Why don't we use sand from the desert to build houses?

About 20% of the earth's land surface is desert, and almost all of the ground in these barren areas is covered by thick sand, such as the famous Sahara Desert, whose average thickness of sand can be as high as about 150 meters.

Such a situation can not help but give rise to a kind of doubt: if there is so much sand in the desert, then why we do not use the desert sand to build houses?

When we build houses, we do need to use a lot of sand, according to the professional term, this should be called "sand", its main use is to prepare mortar and concrete.

Mortar is a mixture of water, cement, and sand, its strength is relatively low, usually used for masonry, decoration, plastering, etc., while concrete is a mixture of water, cement, sand, and stone, relatively speaking, the strength of concrete is very high, can withstand a lot of weight, mainly used in the main parts of the housing structure under stress.

In simple terms, the basic theory of concrete is to fill the gaps of large stones with small stones, fill the gaps of small stones with sand, and then wrap the stones and sand with contentious material, and also fill in their gaps, so that the concrete can be dense enough, and then achieve a high enough strength.

Stone and sand in concrete are also known as "aggregate", as the name suggests, "aggregate" is the material that can act as a "skeleton", and sand is among the finest particles of that One, so sand is also known as "fine aggregate", they play a role in the concrete is: fill in the gaps between the larger particles of "aggregate", and the larger particles of "aggregate "and cement paste as a contentious material closely linked.

To produce qualified concrete, the "fine aggregate" of the sand needs to meet a series of conditions, of which three are essential, namely.

1, their strength should be high enough.

2, not too many impurities.

3, sand particles can not be too coarse, nor too fine, generally used in the construction of housing, and have coarse sand, sand, and fine sand these three specifications, have the corresponding fineness modulus 3.7 to 3.1, 3.0 to 2.3, 2.2 to 1.6.

However, desert sand misses the above three conditions almost perfectly. First of all, desert sand is made of loose rock weathering, which causes its strength to be usually not up to the standard of building houses.

Secondly, desert sand usually contains a large number of impurities harmful to concrete, such as mica minerals, organic matter, sulfides, chlorides, etc. These substances can significantly reduce the strength of concrete, but also weaken its durability of concrete.

More importantly, due to the long time by role of weathering "polishing", the desert sand particles are generally very small, their fineness modulus is less than 1.5, and some desert sand will even be less than 0.7, which obviously can not meet the standards for building houses.

On the other hand, the desert areas on the earth's surface are generally far away from human settlements, so even if the sand in a desert can barely meet the standard for building houses, the relatively high cost of mining and transportation will usually discourage people from the idea.

Because of this, we usually do not use desert sand to build houses, and among other types of natural sand, mountain sand and sea sand are not the first choices for building houses because they usually contain a lot of clay and silt, and sea sand contains a lot of organic matter and salts.

Generally speaking, people will give priority to river sand and lake sand to build houses, because the strength of this sandstone is relatively high, and in a long time under the action of water, its impurities are relatively small, and their grain coarseness also meets the standards of building houses.

By the way, even if we can't find enough natural sand, we can also make suitable sand artificially, using a stone crusher, we can break river pebbles, granite, and other common stones in nature and some construction waste with suitable conditions into the sand, this kind of sand is also known as mechanism sand.

It is worth mentioning that in case there is no other sand available, it is not impossible to use desert sand to build houses, but it is much more troublesome, for example, we can use inorganic binding materials like epoxy resin to combine the sand strength will be theirgraintheir migratory concrete.

Another example is that we can screen the desert sand, from which the relatively large particles, relatively small impurities of sand, and then these sand and cement as raw materials to create a strong enough mortar block, and then the mortar block for crushing and sieving, so you can get the "fine aggregate" can be used to build houses This will give you the "fine aggregate" that can be used to build a house.