Characteristics of Foamed Concrete Containing Ultra-fine Drift Sand of the Yangtze River

The primary goal of this study was to evaluate the use of Ultra-fine Drift Sand from the Yangtze River (China) in place of natural sand in the production of foamed concrete. The experimental design included factors with varying levels: the proportion of Ultra-fine Drift Sand at four levels (0 percent, 30%, 60%, and 100%). Ultra-fine Drift Sand was substituted in proportion to the mass of material. Each factor's effect on compressive strength, density (dry and saturated), air voids, and water absorption was assessed. According to the results, all factors had significant findings. The compressive strength of concrete increased due to an increase in curing time; fly ash content up to 30%; increasing the percent of Yangzi river sand; and decreasing slag. The mixture of 10% SF (Silica Fume), 24% FA (Fly Ash) and 100% YS (Yangzi soil) gives the enhanced results in concrete strength, by which it reaches about 7 MPa compared with other findings. The remaining percentages of mixing benefit compression strength results. This method of treatment provides an economical way through providing a cheap material that enhances the mechanical properties of concrete, provides a light weight concrete, and a good isolator material to improve the building's thermal insulation to reduce ecological problems and save energy. Doi: 10.28991/CEJ-2022-08-08-013 Full Text: PD

Study on Apparent Permeability Model for Gas Transport in Shale Inorganic Nanopores

Inorganic nanopores occurring in the shale matrix have strong hydrophilicity and irreducible water (IW) film can be formed on the inner surface of the pores making gas flow mechanisms in the pores more complex. In this paper, the existence of irreducible water (IW) in inorganic pores is considered, and, based on the Knudsen number (K (Formula presented.)) correction in shale pores, a shale gas apparent permeability model of inorganic nano-pores is established. The effect of the K (Formula presented.) correction on the apparent permeability, the ratio of flow with pore radius and the effect of IW on the apparent permeability are assessed. The main conclusions are as follows: (1) at low pressure (less than 10 MPa) and for medium pore size (pore radius range of 10 nm–60 nm), the effect of the K (Formula presented.) correction should be considered; (2) considering the effect of the K (Formula presented.) correction, bulk phase transport replaces surface diffusion more slowly; considering the existence of IW, bulk phase transport replaces surface diffusion more slowly; (3) with increase in pressure, the IW effect on gas apparent permeability decreases. Under low pressure, the IW, where pore size is small, promotes fluid flow, while the IW in the large pores hinders fluid flow. In conditions of ultra-high pressure, the IW promotes gas flow

Effect of Polypropylene and Basalt Fiber on the Behavior of Mortars for Repair Applications

The fresh, mechanical, and durability properties of the polypropylene fiber-reinforced mortar (PP FRM) and the basalt fiber-reinforced mortar (BFRM) with various fiber contents were tested in this paper. The test results show that the presence of polypropylene (PP) fiber and basalt fiber (BF) in the mortar reduces the initial slump flow and increases the slump flow loss rate. The bond strength and flexural strength of fiber-reinforced mortar (FRM) are improved, whereas no obvious improvement on the compressive strength has been observed. Compared with the control mortar, the bond strength of PP FRM and BFRM reinforced with 0.6 kg/m3, 1.6 kg/m3, and 2.6 kg/m3 fiber increases by 16.60%–28.80% and 10.60%–21.40%, respectively. Furthermore, FRM shows lower drying shrinkage, superior abrasion resistance, water impermeability, and freeze-thaw resistance compared with the control mortar. The abrasion resistance strength of PP FRM and BFRM is 77.30% and 38.65% more than the control mortar with 2.6 kg/m3 fiber content. Therefore, PP FRM and BFRM are suitable to be utilized as repair materials, especially in repairing hydraulic structures surfaces with excellent bond strength and abrasion resistance

High throughput Single-cell Cultivation on Microfluidic Streak Plates

This paper describes the microfluidic streak plate (MSP), a facile method for high-throughput microbial cell separation and cultivation in nanoliter sessile droplets. The MSP method builds upon the conventional streak plate technique by using microfluidic devices to generate nanoliter droplets that can be streaked manually or robotically onto petri dishes prefilled with carrier oil for cultivation of single cells. In addition, chemical gradients could be encoded in the droplet array for comprehensive dose-response analysis. The MSP method was validated by using single-cell isolation of Escherichia coli and antimicrobial susceptibility testing of Pseudomonas aeruginosa PAO1. The robustness of the MSP work flow was demonstrated by cultivating a soil community that degrades polycyclic aromatic hydrocarbons. Cultivation in droplets enabled detection of the richest species diversity with better coverage of rare species. Moreover, isolation and cultivation of bacterial strains by MSP led to the discovery of several species with high degradation efficiency, including four Mycobacterium isolates and a previously unknown fluoranthene-degrading Blastococcus species

Pressure Transient and Rate Decline Analysis for Hydraulic Fractured Vertical Wells with Finite Conductivity in Shale Gas Reservoirs

