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ABSTRACT A new artificial reef concrete (NARC) with sulphoaluminate cement, marine sand and sea water et al. was proposed. The effect of cement type, sand type and water type on [...]

This paper aims to investigate the effects of rice husk ash (RHA) on itself activity and its concrete performance at different preparation temperatures for which three temperatures of 650 °C, 800 °C, and 900 °C were considered. To find a reasonable particle size, the effect of the particle size of the RHA on the workability of concrete at various grinding times was studied. A series of experiments were carried out to study the characteristics of the RHA, including X-ray fluorescence, XRD, ESEM, and an activity test. The carbonation resistance and frost resistance of concrete incorporating RHA were also investigated, where 10 and 30 wt.-% of cement was considered. The results show that the surface area of the RHA first increases and then decreases with grinding time. When the RHA is ground for 30 min, its surface area is largest and the workability of its mixture is also best. The burning temperature has little effect on the amount of SiO2. Although the structure and activity of SiO2in RHA change at different burning temperatures, the performance of concrete incorporating RHA is higher than that of control concrete without RHA. With the same content of RHA, both carbonization resistance and frost resistance decrease with an increasing burning temperature of RHA. At the same burning temperature, both carbonization resistance and frost resistance increase with an increasing amount of RHA. Among all types of mixtures, the mixture incorporating 30 % RHA burned at 650 °C (i. e., RHA650) yields the best performance.

The impermeability of recycled fine aggregate concrete (RFAC) with different contents of recycled fine aggregate (RFA) was tested according to the standard test method of ASTM C1202. The moisture states of RFA were controlled at air-dried (AD), oven-dried (OD) and saturated surface-dried (SSD) states. Both the interfacial structure and the pore structure of RFAC were analyzed. Research results show that, for the same total water-cement (TWC) ratio and the same content of RFA, the interfacial transition region of RFAC became denser by increasing the moisture amount of RFA from oven-dried, air-dried to a saturated surface-dried state; meanwhile, the density and porosity of hardened cement paste (HCP) improved as well, which resulted in the higher impermeability of RFAC. Whereas by contrast, for the same moisture state and by increasing the RFA content, both the interfacial transition region and the property of the interface structure of RFAC became weaker. Also, the decreasing density and porosity of HCP resulted in lower impermeability of RFAC.

The influence of the concentration of sodium hydroxide solution on the tensile bond strength of alkali-activated slags (AAS) used as a tunnel fireproof coating material was studied under the simulated combined action of vibration and wind suction. A test method involving the simultaneous application of vibration and suction was developed and utilized. The test results indicate that as the concentration of sodium hydroxide solution in the AAS increases from 1 to 10 weight percentage, the bond strength of AAS coating improves under the coupling action of vibration and suction. Furthermore, the cumulative pore volume and the average pore diameter in the AAS are reduced and the ratio of harmful pores to total pores decreases. As the concentration of sodium hydroxide solution increases more than 10 weight percentage, however, there is no further benefit in terms of the pore structure and bond strength.

Granite stone powder is a common type of stone-product industrial waste spreading over Fujian Province and other areas of China, causing serious environmental problems. This paper investigates the possibility of using granite stone powder to completely or partially replace quartz powder for preparing “Green” or “Eco” ultra-high performance concrete under autoclave curing regimes. The mechanical properties and microstructure of autoclaved ultra-high-performance concrete (UHPC) mixed with different replacement ratios of granite stone powders were tested. It was found that its mechanical properties still satisfied the original requirements even after total replacement of quartz powders by granite stone powders. Despite of a slight decrease in flowability after total replacement, flexural and compressive strength did not change significantly. The hydration product of flaky tobermorite crystal was found in both granite stone powder blended UHPC and in quartz powder blended UHPC, while the Ca/Si ratio varied slightly. Furthermore, the pore structure of unadulterated UHPC improved due to a larger population of harmless and less-harmful pores after quartz powder were replaced by granite stone powder.

