Research methods of foam phosphogypsum blocks based on phosphorus fertilizer waste

Persistence of foam depending on water temperature (minutes)

Nomi	Occupied size	Water temperature, ^0С
		12	20	35	50
PB 2000	600	8	6	5	3
PB luxury	720	26	20	17	4
Zimpor	320	29	23	15	8

The obtained results show that the stability of foams decreases with increasing temperature. In our opinion, this is due to the decrease in the molecular attraction forces of water at increased temperature, which in turn led to the acceleration of water separation from the foam.

Figure 1 shows the size and appearance of foaming agents used in the experiment when mixed with water to form foam.



Figure 1. Sizes of foaming agents
Methods of studying the physical-mechanical and deformational properties of foam phosphogypsum:
The main properties of foam phosphogypsum are its strength, brands, classes and deformation properties. The strength of foam phosphogypsum depends on the binder, fine filler and chemical additives. In general, foam phosphogypsum has a smaller porous structure, the stronger it is.
When designing the composition of foam phosphogypsum, it is assigned to classes (brands) according to the resistance to foam concrete, heat insulation and cold resistance.
According to the limit of compressive strength of foam phosphogypsum, the design brand is determined relative to the compressive resistance (MPa) of cube-shaped reference samples.
The draft brand of concrete for cold resistance is determined based on the results of standard cold resistance tests of samples. This mark is determined in points where concrete can be affected by freezing and thawing many times.
Foam phosphogypsum has waterproofing and other special requirements. The compressive strength limit is determined in 28 days.
For foam phosphogypsum products, it is also possible to determine the limit of compressive strength in other terms specified in the standard or technical conditions.
The strength of foam phosphogypsum is determined by testing 3 standard samples prepared in a specific way. Samples are taken from the middle of the foam phosphogypsum mixture, molded and leveled in laboratory equipment.Prepared samples are covered with a moistened cloth for at least 24 hours in molds, the air temperature is kept at 20±20C, then the samples removed from the mold are stored in a special chamber with relative humidity, then the samples removed from the mold are stored in a special chamber with a relative humidity of not less than 95% and a temperature of 20±20C It is stored for 28 days under normal conditions.
The limit of compressive strength of concrete is 20x20x20 cm, 15x15x15 cm (basic sample) and 10x10x10 cm standard samples.
In order to bring the strength indicators to the main sample of 15x15x15 cm, it is necessary to multiply the scale coefficients by 0.95 and 1.05, respectively, when testing samples with sides of 10 cm and 20 cm [6].
The strength of foam phosphogypsum directly depends on the same location of its structural components. In order to ensure that the structure of foam phosphogypsum is uniform, it is necessary to thoroughly mix the constituents. Foam phosphogypsum project brand should be equipped with high-quality gypsum, foaming agents, chemical additives, technological processes, and automated production. The guaranteed brand of foam phosphogypsum in the project can be determined by means of its strength rating tool. The foam phosphogypsum class serves as such an indicator.