## 4 Results of Research and Testing
### Sound Absorption
The compositions contained Portland cement as well as local fine and coarse aggregates. The coarse aggregate was the limestone crumb with a maximum size of 20 mm. It was shown that freezing and heating do not significantly affect the sound absorption of the samples. Similar values of the sound absorption coefficient were obtained when evaluating the sound absorption of cement concrete based on rubber crumb [30]. The sound absorption coefficients were more than 0.5 for compositions with different water-to-cement ratios (0.45, 0.50 and 0.55) and the rubber crumb amount (5.0% and 7.5% by fine aggregate mass) in the frequency range of 200-3000 Hz. The reduction in the compressive strength of samples with the crumb amount of 5% and the water-to-cement ratio of 0.45 was 23-25% both in paper [30] and for composition No. 2. It should be noted that the reduction in the compressive strength of sample of composition No. 5, which differs in the grain composition of the rubber crumb, was only 13%. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{No.} & \multirow{2}{*}{**Composition**} & \multirow{2}{*}{**Mass,\%**} & \multirow{2}{*}{**Average Density, kg/m3**} & \multicolumn{6}{c}{**Sound Absorption Coefficient at Frequencies, Hz**} \\ \cline{6-11}  & & & & **63** & **80** & **100** & **200** & **400** & **800** & **1000** & **2000** \\ \hline \multirow{4}{*}{Reference} & semi-aqueous gypsum & 53.8 & & & & & & & & & & \\  & Portland cement & 14.0 & & & & & & & & & & \\  & superplasticizer & 2.6 & 1012 & 0.31 & 0.31 & 0.33 & 0.39 & 0.39 & 0.43 & 0.43 & 0.48 \\  & metakolain & 1.3 & & & & & & & & & & \\  & water & 28.3 & & & & & & & & & & \\ \hline \multirow{4}{*}{2} & semi-aqueous gypsum & 35.5 & & & & & & & & & & \\  & Portland cement & 10.6 & & & & & & & & & & \\  & metakolain & 1.3 & & & & & & & & & & \\  & superplasticizer & 0.9 & & & & & & & & & & \\  & rubber crumb of fraction & 2.5 - 2.5 mm & 1.258 & & & & & & & & & \\  & rubber crumb of fraction & 2.5 - 1.25 mm & 7.5 & & & & & & & & & \\  & rubber crumb of fraction & 1.25 - 0.63 mm & 6 & & & & & & & & & \\  & rubber crumb of fraction & 0.63 - 0.315 mm & 7.56 & & & & & & & & & \\  & rubber crumb of fraction & 0.315- 0.16 mm & 1.258 & & & & & & & & & \\  & water & 26.51 & & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Compositions and properties of material based on gypsum-cement-pozzolan binder. In conclusion, in comparison with the results of other studies it can be noted that the values of compressive and tensile strength in bending are higher for samples with rubber crumb of improved grain composition. It is stated that the nature of the destruction of samples changes from brittle to plastic since the rubber crumb inside the material stretches and does not allow a sample to collapse quickly. The field of the application of cement and gypsum sound-absorbing composites based on rubber crumb is quite extensive. For example, a gap of at least 20-30 mm should be left between the ceiling and the finishing row of groove-ridge gypsum boards when installing an interior wall. This gap is usually filled with mounting foam that reduces the sound insulation properties of the entire wall. The proposed composition of the gypsum composite can be used to fill this gap with the provision of sound insulation properties. In the case of the yield of the building foundation, the layer of the proposed gypsum composite can be deformed, which prevents cracking in the wall itself.