SU1207772A1 - Method of moulding large-size articles from dry concrete - Google Patents

Description

The invention relates to the construction industry, in particular to the production of building materials, and relates to a method for manufacturing products, mainly from rigid concrete mixtures of a complex configuration, with a height greater than 400 mm.

The purpose of the invention is to increase the porosity of products. ,

The method is carried out as follows.

In the form or in the matrix of the vibropress installed on the vibrating plate, a concrete stiff mixture is laid. Laying the mixture is carried out simultaneously with the vibration effects. The oscillation frequency of the vibro-platform is 25-75 Hz. The mixture thus laid is affected by time-inertia and constant-static loads and creates a specific pressure of 0.015-0.03 MPa. With the simultaneous impact of these loads, each of which has its own oscillation amplitude, the compaction process is intensified and the quality index of the manufactured products is improved. At the same time, the oscillation amplitude of the static load is 0.5-1.4 mm, inertial 0.2-0.8 mm, and the time of their joint action is 1-5 s. Then, in order to avoid the occurrence of destructive formations that reduce the physical and mechanical indicators of products, stop the action of the inertial load and make the addition of a static load for 2-25 s at an oscillation amplitude of 0.5-2.0 mm and a specific pressure of 0.005-0.01 MPa,

An example. Molded samples of concrete products with a height of 400 mm

l

an area of 0.3 m of concrete mix with a stiffness of 120 with the following composition (1 m of the mixture), kg:

Portland Cement M 500

Sand (m, p 2.5) Water

580 1640 180

The concrete mix is placed in the form of a vibropress equipped with a vibrating plate with drivers of vertical-directed oscillations with a frequency of 50 Hz and an amplitude of 0.5 mm. Then, the laid mixture is affected by a stamp consisting of a hydraulic punch driven by the hydraulic system (static load) and an engraving 077722

stock load (inertial load). The specific pressure of the stamp on the mixture is 0.02 ffla for 3 sec., While the amplitude of the oscillation is 5.9 punch, and the load is 0.6 mm. Then, the effect of gravitational loading is terminated by excluding it from the oscillatory system due to special devices 10, for example, installation on fixed stops. After this, the final compaction is performed for 10 s at a specific pressure of 0.008 MPa and an oscillation amplitude of 15–1.2 mm, created by the punch.

And p and m e p 2. Molded samples of concrete products with a height of 500 mm and an area of 0.3 m of concrete mix with a stiffness of 120 with the following composition of 20 (l m mixture), kg:

Portland cement M 500 580 Sand (M 2.5 1640

Water 180

The concrete mix is placed in the form of a 25 vibropress equipped with a vibrating plate with drivers of vertically directed oscillations with a frequency of 50 Hz and an amplitude of 0.5 mm. Then, the laid mixture is subjected to a punch, 30 consisting of a drive from the hydraulic system of a punch (static load) and a gravitational load (inertial load). The specific pressure of the stamp on the mixture is 0.03 ffla for 5 s, while the amplitude of oscillation of the punch is 1.4 mm, and the load is 0.8 mm. Then, the effect of gravitational loading is stopped, after which the final compaction of 25 s is performed at a specific pressure of 0.01 MPa and an amplitude of 2.0 mm of vibrations created by the punch.

The hardening of the molded products is carried out in natural conditions for 28 days.

The tests are carried out according to GOST 1006-76. Values of the degree of compaction are evaluated by the value of the compaction ratio of the concrete mix.

V actual concrete mix during compaction at a fixed mode ij

V theoretical concrete mix,

calculated by the equation 55 absolute volumes

The results of the molding and the quality parameters of the obtained products are given in the table,

35

40

45

50

five

l

91 g

and

Claims (1)

METHOD FOR FORMING LARGE-SIZED PRODUCTS FROM RIGID CONCRETE MIXTURES, including laying the concrete mixture into a mold and compacting it with vibration at an industrial frequency and a varying amplitude of oscillations under load, characterized in that, in order to increase the strength of the products, compaction is carried out for 1-5 seconds under load with inertial and static loads of 0.0150.03 MPa, followed by removal of the inertial load and compaction under load with a static load of 0.005-0.01 MPa for 2-25 s. £ o m m m N3