Plaster Mixtures Research Articles

Influence of PCM Admixture on Thermal Behavior of Composite Plaster

Experimental investigation of the effect of phase change material (PCM) admixture on thermal properties of composite plaster is researched in the paper. Due to its latent heat storage, the applied PCM represents promising way for reduction of buildings energy consumption spent for heating and air conditioning. The investigated composite material is based on commercial dry plaster mixture modified by microencapsulated PCM admixture Micronal DS 5038 produced BASF. The particle size distribution of PCM admixture, original dry plaster mixture, and particular dry mixture with PCM addition are measured on laser diffraction principle. For characterization of the developed materials, measurement of their basic physical properties is done. Specific attention is paid to thermal properties of research materials, whereas the heat transport parameters are measured using transient impulse device, and the DSC (difference scanning calorimetry) analysis is applied for determination of temperatures of phase transitions, enthalpy of fusion and crystallization, and temperature dependent specific heat capacity. The obtained results show significant improvement of the heat storage capacity of PCM modified plasters in dependence on temperature, what can be beneficially used for regulation of the indoor climate.

An Experimental Study of Crack Coalescence Behaviour in Rock-Like Materials Containing Multiple Flaws Under Uniaxial Compression

Experiments on man-made flawed rock-like materials are applied extensively to study the mechanical behaviour of rock masses as well as crack initiation modes and crack coalescence types. A large number of experiments on specimens containing two or three pre-existing flaws were previously conducted. In the present work, experiments on rock-like materials (formed from a mixture of sand, plaster, limestone and water at mass ratio of 126:9:9:16) containing multiple flaws subjected to uniaxial compression were conducted to further research the effects of the layout of pre-existing flaws on mechanical properties, crack initiation modes and crack coalescence types. Compared with previous experiments in which only three types of cracks were found, the present experiments on specimens containing multiple flaws under uniaxial compression revealed five types of cracks, including wing cracks, quasi-coplanar secondary cracks, oblique secondary cracks, out-of-plane tensile cracks and out-of-plane shear cracks. Ten types of crack coalescence occurred through linkage among wing cracks, quasi-coplanar secondary cracks, oblique secondary cracks, out-of-plane shear cracks and out-of-plane tensile cracks. Moreover, the effects of the non-overlapping length and flaw angle on the complete stress–strain curves, the stress of crack initiation, the peak strength, the peak strain and the elastic modulus were also investigated in detail.

Geomaterials under the microscope: a color guide: building stone, roofing slate, aggregate, concrete, mortar, plaster, bricks, ceramics, and bituminous mixtures

Geomaterials under the microscope: a color guide: building stone, roofing slate, aggregate, concrete, mortar, plaster, bricks, ceramics, and bituminous mixtures

Alternative Preparation of Sulphated Binders from Secondary Raw-Material Resources

The insufficient occurrence of raw material resources on our territory was one of the historical reasons for marginal production of sulphated binders from secondary raw-material resources. Also the unprofitability of material production based on calcium sulphate was related to this fact. This was changed in the end of the last century when formation of waste raw materials increased with industrial development. Secondary gypsums became basic raw material for production of plaster boards, plaster mixtures and anhydrite self-levelling mixtures. Wet flue gas cleaning desulphation process during which the energogypsum is formed is nowadays realised in major part of our power stations. Annual production of the energogypsum produced in this way in particular power stations is about 250 kt. The energogypsum is generally stored in stock piles as a so called stabilisate and partially is delivered to cement works as a solidification regulator. Chemogypsum is produced in chemical works where waste waters with content of SO42- occur, which must be desulphated with lime in water ambient. Further it is formed in citric acid productions where also sulphated waters occur. Last but no least it is also produced in industrial production of phosphates. Production of titanium dioxide is another example of the industry where the possibility of gypsum formation exists.

