No abstract

In past studies, a powdery silica-based admixture was developed. It was obtained by applying the heat treatment to inorganic waste, such as waste glass and fly ash containing a large amount of silica. The silica-based admixture has also been recognized as an effective solidifying material when it is mixed with blast furnace slag. The colloidal silica and calcium silicate hydrates (CSHs) produced in the process exhibit not only a higher mechanical strength than cement-based solidification material, but also excellent properties such as the expectation of a delayed effect of the solidification time. Therefore, it is considered to be applicable to ground improvement works. In this study, in order to investigate the usefulness of a silica admixture and blast furnace slag solidifying material and the solidifying mechanism by means of a solidification material, an energy dispersive X-ray analysis (EDS analysis), a scanning electron microscope observation (SEM observation) and an X-ray diffraction analysis (XRD analysis) were implemented to examine soils improved by the solidification material.

ABSTRACT:In a series of studies, the authors have developed a powdery silica-based solidification material composed of heat-treated inorganic solid wastes with a high content of silica products (such as waste glass and waste fly ash) mixed with alkali aids. This material is most suitable for use with iron or steel slag, such as that which comes from a blast furnace or a steel-making process. The powdery silica-based solidification material mixed with iron and steel slag can be expected to exhibit higher mechanical strength and more predominant characteristics than a powdery cement-based solidification material. In this study, the solidification mechanism for the mixture of the silica-based solidification material, blast furnace slag and water is clarified from the viewpoints of chemistry and mineralogy by conducting X-ray diffraction analysis, X-ray fluorescence spectrometry and inductively coupled plasma spectroscopy.

Past research has developed a powdery silica-based admixture of inorganic waste containing a large amount of silica component such as a waste glass and a fly ash. It is effective as a solidifying material by mixing with a blast furnace slag. In addition, it can be expected to have superior characteristics as well as high strength as compared with cement-based solidifying material, and it is effective to adapt to soil improvement. In this study, in order to elucidate the solidification mechanism, energy dispersive X-ray analysis (EDS analysis), scanning electron microscope observation (SEM observation) and X-ray diffraction analysis (XRD analysis) have been conducted. In addition, in order to control the solidification time, blast furnace cement or normal Portland cement or calcium hydroxide (Ca(OH)2) is partially or completely substituted for the blast furnace slag which is the raw material of the mixed solidifying material. On the contrary, the uniaxial compression test, and the flow test are carried out to investigate the usefulness and solidification mechanism in view of practical application.

Water-swelling material (WSM) is a fl uid sealant obtained by blending high-absorbency polymer, a fi ller, and a solvent by using a synthetic resin elastomer as the base material. In this research, we studied experimentally the composition of WSM, the extent of swelling, the strength of the WSM and the long-term performance of the swelling material used as a jointed water cutoff treatment material at waste landfi ll sites. One of the results was that adjusting the degree of etherifi cation of the high-absorbency polymer, which is a component of the WSM, and the resin content of the synthetic elastomer contributed to improvement of the swelling of the sealant and the strength of the swelling material. Further, in long-term tests, the strength of the WSM tended to become stabilized and it was confi rmed that it had suffi cient pressure resistance for use in coastal landfi ll sites, where its application as a water cutoff treatment material is being considered.

No abstract

No abstract

An evaluation method that can express the local leakage of leachate from joint sections in steel pipe sheet pile (SPSP) cutoff walls is discussed in this study. In particular, the evaluation of environmental feasibility (containment of leachates containing toxic substances) considering a three-dimensional arrangement and hydraulic conductivity distribution of the joint sections in the SPSP cutoff wall is compared with an evaluation that uses the equivalent hydraulic conductivity. This equivalent hydraulic conductivity assumes that the joint section and the steel pipe are integrated; therefore, the hydraulic conductivity is substituted with a uniform permeable layer. However, in an evaluation that employs the equivalent hydraulic conductivity, it is diffi cult to consider the local leakage of leachate containing toxic substances from the joint sections in the SPSP cutoff wall. It was established that evaluations of the environmental feasibility of SPSP cutoff walls with joint sections must take into account the local leakage of leachates containing toxic substances from the joint sections. Also, it was clarifi ed that technologies that lower the hydraulic conductivities of joint sections in SPSP cutoff walls and also facilitate the use of sparser joint arrangements contribute signifi cantly to increasing the environmental feasibility of SPSP cutoff walls at landfi ll sites.Key words Coastal landfi ll site · Environmental feasibility · Local leakage of leachate · Steel pipe sheet pile · Vertical cutoff barrier J Mater Cycles Waste Manag (2009) 11:55-64