SU986792A1 - Method of producing concrete articles - Google Patents

Description

The invention relates to the field of the construction industry and is intended for the manufacture of products from preheated concrete mixtures and compaction by pressing. The method of compaction of a concrete product is degraded, concluding with vibration and pressure varying in time, which initially rises to 4-50 MPa and then gradually decreases to 1.6-25 MPa and rises again to its original value, This cycle of pressure change is repeated 2-3 times. The use of 2-3-fold pressing does not increase the degree of compaction of the concrete enough, and the use of two types of compaction - vibration and pressing - complicates the technology of forming the product. In addition, with this method, the products with a high height of section are poorly compacted, and there is still a need for milling pressing equipment (400-5000 tons per 1 m of product). The closest to the proposed method is a method of manufacturing concrete products, including heating the concrete mixture to 65-80, placing it into a mold with forced heating to 85-110 ° C, compaction by vibropressing at a constant load of 10 Pa and thermostating 2}. The disadvantage of the known method is the low compaction efficiency and the low strength of concrete (about 10 MPa) after thermos curing. The purpose of the invention is to increase the strength of concrete. 1 The goal is achieved by the fact that in the method of manufacturing concrete products, including the heating of the concrete mixture up to 65-80 s, laying it in with forced heating to 85-110 ° C, compaction by pressing at a constant load to 10 m1a and thermosal curing, pressing is carried out by additionally applying a pulsating load with a frequency of 1–30 Hz, a value equal to 5–20% of a constant load. The method is carried out as follows. The concrete mixture is heated to 6580 ° C and placed in a mold heated to the same temperature, then the mixture is heated by electric current to 85-110 ° C. After that, the concrete mix is compacted with a constant pressure of 0.05–10 MPa with the application of an additional impulse load, the value of which is 5–20% of constant specific pressure, and the frequency of the pulses is 1–30 Hz. Subsequent hardening is carried out under the conditions of thermosetting and cooling for about 3 hours. The dependence of the pressure change of pressing — the time t is shown in the figures. FIG. Figure 1 shows a graph of the change in the upper boundary parameters of the pres P frequency f 0.1 Hz; in fig. 2 - the same, the change of the lower boundary parameters Pj-pgc at the frequency f О, 1 Hz. Example. Samples - cylinder M in size (6,100 mm, h110, are made of a concrete mixture of composition C: P: S: S 1: 1,038: 2.35: 0.3, the components (gravel, sand and water) are preheated to. After filling the forms heated to the same temperature, the mixture is heated to a fixed current until the samples are then hydroimpulsed at a frequency of 12 Hz at a constant specific pressure in the period between hydro pulses of 50 MPa with an increase in hydro pulses by 20% Subsequent hardening under the conditions of thermosealing and cooling is carried out for 3 hours. Test results are listed in Tables: A decrease in the hydroimpulse force (amplitude) by 5–20% during the period between oscillation pulses ensures the creation of complex particle oscillations and the presence of a permanent underload. A reduction of less than 5% does not allow the creation of complex oscillation modes, and Reducing the amplitude by more than 20% at low unit pressures of hydro-pulsation (0.05 MPa) will lead to a decompression of the concrete mix. The use of the frequency of pulsating oscillations of hydro-pulse in the range of 1–30 Hz causes the appearance of a low-frequency wave field in the concrete mixture with complex forms of oscillatory movements of particles, which gives them increased intensity. The proposed method makes it possible to increase the strength of concrete by a factor of 2 or more, and improves working conditions by eliminating vibration. Table 1

one

one ,

thirty

thirty

Table 2

2,446

20.8 2.584 62.4 2.477 31.2 2.592

80.3

Claims (2)

1. Author's certificate of the USSR 553110, cl. At 28V 3/00, 1975. 2.Mironov S.V. and others. Methods of short-term heat treatment of concrete and the prospects for their use in the production of precast concrete. M., NIIZHB, 1972, p. 43-46.  X Vvx ". LYP ffflfC. g o 5 Yu G5 20 25 Jff 3S 4ff 45 5ff f5 ffff SS 70 t, c rrpec f pcc fas-asfjff j ;;. , fu f