Standardized tests for engineering properties, such as viscosity, volume shrinkage, percolating and solidifying abilities have been carried out simultaneously on various chemical grouts of water glass type, urea resin type, acrylamide type and isocyanate type, which are now being used. The results show that these tests are suitable to compare each characteristic of these chemical grouts simultaneously under the same condition. The goal for developing new chemical grouts which cause no environmental pollution is also established.
A highly plastic clay in the Osaka formation is known as the soil having unusual characteristics, and it gives many troubles in construction works. One of the reasons is that the soil contains a large amount of colloidal materials and a small amount of montmorillonite. This fact, however, offers a proper condition for lime stabilization. The aim of the present study is to find the effects of compaction and stabilization with quick lime on the soil by the measurement of pore size distribution. The result shows that the pore size distribution of a compacted specimen and the compressive strength are closely correlated each other. The behaviour of over-compaction found in the soil can be avoided with the lime stabilization.
Soft clays, particularly alluvial deposits, are widely distributed over several coastal regions in Japan. Their softness is the main obstacle for using them as construction and foundation materials. In order to improve these inferior clays, a new treatment method using a trivalent cation, Fe+3, was introduced. Iron powder was added into a soft clay by various amounts and the mixtures were cured in aerated and unaerated conditions. After various periods of time, tests were performed to measure the change of engineering properties of the treated samples. The main effect of the treatment was found to be the increases in shearing strength and rigidity of the samples due to the bonding between clay particles and trivalent iron ions from the added iron powder. And the mechanisms of these improvements were clarified by studying with a scanning electron microscope and other instruments.
Cation-fixation in soil occurs when exchangeable or water-soluble cation in soil are converted into the form that cannot be readily extracted with a solution of neutral salt. That is, exchangeable ions are changed to the nonreplaceable state. Potassium ions are known to be the primary one involved in such a reaction. In the field of pedology, the study of K-fixation has been performed actively, but from the viewpoint of soil mechanics, especially soil stabilization, it has been hardly done. The present study was undertaken to clarify the physicd-chemical change of clay minerals and the change of the engineering properties due to K-fixation. From the results of X-ray diffraction and differential thermal analysis, it was found that K-fixed soil has a structure similar to illitic clay. The engineering properties of montmorillonite is also stabilized. It is considered that this stabilization is due to the formation of aggregate of clay caused by the decrease in potential energy between clay particles and by the fixation of K ions between the internal layers of clay.
When molten slag is cooled rapidly by means of high pressure water jet, it solidifies as a porous glassy material, thus forming small granules like volcanic sand. This material is known as granulated slag. This report describes a production system and general properties of blastfurnace granulated slag, as well as the results of field tests which were performed to examine its applicability as a banking material. Two types of test banking are constructed to test the following points. (1) The weight reduction per unit volume of banking. (2) The influence of repeated traffic load to banking. (3) The influence of rainfall to each slope of banking. (4) The variation of pore water pressure inside of banking. The results obtained are as follows. (1) The unit weight of banking was 1.0∼1.4g/cm3 as γd and 1.15g/cm3 as the average to 1.00m depth from the surface. (2) Only a little deformation was caused by repeated traffic load. It was possible to cut out a field specimen from the test banking after 21 days of working. The unconfined compression strength (qu) was 4∼6kg/cm2 and the modulus of deformation was 1000∼6000kg/cm2 after 49 days of working. (3) The surface material of the slope made of decomposed granite was scoured out after several hours of raining, but the slope made of the slag did not change. (4) The pore water pressure inside of the banking made of granulated slag was relatively lower than the other.
In order to examine soil stabilization with granulated slag, the masado and cohesive soils were mixed with slag and lime, and their chemical characteristics, unconfined compression strength, triaxial compression strength, and plate loading strength were determined. Furthermore the applicability of the granulated slag as a material for soil stabilization was discussed. Lime was found to be effective in pulling out the potential hydraulicity of granulated slag in a short time, raising the unconfined compression strength in 7 to 14 days, while decreasing the calcium concentration and pH value in the water soluble contents of the granulated slag. The mixture showed a better effect on the unconfined compression strength than the lime stabilization method. The similar effect was found in the triaxial compression strength, too. The increase in cohesion contributed to the increase in its strength. If this potential hydraulic granulated slag were scattered on the soft ground as a reclamational material, it would give 2 to 6 times more bearing power compared with the usual case of sand reclamation.