Producing gas from shale strata has become an increasingly important factor to secure energy over recent years for the considerable volume of natural gas stored. Unlike conventional gas reservoirs, gas transport in shale reservoirs is a complex process. In the organic nano pores, slippage effect, gas diffusion along the wall, viscous flow due to pressure gradient, and desorption from Kerogen coexist; while in the micro fractures, there exist viscous flow and slippage. Hydraulic fracturing is commonly used to enhance the recovery from these ultra-tight gas reservoirs. It is important to clearly understand the effect of known mechanisms on shale gas reservoir performance. This article presents the pressure transient analysis (PTA) and rate decline analysis (RDA) on the hydraulic fractured vertical wells with finite conductivity in shale gas reservoirs considering multiple flow mechanisms including desorption, diffusive flow, Darcy flow and stress sensitivity. The PTA and RDA models were established firstly. Then, the source function, Laplace transform, and the numerical discrete methods were employed to solve the mathematical model. At last the type curves were plotted and different flow regimes were identified. The sensitivity of adsorption coefficient, storage capacity ratio, inter-porosity flow coefficient, fracture conductivity, fracture skin factor, and stress sensitivity were analyzed. This work is important to understand the transient pressure and rate decline behaviors of hydraulic fractured vertical wells with finite conductivity in shale gas reservoirs

Study on Relative Permeability Characteristics Affected by Displacement Pressure Gradient: Experimental Study and Numerical Simulation

The relative permeability is a key parameter for describing multiphase flow in porous media. In this paper, a series of experiments were conducted to study the impact of displacement pressure gradient (DPG) to relative permeability curves using five cores from Shengli Oilfield. Then, an empirical model was proposed to consider the impact of DPG. Finally, the numerical simulation model was established by introducing empirical correction formula into the traditional black oil model, and the effect of DPG on reservoir performance was analyzed. Result shows that with the increase of the DPG (in a range of 0.125-0.498 MPa/m), the residual oil saturation decreases, the cross point of water and oil relative permeability curves moves to the right, and the relative permeability for water phase increases under the same water saturation. In the type III relative permeability curve, with the decrease of DPG, the water relative permeability decrease and the oil relative permeability keeps the same. With considering correction of relative permeability will improve the recovery factor and simulation accuracy

Impact of Parameters\u27 Time Variation on Waterflooding Reservoir Performance

Currently, most oil reservoirs are in high water cut stage due to long term waterflooding, especially for those water-drive naturally fractured formations. Long term waterflooding changes the microscopic pore structure, rock skeleton, and clay minerals of these reservoirs through complex physical and chemical reactions during the process, and causes reservoir and fluid parameters changing over time. Our experimental data show that rock permeability, wettability, and oil viscosity are time-variant parameters during waterflooding, and they are closely related to the continuous water flow through the porous media, which is important to characterize water-drive reservoirs and understand fluid flow in them.In this paper, experimental statistic data from cores of Shengli oilfield, China were utilized. Firstly, the relationship between permeability/wettability/oil viscosity and the ratio of flow-through water volume to pore volume were presented. Secondly, the ratio of grid flow-through water volume to pore volume, denoted as Rwpv, was used to describe the parameter time-variation mechanism. Finally, a numerical simulation software package was developed by introducing Rwpv into the traditional black oil model to characterize the time-variation mechanism in water-drive reservoirs. The new simulator was verified through comparing with commercial reservoir simulator ECLIPSE and experimental data. Simulation results show that the time-variation of permeability and oil viscosity decreases the ultimate recovery compared to the cases without considering time-variation effects; and wettability time-variation makes the reservoir rock more water-wet, which leads to higher ultimate recovery. This research found that both time-variation effects affect the ultimate oil recovery, but in different ways; and time-variation impact becomes increasingly significant as the waterflooding process becomes longer. Both the experimental results and numerical simulations significantly improve the interpretation of the parameters\u27 time variation mechanisms and effect on waterflooding

Utilization of Sandy Soil as the Primary Raw Material in Production of Unfired Bricks

In this study, attempts were made to use sandy soil as the main raw material in making unfired bricks. The sprayed-cured brick specimens were tested for compressive and flexural strength, rate of water absorption, percentage of voids, bulk density, freezing/thawing, and water immersion resistance. In addition, the microstructures of the specimens were also studied using scanning electron microscope (SEM) and X-ray diffraction (XRD) technique. The test results show that unfired brick specimens with the addition of ground-granulated blast-furnace slag (GGBS) tend to achieve better mechanical properties when compared with the specimens that added cement alone, with GGBS correcting particle size distribution and contributing to the pozzolanic reactions and the pore-filling effects. The test specimens with the appropriate addition of cement, GGBS, quicklime, and gypsum are dense and show a low water absorption rate, a low percentage of voids, and an excellent freezing/thawing and water immersion resistance. The SEM observation and XRD analysis verify the formation of hydrate products C–S–H and ettringite, providing a better explanation of the mechanical and physical behavior and durability of the derived unfired bricks. The results obtained suggest that there is a technical approach for the high-efficient comprehensive utilization of sandy soil and provide increased economic and environmental benefits

Influence of polyacrylic ester and silica fume on the mechanical properties of mortar for repair application

Experimental investigations on the influence of different amounts of polyacrylic ester and silica fumes on the mechanical properties of mortar such as the compressive strength, splitting tensile strength, bonding strength, and abrasion resistance are presented in this article. The results show that the compressive and splitting tensile strength of mortar can be improved with the addition of polyacrylic ester and silica fumes. Results obtained from both the direct tensile bond test and flexural bond test indicate that the addition of polyacrylic ester and silica fumes improves the bond strength significantly, and the enhancement is more obvious with polyacrylic ester paste as interfacial adhesives. Furthermore, mortar incorporation of polyacrylic ester and silica fumes shows superior abrasion resistance compared to the control mortar. Therefore, the correct combination of polyacrylic ester and silica fumes to produce mortars has been shown to have synergistic effects, which results in excellent properties including high bond strength and superior abrasion resistance. Mortars containing polyacrylic ester and silica fumes are ideal for repairing concrete especially for hydraulic concrete structure