The method of British Standard (BS) for mineral aggregate has an advantage that can statistically evaluate the strength of a large number of aggregates in one time. But we could not find any correlation of BS crushing value and strength of an artificial lightweight aggregate, which has high strength and low water absorption, newly produced by Taiheiyo Cement Corporation. By compression, fragments from crushed aggregates fill spaces inside the cylinder that would increase friction between piston and cylinder. It is studied a new method to press a large number of aggregates, which array in one layer, and here we call this method as ‘monolayer loading test’. As a result, we could find a good relation between values of monolayer loading test and compressive strength of the aggregate. By this method, we can evaluate the strength of the artificial lightweight aggregate statistically.
The recycling of coarse aggregate can be considered as a method for reducing the amount of concrete fragments that are disposed after the demolition of concrete structures. The objective of this study is to investigate experimentally the effects that recycled times have on the material properties of recycled coarse aggregate. The test results clearly indicated that the percentage of mortar in recycled coarse aggregate increases in relation to the number of recycled times and repeatedly recycling coarse aggregate gradually turns it into the condition of mortar. It was shown that the decrease in specific gravity and the increase in percentage of water absorption have a tendency to level off after some time to form a coarse mortar aggregate made from mortar fragments. In this limited study, the relationship equations between the number of times that coarse aggregate is recycled and its specific gravity as well as its percentage of water absorption was also studied.
Concrete waste is hardly recycled to be aggregate for concrete by only normal crushing, because the micro cracks remain in the crushed concrete and the particles of only mortar or cement paste are included. Thus many techniques to produce recycled aggregate are proposed and practiced, but these techniques need significantly much energy and may generate much CO2. As the preliminary test results, it was clarified that processes for recycled aggregate to absorb water or Pozzolanic material can improve the strength of recycled aggregate concrete, even though the only crushed concrete wastes are used. This absorbed water or Pozzolanic liquid is expected to fill up the micro cracks in recycled aggregate with cement gel by cement hydration or Pozzolanic reaction. Process to soak aggregate in mixing water was tried in the preliminary test for recycled aggregate to absorb water, but this process takes more than 10 minutes. On the other hand, attendance of colloidal silica as a Pozzolanic material into mixing water caused smaller slump. In this paper, the process to soak the recycled aggregate in colloidal silica solution before mixing is evaluated to sustain slump of plain concrete, and also the application of agent for reducing surface tension of mixing water is investigated to cut off the soaking process that is for aggregate to absorb enough water during mix.
The purpose of this study is to establish the technique that can be evaluated in the properties of the concrete using aggregate performance and mix proportions as indicator. In this paper, the application as indicator for aggregate performance of aggregate crushing value, sinkage of plunger (aggregate sinkage) and abrasion loss were inves-tigated by results of experiments using recycled fine aggregate mortar. From this experimental results, aggregate crushing value and aggregate sinkage could apply as the indicator for aggregate performance. Compressive strength and drying shrinkage of recycled fine aggregate mortar could be estimated by using that indicator. To apply elastic modulus of aggregate and aggregate shrinkage calculated from theoretical formulas as indicator were effective means, in addition to that indicators.
Physical properties of decomposed granites distributed widely in Tottori prefecture were examined. Subsequently, mix proportion and manufacture of concrete with water content of 150kg/m3 and slump of 8cm using the decomposed granite from Togou Dam site origin were conducted. The problems with this mix design, and the properties of the fresh and hardened concrete with the decomposed granite also were examined and compared to that of ordinary concrete with normal sand. Test results showed that the disadvantage of concrete with the decomposed granite where (1) slump loss with time is larger, (2) bleeding becomes almost equal to zero, and (3) setting time becomes short compared to that of the ordinary concrete, could be improved to have almost the same physical properties as that of ordinary concrete with normal sand by using a retarder type of air-entraining high-range waterreducing agent.
Copper slag is a by-product yielded from a copper refinery. The annual amount of copper slag in Japan is two million tons. The copper slag has been used for cement material, sand blasting, reclamation and so on. However, most of the copper slag is stacked high as waste since the production exceeds demand. This study on the application of copper slag as fine aggregate for concrete has been started with the expectation of large amounts of consumption. Many researchers have already found it possible to use a copper slag as a concrete aggregate. However, it also has been clear that the concrete with copper slag has some problems. One of them is excess bleeding attributed to the glassy surface of copper slag. Another problem is the delay of setting time of concrete with copper slag nevertheless it produced at the same refinery. The delay of setting time is more than one week in some cases although the durability in concrete is not affected by it. In this paper, the strength, setting time and durability of concrete with copper slag is clarified. It is shown that the delay of setting time does not have a negative influence on durability. Furthermore, the solution will be given in this paper.
