Papers by Keyword: Gypsum

Abstract: In this work, the waste gypsum from industry is repurposed to add value in the medical field by transforming it into Plaster cast. The waste gypsum or calcium sulfate dihydrate is heated to a temperature of 120 °C for three hours to obtain calcium sulfate hemihydrate or Plaster of Paris. Subsequently, it is mixed with water in a 1:1 ratio before embedded on gauze. To enhance the strength of the plaster cast, different types of starch-based adhesives are mixed with plaster solution to investigate their impact on shaping and the strength of the plaster. Three types of starch, including potato starch, tapioca starch, and cornstarch, are utilized. After testing the strength of plaster cast mixed with adhesive starch, it is found that with 5% potato starch, the plaster cast exhibits the highest strength among all variants. In addition, its result from SEM indicated that the potato starch was distributed and packed tightly onto gauze.

Abstract: Expansive soils are known to show significant volumetric changes in response to changes in the moisture content. Such soils swell when the moisture content is increased and shrink when the moisture content is decreased, thereby causing distress and damages to structures founded on them. Construction developments on naturally occurring expansive soils are usually problematic. This study examines the properties of expansive soil obtained from the city of Muscat in Oman. The expansive soil samples were further treated with gypsum, which was obtained from waste plasterboards, at varying quantities of 3%, 6%, 9% and 12% by mass in an attempt to stabilize the soil. Based on USCS classification system, the expansive soil was identified a poorly clay with high plasticity (CH) with AASHTO classification of A-6. The pH test confirms the reaction between expansive and gypsum, while both the compaction and unconfined compression strength (UCS) tests revealed the optimum percentage of gypsum required to enhance the properties of expansive soil to be 9% by mass. The unconfined compression strength (UCS) test yielded a 37.7% increase over that of untreated expansive soil at 28 days of curing. The California Bearing Ratio (CBR) test of the treated soil yielded a 57% increase in CBR value for expansive soil treated with 9% of waste gypsum over untreated expansive at the unsoaked state and 70% at soaked state. Overall, a solid understanding of the physical and engineering properties of expansive soil, and the confirmation of the potential use of gypsum for its stabilization, was achieved in this study.

Abstract: Mortar is another construction medium made of cement, which is mixed with sands and water, and lime is applied to increase the product's longevity. The gypsum renders workability to make mortar or concrete by keeping the cement in plastic state at early age of hydration. The gypsum is called the retarding agent of cement because the gypsum which is mainly used for regulating the setting time of cement. To get the optimal setting time for optimum compressive strength, gypsum in the cement needs to be control. Cement setting time when it hydrates and renders cement paste when combined with water. The objective of this research is to analyze the effect of different amount in Ordinary Portland Cement (OPC). Vicat apparatus was used to analyze the initial setting time of cement paste. Gypsum and clinker were used in production of mortar with the size 50 mm x 50 mm x 50 mm. This research deals with observation of the cement setting time to point out some differences that would effect to strength of mortar. The results reveal that control gypsum with 4% of gypsum has the highest strength as compared to 0% of gypsum and 8% of gypsum. The setting time of cement paste are discussed with respect to their influence on the strength of mortar.

Abstract: The article covers the research of the chemical and mineralogical compositions of mortars used in the construction of architectural monuments of Uzbekistan in the 9^th-12^th centuries, which is based on the study of chemical composition, X-ray and differential thermal analyzes. Comprehensive study of the building materials used in mentioned monuments will allow development of identical modified solutions to preserve the value of architectural monuments.

Abstract: The main results of the study of the influence of man-made products of the metallurgical industry on the properties and structure of gypsum binder are presented. It has been proved that the introduction of man-made modifiers, metallurgical dust, and slag leads to an increase in the strength properties and electric conductivity of the material, but, over time, the waste efficiency decreases. The use of Portland cement as an activator leads to the formation of amorphous hydration products based on calcium hydrosilicates, which bind calcium sulfate crystals and provide an increase in the physicomechanical characteristics and electric behavior of the gypsum composite.

Abstract: Fiber-gypsum-cement-vermiculite-concrete composites with use of gypsum, Portland cement, volcanic ash, expanded vermiculite and basalt fibers are considered. The results of studies of the compositions and physical and mechanical properties of fiber-gypsum-cement-vermiculite-concrete composites, the dependence of the composite characteristics on the reinforcement with basalt fibers are presented. Graphical interpretations of regression equations for compressive and flexural strength of composites are presented.

Abstract: Currently, the use of board materials as a material intended for the dry construction of building structure cladding in the building industry has become widespread. The most common types of board materials include wood-based boards (particle, fibre, laminated / plywood, oriented strand boards [OSB]), cement-bonded particleboards and gypsum plasterboards or gypsum fibre boards. In the case of board materials based on inorganic binders, these are most often represented by boards in which the fillers used are bonded by plaster or cement. Wood can then be used as filler, which is predominantly an assortment of inferior-quality trees or comes from a short rotation coppice, treated by various technological processes. Microstructure and material composition have the greatest influence on the physical and mechanical properties of the boards. The use of the boards in the internal or external environment is determined by their individual properties. Another indicator for the possible use of boards is the form of moisture with which the board comes into contact after installation into the structure. For the external environment, the boards have to withstand mainly liquid moisture; in contrast, in an internal environment, the boards come into contact mainly with air humidity. The diffusion properties of the individual products are also crucial for the overall design and use of the boards for structure cladding.

