Page 420 - New Trends in Eco efficient and Recycled Concrete

374 New Trends in Eco-efficient and Recycled Concrete

were added to GC the strength loss was significantly reduced: the ternary blended
precursor [coffee grounds (CG)/MK/BFS] yielded more stable N A S H and
C A S H gels.
B˘ ad˘ anoiu et al. (2015a,b) studied the stability of activated mixtures of GC and
RM. The addition of RM as aluminium supplier for forming stable N A S H gel
did not show great advantages. The replacing of 25% of GC by RM led to produc-

ing systems with 15 MPa after 3 days at 60 C curing. Samples stored for 4 days

more at 20 C slightly increased the strength (20 MPa) (B˘ ad˘ anoiu et al., 2015a).
Mortar specimens stored under water for 28 days showed a decrease in 30% 40%
strength, in a similar way to that found for plain GC-activated mortar.
Hao et al. (2013) activated MK-based geopolymers by replacing 0% 40% with
solar panel glass. The mixes were reacted with a mixture of sodium hydroxide and
silicate (SiO 2 /Na 2 O 5 3.2). Several S/L ratio pastes (0.4 1.0) were prepared and
cured at 30 C for 1, 7 and 28 days. In general, compressive and flexural strengths

dramatically decreased for high replacement rates (20% 40%), while 10% contain-
ing GC paste yielded similar strengths than those found for plain MK geopolymers.
The best behaviour was obtained for samples with a S/L ratio of 1.0.
Alkali-activated borosilicate inorganic polymers were prepared by the alkali acti-
vation of waste glass powder with a NaOH/borax solution (Al-Saadi et al., 2017).
The materials presented an intumescent behaviour due to the heat exposure.
Increase in the porosity was achieved when borax was present in the mixture
(Fig. 13.10). Additionally, the intumescence was reached for lower temperatures
with borax.
Kourti et al. (2010, 2011a,b) studied the geopolymerisation of air pollution con-
trol (APC) glass. APC residues were treated by DC-plasma technology by combin-
ing APC with glass-forming additives. An inert glass from a hazardous point of
view was formed, containing 41.10 SiO 2 , 14.78% Al 2 O 3 and 32.59% CaO as the
main components (Kourti et al., 2010). The APC glass reacted (Kourti et al.,
2011b) with NaOH/Na 2 SiO 3 solution and the geopolymer yielded 110 MPa in com-
pression mode and 10.5 MPa in flexure mode after 28 days of curing. After 92

Figure 13.10 SEM micrographs of heated GC geopolymers: left, NaOH-activated at 650 C;
right NaOH/borax activated pastes at 500 C(Al-Saadi et al., 2017). GC, Glass cullet.