Research on the Performance of Superhydrophobic Cement-Based Materials Based on Composite Hydrophobic Agents.

The utilization of a novel monolithic superhydrophobic cement material effectively prevents water infiltration and enhances the longevity of the material. A method for improving superhydrophobic concrete was investigated with the aim of increasing its strength and reducing its cost by compounding superhydrophobic substances with water repellents. The experimental tests encompassed the assessment of the compressive strength, contact angle, and water absorption of the superhydrophobic cementitious materials. The findings demonstrate that an increase in the dosage of isobutyltriethoxysilane (IBTES) progressively enhances the contact angle of the specimen, but significantly diminishes its compressive strength. The contact angle of SIKS mirrors that of SIS3, with a superior compressive strength that is 68% higher. Moreover, superhydrophobicity directly influences the water absorption of cementitious materials, with a more pronounced superhydrophobic effect leading to a lower water absorption rate. The water absorption of cementitious materials is influenced by the combined effect of porosity and superhydrophobicity. Furthermore, FT-IR tests unveil functional mappings, such as -CH3 which can reduce the surface energy of materials, signifying successful modification with hydrophobic substances.

Improvement of CO2-Cured Sludge Ceramsite on the Mechanical Performances and Corrosion Resistance of Cement Concrete.

The application of CO2 curing on sludge ceramsite may improve its mechanical properties, and then increase the corresponding corrosion resistance. In this study, the influence of CO2-cured sludge ceramsite on the strength and long-term properties of cement concrete is investigated. CO2 curing time ranges from 0 h to 2 d. The cylinder compressive strength and water absorption rate of CO2-cured sludge ceramsite are first determined. Additionally, the flexural and compressive strengths, the chloride permeability and the freeze-thaw damage, as well as the corresponding thermal conductivity of cement concrete, are tested. Furthermore, the corrosion resistance of reinforcement inner-sludge-ceramsite cement concrete is measured. Finally, the scanning electron microscope photos of sludge ceramsite are obtained. Results show that the cylinder compressive strength of CO2-cured sludge ceramsite is 15.1, ~34.2% higher than that of sludge ceramsite. Meanwhile, the water absorption rate of CO2-cured sludge ceramsite is 39.6, ~82.4% higher than that of sludge ceramsite. The compressive strength and the flexural strength of cement concrete with CO2-cured sludge ceramsite are 11.4 and 18.7, ~21.6% and ~31.5% higher than the cement concrete with sludge ceramsite, respectively. The resistance of NaCl freeze-thaw cycles, determined by comparing the mass loss rate and the loss rates of mechanical strengths, is effectively improved by CO2 curing, while the thermal conductivity of cement concrete is decreased by CO2 curing. The corrosion resistance of inner reinforcement is improved by the application of CO2 curing on sludge ceramsite.

Use of Bacteria to Activate Ground-Granulated Blast-Furnace Slag (GGBFS) as Cementless Binder.

Ground-granulated blast-furnace slag (GGBFS) can be used as a cementless binder after activation. Recent approaches to activate GGBFS have focused on chemical methods that use NaOH, KOH, and CaO. This study introduces the use of bacteria to activate GGBFS as a biological approach. The presence of bacteria (volumetric ratio), curing temperature (23 °C and 60 °C), and number of curing days (3, 7, and 28 d) are investigated. The use of urea is considered owing to the possibility of calcium carbonate formation. The activated GGBFS is evaluated in the form of a cube (5 cm × 5 cm × 5 cm) for its strength, mineral identification, and pore size distribution. A brick (19 cm × 9 cm × 5.7 cm) is prefabricated to see the feasibility of commercializing bacteria-activated GGBFS based on water absorption and strength measurements. All results are compared with those of water-activated GGBFS. The results indicate that the use of urea inhibits the strength improvement of bacteria-activated GGBFS. Bacterial suspension enhances the GGBFS strength at a curing temperature of 60 °C. Mineral identification tests show that the strength increase is primarily due to the formation of calcite. The compressive strength satisfies the commercial standard of concrete bricks; however, the water absorption rate must be resolved.

Crop-dependent changes in water absorption of expanded polystyrene in soil environments.

As expanded polystyrene (EPS) has been utilized in soil environments, there is a need to understand interactions between chemical adsorption and the soil system. We conducted a plant bioassay using agricultural crops in a soil system containing a macro-sized EPS (8.3 ±â€¯0.5 mm). When the EPS was collected after cultivation of no crop (control), mung bean, lettuce, and rice, we found that its water absorption rate significantly (p < 0.05) increased after mung bean and rice cultivation as compared to the no crop condition. We expected that these crop-dependent differences would be highly linked with metal adsorption and desorption. However, cadmium (Cd) adsorption percentages (%) from the initial Cd solution were calculated as 15-18% with no significant differences between the different crop cultivation conditions. The desorption percentages also showed low levels of interaction with the crop-dependent water absorption rate. These results provide useful data for better understanding the interaction between plastics and their roles as chemical vectors in the soil system.

Understanding the microstructure and absorption rate of starch-based superabsorbent polymers prepared under high starch concentration.

From a microstructural view, the focus of this work was on the water absorption rate of starch-based superabsorbent polymers (starch-SAPs) prepared under high starch concentration (0.27:1w/w starch:water). The effects of starch amylose/amylopectin ratio were disclosed. The increase in amylopectin reduced the amount (CPAM) of polyacrylamide (PAM) in starch-SAPs but increased the ratio of starch carbons grafted with PAM, which eventually decreased the average length (LPAM) of PAM chains. The shorter PAM chains could reduce starch-SAP chain flexibility, thus inducing larger mass fractal gels in swollen starch-SAPs. In general, the increases in CPAM and LPAM were preferable for a higher water absorbent capacity (WAC), whereas the denser fractal gels reduced WAC. Interestingly, all starch-SAPs had a dual-phase absorption process with the first stage showing a higher rate than the second phase (k1>k2). The shorter PAM chains caused increases in k1 and k2.

Preliminary Study on Mathematical Model of Liquid Volume Added of TCM Medicinal Broth Decoction Machine / 中国药房

OBJECTIVE:To establish mathematical model of liquid volume added of TCM medicinal broth decoction machine to accurately calculate liquid volume added in the process of medicinal herb decocting,so as to guarantee the quality of medicinal herb decocting. METHODS:The water absorption rate of representative TCM decoction piece with high use frequency were deter-mined,and cluster analysis of water absorption rate of TCM decoction piece was conducted according to closely related index as density,size,shape,moisture. TCM decoction piece with similar water absorption rate were bracketed together,so that of single ingredient TCM decoction piece can be estimated by water absorption of representative TCM decoction piece;the quantity of water evaporation and liquid extrusion were determined among different types of decoction machine (powered by electric and gas);ac-cording to the above parameters,mathematical model of liquid volume of TCM medicinal broth prepared by different types of de-coction machine had been established,and validated with TCM formula. RESULTS:Factors that affected the liquid volume added included the water absorption of each ingredient,the quantity of water evaporation and extrusion function. The mathematical model was liquid volume added=water absorption of each ingredient × quality of decoction piece+the quantity of water evaporation+re-quired amount of liquid-parameters of extrusion function×total weight of decoction piece;in validation test,the percentage of the practical amount of liquid to required amount was within ±5%. CONCLUSIONS:Established model can promote the accuracy li-quid volume added and guarantee the quality of TCM decoction when using TCM decoction machine.