# The Influence of Steel, Glass and Basalt Fibres on Selected Parameters of Construction Mortars
## 4 Discussion  
After conducting laboratory tests, i.e., on mortars with a standard composition and the addition of steel (ST), glass (SZ) and basalt (SB) fibres, it should be concluded that the issue raised in the article--whether the use of any fibre available on the market will improve all the rheological properties and parameters of hardened mortars--remains open. If we are interested in two parameters, which fibres should we choose? Does the addition of fibres impair any properties of fresh or hardened mortars? Is there a change in the parameters currently being tested compared to those tested twenty years ago on fibres with partially different parameters? Adding fibres to mortars reduces the slump of fresh mortars in the consistency test conducted on a slump table. For glass fibres, this flow was the lowest. It can be concluded that basalt fibres have the least impact on this parameter. Here, the use of a chemical admixture should also be considered in the case of a mortar with a higher fibre content and low workability. The addition of fibres to mortars significantly affected the change in their volume density. The test showed that the addition of fibres to mortars increased the bulk density compared to the reference series. When glass fibres were used, the volume density increased by 7.7% compared to the SW sample, while for steel fibres, an increase of as much as 14.4% was recorded in relation to the reference series. Fibres in a cement matrix are usually distributed evenly and randomly, both in terms of position and direction. This distribution is mainly due to the difficulty of predicting local tensile stress distributions during the service life of the component. In practice, the distribution of fibres is mainly influenced by the smallest dimension of the component, for example, the thickness of the board. In thin plates, the fibres are usually arranged parallel to their surface, which ensures optimal mechanical properties. Disturbances in the uniform distribution of fibres can occur for various reasons, such as excessive vibration or a concrete mix that is too liquid. To improve the strength properties, it is possible to deliberately order the fibre  
Figure 13: Comparison of compressive strength of mortars stored in laboratory conditions and subjected to freezing after 28 days of curing. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Time [cycle]** & **SW [g]** & **SZ [g]** & **ST [g]** & **SB [g]** \\ \hline
0 & 520.69 & 538.96 & 521.88 & 576.68 \\ \hline
150 & 495.21 & 515.53 & 499.88 & 551.87 \\ \hline weight loss, [\%] & 4.9 & 4.3 & 4.2 & 4.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 15: Determination of the decrease in the mass of mortars subjected to freezing. distribution if the tensile stress distribution in the matrix that will arise during use is known. Based on sample fractures, no agglomeration or clustering of fibres was observed in the tested mortars. In summary, the compressive strength of the mortars with fibre additives tested after 28 and 56 days of curing did not differ significantly. The differences in the compressive strength increase ranged from 1 to 3 MPa. Here, the type of fibre used did not affect this parameter. The positive effect of fibres on compressive strength is due to the likelihood of the fibre itself being located along the crack path leading to the destruction of the sample at a position that still allows them to be bridged. In the flexural strength test, the type of fibre used in the mortar is very important. Compared to the reference series (SW), mortars with basalt fibres achieved the highest increase in flexural strength: by 48% after 28 days and by 47% after 56 days of curing. The extended curing time of the mortars did not affect the trend in flexural strength gain. The next mortars to achieve higher flexural strength gains were those with steel fibres. Their flexural strength was lower by 16.7% than that of the mortars with basalt fibres after 28 days of curing.