Effect of nano-clay on mechanical and thermal properties of geopolymer

Peer review under responsibility of The Ceramic Society of Japan and the Korean Ceramic Society.

Figures & data

Table 1 Chemical composition of fly-ash (wt%).

SiO2	Al2O3	CaO	Fe2O3	K2O	MgO	Na2O	P2O5	SO3	TiO2	MnO	BaO	LOI
63.13	24.88	2.58	3.07	2.01	0.61	0.71	0.17	0.18	0.96	0.05	0.07	1.45

Table 2 Physical properties of the nano-clay platelets (Cloisite 30B) [13].

Color	Off white
Density (g/cm^3)	1.98
d-Spacing (0 0 1) (nm)	1.85
Aspect ratio	200–1000
Surface area (m^2/g)	750
Typical dry particle sizes	90% volume < 13 μm
	50% volume < 6 μm
	10% volume < 2 μm

Table 3 Formulation of samples.

Sample	Fly-ash (g)	NaOH solution (g)	Na2SiO3 solution (g)	Nano-clay (g)
GP	1000	214.5	535.5	0
GPNC-1	1000	214.5	535.5	10
GPNC-2	1000	214.5	535.5	20
GPNC-3	1000	214.5	535.5	30

Table 4 Porosity and water absorption for pure geopolymer and geopolymer nano-composites.

Sample	Density (gm/cm^3)	Porosity (%)	Water absorption (%)
GP	1.84 ± 0.02	22.2 ± 0.4	12.1 ± 0.2
GPNC-1	1.92 ± 0.02	21.3 ± 0.3	11.1 ± 0.1
GPNC-2	2.05 ± 0.02	20.6 ± 0.3	10.0 ± 0.2
GPNC-3	1.98 ± 0.03	21.0 ± 0.2	10.6 ± 0.2

Fig. 1 X-ray diffraction pattern of nano-clay (Cloisite 30B).

Fig. 2 X-ray diffraction patterns of fly-ash, GP and GPNC-3.

Fig. 3 Flexural strength and flexural modulus of samples GP, GPNC-1, GPNC-2 and GPNC-3.

Fig. 4 Compressive strength of samples GP, GPNC-1, GPNC-2 and GPNC-3.

Fig. 5 Hardness of samples GP, GPNC-1, GPNC-2 and GPNC-3.

Fig. 6 SEM images of the fracture surface of geopolymer nano-composites with different loadings of nano-clay: (a) pure geopolymer, (b) 1.0 wt%, (c) 2.0 wt%, (d) 3.0 wt%, agglomerated nano-clay particles embedded in the matrix at: (e and f) low magnification and (g and h) higher magnification.

Table 5 Peak areas and peak heights ratios of geopolymers at Si–O–Si stretching vibrations from FTIR spectra.

Sample	Wave-number of Si–O–Si peak	Ratio of peak heights	Ratio of peak areas
GP	983	1	1
GPNC-1	983	1.02	1.02
GPNC-2	981	1.19	1.07
GPNC-3	980	1.15	1.03

Fig. 7 FTIR spectra of all samples.

Table 6 Thermal properties of control paste, geopolymer nano-composites and nano-clay (Cloisite 30B).

Sample	Residual mass at different temperatures (%)
	100 °C	200 °C	300 °C	400 °C	500 °C	600 °C	700 °C	800 °C
GP	97.1	91.1	89.7	89.0	88.6	87.8	87.7	87.5
GPNC-1	97.5	91.4	90.0	89.2	88.5	88.1	88.0	87.8
GPNC-2	98.1	92.1	90.6	89.8	89.0	88.7	88.6	88.4
GPNC-3	97.8	91.6	90.1	89.4	88.8	88.4	88.2	88.1
Nano-clay	98.6	98.2	97.3	78.7	75.4	73.5	72.6	71.5

Fig. 8 TGA curves of nano-clay (Cloisite 30B) and all samples.

Fig. 9 DTG curves of pure geopolymer and geopolymer nano-composites.