Long-term Performance of Nanoparticle Incorporated Eco-friendly Concrete in Natural Seawater Environment

The use of blended concrete has widely gained industrial importance owing to the CO2 gas emissions and carbon footprint resulting from the production of ordinary Portland cement (OPC). Despite the advancements, the deterioration of concrete structures raises a significant threat to their long term durability and service life in aggressive conditions. In this work, the long-term antifouling, strength and durability properties of a blended eco-friendly concrete with OPC, fly ash, nanoparticles, and corrosion inhibitor is evaluated in natural seawater for one year. The biofouling attachment, total viability count (TVC), mechanical strength, alkalinity and free chloride contents were measured and the results were compared with OPC concrete. A four-order reduction in the total biomass and total bacterial density is observed on the surface of the blended concrete. Further, a significantly lower chloride and water penetration depth, free chloride content, compact and smooth surface morphology devoid of cracks and high C-S-H content are observed in blended concrete, compared to the OPC concrete, after exposure in seawater for one year. From the results, it is seen that the blended concrete mix is promising for applications in seawater environments because of its superior biofouling resistance, mechanical properties and durability.

Assessment of river water infiltration conditions based on both chloride mass-balance and hydrogeological setting: the Krajkowo riverbank filtration site (Poland)

In the present work measurements of chloride concentrations were used to assess the variability of infiltration conditions and contributions of surface water and local groundwater to the discharge of wells at Krajkowo riverbank filtration site (western Poland). Tests were performed on samples from 26 wells located in a well gallery close to the River Warta. Due to higher chloride concentrations in river water in comparison with local groundwater, significant differences in concentrations in samples from individual wells were noted. In particular, lower chloride concentrations in 11 wells were recorded, which can be linked to the local occurrence of low-permeability deposits in the superficial zone; a locally higher degree of riverbed sediment clogging in the highly convex meandering zone, where strong erosion of the riverbed occurred, which in turn led to increased clogging; the occurrence of a more intensive groundwater inflow into the river valley due to water infiltration from a smaller river entering the River Warta valley, as well as unfavourable conditions for the infiltration of surface water to the lower part of the aquifer with a greater thickness. Differences in chloride concentrations observed were also used to quantify approximately river water contribution to the well production. The average contribution of the River Warta to the recharge of the entire well gallery was estimated at 59.8%.

Effects of Coal Bottom Ash as Cementitious Material on Compressive Strength and Chloride Permeability of Concrete

Coal Bottom Ash (CBA) is the waste material produced by coal-based power plants, particularly in Malaysia around 1.7 million tons of CBA was produced annually, which is major environmental concern. Therefore, the use of CBA as a partial replacement of cement in concrete is a possible solution for that pollution; this approach also creates a new corridor in the field of concrete production. However, this study aims to evaluate the effects of CBA as cementitious material on the concrete properties. This study incorporated 10% CBA as a cement replacement by weight method in concrete. However, concrete samples were prepared with and without CBA and immersed in water for 7, 28, 56 and 90 days. Next, the performances of concrete with and without CBA were evaluated in terms of workability, compressive strength, and rapid chloride permeability test. It was found that due to presence of CBA in concrete, workability reduces; no substantial growth in compressive strength at the early ages but substantial rise in strength was noticed after 56 days. Almost 4.7% higher strength was recorded than the control specimens at 90 days. Besides that, concrete containing CBA has lower chloride penetration as compared to the control specimen, which shows its better durability performance. It can be concluded that CBA has an enormous potential to be utilized as a cementitious material in durable concrete production.

P1592HYPOCHLOREMIA AND INFLAMMATION: RELATIONSHIP BETWEEN SERUM CHLORIDE LEVELS AND NEUTROPHIL-TO-LYMPHOCYTE RATIO IN INCIDENT CHRONIC HEMODIALYSIS PATIENTS

Background and Aims Recently the role of chloride in patients with heart failure has been reevaluated. Some studies have linked it to higher mortality in these patients, being more important, even, than sodium. On the other hand, some authors have found a higher mortality in patients with low chloride levels and sepsis. The underlying mechanisms in both cases are unknown. Some authors attribute it to concomitance with metabolic alkalosis, however, this is not a reason that fully explains these findings. Neutrophil-to-Lymphocyte Ratio (NLR) is an emerging marker of inflammation comparable to established ones such as C-reactive protein, ferritin, etc. It is also a good biomarker of mortality in certain populations such as cancer, cardiovascular and renal. Patients with chronic kidney disease on hemodialysis have high cardiovascular comorbidity and a high rate of inflammation. However, there are no studies that correlate chloride levels to inflammation markers, such as NLR, in this population. Therefore, the aim of our study was to determine if there is a relationship between chloride and NLR in our population of patients on chronic hemodialysis. Method Restrospective cohort study. We analyzed the values of chloride and NLR of 396 incident patients on hemodialysis over a period of 3 years (between 2016 and 2019). The patients were divided into three groups, depending on the levels of chloride (tertiles): (1: <100, 2: 100.1-103, 3> 103.1 mEq / l). In each group the average of NLR was calculated. Results The mean age in our sample was 64.73 ± 0.57 years, 39.7% were women (N = 157). The average of NLR was 3.84 ± 2.65 and chloride was 101.03 ± 3.91. We found that patients in the lower chloride level tertile were associated with a higher NLR levels (p <0.012). (Figure 1) Conclusion Incident hemodialysis patients with lower chloride levels had higher NLR values. These findings suggest a greater tendency to inflammation in these patients.

