Effects of Temperature and Curing Duration on the Stability of Slag Cements in Combined Chloride-Sulphate Environments

This experimental study investigates the effects of temperature and curing duration on the stability of slag blended cement systems exposed at 20 °C and 38 °C to combined sodium chloride (30 g/L) – sodium sulphate (3 g/L) solutions. Two slags, designated as slag 1 and 2, having CaO/SiO2 ratios of 1.05 and 0.94, were respectively blended with Portland cement CEM I 52.5R at 30 wt.% replacement level. Mortar prisms and cubes with w/b ratio of 0.5 and binder/aggregate ratio of 1:3 were then prepared for length and mass changes. The samples were cured in lime water for either 7 or 28 days before ponding for a total exposure period of 544 days. Analogous paste samples were also prepared to follow changes in the hydration products using x-ray diffraction (XRD). The results showed that curing at 38°C resulted in less expansion and prolonged curing generally reduced expansion except for slag 1 blend at 20 °C. Also, mass-change was minimal at 38 °C compared to 20 °C, and curing up to 28 days further improved mass stability. There was a positive correlation between mass change and length change for the period of investigation

Engineering Performance of a New Siloxane-Based Corrosion Inhibitor

This paper presents an evaluation of a new non-toxic corrosion inhibitor on selected engineering properties of concrete mixes with different cementitious materials following a corrosion and durability study on concrete samples. Corrosion inhibitors consist of powders or solutions which are added to concrete when mixed to prevent or delay corrosion of steel by their reaction with ferrous ions to form a stable and passive ferric oxide film on the steel surface. The new inhibitor functions slightly differently and its corrosion inhibition effect is due to the formation of a siloxane coating on the steel surface. Therefore, the performance of the new inhibitor in concrete mixes manufactured with CEM I, PFA and GGBS cements was compared against a well known and established corrosion inhibitor on the market, namely calcium nitrite in terms of their effect on workability (measured in terms of slump), compressive strength, freeze–thaw durability and macro-cell corrosion. The results from this experimental programme have demonstrated that the new inhibitor is effective in reducing or slowing down corrosion. In addition, it was found that CEM I concrete containing the new inhibitor was less penetrable to chlorides than that without. A similar set of results was obtained for the freeze– thaw resistance, but the compressive strength was found to decrease with the addition of the new inhibitor. In the case of concretes containing PFA and GGBS, the new inhibitor was found to be less effective. Further, long-term investigations are recommended to assess the effectiveness over time

Methods of assessing the durability and service life of concrete structures

Characterisation of cover concrete is often the most viable means for assessing the durability and has become increasingly evident over the past 20 years. A variety of field methods and laboratory techniques exist, which provide a number of properties, such as air permeability index, water absorption rate, water permeability index, chloride diffusivity, electrical resistivity, moisture content and porosity gradient. Most techniques are economical and appropriate for assessing the durability of structures subjected to a single mechanism of deterioration. In reality, structures may face multiple deterioration mechanisms, stress/strains due to both environmental and structural loading and related acceleration of deterioration. Developing an understanding of such multimode deterioration may help in addressing the performance gap between laboratory and field. In this paper, a brief review of some of the ways by which a performance testing strategy could be developed is given so that service life prediction could be more realistic

Identification of Random Amplified Polymorphic DNA (RAPD) Markers in Endemic Yellow Catfish, Horabagrus brachysoma (Gunther 1864)

Random amplified polymorphic DNA (RAPD) analysis was applied to individuals of Horabagrus brachysoma sampled from three geographic locations of Western Ghat river systems in India. Of the thirty-two 10-mer RAPD primers screened initially, ten were chosen and used in a comparative analysis of H. brachysoma collected from Chalakkudy, Meenachil and Nethravathi river systems. A total of 124 RAPD fragments were amplified, out of which 49 (39.51%) were found to be shared by individuals of all three river systems. The remaining 75 fragments were found to be polymorphic (60.48%). This confirms the suitability of RAPD markers for the study of population genetic structure in yellow catfish stocks