Influence of Zeolite Additive on the Properties of Plaster Used for External Walls from Autoclaved Aerated Concrete

Enclosures that had been built from elements of autoclaved aerated concrete (AAC) often are covered with plasters. Some adhesion problems between plasters and surface exist during the mechanized covering of surfaces of the mentioned enclosures with plaster. Some dispersible additives (vinyl acetate polymer or derivatives of acrylic acid esters) are used to improve the adhesion. Another problem is the increased water absorption of AAC elements, therefore water retarding additives (cellulose esters) are used in the mixture of plasters. Due to insufficient amount of water in the mixture of plasters, the hydration of cement minerals slows down. Influence of the natural zeolite – clinoptilolite on the properties of plaster is analyzed in this work. It was found that this additive effectively absorbs water and thus, ensures adequate hydration of cement minerals. When in the mixture of plaster the sand is changed by clinoptilolite in amount of 15 % the structure slightly compacts, the compressive and flexural strength of hardened plaster increase by 47 % and 12 % respectively and the adhesion to a surface of the AAC element increases by 44 %. Drying shrinkage, water vapor resistance factor and coefficient of capillary absorption remain unchanged.DOI: http://dx.doi.org/10.5755/j01.ms.19.2.4441

Lightweight plaster materials with enhanced thermal properties made with polyurethane foam wastes

This paper presents a study of the properties and thermal behaviour of plaster with polyurethane foam wastes. Plaster mixtures, prepared using differing volumes of polyurethane foam waste from two different sources, were ground to different granulometric sizes. The characteristics of the specimens were defined and tested by fixing the consistency at a good workability and then studying the mechanical properties, Shore C hardness and adherence to ceramic materials after both 7 and 28 days. The thermal behaviour was examined via thermogravimetry and thermal conductivity analysis, correlating the latter with the apparent density values of the plaster polyurethane material. The interface of materials was observed by Scanning Electron Microscopy (SEM). The results show that increasing the polyurethane quantity decreases the density and mechanical properties of the plaster while increasing its thermal resistance proportionally to the reduction in density. These results suggest that the use of plaster containing polyurethane foam waste is comparable to that of plaster lightened with conventional materials.

Calcareous fossil inclusions and rock-source of Maya lime plaster from the Temple of the Inscriptions, Palenque, Mexico

This paper introduces for the first time the study and description of fossil remains preserved in lime plaster from a Maya site, the Temple of the Inscriptions in Palenque, one of the most outstanding Classic Period cities of the Maya culture in Mesoamerica.Plaster was removed with EDTA carbonate-digestive technique and results based on ultrastructural microanalysis reveals marine fossil remains of shells and calcareous debris correlated with organisms of several taxa including Foraminifera, Gastropod, Bivalvia, and Cnidarian.This fossil material is associated with several Tertiary fossil-bearing strata in the surroundings of Palenque. Additionally, results of WDX testing on white lumps of plaster show a characteristic MgO/CaO ratio consistent with a dolomitic limestone source linked to the Tenejapa geological unit (Paleocene). Plaster of The Temple of the Inscriptions is best described as a dolomitic lime plaster.Calcareous fossil material in plaster mixtures is present mainly as micro-aggregates and lime dust, such material may come from a fossil-bearing rock intentionally selected that was burned and crushed. This also suggests that low-temperatures can cause burns to incomplete calcination of rocks and, consequently, that fossils can preserve their recognizable, morphological features.

Model Test of Socketed Depth’s Influence on Bearing Mechanism in Rock-Socketed Pile

The socketed depth in rock-socketed pile can influence its bearing mechanism largely. At present the numerical simulation is used to study the socketed depth’s influence on pile’s bearing mechanism. It can reveal the pile bearing mechanism in some degree; however, there are some defects and limitations in simulation for its assumptions and simplifications. Based on the pile foundation of Tian-xing-zhou Bridge, the model test is conducted to study the socketed depth’ influence on rock-socketed pile bearing mechanism. In the model test, the socketed depth of model piles are made different ranging from 60mm to 200mm at the step of 20mm, and the bed rock is simulated with mixture of sand and plaster, the rock-soil overlain the bed rock is simulated with silty sand, the pile is simulated with organic glass rod according to similarity principle respectively. The results show that the settlement of top of model pile is smaller and the ratio of point resistance is smaller when the socketed depth is longer. When the socketed depth reaches 5D (D represents diameter of model pile), the ratio of point resistance is no more than 40%, and it is less than 1% when 8D. The conclusions drawed from model test are useful to deciding the length of pile foundation in Tian-xing-zhou Bridge.

