Gypsum Plaster Research Articles

Simulation of passive thermal retrofitting techniques in an earthquake-resistant building: A case study of a building in Thakle Namuna Basti, Melamchi, Nepal

Thermal comfort is a relatively emerging topic in the Nepalese context. The role of thermal comfort in building performance is foreshadowed by peoples’ emphasis on only the structural aspect and active heating/cooling systems. This paper analyzes the effectiveness of passive thermal retrofitting techniques in an earthquake-resistant building in a small community called Thakle Namuna Basti of Melamchi, Nepal. Only three retrofitting techniques are used in this simulation; the addition of gypsum plaster on the wall, the use of foam on the floor, and the application of double-glazed windows. The study was conducted through a two-phased survey, and simulation in TRNSYS. The heating and cooling loads before and after retrofitting are compared. It showed that applying passive thermal retrofitting techniques reduced the overall annual heating load by 35% in the winter but increased the overall cooling load by 4% in the summer.

Geometrical and environmental effect on fire behaviour of polyurethane foam slabs

AbstractThis study presents the results of a set of large‐scale fire tests performed on horizontal polyurethane foam slabs. Slab thickness, ignition location, and environment (free burn or corner wall) were varied over 23 individual tests. In a continuation of a previous study by the authors, four different slab thicknesses, five different ignition locations, and three environmental modification combinations were tested to examine the potential effects these parameters may have on the test outcomes. Wall configurations were composed of either gypsum plaster board or particle board wall linings and enclosed two sides of the foam slabs. The results obtained were heat release rate, peak HRR, total heat release, and effective heat of combustion, smoke production rate, total smoke production, specific extinction area and soot yield along with flame spread rate calculations obtained using a specifically designed sample tray. These were then analysed to quantify the effects of the test input parameter changes. Results highlight the influence of test input parameter changes on almost all the chosen fire metrics analysed. Slab thickness showed relatively straight forward linear changes to global metrics such as total heat release and total smoke production, while effective heat of combustion showed no change. The smoke production parameters of specific extinction area and soot yield showed minor trends towards higher values with increased slab thickness. Flame spread rates also showed an increased velocity with thicker slabs. Changes to the environment surrounding the foam slabs, from a free‐burning scenario to a corner wall configuration that obstructed two sides of the foam slab generally resulted in faster growth of HRR and higher peak values when compared to the free‐burn tests. This outcome was most obvious for the wall tests using combustible materials, where growth rates were comparative to an ultra‐fast t^2 fire, and peak HRR value rose to over triple that of the free‐burn test results. Flame spread rates were highly impacted by the addition of a corner wall, spread rates increased, and the overall pattern of spread rates across the face of the slabs changed entirely. The influence on smoke production values was minor, and for other smoke metrics, the scenario changes showed little influence. However, the values obtained for soot yields were approximately an order of magnitude lower than those given in standard reference books, such as the SFPE handbook for flexible polyurethane foam. This was an interesting additional finding as soot yield values are often directly used in CFD models to simulate smoke spread and determine life safety criteria in fire safety engineering (FSE).

Advanced materials engineering in historical gypsum plaster formulations

We show how historical gypsum plaster preparation methods affect the microstructure and the wettability properties of the final stucco materials. We reproduced a traditional Persian recipe (Gach-e Koshteh, ~14thcentury AD), which involves a continuous mechanical treatment during plaster hydration. These samples were compared with a laboratory-replicated historical recipe from Renaissance Italy (Gesso Sottile, ~15thcentury AD) and contemporary low-strength plaster. The Koshteh recipe induces the formation of gypsum platelets, which exhibit preferential orientation in the plaster bulk. In contrast, the Italian and low-strength plasters comprise a typical needle-like morphology of gypsum crystals. The platelets in Koshteh expose the more hydrophilic {010} face of gypsum in a much more pronounced manner than needles. Consequently, the Iranian plaster displays enhanced wettability, enabling its direct use for water-based decoration purposes, or as a fine finishing thin layer, without the need of mixing it with a binder material. Contrary, in Sottile, gypsum crystals are left to equilibrate in large excess of water, which promotes the growth of long needles at the expense of smaller crystals. Typically, such needles are several times longer than those found in a control regular plaster. For this crystal habit, the total surface of hydrophilic faces is minimized. Consequently, such plaster layers tend to repel water, which can then be used, e.g., as a substrate for oil-based panel paintings. These findings highlight the development of advanced functional materials, by tuning their microtexture, already during the premodern era.

