Concrete Corrosion Rate Research Articles

Preparation of Calcium Magnesium Acetate Snow Melting Agent Using Raw Calcium Acetate-Rich Made from Eggshells

A large number of discarded eggshells bring serious environmental pollution and waste of resources. To solve this problem, raw product of calcium acetate was prepared from waste eggshell by the ultrasonic assisted neutralization method, thus, the best material ratio of calcium and magnesium, a non-chloride environment-friendly snow melting agent, which took calcium acetate as raw material by optimizing the experimental conditions, was determined. In this paper, the eggshell powder with a recovery rate of 90% was firstly obtained through the separation of eggshells and shell membrane; then, calcium acetate was prepared with a high yield of about 95.29% using ultrasonic neutralization treatment and suction filtration, and its properties including the calcium content, pH, moisture determination, sulfate, chloride, etc. were characterized with satisfaction according to the national standard, China (GB/T 23851-2009, China), the U.S. Pharmacopeia and related literature. Furthermore, different ratios of calcium and magnesium products were prepared and its properties on the pH, freezing point, dissolution rate, ability to melt snow and ice, concrete corrosion rate, carbon steel corrosion rate and plant salt tolerance test, were compared with commercially available snow melting agents. The best snow melting agent with calcium to magnesium ratio of 5:5 was picked over to be a substitute for the chlorine salt snow melting agent which can reduce the environmental pollution by discarded eggshells caused. The results obtained also provided a new theoretical basis and credible experimental data for the preparation of environmentally friendly snow melting agents.

Sensitivity of chloride-induced corrosion rate of steel in concrete to cover depth, crack width and concrete quality

This paper presents the results of analyses carried out to assess the sensitivity of chloride-induced corrosion rate to change(s) in cover depth, concrete quality and crack width. An empirical chloride-induced corrosion rate prediction model is used to carry out the sensitivity analyses. The main model input parameters for the model are surface crack width (w cr), cover (c) and concrete quality (characterized by a long-term diffusion coefficient, D 90). A two tier sensitivity analysis is carried out to establish (i) which individual input parameter (D 90, c or w cr) corrosion rate is most sensitive to, and (ii) which combination of two input parameters out of the possible three (D 90, c and w cr) corrosion rate is most sensitive to. The sensitivity analyses results show that in cracked concrete change in corrosion rate is greater if concrete quality is varied than if either crack width or cover depth is varied i.e. concrete quality has a dominating role on the effect of either crack width or cover depth on corrosion rate. Generally, in cracked concrete corrosion rate is more sensitive to change in concrete quality than change in either crack width or cover depth. Even though cover cracking increases corrosion rate, and that it should be minimized, a holistic approach considering the effect of cover depth, crack width, and more importantly, concrete quality on corrosion rate should be adopted.

Performance indicator of the atmospheric corrosion monitor and concrete corrosion sensors in Kuwait field research station

Two field research stations based upon atmospheric corrosivity monitoring combined with reinforced concrete corrosion rate sensors have been established in Kuwait. This was established for the purpose of remote monitoring of building materials performance for concrete under Kuwait atmospheric environment. The two field research sites for concrete have been based upon an outcome from a research investigation intended for monitoring the atmospheric corrosivity from weathering station distributed in eight areas, and in different regions in Kuwait. Data on corrosivity measurements are essential for the development of specification of an optimized corrosion resistance system for reinforced concrete manufactured products. This study aims to optimize, characterize, and utilize long-term concrete structural health monitoring through on line corrosion measurement and to determine the feasibility and viability of the integrated anode ladder corrosion sensors embedded in concrete. The atmospheric corrosivity categories supported with GSM remote data acquisition system from eight corrosion monitoring stations at different regions in Kuwait are being classified according to standard ISO 9223. The two nominated field sites where based upon time of wetness and bimetallic corrosion rate from atmospheric data where metals and rebar's concrete are likely to be used. Eight concrete blocks with embeddable anodic ladder corrosion sensors were placed in the atmospheric zone adjacent to the sea shore at KISR site. The anodic ladder corrosion rate sensors for concrete were installed to provide an early warning system on prediction of the corrosion propagation and on developing new insights on the long-term durability performance and repair of concrete structures to lower labor cost. The results show the atmospheric corrosivity data of the environment and the feasibility of data retrieval of the corrosion potential of concrete from the embeddable sets of anodic ladder corrosion sensors.

