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use of SSA in building materials, such as with raw materials in the fabrication of
clinker and ceramics.
Lin and Lin (2004) and Lin et al. (2005) developed three types of hydraulic
cements incorporating SSA and slag from steelworks (ferrate) as a partial replace-
ment of clay, silica, alumina and iron oxide in raw materials for PC production. A

pilot-scale study was conducted, heating it up to 1400 C for 6 h in a clinkerisation
process using a simulated incineration and smelter. Results showed that eco-cement
A (6.47% SSA) was most similar in compressive strength to PC, while eco-cement
B (4.86% SSA) showed early strength development.
Tay et al. (1991) studied the use of dewatered sludge clay mixtures after inciner-
ation as a lightweight coarse aggregate. The properties of the obtained aggregates,
as well as concrete, were also studied. The strength of the concrete with the
lightweight aggregate increased along with the percentage of clay after 28 days of
curing. Compressive strength results agreed with BS 8110 for structural concrete.
A bench-scale was developed to determine whether SSA could be used in brick
making clay mixtures in order to reduce SSA that is landfilled (Trauner, 1993). The
study concluded that bricks with even 30% by weight SSA addition agreed with
ASTM standard specifications regarding compressive strength.
Chen and Chiou (2006) also used SSA as a main material to produce foamed
lightweight materials, investigating how sintering temperature affected the macro/
micro properties. Firing tests were conducted at different temperatures, and it was
shown that the SSA/cement foamed samples (20/80, 30/70 and 40/60 ratios were
tested) presented better performance than pure cement foamed paste (Fig. 5.13).
Large volume shrinkage (25%) was measured with increasing firing temperature

from 20 to 1093 C. However, because the sintering effect was favoured by SSA,
the 20/80 and 30/70 samples showed an increase in compressive strength from

600 C (8.5 9.0 MPa) to 1093 C (11.0 13.5 MPa).

Figure 5.13 Appearance changes for foamed pastes after firing at different temperatures: (A)
pure cement paste (W/S 5 0.35), and (B) C/SSA 5 30:70 (W/S 5 0.6) (Chen and Chiou,
2006). SSA, Sewage sludge ash.