2.Role of Fibers in Geopolymer
Composites
Steel fibers, glass fibers, basalt fibers, polypropylene fibers, and
blended fibers are all fibers currently used in concrete. Given that
geopolymers and cement are both brittle materials, fibers play similar
roles in geopolymers, mainly the following roles in the polymer such as
nano filling and crack bridging. The key factors to be considered while
selecting fibers for reinforcement modification of cement or geopolymer
composites include: (1) compatibility of material properties with
application; (2) adequate fiber-matrix interaction to transfer stress;
and (3) optimal aspect ratio to ensure effective post-cracking behavior.
The addition of fibers affects the fluidity and mechanical properties of
viscous carbides, which depends on the surface properties, shape, types
and flexibility of the fibers[8].
At present, the fibers used in geopolymers can be roughly divided into
the following three
categories,
i.e., inorganic fiber,
natural
fiber and synthetic fiber. To be
specific, inorganic fiber mainly includes steel fiber, glass fiber and
basalt fiber; natural fiber mainly consists of plant fiber, animal fiber
and mineral fiber; and synthetic fiber mainly refers to polyethylene,
polypropylene, polyvinyl alcohol fiber, etc. Table 1 lists the main
characteristics of common fibers added to geopolymer.
- Inorganic fibers. Inorganic fiber can be traced back to the
application of ancient asbestos[9]. These fibers consist of a
mixture of alumina and silicon dioxide and are often used in high
thermal applications such as refractories due to their high melting
point. In addition, these fibers also possess the advantages of low
cost, high tensile strength, chemical stability and excellent
insulation
properties[10].
- Natural fibers. Nature fibers are mainly divided into plant fiber,
animal fiber and mineral fiber. Plant fibers mainly include fruit
fiber, leaf fiber, stem fiber, seed fiber, and bast fiber; animal
fiber mainly refers to the silk fiber in animal hair; and iron
asbestos, crocidolite, actinite and carlite fibers are the main
mineral fibers[11].
- Synthetic fibers. Synthetic fibers refer to the fibers made of
synthetic polymer materials, including polyester fiber, polyamide
fiber, polypropylene fiber, polyvinyl alcohol fiber, polyvinyl
chloride fiber, etc.
Table1 Characteristics of common fibers