Laboratory studies on influence of transverse cracking on chloride-induced corrosion rate in concrete

To clarify the corrosion mechanism of steel induced by transverse crack, a study on the influence of crack widths and epoxy coating on corrosion of steel bars in cracked concrete is presented here. Microcell and macrocell corrosions of bars were investigated on single crack specimens with crack widths of 0.08, 0.26, 0.38 and 0.94 mm. The entire study was carried out in an artificially created chloride ion-induced corrosion environment. The results show that the steel in cracks was activated once the transverse crack occurred on concrete element, and the macrocell corrosion must co-exist with microcell corrosion of reinforcements in test specimens with transverse crack. The macrocell current of steel elements were separated from the crack width, and the wider the transverse crack is, the higher corroded area and the greater microcell current of the rebar is. Oxygen and water go into concrete through crack instead of through concrete cover. The epoxy coating cannot prevent the occurrence and propagation of crack, so it was not effective to prevent corrosion of steel bars in cracked concrete.

Corrosion Rate of Steel in Fly Ash Concrete Containing Chlorides

In order to consider the durability of fly ash concrete against the chloride attack, quantitative evaluation of rebar corrosion rate in concrete is necessary. In this study, reinforced concrete specimens containing premixed chlorides were prepared, using concrete with cement or fine aggregate partly substituted by fly-ash. The corrosion rate of rebar embedded in the specimen was evaluated by measuring the polarization resistance which is an electrochemical corrosion index and one of the non-destructive techniques. As a result, the corrosion rate of rebar was greatly suppressed by admixing fly-ash at the environmental temperature of 20 degrees Celsius, while such suppression effect decreased with the rise of temperature to 40 degrees Celsius. The suppression effect was remarkable in the case of fly ash addition as the substitution of fine aggregate. Moreover, in the experimental conditions of this study, the influence of a variation of the chloride content in concrete on the corrosion rate of steel in concrete was not so significant. The influence of environmental temperature on the corrosion rate could be evaluated by an existing formula in the case of non-fly ash concrete, but the error became relatively high in the cases of fly ash concrete.

Global sensitivity analysis of an in-sewer process model for the study of sulfide-induced corrosion of concrete

The presence of high concentrations of hydrogen sulfide in the sewer system can result in corrosion of the concrete sewer pipes. The formation and fate of hydrogen sulfide in the sewer system is governed by a complex system of biological, chemical and physical processes. Therefore, mechanistic models have been developed to describe the underlying processes. In this work, global sensitivity analysis was applied to an in-sewer process model (aqua3S) to determine the most important model input factors with regard to sulfide formation in rising mains and the concrete corrosion rate downstream of a rising main. The results of the sensitivity analysis revealed the most influential model parameters, but also the importance of the characteristics of the organic matter, the alkalinity of the concrete and the movement of the sewer gas phase.

Development and prediction strategy of steel corrosion rate in concrete under natural climate

A long-term test on the steel corrosion in concrete was conducted under the sheltered conditions of a natural climate environment. A synchronous test under the sheltered and unsheltered conditions was performed to determine the microenvironment response and steel corrosion in concrete. The effect of environmental climate on the steel corrosion rate in concrete was further determined. The results show that the steel corrosion rate in concrete fluctuates and is time-dependent under natural climatic conditions. The changes of environmental conditions in the concrete microenvironment are less than those in a natural climate environment, particularly relative humidity. The steel corrosion rate in concrete is directly affected by the microenvironment of concrete, which depends on the random fluctuations of natural climate. Temperature is the primary climatic factor that affects the steel corrosion rate in concrete under an atmospheric environment. The pore water saturation of concrete is also a key factor that causes the differences between the steel corrosion rates in concrete under sheltered and unsheltered conditions. A prediction strategy for the steel corrosion rate in concrete under natural climate is proposed based on the effects of environment on the corrosion rate as well as on the responses of the concrete microenvironment.

