Search Results (7)

Supplementary cementitious materials and aeolian sand have been used to produce low-carbon ultra-high-performance concrete (UHPC) due to their beneficial effects on the reduction in production cost and carbon emissions. However, low-carbon UHPC still faces some drawbacks, such as lowered mechanical properties, large shrinkage, and a tendency for cracking. This study proposed an approach to improve the performance of low-carbon UHPC by incorporating recycled coarse aggregate. The effects of recycled coarse aggregate type, particle size, and content on the workability and mechanical properties of low-carbon UHPC were investigated. Moreover, the internal relative humidity and volume stability of UHPC containing recycled coarse aggregate was also explored. At last, the hydration products and microstructure of UHPC was analyzed to shed light on the underlying mechanisms for the improved performance. Full article

Rotor blades in aero-engines operating in sand-laden environments are highly susceptible to particle-induced erosion. Conventional sand ingestion experiments primarily rely on post-test disassembly, which lacks the capability for real-time surface shape analysis. To overcome this limitation, this study proposes a high-precision three-dimensional (3D) shape measurement method for ultrafast dynamic scenarios, based on pulsed laser illumination and stroboscopic structured light. In the proposed approach, a pulsed laser is employed to illuminate a physical grating, generating stroboscopic structured fringe patterns that are projected onto high-speed rotating blades. The deformed fringe images are synchronously captured by a high-speed camera and processed using Fourier transform profilometry (FTP) to reconstruct fine surface features with high accuracy. Compared with conventional LED-based stroboscopic systems, the pulsed-laser-based scheme effectively suppresses motion blur and significantly improves image intensity under ultra-short exposure conditions. Experimental results demonstrate that stable and high-quality fringe acquisition can be achieved at high rotational speeds. The method enables precise quantification of micro-scale defects, such as scratches and pits, providing a reliable solution for in situ monitoring and performance evaluation in aero-engine sand ingestion tests. Full article

The recycling of ultralight foam concrete (ULFC), both with and without phase-change material (PCM), involves crushing it and using the resulting recycled foam concrete powder (RFCP) as a partial substitute for cement or sand in cement composites. These recycling paths remain insufficiently explored in the literature regarding practical feasibility. Since both RFCP and PCM reduce the flowability of fresh mortars, incorporating RFCP with PCM is, in practice, only feasible with the addition of a superplasticizer (SP). The primary objectives of this study were to determine: (1) the effect of RFCP with PCM, when used to replace cement or sand, on mortar properties, and (2) its influence on the performance of the superplasticizer (SP), to assess the feasibility of using RFCP with PCM in cement composites. The addition of RFCP, both without PCM (RFCP_0) and with PCM (RFCP_PCM), deteriorates the properties of fresh and hardened mortars compared to reference mortars. The negative impact of RFCP is less pronounced when it replaces sand rather than cement. Compared to RFCP_0 mortars, RFCP_PCM mortars exhibit reduced flowability. PCM delays setting and reduces heat evolution during the first 48 h of hardening. PCM does not significantly affect strength or water absorption but increases shrinkage and lowers thermal conductivity. While RFCP_PCM does not impair SP efficiency, PCM causes SP to significantly retard setting and hardening. Full article

We investigated the use of gravel packing sand control technology in multi-lateral horizontal wells to support the development of natural gas hydrate reservoirs. An experimental apparatus was developed to investigate the effects of well configurations and operational parameters on ultra-light sand packing behavior and to estimate the field operational parameters through the application of similarity criteria. The results showed that the ultra-light sand packing process includes four stages in a single horizontal main bore, i.e., sand bank formation, alpha-wave, beta-wave, and simultaneous annulus packing, and two stages in lateral wellbores: a sand bank formation and then an alpha-wave pattern or an initial alpha-wave pattern followed by a slope pattern. At comparable injection rates and sand concentrations, the packing sequence is predominantly governed by leakage rates and the quantity of lateral wellbores. When the lateral wellbore is 1 m and the leakage rate exceeds 20%, the lateral packs first. When the lateral wellbore is 2 m and the leakage rate is below 30%, the main bore packs first. For the field prototype (480 m main bore and 200 m lateral wellbore), the deviation angle of lateral wellbores should be controlled within 30°, and it is recommended that the distance between the junction point and the heel of the horizontal main bore be 160 m. When the leakage rates exceed 50%, the recommended injection rates are less than 1.69 m³/min. When the leakage rates range from 10 to 50%, the recommended injection rates range from 1.69 to 3.38 m³/min, with predicted end-of-packing pressures ranging from 6.56 to 19.92 MPa. This study provides valuable insights into the development of gravel packing sand control technologies in a multi-lateral horizontal well for hydrate reservoirs. Full article