Water reducing admixtures are usually added to concrete mix in order to improve workability of fresh concrete, and to improve physical properties of hardened concrete. Customarily, these admixtures are dissolved in mixing water, and then mixed with other concrete materials. It was found that the effectiveness of the admixtures can be greatly enhanced by changing purposely the timing of admixture addition to concrete mix. Ready mixed concrete Method A: Add an admixture to concrete mix at the end of the ordinary mixing period. The concrete mix is then agitated during the transportation period. Method B: Add an admixture at a job site. The concrete mix is then agitated vigorously in a truck mixer. Method C: Combination of methods A and B. Job site mixing Method D: Add an admixture to concrete mix at the delayed time, and then complete the mixing. The following advantages can be expected when a suitable admixture is used combined with an appropriate choice of methods described above: (1) Retempering by admixtures, (2) to produce flowing concrete and (3) to improve the water reducing action of admixtures. These advantages can be achieved economically without any deteriorating effects on the final products.
This study aims at revealing the effects of the particle size and content of reactive aggregates on the expansion of mortar bars. The reactive aggregates used were opaline amorphous silica from Kagoshima in Japan and powder of pyrex glass (borosilicate glass). They were mixed with the non-reactive aggregate of Toyoura standard sand and a normal portland cement with the equivalent percent Na2O of 0.71 percent to make a series of mortar. The amount of the reactive aggregate was fixed to 10 percent of the total aggregate by weight for the mortar bars for testing the effect of particle size on the expansion, and it was varied from 5, 10, 20, 50, 70, to 100 percent for the mortar bars for examining the effect of reactive aggregate content on the expansion. The results obtained for the opaline silica are summarized as follows: (1) The mortar bars with the opaline aggregate show the maximum expansion at the particles size of 0.149-0.238mm and 10 percent replacement. (2) The surface of the mortar specimens using the fine aggregate is uniformly covered by white fine powder. Some transparent exudation appears on the surface when the coarse reactive aggregates are used. (3) A scanning electron microscopic study shows that fibrous crystals are newly produced on the alkaline silica gel which covers the opaline aggregate during the storage of specimens. This fibrous crystals may be considered as a secondary reaction product.
A series of studies have been planned to clarify the time-dependent stress-strain behaviors of concrete. The present paper describes firstly the experimental results and discussions of creep phenomena of concrete subjected to high tensile sustained stress. It includes a statistic treatment tried to analyze the tensile creep limit and the time to tensile creep rupture occurance. Secondly, the results of tensile relaxation tests of concrete are given; the tensile stress relaxation as well as the compressive relaxation can be fully approximated by a hyperbolic equation with two experimental constants representing the relaxation time and the ultimate residual stress, respectively, and the ratio of the ultimate relaxation loss to the unit initial stress represents a characteristic value of relaxation corresponding to the ultimate creep factor.
Most of the studies on creep of concrete have dealt with the deformation under lower sustained stress, but not with the rupture or the deformation under higher sustained stress. In this study, the creep rupture tests were performed on the normal and lightweight concretes. The results obtained can be summarized as follows: The phenomenon of creep rupture can be divided into three parts, transient creep, steady state creep and accelerating creep, and the relationship between the rate of steady state creep and the time to failure can be shown by an exponential function. On the assumption that the time to failure takes place in a stochastic process, its fluctuation was discussed. The statistical analysis of the test results shows that the probability of survival at the same stress level is represented by a logarithmic normal distribution. The creep limits of the normal and lightweight concretes are determinend, respectively, as 84.5% and 83.8% of the static strength, by the Probit analysis method.
