Real-time monitoring the electrical properties of pastes to map the hydration induced microstructure change in cement-based materials

The effect of the supplementary materials (SCMs) on the moisture content and ion diffusivity at different hydration time is important for the service life modelling of modern concrete. This study designed a simple but valid method to monitor the microstructure change in pastes during hydration. A procedure easy to implement was proposed to detect the water content in pastes. The electrical conductivity of pore solution was evaluated by the evaporable water content in pastes and chemical composition in the binders. Results show that the electrical properties of pastes (conductivity, formation factor and its growth rate) can effectively indicate the hydration reactivity of binder, pore connectivity and volume of pore solution in the hardened pastes. The effect of waterbinder ratio and SCMs on the structure of pastes are effectively indexed by the formation factor which is the conductivity of pore solution divided by that of paste. The inflection point of average growth rate of formation factor is a good index for the final setting of pastes. The relation between volume of evaporable water and formation factor is well demonstrated by the extended percolation theory. The real-time monitored electrical conductivity and formation factor of pastes can be used to calculate the chloride migration coefficient in hardened cement pastes

Moisture and ion transport properties in blended pastes and their relation to the refined pore structure

This paper presents a study of the\ua0moisture transport\ua0properties in blended pastes measured by a new procedure and setup. The dependence of moisture transport coefficient on relative humidity (RH) is confirmed. The differences in the moisture dependency may be due to discrepancies in the critical RH for the\ua0percolation\ua0of liquid. Fly ash and slag increase the percentage of mesopores or “ink-bottle” pores with a\ua0mesoscale\ua0neck and they strongly reduce the pore connectivity in pastes. These effects cause the evident reduction in the moisture and chloride diffusivity. The additional replacement with\ua0limestone filler\ua0has little effect on the pore connectivity. The formation factor controls the moisture transport at the high RH interval, but the volume of small pores (middle capillary and mesopores) is the major determinant at a low RH interval. The relationship between water-binder ratio,\ua0pore structure\ua0and moisture transport or chloride migration coefficient is discussed

On the growth of national geoparks in China: distribution, interpretation, and regional comparison

Since the year 2000 China has created 139 National Geoparks; it started under the guidance of the former UNESCO\u27s Division of Earth Science, and has therefore become one of the pioneers in this aspect. Many National Geoparks in China have been described over the past decade, but an understanding of the range of various landform features and their connection with geological and climatic constraints has not previously been published. Based on an increasing awareness of National Geoparks, the aim of this contribution is to provide a comprehensive overview of the National Geoparks of China by reviewing the geological heritage and their intrinsic linkages with geological and climatic controls. A regional comparison of the widespread clastic and karst Geopark landforms indicates that the development of these terrains can only be understood within a synthesis of tectonic constraints, climatic changes and lithological properties, whereas the variety of types, forms, scales and development patterns reflect processes in various climatic settings

Using water vapour and N2 isotherms to unveil effects of SCMs on nanopores and evaluate hydration degree

Nanopores are critical for the durability of cement-based materials, but the refinement of these pores by SCMs is yet to have a clear understanding. This paper studied effects of the water–binder ratio, SCMs and the drying on the distribution of nanopores using water vapour and N2\ua0sorption isotherms. Results show that data of water vapour sorption can be used for a practical evaluation of the hydration degree of SCMs with thermodynamic simulation. Fly ash increases the volume of large gel and capillary pores. It lowers the difference between the sorption of water vapour and N2. Slag evidently refines the nanopores by increasing the volume of ink-bottle gel pores with an interlayer-size neck. A higher\ua0w/b\ua0produces more large pores to reduce the effect of drying. Removal of water induces contraction of interlayer and reduces gel pores volume, which causes large difference between sorption of water vapour and N2

In Vivo Imaging of Schistosomes to Assess Disease Burden Using Positron Emission Tomography (PET)

Schistosomiasis is a well studied parasitic disease that is far from eradication despite the development of an effective treatment. The lack of an efficacious vaccine and high re-infection rates after treatment are major factors in its intractable worldwide prevalence. A non-invasive imaging technique like positron emission tomography (PET) could give clinicians and researchers a quantitative and visual tool to characterize the worm burden in infected individuals, determine the efficacy of a candidate vaccine, and provide information about parasite migration patterns and basic biology. We are therefore proposing the novel application of PET imaging to schistosomiasis in order to advance the management and research of this infectious disease. Herein, we demonstrate that schistosome parasites take up 2-deoxy-2[18F]fluoro-D-glucose (FDG). FDG uptake in regions adjacent to or within the liver linearly correlate with the worm number in infected mice, but the correlation was stronger in mice with high infection burdens. We anticipate that this research is a first step in the development of more specific radiotracers optimized for schistosomiasis, and will eventually translate to human studies

Three-dimensional modeling of nitrate-N transport in vadose zone: Roles of soil heterogeneity and groundwater flux

Contamination of groundwater from nitrogen fertilizers in agricultural lands is an important environmental and water quality management issue. It is well recognized that in agriculturally intensive areas, fertilizers and pesticides may leach through the vadose zone and eventually reach groundwater. While numerical models are commonly used to simulate fate and transport of agricultural contaminants, few models have considered a controlled field work to investigate the influence of soil heterogeneity and groundwater flow on nitrate-N distribution in both root zone and deep vadose zone. In this work, a numerical model was developed to simulate nitrate-N transport and transformation beneath a center pivot-irrigated corn field on Nebraska Management System Evaluation area over a three-year period. The model was based on a realistic three-dimensional sediment lithology, as well as carefully controlled irrigation and fertilizer application plans. In parallel, a homogeneous soil domain, containing the major sediment type of the site (i.e. sandy loam), was developed to conduct the same water flow and nitrate-N leaching simulations. Simulated nitrate-N concentrations were compared with the monitored nitrate-N concentrations in 10 multilevel sampling wells over a three-year period. Although soil heterogeneity was mainly observed from top soil to 3m below the surface, heterogeneity controlled the spatial distribution of nitrate-N concentration. Soil heterogeneity, however, has minimal impact on the total mass of nitrate-N in the domain. In the deeper saturated zone, short-term variations of nitrate-N concentration correlated with the groundwater level fluctuations

Wild relatives of pigeonpea in China

Wild relatives play an important role in the genetic improvement of cultivated crops. Breeders turn their attention to the wild relatives of crops after unsuccessful search for some unique trait in the cultivated germplasm. According to van der Maesen (1986) the genus Cajanus has 32 species. Of these, the Indian subcontinent harbors 18 species. ICRISAT has the global responsibility of collection, maintenance, and evaluation of germplasm of the wild relatives of pigeonpea. At present a total of 213 accessions, representing 20 Cajanus species are conserved for use in the breeding programs

Performance of ICRISAT pigeonpeas in China

Results of the experiments on pigeon pea biomass production conducted in Guangxi Province, and on soil conservation potential of pigeon pea conducted in Kunming, China, are presented and discussed. Tabulated data on the performance of short-duration determinate ICRISAT pigeon pea lines tested in Guangzhou, China, during 1998 is given

Pigeonpea: A potential fodder crop for Guangxi province of China

The progress of pigeon pea as a major fodder crop in Guangxi, China is reviewed. The potential of pigeon pea as a source of good quality fodder for the growing livestock industry in the province is discussed