Karakteristik Mortar Polimer Epoxy Resin Dengan Fiberglass

Nowadays, the developments of technology in construction are progressing very rapidly, one of which is mortar without using cement material. This encourages the development of concrete and mortar technology so that it can be widely used to repair structural or non-structural damages. In these conditions, a binder is needed in the form of an epoxy resin polymer with added fiberglass to get a strong material result in a short time. A mixture of 75% sand and 25% epoxy resin from the volume of the test object resulted a mortar compressive strength of 35.50 MPa with a specific gravity of 1.505 kg/m3. The results showed that the variation of the compressive strength of the epoxy resin mortar without fiber was higher than the variation with fiberglass. This was due to the addition of fiberglass reducing the composition of the percentage of epoxy resin which results in reduced bonding power in the mixture. The flexural strength of a mortar with variations using fiberglass was 8 MPa and showed the best performance, although the difference was not too far from the variation without fiberglass. This was because the addition of fiberglass can reduce cracks, so that the fibers can bind well. The tests had been carried out including tests of the compressive strength, flexural strength, and Scanning Electron Microscope (SEM).

Recent Advances in Magnesia Blended Cement Studies for Geotechnical Well Construction—A Review

The current paper presents a literature review on the studies of incorporation of magnesia (magnesium oxide) into Portland cement material from the geotechnical well construction perspective. Starting with a comparison of application conditions between civil construction and geotechnical well cementing, this work reviewed the Portland cement categorizations, magnesia manufacturing routes at first. Then, the physical-chemical-mechanical properties were investigated which includes the reactivity of magnesia, expansion influence from its hydration, and carbonation/dehydroxylation of magnesia blended Portland cement. The development of cement material hydration modeling methods is also summarized. Moreover, the experimental characterization methods have also been elucidated including composition determination, particle size analysis, volumetric variation measurement, compressive strength testing, shear-bond strength testing, transition state analysis, etc. Meanwhile, the results and conclusions were extracted from the literature. Through this route, a comprehensive understanding of the scientific research progress on magnesia blended Portland cement development for geotechnical well construction is derived. Additionally, it is concluded that incorporating magnesia into Portland cement can provide benefits for this material utilization in geotechnical well constructions provided the reasonable tuning among the characteristics of magnesia, the downhole surrounding conditions, and the formulation of the cement slurry. Satisfying these pre-conditions, the effective expansion not only mitigates the micro-annulus issues but also increases the shear bonding strength at the cementing interfaces. Moreover, the caustic magnesia introduction into Portland cement has the potential advantage on carbon dioxide geological sequestration well integrity compared with the Portland cement sheath without it because of the denser in-situ porous matrix evolvement and more stable carbon fixation features of magnesium carbonate. However, since the impact of magnesia on Portland cement strongly depended on its properties (calcination conditions, particle size, reactivity) and the aging conditions (downhole temperature, pressure, contacting medium), it should be noted that some extended research is worth conducting in the future such as the synchronized hydration between magnesia and Portland cement, the dosage limit of caustic magnesia in Portland cement in terms of CO2 sequestration and the corresponding mechanical properties analysis, and the hybrid method (caustic magnesia, Portland cement, and other supplementary cementitious materials) targeting the co-existence of the geothermal environment and the corrosive medium scenario.

DESIGN AND FABRICATION OF CONCRETE-REINFORCED FLOATING PLATFORM FOR CANAL AND RIVER-SHORE PROTECTION

Erosion of canal and river-shore causes problems on agriculture activities and soil environment. This paper devotes to develop a floating platform to protect the shores. A concrete-reinforced floating platform was designed and fabricated in this study. Mechanical simulation was performed to ensure the design viability. The concrete-reinforced floating platform consists of three main parts: (1) steel structure, (2) foam-cement material, and (3) connecting joints. The dimension of the cement foam floating platform is 1.2 m in width, 3 m in length and 0.4 m in thickness. The cement used in this research is resistant to corrosion of sulfate and chloride from saltwater. Foam with density of 12 kg/m3 is mixed with concrete matrix so that the floating platform can float 60% or 0.16 m above the water surface. The foam cement material has the maximum compression stress of 1,951 kg ± 266.59 kg for the material density of 427.30 kg/m3 ± 19.30 kg/m3. The connecting joint part has the ultimate tensile load of 1,564 kg. The assemble floating platform has the compressive stress of 543.33 kg/m2 with the maximum vertical deformation of samples of 1 mm under the distribution load of 1,571 over the samples. Finally, from simulation with data from the material testing, the designed floating platform had a safety factor 3.46 which was higher than the design criteria of 3.

