POTENTIAL VOLUMIZING EFFECT OF THE POST-MORPH LIME FILLER IN ATTENUATING CONCRETE CARBONATION

A study on the crystallography of the lime that comes from mussel shell has been conducted to determine the packing density of the material. The experimental analysis encompasses of concrete samples preparation with lime replacement at 5%, 7.5% and 10% by cement weight. The samples were carbonised naturally over a period of six months and subjected to the phenolphthalein test at 60, 90, 120 and 180 days. It has been found that lime originating from the mussel shell is of both the aragonitic and calcitic crystal types. Both crystal polymorphs of aragonite and calcite are denser than the typical normal concrete by 27.8% and 18.3% respectively. This suggest a volumizing effect that is beneficial to reduce carbonation penetration into the capillarity of the concrete. Results from the carbonation test indicate that concrete containing mussel shell lime ash showed up to 51% lower carbonation coefficient and significantly lower intensity of capillarity as shown via FESEM. ABSTRAK: Kajian mengenai kristalografi kapur yang didapati daripada kulit kupang telah dijalankan bagi menentukan kepadatan bahan tersebut. Analisis eksperimen merangkumi penyediaan sampel-sampel konkrit yang mengandungi gantian kapur pada 5%, 7.5% dan 10% daripada berat simen. Sampel-sampel telah dikarbonatkan secara alami selama enam bulan dan menjalani ujian fenolftalin pada usia 60, 90, 120 dan 180 hari. Kajian telah mendapati bahawa kulit kupang terdiri daripada kapur-kapur berjenis aragonit dan kalsit. Kedua-dua polimorf kapur aragonit dan kalsit adalah 27.8% dan 18.3% lebih tumpat berbanding konkrit biasa. Hal ini berpotensi menjadi bahan penumpat yang bagus untuk mengurangkan serapan pengkarbonatan ke dalam kapilari konkrit. Keputusan ujian pengkarbonatan menunjukkan konkrit yang mengandungi abu kapur kulit kupang mempunyai pekali pengkarbonatan sehingga 51% lebih rendah dan mempunyai kerendahan kapilariti yang signifikan seperti yang ditunjukkan melalui FESEM.

Corrosion-Fatigue Life Prediction Modeling for RC Structures under Coupled Carbonation and Repeated Loading

The coupled action of concrete carbonation and repeated loading strongly influences the safety of reinforced concrete (RC) structures and substantially reduces service life. A novel corrosion-fatigue life prediction model for RC structures under coupled carbonation and repeated loading was developed. The effect of fatigue damage on concrete carbonation and carbonation-induced corrosion rate was considered, and the acceleration of fatigue damage accumulation due to reinforcement corrosion was considered in this approach. The proposed corrosion-fatigue life prediction model was illustrated by a 6 m-span RC slab in a simply supported slab bridge for the highway, and the effects of traffic frequency, overloading, carbonation environment grade, and environmental temperature and relative humidity on corrosion-fatigue life were discussed. The results indicate that the proposed model can predict the corrosion-fatigue life of RC structures simply and conveniently. Traffic frequency, overloading, carbonation environment grade, and environmental temperature and relative humidity can decrease the corrosion-fatigue life of the RC slab by up to 66.86%, 58.90%, 77.45%, and 44.95%, respectively. The research is expected to provide a framework for the corrosion-fatigue life prediction of RC structures under coupled carbonation and repeated loading.

Visible Corrosion Damage in Carbonated Reinforced Concrete

This study discusses visible corrosion damage due to carbonation in concrete balconies and facades. The focus of the study was to find out how the age of the structure, cover depth of concrete, carbonation coefficient, capillarity of concrete and the climate affect visible corrosion damage. The research data consist of condition investigation reports of existing concrete balconies and facades built between 1948 and 1996. Balcony slabs and brushed painted facades were the most prone to visible corrosion damage. None of the researched panels met the required minimum cover depth of reinforcement even at the time of construction. However, most of the visible damage on the database was localized damage and there was not much visible corrosion damage. The carbonation coefficient of balconies was higher than the carbonation coefficient of facades. Brushed painted facade panels had clearly higher carbonation coefficient than other facade panels. The carbonation coefficient was considerably lower on white concrete panels compared to other panel types. When capillarity of concrete raises, the carbonation rate of concrete increases slightly. However, no correlation can be seen. The capillarity of concrete and the carbonation rate of concrete had a major range.

Time impacts of treating pervious concrete with sodium bicarbonate

Magnesium chloride (MgCl2) deicers applications onto pervious concrete pavements can deteriorate the material, and studies investigate treatments to increase the concrete resistance to MgCl2 attacks. In this paper, pervious concrete specimens are subjected to a treatment with Sodium Bicarbonate (NaHCO3) solution, which seems to accelerate concrete carbonation and might hamper chemical reactions between MgCl2 deicer and hydroxides in cement mortar. All specimens had their compressive strength tested and the time frames before and after treatment varied. Results show that at least 2 months should be given post curing before treatment to not harm the concrete, and longer post treatment periods may be beneficial.

Time Impacts of Treating Pervious Concrete with NaHCO3

Magnesium chloride deicers applications onto pervious concrete pavements can deteriorate the material, and studies investigate treatments to increase the concrete resistance to MgCl2 attacks. In this paper, pervious concrete specimens are subjected to a treatment with NaHCO3 solution, which seems to accelerate concrete carbonation and might hamper chemical reactions between MgCl2 deicer and hydroxides in cement mortar. All specimens had their compressive strength tested and the time frames before and after treatment varied. Results show that at least 2 months should be given post curing before treatment to not harm the concrete, and longer post treatment periods may be beneficial.

Climatic Issue in an Advanced Numerical Modeling of Concrete Carbonation

Damage in reinforced concrete structures is frequently caused by reinforcement corrosion due to carbonation. Although a wide range of literature contributed to the concrete carbonation consisting of experimental investigations and numerical simulations, research work on a complete numerical model for concrete carbonation prediction with integrated climatic variables (e.g., temperature, relative humidity) is still a challenge. The present paper aims to propose an advanced numerical model to simulate the penetration of carbon dioxide and moisture, diffusion of calcium ions, heat transfer, and porosity modification in concrete material using COMSOL Multiphysics software. Three coupled mass conservation equations of calcium, water, and carbon dioxide are solved together with additional equations regarding the heat transfer, variation of porosity, and content of portlandite and other hydrates and calcites. In this study, the actual temporal variabilities of temperature and relative humidity in Toulouse, France, are used as a case study. The predicted results of portlandite profiles and carbonation depth are compared with the experimental data and discussed to identify the effect of climatic variables on the concrete carbonation.