# Composites Containing Felt Wastes from the Automotive Industry
## 1 Introduction
### Materials  
This study's primary research material was waste felt from the automotive industry. The material was collected from the bulkheads of a worn-out vehicle--a Jeep Cherokee WK2, where it performed thermal and acoustic insulation functions. Moreover, the material was collected from vehicle disassembly stations in the form of soundproofing mats. Plastic mats were covered on the passenger compartment side to protect the felt from damage and dust. The protective coating was removed, and the material was then shredded using a wire brush mounted on a contour grinder to form felt fluff. Figure 1 shows the waste in matted form and as fluff after shredding. Shredding was carried out until individual yarn fibres could be separated up to the size quoted by felt manufacturers of 0.08-0.3 mm. The length of the fibres used was approximately 4-8 cm. According to the manufacturer's sheet, the felt had the properties presented in Table 1 below. The table also gives the types of fibres and the parameters of the yarn from which the felt is made. Portland cement CEM I 42.5N--SR 3/NA from Cemex companies was used as the cement for the concrete. According to the manufacturer's sheet, this cement is characterized by stable physical and chemical parameters with an appropriate setting time, high early and final strength parameters, low alkali content, and high resistance to aggressive chemical agents. Thanks to these advantages, it is popularly used in the production of concrete commodity mixtures. Table 2 shows the physical and chemical parameters of the cement used. Concrete plasticizer Qplast from the Simeplast company was used as a plasticizing admixture. According to the manufacturer's sheet, it is a highly potent plasticizing plasticizer that distributes the cement particles in the concrete mix. It is used to improve the working and service properties of the concrete mix while reducing the amount of batch water. According to the technical data, which are based on [87], it significantly improves the workability and cohesiveness of the mix, thus facilitating the conc \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Lp.** & **Parameter** & **Standards** & **Value** \\ \hline
1 & Density [ g/cm\({}^{3}\)] & 0.35+/\(-\)0.02 & 0.360 \\
2 & Breaking strength & \(\leq\)50 kg/cm\({}^{2}\) & \(\leq\)55 kg/cm\({}^{2}\) \\
3 & Tensile strength at break & \(\leq\)110\% & 90\% \\
4 & Free sulphuric acid content & \(\leq\)0.30\% & 0.25\% \\
5 & Botanical impurities content & \(\leq\)0.35\% & 0.18\% \\
6 & Mineral impurities content & \(\leq\)0.12\% & 0.01\% \\
7 & Fire protection properties & \(\leq\)70 mm/min & \(\leq\)10 mm/min \\
8 & Thermal resistance & max. up to 150 \({}^{\circ}\)C & 150 \({}^{\circ}\)C \\
9 & Yarn fibre thickness & - & 0.08-0.3 mm \\
10 & Fibre material & - & Polyesters, elastane, polyamide \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Properties of felt based on manufacturer’s data. Figure 1: Waste felt materials from the automotive industry, (**a**) in the form of soundproofing boards, (**b**) after shredding. cohesion and coherence of the mix, counteracting the segregation of components and the separation of water, allowing a reduction in the amount of water by approximately 10%, while maintaining high workability, and simultaneously increasing the strength, water and frost resistance, durability, and density of the concrete. Due to the fact that the composite is filled with high water-content waste, it was decided to use it. The primary technical parameters of the admixture, based on its technical sheet, are shown in Table 3.  
Silica dust from the SLIMIC Poland company was used as a concrete additive. According to the manufacturer's description, microsilica originated as a byproduct obtained during the production of silicon metal and ferrosilicon alloys in arc furnaces. It consists of fine dust particles, the diameter of which was estimated to be, on average, 100 times smaller than the average grain size of cement.