This study aims to characterize the seasonal variation of the shallow‐to‐deep convection transition and understand how environmental conditions impact the behavior of this transition using data collected from the Observations and Modeling of the Green Ocean Amazon (GOAmazon) field campaign in the Central Amazon (Manaus). The diurnal cycle of the rain/cloud fraction shows that the wet season has more extensive shallow convection before the transition to deep convection with larger fractional coverage and rainfall; deep convection in the transition season is more intense and has higher vertical extension and a stronger updraft. Surface meteorology, atmospheric moisture, instability, and wind shear are contrasted for the shallow/congestus convection (SC) cases and the locally formed shallow‐to‐deep convection transition (LD) cases. The comparisons suggest that occurrence of the LD is generally promoted under the conditions of high atmospheric moisture and instability but has a weaker dependence on wind shear. The relative importance of these environmental controls also varies in different seasons: The dry and transition seasons require a deeper moist layer from the boundary layer to midtroposphere than the wet season; convective available potential energy (CAPE) is higher during the transition season, but it is a less important factor for shallow‐to‐deep convection transition than in other seasons; LD only has significantly larger wind shears than SC during the dry season. Shallow‐to‐deep convection transition and diurnal cycle of rainfall in the Central Amazon vary seasonallyThe transition of shallow‐to‐deep convection require a deeper moist layer during the dry and transition seasons than during the wet seasonConvective intensity is the strongest during the transition season due to high CAPE and CIN

We have developed a canonical correlation analysis (CCA) model for improving seasonal winter rainfall prediction. It uses the anomalies of sea surface temperature (SST), vertically integrated vapor transport (IVT), and geopotential height at 250 hPa (Z250) in October and November, respectively, as the predictors for winter rainfall prediction. These predictors represent the processes that influence winter rainfall over California as documented in the literature, but their potential for improving predictability was previously unclear. This statistical model shows prediction skills higher than those of the baseline autoregressive model, the CCA‐based prediction model using only the SST anomalies, and the dynamic predictions by the North American Multi‐Model Ensemble (NMME). Averaged over California, the Pearson correlation (R) is 0.64, root mean squared error (RMSE) is 0.65, and Heidke skill score (HSS) is 0.42 when the CCA‐based model is initialized by the three predictor fields (SST, IVT, and Z250) in November. These skills are higher than those of the NMME predictions initialized in November (R, RMSE, and HSS are 0.30, 0.83, and 0.15, respectively) and those of the autoregressive baseline (R, RMSE, and HSS are 0.10, 0.79, and 0.08, respectively). Hindcasts of winter rainfall initialized by October observations show R, RMSE, and HSS of 0.53, 0.81, and 0.39, respectively, also higher than those of the NMME seasonal prediction initialized in October (0.32, 0.79, and 0.22 for R, RMSE, and HSS, respectively) and the autoregressive model (0.30, 0.75, and 0.16 for R, RMSE, and HSS, respectively). Statistical model for California winter rainfall forecast is developed which is better than autoregressive model and current dynamic modelsIncorporating atmospheric variables into the model is essential for a high skill at a shorter lead time, especially moisture transport Statistical model for California winter rainfall forecast is developed which is better than autoregressive model and current dynamic models Incorporating atmospheric variables into the model is essential for a high skill at a shorter lead time, especially moisture transport

This study uses a multivariate self‐organizing map approach to diagnose precipitation anomalies over the United States' Great Plains during the warm season (April–August) and the associated anomalous large‐scale atmospheric patterns, as represented by standardized anomalies of 500 hPa geopotential (Z500′), integrated vapor transport (IVT′), and convective inhibition index (CINi′). Circulation patterns favoring dryness identified by the method are generally consistent with those shown in previous studies, but this study provides a more comprehensive and probabilistic characterization of those that favor drought over the Southern Great Plains (SGP) and the Central Great Plains (CGP) and their temporal evolutions. Six circulation types that are associated with warm season rainfall variability over the Great Plains are identified. The SGP droughts are attributable to more frequent and persistent northern low‐southern high as well as dominant high circulation types and are connected to larger negative CINi′. In contrast, CGP droughts are attributable to more frequent and persistent western low‐eastern high, or northern high‐southern low, or dominant high patterns, and are linked to a larger negative IVT′, but not larger CINi′. Thus, these results suggest that land surface dryness and a stable atmospheric boundary layer may play a more important role over the SGP than reduced moisture transport in warm season droughts, but reduced moisture transport may play a more important role than thermodynamic stability in droughts over the CGP. Multivariate self‐organizing map reveals six circulation types related to warm season rainfall variability over the U.S. Great PlainsSGP drought is linked to higher geopotentials either over the entire or southern Great Plains with strong negative convective inhibition energyCGP drought is attributable to higher geopotentials either over the entire, or northern, or western Great Plains and weak moisture transport