Granulated Coal Ash Research Articles

石炭灰造粒物による硫化物イオンの除去

Hydrogen sulfide is highly toxic and fatal to benthic organisms. It also depletes dissolved oxygen and generates blue tide when oxidized. Therefore, it should be controlled to maintain healthy ecosystems. The purpose of this study is to evaluate the removal of hydrogen sulfide from seawater using granulated coal ash produced from coal thermal electric power stations. The batch experiments revealed that the removal kinetics of hydrogen sulfide were expressed as a first-order rate equation and that the adsorption maximum of hydrogen sulfide was 108 mg-S · g-1. The K-edge X-ray adsorption fine structure spectra of sulfur adsorbed by granulated coal ash indicated that hydrogen sulfide was adsorbed as sulfur and formed FeS2 when the hydrogen sulfide concentration was high. Results imply that applying granulated coal ash to organically enriched sediment can effectively reduce the concentration of hydrogen sulfide in interstitial water.

Cyclic Shear Characteristics of Soil Mixed with Granulated Coal Ash

**** With the aim of using granulated coal ash mixed with natural sand as geo-material, laboratory experiments were performed on the composite material to understand its cyclic shear characteristics. A series of undrained cyclic shear tests was performed on loose samples of the composite material to assess the effect of the mixed proportion on the cyclic shear characteristics. The tests revealed that (1) the composite material in which the proportion of granulated coal ash mixed was about 50% or more has cyclic shear strength almost equal to that of pure granulated coal ash, irre- spective of the type of natural sand used ; (2) The cyclic shear strength of the composite material increased when the particle strength of the natural sand was low ; (3) When the composite material consisted of about 30% natural sand, the initial shear modulus G0 of the mixture was almost equal to that of granulated coal ash. Based on these test results, it was shown that when the mixed proportion of granulated coal ash was about 50%, the cyclic shear charac- teristics and dynamic deformation characteristics of the composite material were almost similar to those of pure gran- ulated coal ash.

石炭灰造粒物を用いた沿岸底質環境改善材開発のための基礎的研究〜栄養塩溶出試験およびＳｋｅｌｅｔｏｎｅｍａ ｃｏｓｔａｔｕｍの増殖試験〜

The Characterization of cement-granulated coal ash was carried out for the purpose of remediation of organically rich sediment by controlling the nutrient balance of ecosystems. The granulated coal ash used in this study is composed of SiO2, CO3, Al2O3, CaO with quartz and aluminum silicate as the main phases. Moderate dissolutions of phosphate, silicate and calcium were observed. This may be useful for the neutralization of the acidified sediment and effective for controlling the balance of nutrients in coastal seas. Although the growth of the diatom S. costatum was inhibited under the batch culture condition owing to pH increase, such a pH increase would not occur under natural conditions because of magnesium precipitates and carbonate equilibrium.

AN EXPERIMENTAL STUDY ON APPLICATION OF GRANULATED COAL ASH SLAG TO CONCRETE AGGREGATE

Aggregate test, mortar test, concrete test and manufacture test of secondary concrete products were executed in order to examine whether the coal ash slag can be used as a fine aggregate for concrete. As a result of these tests, the coal ash slag turned out to be similar to the pit sand in ingredient composition without any toxic chemicals to be eluted and after being subject to grinding process, it satisfied the quality requirements as a fine aggregate for concrete. The greater the slag substitution rate is, the greater the bleeding rate of the concrete using coal ash slag becomes. However, the concrete using coal ash slag has almost equivalent the compressive strength and tensile strength to those in which the land sand is used. Concerning the characteristics related to durability, such as the carbonation rate and freeze-thaw resistance, it did not show any difference from the concrete using the land sand. With these results, it can be concluded that the granulated coal ash slag has a quality to be applied to structural concrete.

地盤材料としての造粒石炭灰の粒子特性

The applicability of a granulated coal ash to construction material (geomaterial) was investigated to promote the recycling. Especially, the characteristics of the individual particle such as shape, physical properties and strength were measured. The features of the granulated coal ash were clarified in comparing with the result of the natural sands. The following conclusions were obtained. (1) The aspect ratio Ar of the granulated coal ash is lower and roundness coefficient Rc is higher than those of natural sands. (2) The void ratio of the granulated coal ash become high because of larger roundness coefficient Rc and containing intragranular voids. (3) It become clear that single particle crushing strength of granulated coal ash is lower than that of natural sands, however, its strength increase as the curing days, in the observation for 900 days. (4) It is found that single particle crushing strength of granulated coal ash doesn't depend on the particle size. (5) It is confirmed that the Weibull modulus mf of granulated coal ash is larger than that of natural sands, and the variability of maximum crushing strength is small. (6) It is found that the Weibull modulus mf doesn't depend on the particle size and curing days.