Model Test of Roughness’ Influence on Bearing Mechanism in Rock-Socketed Pile

The interface roughness between pile and rock in rock-socketed pile can influence its bearing mechanism largely. At present the numerical simulation, which simulates the interface roughness with changing the surface shape or interface friction coefficient, is used to study the interface roughness’ influence on pile’s bearing mechanism. It can reveal the pile bearing mechanism in some degree; however, there are some defects and limitations in simulation because of its assumptions and simplifications. Based on the pile foundation of Tian-xing-zhou Bridge, the model test is conducted to study the interface roughness’ influence on rock-socketed pile bearing mechanism. In the model test, the surface of model piles are made different ranging from smooth to rough, and the bed rock is simulated with mixture of sand and plaster, the rock-soil overlain the bed rock is simulated with silty sand, the pile is simulated with organic glass rod according to similarity principle respectively. The results show that load-settlement curves grow more gently, the ultimate bearing capacity is bigger, the proportion of point resistance is lower, and the shaft resistance is bigger which reaches more than 70% of total loading as the surface of pile is rougher. The conclusions are useful to deciding the length of pile foundation in Tian-xing-zhou Bridge.

Development of an improved laboratory production technique for the coffee berry borer Hypothenemus hampei, using fresh coffee berries

AbstractThe suitability of a mixture of plaster of Paris and charcoal as a means to regulate the moisture content of coffee berries and the relative humidity (moisture conditions) of the rearing environment and its impact on rearing the coffee berry borer (CBB), Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae), was evaluated under laboratory conditions using two types of coffee. Coffee berries were kept individually in vials with a 1‐cm layer of the mixture, and the fresh weight of the berries was assessed, as well as the penetration of CBB into the berries, its survival, and its progeny production over a period of 55 days. Significantly higher survival and progeny production was achieved when using the mixture regardless of the coffee type. Compared to the vials without plaster of Paris/charcoal, a six‐ to sevenfold increase in survivorship of the F1 was recorded when using plaster of Paris/charcoal and in the latter treatment berries harboured on average more than 100 individuals, whereas only 1.7 in the vials without plaster of Paris.

Osteogenic activity of the mixture of chitosan and particulate dentin

To evaluate the healing effect of a mixture of chitosan and particulate dentin, a 8-mm-diameter critical size defect was created in the calvarium of 75 rats. The rats were divided into four experimental groups and a control group (no treatment). The defects in the experimental groups were grafted either with pig particulate dentin (group 1), a mixture of particulate dentin and plaster of Paris (group 2), particulate dentin and chitosan (group 3), or chitosan only (group 4). Rats in each group were sacrificed 2, 4, and 8 weeks after implantation. All experimental groups showed more new bone formation when compared to the control group. Additionally, all groups exhibited more bone growth at 8 weeks than at 4 weeks after implantation. It was concluded from this study that defects treated with particulate dentin powder-chitosan mixture may mediate an excellent effect on the formation of new bones.

Effect of laboratory culture conditions on population growth ofProisotoma minuta(Tullberg) (Collembola: Isotomidae)

AbstractThe collembolanProisotoma minuta(Tullberg) was successfully maintained in a laboratory culture that could be used to produce large numbers ofP. minutaof standard size and physiological condition. The general life history ofP. minutawas studied using a substrate comprising a mixture of plaster of Paris and charcoal with baker's yeast as food. The mean time taken for eggs to hatch following oviposition was 10.6 ± 1.3 days at 17.5°C and 6 ± 0.5 days at 23°C. Conditions in the culture were very important for the production of large insect populations. Growth of the cultures was limited by the increasing population size and was probably affected by contamination of the habitat by the deposition of excretory materials.Proisotoma minutafrom a population that had ceased egg production started oviposition after individuals were transferred to a fresh plaster of Paris and charcoal habitat.

Guided Tissue Regeneration of the Mixture of Human Tooth-Ash and Plaster of Paris in Dogs

This study evaluated the efficacy of periodontal tissue regeneration using guided tissue regeneration (GTR) with a mixture of tooth ash and plaster as a bone substitute material in the treatment of class II furcation defects in dogs. GTR was performed at the site of a surgically formed mandibular premolar bifurcation area in dogs. Four adult dogs were used in the animal study. The animals were in a good periodontal state without any systemic disease. A resorbable membrane (Bio-Gide®, Swiss) and bone graft material using a mixture of tooth ash and plaster were used to examine the biological activity. The defect in the control group was filled a Bio-Gide® only. For the experimental group, the defects were filled with a mixture of tooth ash and plaster and covered by a Bio-Gide®. Oral rinsing with 0.12% chlorhexidine was performed twice a day for 2 weeks. In control group, new bone formation was observed adjacent to the preexisting bone. Soft tissue ingrowth was also noted. In experimental group, new lamellar type trabecular bone formation as well as centum and PDL regeneration was observed in the base of the infrabony pocket. More bone regeneration would be expected when GTR is performed using a mixture of human tooth-ash and plaster of Paris as a bone graft material.

