It can be said that corrosion of reinforcing steel is a serious problem for concrete structures. However, the corrosion mechanism of steel is still unclear, and it is difficult to prevent corrosion perfectly. In this study, in order to make clear the corrosion process in alkaline environment, the corrosion products formed in solutions of various OH- and Cl- concentrations were evaluated by Raman spectroscopy

A simple and accurate method is developed to model the effective elastic properties of early age cement pastes. It uses available data of media of which the microstructures are close to that of the predicting medium. Such technique allows us to model accurately the effect of the hydration degree on the effective elastic properties. On the other hand, the hydration degree of a hydrating cement paste

Ordinary “loop joint” applied to precast prestressed concrete (PC) deck slab tends to increase its thickness. By decreas-ing this thickness, the dead load of the deck slab can be reduced. Hence, we have developed an “improved (inclined) loop joint” that reduces the deck slab thickness. This study presents the results of static bending test of slab specimens to confirm the load-carrying behavior and

This study aims to develop and propose a seismic retrofitting method for unreinforced brick masonry for improving the seismic safety of the 1st and 3rd headquarters buildings of Kyushu University. Five brick wall specimens representing parts of the walls that were adjacent to the openings in the headquarters buildings were prepared on a 3/4th scale of the actual structure and they reinforced on either

For better understanding of irreversible shrinkage, nine hardened cement paste (hcp) samples with three different cement types and three different water to cement ratio were prepared. Four different relative humidity conditioning histories containing the first desorption, re-humidification and the second desorption are investigated for all the specimens to obtain the length change and water sorption

The authors have reported from experimental investigation that the use of closed stirrups, U-shaped stirrups and rod-shaped reinforcements as shear reinforcements in reinforced concrete (RC) beams results in clear differences in internal crack patterns and maximum strength. In this study, simulations of the experimental beams were performed using a three-dimensional rigid-body spring model, demonstrating

The effects of gamma irradiation on concrete properties during early hardening were studied towards radioactive waste storage or accelerated processing at precast plants. Concrete mixtures containing different mineral aggregates (baryte, magnetite, amphibolite) were investigated. During initial 16 hours of hardening the mixes were irradiated using 60Co gamma source at the rate of 3.5 kGy/h. The mechanical

Calcium leaching from cementitious materials into bentonite is a key process for the long-term alteration of cement–clay interfaces of engineered barrier systems. Strong chemical gradients between cement and clay drive the precipitation of minerals such as calcium silicate hydrate (C–S–H) and calcite. To analyze the mineralogical and porosity evolution at the cement–clay interface, composite specimens

Calcium leaching from cementitious materials in contact with bentonite in nuclear waste repositories can alter the functionality of an engineered barrier system. In this study, we contribute to the fundamental understanding of calcite precipitation at cement–bentonite interfaces by adding carbonate to bentonite. In addition, we accelerate the transport of charged reactants towards the interface using

Lateral loading tests using reduced reinforced concrete (RC) walls affected by alkali-silica reactions (ASR) and their simulation analyses were performed in order to evaluate the influence of ASR on the structural performance of shear walls that act as seismic resistant members in nuclear power facilities. The state of RC walls was also measured by several techniques to assess applicable monitoring

The decarbonization of concrete structures sector is a priority due to the world climate. Since Portland cement is responsible for approximately 7% of the anthropogenic emissions worldwide, it is decisive to partially replace it by products with lower environmental impact. Fly ash has become highly demanded, due to its proven advantages, however, has announced end by the developed countries. The purpose

In existing bridge structures, reinforced concrete dapped-end beams/girders (RCDEB) are frequently subjected to service loadings that exceed their design capacity, due to increasing economic and population growth. Dapped-end beams are prone to the accumulation of water due to improper drainage and sealing of the joint, providing favorable conditions for corrosion due to the stagnation of chloride rich

The degradation factors considered in the evaluation of long-term soundness of reinforced concrete structures in nuclear facilities in Japan are heat (high temperature), irradiation, carbonation, chloride penetration, alkali silica reaction, and machine vibration. As described in the “Guidelines for Maintenance and Management of Structures in Nuclear Facilities,” the soundness evaluation of equipment

To assess the durability of concrete structures at nuclear power plants in Japan, plant life management technical evaluation is performed in accordance with the guidelines of the Architectural Institute of Japan for the maintenance and management of structures in nuclear facilities. Concrete carbonation is one of the degradation factors covered in the guidelines, and sampling is performed to confirm

Advances in the development of concrete materials have led to increasingly complicated composite systems. Investigation of such complex systems by traditional sampling methods requires a large sample size to understand the influence and interactions of all important factors, and conducting full size experiments with a large number of samples could be onerous and expensive. To devise more efficient

