Chloride Ion Penetration Test Research Articles

Durability of recycled aggregate concrete using pozzolanic materials

In this study, pulverized fuel ash (PFA) and ground granulated blast furnace slag (GGBS) were used to compensate for the loss of strength and durability of concrete containing recycled aggregate. As a result, 30% PFA and 65% GGBS concretes increased the compressive strength to the level of control specimens cast with natural granite gravel, but the tensile strength was still lowered at 28 days. Replacement with PFA and GGBS was effective in raising the resistance to chloride ion penetrability into the concrete body, measured by a rapid chloride ion penetration test based on ASTM C 1202-91. It was found that the corrosion rate of 30% PFA and 65% GGBS concretes was kept at a lower level after corrosion initiation, compared to the control specimens, presumably due to the restriction of oxygen and water access. However, it was less effective in increasing the chloride threshold level for steel corrosion. Hence, it is expected that the corrosion time for 30% PFA and 65% GGBS concrete containing recycled aggregate mostly equates to the corrosion-free life of control specimens.

폴리카르본산계 조강혼화제 혼합 콘크리트의 강도 및 내구 특성

This study reports the properties of high early strength & durability of concrete using PC admixture. To apply these data to construction site, we did the lab tests. The target of this study is to accomplish early strength of concrete (5.0 Mpa/18 hr), and we did the durability tests such as length change test, chloride ion penetration test, fleeting and thawing test, adiabatic test, etc. And we tested the porperties of concrete by the different factors, such as the type of admixtures, curing temperature, the amount of binder, etc. Through the test of concrete using the different type of admixture, PC type was more excellent than PNS type admixture. As a result, we made a concrete of high early strength concrete, and excellent durable concrete. According to these tests, we concluded that we can apply this type of PC admixture to the civil & construction site, and we can reduce the term of works and finally we will accomplish the economical construction.

Evaluation of Cementitious Repair Mortars for Corrosion Resistance

Repair and rehabilitation of deteriorated concrete structures are essential not only to utilize them for their intended service life, but also to assure the safety and serviceability of the associated components. A good repair improves the function and performance of the structure, thus prevents ingress of aggressive species to the steel/concrete interface and improves its durability. It is important to evaluate the performance of repair materials available for repairing the deteriorated concrete structures. This investigation was carried out to evaluate the durability characteristics of five types of modified cement based repair mortars. The corrosion resistance of the repair materials was evaluated by conducting various tests such as water absorption, rapid chloride ion penetration test, impressed voltage, 90 days ponding test, macro cell corrosion test, weight loss measurement, etc. Details of the test and their results were discussed. It is concluded that the modified cement based repair mortars formulated with different mineral admixtures (fly ash and/or silica fume) showed improved corrosion resistance.

복합양생에 의한 폴리머 시멘트 모르타르의 성질

Concrete is much more easily damaged by various parameters than by the only one and performance reducing mechanism grows more complicated in that condition. In addition, the factors which really act in concrete structure tend to be activated in turn and the degradation of concrete is very rapidly progressed. The purpose of this study is to evaluate the properties of polymer cement mortars under combined cures. The polymer cement mortars are prepared with various polymer types, polymer-cement ratios and cement-fine aggregate ratio, and tested for compressive and flexural strengths, accelerated carbonation, chloride ion penetration and acid resistance test, and freezing-thawing test. The properties of polymer cement mortars under combined cures is discussed. From the test results, polymer cement mortars have superior strengths compared with plain cement mortar under combined cures. The strengths of polymer cement mortars are markedly increased at curing condition II and V, however strengths are not improved at curing condition I and IV irregardless of polymer types. The carbonation and chloride ion penetration depths of polymer cement mortars tend to decrease in curing conditions, III-C, IV-B, V-A order, and decrease with increasing polymer cement ratios. It is concluded that polymer cement ratio of 10 to 15% are considered optimum for the preparation of such polymer cement mortars.

Analysis of corrosion resistance behavior of inhibitors in concrete using electrochemical techniques

Reinforced concrete is one of the most durable and cost effective construction materials. However, in high chloride environments, it can suffer from corrosion due to chloride induced breakdown of the normal passive layer protecting the reinforcing steel bars inside concrete. One means of protecting embedded steel reinforcement from chloride induced corrosion is the addition of corrosion inhibiting admixtures. In the present investigation, various inhibitors such as sodium nitrite, zinc oxide, mono ethanol amine, diethanolamine, and triethanol amine have been used in concrete in different percentages. Their effectiveness was then studied using various electrochemical techniques such as rapid chloride ion penetration test, open circuit potential measurement, electrochemical impedance measurement, potentiodynamic polarization measurement, and gravimetric weight loss measurement. The results thus obtained indicate that the addition of inhibitors enhances the corrosion resistance properties.

Electrochemical studies on the corrosion performance of steel embedded in activated fly ash blended concrete

The use of fly ash to replace a portion of cement has resulted significant savings in the cost of cement production. Fly ash blended cement concretes require a longer curing time and their early strength is low when compared to ordinary Portland cement (OPC) concrete. By adopting various activation techniques such as physical, thermal and chemical methods, hydration of fly ash blended cement concrete was accelerated and thereby improved the corrosion-resistance of concrete. Concrete specimens prepared with 10–40% of activated fly ash replacement were evaluated for their open circuit potential measurements, weight loss measurements, impedance measurements, linear polarization measurements, water absorption test, rapid chloride ion penetration test and scanning electron microscopy (SEM) test and the results were compared with those for OPC concrete without fly ash. All the studies confirmed that up to a critical level of 20–30% replacement; activated fly ash cement improved the corrosion-resistance properties of concrete. It was also confirmed that the chemical activation of fly ash yielded better results than the other methods of activation investigated in this study.

