Recently, chemical soil stablization using the deep mixing method has been actively adopted for the improvement of soft ground in the offshore regions. The objective of this study is to reveal the mechanism of strength development in the uncompacted stabilized soils made by the deep mixing method. The mechanical properties such as strength, modulus of deformation and pulse velocity of the solis stabilized by cement or lime-blastfurnace slag were comparatively investigated. Furthermore, the reaction process and microstructure in them were elucidated by X-ray diffraction, SEM observation and the measurement of pore size distributions. From these results, the relationship between strength development and change in microstructure in the uncompacted stabilized soils was discussed.
The reuse or recycle of waste materials is one of the most important problems in developed countries. The study is focused on the reutilization of the waste concrete powder, which is a by-product of recycling the waste concrete. This concrete powder is producted (about 30% in weight of original waste concrete) when the waste concrete is crushed and the aggregates are sieved away. The objective of this research is to clarify the possibility of the practical use of the cement hardened concrete powder. The treated samples were subjected to the following tests; an unconfined compression test, an X-ray diffraction analysis, a scanning electron microscope observation, etc. As the result, a large hardening effect was noticed when a small amount of the carbonated aluminated salt material is added to the cement, compared with the case of only cement mixing. The strength change during the subsequent hydration is then discussed. According to this procedure, the stabilized waste concrete powder can be applied as a soil stabilizer and/or a grout material.
Vertical loading tests of soil-cement columns were carried out in three soft grounds by banking in order to obtain the allowable bearing capacities and distribution of axial force of the columns. The axial strains, head and bottom settlements of the columns were measured during the tests. The soil-cement columns were placed in situ and their diameters were in the range of 45-47cm and the lengths were 3-6m. The test results show that the allowable bearing capacities of the columns are 4.7-10tons and the bearing capacities of the columns placed in the soft strata without reaching to the supporting stratum arises mostly from skin friction, while those placed on the supporting stratum from both of skin friction and end bearing resistance. The settlement of the columns in long term loading tests were very small in all grounds.
The purpose of this study is to clarify the relationship between the degree of weathering and the content of amorphous materials and the influence of amorphous components on the lime stabilization of the soil from the physico-chemical point of view. The ignition loss and the specific surface area which have been adopted as a criterion of the degree of weathering are related closely to the ratio of Al2O3/SiO2. This fact means that the ratio can be also used as a criterion of the degree of weathering from the chemical point of view. In conclusion, the ratio of Al2O3/SiO2 and lime content have a decisive effect on the unconfined compressive strength of the sample stabilized with lime.
It is well known that steelmaking slag expands by reacting with free lime and atmospheric water. Therefore, it is important to determine the mechanism of expansion in order to utilize the slag effectively as a material for subgrade, soil stabilization or concrete. In this paper, the expansive properties of electric arc furnace slags by water absorption were investigated by using a small-sized electric furnace to dehydrate crystallized water in the slags. A porosimeter was used to measure the micropore distribution and absorption of water in the slag under high pressure (199MPa), and a scanning electron microscope (SEM) was also employed. From the micrograph of SEM, it was observed that the surface of reducing slag particles was very rough with many protuberances like wens and that the slag particles became smaller by water absorption under high pressure. By using the relationship among the amount of water absorption, the amount of dehydration and the ratio of expansion, it seems possible to judge the effect of “aging” from the amount of dehydration.
It has been widely recognized that the addition of lime to soils improves the plasticity and strength characteristics of the soils. This paper examines the stabilizing effect of calcined dolomitic lime on a loam soil. Dolomitic lime is produced from mineral dolomite, a type of limestone containing about 30 percent magnesium carbonate. It has not been used as a soil stabilizer because of containing magnesium carbonate. A series of soil tests, including consistency test, unconfined compression test, oedometer test and CBR test, were carried out. The data of these tests showed that the addition of dolomite to the loam soil reduces its water content and improves its consistency characteristic, compressibility characteristics and strength characteristics as well as CBR values, which are normally recognized as the positive effects of the addition of lime to soils.
Recently, a micropiling reinforced soil method has been often used in the slope stability works. Its reinforcing mechanism, however, is still not clear and there is a confusion in different types of design methods. In this paper the ground confining effect by the micropiling reinforced soil method is discussed with the in site measuring data of the slope deformation behavior at the express highway construction work. The roles of micropiles as the tensile reinforcing and the restraint of stress relaxation are clearly shown and then these results will be reflected for improving the design method for the slope stability.
The vegetation method has been usually and widely used in order to control the erosion on slope surface. In sandy soil slopes, however, the vegitation often cannot be sufficiently carried out because, in such soils, the erosion occurs within a short period after planting vegetation or seeding. Therefore, it is necessary to stabilize the slope surface temporarily until the vegitation has covered the surface. In this paper, a temporary stabilization method, in which the mixed solution of iron-salt and lime is sprayed on the slope surface, is proposed. To examine the validity of the proposed method, some laboratory tests were carried out on sandy soils by adding the solution of iron-salt and lime mixed in various ratios. The results are summarized as follows: 1. The appropriate mixture ratio of iron-salt and lime is about 7:3. 2. The internal friction angle of soil is increased by mixing it with iron-salt and lime. 3. The strength increase is considered to be caused by the action of iron oxide as a cementing agent between the soil particles.
In order to control compaction of earthwork, it is necessary to obtain data on dry density and water content. In this study, a penetration test and an electric resistance test were used as the methods of measuring dry density and water content. These testing methods were applied to monitor the compaction work of the subbase level of the baseball ground which was improved by using coal cinders and decomposed granite. Furthermore, these data can be obtained very rapidly, easily and safely, with the same accuracy as the JIS-approved method. If these tests could be used, the control of the execution of work would be more easy and also the result of construction work would be more sound and of standard grade. Therefore, this research has contributed to raising the level of earth engineering in civil construction works.
