Applied Mechanics and Materials Vols. 174-177

Abstract: The correlation between the ratio of styrene-acrylic latex to sulphoaluminate cement and the resistance of latex modified sulphoaluminate cement mortar to hydrochloric acid corrosion was investigated. The weight change rate, compressive strength, and flexural strength of various latex modified cement mortar in the hydrochloric acid solution at different ages were tested and the samples appearance was observed. The results show that the resistance of latex modified sulphoaluminate cement mortar to hydrochloric acid corrosion is related to the latex/cement ratio. With the increase of the latex/cement ratio, the resistance performance of sulphoaluminate cement mortar to hydrochloric acid corrosion was improved firstly and then decreased. When the polymer/cement ratio was 0.2, the latex modified cement mortar presented the highest ability in compressive strength, flexural strength, weight change rate, and the appearance, showing its excellent resistance to hydrochloric acid corrosion.

Abstract: A novel xanthan-g-poly (acrylic acid)/ organic montmorillonite (XG-g-PAA/OMMT) superabsorbent polymer were synthesized by free-radical graft polymerization in aqueous solution using potassium persulfate as a free radical initiator and methylenebisacrylamide as a crosslinker, and then organic montmorillonite (OMMT) was introduced as filler into superabsorbent. The effects of reaction variables were systematically optimized to achieve a superabsorbent with swelling capacity as high as possible. Under the optimal synthesis condition, the polymer attained the best water absorbency of 882 g/g in distilled water and 107 g/g in 0.9 wt% NaCl solution. And such excellent character could be important to use in many fields, for example, in agricultural and horticultural applications.

Abstract: Small molecular monomer and initiator were added to cement mixture, in situ polymerization had occurred under the action of initiator with the cement hydration, and polymer network was produced, and thus the toughness of cement paste was improved. The toughness of in situ toughening mortar had been measured through flexural/compressive ratio, and modification mechanism had been revealed through MIP, SEM and TG-DTG. The results show that, flexural/compressive ratio of in situ toughening mortar has been enhanced greatly compared with reference; Many polymer films are formed in hardened cement mortar, and hydrolysis product of polymer can react with cement hydration product Ca(OH)2. Physical adhesion between polymer films and cement hydration products and chemical bonding between polymer and cement hydration products are primary causes to improve toughness of cement mortar.

Abstract: Organified Attapulgites (AT) were grafted with 3-(trimethoxysilyl) propyl methacrylate ( KH570 ) on the surface of AT particles. Then, the modified AT (AT-g-KH570) and untreated AT particles were compounded with polypropylene (PP) to prepare PP/AT-g-KH570 and PP/AT composites respectively. The morphology, chemical structure and mechanical properties of the composites were also investigated with scanning electron microscopy (SEM), Fourier-transform infrared spectra (FTIR) and mechanical testing. The FTIR results showed that the KH570 is grafted on the AT particles. The tensile strength and izod impact strength of PP/AT-g-KH570 composites were improved obviously than those of PP/AT composites. The izod impact strength of PP/AT-g-KH570 composites show the maximum and was enhanced 50 % at 1 wt% loading, which contributed to homogeneous dispersion of particles and enhanced the interfacial interaction between modified AT particles and PP matrix.

Abstract: Plain concrete is susceptible to cracking under aggressive environment such as in freezing shaft. And addition of steel fibres in plain high strength concrete is proved to be effective in cracking resistance and brittleness improvement, etc. This paper presents results of experimental investigation carried out to study the mechanical properties of steel fibre-reinforced concrete having volume fractions of 0.38%, 0.51% and 0.64% for two types of fibres respectively. The results of this study revealed that there is an increase for all the mechanical properties such as compressive strength, split tensile strength, modulus of elasticity and flexural strength. Enhancement for split tensile strength and flexural strength is more evident than compressive strength.

Abstract: A barium ferrite modified 0–3 cement-based piezoelectric composite was fabricated with piezoelectric ceramic [0.08Pb(Li1/4Nb3/4)O•0.47PbTiO3•0.45PbZrO3], sulphoaluminate cement and barium ferrite by compressing technique. It is well known that in the process of making piezoelectric composites，polarization is very critical, which is the process of domain structure's motion and development in a piezoelectric composites. Without the polarization, the composites will have no piezoelectric properties. So the influences of poling temperature on the piezoelectric and dielectric properties, electromechanical coupling property and acoustic impedance were investigated. And the poling temperature were selected at 30°C、50°C and 80°C. The results showed that the optimum poling temperature were 80°C.

Abstract: Mechanical grinding method was employed in this study to disperse CaCO3 whiskers in cement matrix. Mechanical properties of the ground whisker reinforced cement were measured. It is shown that the mechanical grinding method was advantageous to the dispersion and mechanical properties of composites. But the grinding process must be proper to assure a certain length and integrality of the whiskers. Crack deflection and whisker pullout mechanisms could account for the strengthening and toughening effects caused by whiskers.

Abstract: The sulphuric acid erosion resistance of high strength concretes containing limestone powder,titanium slag and silica ash were studied by accelerating cycle sulphuric acid soak tests. It indicates that the introduction of super-fine mineral powders into concrete can improve its sulphuric acid erosion resistance. With fixed 10% limestone powder, blending 10% titanium slag or 15% silica ash can remarkably enhance sulphuric acid erosion resistance of concrete. The concretes containing mineral admixtures such as limestone powder, titanium slag and silica ash can be used in acid rain abundant area.

Abstract: The mechanical properties of concretes containing super fine mineral admixtures such as limestone powder, titanium slag, lithium slag and silica ash have been investigated by compression tests. It was found that 10% limestone powder used in cocncrete is beneficial to compressive strength, it reaches 111Mpa after 28 days curing. The optimum mixing amounts of titanium slag, lithium slag and silica ash are 20%, 10% and 10%, respectively. All their 28d compressive strengths exceed 100MPa, reach super-early and super-high strength concrete level. By introducing mineral admixures into concrete, the cement consumption in concrete can be greatly reduced.

Abstract: Design concrete mix used in the PHC pile production, silica sand powder and slag powder as a concrete admixture, replace a certain percentage of Portland cement, under the premise of meeting the PHC pile production requirements. After the steam curing, determinate the demould strength of concrete and after autoclave curing, determinate the compressive strength of concrete. Test results show that it is feasible for the use of silica sand powder and slag powder instead of Portland cement, in which the proportion of concrete admixtures up to 45%. Silica sand powder and the amount of slag powder were mixed with 150 kg/m3, 50 kg/m3, the concrete demould strength up to 49.1 MPa and the compressive strength after autoclave curing up to 89.0MPa, to achieve requirements of the national standard GB13476.