Integration of lauric acid/zeolite/graphite as shape stabilized composite phase change material in gypsum for enhanced thermal energy storage in buildings

The effectiveness of Gypsum plaster loaded with Shape Stabilized Composite Phase Change Material (SSCPCM) in regulating indoor temperature of the building is experimentally investigated in this study. SSCPCM is composed of Gypsum/Lauric acid/Zeolite loaded with varying percentage of Graphite (0 wt%, 5 wt%, and 10 wt%). The SSCPCM-0, SSCPCM-5, and SSCPCM-10 were characterized for morphology, physical structure, chemical structure, thermal energy storage capabilities, thermal stability, and thermal conductivity using Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Fourier Transformation Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry, Thermo Gravimetric Analysis (TGA), and thermal conductivity meter respectively. The results suggest that SSCPCM have excellent surface morphology and shows good chemical, thermal and physical stability. Thermal energy storage capacity of 81.08 J/g, 74.02 J/g, and 54.30 J/g at thermal conductivity of 0.242 W/mK, 0.427 W/mK, and 0.774 W/mk were shown by SSCPCM-0, SSCPCM-5, and SSCPCM-10 respectively. Additionally, SSCPCM-5 has shown superior thermal reliability by maintaining the thermo-physical characteristics after 1000 thermal cycles. These SSCPCMs were used to prepare GPCM, GPCM-5, and GPCM-10 composite gypsum plaster and five day real outdoor testing was conducted by applying them on indoor roof and south wall of cubicles. GPCM has effectively improves the indoor temperature profile in comparison with GPCM-5 and GPCM-10.

Influence of calcination temperature on hydration behavior, strength, and weathering resistance of traditional gypsum plaster

The mineralogical composition, microstructure, and reactivity of traditional gypsum, a multiphase product, is closely connected to its calcination temperature, but systematic studies which relate those features to mechanical properties and weathering resistance of plasters are scarce. Here we examined the hydration behavior of gypsum calcined between 100 and 1000 °C, which contained varying amounts of uncalcined gypsum, bassanite, and/or anhydrite II.Detailed hydration and textural studies allowed the identification of the underlying mechanisms leading to differences in plaster performance related to (i) delayed hydration of anhydrite II along with modifications of the pore system; (ii) a filler effect exerted by anhydrite II and uncalcined gypsum; (iii) disruption of the plaster matrix by uncalcined gypsum; (iv) seeded crystallization in the presence of uncalcined gypsum and anhydrite II. Findings of this study further the understanding of traditional gypsum plaster performance and open opportunities for the development of sustainable building materials by designing optimized gypsum-based mixtures for specific application.

Properties Evaluation of Composite Materials Based on Gypsum Plaster and Posidonia Oceanica Fibers

Estimating the amount of material without significant losses at the end of hybrid casting is a problem addressed in this study. To minimize manufacturing costs and improve the accuracy of results, a correction factor (CF) was used in the formula to estimate the volume percent of the material in order to reduce material losses during the sample manufacturing stage, allowing for greater confidence between the approved blending plan and the results obtained. In this context, three material mixing schemes of different sizes and shapes (gypsum plaster, sand (0/2), gravel (2/4), and Posidonia oceanica fibers (PO)) were created to verify the efficiency of CF and more precisely study the physico-mechanical effects on the samples. The results show that the use of a CF can reduce mixing loss to almost 0%. The optimal compressive strength of the sample (S1B) with the lowest mixing loss was 7.50 MPa. Under optimal conditions, the addition of PO improves mix volume percent correction (negligible), flexural strength (5.45%), density (18%), and porosity (3.70%) compared with S1B. On the other hand, the addition of PO thermo-chemical treatment by NaOH increases the compressive strength (3.97%) compared with PO due to the removal of impurities on the fiber surface, as shown by scanning electron microscopy. We then determined the optimal mixture ratio (PO divided by a mixture of plaster, sand, and gravel), which equals 0.0321 because Tunisian gypsum contains small amounts of bassanite and calcite, as shown by the X-ray diffraction results.

