Page 233 - Materials Chemistry, Second Edition

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Sustainable Industrial Design and Waste Management
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TABLE 6.5
Maximum Water Absorption Percentages for Construction Bricks and Tiles (Abou
Khatwa et al., 2005)
Application Standard specification Water absorption (%)
Industrial floor brick ASTM C410-60 1.5–12
Solid concrete interlocking ASTM C936-96 5
paving units
Pedestrian and light traffic ASTM C902-95 11–17
paving brick
Cement tiles ES 269-1974 12
Recycled plastic waste 0.64–1.6
composite material

units, compared to those produced by the composite material. It is evident
from the table that even mix 1 (20% sand, sieve 1, and temperature 185°C),
holding the highest average water absorption value over all the investigated
mixes of 1.6%, easily satisfies all the standard requirements for industrial floor
bricks, interlocks, paving bricks, and cement tiles. It is evident from Table 6.5
that the investigated plastic waste composite reveals superior water absorption
resistance when compared to cementitious materials. However, the values are
slightly higher than those expected for most plastics (less than 1% absorption).
This could be related to the presence of imperfections in the prepared speci-
mens, either in the form of cavities, minor waste constituents such as paper or
pores resulting from the use of sand as filler material.

Resistance to chemical reagents
To assess the serviceability of the recycled plastic material when exposed to
outdoor environment conditions, the ASTM standard practice D 543-95 (1998)
for evaluating the resistance of plastics to chemical reagents was employed.
Three reagents were selected for the tests, benzene, sulfuric acid (3%), and
sodium hydroxide solution (10%). Testing was conducted for 7, 14, and 28
day’s immersion.
Tables 6.6–6.8 list the average increase in weight over an immersion period
of four weeks for the three reagents. It is apparent from the results that the mate-
rial possesses excellent chemical resistance to acids and alkalis. The average
increase in weight after 28 days was 1.37% and 3.38% for the sulfuric acid and
the sodium hydroxide solution, respectively. However, the increase in weight
after seven days was nearly half the values for the total immersion time. On
the other hand, the increase in weight associated with the benzene reagent
was much higher starting at a 5.59% increase after the first seven days and
reaching 9.85% after 28 days. It is well known that most polymers exhibit
very high resistance to chemical attacks by acids and alkalis. However, they
are less resistive to organic solvents which react with the carbon atom chains