Solidification effect of river bottom sediments after flocculation via different composite flocculants.

The main problem in the reduction of river bottom sediments is to solve the dewatering of the rive sediments. The reduction of river bottom sediments is usually dehydrated by natural air drying and requires more time and economic costs. Different proportions of composite flocculants and curing agents have been developed to the reduction of river bottom sediments according to the requirements of the project. Two or more flocculants were mixed with the rive sediments. Therefore, anionic polyacrylamide (PAM), polyaluminum chloride (PAC), polysilicate aluminum ferric (PSAF), and iron perchloride (IC) were selected for flocculation of river sediments. Through the sedimentation column test, the relationship between sedimentation amount and time was plotted, the turbidity value and pH value of the supernatant filtration supernatant were detected, and the flocculation effect of different flocculants was evaluated to obtain suitable groups of composite flocculants. The optimum ratio of two types of polyacrylamide with a molecular weight of 18 million and 23 million was 3:7. The turbidity of the supernatant of water could well be reduced by adding polysilicate aluminum ferric. Finally, the 6 groups of composite flocculants were determined according to the sedimentation and the turbidity value of the supernatant. The relative water content was maintained at about 60% before and after flocculation. At the same curing age, the compressive strength increased as the amount of curing agent increased after flocculation. At the same curing agent dosage, the overall solidification effect was reduced with increase of curing time after flocculation.

Analysis of the Thermal Performance of the Embedded Composite Phase Change Energy Storage Wall.

In this study, the phase change paraffin and metal powder were mixed to form the composite phase change energy-storing material. This composite material was then injected into metal coil tubings at different coil spacings to form a composite phase change energy storage tubing system, which was then embedded in a wall. The thermal performance of the embedded phase change energy storage wall was investigated at various temperatures. The results showed that among the four types of aforementioned walls, the energy storage tubes at a spacing of 20 mm exhibited the smallest heat transfer and the largest surface heat storage coefficients. Therefore, this wall can block heat flow and temperature propagation effectively, and it exhibits excellent thermal insulating and heat storage performances and increased resistance to temperature fluctuations.

Flocculation-bio-treatment of heavy metals-vacuum preloading of the river sediments.

Heavy metals pollution in river sediments is irreversible, and it is not easy to be found to be concealed. The pollution of heavy metals for river sediments is currently a serious environmental problem. In the paper, the Bacillus subtilis was selected to remove heavy metals by bio-mineralization method in river sediments. Optimal content of Bacillus subtilis powder and organophosphate monoester was 20 g and 0.2 mol in 1 L of bacterial solution, respectively. The optimum reaction time and temperature were 36 h and 30 °C, respectively. The optimal reaction conditions were applied to zinc ions in river sediments. After heavy metals treatment, there was little effect on the water content before and after flocculation and vacuum preloading. Treatment of heavy metals had no effect on the cross-plate shear strength of river sediments after vacuum preloading. After treatment of heavy metals, the effect of purifying water quality was the group B(Polyacrylamide + Polysilicate aluminium ferric) bigger than the group A (Polyacrylamide). The removal efficiency of zinc ions (Zn2+) in the group B was 89.59% and 74.99% before and after the vacuum preloading, respectively, which was better than that in the group A.

Performance of river sediments after flocculation-pressure filter membrane-vacuum preloading.

The main problem in the reduction of river bottom sediments is to solve the dewatering of the sludge. The commonly used natural air drying method requires a large amount of time and economic cost. In this paper, different treatments were developed for the needs of the project, and related tests were carried out on the reduction of the sludge. Firstly, two or more flocculants were compounded according to the nature of the sludge. The 6 different treatments were determined according to the sedimentation and the turbidity value of the supernatant. Secondly, the dewatering test was carried out on river sediments after flocculation-vacuum preloading. The dewatering effect of different flocculants, water quality, dissipation of pore water pressure, vane shear strength, compression coefficient, and coefficient of consolidation have been analyzed after flocculation-vacuum preloading. The polysilicate aluminium ferric (PSAF) can greatly increase the dewatering efficiency of the filter press membrane, and the final dewatering amount could reach 310 g. The effect of purifying water quality was PSAF>PAM (polyacrylamide, PAM-1(18 million): PAM-2(23 million) = 3:7)>PAC (polyaluminium chloride). The PSAF and PAC could increase the pH of the water during the vacuum preloading test. The PAM has the best the vane shear strength. Lime could improve the vacuum preloading and the vane shear strength when it was added to other flocculants. The incorporation of PSAF could accelerate the dissipation and increase the final dissipation value of pores water pressure. Compared with PAM+PAC+lime, PAM+lime, PAM+PSAF+lime, PAM+PSAF, and PAM+PAC, the overall effect and price of the PAM is optimal.

Strength, microstructure, and thermal conductivity of the insulation wallboards prepared with rice husk fiber and recycled concrete aggregates.

This paper intends to evaluate the influence of content of rice husk fiber and cementitious materials on mechanical properties and thermal conductivity of thermal insulation wallboards. Thermal insulation wallboard contained different mass of rice husk fiber was prepared when the weight of cement, fly ash, cellulose ether, naphthalene superplasticizer, and recycled concrete aggregates was equal. Scanning electron microscopy (SEM) shows the internal structure of the insulation wallboards is very dense. Compared to thermal conductivity of blank group (0.9600 W/m·°C), B2 (0.1997 W/m·°C) and C2 (0.1810 W/m·°C) measured by the DRCD-3030 intelligent thermal conductivity tester can meet certain engineering requirements. Average compressive strength, flexural strength, and thermal conductivity of wallboards decreases with content of rice husk fiber increasing when other materials mass are the same. Under the same conditions of curing time and rice husk content, average compressive and flexural strength increase with the increase of the amount of cementitious material.