Environmental Engineering Reference
In-Depth Information
Lingling et al., (2005); Guler et al., (1995); Kalwa and Grylicki, (1983)
showed that fly ash can increase the compressive strength of bricks. Also,
work conducted by Lingling et al., (2005) showed that addition of 50% of
pulverised fly ash resulted in high compressive strength (985 kg/ cm
2
) as
compared to bricks developed from clay alone (169 kg/ cm
2
). However, this
work showed no improvement in compressive strength with CCRs. Although,
there are several advantages due to CCRs utilization including reduced
plasticity, no efflorescence and reduced weight and fracture and inhibits toxic
substances in jarosite waste under verification. It was observed that
incorporation of clay about 25 % significantly contributed to improve the
quality of bricks. Jarosite sintering behavior is strongly dependent on the
composition, quantity and constituents impurities, leading to the formation of
transitory liquid phases which assist the densification of the main crystalline
phases, hematite and magnetite or zinc ferrite. Nevertheless, 1:1 ratio of
jarosite waste-clay along with 15-30 % of PCCRs application resulted in 37-50
kg/cm
2
compressive strength as an intermediate condition to meet the quality
standard (IS 2248:1992) for use in construction applications safely (Figure 9 a)
as well as toxic elements leachate concentration in jarosite waste composites
were within the prescribed USEPA limits.
3.2.2. Effect of Jarosite waste and CCRs on Water Absorption, Shrinkage
and Density of s/s Sintered Clay Bricks
The preliminary experimental results showed that the water absorption
capacity of jarosite composite bricks varies from 14 -26 %. Increase in
concentration of jarosite waste decreased water absorption capacity. Minimum
water absorption (13.27 %) was obtained when 15% CCRs was used along
with a 4:1 jarosite waste to clay ratio (Figure 9 d). However, maximum
shrinkage (~38 %) could be seen with this concentration, which is expected
because the jarosite has shrinking and swelling properties. Addition of CCRs
decreased the shrinkage and minimum shrinkage (8.1%) was obtained with
45% CCRs with a 1:1 ratio of jarosite waste to clay (Figure 9a). This was
probably due to the physical and morphological characteristic of the CCRs;
during firing at high temperature, there is considerable increase in the
formation of liquid phase due to the fusion of clay minerals and partial
dissociation of quartz phase (silica to glassy phase). This reduces the porosity
in the fine porous of the products under capillary tension force and increases
the shrinkage (Qrts et al, 1993; Adcock et al., 1959; Escardino et al., 1985;
Amoros, 1987). Due to firing, the mechanism of reaction leads to nucleation
and growth of new mineral (Riccardi et al., 1999) resulting improved quality
Search WWH ::
Custom Search