dc.description.abstract | The high chlorine content in the incinerator ash has limited the use of it as part of the raw material for producing ecocement. It is possible, however, to
calcine chlorine-containing raw meal into calcium chloroaluminate, one cement hydrate mineral, which can not only fix the chlorine in it but also function just
like the other cement clinker minerals. This study investigated the feasibility of producing ecocement, using chlorine-containing incinerator ash, marble sludge,
and sewage sludge as raw materials, and the hydration characteristics of the resulting cement clinkers.
In the design of the raw materials incorporated the tested wastes, a computational model was established on the basis of cement modulus to formulate possible range of the compositions of raw meals with tested chlorine contents in the raw materials verifying from 1.5-37.8 %(w/w). The calcination of raw materials into cement clinker minerals were examined and the hydration characteristics of the resultant ecocements and the engineering properties of their pastes were studied including the compressive strength, speciation and the degree of hydration, as compared to those of ASTM type I ordinary Portland cement
(OPC).In this study, the amount of free CaO decreased to less than 1 %(w/w) and the LOI for all tested meals met the eco-cement criteria. In conclusion, the formation of major cement clinker minerals such as C3S, C2S, C3A, C4AF and C11A7CaCl2 were confirmed in all the eco clinkers.
Ecocement produced with was washed incinerator ash, marble sludge, and sewage sludge as raw meal (referred to as ordinary ecocement, OEC) showed both the initial and the final setting times were slightly shortened or similar to
those of OPC. However, ecocement produced using chlorine-containing incinerator ash, marble sludge, and sewage sludge as raw meal (referred to as chlorine-containing ecocement, REC) exhibited both the initial and the final
setting times were significantly shortened with the increasing chlorine content in the RECs.
On the other hand, the compressive strength development of OEC samples showed slightly decreased as compared to that of OPC samples, whereas the REC samples showed a reversed trend. The development of compressive strength
outperformed those of OPC samples during the early 28 days, showing the contribution by the hydration of the C11A7CaCl2 which characterizes the rapid setting and strength development of the REC samples.
The results of XRD analysis confirmed that OPC, OEC and REC showed common hydration products of CH and CSH gel, the OEC and REC exhibited the presence of hydration product, (Mg(OH)2), which were supposed contributed by
the use of marble sludge in the raw meals.
The FTIR analysis of the OEC and REC pastes cured at 90 days containes three wavenumbers: the first wavenumber was mainly due to the Si-O bonds of calcium silicate hydrates (CSH); the second wavelength represents the C-O
bonds of the calcium carbonate (CaCO3); and the third wavelength the decomposition of calcium hydroxide (Ca(OH)2). The results indicate the hydration products of the tested OEC and REC samples. The hydration products of both OEC and REC pastes, as analyzed by 29Si
NMR techniques showed that Q0 peak decreased and O1 peake increased with increasing curing age. And the hydration degree and length of the linear polysilicate anions, as estimated on the basis of the Q0 and Q1 peaks, showed the
increasing trend with increasing age.
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