sand, and what to make for making concrete.[3]
[1] https://www.youtube.com/watch?v=1CpjRMICXNM [2] https://www.alibaba.com/showroom/vsi-crusher.html [3] http://www.metso.com/showroom/construction/new-type-of-crush...
https://www.nytimes.com/2017/03/01/magazine/sand-mining-indi...
This poor continent keeps getting jacked.
French: https://www.arte.tv/fr/videos/046598-000-A/le-sable-enquete-...
German: https://www.arte.tv/de/videos/046598-000-A/sand-die-neue-umw...
(I didn't find an English version or English subtitles for it, sorry...)
It's available until September 18.