A process for reforming the fly ash, including the heating step that heats a raw fly ash powder containing the unburned carbon at a temperature of 780 to 1000 C. to decrease the amount of the unburned carbon contained in the raw fly ash powder; and the cooling/classifying step that introduces the heat-treated fly ash in a state of being maintained at a high temperature as obtained through the heating step into a cooling/classifying apparatus so that the fly ash is separated into a fine grains and a coarse grains; wherein the cooling/classifying apparatus 3 used in the cooling/classifying step has a basic structure in which the gas flow for classification is introduced from the lower side and the gas flow Z for cooling/classification introduced into the apparatus is then discharged from the upper side; the heat-treated fly ash is brought into contact with the gas flow Z for cooling/classification, the fine grains contained in the heat-treated fly ash is lifted up and discharged out of the apparatus while the coarse grains contained in the heat-treated fly ash is allowed to stay in the apparatus 3, and the fine grains and the coarse grains are separated and cooled; and the fine grains discharged from the apparatus 3 is recovered by using a dust-collecting apparatus, and the coarse grains is recovered from the apparatus 3.

A process for producing a modified fly ash comprising the steps of providing, as a raw material, the raw fly ash discharged from a pulverized coal combustion boiler; classifying the raw fly ash into a crude powder and a fine powder; removing the unburned carbon contained in the crude powder by heating the crude powder at a temperature in a range of 500 to 1000 C.; and mixing together the crude powder from which the unburned carbon has been removed and the fine powder to obtain a modified fly ash.

A process for reforming the fly ash, including the heating step that heats a raw fly ash powder containing the unburned carbon at a temperature of 780 to 1000 C. to decrease the amount of the unburned carbon contained in the raw fly ash powder; the classifying step that introduces the heat-treated fly ash containing the unburned carbon in decreased amounts obtained through the heating step into a classifying apparatus in the state of being heated at a high temperature so as to separate the fly ash into a coarse powder and a fine powder; the fine powder recovering step that recovers the fine powder of the heat-treated fly ash obtained through the classifying step by using a dust-collecting apparatus; and the milling step that mills the coarse powder of the heat-treated fly ash obtained through the classifying step until a 45 m sieve residue becomes not more than 34% by mass, and then recovers the milled powder.

A plasterboard includes a first layer of plaster and a second layer of plaster, wherein the first layer includes activated carbon; the second layer includes a scavenging agent, wherein a content of scavenging agent in the first layer, expressed as percentage by weight of dry matter, is less than a content of scavenging agent in the second layer, and wherein the second layer is free of activated carbon.

A plasterboard includes a first layer of plaster and a second layer of plaster, wherein the first layer includes activated carbon; the second layer includes a scavenging agent, wherein a content of scavenging agent in the first layer, expressed as percentage by weight of dry matter, is less than a content of scavenging agent in the second layer, and wherein the second layer is free of activated carbon.

A plasterboard includes a first layer of plaster and a second layer of plaster, wherein the first layer includes activated carbon; the second layer includes a scavenging agent, wherein a content of scavenging agent in the first layer, expressed as percentage by weight of dry matter, is less than a content of scavenging agent in the second layer, and wherein the second layer is free of activated carbon.

The present invention provides a method for reforming coal ash, including classifying coal ash having 10% by mass or more of a residue on a 45 m sieve by using a forced vortex centrifugal type classifying apparatus, under a condition that the residue on a 45 m sieve of the coal ash after the classifying becomes in a range of 1% by mass or more and 8% by mass or less.

There is provided a method for reforming unburned carbon-containing coal ash of the present invention, including: a receiving process of measuring L value and b value of unburned carbon-containing coal ash in a Lab color order system and sorting unburned carbon-containing coal ash of which the L value is 54 or more and the b value is 2 or more and 10 or less; and a classifying process of classifying the unburned carbon-containing coal ash sorted in the receiving process under a condition that a residue on a 45 m sieve of reformed coal ash which has been reformed by classification is 8% by mass or less.

A process for producing a modified fly ash comprising the steps of providing, as a raw material, the raw fly ash discharged from a pulverized coal combustion boiler; classifying the raw fly ash into a crude powder and a fine powder; removing the unburned carbon contained in the crude powder by heating the crude powder at a temperature in a range of 500 to 1000 C.; and mixing together the crude powder from which the unburned carbon has been removed and the fine powder to obtain a modified fly ash.

A process for preparing whitened fly ash includes the steps of: (a) subjecting fly ash to a size classification step to obtain size classified fly ash having a particle size such that at least 90 wt % has a particle size of from 44 ?m to 250 ?m; (b) optionally, contacting the size classified fly ash from step (a) with water to form a slurry, wherein the slurry has a solid content of less than 40 wt %; (c) subjecting the slurry obtained in step (b) to an exhaustive magnetic separation step to form magnetically treated fly ash, wherein the exhaustive magnetic separation step includes a first magnetic extraction step and a second magnetic extraction step, wherein the second magnetic extraction step is carried out at a higher magnetic field strength than the first magnetic extraction step; and (d) subjecting the magnetically treated fly ash obtained in step (c) to milling to form whitened fly ash.