Effect of Fibrin Sealant on Early Bone Healing with Tooth Ash and Plaster of Paris in Ovariectomized Rats

This study examined the role of tissue adhesives during early healing and the effects of tooth ash and plaster of Paris on bone healing in the presence of osteoporosis. Sixty rats were assigned to five groups randomly and each group was further divided into two subgroups, which were examined 4 and 8 weeks after implantation. Histologic sections and histomorphometric analysis of defects were obtained 4 and 8 weeks after surgery. Bone formation was significantly better in the non-ovariectomized groups compared to the ovariectomized group. A mixture of tooth ash and plaster of Paris is recommended, but not tissue adhesives, in ovariectomized cases.

Low-field variation of magnetic susceptibility measured by the KLY-4S Kappabridge and KLF-4A magnetic susceptibility meter: Accuracy and interpretational programme

The KLY-4S Kappabridge and KLF-4A Magnetic Susceptibility Meter enable automated measurement of susceptibility variation with field in the ranges of 2–450 A/m and 5–300 A/m (in effective values), respectively. Unfortunately, the measurement accuracy decreases with decreasing field and it is not easy to decide whether the susceptibility variation at the lowest fields is natural phenomenon or results from measuring errors. To overcome this problem, the accuracies of both the above instruments were investigated experimentally using artificial specimens (mixture of pure magnetite and plaster of Paris) with variable susceptibilities ranging from 1 × 10−5 to 5 × 10−2. The complete curve of the field variation of susceptibility of each specimen was measured 10 times and the relative error was calculated for each field.

Periodontal Regeneration Using the Mixture of Human Tooth-ash and Plaster of Paris in Dogs

The ultimate goals of periodontal therapy include not only the arrest of periodontal disease progression, but also the regeneration of structures lost to disease where appropriate. An appropriate periodontal regeneration should be restored original normal alveolar bone, periodontal ligament, and cementum which is destructed by the periodontal disease. Additionally, the periodontal ligament fibers must be anchored into the cementum. However, periodontal healing following a conventional periodontal treatment occurred junctional epithelial attachment. As a result, various materials such as bone replacement grafts, barrier membranes, and biologic modifiers currently used for the regeneration of periodontal tissue defects.1) GTR technique is for the periodontal tissue regeneration by inducing the fibroblast or progenitor cells originated from PDL not allowing epithelium and gingival connective tissue ingrowth. Non absorbable membrane has some problems in that early exposure of membrane and additional surgery for the removal of the membrane. It has been documented that bacterial infection caused by the early exposure of the membrane was one of the GTR failure factors and even if the GTR succeed, the amount of the tissue regeneration was decreased. To overcome these problems, bioresorbable membrane was used, but bioresrobable membrane had some disadvantages in maintaining the space for

신발 금형의 쾌속제작기술 개발 및 그 적용에 관한 연구

RP&M (Rapid Prototyping and Manufacturing) is the most appropriate technology for the small-lot production system, because the production cycle is getting shorter owing to various needs of the consumer. In this paper, rapid tooling technology is applied to the casting process. The casting process has the ability to reflect complicated shapes in one process. But it has not been widely used to make a die and mold because of the poor surface quality caused by air bubbles on the surface of the casting product. In this study, the porous casting mold is fabricated from a mixture of plaster and water-soluble binder. The porous casting mold can improve the characteristics of casting products with the help of the vacuum sealed casting process. The vacuum sealed casting process is an advanced technology that removes the air bubbles between the porous casting mould and the liquid metal, thus making the surface of the casting product finer. The purpose of this paper is to develop a high quality shoe mold using porous casting mold and to apply the RP&M technology to the shoe industry .

