A method for preparing ceramsite by using municipal sludge as raw material, including the following specific steps: drying; preparing ingredients including raw sludge, fly ash, kaolinite, steelmaking slag, zeolite, hematite, calcareous shale, waste incineration fly ash, Fe.sub.2O.sub.3, waste glass, calcium carbonate, sodium lauryl sulfate, and sodium benzoate; mixing and stirring uniformly, and putting the stirred materials into a granulating machine for granulation; drying and preheating the material pellets after granulation, and then quickly transferring to a sintering device for first sintering at a low temperature and then sintering at a high temperature; crushing large chunks of the cooled materials; and separating and screening the crushed materials. The method of the present invention reduces the generation of the large chunks of the cooled materials in the obtained ceramsite, thereby reducing the subsequent crushing work and saving energy consumption accordingly.

A hydratable cement composition which will bond to both asphalt and cementitious substrates is supplied for the repair of various surfaces. The composition comprises of a combination of Portland cement, calcium sulfoaluminate cement or calcium aluminosilicate, and an alkali metal salt activated pozzolonic powder, wherein the Portland cement content of the hydratable portion of the composition is greater than 20%. The composition is free from latex bonding agents and calcium aluminate. The composition is mixed with water to form a typical cement, mortar, or concrete consistency, placed and allowed to cure. The result is a self-adhering patch to damaged surfaces. The hydratable cement composition may also be used to fabricate items of original construction by casting into molds or forms.

A hydratable cement composition which will bond to both asphalt and cementitious substrates is supplied for the repair of various surfaces. The composition comprises of a combination of Portland cement, calcium sulfoaluminate cement or calcium aluminosilicate, and an alkali metal salt activated pozzolonic powder, wherein the Portland cement content of the hydratable portion of the composition is greater than 20%. The composition is free from latex bonding agents and calcium aluminate. The composition is mixed with water to form a typical cement, mortar, or concrete consistency, placed and allowed to cure. The result is a self-adhering patch to damaged surfaces. The hydratable cement composition may also be used to fabricate items of original construction by casting into molds or forms.

A cementitious composition of one embodiment, according to the present teaching, includes, but is not limited to, a Portland cement, and at least one other cement from a group comprising, but not limited to, calcium sulfoaluminate cement, a calcium aluminosilicate cement, and calcium aluminate, wherein the Portland cement has a content of at least 20 percent based on the total weight of the non-Portland hydratable cement powder, wherein the cementitious composition bonds to asphalt.

A cementitious composition of one embodiment, according to the present teaching, includes, but is not limited to, a Portland cement, and at least one other cement from a group comprising, but not limited to, calcium sulfoaluminate cement, a calcium aluminosilicate cement, and calcium aluminate, wherein the Portland cement has a content of at least 20 percent based on the total weight of the non-Portland hydratable cement powder, wherein the cementitious composition bonds to asphalt.

A low strength backfill material having a 28 days compressive strength less than approximately 2.0 MPa is provided. The backfill is suitable for use in areas with dense underground utilities due to its high excavatability and good thermal conductivity. The backfill includes a cementitious binder of approximately 1 weight percent to approximately 10 weight percent and fine aggregates in an amount of approximately 40 to approximately 75 weight percent. Filler is provided at 20 microns to approximately 100 microns for high flowability. A density-controlling agent of 0.0001-5 weight percent is used such that the density of a cured backfill material is approximately 1600 kg/m.sup.3 to 2000 kg/m.sup.3. Thermally conductive particles having a size range of approximately 0.01 microns to 500 microns in an amount of approximately 0.1 to 10 weight percent are evenly dispersed throughout the backfill.

A low strength backfill material having a 28 days compressive strength less than approximately 2.0 MPa is provided. The backfill is suitable for use in areas with dense underground utilities due to its high excavatability and good thermal conductivity. The backfill includes a cementitious binder of approximately 1 weight percent to approximately 10 weight percent and fine aggregates in an amount of approximately 40 to approximately 75 weight percent. Filler is provided at 20 microns to approximately 100 microns for high flowability. A density-controlling agent of 0.0001-5 weight percent is used such that the density of a cured backfill material is approximately 1600 kg/m.sup.3 to 2000 kg/m.sup.3. Thermally conductive particles having a size range of approximately 0.01 microns to 500 microns in an amount of approximately 0.1 to 10 weight percent are evenly dispersed throughout the backfill.

Provided are compositions and methods thereof that may include Portland cement, a melamine, and alumina. The compositions may further include silicon dioxide, supplementary cementitious material, polymer resin(s), hydrophobizers, preservatives, film-forming assistants, dispersants, foam stabilizers, defoamers, pigments, dyes, water, or combinations thereof. Typically, the compositions are coatings that may be applied to restore and preserve asphalt and cement road surfaces and pavements.

Provided are compositions and methods thereof that may include Portland cement, a melamine, and alumina. The compositions may further include silicon dioxide, supplementary cementitious material, polymer resin(s), hydrophobizers, preservatives, film-forming assistants, dispersants, foam stabilizers, defoamers, pigments, dyes, water, or combinations thereof. Typically, the compositions are coatings that may be applied to restore and preserve asphalt and cement road surfaces and pavements.

The present invention provides an apparatus and a method for producing cement through flue gas desulfurization, and specifically provides an apparatus and a method for simultaneously producing magnesium sulfate cement during a magnesium oxide based flue gas desulfurization process. The apparatus of the present invention includes a flue gas desulfurization equipment, a concentration equipment, a crystallization equipment, a centrifugation equipment, a drying equipment, a waste ash supplying equipment, a slag material supplying equipment, a mixing equipment, etc. By adopting the apparatus and method of the present invention, the problems in the present conventional cement production such as high energy cost, severe damage to the environment and so on can be solved, and the problems like high production cost of ordinary magnesium sulfate cement and high transportation cost of supplies thereby causing incapability in a large scale market spreading and application can also be solved.