The correct answer is D. Sea sand used in structures causes dampness, efflorescence, and disintegration.
Sea sand is a type of sand that is found near the ocean. It is made up of small, round particles of quartz that have been eroded by the waves and tides. Sea sand is often used in construction because it is a strong and durable material. However, it can also cause problems in structures if it is not used properly.
One of the problems with sea sand is that it can absorb water. When sea sand absorbs water, it can cause the structure to become damp. This can lead to the growth of mold and mildew, which can damage the structure and make it unhealthy to live in.
Another problem with sea sand is that it can cause efflorescence. Efflorescence is a white, powdery substance that forms on the surface of concrete and other masonry materials. It is caused by the leaching of salts from the concrete or masonry. Salts can leach from concrete or masonry when they are exposed to water. When the water evaporates, the salts are left behind and form efflorescence.
Efflorescence can be unsightly, and it can also damage the surface of the concrete or masonry. If efflorescence is not removed, it can eventually cause the concrete or masonry to crumble and disintegrate.
Finally, sea sand can cause disintegration. Disintegration is the breakdown of concrete or masonry materials. It is caused by the action of water, salt, and other environmental factors. Sea sand can accelerate the process of disintegration because it is a porous material that can absorb water and salts.
For these reasons, it is important to use caution when using sea sand in construction. It is important to make sure that the sea sand is properly treated to prevent it from absorbing water and causing problems.