순환골재 및 고로슬래그 시멘트를 사용한 증기양생 콘크리트의 강도 특성

There are some problems in utilizing recycled concrete aggregate go structural use because of the difficulties concerning about quality control and durability. It seems to be possible to utilize recycled concrete aggregate for making concrete products because quality control of concrete products is easier than ready-mixed concrete, but there are little studies about the properties of the steam-cured recycled aggregate concrete. In this study, various tests were performed such as compressive strength, flexural strength, splitting tensile strength, bonding strength and chloride ion penetration test to evaluate the effect of substitution of recycled concrete aggregate. The results of strength test showed that the concrete strength decreased with the increase of the substitution ratio of recycled concrete aggregate, but it was in the reasonable range and almost equal to that of normal concrete below the substitution ratio of . On the other hand, strength test of furnace slag cement concrete shows that the strength of recycled concrete with furnace slag cement under curing condition lower than that of recycled concrete with ordinary portland cement under same condition. From the result of this study, it can be concluded that recycled concrete aggregate is able to be utilized for structural use but substitution ratio should be decided with care in each case. The result of this study could be used as the basic data for the structural use of recycled concrete aggregate.

증기양생 재생콘크리트의 강도특성에 관한 실험연구

Various tests are performed with the recycled concrete including compressive strength, flexural strength, splitting tensile strength, bonding strength and chloride ion penetration test. The basic data obtained from the presented test could be accumulated for the purpose of utilization in concrete structure. Most of the strength tests show that strength decrease a little extent with increasing substitution ratio of recycled coarse aggregate except splitting tensile test for the concrete with <TEX>$100\%$</TEX> recycled fine aggregate. But in case of the <TEX>$50\%$</TEX> substitution of recycled coarse aggregate, compressive strength, flexural strength and bonding strength are almost equal to the normal concrete. Chloride ion penetration test shows that the penetration amounts of chloride ion becomes more in proportion to the substitution ratio of recycled aggregate. But most of the results show that the permeability of recycled concrete is proper to use. The results of present study nay imply that the use of recycled aggregate for steam curing concrete is possible but the substitution ratio of recycled aggregate should be determined through further studies.

고내구성콘크리트의 염해저항성에 관한 실험적 연구

In this paper, salt damage resistance of high durable concrete was tested. High durable concrete was made by using low water cement ratio, chemical admixture called super-durable admixture and mineral admixtures such as fly-ash, ground granulated blast-furnace slag, silica fume. Two kinds of salt damage resistance test were carried out. One method is chloride ion penetration test(ASTM C1202), and the other one is depth of chloride penetration test in saline solution. Test results were as followers: 1) The depth of chloride ion penetration increased exponentially as water cement ratio was increased and time passed. 2) Super-durable admixture had little effect on the improvement of salt damage resistance of concrete. 3) Silica fume and ground granulated blast-furnace slag were effective on salt damage resistance because of pozzolanic reaction, but fly-ash had a little effect.

Performance of concrete mixes with OPC?PFA blends

This paper describes a comprehensive programme of testing for strength, durability (sorptivity, carbonation, drying shrinkage, sulphate attack and chloride ingress) and fresh-state properties (slump, slump loss, setting time, temperature rise and plastic shrinkage) of grade 25 and 35 concretes, where the ordinary Portland cement (OPC) binder was replaced with 15% and 25% of pulverised fuel ash (PFA). Three types of OPC–PFA mixes, designated ‘safe’, ‘workable’ and ‘economical’, were investigated. In general, the results from the PFA mixes were similar to or better than the OPC control mixes. The charge passed in the indirect chloride ion penetration test and the heat of hydration temperature rise were considerably reduced in the PFA mixes. They were however more susceptible to plastic shrinkage cracking. It was also found that the strength ratio between PFA mixes and OPC controls was slightly greater at 3 days than at 7 days, after which this ratio increased again, as expected.

Performance of concrete mixes with OPC–PFA blends

This paper describes a comprehensive programme of testing for strength, durability (sorptivity, carbonation, drying shrinkage, sulphate attack and chloride ingress) and fresh-state properties (slump, slump loss, setting time, temperature rise and plastic shrinkage) of grade 25 and 35 concretes, where the ordinary Portland cement (OPC) binder was replaced with 15% and 25% of pulverised fuel ash (PFA). Three types of OPC–PFA mixes, designated ‘safe’, ‘workable’ and ‘economical’, were investigated. In general, the results from the PFA mixes were similar to or better than the OPC control mixes. The charge passed in the indirect chloride ion penetration test and the heat of hydration temperature rise were considerably reduced in the PFA mixes. They were however more susceptible to plastic shrinkage cracking. It was also found that the strength ratio between PFA mixes and OPC controls was slightly greater at 3 days than at 7 days, after which this ratio increased again, as expected.

Chloride-ion induced corrosion of galvanized and ordinary steel reinforcement in high-performance concrete

An experimental investigation has been carried out to assess the effectiveness of the use of high-performance concrete (HPC) and galvanized steel in reducing reinforcement corrosion. Two normal strength concrete (NSC) mixtures with 28-day compressive strengths of 30 and 40 MPa and two high strength concrete (HSC) mixtures with compressive strengths of 50 and 80 MPa were used for this study. The rapid chloride ion penetration test was used to study the ion penetration and the results are compared with the results of long-term immersion tests in 4% NaCl solution over a period of 1 year. No correlation between the results of these two tests could be established. Half-cell potential measurements were used to monitor the initiation of corrosion. The pH of HPC pastes and mortars were monitored for 90 days to study the effect of silica fume on pH of concrete and corrosion initiation. The results showed that HPC reduced chloride ion penetration significantly. Silica fume at 10% replacement level reduced the pH of concrete from 14.00 to 12.8 over a period of 90 days.