We will find that for stone care, there are many problems caused by dampness. Let’s share some tips on stone application and maintenance in humid environments.
The porous structure of stone
To thoroughly understand the relationship between stone and water, it is necessary to first understand the structural characteristics of stone.
1. Different structures, different characteristics
There are many types of building decoration materials around us, and their characteristics displayed in use are different. For example, before using stone, protection should be taken. Sometimes cement also needs to be treated with waterproofing. Going further, ancient ships were all made of wood. Before launching these ships, they need to be treated with tung oil for waterproofing. However, on the other hand, other materials such as plastic, metal, and glass have never heard of the need for protection.
2. What is a porous structure?
Taking stone as an example, there are various pore structures on natural stone, but they can be most intuitively divided into two categories:
① Visible holes: such as holes, cracks, microcracks, etc., can be classified as visible holes as long as they are directly visible to the human eye or can be detected by careful observation.
② Invisible pores: Contains visually indistinguishable microcracks, various fine pores, micropores, pores, and other structures scattered throughout the stone, which cannot be distinguished by the human eye.
3. Invisible pores determine the characteristics of stone materials
But who determines the characteristics of stone in these two types of pores—— It is an invisible hole. This is because the invisible pores in the stone have radii ranging from 10 to 10 to -10, which means they reach the nanoscale and micrometer level. And the entire stone is composed of minerals, cementitious substances, and these pores. So, these invisible micropores actually form a wide range of micro channels throughout the entire stone. It is precisely these micro channels that form the true foundation for the porosity of stone. The porous structure of cement and wood is similar to this. However, plastic, metal, and glass do not have these nanoscale and micrometer scale structures, so they do not possess porosity.
The relationship between the porosity and water absorption of stone materials
It is precisely these porous properties that make the relationship between stone and water very unusual.
1. Direct water absorption
Visible and invisible pores serve as channels for storing and entering water, allowing the stone to absorb water and hide dirt.
2. Hygroscopic phenomenon
According to the data in the table below, micropores with different radii (in meters) can absorb moist water vapor in the environment and air through condensation and capillary action. This also indicates that in practical use, various forms of water, including visible, invisible, and damp, can cause stone to absorb water. The water absorption effect of pores of different sizes.
The harm caused by water absorption to stone materials
It is not an exaggeration to say that the vast majority of the problems encountered in the application of stone materials are closely related to water. It can even be said that the vast majority of problems are caused by water.
1. After the stone absorbs water, it will cause mineral reactions and changes, resulting in various problems such as rust spots, yellowing, water spots, alkalization, color difference, pulverization, bursting, and fracture.
2. After natural stone absorbs water, it can also cause a decrease in the binding force between minerals and cementitious materials, resulting in a decrease in the compressive strength and bending resistance of the stone. For example, the deformation of the stone after water absorption, compression, warping, microcracking, and fracture increase the risk of engineering use.
3. Natural stone has a high water absorption rate, which increases the weight of the stone. When applied on outdoor walls, it is affected by natural conditions such as rainy season and humidity. Water absorption makes the structure load-bearing, and rainwater and humidity promote the oxidation of structural components through the stone, affecting the safety of buildings.
4. Natural stone materials such as low density and limestone dissolve after absorbing water, resulting in the occurrence of surface loss, discoloration, potholes, aging, and other phenomena, which reduce the application performance of stone materials.
5. After natural stone absorbs water, it will freeze in the cold winter, and the temperature will rise and melt again. The volume of water freezing will expand. The repeated cycles of freezing and melting can cause stone fragmentation.
6. When maintenance is carried out in damp conditions, moisture can also dissolve the material, thereby affecting the polishing effect. It can be seen that behind various stone problems, there is basically the shadow of water