Aerogel is a synthetic porous ultralight material with very low thermal conductivity, and it is mainly used in buildings for external insulation in the form of blankets. In this study, the development of high-strength concrete with a partial replacement of sand with aerogel powder and aerogel beads is presented. Compressive strength, thermal conductivity, and shrinkage measurements have been conducted, and the results indicate that a replacement of sand with 30% aerogel beads leads to a high compressive strength (70 MPa) and relatively low thermal conductivity (1 W/mK) concrete. Full article

The Daniudi gas field is located in the Ordos Basin’s northern section of the Yishan slope. The intertidal–subtidal depositional environment dominates the lithology of the Ma55 sub-member, resulting in a stable, thick-layered dark gray–gray–black limestone and lime dolomite. The stratum is stable laterally as well as dolomite, with an average thickness of 26.8 m. Fractures, dissolution expansion pores, and inter-crystalline dissolved pores are the primary reservoir space kinds, with a minor number of karst caves and fractures generated as well. The main distribution ranges for porosity and permeability are 1–8 percent and 0.01–1 mD, respectively. Low porosity, tightness, and ultra-low permeability are common characteristics, and a single well typically has no natural productivity. Production stimulation technologies like pre-fluid acid fracturing, compound sand addition acid fracturing, and multi-stage injection + temporary plugging volumetric acid fracturing have been gradually optimized using the horizontal well development method, and breakthroughs in the development of tight and low-permeability carbonate rock reservoirs have been made. However, the conditions of different types of reservoirs are quite different, and the acid fracturing process is not matched and imperfect, resulting in large differences in the productivity of different horizontal wells after fracturing, as well as a high proportion of low-yield wells, which cannot meet the needs of cost-effective and effective development of this type of gas reservoir. In light of the aforementioned issues, a series of laboratory tests have been carried out to explore the stimulation effects of acid fracturing on different types of reservoirs and to optimize the acid fracturing process in the Daniudi gas field. The results show that the rock mechanical performances and the acid etching conductivities of the rock specimens are related to the types of reservoirs. The rock mechanical properties can be deteriorated after acidizing, but different types of reservoirs have different degrees of deterioration. According to the results of acid etching conductivity of different types of reservoirs, conductivities obtained by high and low viscosity and cross-link-gelled acid (two stage injection) processes are higher than those of high viscosity systems. The experimental results of process suitability suggest adopting high and low viscidity acid systems for pore type and fracture-dissolved pore type reservoirs, and cross-linked acid systems for fracture-pore type reservoirs. The findings of this study can help form a better understanding of the performance of different types of reservoirs under the various acidified conditions that can be used for the optimization of acid fracturing processes in carbonate formations. Full article

Limited water resources in arid and semi-arid regions require innovative management to maintain crop production while minimizing the amounts of water used for irrigation. We investigated the impact of the particle size of natural clinoptilolite zeolite (CZ) on water content (WC) and hydraulic properties of a loamy sand soil. WC was measured using 5TE sensors installed at five depths (10, 20, 30, 40, and 50 cm) in soil columns (7.4 cm ID, 56 cm length). Three sizes of macro- and nano-CZ particles (20, 2.0, and 0.2 µm) were added to the soil at an application rate of 1%. The columns were subject to 14 wetting/drying cycles from 24 February to 8 December 2020. The HYDRUS-1D model was used to simulate WC and soil water storage inside the soil columns. WC increased with the decreasing particle size of CZ, especially when columns were subject to long drying periods. The larger surface area and smaller pore size of CZ altered the pore-size distribution of the loamy sand soil and increased the amount of microporosity inside the soil system, leading to increased water retention. Available water and soil water storage were increased by 3.6–14.7% and 6.8–10.5%, respectively, with larger increases with the decrease in CZ particle size. Variations in infiltration rate and hydraulic conductivity were statistically significant only with the smallest CZ particle size, with a reduction of 25.6% and 19.3% compared to the control, respectively. The HYDRUS-1D model accurately simulated WC and soil water storage, with only slight overestimation of WC (2.4%) at depths ≤ 30 cm. The results suggest that, in light-textured soils, the application of CZ in the ultra-fine nanoparticle size would increase water-holding capacity and reduce hydraulic conductivity, which would enhance the efficiency of water use and contribute to water conservation in dry regions. Full article