Advances in Natural Fibre Composites by Raul Fangueiro & Sohel Rana

Author:Raul Fangueiro & Sohel Rana
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Materials and Methods

The geopolymer matrix was made from fly ash from the CHP plant in Skawina (Poland). The fly ashes were thoroughly investigated as a possible raw material for the production of the geopolymer matrix being a base for various composites. SEM observations, EDS analysis and the previous research confirmed its suitability for such matrix. The chemical composition of the mentioned ash consists of approx. 56% SiO2, 23.5% Al2O3, 6% Fe2O3, 3.5%, K2O, below 3% CaO and MgO, and less than 1% of other components e.g., TiO2, Na2O, P2O5 and BaO [4]. High value of SiO2 and Al2O3 is advantageous for creating geopolymers, additionally low amount CaO confirm the usability of this particular fly ashes for the prosecco alkali activation. The fly ash density amounted to 2.22 g/cm3. The morphology of the particles of fly ash was typical of such by-products of coal combustion. Regarding the particle size distribution of the examined fly ash, the size of approx. 60% particles was <56 µm [4].

The matrix of the composites was 8 M sodium hydroxide solution combined with the sodium silicate solution (liquid glass at a ratio of 1:2, 5). In order to manufacture the composites flakes of technical sodium hydroxide were used and water solution of sodium silicate R–145 whose modulus was 2.5 and density 1.45 g/cm3. Tap water was used as batched water instead of the distilled one. The alkaline solution was prepared by means of pouring the aqueous solution of sodium silicate and water over solid sodium hydroxide. The solution was mixed and left until its temperature became stable and the concentrations equalized.

The samples were prepared using sodium promoter, fly ash and raffia fibres (the 1% by mass of the composite). To reinforce the geopolymer matrix raffia fibres were used whose length was approx. 3 mm and diameter approx. 1 mm. The research involved the samples reinforced by raffia (Fig. 1) and artificial fibre—PP (polypropylene). PP is the traditional additive for building materials such a cement. The fly ash was mixed with fibres about 5 min by using mixing machine. Then, the solution was mixed with fly ash and raffia fibres about 15 min (to receive the homogeneous paste). Next, it was poured into two sets of plastic moulds. The first set consisted of the moulds dedicated to undergo compressive strength tests and the second set consisted of the moulds dedicated to undergo flexural strength tests. The samples were hand-formed and then subjected to vibratory removal of air bubbles. Tightly closed moulds were heated in the laboratory dryer for 24 h at 75 °C. Then, the samples were unmoulded. They were investigated after 28 days.

Fig. 1Exemplary SEM images for raffia fibres

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