Civil Engineering Reference
In-Depth Information
100
80
60
40
20
B1
B2
B3
T1
T2
0
1
3
7
28
90
Age (days)
4.7
Lime fixed over time by fired clay material.
lime fixed in the 1-day specimens may be as high as 40% of the total lime
available under the most favourable (finest material) conditions and 5%
in the least (coarsest material). These results highlight the importance of
fineness in early age specimens. Over time, lime fixation tends to even out,
with similar 90-day results for all the samples. These findings indicate that
the firing temperature used to manufacture these materials (around 900 °C)
suffices to activate the pozzolanic properties of clay. Note that these fired clay
materials behave much like the most active natural pozzolans and as MK.
The effect of including fired clay waste in mortars was studied for this
review by running mechanical strength trials and comparing the results to
the findings for standard mortar. The waste was used as a pozzolan at a
cement replacement ratio of 15%. The fired clay waste used for the trial was
obtained by mixing ground brick and roof tile ground to a Blaine fineness
of 3500 cm
2
/g.
The findings for bending and compressive strength in percentage of
the values for the control mortar (with no fired clay additions) in 24-hour
and 28-day specimens are shown in Fig. 4.8. The 24-hour bending and
compressive strength values were similar in the test and control specimens.
The 28-day values were slightly lower than in the control, however, but in
all cases, the percentage decline was smaller than the cement replacement
ratio. This is an indication that these waste materials act as pozzolans and
contribute to mechanical strength. The above studies confirm that additions
have a beneficial effect on cement characteristics, since they contribute to
enhancing mechanical strength in the medium to long term.
In this same vein, i.e. the reuse of fired clay industry waste, Toledo et al.
(2007) studied material from plants in Brazil and Velosa and Cachim (2009)
a residue from expanded clay production. Both teams confirmed that this
waste is apt for use as a pozzolanic addition in concrete with a hydraulic
