Why we don't use desert sand 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't help but give rise to a kind of doubt: if there is so much sand in the desert, why don't we use the sand in the desert to build houses?

When we build houses, we do need to use a lot of sand, which is called "sand" in professional terms, and its main use is to prepare mortar and concrete.

Mortar is a mixture of water, cement, and sand with relatively low strength and is usually used for masonry, decoration, and plastering, while concrete is a mixture of water, cement, sand, and stone with relatively high strength and can bear a lot of weight and is mainly used for the main stress parts of the house structure.

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

The stones and sand in concrete are also called "aggregate", as the name implies, "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 cementitious material closely linked.

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

1, their strength to be high enough.

2, not too many impurities.

3, the sand particles can not be too coarse, nor too fine, generally used to build houses of sand, coarse sand, sand, and fine sand, the three specifications, 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.

What's more, due to a long time of the weathering effect of "polishing", 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 standard of 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 reach the standard for building houses, the relatively high mining and transportation costs will usually discourage people from the idea.

Because of this, we usually do not use desert sand to build houses. Among other types of natural sand, mountain sand and sea sand are not preferred 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 these sands is relatively high, and under the action of long-time hydraulics, it contains relatively few impurities, and their grain coarseness also meets the standard 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 the common stones in nature such as river pebbles, granite, and some construction waste with suitable conditions into the sand, which is also called mechanism sand.

It is worth mentioning that in case there is no other sand available, it is not impossible to build houses with desert sand, but it is just much more troublesome. For example, we can use inorganic binding materials like epoxy resin to combine the sand, and its strength will be comparable to 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 ".