الفهرس 
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Abstract
Production of cement clinker is one of energy-intensive industry which requires a large amount of fuel. Recently many countries tend to use solid wastes as a source of energy in cement industry instead of fossil fuel or as a fraction of the fuel used in the production of cement clinker. The industry argues that the use of waste as alternative fuels has several positive impacts on sustainability, i.e. conservation of non-renewable energy sources, better energy recovery in waste, etc. In addition, the use of alternative fuels can help to reduce the costs of cement production.
The objectives of the present investigation are to study the characterization and thermal properties of eight types of different solid wastes to show their efficiency as refused derived fuel (RDF) sources. These solid wastes are divided into two categories according to their ash residue. The first category of solid wastes are; Tree trimmings (TT), Rubber waste (RW), Rice straw (RS) and municipal solid waste (MSW) which they are show percentage of ash residue after firing at 1000°C or 2 hours > 19 % and they characterized in this study as high ash content RDF sources (HARDF). While the second category of solid wastes are; paper waste (PAW), saw dust (SD), plastic waste (PLW) and cane waste (CW) which they are show percentage of ash residue after firing 2 hours at 1000°C less than 10 % so they characterized in this study as low ash content RDF (LARDF) sources. The characterization of these RDF sources done via determination of their elemental analysis, percentage of moisture contents (MC %), density, percentage of ash contents (ASH %) and caloric values (CV). Also the oxide compositions of the RDF sources was studied by X-ray fluoresce (XRF) analysis.
Various dry mixes are prepared using the Ordinary Portland cement clinker contaminated with 2 or 4 wt.% of RDF ashes residues (in case of low ash RDF) or 5 and 10 wt % wt.% of RDF ashes ( in case of high RDF wastes) to study the effect of the ashes residues on the clinker compositions. Finally the effect of addition of the RDF ashes on the physicochemical and the hydration characteristics of the hardened OPC pastes studied.
The hardened admixed OPC pastes were prepared using W/C ratio of 0.3 and tested for initial and final setting times. After that the hardened pastes hydrated for various time intervals of 1, 3, 7, 28 and 90 days. At each time interval, the hydrated pastes were tested for their compressive strength; then, the following studies were carried out on the ground dried specimens:
1- Kinetics of hydration products were studied by the determination of chemically combined (non-evaporable) water (Wn, %) and free lime (CaO, %) content at the different times of hydration.
2- Phase composition of the formed hydration product was investigated by means of X-ray diffraction (XRD).
The obtained results were divided into two parts:
For the high ash contents RDF solid wastes:
- The main compositions of the studied solid wastes are hydrocarbons with minor amine, sulfur and chloride contents. Rubber waste (RW) and Tree trimmings (TT) offer the highest carbon, sulfur and chloride contents. This predicts the highest carbon, sulfur and nitrogen oxides emission by using these wastes as source for RDF.
- Rubber waste shows the highest caloric value (CV) (8600 Cal. /g).while municipal solid waste (MSW), Tree trimmings (TT) and Rice straw (RS) showed caloric values varies between 3167 – 4200 Cal. /g.
- Addition of 5 and 10 wt. % of ash residues of high ash content RDF to OPC lead to reduce the setting times of the hardened pastes. This explained due to the nucleation effect of the RDF ashes particles, so they can act as active centers inside OPC matrix that favors the growth of the hydration products on them leading to acceleration of the hydration reaction.
- OPC pastes admixed with 5 and 10 wt.% of rubber wastes ashes (RW) show an improvement in the compressive strength values at almost hydration ages compared to the control OPC paste ( neat OPC).
- OPC pastes admixed with other RDF ashes (TT, RS and MSW) show higher compressive strength values than blank (neat OPC) during the early ages of hydration; up to 3 days and up to sometimes this extended to 7 days for tree trimmings (TT mixes).
-OPC mixes admixed with 5 and 10 wt. % of HARDF ashes showed lower Wn, % values and free lime, CaO% than the neat OPC mix at almost hydration ages.
- According to X-ray test, OPC pastes admixed with RDF ashes show the same hydration products as blank OPC mix indicating that mixing of Portland cement with RDF ashes does not change the hydration products.
For the low ash contents RDF solid wastes:
- The main compositions of the studied solid wastes are hydrocarbons with low amounts of sulfur and chloride contents. This indicates that these RDF wastes could be used in cement plant with high SO3 or Cl2 in their raw material.
- Plastic waste (PLW) shows the highest caloric values (CV) (9230 calorie/ g) and the paper waste (PAW) shows the lowest caloric values (3290 cal/ g) between the four RDF studied.
- The ash results from plastic waste (PLW) has the highest SiO2 content and the lowest CaO content; and paper waste (PAW) has the highest CaO content and the lowest SiO2.
-Addition of 2 and 4 wt. % of ash residues of low ash content RDF to OPC result in reduction of both initial and final setting times compared to OPC paste free of ash, mix B. Paper waste ashes (PAW) show the highest reduction in setting times while saw dust ashes (SD) shows the lowest reduction.
-OPC pastes admixed with 2 wt. % or 4 wt. % of ashes of low ash RDF sources show an improvement in the compressive strength values compared to the control OPC paste after 90 days of hydration.
-OPC mixes admixed with 2 and 4wt. % of LARDF ashes showed lower Wn, % values and free lime, CaO% than the neat OPC mix at almost hydration ages.
- According to X-ray test, OPC pastes admixed with low RDF ashes show the same hydration products as blank OPC mix indicating that mixing of Portland cement with RDF ashes does not change the hydration products.