Behaviour of Glass Fibre Reinforced Gypsum panels as Walls: An Update on the Recent Research Developments

The current housing shortage problem in the country, especially among the low-income groups and the necessity to address their shelter needs, led to the introduction of Glass fibre reinforced gypsum (GFRG) panels in India. These panels were originally developed in Australia in 1990 and later introduced in India, China, Hong Kong and other countries. They are light-weight, load-bearing walls used for rapid construction of affordable and eco-friendly houses (individual units to multi-storeyed buildings) and are being used in India for more than a decade. These are prefabricated in controlled-conditions in factories, from gypsum plaster reinforced with glass fibres along with certain special additives and are available in a fixed size of 12 m length, 3 m height and 124 mm thickness. The panels are hollow, with cavities of size, 230 × 94 mm, aligned along the height. These panels can resist axial, in-plane and out-of-plane loads and various studies conducted worldwide established the suitability of the panel for the construction of walls, slabs, staircases and parapet walls. GFRG buildings consist of GFRG panels as walls and slabs (without any beams and columns) and can be constructed up to 5-8 storeys in low to moderate seismic zones, and lesser height in higher seismic zones. Thus to properly understand the structural behaviour of the GFRG building system and to develop a proper design guideline, comprehensive research works were undertaken in India and other countries which includes the study to determine the various material and structural properties of the panel and this paper presents a critical review of the experimental and theoretical investigations on the structural behaviour of GFRG wall panels.

Collagen and Keratin Hydrolysates to Delay the Setting of Gypsum Plaster.

Leather and wool waste represent a high concern due to the low level of valorization and circular economy demands for upcycling of biomass resources. Both biomasses can be easily processed as protein hydrolysates and used as functional additives due to the amphiphilic and tunable properties of collagen and keratin proteins. The chemical, physical, and structural investigations of collagen and keratin hydrolysate properties showed that the chelating abilities due to carboxylic groups can be exploited for gypsum retardant additives. The molecular weights and amino acid compositions of three different hydrolysates showed only slight influences on the setting time of gypsum; all three proteins delayed the setting time of gypsum between 60 and 120 min, as compared to the commercial plaster with a 30 min setting time. Higher molecular weight and more carboxylic active groups showed slight improvements in the setting time of mortars. The improved properties of keratin hydrolysate as compared to low molecular collagen hydrolysate were attributed to foaming and conductive properties. The mechanism of mortar setting delaying through calcium ions complexation by protein hydrolysates was shown by electric conductivity evolution of plasters with and without protein additives over time, supported by foaming properties, amino acid, and functional groups' composition. Lower bending strength values for the higher concentration of proteins do not reduce the potential to use the protein hydrolysates as retardant additives in mortar fabrication.

Effect of graphene-based additives on mechanical strength and microstructure of gypsum plaster

In this study, graphene-based materials such as graphene oxide, reduced graphene oxide, and boron-doped reduced graphene oxide were synthesized, and their effects on the microstructure and mechanical properties of gypsum plaster were investigated. The graphene oxide (GO) sample was synthesized by modified Hummers’ method, and reduced graphene oxide (rGO) was obtained with the thermal reduction of GO. Boron doped reduced graphene oxide (B-rGO) was prepared via the impregnation method. The synthesized graphene-based materials were characterized using H 2 -TPR, TGA-DTA, XRD, FT-IR, SEM-EDS, TEM, Raman, and N 2 adsorption-desorption analysis. Analysis results confirmed that 450 o C was a sufficient temperature under an H 2 atmosphere to reduce GO and preserve rGO structure. XRD results revealed the presence of multilayer graphene structure in the rGO and B 2 O 3 crystals in the B-rGO sample. Multilayer graphene formation was also determined from the I 2D /I G ratio (0.1) of Raman analysis. Mechanical strength studies showed that while GO had a negative effect on both bending and compressive strength of gypsum plaster, rGO enhanced its bending and compressive strength. The addition of 0.1 wt% rGO added gypsum plaster increased the bending strength by 15.1% and compressive strength by 3.70%. SEM, He Pycnometry, and N 2 adsorption-desorption analyses revealed that rGO addition significantly changed the microstructure of gypsum plaster. The addition of B-rGO positively affected the compressive strength of the plaster and the highest increase was obtained as 8.6%; however, no significant change was observed in the microstructure of gypsum. • Electron microscopy images represented graphene nanosheets and graphene layers • X-ray diffraction results revealed the B 2 O 3 crystals in the boron-doped sample • Reduced graphene oxide increased the bending and compressive strength • Boron doped reduced graphene oxide enhanced the compressive strength • Reduced graphene oxide decreased the porosity of the gypsum

The Victoria and Albert Museum Plaster Casts by the Nineteenth-Century Workshops of the Notre-Dame Cathedral: Scientific Analysis and Conservation

