Fig. 2. The interfacial bonding of different fibers with geopolymer
steel fiber[31]; (b) glass fiber[14]; (c) basalt
fiber[14]; (d) polypropylene fiber[31]; (e) jute
fiber[23]; (f) sisal fiber[23][14, 23, 31]
Reproduced from [14, 23, 31], with permission from [Publisher]
Fig. 2(a) shows that the steel fiber and geopolymer matrix contact well,
and there is no interface peeling phenomenon. Given that steel fibers
are often hydrophilic, they can significantly improve the energy
absorption and bending strength of composites[31]. The glass fiber
and basalt fiber in Figures 2(b) and 2 (c) present obvious interfacial
debonding with geopolymer. The addition of glass fiber increases the
compressive strength and flexural strength of the matrix by 32.6 % and
30.35 %, respectively, while the addition of basalt fiber increases the
compressive strength and flexural strength of the matrix by 27.3 % and
35.36 %, respectively[14]. Fig. 2(d) describes the interface
bonding between polypropylene fiber and geopolymer matrix. Organic fiber
also shows the interface peeling phenomenon, and the addition of adding
polypropylene fiber increases the compressive strength and flexural
strength of the matrix by 27.5 % and 16.07 %, respectively. Fig. 2(e)
(f) depicts the interfacial bonding between jute, sisal fiber and
geopolymer in natural fibers. The jute with a mass fraction of 1.5 %
increases the compressive strength and tensile strength of the matrix by
64 % and 45 %, respectively, while the sisal fiber with a mass
fraction of 2.5 % increases the compressive strength and tensile
strength of the matrix by 76 % and 112 %, respectively.
The bonding between steel fiber and geopolymer is found the best, and no
interface peeling phenomenon is observed. Considering the high strength
and rough surface of steel fiber, the mechanical bonding force with
geopolymer is formed, and leads to the optimal mechanical properties of
geopolymer.