This study measured the mass decrease rate of the hardened cement specimens which deteriorated by sulfuric acid, hydrochloric acid, nitric acid and mixed acid which mixed these acids (i.e. sulfuric acid, hydrochloric acid, nitric acid) for the purpose of clarify the these chemical reaction mechanism. As a result, it was clarified that mass decrease rate of hardened cement is greatly dependent on concentration of sulfuric acid when mixed acids containing sulfuric acid and other acid (i.e. hydrochloric acid or nitric acid) act on hardened cement. In this study, it was apprehended that the cause of this chemical reaction mechanism is influence of molar fraction of sulfuric acid and it was indicated that this chemical reaction mechanism could be explained by Gibbs free energy and chemical kinetics. Moreover, in this study, it was proposed that prediction model of mass decrease rate based on these theories.
In this study, a technique for estimating concrete strength and evaluating its resistance to freezing and thawing was developed by quantifying early defects and voids in concrete using contrast radiography, and the applicability of the technique was investigated. Tests have revealed that the void content of concrete determined by contrast radiography correlates well with its compressive strength and resistance to freezing and thawing. Application tests were also conducted using this technique to evaluate the properties of concrete in newly built concrete structures and determine the deterioration depth of concrete for aged deterioration, with its utility being verified. The results of evaluation by contrast radiography were compared with those by air permeability testing, which has been widely used in recent years, to elucidate their relationship, while clarifying the characteristic of measurement result by air permeability testing.
The experiments have been conducted in order to investigate the mechanical and chemical properties of mortar with three different binders under the several conditions in accelerated carbonation curing. As the results, the depth of carbonation varied among each mix proportion. It is proven that by increasing CO2 density in the mortar having γ-2CaO.SiO2, the CaCO3 production will increase, which leads to the increase of filling ability in the pore of mortar. Furthermore, as a result from the calculation of Tritium permeation, it shows that the permeation decreases with an increase of CO2 density.
Analytical investigations points out that torsion moment acts on RC columns of rigid frame viaducts, which have irregular planar shape and unequal mass arrangement, and are on irregular ground. Therefore, we carried out loading tests of RC columns subjected to the reversed cyclic torsion and bending, and reproduced seismic damage of RC columns. Moreover, we investigated the influence of torsion on deformation performance of RC columns. As a result, the following was evident. There is little possibility of the collapse of RC columns subjected to combined torsion and bending. Deformation performance of RC columns subjected to combined torsion and bending decrease, however, there is little influence of amount of torsion and hoop reinforcing bar. The reason is that torsional deformation of RC columns localize at the bottom of RC columns. Furthermore, we presented consideration of seismic design of RC structures subjected to torsion moment.
The standard method of investigation of cracks on the concrete surface is usually visual inspection. However, the method has many problems such as inspection data spread, oversight, lack of objectivity and data quantification. Therefore, digital image analysis of concrete cracks is developed from the view point of efficient, automatic and quantitative inspection. For accuracy improvement on the extraction of cracks, the two-dimensional Gabor wavelet transformation method is applied to digital image analysis. Furthermore, it is clarified that the method is effective in cracks extraction from application of this method to the inspection of structure.
In this study, the analytical evaluation was conducted in order to evaluate the mitigation effect resulting from various retrofitting methods on ASR expansion. Through the investigation by means of Finite Element Analysis, ASR expansion model proposed by authors was applicable to evaluate the ASR expansive behaviors of RC columns retrofitted by steel plate bonding method and PC confined method. The parametric analyses were also conducted in order to evaluate the mitigation effect retrofitting on ASR expansion. As the results, it was quantitatively confirmed that the introducing lateral force such as PC confined method was more effective for mitigating ASR expansion than the retrofitting with high reinforcement ratio.
A versatile index which can identify failure and load-carrying capacity of RC planar members is proposed on the basis of analytical results in relation to material damage. This study aims to promote the performance verification applying finite element analysis based on material nonlinear constitutive models. Response behavior of various shape of RC planar members can be analytically evaluated with satisfactory accuracy, and situation at maximum load is approximately identified by two previous methods which use local strain if element size recommended in JSCE code is provided. The situation can be also identified equivalently by using consume strain energy averaged over certain region. Moreover, this method allows greater flexibility on mesh definition.