Four nineteenth-century casts of the decoration on the north side of the exterior of the apse of the Notre-Dame Cathedral in Paris are held in the plaster casts collection at the Victoria and Albert Museum in London. The casts were manufactured by two different nineteenth-century workshops, one run by Jean Pouzadoux and the other by Auguste Malzieux. After an assessment of the condition of the casts, a scientific analysis allowed the characterization of the manufacturing materials and subsequent conservation treatments aimed at ensuring the stability of the casts and removing dirt and grime from the casts’ surfaces. Optical microscopy of the samples taken from the casts allowed the stratigraphy to be studied, which largely consisted of gypsum plaster and a coating layer (oxidized diterpenic resin or shellac) containing silicon and aluminium partially diffused in the porous substrate. These materials were identified by a range of techniques, including X-ray diffraction, scanning electron microscope–energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and gas chromatography/mass spectrometry. The conservation works returned stability to the panels for redisplay in the galleries and achieved a closer comparative study between the two workshops. The two sets of panels showed numerous differences in manufacturing processes that corresponded to their observed deterioration.

Assessment of the Properties of Giant Reed Particleboards Agglomerated with Gypsum Plaster and Starch.

This paper analyzes the properties of composite particleboards made from a mix of giant reed with gypsum plaster and starch as binders. Experimental boards were manufactured with a 10:2 weight ratio of giant reed/gypsum plaster particles and different amounts of starch. Giant reed particles used were ≤0.25 mm. The mix was pressed at a temperature of 110 °C with a pressure of 2.6 MPa for 1, 2, and 3 h. The results showed that the boards manufactured with longer times in the press and with 10 wt.% starch achieved the best physical and mechanical properties, obtaining a modulus of rupture (MOR) of 17.5 N/mm2, a modulus of elasticity (MOE) of 3196 N/mm2, and an internal bounding strength (IB) of 0.62 N/mm2. Thickness swelling (TS) at 24 h of the panels was reduced from 36.16% to 28.37% when 10 wt.% starch was added. These results showed that giant reed-gypsum-starch particleboards can be manufactured with physical and mechanical properties that comply with European standards for use in building construction.

Microstructure characterizations, thermal analysis, and compression stress–strain behavior of lime-based plaster

• The impact of the water/cement ratio on the compressive strength of lime-based plaster is quantified. • A difference-based method for constructing target compressive strength is proposed. • Models of use to improve the prediction accuracy of the strength of lime-based plaster learning are proposed. • The stress–strain behavior of the cement models is possible using of Vipulanandan p–q model. • Predicting the compressive strength of the lime-based plaster as a function of w/c and age. Classical lime-based plasters (LP) are multilayer complex systems made of different fillers and binders; the behavior of LPs is determined by their physical properties: mutual connection, contact with the substrates, and external factors. Lime plaster is set to a solid mass that is durable and relatively flexible. It is permeable and allows for moisture diffusion and evaporation. It is less affected by water and will not dry or dissolve like clay or gypsum plaster. Plasters of hydrated lime are less brittle and less prone to breakage, which do not require expansion joints. Different plasters have been used in construction industries, such as cement, lime, mud, stucco, and gypsum plasters. Lime-based plaster (LP) is used as building insulation materials (Bims) against environmental impacts. Lime plaster is made of sand, water, and lime, usually non-hydraulic hydrated lime (also known as slaked lime, high calcium lime, or air lime). Ancient lime plaster often contained horse hair for reinforcement and pozzolanic additives to reduce work time. Microstructure tests such as X-ray fluorescence (XRF), energy dispersive X-ray (EDX), X-ray diffraction, scanning electron microscopy, and differential scanning calorimetry were used to identify the LP. Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy, compressive strength, and modulus of elasticity. The XRF and EDX study revealed that the LP was mainly composed of SiO 2 and CaO, predominantly changed into calcium-silicate and CaCO 3 throughout the carbonation process. TGA results showed that the LP had high thermal stability up to 150 °C and 16.6 % weight loss at 1000 °C, proving the significant heat capacity of the material and fire resistance. The compressive strength of the LP with water to binder ratio (w/b) of 0.75 and 0.9 were 900 and 350 kPa at 28 days of curing, respectively. Three distinct mathematical models, including β, rational, and Vipulanandan p-q models, were proposed to predict stress–strain relationships of the LP. Based on the statistical parameters such as coefficient of determination (R 2 ), root mean square error (RMSE), and mean absolute error (MAE), the Vipulanandan p-q model was the best model for predicting the stress–strain behavior of the LP.