The determination of the mineral composition of aggregates which constitute an important component of concrete is essential to understand and estimate the durability of structures. The modal (quantitative mineralogical) analysis of rocks is generally determined by point-counting method on thin sections or slabs. However, there is a difficulty of mineral identification depending not only on the experience

Cr3+ and Cu2+ can be cured using basic magnesium sulfate cement (BMSC). The influence of compressive strength, water resistance, and leaching characteristics of BMSC-solidified bodies was studied to evaluate the applicability of BMSC cement in industrial solid waste treatment. XRD, SEM, MIP, TG and FTIR were used to analyze the hydration products and microstructures of the solidified BMSC. The results

Cement-based materials used at radioactive waste disposal sites are required to possess long-term stability. However, when these materials come in contact with groundwater, calcium leaching from the solid occurs, and the material becomes porous. The use of mineral admixtures is recommended to minimize porosity. However, few studies have focused on the diffusion performance of cement-based materials

Weathering steel (WS) is known to develop higher corrosion resistance than ordinary steel under atmospheric condition due to the formation of a protective, dense rust layer. This aspect, however, has not been studied so far in cement-based materials, which are characterized by high alkalinity and limited oxygen. To address the need for durable RC structure in extreme environments, it is necessary to

Few reports have described practice-based models assessing ultimate strengths of existing reinforced concrete (RC) members subjected to frost damage. This paper presents a kinematic model for shear assessment of damaged RC short columns based on the upper bound theorem. Without regressive functions, the developed model predicts the shear strength contribution of damaged concrete when the displacement

Self-healing cement composites are considered to be an effective solution towards the enhancement of sustainability and service-life of cement and concrete structures, as well as the reduction of repair and maintenance cost. Among the several self-healing technologies, encapsulated healing agents present benefits that include healing of larger cracks and timeless healing potential upon damage. This

In this study, finite element (FE) analyses were conducted on a reinforced-concrete (RC) shear wall that is affected by an alkali–aggregate reaction (AAR), which were then applied for a benchmark studies in OECD/NEA/CNSI/ASCET (Organization for Economic Co-operation and Development/Nuclear Energy Agency/Committee on Safety of Nuclear Installations/Assessment of Structures subjected to Concrete Pathologies)

Municipal waste incineration ash contains heavy metals, and the safety of its disposal and reuse is an important issue. In this study, we discussed a safe recycling technology for bottom ash (BA) by utilizing the excellent heavy metal immobilization feature of geopolymer (GP). First, the differences in chemical compositions, physical properties, and heavy metal contents of BAs discharged in different

The purpose of this study is to improve the interfacial performance between the concrete and polymer cement mortar (PCM) by using nano-SiO2. This study examined the bond properties of the inclusion of nano-SiO2 in the PCM based on splitting-tensile tests. In addition, the bonding mechanism was investigated with SEM. The results demonstrate that the inclusion of 2% nano-SiO2 in the PCM is beneficial

Concrete structures serving in cold and wet regions usually suffer frost damage and thus have server deterioration. Many researches have been conducted to reveal the damaging mechanism and damaged mechanical properties of concrete under the effect of frost action. It has been widely known that the strength and stiffness of frost damaged concrete without using air-entraining agent decrease under room

The effect of bacterial and fiber combination to enhance the properties of GGBS based geopolymer concrete to be used as paver block is investigated in this study. In this study, Bacterial combinations such as Bacillus Subtillis and Bacillus Sphaericus and high modulus glass fibers and low modulus polypropylene fibers were incorporated to produce hybrid fiber reinforced bacterial geopolymer concrete

This experimental and numerical study aims to evaluate the penetration depth of contaminated water in the concrete structures involved in the Fukushima Daiichi nuclear powerplant. The influence of the mortar mixture on water absorption was investigated by varying the composition: mortar containing aggregates from river sand and crushed limestone sand was compared, and 15% of the cement in the mixture

A detailed inspection of a dam in Thailand is reported for its time-dependent gradual expansion towards upstream, contrary to the expected downstream creep deflection owing to hydrostatic loads. In this study, based on petrographic analysis and SEM, a sample of cored concrete from the dam was found to undergo a low to moderate level of ASR. The potential for future expansion was verified using an accelerated

The resistivity of fresh concrete was obtained for the period from casting to the age of 72 h by a non-contact electrical resistivity measurement. Early hydration process of three types of concrete with the ratio of water to binder in mass of 0.4, including ordinary Portland cement concrete (OPC), concrete with fly ash of 30% (FAC) and concrete with silica fume of 5% (SFC), were analysed and compared

Degradation of reinforced concrete (RC) structures can occur through the carbonation-induced corrosion of reinforcing bars, and this process is a major concern for the durability of RC buildings. Structures located in relatively humid inland environments are especially vulnerable. Therefore, it is important to clarify how relative humidity (RH) affects steel corrosion rates in carbonated concrete.