Mechanical Strengths of Sawdust-Ash-Admixed Gum Arabic Concrete

Gum Arabic and sawdust ash were used both as an emulsifier admixture and supplementary cement material to address some of the gaps between pozzolanic and conventional concretes. Four concrete mixtures of 1: 2.24: 2.71, with a water-cement ratio of 0.5, and cement content of 370 kg/m3, was used. The concrete mixtures were designated as M-00, M-00GA, M-10GAS, and M-30GAS, signifying the control, control with gum Arabic (GA), and mix with both gum Arabic and sawdust ash (GAS), respectively. The dosage was 0.5 % of GA and the SDA replacement by wt. % was at 10 % and 30 %, respectively. The concrete samples were cured for 90 days, and tested for mechanical strengths. The results showed that adding GA alone to concrete mixture improved the mechanical strengths of the concrete and the gum Arabic acted like an accelerator. When both GA and SDA were used together in the dosage of 0.5 % with 10 % and 30 % proportions respectively, the mechanical strengths of the concrete decreased. The findings also reported that the two-third strength ratio at 28-days of curing which is used for the conventional concrete in stripping the formwork, may not be appropriate for use on pozzolanic concrete. This is because of the delay in setting times and thus, attaining the required design strength. Therefore, it is proposed to be taken at an age beyond 28 days of curing to carter for the pozzolanic effects which starts well above 28-days.

Adhesive Ability of Different Oral Pathogens to Various Dental Materials: An in Vitro Study

This study provides a basis for selecting dental materials and lays a foundation for developing new dental materials. Four dental restorative materials were divided into two groups: Streptococcus mutans and Actinomyces viscosus, five root canal sealing materials were divided into two groups: Porphyromonas gingivalis and Enterococcus faecalis. Each material block was immersed in the corresponding group of the bacterial solution and cultured under anaerobic conditions at 37°C for 2, 4, 6, 8, 12, 16, 20, and 24 h. The adhesion of bacteria was observed, the number of different bacteria adhering to various material model disks was calculated at different time intervals under a scanning electron microscope. 24 hours later, the number of Streptococcus mutans and Actinomyces viscosus that adhered to the surface of the resin and the zinc phosphate cement material disks was the maximum. The number of Porphyromonas gingivalis and Enterococcus faecalis adhering to the surface of the AH Plus sealer block was the maximum. Streptococcus mutans and Actinomyces viscosus exhibited the strongest adhesion ability to the resin and the zinc phosphate cement material block. Porphyromonas gingivalis and Enterococcus faecalis showed the highest adhesion ability to the AH Plus sealer block.

Проблемы заколонных перетоков в скважинах с боковыми стволами и горизонтальным забоем

The article analyzes the main causes of fluid manifestations that occur in wells with side shafts and horizontal bottom at the stage of construction and operation of wells. It is established that the fluid manifestations are mainly due to the design features of such wells. The presence of overflow and interstratal overflows, in case of untimely detection and liquidation, can lead to emissions, accidents and large–scale environmental disasters. The cause of most complications at the stages of construction and operation of wells is the hydraulic connection of the drilled fluid–saturated formations with the wellbore, which accompanies all subsequent periods of well operation. To solve this problem, it is necessary to carry out repair and insulation works to eliminate overflow flows in wells with horizontal sections using blocking fluids for temporary insulation of the perforated part of the production string. Technological solutions for the elimination of intercolumn flows by pumping blocking tamponing compositions in the intervals of flow of liquids or gases, the installation of cut–off bridges to protect the productive layers from the cement material; carrying out insulation work through the upper part of the perforation zone. The authors propose the current directions of development of existing insulation technologies, taking into account the peculiarities of work in horizontal wells, in the construction of which use non–cemented shank–filters using physico–chemical and mechanical solutions. The selected technology and materials should ensure the filling of the entire porous medium and channels in the well and downhole section of rocks, as well as the optimal structure of the composition in a technologically acceptable time.

Application of New Bone Cement Biomaterials in Osteoporotic Compression Fractures

Silk fibroin (SF) is a kind of natural protein, which is widely used in biomedical materials because of its biodegradability, easy modification, biocompatibility and good mechanical properties. In this exploration, it was used as bone cement materials and compared with conventional bone cement materials to obtain the efficacy of different bone cement materials in the treatment of osteoporotic vertebral compression fractures. First, the effect of degumming time of silk in boiling on SF was analyzed. Then, hydroxyapatite silk fibroin (HA-SF) was added to calcium phosphate cement (Cap) by coprecipitation method. The properties of the composite bone cement were analyzed by morphology analysis and mechanical properties testing. Finally, 40 patients who underwent percutaneous kyphoplasty (PKP) from May 2019 to June 2020 were selected and divided into two groups. Among them, one group used the composite bone cement material proposed in this exploration, and the other group used the conventional bone cement material. Patients in different groups were evaluated for postoperative treatment. In the experiment, the sericin could be removed by boiling, and the SF short fiber could be peeled by boiling for a long time; the compressive strength of Cap material could be improved by adding HA-SF. At the same time, the introduction of SF could shorten the coagulation time under the premise of injectability, so as to improve the anti-collapse ability of Cap; the patients using different bone cement materials were compared, and the cobb angle, anterior height of vertebral body and VAS score of different groups were analyzed 3 days and 3 months after operation. The results show that the bone cement material proposed in this exploration can effectively treat osteoporotic vertebral compression fractures.