A Discuss on Basing Half-Cell Potential Method for Estimating Steel Corrosion Rate in Concrete

Basing half-cell potential method estimating steel corrosion rate in concrete was studied in this paper. The exponential relationship between the corrosion current and the corrosion potential was regressed by the data collected from the linear polarization method experiment. Potential collected by the half-cell potential method and linear polarization resistance method in the experiment were close, it is reasonable to using regression equation. Regression equation was applied to analysis steel corrosion rate in a concrete structure column.

PENGARUH UNSUR – UNSUR KIMIA KOROSIF TERHADAP LAJU KOROSI TULANGAN BETON : I. DI DALAM AIR RAWA

Most of infrastructures using steel concrete to reinforce the strength of concrete. Steel concrete is so vulnerable to chemical compounds that can cause corrosion. It can happen due to the presence of chemical compounds in acid environment in low pH level. These chemical compounds are SO4 2-, Cl-, NO3 -. There are many swamp area in Indonesia. The acid contents and the concentration of ion sulphate, chlorides, and nitrate are higher in the swamp water than in the ground water .The objective of this research was to find out the influence of corrosive chemicals in the swamp water to the steel concrete corrosion rate. There were two treatment used: (1) emerging ST 37 and ST 60 within 60 days in the ‘polluted’ swamp water, (2) moving the ST 37 up and down periodically in the ‘ polluted’ swamp water. Three variation of ’polluted’ swamp water were made by increasing the concentration of corrosive chemical up to 1X, 5X and 10X respectively. The corrosion rate was measured by using an Immersion Method. The result of Immersion test showed that chloride had the greatest influence to corrosion rate of ST 37 and ST 60 and followed by sulphate and Nitrate. Corrosion rate value for ST 37 is 24.29 mpy and for ST 60 is 22.76 mpy. By moving the sample up and down, the corrosion rate of ST 37 increase up to 37.59 mpy, and chloride still having the greatest influence, followed by sulphate and nitrate.

Monitoring Method of Steel Reinforcement Corrosion Rate in Concrete

Steel reinforcement concrete is one of the most widely used composite materials in architectural and civil engineering. The alkaline of concrete makes steel passive state, so the steel bars in conrete are kept in anti-corroded phase. Carbon dioxide in atmosphere, however, chemically reacts to the alkaline components in long term, and the passive state of steel is missing. Steel corrosion in concrete is not visible but it may cause decaying buildings or civil construction. The author developed the electrochemical measurement method of monitoring steel corrosion rate in concrete. With the measurement method, the author measured the variety of corrosion rates of steel reinforcement in several atmospheres, such as indoors, outdoors, in-water, underground, and so on. In this paper, found and analyzed mechanisms of steel corrosion in those atmospheres are mainly shown. For an interesting result, the most corroded sample is not the sample exposed outdoor, nor exposed in water, but the sample exposed in wet room. This may cause the diffusion balance of oxygen and water in concrete.

Controlled treatment with nitrate in sewers to prevent concrete corrosion

It has generally been accepted that concrete corrosion is caused by bacterial oxidation of hydrogen sulphide in sewage systems. Costs related to sewer replacement and remediation are quite high, but there is limited knowledge and documentation on the relationship between hydrogen sulphide levels and corrosion rates. This is necessary information in order to select the appropriate means of hydrogen sulphide control and to conduct cost-benefit evaluations. This pilot scale study shows that the concrete corrosion rate can be modeled by a Monod type function with Ks=2 ppm H2S in gas and a maximum concrete corrosion rate at 25°C of 16 mm/year. Complete hydrogen sulphide control with 0 ppm H2S in water and gas is required to prevent concrete corrosion. This can be achieved by controlled treatment with nitrate using the Nutriox® Concept where the nitrate dose is based on flow, temperature, sewer design, and sewage concentration. The local conditions will be important for the cost-benefit evaluations, but in general terms, one can say that the longer the hydraulic retention time is, the more cost effective will a controlled treatment with nitrate be for corrosion control.