Condition Of Concrete Structures Research Articles

Aggressive effect of vegetable oils and organic fatty acids on cement-sand mortar and concrete

Vegetable oils have a destructive effect on the strength properties of cement-sand mortar and hardened concrete, even with relatively short-term exposure. The degree of exposure depends on the type of oil, the viscosity of the oil, the quantitative ratio of fatty acids and their position on the triacylglycerin radical, the duration of exposure, and other factors. The aim of the study is to identify the intensity of the aggressive effect of vegetable oils (corn, olive and palm) on the strength of axial compression of cement-sand mortar and concrete. Concrete and cement-sand samples were tested for axial compression strength after being kept in vegetable oil for 10, 20, 30, 40, 50, 60, 70 days. Based on the factor analysis of statistical data, empirical mathematical models have been developed for predicting changes in the axial compressive strength of cement-sand mortar and concrete. Mathematical models of the strength of hardened cement-sand mortar and concrete oiled with vegetable oil link their strength with the viscosity of the oil, the duration of oiling and the comprehensive characteristics of the porosity of the sand. These mathematical models are valid in the range of the duration of oil exposure to cement-sand mortar and concrete 0 < τ ≤ 70 days. Mathematical models for predicting changes in the axial compressive strength of cement-sand mortar and concrete are proposed for the first time and are heuristic. The results obtained are of scientific importance for predicting changes in the state of concrete structures under the influence of vegetable oil and ensuring their comprehensive protection from its negative effects. The results of the study are of practical interest for the design, erection and operation of industrial buildings.

Accounting for the effect of creep and shrinkage on the stress state of concrete structures of cable-stayed bridges in Myanmar

The article considers the finite element analysis of the influence of time-dependent processes (creep and shrinkage) of concrete on the structures of a concrete cable-stayed bridge according to Russian, European and American standards. For numerical calculation, the Midas/Civil software was used, which allowed us to take into account elastic short-term deformation and creep deformation, as well as changes in the strength of concrete over time. Long-term deformations in concrete elements could be 1.5~3.0 times higher than elastic deformations and were observed in the first few months, and most of them occurred within five years. The object of research was a cable-stayed bridge with a reinforced concrete beam with a box girder. Three calculation models were used to model concrete shrinkage and creep: according to Russian, European and American standards. The results of the study showed significant discrepancies between foreign and Russian standards for accounting for long-term processes in concrete structures of cable-stayed bridges. Creep and shrinkage processes led to increased displacements in the box girder and pylon. Moreover, with an increase in the humidity of the environment, the deflection of the girder decreased, and the displacement of the pylon slightly increased. The cable-forced was reduced by the shrinkage and creep of the concrete. It was found that the loss of cable forces decreased with increasing humidity of the environment.

Experimental and numerical studies of stress-strain state of concrete structures reinforced with polymer-composite reinforcement

Experimental and numerical studies of stress-strain state of concrete structures reinforced with polymer-composite reinforcement

Deterioration of concrete structures along with case studies in India

Concrete is used extensively in various types of construction works. However, the deterioration of reinforced-concrete structures is recognised as a major problem worldwide. Apart from requiring regular maintenance, many structures require extensive repair, rehabilitation and retrofitting. Over a period of time, as these structures become older, certain degradation or deterioration with resultant distress manifested in the form of cracking, splitting, delaminating and corrosion is found in them. Such deteriorated structures can be rehabilitated and retrofitted by using various types of admixtures and modern repair materials. This paper discusses the present state of concrete structures and the major areas where improvement is needed during the service life stage for sustainable development. It also discusses the method of carrying out repair, rehabilitation and retrofitting. This is detailed in the paper along with various case studies compiled by the author based on his field experience of direct involvement in the planning and execution of repair and rehabilitation jobs, which were successfully completed by using the latest repair materials and techniques.

Rehabilitation/Retrofiting of Concrete Structures Along with Case Study

The construction material mainly concrete is being used extensively for various types of construction projects. However, the deterioration of Reinforced Concrete structures is recognized as a major problem worldwide. Apart from requiring regular maintenance, many structures require extensive Repair/Rehabilitation/Retrofitting. Over a period of time, as these structures become older, we find in them certain degradation or deterioration with resultant distress manifested in the form of cracking, splitting, delaminating, corrosion etc. Such deteriorated structures can be rehabilitated and retrofitted by using various types of admixtures & modern repair materials. The paper brings out the present state of concrete structures & the major areas where improvement is needed during its service life stage for sustainable development & also the method of carrying out Repair/Rehabilitation/Retrofitting.This has been brought in details in the paper along with Case study, where the Author of the paper was directly involved in planning and execution of job.

Corrosion Sensor for Monitoring the Service Condition of Chloride-Contaminated Cement Mortar

A corrosion sensor for monitoring the corrosion state of cover mortar was developed. The sensor was tested in cement mortar, with and without the addition of chloride to simulate the adverse effects of chloride-contaminated environmental conditions on concrete structures. In brief, a linear polarization resistance method combined with an embeddable reference electrode was utilized to measure the polarization resistance (Rp) using built-in sensor electrodes. Subsequently, electrochemical impedance spectroscopy in the frequency range of 1 kHz to 50 kHz was used to obtain the cement mortar resistance (Rs). The results show that the polarization resistance is related to the chloride content and Rs; ln (Rp) is linearly related to the Rs values in mortar without added chloride. The relationships observed between the Rp of the steel anodes and the resistance of the surrounding cement mortar measured by the corrosion sensor confirms that Rs can indicate the corrosion state of concrete structures.

A Computational Framework for Risk Assessment of RC Structures Using Indicators

The present article starts out by proposing a framework for risk assessment of RC structures utilizing condition indicators. Thereafter, the various building stones of the suggested framework are described. This description includes a summary of the basis for the probabilistic modeling of the initiation phases of chloride-induced corrosion of concrete structures. Furthermore, a probabilistic modeling of condition indicators regarding the condition state of concrete structures is proposed whereby information available at the design stage of concrete structures as well as information obtained through in-service inspections may be utilized for the purpose of reliability updating. Finally, it is described how the probability of localized and spatially distributed degradation of different degrees can be assessed and examples are given on how the various indicators may be used for the purpose of updating the statistical characteristics of the future degradation of RC structures. The presented framework forms a consistent basis for risk assessment of concrete structures subject to chloride-induced corrosion. It can easily be adopted to other degradation phenomena such as carbonation-induced corrosion and it forms a good basis for the development of efficient approaches to Asset Integrity Management of RC structures.