Optimal Design of pH-neutral Geopolymer Foams for Their Use in Ecological Plant Cultivation Systems

Abstract

We have calculated that with the world population projected to increase from 7.5 billion in 2017 to 9.8 in 2050, the next generation (within 33 years) will produce 12,000–13,000 Mt of plastic, and that the yearly consumption will reach 37–40 kilos of plastic per person worldwide. One of the branches of the plastics industry is the production of plastics for agriculture e.g., seed trays and pots. In this paper, novel metakaolin-based geopolymer composites reinforced with cellulosic fibres are presented as an alternative to plastic pots. Materials can be dedicated to agricultural applications, provided they have neutral properties, however, geopolymer paste and its final products have high pH. Therefore, a two-step protocol of neutralisation of the geopolymer foam pots was optimised and implemented. The strength of the geopolymer samples was lower when foams were neutralised. The reinforcement of geopolymers with cellulose clearly prevented the reduction of mechanical properties after neutralisation, which was correlated with the lower volume of pores in the foam and with the cellulose chemical properties. Both, neutralisation and reinforcement with cellulose can also eliminate an efflorescence. Significantly increased plant growth was found in geopolymer pots in comparison to plastic pots. The cellulose in geopolymers resulted in better adsorption and slower desorption of minerals during fertilisation. This effect could also be associated with a lower number of large pores in the presence of cellulose fibres in pots, and thus more stable pore filling and better protection of internal surface interactions.

Mechanical Properties of Basalt Fiber Reinforced Fly Ash-Based Geopolymer Composites

“…Geopolymer binder is a brittle material with a relatively low tensile strength and deformation capacity. To rectify these issues, reinforcement is required [1,2]. In particular, the brittleness of these materials results in cracking under tensile and flexural loading [1,2].…”

“…To rectify these issues, reinforcement is required [1,2]. In particular, the brittleness of these materials results in cracking under tensile and flexural loading [1,2]. The challenge is to replace the conventional steel bars traditionally applied in construction industry, through the proper short fibres [3].…”

Impact of Flax Fiber Reinforcement on Mechanical Properties of Solid and Foamed Geopolymer Concrete

“…Most of the research was dedicated to reinforcement by artificial fibers such as carbon [27][28] or glass [29][30], including waste products [29][30]. Some of the investigations have been done on the composites with natural fibers such as hemp [31][32], abaca [33], cellulose [34][35] and jute [36]. The mineral fibers; for example, basalt have been also tested [28,37].…”

“…The investigation with cellulose shows the positive influence of this addition on pH and the possibility of applying this material for eco-friendly pots [34][35]. The flax fibers in foamed geopolymers were only investigated as an addition to long fibers [36].…”

Variation Among Spring Wheat (Triticum aestivum L.) Genotypes in Response to the Drought Stress. II—Root System Structure

“…Roots, as one of the primary organs, play an important role in vascular plants. They are a hidden part of a plant, responsible for growth, development and productivity, anchorage, and supplying stem and leaves with water and nutrients [1][2][3][4][5][6][7][8]. Roots constitute a source of organic matter, they influence the soil structure, aeration, and its biological activity [9][10][11].…”