Repeatability and Reliability of New Air and Water Permeability Tests for Assessing the Durability of High Performance Concretes

This paper reports on the accuracy of new test methods developed to measure the air and water permeability of high-performance concretes (HPCs). Five representative HPC and one normal concrete (NC) mixtures were tested to estimate both repeatability and reliability of the proposed methods. Repeatability acceptance was adjudged using values of signal-noise ratio (SNR) and discrimination ratio (DR), and reliability was investigated by comparing against standard laboratory-based test methods (i.e., the RILEM gas permeability test and BS EN water penetration test). With SNR and DR values satisfying recommended criteria, it was concluded that test repeatability error has no significant influence on results. In addition, the research confirmed strong positive relationships between the proposed test methods and existing standard permeability assessment techniques. Based on these findings, the proposed test methods show strong potential to become recognized as international methods for determining the permeability of HPCs

Identification of polymorphic allozyme markers for population structure analysis in Horabagrus brachysoma (Gunther, 1864).

Fourteen polymorphic allozyme loci were identified in yellow catfish, Horabagrus brachysoma. The genetic variation detected at each allozyme locus was assessed for samples collected from three rivers. The observed heterozygosities per locus ranged from 0.0286 to 0.4000. Significant genotype heterogeneity indicated that the samples are not drawn from same gene pool. The results suggest the potential of the identified loci to analyze stock structure of natural populations of H. brachysoma

Smoking a dangerous addiction: A systematic review on an underrated risk factor for oral diseases

Despite growing knowledge of the adverse effects of cigarette smoking on general health, smoking is one of the most widely prevalent addictions around the world. Globally, about 1.1 billion smokers and over 8 million people die each year because of cigarette smoking. Smoking acts as a source for a variety of oral and systemic diseases. Various periodontal issues such as increased pocket depth, loss of alveolar bone, tooth mobility, oral lesions, ulcerations, halitosis, and stained teeth are more common among smokers. This systematic review was conducted according to the guidelines from PRISMA, and research articles were retrieved from the Web database sources on 31 May 2021. The quality of research articles was ensured by the type of evidence from combined schema incorporating as schema-13 evidence type description, Cochrane health promotion and public health field (CHPPHF), and the health gains notation framework-14 screening question for quality assessment of qualitative and quantitative studies. Smokers have been found to have bleeding on probing, periodontal pockets, and clinical attachment loss compared to nonsmokers. Oral and respiratory cancers are among the most lethal known diseases caused by cigarette smoking and other commonly occurring sequelae such as stained teeth, periodontal diseases, etc

Developments in Performance Monitoring of Concrete Exposed to Extreme Environments.

The performance of the surface zone of concrete is acknowledged as a major factor governing the rate of deterioration of reinforced concrete structures because it provides the only barrier to the ingress of water containing dissolved ionic species such as chlorides, which ultimately initiate corrosion of the reinforcement. In situ monitoring of cover-zone concrete is therefore critical in attempting to make realistic predictions as to the in-service performance of the structure. To this end, this paper presents developments in a remote interrogation system to allow for continuous, real-time monitoring of the cover-zone concrete from an office setting. Use is made of a multi electrode array embedded within cover-zone concrete to acquire discretized electrical resistivity and temperature measurements, with both parameters monitored spatially and temporally. On-site instrumentation, which allows for the remote interrogation of concrete samples placed at a marine exposure site, is detailed together with data handling and processing procedures. Site measurements highlight the influence of temperature on electrical resistivity and an Arrhenius-based temperature correction protocol is developed using on-site measurements to standardize resistivity data to a reference temperature; this is an advancement over the use of laboratory-based procedures. The testing methodology and interrogation system represent a robust, low-cost, and high-value technique that could be deployed for intelligent monitoring of reinforced concrete structures