| Budget Amount *help |
¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 1994: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1993: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
The amount of muddy soil such as hedoro from construction sites has been increasing, and some of them has been used as contruction material. However, the annual amount of unused construction waste was 76,000,000t in 1990, and about 20% of it was polluted sludge. Various inductrial wastes also have the same problem. It is very important to reuse the soil and waste, from the viewpoint of natural resource preservation and environmental impact mitigation.
The purpose of this study is to improve the trafficability or earth-moving property and to increase the strength of muddy soil which is high in water content and organic matter. In order to achieve these objectives, a hardening agent Portland cement and the admixture were added to the muddy soil, and their effects investigated. The used admixtures are three types of industrial waste (concrete powder, paper sludge ash and coal fly ash), and one natural material (granular bentonite).
The obtained results are summarized as follows :
(1) It is m
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ade clear that the strength of the treated soil is enhanced with the addition of each of the used admixtures to the muddy soil, and it is confirmed that an ideal mixing ratio of admixtures and soil exists.
(2) Concrete powder and paper sludge ash are effective as admixtures to muddy soil with less organic matter and low water content. For instance, the treated soil mixed with paper sludge ash became 2-3 times stronger compared with that only mixed cement.
(3) Cola fly ash obtained the greatest hardening effective due to the production of ettringite in all treated soils. The strength of the treated soil mixed with the coal fly ash which contained SO_3 ion and pozzolanic material was twice that of the paper sludge ash mixing. Therefore, the coal fly ash can be considered "most suitable admixture".
(4) Bentonite is affected to some degree by a reduction in moisture content and increased cohesion.
(5) If these admixtures are used, it is possible to decrease the quantity of hardening agent used and to reduce the curing period when the strength achieves the expected level.
(6) When the soil is treated with the special-blended cement, the high hardening strength can be observed from the early curing age through the long term.
(7) The hardening reaction products which contribute to a strength are CSH group reaction products and ettringite crystals.
(8) The strength, which is so low that the unconfined compression test can be performed, can be estimated by the fall cone test. It is consequently possible to predict the long team strength and to utilize the results of this test for a quality control of the treated soil. Less
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