Effect of Calcium Stearate in the Mechanical and Physical Properties of Concrete with PCC and Fly Ash as Binders

This work aims to study the effect of Ca(C18H35O2)2 (calcium stearate) on the properties of concrete by using Portland composite cement (PCC) and fly ash as binders. The calcium stearate content used in the concrete here consists of 0, 1, 5, and 10 kg per m3 of concrete volume, or alternatively, 0 to 2.85% by the weight of cement. We have performed several tests for each of the contents, namely, compressive strength, water absorption, chloride ion infiltration, and accelerated corrosion tests. According to the testing, we have found that with the addition of calcium stearate at 1 kg/m3 in self-compacting concrete (SCC) with 10% fly ash, the mechanical and physical properties of SCC can be improved significantly when compared to the SCC without fly ash and calcium stearate, resulting in a stable compressive strength, lower water absorption, lower chloride ion infiltration, and lower degree of corrosion attack.

The Corrosion of Cast Duplex Stainless Steels in Seawater and Sour Brines

Modern duplex stainless steels have been in use since the early 1970s and cast versions of the wrought alloys were soon in demand for pumps and valves. Since that time a range of cast duplex stainless steels have been developed with a wide range of compositions, but all with approximately 50/50 austenite/ferrite phase balance and deliberate additions of nitrogen. This paper presents some comparative corrosion data on a range of cast duplex stainless steels, mainly in seawater. The differences in performance related to composition and microstructure are discussed. Corrosion data in lower chloride brines are also presented to show the limits of use of some lower alloyed duplex materials. In addition to oxidizing chloride solutions, some data are presented on cast duplex stainless steels in reducing brines containing H2S, where the main corrosion problem is sulfide stress corrosion cracking. Finally, the importance of using a suitable technical specification, over and above ASTM, combined with selecting a suitably skilled foundry in order to obtain satisfactory castings is discussed.

Chloride Diffusivity in Blended Cement Made from Selected Industrial and Agrowastes

This paper reports study findings on the diffusivity of chloride ions in potential blended cement. The cement, abbreviated as PCDC, was made from blending ordinary Portland cement (OPC) with dried calcium carbide residue and an incinerated mix of rice husks, spent bleaching earth, and broken bricks. The aim of the study was to investigate the ability of PCDC to withstand aggressive chloride environment. 10 cm × 10 cm mortar cubes were prepared using PCDC and cured for 28 days in saturated calcium hydroxide solution. The cured mortar cubes were subjected to aggressive chloride media in a laboratory set up. The test cement was subjected to chloride profile analysis with depth of cover as a function of w/c ratio and curing period in alternate dry and wet environments of 3.5 percent sodium chloride solution. The experiments were carried alongside neat OPC and OPC + 25% pulverised fuel ash (OPC + 25% PFA). Results showed that PCDC exhibited lower chloride ingress as the depth of cover increased. In conclusion, the study showed that PCDC was a potential cementitious material with high ability to withstand aggressive environment of chlorides.

The influence of SAPs on chloride ingress in cracked concrete

Super Absorbent Polymers (SAPs) have proven to be effective as a self-healing agent for regaining the liquid tightness of cracked concrete. This is due to their large swelling capacity which allows them to (partially) block cracks which are in contact with water or moisture. Additionally, they are able to release this water when the climate becomes drier, thereby promoting the autogenous healing capacity of the concrete matrix. The effect SAPs have on chloride migration into cracked concrete is still unknown. The swelling capacity of the SAPs might partially block the crack, but this does not necessarily mean that the chloride ingress into the crack is lower. Especially, since the porosity of concrete with SAPs is slightly higher when additional water is added to compensate for the loss in workability. This paper compares the chloride ingress in cracked mortar with and without SAPs. The specimens were saturated in a chloride solution during 1 or 5 weeks after which the chloride ingress could be visualised using silver nitrate. The specimens which healed prior to chloride saturation had a significantly lower chloride ingress. The SAPs were able to delay the chloride ingress, as well as limit the influence of the crack on the chloride ingress.

Chloride Ingress in Chemically Activated Calcined Clay-Based Cement

Chloride-laden environments pose serious durability concerns in cement based materials. This paper presents the findings of chloride ingress in chemically activated calcined Clay-Ordinary Portland Cement blended mortars. Results are also presented for compressive strength development and porosity tests. Sampled clays were incinerated at a temperature of 800°C for 4 hours. The resultant calcined clay was blended with Ordinary Portland Cement (OPC) at replacement level of 35% by mass of OPC to make test cement labeled PCC35. Mortar prisms measuring 40 mm × 40 mm × 160 mm were cast using PCC35 with 0.5 M Na2SO4 solution as a chemical activator instead of water. Compressive strength was determined at 28th day of curing. As a control, OPC, Portland Pozzolana Cement (PPC), and PCC35 were similarly investigated without use of activator. After the 28th day of curing, mortar specimens were subjected to accelerated chloride ingress, porosity, compressive strength tests, and chloride profiling. Subsequently, apparent diffusion coefficients (Dapp) were estimated from solutions to Fick’s second law of diffusion. Compressive strength increased after exposure to the chloride rich media in all cement categories. Chemically activated PCC35 exhibited higher compressive strength compared to nonactivated PCC35. However, chemically activated PCC35 had the least gain in compressive strength, lower porosity, and lower chloride ingress in terms of Dapp, compared to OPC, PPC, and nonactivated PCC35.