The experimental results of the bond behavior between glass fiber reinforced polymer (GFRP) bars and concrete under several aggressive environments were studied. To give a comprehensive and comparative evaluation, a total 60 GFRP bar-concrete pullout specimens were divided into a control group and a treated group being immersed in tap water, alkaline and saline solutions for up to 270 days. The influences

Considering the low-permeability of reactive powder concrete (RPC) and the influence of pressurized liquid on crack development, this paper studies the mechanical properties of sealed and unsealed prismatic RPC samples under different confining pressures. It is determined that the stress-strain relations of sealed and unsealed RPC samples are almost consistent before the stress reaches its proportional

Inspection data of actual concrete structures should be analyzed to elucidate the deterioration mechanism and construct a regression model. Although machine learning can be applied to this problem, inspection data are not suitable because machine learning targets big data with a uniform density and a balanced distribution. This study applies machine learning to a regression model of the crack damage

Shear failure experiments of concrete beams containing a weak layer were conducted with a focus on the bifurcation of shear localization appearing at the boundary between structure and soil foundation. Low-strength concrete, which is analogous to artificial soft rocks and strengthened foundation, was used to create a weak layer that caused dispersal and bifurcation of the shear localization area, resulting

Fiber Reinforced Polymer (FRP) composites in the form of laminates and fabrics are installed on reinforced concrete members, using externally bonded (EB) techniques for strengthening. However, the utilisation of capacity of FRP composites is limited due to debonding observed in the strengthening system, due to FRP and concrete interfacial shear stress. Carbon fiber reinforced polymer (CFRP), in a new

Recent progress in finite element analysis aids the simulation of seismic vibration of an entire reinforced concrete (RC) building structure and indicates that drying shrinkage cracks affect seismic resistance performance. Polypropylene fiber-reinforced concrete (PFRC) is a promising material since the fibers will reduce the cracks and strains under drying shrinkage. This paper attempts to quantify

The bond behaviour of plain rebars embedded in ambient cured geopolymer concrete (GPC) prepared with a mix of fly ash and ground granulated blast furnace slag (4:1 by mass) was studied to evaluate the adhesive bond between these rebars and concrete. As GPC is an inorganic polymer concrete, the adhesive bond strength of concrete is evaluated for its suitability to reinforced concrete applications. Pull-out

The corrosion morphology and the mechanical behavior of corroded prestressing strands are investigated in the present study. Nineteen corroded strands are obtained through controlling stress level, corrosion time and chloride ion concentration under artificial climate conditions. A total of 119 corrosion pits are counted to investigate the geometric morphology of corrosion pits. A depth-width ratio

Mechanical properties of calcium silicate hydrates (C-S-H) with C/S ratios of 0.75, 1, and 1.33 were examined with nanoindentation after gamma-adsorbed doses of 0.145, 0.280, 0.500, and 0.784 MGy, and were compared with control samples. Young' s modulus and stress relaxation tests showed no apparent trend with irradiation dose. Qualitatively, most of the irradiated samples were found to relax more

In this study, a method was developed to estimate accurately the chloride threshold value for corrosion initiation in reinforced concrete. In this method, chlorides are supplied through a part of the specimen surface, and half-cell potential between the rebar and reference electrode embedded in a concrete specimen was measured in every ten minutes. A sudden drop of half-cell potential was observed

During sorption, the microstructural evolutions of two different cement pastes (with water-to-cement ratios of 0.40 and 0.55) are studied via proton-nuclear-magnetic-resonance relaxometry. The water uptake test is performed for samples dried at 105°C under three different temperatures of 20°C, 40°C, and 60°C for the first twenty-six days of sorption. It is observed that the water went first to the

This paper introduces a novel and simple model for estimation of the shear contribution of the fiber-reinforced polymer (FRP) strengthening system in the FRP-strengthened beams. The model utilizes the bonding-based approach, which considers the shear resisting mechanism of FRP-strengthened beam via the bond behavior between FRP strengthening system and concrete. Herein, the beams strengthened in shear

In nuclear power plants, concretes used for biological shielding walls are exposed to radiation such as neutrons and gamma rays over the long-term operation of the plant. Previous studies have reported that neutron irradiation causes aggregate expansion due to the metamictization of quartz and feldspar leading to reduced density and a loss of the compressive strength and Young' s modulus of the concrete

In this study, the effects of Perlite, Leca, and Scoria as lightweight aggregates have been investigated on the properties of self-compacting concrete at the fresh and hardened phases. For this purpose, the ratio of water to cement and super lubricant were kept constant in the mixing rules. Performance tests, such as Slump flow, J ring, U box, L box, and V-funnel tests, were used to investigate the

To evaluate the radiation-induced degradation of concrete, a rigid-body spring network model is introduced that takes into account the three phases in concrete: mortar, aggregate, and the interfacial transition zone. The proposed model enables evaluation of the change in the physical properties of concrete affected by aggregate expansion under the free restraint condition. Good agreement with previous

