Papers by Keyword: Chloride Penetration

Abstract: Scrap tyres disposal revival the environmental concern except if recycled in an eco-friendly way. The inclusion of waste tyre crumb rubber (WTCRs) as a partial replacement of natural aggregate can be possible solutions for those concern. Thus, this study investigates the effect of using WTCRs at various contents (5, 10, 20 and 30% of volume) as a replacement agent of fine or/and coarse aggregate on water absorption, carbonation depth and chloride ion penetration rubberised concrete prepared with 20% ground blast furnace slag (GBFS) as Portland cement (OPC) replacement. Twelve batches are prepared by mixing the industrial wastes of GBFS and WTCRs. The results shown that modified rubberised containing 5% WRTCs as a substitute to natural aggregate, provided high durable performance such as lower water absorption, carbonation depth and chloride ion penetration compared to control specimen of traditional concrete. However, the rubberised concrete durability performance slightly trends to decrease with increasing WRTCs content from 5% to 30%, these proposed mix designs have a high potential for a wide variety of concrete industrial applications, especially in acid and sulphate risk.

Abstract: Alternating-current method for measuring chloride penetration resistance of concrete, test method for coulomb electric flux and rapid chloride migration coefficient (RCM) were applied to evaluate the resistance of chloride penetration in alkali-activated slag concrete in this paper. At the same time, the applicability of the above three electrical parameters test methods to the alkali slag concrete was discussed. The results show that NaOH activated slag concrete behaves higher resistance to chloride penetration than water glass activated slag concrete. Blend of fly ash increases the porosity of alkali-activated slag concrete and weakens the resistance of chloride penetration. Correlation coefficient between chloride migration coefficient and AC electrical resistivity is 0.99. There are good correlations among the evaluation results of three electrical parameters test methods, and all of them behave sound applicability to alkali-activated slag concrete.

Abstract: This paper presents a study that aimed to assess the chloride penetration depth of recycled aggregate concrete (RAC) modified by using treated coarse recycled concrete aggregate (RCA), adding polyolefin (PO) or polypropylene (PP) fibre and comparing with normal concrete. The coupling effects of the treated RCA and fibres on the chloride penetration of RAC were analysed after two different curing regimes (i.e. normal and seawater) and tested at different curing ages (i.e. 90, 180 and 300 days). Results showed that the inclusion of treated coarse RCA can reduce porosity, thereby decreasing the chloride penetration of RAC. However, the coupling effects of treated coarse RCA and fibre, especially on the use of PO fibre, can enhance the results.

Abstract: The paper was removed due to copyright misconduct (missing consensus from all co-authors)

Abstract: The paper was removed due to copyright misconduct (missing consensus from all co-authors)

Abstract: Supplementary cementitious materials such as fly ash, silica fume and ground granulated blast furnace slag (GGBS) have been used widely to partially replace cement in producing self-consolidating concrete (SCC). The production of cement is associated with emission of significant amounts of CO₂ and increases the human footprint on the environment. Fly ash, silica fume, and GGBS are recycled industrial by-products that also impart favorable fresh and hardened properties on concrete. This study aims to assess the effect of the amounts of fly ash and silica fume on strength and chloride penetration resistance of concrete. Rapid Chloride Penetration Test (RCPT) was used to assess the ability of SCC to resist ingress of chlorides into concrete. SCC mixes with different dosages of fly ash and silica fume were developed and tested at different curing ages. Test results showed that replacing 20% of cement with fly ash produced the highest compressive strength of 67.96 MPa among all fly ash-cement binary mixes. Results also showed that replacing15% of cement with silica fume produced the highest compressive strength of 95.3 MPa among fly ash-cement binary mixes. Using fly ash and silica fume consistently increased the concrete resistance to chloride penetration at the early ages. Silica fume at all dosages results in low or very low levels of chloride penetration at all curing ages of concrete.

Abstract: The chloride permeability of concrete (UHPC) was evaluated by means of the Rapid chloride permeation test and and standard difusion test. The tests are different in the voltage applied for accelerating the transport through the concrete specimen. The permeability strongly depends on quality and curing time of the concrete.

Abstract: The influence of an applied high compressive load on strength of concrete has been studied both theoretically and experimentally in great detail in the past. It was observed that load bearing capacity of concrete decreases under the influence of sustained compressive stress. In this contribution the influence of high sustained compressive stress on capillary absorption and on chloride penetration will be described. It was found that under the influence of moderate sustained compressive load the amount of capillary absorbed water decreases. If the sustained compressive load overcomes 50 % of the material’s strength, the rate of capillary absorption increases. This fact can be explained by reduction of the pore space under moderate compressive stress and formation and time-dependent growth of micro-cracks in the composite structure of concrete. Dissolved chloride is filtered out of the aqueous salt solution and remains accumulated in a surface near layer. In this way a high concentration difference of chloride is built up in a short time. This gradient leads to long lasting diffusion of chloride deeper into the pore space. As the diffusion coefficient of dissolved ions in the pore liquid increases with increasing applied compressive load, service life of structural elements under high compressive load will be reduced significantly when exposed to aggressive environment. This fact has to be taken into consideration if service life of reinforced concrete structures is to be predicted in a realistic way.

Abstract: In most national and international codes for durability design, service life is estimated after selection of one single and dominant deteriorating process such as carbonation, chloride penetration or frost attack. Application of existing codes has shown, however, that the predicted service life is not reached in practice in most cases. Early damage occurs and as a consequence expensive repair measures become frequently necessary, long before the design service life is reached. One reason for this discrepancy is certainly the fact that in practice each dominant deteriorating process is usually accompanied by other aggravating processes. In this contribution capillary absorption of different types of concrete is studied first. The influence of an increasing number of freeze-thaw cycles on capillary absorption of water is studied first, then chloride penetration before and after exposure to a certain number of freeze-thaw cycles was determined experimentally. It was found that an increasing number of freeze-thaw cycles increases chloride penetration significantly, and hence reduces service life in aggressive environment. It can be concluded that for realistic service life prediction the interaction between frost damage and chloride penetration has to be taken into consideration in regions with low temperatures.

Abstract: Chloride ingress is one of the major causes of durability problems in reinforced concrete structures. This research focused to investigate the chloride penetration process through the concrete subjected to wetting and drying cycle. This research used 150 x 150 mm normal concrete prism sample with a 40 mm concrete cover. Three wetting and drying configurations used in this study to investigate the effect of wetting and drying period to the chloride penetration. The result indicated that the chloride concentration and penetration depth were highly influenced by the duration of wetting and drying. Based on the experimental result, concrete exposed to 5 hours drying and 3 hours wetting has the highest chloride concentration compared with the sample exposed to other wetting and drying configuration.