Hydroxyapatite (HAp) powder has been synthesized using phytin contained in rice bran as a P-source, and the processes of formation and calcination of calcium phytate were observed by SEM and TEM. Phytin was extracted from 10g of oilless rice bran by 0.01N HCl solution at 60°C. The mixture of CaCO3 (0.7g) and Ca(OH)2 (0.3g) was then added to 200ml of the extract to obtain calcium phytate.The product was washed, dried and finally calcined at 1000°C for 3hr. to obtain HAp powder. The Ca/P atomic ratio of HAp powder obtained was 1.67. The observations by SEM and TEM showed that the calcium phytate consisted of spherical particles, which contained a small nucleus of calcium carbonate. The reaction between the nuclei and calcium phytate started from about 500°C, and then, the nuclei decreased gradually in size with increasing heat temperature and disappeared at 900°C. On the other hand, HAp powders obtained by calcining at 1000°C for 3hr. were spherical particles of about 0.2μm in the diameter.
SO42- ions loaded on the surface of TiO2 or ZrO2 act as a promoter to enhance the Lewis acidity of the metal cations upto the strength of super solid acid. The SO42- ions act simultaneously as a suppressor of the thermal growth of constituent oxide particles during calcination. The OH groups on the surface without SO42- ions are active to the Olation reaction which is 2OH→-O-+H2O, and leading to the coagulation and joining of the particles. The replacement of OH group with SO42- ion results in a retarding effect against the decrease of surface area and crystallization along with phase transition. The catalytic activity of super solid acid catalysts such as SO42-/TiO2 and SO42-/ZrO2 was found to be controlled by both the number of super solid acid sites and the acid strength.
Submicron grinding of low-soda alumina was studied with a ball mill using alumina balls from 30mm to 0.75mm in diameter. Low-soda alumina powder was of commercial grade and its average particle size was 1.64μm. The average particle size was calculated from the specific surface area measured by BET method, and the characteristics of alumina were determined by X-ray pH, DTA and TG. The results obtained are summerized as follows. (1) It was demonstrated that submicron grinding of alumina powder was possible in a short time by using balls of several mmφ in diameter. (2) The maximum grinding speed was achieved with balls of 2mmφ. (3) The following experimental relation was obtained, ln(Sw)=-0.399lnr3-0.482/r+0.503lnt+1.043 where Sw is the specific surface area, r is the ball radius and t is time. The multiple correlation coefficient R was found to be 0.952 when calculated by a computer. (4) A part of alumina transformed to gibbsite with a mechano-chemical reaction. (5) With decreasing particle size, pH of slurry became high. As a result, the viscosity of slurry became low, and the grinding speed showed no tendency to slow down.
By aiming at the development of a semiconducting composite in which semiconducting SnO2 particles are uniformly dispersed in glass matrix, fine semiconducting powder was prepared by ball-milling SnO2 powder with a small amount of Sb2O5. Several kinds of ball-milled powder were characterized by the measurement of specific surface area by B.E.T. method, thermal gravimetry, X-ray powder diffraction analysis, X-ray photo spectroscopy and the measurement of DC electric resistance.
In order to investigate the effect of the circulating load ratio CL on the properties of granule products in a closed-circuit granulation system, the relationship between CL and the residence time distribution of particles passing through a closed-circuit process was discussed with a few assumptions.Furthermore, the open- and closed-circuit granulation experiments were carried out in a single horizontal rotating conical vessel with a rotary lifter. CaCO3-powder and water were used as powder and binder, respectively. The results are summarized as follows. (1) It is expected that the uniform size and spherical products can be obtained by a closed-circuit granulation process having an effective separating system, although the theoretical consideration showed that the large CL makes the residence time distribution of particles wide in the process. (2) It was experimentally confirmed that more spherical, more uniform size and harder products were obtained in the closed-circuit granulation than that in the open-circuit granulation under the optimum circulating load ratio, CL<1.3 which satisfies the optimum separating condition in the present granulator, which has the functions of both granulation and separation.
Previous studies for estimating randomness of a binary solid particle system have shown that the total electric resistance, RS calculated by an approximation method is closely related to the degree of mixing. In this report, in order to estimate the randomness of the system, a parameter of short range disorder, σS was introduced as a criterion of the degree of mixing of the system. The short range disorder was difined as a ratio TC/TS, where TC represents the number of contact points between particles with different resistance (A particles and B particles) and TS represents the total number of contact points of all particles. The values of degree of mixing obtained from two different methods (one is the spot sampling and the other is the total inspection) were compared with the values of the parameter of short range disorder. Furthermore, in order to assess these methods, the correlation functions between σSvs. σTL, σS, vs. σSL, σSvs.RS, σTLvs.RS and σSLvs.RS were calculated, where σS is the parameter of short-range disorder, σTL is the standard deviation of the total inspection, and σSL is the standard deviation of the spot sampling. The computer simulated results showed that each correlation function described above is valid. Consequently, the total electric resistance calculated by an approximation (series and parallel) method can be used for the purpose of estimating randomness during the mixing process. However, in the spot sampling, the calculated values of degree of mixing was found to be affected by the number of samples and the sample size.
A kneading experiment of thermoplastic resin and carbon black (material for toner) was carried out with a continuous kneader under various feeding rates. In addition to the measurements of the mixing torque in kneading and the residence time of the material, an assessment of a dispersion state of carbon black was attempted by means of image analysis and the validity of this method was examined. From the results, it is suggested that the degree of dispersion can be determined by the density of aggregation of the kneaded material, and also it is clarified that the degree of dispersion in the kneaded material increases with a prolongation of the residence time, that is, as the mixing action works both radially and axially, or with an increase of the kneading energy.