Factors influencing accuracy of free swelling ratio of expansive soil

Many geotechnical structures,such as the subgrade of high-speed railway,are extremely sensitive to micro deformations.As one of the most commonly used indexes in China to evaluate the potential swelling level of expansive soils,the effectiveness and accuracy of free swelling ratio should be highly required.However,due to the deficiency of geotechnical test regulations for the free swelling ratio test,non-negligible variation difference is often observed among the test results of the same type of soil samples.Thus,a series of laboratory tests are conducted to figure out the influences of soil particle size,initial soil temperature,and wet-dry circulation on the free swelling ratio of expansive soils.The results show that the initial soil temperature exerts an obvious influence on free swelling ratio and a relative weak influence on soil mass of expansive soil with the micro soil particle size(d<0.075 mm),and the correlation becomes unclear when soil particle size is within the range of 0.075 mm≤d<0.500 mm.A larger particle size of expansive soils induces a larger free swelling ratio and soil mass in the soil measuring cup regardless of initial soil temperature.However,the enlarging amplitude decreases as the particle size of expansive soils increases.There is a progressive enlargement of free swelling ratio at the first two wet-dry cycles and then it attenuates gradually when the number of wetdry cycles further increases.

Preparation and Swelling Behavior of L-Lactide Interpenetrating Networks

Novel triblock copolymers of poly (L-lactide)-poly (ethylene glycol)-sebacate-poly (ethylene glycol)-poly (L-lactide) were synthesized by Ring-Opening Polymerization of different ratios of L-lactide with other three pre-prepared poly (ethylene glycol)-sebacate-poly (ethylene glycol) polymers, coded A, B and C which had different poly (ethyleneglycol) chain lengths. The copolymers were characterized by FTIR and 1H NMR spectroscopy, which indicated that the reaction of ROP took place and led to producing nine triblock copolymers having new different lactide chain lengths (n = 10, 25 and 50), AL10, AL25, AL50,BL10, BL25, BL50, CL10, CL25, and CL50. Nine polymer networks were also prepared from copolymers with sodium alginate S1 - S9 and finally mixed with a solution of hydroxyl ethyl cellulose to form SH1 - SH9.

Swelling Properties of Water-Swelling Materials Exposed to Organic Water Pollution

A water-swelling material is one of the rubbery impermeable materials which mixed synthetic resin elastomers as a base material, high absorbency polymers, filler and solvents. In this study, swelling characteristics of the water-swelling material on the water polluted with COD and BOD, as an impermeable material at coastal landfill sites, are examined by laboratory swelling ratio test. Furthermore, the factor in which it influences the swelling pressure of water-swelling material is clarified by measuring the swelling pressure. As the results, the COD nor the BOD concentrations in the soaked water influence the swelling ratio of the water-swelling material. When the thicknesses of water-swelling material are 2 mm and 3 mm, the maximum swelling pressure of 0.5 MPa or more that corresponds to hydraulic pressure by depth of 50 m is possessed.

Study and application on fire extinguishing and preventing with light-paste material for coalmine

For preventing and extinguishing the spontaneous combustion of coal seam, based on the importance for sealing air leakage channels in roadway, developed a material of light-paste for coalmine, and research its ingredient, proportion and performance. The result indicates that the component ratio of the material is which PB exciting agent is 20%, complex reinforcing agent is 2%, complex expansion agent is 1%, and A-material is 77%. The performances of compressive strength, swelling ratio and expansion time are optimum. The light-paste material can effectively seal air leakage channels for preventing and extinguishing the spontaneous combustion of coal seam in coalmine.

Research on physical and chemical properties and soundness of dry desulphurized fly ash used as a construction material

The physical and chemical properties and soundness of Baosteel Power Plant＇ s dry desulphurized fly ash were systematically investigated and compared with those of the similar byproducts produced by some other domestic power plants. The feasibility of these byproducts used as a construction material was also analyzed. The results show that Baosteel＇s dry desulphurized fly ash is a kind of ash with high calcium and high sulfur contents, which has the characteristics of volcanic ash activity. It contains sulfate and sulfite, and is easy to cause sulfate activation. It has higher activity compared with common fly ash. But higher calcium sulfite and free-CaO contents in ash will bring about soundness concerns to users. Therefore, quality tests and volume control will be necessary when fly ash is used as a construction material.

The Influence of Various Cationic Group on Polynorbornene Based Anion Exchange Membranes with Hydrophobic Large Steric Hindrance Arylene Substituent

A series of brominated polynorbornene derivatives,including bulky steric hydrophobic groups and highly physical and chemical stable backbones,were synthesized via ring-opening metathesis polymerization and post-functionalized with trimethylammonium(QA),N-methylimidazole(Im),N-methylpyrrolidinium(Pyr)or N-methylpiperidinium(Pip)to construct the entire anion exchange membranes(AEMs).Benefited from prominent phase-separated morphology,PBO-x%-y(x=66,68,70;y=QA,Im,Pyr,Pip)AEMs with ion exchange capacity(IEC)approaching 2.0 meq·g^(−1)exhibited super high hydroxide conductivities.Thereinto,PBO-70%-Pip possessed the highest hydroxide conductivity of 137.3 mS·cm^(−1)at 80℃Moreover,all membranes exhibit low swelling ratio(SR)(the SR of PBO-66%-QA was just 8.6%at 80℃).That is,bulky steric hydrophobic groups play a crucial role in balancing the high hydroxide conductivity and low SR in AEMs.Furthermore,three AEMs(PBO-66%-QA,PBO-68%-Pyr,PBO-70%-Pip)showed good alkaline stability after immersion into 1.0 mol/L NaOH aqueous solution at 80℃for 480 h without any degradation.

Synthesis of Hydrophobically Modified Poly(acrylic acid) Gels and Interaction of the Gels with Cationic/Anionic Surfactants

Poly(acrylic acid) (PAA) gel network with only chemical crosslinking and hydrophobically modified PAA (HM-PAA) gels with both chemical and physical crosslinking were synthesized by radical polymerization in tert-butanol, using ethylene glycol dimethacrylate (EGDMA) as crosslinker, and 2-(N-ethylperfluorooctanesulfoamido)ethyl methacrylate (FMA), stearyl acrylate (SA) or lauryl acrylate (LA) as hydrophobic comonomer respectively. The effect of the fractions and the species of the hydrophobes on swelling properties of HM-PAA gels and the interaction of gels and surfactants were studied. The results showed that the swelling ratio of HM-PAA gels exhibited a sharp decrease with increasing hydrophobic comonomer concentration, which could be ascribed to the formation of strong hydrophobic association among hydrophobic groups. It was proved that two kinds of binding mechanisms of surfactant/gel and different kinds of hydrophobic clusters existed in gels containing both physical and chemical networks.