Civil Engineering Reference
In-Depth Information
Table 4.11 Reduction of compressive strength of cement mortar and concrete (28-day) due to
the substitution of natural aggregates by plastic aggregates
Reference
Types of
substitution
Reduction in compressive strength
for substitution level (%) of
3
5
10
15
20
30
45
50
75
100
Batayneh et al.
(
2007
)
Fine/PET
23
72
Frigione (
2010
)
Fine/PET
\2
Hannawi et al. (
2010
)
Fine/PET
9.8
30.5
47.1
69
Fine/PC
6.8
27.2
46.1
63.9
Kou et al. (
2009
)
Fine/PVC
9.1
18.6
21.8
47.3
Saikia and de Brito
(
2010
)
Fine flakes/PET
13.8
28.5
41.8
Coarse flakes/
PET
28.3
47.9
64.4
Fine pellet/PET
12.2
14.6
22.4
Fraj et al. (
2010
) observed a 57-78 % lower 28-day compressive strength of
concrete with 8-20 mm rigid PUR foam as aggregate compared to a control
concrete, due to the lightweight nature of the modified concrete as well as the low
mechanical properties and the high porosity of PUR-foam aggregates. Prewetting
the PUR-foam aggregates further lowers the compressive strength due to an
increase in the mortar's porosity. Using a superplasticizer along with increasing
cement content, on the other hand, increases compressive strength. The use of
superplasticizer made it possible to decrease cement content by 15 % and to
increase PUR-foam content by 33 % compared, with an acceptable reduction
(15 %) of compressive strength.
Mounanga et al. (
2008
) reported that water curing concrete with PUR-foam
aggregates and NA slightly improved the compressive strength compared to dry
curing. For conventional lightweight concrete, the increase in strength was about
69 % and this improvement for concrete with 13.1, 21.2 and 32.7 % by volume of
PUR-foam aggregates was 39, 34 and 5 %, respectively.
Kan and Demirboga (
2009
) reported that lightweight concrete with heat-treated
expanded polystyrene (MEPS) waste aggregates exhibited a compressive strength
40 % higher than that of concrete with vermiculite or perlite aggregates at equal
concrete density. However, the compressive strength of concrete with MEPS
aggregates decreased with increasing addition of aggregates. The development of
compressive strength of concrete with 100 % MEPS aggregates at 90 days with
respect to that at 7 days was about 83 % whereas it was 69 % for concrete with
25 % MEPS aggregates, which might be due to the high heat of hydration of the
former type of concrete because of low specific thermal capacity of the MEPS
aggregates. The compressive strength of concrete with coarse MEPS aggregates
was lower than that of concrete with fine MEPS aggregates as the coarse MEPS
aggregates had higher porosity, and therefore were more brittle and weaker than
the fine MEPS aggregates.