In this study, the compensation effect on autogenous shrinkage of three types of high-fluidity mortars containing different binders prepared by adding with two types of expansive additives at various additive content had been examfined. As a result, it was cleared that, any expansive additive has the compensation effect for autogenous shrinkage, especially a free-lime rich calcium sulfoaluminate based-expansive additive has larger compensation effect for autogenous shrinkage than conventional calcium sulfoaluminate based-expansive additives, and that the effect of the mortar prepared with the same additive content of the expansive additive on the expanded volume varies according to the type of binder.
We discuss the influence of calcium sulfates on the fluidity of high-flow concrete made with ground granulated blast-furnace slag (BFS) and polycarboxylate-based superplasticizer (PC). Gypsum, hemihydrate and anhydrate were added to BFS and the effect of each was examined. Gypsum and anhydrate had no effect on the fluidity of high-flow concrete with BFS. By addition of hemihydrate, the fluidity of high-flow concrete is reduced at very early stages, but it is improved rapidly after 5 minutes. The amount of adsorbed PC, amount of ettringite and sulfate ion concentration in the aqueous phase of cement paste with BFS and PC were measured to clarify the mechanisms for the changing of fluidity. Fluidity was decreased linearly with the increase of sulfate ion concentration. The results of present study suggest that the change in fluidity of high-flow concrete with BFS and PC due to calcium sulfates in BFS caused by a change in the dispersion of particles by sulfate ions in the aqueous phase.
One of the main problems of fly ash concrete is reducing the resistance against carbonation of concrete due to consuming Ca(OH)2 by pozzolan reaction of fly ash. Then, admixing of fly ash into concrete may increase the corrosion risk of reinforcing steel embedded in concrete. In this study, the influence of fly ash admixed into concrete on corrosion behavior of reinforcement due to both chloride attack and carbonation, was estimated by means of electrochemical techniques. The results showed that when the cause of corrosion was only chlorides, microcell corrosion rate could be reduced by admixing fly ash. However, when there was the act of carbonation, corrosion rate of reinforcing steel embedded in fly ash concrete was increased, compared with the case of non-fly ash concrete.
As for the effective utilization of sludge water containing cement and fine particles of aggregate, JIS A 5308 permits now the usage under 3 percent as solids for the unit content of cement. This study, in order to utilize the larger quantity of sludge water than that now allowed in the mixing plants, is to obtain the basical data on the properties of fresh concrete and of hardened concrete. Especially, in order to stabilize the quality of sludge by preventing hardening of sludge due to the hydration of cement particles, the effect of setting retarder has been discussed experimentally. From the results of this study, it was clarified that a good quality concrete could be obtained even though the sludge mass of 9% and the sludge age of 3 days, provided that setting retarder was used adequately.
Self-compacting concrete has an unique characteristic which may influence on the flexural and/or shear strength of a reinforced concrete beam with vertical construction joint. In this research vertical construction joint was intended to be present either in the mid-span of the beam or in the middle of the shear span. Crack initiation loads, the crack width, failure loads and failure modes were investigated. With the vertical construction joint present in the midspan the crack initiation load was reduced to 60% of that of a control beam without joint. In addition, increased loads resulted in the substantial increase of the crack width. On the other hand, flexural crack formed at the construction joint in the middle of the shear span with lower loads leading to the shear failure with about 75% of the ultimate load of a control beam with an equal steel ratio.
Stress analysis by using fractography is already established technology as means for seeking cause of fracture and has been widely employed. In actually broken machine parts, however, sufficient analytical results may not always be obtained by the technique of fractography due to oxidation, stain or damage of the fracture surface. On the other hand, the fracture analysis method applying the X-ray diffraction method, that is, the X-ray fractography comes to be used as effective fracture surface analysis. In the X-ray diffraction method, the change in the values related to plastic deformation and residual stress near the fracture surface may be determined, and information of internal structure of material can be obtained. In the present study, based on the information from the fracture surface obtained by fatigue test, the correlation of X-ray parameter and fracture mechanics parameter was determined, and application to actual broken machine parts was studied.
Uniaxial tension fatigue tests of (α+β) Ti-6Al-4V were carried out in vacuum and air environments to clarify how these environments affect the surface and the interior originating type fatigue properties. Then, the effects of the environments on both fracture surface of stage 2a region and the condition of transition from stage 2a to stage 2b region were also investigated through fractographic analysis. As a result, the following conclusions were obtained: (1) The vacuum environment improved the fatigue lives of surface originating fractures although it gave no effect on those of interior originating fractures. (2) Crack propagation mechanism of surface fractures in the vacuum was different from that in the air. (3) The effect of the internal environment of materials on interior crack propagation was similar to that of the vacuum environment on surface crack propagation. (4) S-N properties were determined by the competition of surface fracture mode in high stress and interior fracture mode in low stress regardless of the environments.
An analytical study on thermal diffusivity for anisotropic materials using a laser flash method was carried out to clarify the applicability of the method which has been established for an isotropic materials. A measurement error for anisotropic materials caused by the laser pulse intensity distribution was estimated analytically using a finite element calculation code. In this paper the analytical result on the measurement error of the anisotropic materials was presented and the applicability of the laser flash method to the anisotropic material was discussed.