Role of Chemical and Mineral Admixtures on the Physical Properties and Frost-Resistance of Recycled Aggre-gate Concrete

10.14359/398 ◽  
1998 ◽  
Vol 95 (5) ◽  
2021 ◽  
Vol 61 (4) ◽  
pp. 1220-1231
Author(s):  
Pragya Gupta ◽  
Akanksha Pandey ◽  
Kirtiraj K. Gaikwad ◽  
Sunanda Roy ◽  
Pradip K. Maji

2021 ◽  
Author(s):  
Zhenyu Zhang ◽  
Patrick Laux ◽  
Joël Arnault ◽  
Jianhui Wei ◽  
Jussi Baade ◽  
...  

<p>Land degradation with its direct impact on vegetation, surface soil layers and land surface albedo, has great relevance with the climate system. Assessing the climatic and ecological effects induced by land degradation requires a precise understanding of the interaction between the land surface and atmosphere. In coupled land-atmosphere modeling, the low boundary conditions impact the thermal and hydraulic exchanges at the land surface, therefore regulates the overlying atmosphere by land-atmosphere feedback processes. However, those land-atmosphere interactions are not convincingly represented in coupled land-atmosphere modeling applications. It is partly due to an approximate representation of hydrological processes in land surface modeling. Another source of uncertainties relates to the generalization of soil physical properties in the modeling system. This study focuses on the role of the prescribed physical properties of soil in high-resolution land surface-atmosphere simulations over South Africa. The model used here is the hydrologically-enhanced Weather Research and Forecasting (WRF-Hydro) model. Four commonly used global soil datasets obtained from UN Food and Agriculture Organization (FAO) soil database, Harmonized World Soil Database (HWSD), Global Soil Dataset for Earth System Model (GSDE), and SoilGrids dataset, are incorporated within the WRF-Hydro experiments for investigating the impact of soil information on land-atmosphere interactions. The simulation results of near-surface temperature, skin temperature, and surface energy fluxes are presented and compared to observational-based reference dataset. It is found that simulated soil moisture is largely influenced by soil texture features, which affects its feedback to the atmosphere.</p>


1985 ◽  
Vol 69 (1-2) ◽  
pp. 69-91 ◽  
Author(s):  
Dae-Choul Kim ◽  
Murli H Manghnani ◽  
Seymour O Schlanger

2016 ◽  
Vol 7 (5) ◽  
pp. 546-550
Author(s):  
Aurelijus Daugėla ◽  
Džigita Nagrockienė ◽  
Laurynas Zarauskas

Cement as the binding agent in the production of concrete can be replaced with active mineral admixtures. Biofuel combustion fly ash is one of such admixtures. Materials used for the study: Portland cement CEM I 42.5 R, sand of 0/4 fraction, gravel of 4/16 fraction, biofuel fly ash, superplasticizer, water. Six compositions of concrete were designed by replacing 0%, 5%, 10%, 15% 20%, and 25% of cement with biofuel fly ash. The article analyses the effect of biofuel fly ash content on the properties of concrete. The tests revealed that the increase of biofuel fly ash content up to 20% increases concrete density and compressive strength after 7 and 28 days of curing and decreases water absorption, with corrected water content by using plasticizing admixture. It was found that concrete where 20% of cement is replaced by biofuel ash has higher frost resistance.


Author(s):  
Jing Cui ◽  
Andreas D. Peuke ◽  
Anis Limami ◽  
Guillaume Tcherkez

Since the first description of phloem sap composition nearly 60 years ago, it is generally assumed that phloem sap does not contain nitrate and that there is little or no backflow of nitrate from shoots to roots. While it is true that nitrate can occasionally be absent from phloem sap, there is now substantial evidence that phloem can carry nitrate and furthermore, transporters involved in nitrate redistribution to shoot sink organs and roots have been found. This raises the question of why nitrate may or may not be present in phloem sap, why its concentration is generally kept low, and whether plant shoot-root nutrient cycling also involves nitrate. We propose here that phloem sap nitrate is not only an essential component of plant nutritional signaling but also contributes to physical properties of phloem sap and as such, its concentration is controlled to ensure proper coordination of plant development and nutrient transport.


1981 ◽  
Vol 29 (6) ◽  
pp. 675 ◽  
Author(s):  
DM Paton

The effects of different hardening regimes were studied in E. viminalis by varying temperature, light conditions and photoperiod. The role of root temperature in dehardening was investigated in E. grandis. The relationship between leaf glaucousness and frost resistance was reexamined in E. urnigera and in crosses between the glaucous frost-resistant species E. pulverulenta and the green. less-resistant species E. grandis. These studies involved seedlings but adult material was also used when checking the association between frost resistance and G, the growth regulator in E. grandis. Provided that night temperatures were close to freezing, rapid hardening was independent of photoperiod, light source and day/night temperature differentials. No significant relationship between level of frost resistance and intensity of leaf glaucousness was observed in a segregating progeny of E. urnigera. In F2 and backcross progenies between E. pulverulenta and E. grandis, no evidence was obtained for either physiological or genetical links between glaucousness and frost resistance. As in several other Eucalyptus species, low root temperatures delayed rapid dehardening in E. grandis. Increased frost resistance towards the top of E. grandis seedlings was associated with marked ontogenetic increases in G content. The G content of a 2 m sapling was highest in winter when maximum frost resistance had developed. This and other supporting evidence suggests that G has a role in the frost resistance of E. Grandis perhaps by affecting active electron transport properties of membranes. No information of this kind is available for other Eucalyptus species.


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