Page 236 - Materials Chemistry, Second Edition

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Recycling of Municipal Solid Waste Rejects
segregation decreases with increasing temperature and decreasing sand con-
centrations. Clustering of sand particles depends on the concentration of the
filler employed as well as its size; the clustering tendency increases by increas-
ing the filler concentration and decreasing the particle size.
The compressive strength was 7.25% higher than the ASTM limit for
pedestrian and light traffic paving bricks; however, it failed to meet the ASTM
limit for solid concrete interlocking paving units. The modulus of rupture was
also higher than the standard limits for clay bricks and industrial floor bricks.
The abrasion resistance of the composite material was 70% higher than the
Egyptian standard limit for cement tiles allowing for its use in tiling applica-
tions. The composite material exhibited very low density and water absorption
rate in comparison to cement tiles and paving units. However, such absorption
rates may be detrimental in applications where the material is subjected to
tensile loads since water is a plasticizer for many polymers and can result in a
decrease in the elastic modulus. Water can also swell the polymeric waste cre-
ating stress concentrations. The softening temperature of the composite
material was much higher than the maximum expected summer service tem-
peratures. In addition, the material showed high chemical resistance to acidic
and alkaline attack. Based on the compressive strength, flexural strength,
abrasion, chemical resistance, and leaching tests of the composite material, it
can be safely used to manufacture paving bricks, large tiles, or sheets for use
in industrial facilities where physical requirements are not of great impor-
tance. The major problem with the composite material remains its suscepti-
bility to environmental attack by ultraviolet radiation and microorganisms
and further investigation of this matter together with tests for the leaching of
organic compounds should be conducted.

6.5 Manhole

A manhole or maintenance hole, sometimes called an inspection cover is the
top opening to an underground vault used to house an access point for making
connections or performing maintenance on underground and buried public
utility and other services including sewers, telephone, electricity, storm drains
and gas. It is protected by a manhole cover designed to prevent accidental or
unauthorized access to the manhole. Manhole base and cover are usually made
out of case iron or Reinforced Fiber Plastic (RFP) or can be produced out of
MSW rejects. The main advantages of manholes made out of MSW rejects
are less cost, less energy consumption, durability and their resistance to acid.
The weight can be adjusted by adding sand to the mix. Sand will increase the
required specific weight up to a certain percentage (28%) to avoid any strength
impact. The carrying load for a 40 cm manhole is 1.8 tons, which is slightly
higher than FRP manholes and can be increased by adding steel bars.
A manhole cover is a removable plate forming the lid over the opening
of a manhole, to prevent someone from falling in and to keep unauthorized