Polymer concrete: key material properties, production

What is this stuff? How does it differ from the usual concrete mixes in terms of composition and consumer properties? Can I make polymer concrete with my own hands? Where and how is it used? Let's try to find the answers.

What it is

Definition

Let's find out what polymer concrete is? The key difference between the material we are interested in and ordinary concrete is that synthetic resins are used instead of portland cement as a binder. As a rule, thermosetting; less often - thermoplastic.

Reference: thermosetting is called a polymer in which irreversible chemical changes occur during heating, leading to changes in its strength or other properties. Simply put, after a one-time heating, the plastic no longer melts when it reaches the same temperature. Thermoplastic polymers, on the contrary, make a phase transition with each heating.

Do not confuse our hero with another material - polymer cement concrete. In our case, polymers are used as the sole binder. Polymer-cement concrete is ordinary concrete based on Portland cement, modified with synthetic additives to give it any specific properties (increased elasticity, wear resistance, water resistance, etc.).

Key properties

What does replacing cement with polymers give in terms of consumer qualities?

• Increased tensile strength. Concrete based on cement have excellent compressive strength, but bending or tensile loads are perceived reinforcing cage.
• Reduced brittleness. The material is much more resistant to shock loads.
• Elasticity. Where the concrete monolith breaks, polymer concrete only slightly deforms.
• Water resistant. Portland cement during drying gives a significant shrinkage, which provides a porous structure of concrete. In contrast, polymers after the final curing decreases in volume very slightly; moreover, shrinkage does not lead to porisation, but to a small decrease in the linear dimensions of the finished product.

To clarify: to improve the insulating qualities and reduce weight in some cases in the production of polymer concrete products, the use of porous aggregates is practiced. In this capacity, expanded clay and perlite sand are used. However, the pores of the aggregate do not come to the surface, and if so - water resistance does not suffer.

• Frost resistance. Actually, this property directly follows from the previous paragraph: there is no pore - no, and there is no crystallization of water in them that tears the material during freezing.

• Increased wear resistance. Polymer binder trite stronger cement stone to break; tearing a filler particle from it is much more difficult.
• Chemical resistance. And it is caused by the properties of polymers: most of the resins are inert to the action of aggressive gases and liquids.

Application

Let's explore the main applications of polymer concrete.

Production

Regulations

The material we are discussing is considered relatively new and of foreign origin; However, a study of the regulatory documents on which it is produced will lead to an unexpected discovery. Instructions for the production of polymer concrete and products from them under the number CH 525-80 was adopted in 1981 and remains relevant to this day.

Let's study the main theses of the document. For all products from polymer concrete, the normal temperature regime is considered to be from -40 to +80 degrees Celsius.

To clarify: if the upper limit is due to the possibility of using thermoplastic resins that soften when heated, then the lower limit is due to the increased brittleness of the polymers during freezing. In the absence of shock and mechanical loads in general, the lower limit of the operating temperature can be increased painlessly to the actual in the most severe climatic zones.

Binder

The composition of polymer concrete, according to the text of the document, may include the following polymers:

Aggregate

The main aggregate is crushed rock. The use of sedimentary rocks (limestone, shell rock, etc.) is not allowed: its low compressive strength will significantly impair the performance of the product.

The size of the rubble fraction is determined, no matter how funny it sounds, by its maximum diameter:

1. If the largest size does not exceed 20 mm, one fraction is used - 10-20 millimeters.
2. In cases where the largest size reaches 40 mm, it is recommended to use two fractions: 10-20 and 20-40 millimeters. Small gravel will contribute to a more dense filling and, accordingly, will increase the final strength of the material.

Note: for porous aggregates (already mentioned claydite and perlite), the maximum size is 20 mm; two fractions are used: 5-10 and 10-20 millimeters. At the same time, the percentage composition of the aggregate is divided between the coarse and fine fractions in the ratio of 60:40 percent by weight.

In addition to coarse, small (so-called grain) aggregate is used. Quartz sand usually plays this role - natural or crushed. Requirements for it are mainly reduced to the absence of impurities - dust, silt and clay, which are able to worsen the adhesion between the aggregate and the binder.

Filler

In addition to the mineral aggregate, the product includes ground filler - mineral flour. The standard provides several options.

It is allowed to use crushed rubble and quartz sand. For the material that is prepared on the basis of urea-formaldehyde resins, additionally used water-binding additive - gypsum (GOST 125-70).

Composition example

As a sample, we analyze the composition of the heavy polymer concrete based on the furan-epoxy binder FAED. The source of information we will serve all the same document CH 525 -80.

Curious: BSK performs two functions at once. It serves as a polymerization catalyst (curing agent) and provides dehydration (dehydration) of raw materials.

Technology

What is the technology of polymer concrete (more precisely, its production) in industrial conditions?

1. Fillers are thoroughly washed from all sorts of pollution. As we remember, they can adversely affect the final strength of the product.
2. The next stage is drying. The moisture content of the aggregate should not exceed 1 percent; It is recommended to adhere to the mass content of water up to 0.5%.
3. Fractional components are loaded into the mixer. The sequence of loading and intermediate operations is strictly regulated:

1. Loading rubble.
2. Sand is added.
3. The filler is added.
4. The mixture is stirred for 1-2 minutes.
5. Added binder.
6. The mixture is stirred for 3 minutes.
7. The hardener is added.
8. Stirring for 3 minutes - and the material is ready for pouring.

The form can be removed from the finished product in a day. Strength at room temperature takes from 20 to 60 days. It, however, can be accelerated by heating to 60-80 degrees; the temperature rises and falls at a rate of 0.5 ° C per minute in order to avoid the growth of internal stresses.

As you can see, the production technology does not imply any special difficulties; in the presence of a binder, hardener, concrete mixer and vibrating table, it is quite realistic to produce polymer concrete at home.

Nuance: to clean the concrete mixer from the remnants of the mixture will have extremely quickly. After the addition of the hardener, the setting takes less than an hour

Treatment

How and how are polymer concrete products treated? Is it possible to grind and glue them?

How to cut and drill this material?

• For bonding used mastics and adhesives based on all the same synthetic resins. Mastics, in addition to the binder itself, contain stone flour.

• Normal sandpaper is suitable for sanding. Felt wheel is used for polishing; gloss can be applied using GOI paste (polishing paste developed by the State Optical Institute).

• In principle, the material can be drilled using conventional concrete drills; However, diamond drilling holes in concrete with a polymer binder gives a much better result. The edges of the holes remain perfectly smooth, without chips. For holes of large diameter (for example, under the mixer in a polymer concrete worktop for the kitchen), a diamond crown is used.
• The ideal cutting tool is again a diamond saw. It is also preferable for structures whose appearance is not so important (cutting reinforced concrete with diamond circles makes it possible to make the cutting edges perfectly smooth and not to change the circle during reinforcement); in the case of the same tabletop, sloppy cutting will hopelessly spoil its appearance.

When processing a material, it is generally worth avoiding its strong heating. Temperatures above 120-150 degrees are contraindicated for thermoplastic binders.

Conclusion

We will consider our acquaintance with the material held. For more information about what happens polymer concrete, where and how it is used, the reader can find in the video in this article. Successes!