In the present paper, some statistical properties of the strength of cement paste and mortar are discussed in relation to their fracture process or failure mode. The variables chosen in the experiment are the kind and content of defect (air void or aggregate) in a specimen and the size of specimen. The main results obtained are summarized as follows: (1) The fracture process of cement paste and mortar becomes stabilized as the air or aggregate content increases. (2) The larger the size of specimen is, cement paste and mortar show the more stable or ductile fracture process in the range of small size, but their fracture process transforms from ductile mode to brittle mode as the size of specimen becomes larger than a specific size. (3) The statistical distribution of strength is closely related to the fracture process and the failure mode. The mean slope of the distribution curve of strength illustrated in the relation between ln(-ln(1-P)) and ln(F) increases as the fracture process is stabilized. (4) The mean strength decreases with the increase of air content, and the rate of decrease of compressive strength is more significant than that of flexural strength. (5) The aggregate plays the following two conflicting roles for the strength of mortar, i. e., the role as a defect which deteriorates the strength and the role as a crack-arrestor which improves the strength. (6) The scale effect of the strength of mortar is more significant as the aggregate content becomes lower.
Resin concrete has recently been attracting general attention as a light weight structural material, and the amount of work on design and properties of resin concrete is increasing steadily in recent years. Resin concrete is composed of resin, fine powder, sand and gravel. In the case that fine powder and sand are used as fillers, it is called resin mortar. They can be considered to be a kind of particle dispersed composites. Such materials generally show a considerable spread in fracture stress, so that a statistical treatment is required to deal with their strength properties. The tensile strength of composite materials is known to depend on composite morphology, existence of voids and brittle property of particle, matrix and bonding surface. In this paper, the tensile strength analysis is undertaken on a particle dispersed composite consisting of matrix, n kinds of particles and void. The specimen is divided into cross sectional elements and the law of mixture is applied to the strength of the unit cell. The Weibull distribution is adopted for the distribution of the strength of the element in composite materials, because it has an advantage of easiness of treatment over the normal distribution, and because the two distributions are close each other within the range of 40 percent of the coefficient of variation. The results of our analysis are found to agree very well with the experiments on resin mortar.
Many structures have been constructed and used in marine environment. When properly designed and constructed, reinforced concrete is the most suitable material for a wide range of sea structures. However, the electrochemical corrosion of reinforcing steel which endangers the durability and safety of concrete sea structures is the most critical problem. In analyzing the corrosion of reinforcing steel embedded in concrete, the most reliable method is to test the reinforcing steel in actual conditions that the structures would be exposed to. However, the method takes a very long time to obtain the test results. In order to shorten the time of testing, accelerated corrosion tests under raised temperature and under high humidity have been performed in the present study. As a result, the accelerated test is proven to be very effective. Influences of salt concentration in mixing water, of crack width in covering concrete, and of surface condition of reinforcing steel, on the corrosion were investigated. The results of the tests are summarized as follows; (1) At raised temperatures ranging from 40°C to 60°C, the time needed to corrode reinforcing steel embedded in concrete becomes much shorter than that at normal temperature. The accelerated method of testing is very effective in shortening the time of testing. (2) The amount of corrosion of reinforcing steel embedded in concrete was estimated from the ratio of the corroded surface area to the total surface area. Cracks narrower than 0.06mm did not give any distinct influence on the whole corrosion except just around the cracks. (3) The corroded area of embedded steel was much larger on the lower surface than on the upper surface.
Cement concrete is a most popular structural material at present, but its basic weakness is a limited chemical resistance to various chemical agents. In this paper, autoclaved concrete (AC), polystyrene-impregnated autoclaved concrete (PIAC) and water-cured concrete (WCC) were prepared and tested for chemical resistance to ten types of chemical agents such as hydrochloric acid, sulfuric acid, sodium hydroxide, etc.. The conclusions obtained are summarized as follows: (1) In general, the chemical resistance of various concretes is in the following order; (good) PIAC>AC>WCC (bad). (2) The aggressive chemical agents that attack markedly various concretes are hydrochloric acid, sulfuric acid, ammonium sulfate, etc.. (3) It seems that the chemical resistance of various concretes depends on the formation of free Ca(OH)2 (highly reactive and susceptible to attack by chemical agents) and tobermorite (chemically resistant and watertight, produced as a result of autoclaving) in them. (4) The superior chemical resistance of PIAC is due to the impregnation of autoclaved concrete with chemically resistant polymer (polystyrene).