Abstract: The construction industry has focused on trying to minimize and control the environmental impacts caused within the process of production and manufacture of fired bricks, for this reason the present research proposes five different alternative mixtures for the elaboration of ecological bricks, four of these based on soil-cement and one obtained through a geopolymerization process, using raw materials from the amazon region and the southern highlands of Ecuador, such as soil from the Centza mine (MC), sand from the Quiringue mine (MQ), organic correctors of husk rice (RH ), peanut shell (PS), natural gypsum (G) from the Malacatos sector and fired brick residues from the same sector. The raw materials were characterized (analysis: physicochemical and mineralogical); the soil-cement-based combinations used different percentages of substitution of organic correctors and gypsum, the optimum percentage of water and cement was determined through the compaction test and resistance to simple compression respectively, the samples were cured and tested at ages of 7, 14 and 28 days. In the geopolymerization process, an alkaline solution NaOH was used in different concentrations of molarity and solution contents, the specimens were cured at temperatures of 90 °C, 120 °C, 150 °C, 180 °C and 200 °C. The different combinations were subjected to indirect traction with the purpose to determine the optimal mixture and subsequent estimation of the compressive strength of bricks applying the Griffith criterion, the results were validated by the finite element method, obtaining strengths of 4 MPa in the combination soil-cement sand (SC_Ar1), in soil-cement rice husk (SC_RH2) and soil-cement peanut shell (SC_PS2) mixtures its resistance is 3 MPa, while in the soil-cement gypsum (SC_G4) mixture the resistance is 6.90 MPa and finally the resistance in geopolymeric mixture (GBW) is 13.75 MPa; In this way, the optimal combinations comply and increase the resistance to simple compression of bricks by 35% the SC_Ar1 mixture, 130% in the SC_G mixture with respect to the spanish standard and 129% the GBW mixture with respect to the ecuadorian standard.

Abstract: The paper describes the methodology of processing of the experimental data from the study of the hardening process of the binder paste, which allows to reveale information hidden in the results and objectively divide the period of structure formation into steps that differ in mechanisms and conditions. The proposed method has a universal character, is designed to study compositions of a heterogeneous structure and is implemented using experimental data on the plastic strength of gypsum binder paste as a simplified model of such a composition. It consists of two stages - the transition to normalized values and coordinate transformation to adequately display the observed processes of structure formation. To determine the type of the corresponding coordinate transformation, Erofeev and Kolmogorov equations were considered, which describe, in particular, crystallization processes. Based on the proposed equations, a physically reasonable choice of coordinate transformations of the re-logarithmic type was carried out. Processing the data on the plastic strength of the hardening gypsum binder paste as a model of the composition of an inhomogeneous structure allows us to identify the main stages of structure formation characterized by linear dependencies and transition stages in which qualitative transformations of the regime of change in plastic strength during hardening are observed. The separation of the total time of structure formation at the step is fixed on the graphs of changes in the corresponding properties, and the transition stages correspond to the points of change in the angular coefficients of the obtained dependencies. It is shown that the stationary step of structure formation corresponding to the stable maintenance of supersaturation is reflected in the general linear section on the graphs. It is shown that the time of occurrence of transition stages recorded during the measurement of plastic strength approximately corresponds to the setting time obtained by regulatory methods. A geometric interpretation of the angular coefficients of the obtained dependences which allows one to determine the structure of growing nuclei of a new phase was considered. The proposed technique can be applied to control the processes of structure formation of heterogeneous composition compositions.

Abstract: The studies’ results to determine the gypsum, ash and Portland cement components proportions, which would ensure a decrease in the specific binder consumption, as well as the ash grain composition’s effect on the properties of the gypsum cement pozzolan composite, are presented. It was revealed that the use of volcanic ash together with Portland cement in gypsum concrete composites allows reducing gypsum consumption by up to 50% without a significant decrease in strength characteristics. At the same time, the developed gypsum concrete composites have increased water resistance. The influence of the ash particle size distribution on the strength properties of the composite is ambiguous; in the compositions with a high ash content it is advisable to use larger fractions, and with a content of less than 50% ash in the composite, - the small fractions. To study the parameters’ effect of the dispersed reinforcement with basalt fibers on the properties of a gypsum-cement composite, an experiment with such a second-order composite rotatable plan as regular hexagon was conducted. It was found that the maximum values ​​of optimization parameters are observed in the central area of ​​the plan with and . The compressive strength of a fiber gypsum cement pozzolan composite increases by 1.15-1.18 times, when bending, by 1.56-1.72 times with respect to the strength of the initial matrix.