Due to their wide applicability in inspection of concrete structures, there is considerable interest in the development of automated crack detection method by image processing. However, the accuracy of existing methods tends to be influenced by the existence of traces of tie-rod holes and formworks. In order to reduce these influences, this paper proposes a crack detection method based on semantic

Aiming at improving bond strengths between FRP sheet and concrete, the FRP sheet bonding method using high elongation elastic resin as a buffer layer was developed. In this study, bonding tests was conducted to clarify the basic bond characteristics of FRP strand sheet-concrete interface with a polyurea resin. As a result of the bonding tests, it was found that the use of the polyurea resin as a buffer

The adhesion failure of the interface between concrete and rendering mortars often leads to the degradation of the reinforced concrete building envelopes. Although several methods to improve the adhesion properties between concrete and rendering mortar have been proposed, there is no system to evaluate the effectiveness of these methods from the perspective of durability. To this end, this study proposed

In this research, concrete-filled braided carbon fibre-reinforced polymer (CFRP) tubular beams and arches were constructed. CFRP tubes and concrete-filled CFRP tubular cylinders were compressed to investigate the constraint effect of the CFRP tube on the concrete. Long and short beams were bent to reveal the deformation styles and the failure modes controlled the flexure and the shear, respectively

A mix-design method based on packing model was used to optimize the mix proportion of Reactive Powder Concrete (RPC) containing phosphorous slag in this paper. The design aimed to achieve a densely compacted matrix by applying the modified Andreasen particle packing model, i.e., the Dinger-Funk particle size distribution (PSD) equation. MATLAB and Excel Solver Tool were utilized to implement the calculation

The steel-plate bonding method used to reinforce concrete slabs in bridges has a long record of adoption, and has played an important role for many years. Favorable conditions have been observed with this method in periodic inspections; however, as part of durability tests, decreases in strength of the epoxy resin adhesive (which is one of its component materials) have been observed following over

In this study, thermoporometry by differential scanning calorimetry and proton NMR measurements of hardened cement paste equilibrated under different humidity conditions were carried out, and the results of both measurements were compared. The results reveal that thermoporometry by low temperature DSC measurement cannot detect the water present in samples equilibrated at low relative humidity. On the

The present research aimed at evaluating early age thermal cracking risk of durable RC slabs incorporating slag cement and expansive additive on multiple span steel box girder bridges utilizing full-scale 3D FEM simulation. First, laboratory investigations were conducted to calibrate the material models of durable concrete. Second, the material models were utilized in several member level FEM models

Explosive spalling is a severe threat to concrete at high temperature. The addition of steel fibers is believed to be useful to mitigate explosive spalling of concrete. But predicting explosive spalling of steel fiber reinforced concrete remains to be a challenging topic. This paper adopted a popular machine learning approach, i.e., artificial neural network (ANN), to predict explosive spalling of

The objective of this research is to propose a simple and accurate prediction method for the shear capacity of reinforced concrete beams with steel fiber (RSF beams). Steel fiber reinforced concrete (SFRC) is being widely used nowadays, with the steel fibers added to the concrete to improve the tensile resistance. First, this research aims to investigate the material properties of SFRC in various concrete

In view of the life-cycle assessment of concrete pavement, three-dimensional behavioral simulation was conducted by integrating constitutive laws for cracked/uncracked reinforced concrete, modeling of pore water inside cracks and multiyield surface plasticity for soil to investigate the fatigue life under high-cycle moving loads. Presented is a discussion that the balanced pavement requires thicker

Recent studies in the field of concrete materials show that the early cracking criteria in micro-size can occur as soon as the cement matrix becomes hardened. In many ways, these cracks can become macro-size and opened cracks resulting in significant issues for the durability and appearance of concrete structures as water leakage and corrosion. The technique of self-healing using bacteria has recently

Multiple factors, regarding mechanical properties, load levels, and environmental conditions, affect the fatigue lifetime of reinforced concrete (RC) bridge decks. For the mechanical behavior, previous research predicts the fatigue lifetime of RC decks as a function of their punching shear capacity, where they give less attention to other modes of failure due to experimental limitations of fatigue

The Fukushima-Daiichi nuclear power station accident in East Japan in 2011 released radioactive cesium (r-Cs) into the surrounding environment. In addition to the major contamination of soil and vegetation, surrounding concrete structures have also been contaminated. Understanding the contamination characteristics is important for the decontamination or disposal of offsite and onsite concrete structures

Plant concretes were developed and are currently used as filling material in a timber frame. Their properties are strongly related to the bio-aggregates characteristics. In addition, since hemp shiv, the reference bio-based aggregate, has a limited availability, it is necessary to consider alternative bio-aggregates largely and locally available. Thus, this paper focused on identifying and understanding