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The technology of manufacturing paving slabs.

Author: Yuri Zarva
Source: trotuar.ru
E-mail: medbisnes@trotuar.ru

Form preparation

preparation of concrete mix

molding on a vibrating table

keeping products in a day in forms

formwork

packing and storage

The process of manufacturing paving slabs includes several basic stages:

  1. preparation of forms;
  2. preparation of concrete mix;
  3. molding on a vibrating table;
  4. keeping products during the day in forms;
  5. Decking of products;
  6. packing and storage.

PREPARATION FORMS

Forms for the manufacture of products can be used plastic, rubber and rubber-like (polyurethane). The number of molding cycles that can withstand molds is: for rubber - up to 500 cycles, for plastic - 230-250, for polyurethane - 80-100 cycles.

Forms before pouring concrete in them are coated with special compounds or poured concrete without pre-lubricating the mold. When working without lubrication, the new molds are treated with an antistatic agent, after inspection of the mold, they are inspected and, if necessary, washed with 5-10% hydrochloric acid solution.

For the lubrication of molds, you can use emulsol, OPL-1 (Russia) and SNAA-3 (England). To preserve the surface of the mold, lubricants containing oil products can not be used. The layer of lubricant applied to the surface of the molds must be thin, because the excess of the lubricant leaves pores on the surface of the finished product.

Emulsol greases and OPL-1 are applied by brush before each filling, lubricant CPA-3 is applied by brushing or by spraying. Lubricants SVA-3 is enough for 2-3 moldings. The temperature during application should be 18-20 ° C.

mixture preparation
FIG. No. 1

PREPARATION OF CONCRETE MIXTURES

For the preparation of decorative concrete, it is better to use a forced-mix concrete mixer. Basically the order of preparation of the mixture does not differ from the preparation of ordinary concrete (Figure 1). The pigment is fed about 30 seconds before the cement is fed.

Optimum mixing mode:
sand + pigment - 15-20 seconds;
sand + pigment + crushed stone - 15-20 s;
sand + pigment + crushed stone + cement - about 20 s;
sand + pigment + crushed stone + cement + water + additives - 1-1,5 min;
only 2-2.5 minutes.

To increase the durability of concrete, its wear resistance and impact resistance, it is also possible to add polypropylene, polyamide or glass alkali-resistant fibers 5-20 mm in length and 5-50 μm in diameter in the amount of 0.7-1.0 kg per 1 m3 of concrete. The length of the fibers should correspond to the largest diameter of the coarse aggregate in the concrete. Fibers with good dispersion form a three-dimensional lattice in concrete, which significantly increases the bending strength, impact resistance and wear resistance of concrete.

Polypropylene and alkali-resistant glass fibers are introduced with mixing water; The polyamide fiber is introduced into the finished concrete mixture, i.e. at the last stage, while the mixing time of the mixture is increased by 30-50 seconds.

When using a microsilica additive, the following schedule of preparation of the concrete mix is ​​adopted:

sand + microsilica + pigment - 30-40 s;
sand + microsilica + pigment + cement - about 30 s;
sand + microsilica + pigment + cement + water + additives - 1-1.5 min.
shaker
FIG. No. 2 - Vibration table

FORMATION ON THE VIBRATORY

The ready-made concrete mixture has a workability of OK = 3-4 cm. Therefore, short-time vibration processing is used for its compaction. After the preparation of the concrete mixture, it is laid into molds and compacted on a vibrating table (Fig. 2).

In the production of colored tiles in plastic forms, layer-by-layer molding can be used to save pigment: the first face layer of concrete is prepared using pigment, the second layer of concrete without it.
For separate molding, it is necessary to have two mixers for the preparation of concrete of the first and second layers.

FIG. № 3 - There is a curb in the curb.

When molding, first lay the front layer of colored concrete 2 cm thick and compact for 40 seconds. After this, the second layer of concrete is laid without pigment and is compacted by vibration for another 20 seconds. With a different mobility of concrete, it is necessary to choose your sealing time on the molding table.

EXTRACTION OF PRODUCTS

After molding, the products in the molds are installed in stacks 3-8 rows high, depending on the thickness and configuration of the tile. So, for example, square plates are put no more than 3 rows. After this, the piles are covered with a polyethylene film to prevent evaporation of moisture. The holding temperature must be at least 15 ° C. Additional heating is not required. After 24 hours of soaking in molds, it is possible to form (release products from molds).


FIG. No. 4 - "Piling" of paving slabs on a vibrating table.

STRIPPING

Formwork formwork is produced on a special knock-out table with vibration (Fig. 4), while it is recommended to warm 2-3 minutes in a hot water bath (temperature 45-50 ° C) to facilitate mold shaving with products. In this case, the effect of high thermal expansion of polymers is used in comparison with concrete.

Decking of square plates and facade tiles occurs without any special devices. It should be noted that the release without preliminary heating shortens the service life of the mold by approximately 30% and can lead to the marriage of finished products, especially for thin products.


There is a process of knocking out paving slabs. And its storage on pallets.


FIG. No. 5 - The tiles are packed and ready for sale.

PACKING AND STORAGE

After the decking, the tiles are laid on the euro pallets "face" to the "back", tie them with a packing tape. To ensure the further hardening of concrete and preservation of the presentation of products, they must be covered with polyethylene shrink or stretch film.

In the summer, products are released when they reach 70% of the design strength, which corresponds approximately to 7 days of hardening of concrete, counting from the moment of its manufacture. In winter, leave is made when 100% of the design strength is reached (28 days from the date of preparation of concrete).