Development of an electro-chemical accelerated ageing method for leaching of calcium from cementitious materials

Babaahmadi, Arezou; Tang, Luping; Abbas, Zareen; Zack, Thomas; Mårtensson, Per

doi:10.1617/s11527-015-0531-8

Cited by 15 publications

(8 citation statements)

References 19 publications

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“…It is known that the bonding component in cementitous material is mainly C–S–H, where Ca is the important consisting element. The loss of Ca will cause the degradation of C–S–H and thus the failure of bonding capability, which is consistent with the finding in Ref [ 23 ]. Consequently, both the accumulation of NaCl and the loss of Ca at the anode will cause the loss of shear strength of the interface and the increase of electrical resistance over time.…”

Section: Resultssupporting

confidence: 92%

Polarization Induced Deterioration of Reinforced Concrete with CFRP Anode

et al. 2015

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This paper investigates the deterioration of reinforced concrete with carbon fiber reinforced polymer (CFRP) anode after polarization. The steel in the concrete was first subjected to accelerated corrosion to various extents. Then, a polarization test was performed with the external attached CFRP as the anode and the steel reinforcement as the cathode. Carbon fiber reinforced mortar and conductive carbon paste as contact materials were used to adhere the CFRP anode to the concrete. Two current densities of 1244 and 2488 mA/m2, corresponding to the steel reinforcements were applied for 25 days. Electrochemical parameters were monitored during the test period. The deterioration mechanism that occurred at the CFRP/contact material interface was investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The increase of feeding voltage and the failure of bonding was observed during polarization process, which might have resulted from the deterioration of the interface between the contact material and CFRP. The formation and accumulation of NaCl crystals at the contact material/CFRP interface were inferred to be the main causes of the failure at the interface.

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Section: Resultssupporting

confidence: 92%

Polarization Induced Deterioration of Reinforced Concrete with CFRP Anode

et al. 2015

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“…Na + and K + ions have higher solubility and mobility in the pore solution than that of Ca 2+ ions. As a consequence, Na + and K + ions will dominate the diffusion and/or migration process more significantly in the beginning of the tests, and will not vary substantially on later stages, as also reported by Babaahmadi et al (Babaahmadi et al 2015). As can be observed in Figs.…”

Section: Chemical Analysis Of the External Mediumsupporting

confidence: 81%

Stray Current-Induced Development of Cement-Based Microstructure in Water-Submerged, Ca(OH)<sub>2</sub>-Submerged and Sealed Conditions

Susanto

Koleva

Breugel

et al. 2017

ACT

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This work reports on the development of microstructural and mechanical properties of mortar cubes under the synergetic action of stray current and various environmental/curing conditions. The study refers to specimens cured for 24h only, followed by a 112 days period of partial or full submersion in water or alkaline medium. Additionally, equally prepared mortar specimens were tested in sealed conditions. The outcomes for submerged and saturated conditions were compared to sealed conditions. Three current density regimes were employed i.e. 1 A/m 2 , 100 mA/m 2 , and 10 mA/m 2 , simulating different levels of stray (DC) current environment. The highest level of 1A/m 2 was also comparable to stray current densities, as measured in field conditions. The tests were designed in a way, so that the effects of diffusioncontrolled transport (ions leaching due to concentration gradients), were distinguished from migration-controlled ones (ion/water transport in stray current conditions). Mechanical, microstructural and electrical properties were monitored throughout the test. For water-conditioned specimens, the stray current was found to accelerate degradation processes. This was reflected by decreased compressive strength, reduced electrical resistivity and increased porosity of the matrix. The results were attributed to leaching-out of alkali ions due to concentration gradients, where except diffusion, migration took place i.e. the leaching-out effect was accelerated by water and ions migration in conditions of stray current flow. In contrast, stray current flowing through mortar in sealed conditions (as well as through mortar in alkaline medium) resulted in increased compressive strength and electrical resistivity. These were accompanied by densification of the bulk matrix and reduced porosity. It can be concluded that for a cement-based material at early hydration age, both positive and negative effects of stray current flow can be expected. The level and direction of these effects are dependent on the external environment and the current density levels, where stray currents above 100 mA/m 2 and in conditions of concentration gradients with the external medium, would lead to more pronounced negative effects on microstructural and micromechanical performance.

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“…As it is concluded by Babaahmadi et al (Babaahmadi et al 2015), with a current density of 125-130 A/m 2 an approximately 53 days of experimental time is predicted to reach to complete leaching of Portlandite for a paste specimen of Ø50 9 75 mm and W/C-ratio of 0.5. In this study similar experimental time (53 days) was chosen for the specimens.…”

Section: Electrochemical Acceleration Methodsmentioning

confidence: 73%

“…Concrete specimens were depleted in calcium by the use of a newly developed method for accelerated calcium leaching of solid specimens of flexible size (Babaahmadi et al 2015). As illustrated in Fig.…”

Section: Electrochemical Acceleration Methodsmentioning

confidence: 99%

Physical and Mechanical Properties of Cementitious Specimens Exposed to an Electrochemically Derived Accelerated Leaching of Calcium

Babaahmadi

Tang

Abbas

et al. 2015

International Journal of Concrete Structures and Materials

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Simulating natural leaching process for cementitious materials is essential to perform long-term safety assessments of repositories for nuclear waste. However, the current test methods in literature are time consuming, limited to crushed material and often produce small size samples which are not suitable for further testing. This paper presents the results from the study of the physical (gas permeability as well as chloride diffusion coefficient) and mechanical properties (tensile and compressive strength and elastic modulus) of solid cementitious specimens which have been depleted in calcium by the use of a newly developed method for accelerated calcium leaching of solid specimens of flexible size. The results show that up to 4 times increase in capillary water absorption, 10 times higher gas permeability and at least 3 times higher chloride diffusion rate, is expected due to complete leaching of the Portlandite. This coincides with a 70 % decrease in mechanical strength and more than 40 % decrease in elastic modulus.

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Development of an electro-chemical accelerated ageing method for leaching of calcium from cementitious materials

Cited by 15 publications

References 19 publications

Polarization Induced Deterioration of Reinforced Concrete with CFRP Anode

Polarization Induced Deterioration of Reinforced Concrete with CFRP Anode

Stray Current-Induced Development of Cement-Based Microstructure in Water-Submerged, Ca(OH)<sub>2</sub>-Submerged and Sealed Conditions

Physical and Mechanical Properties of Cementitious Specimens Exposed to an Electrochemically Derived Accelerated Leaching of Calcium

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