Sub-surface structures and collapse mechanisms of summit pit craters

Summit pit craters are found in many types of volcanoes and are generally thought to be the product of collapse into an underpressured reservoir caused by magma withdrawal. We investigate the mechanisms and structures associated with summit pit crater formation by scaled analogue experiments and make comparisons with natural examples. Models use a sand plaster mixture as analogue rock over a cylinder of silicone simulating an underpressured magma reservoir. Experiments are carried out using different roof aspect ratios (roof thickness/roof width) of 0.2–2. They reveal two basic collapse mechanisms, dependant on the roof aspect ratio. One occurs at low aspect ratios (≤1), as illustrated by aspect ratios of 0.2 and 1. Outward dipping reverse faults initiated at the silicone margins propagates through the entire roof thickness and cause subsidence of a coherent block. Collapse along the reverse faults is accommodated by marginal flexure of the block and tension fractures at the surface (aspect ratio of 0.2) or by the creation of inward dipping normal faults delimiting a terrace (aspect ratio of 1). At an aspect ratio of 1, overhanging pit walls are the surface expressions of the reverse faults. Experiments at high aspect ratio (>1.2) reveal a second mechanism. In this case, collapse occurs by stopping, which propagates upwards by a complex pattern of both reverse faults and tension fractures. The initial underground collapse is restricted to a zone above the reservoir and creates a cavity with a stable roof above it. An intermediate mechanism occurs at aspect ratios of 1.1–1.2. In this case, stopping leads to the formation of a cavity with a thin and unstable roof, which collapses suddenly. The newly formed depression then exhibits overhanging walls. Surface morphology and structure of natural examples, such as the summit pit craters at Masaya Volcano, Nicaragua, have many of the features created in the models, indicating that the internal structural geometry of experiments can be applied to real examples. In particular, the surface area and depth of the underpressured reservoir can be roughly estimated. We present a morphological analysis of summit pit craters at volcanoes such as Kilimanjaro (Tanzania), San Cristobal, Telica and Masaya (Nicaragua), and Ubinas (Peru), and indicate a likely type of subsidence and possible position of the former magma reservoir responsible for collapse in each case.

Grafting of large defects of the jaws with a particulate dentin–plaster of paris combination

Objective. The purpose of this report is to show the usefulness and discuss the effects of a particulate dentin and plaster of paris combination as a bone graft material in jaw defects. Study design. This was a retrospective evaluation of 10 patients with jaw defects who underwent grafting with a combination of particulate dentin and plaster of paris. The material was used when the defects were more than 20 mm in diameter. The ratio was 2: 1 by weight. Patients were examined for any evidence of infection and recurrence during the follow-up periods. Results. During a mean follow-up of 52.2 months (range, 50 to 57 months), patients had minor immediate postoperative complications. These complications were swelling and perforation; they were treated without problems through use of incision and drainage, antibiotic treatment, and buccal flap. Conclusions. On the basis of the results that we obtained radiographically and clinically, it may be concluded that the particulate dentin plaster mixture is a useful and readily available material for bone substitute. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;88: 22-5)

Osteogenic response of rabbit tibia to hydroxyapatite particle–Plaster of Paris mixture

A mixture of hydroxyapatite (HA) particles and plaster of Paris (POP) with saline solution was injected into the bone marrow of 30 unilateral tibiae of 30 rabbits. As a control, POP with saline solution was similarly injected into the bone marrow of 30 unilateral tibiae of 30 additional rabbits. Five rabbits in each group were killed 2, 4, 8, 12, 24 and 40 weeks after injection. Histological examination was performed on three tibiae of five killed animals, and X-ray diffraction analysis of the bone marrow was performed on the remaining two tibiae. In two of three tibiae, bridges of new bone were formed between the hydroxyapatite particles and the cortical bone, 4 weeks after the injection of the HA particle–POP mixture. New bone formation was seen in all three tibiae at 8 weeks and thereafter. No new bone formation was observed in the tibiae of the control group. The affinity index, a parameter of osteogenesis, was 0% at 2 weeks, 52.2±14.0% at 4 weeks, 74.8±5.3% at 8 weeks, 86.1±6.1% at 12 weeks, 90.1±8.3% at 24 weeks and 92.8±4.1% at 40 weeks after injection. Statistically significant increases were found between the affinity indexes of 2 weeks and 4 weeks and between those of 4 weeks and 8 weeks, p<0.03 and p<0.05, respectively. Between 12, 24 and 40 weeks, the indexes showed tendencies toward increases. X-ray diffraction of bone marrow of two tibiae into which HA particle–POP mixture or POP alone was injected showed that POP had disappeared 8 weeks after injection.