Monitoring Gypsum Plaster Setting in a Foam through Raman Spectroscopy

We use Raman spectroscopy to probe in situ the hydration reaction of a foamed mineral binder, here gypsum plaster. We show the strong effect of the mixing process used for foaming on the hydration kinetics. On the contrary, we observe no effect of the cationic surfactant tetradecyltrimethylammonium bromide (TTAB) used as foaming agent and of the foam structure. By tuning the hydration time scale with a setting retardant (citric acid) and measuring in parallel the characteristic bubble radius in the foam, we show that hydration kinetics control the arrest of the bubble-size evolution in the fresh foam and the final pore size in the set gypsum.

Effect of the expanded perlite dose on the fire performance of gypsum plasters

• XRD & TG show excellent fire performance of plasters containing 2.0% expanded perlite. • The IR camera show the heat transfer increases in plasters with high % of perlite. • The use of perforated lids in DSC allows quantification of gypsum and bassanite. • The plaster external side is highly affected by fire regardless the dose of perlite. Gypsum plasters are often used in buildings to provide passive protection against fire. This paper studies the fire behaviour of lightweight plasters containing moderate and high doses of expanded perlite. A propane flame was used to study the heat transmission through the plaster from the exposed side to the back side (2 cm thickness) using an IR camera. The microstructural and mineralogical variations induced by fire were analysed by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) using micro-perforated lids to improve the resolution (separation) of endothermic peaks of gypsum and bassanite. The exposed side of the plasters was drastically affected by fire regardless the concentration of perlite. However, important differences were found in the non-exposed side depending on the used amount of perlite. The greatest alteration was observed for high doses of perlite (6.5 % w/w) followed by control samples (0 % w/w). By contrast, using moderate doses of perlite (2.0 % w/w) the plasters showed excellent fire performance and CaSO 4 2H 2 O was well preserved. The results suggest that the incorporation of lightweight materials to plasters should be carefully adjusted to ensure appropriate fire protection.

Experimental Investigation of a New Design of Insulation Gypsum Plaster Blocks

Green building materials are an alternative to ordinary materialsoffering multiple environmental benefits. This study consists of an experimental investigation of a new design of gypsum plaster blocks. First, a mix design of gypsum plaster and water mixture was prepared. The optimal mix composition was determined according to the mechanical and physical properties, such as the water absorption, the temperature of hydration, the density, and the compressive strength of different gypsum plaster and water mixtures made by varying the water dosage. The second part of this investigation aims to study a new design of green blocks prepared from the optimal water and gypsum plaster mixture. The new blocks are perforated to lighten them and to reduce their thermal conductivity in order to make them moreinsulate. Experimental tests were conducted on the block prototype, such as the measurement of dimensional tolerances, compressive strength, density, flatness, water absorption, residual moisture, surface hardness, and thermal conductivity. Experimental test results show that the new blocks have very low density, and their compressive strength is sufficient for wall construction. In addition, the manufacturing process of the new blocks is very easy and very fast. Finally, the obtained physical and mechanical properties of the new gypsum plaster blocks give it the opportunity to be used for interior walls for building constructions.

Influence of polypropylene residues on the physico-mechanical and water-resistance properties of gypsum plasters

The main objective of the present research is to determine the feasibility of using polypropylene (PP) waste to produce eco-friendly gypsum-based composites. Four different replacement levels of plastic waste were selected for analysis - 2.5%, 5%, 7.5% and 10% by weight of gypsum. The first stage of the experimental campaign consisted of analysing the resulting composites based on density, mechanical performance (flexural and compressive strength) and surface hardness (Shore C). In the second stage, samples were evaluated based on their water absorption by capillary action or exposing them to continuous moisture in a wet chamber, and water resistance by subjecting them to several wetting-drying cycles. After that, scanning electron microscopy (SEM) analyses were carried out to evaluate the quality of the cohesion at the interfacial transition zone (ITZ) between the PP waste particles and the gypsum matrix. The results showed equivalent compressive strength and even a slight improvement (up to ∼9% when using 2.5% of PP waste when compared to the control material) most likely due to the greater compactness from the improved particle size distribution. In addition, a considerable reduction in water absorption and retention capacity was observed, due to the increasing incorporation of recycled PP into the gypsum matrix. The new PP-containing composites subjected to water absorption by capillary action and continuous moisture tests presented lower water absorption and adsorption capacity, wherein specimens with 10% of PP waste showed a decline of up to ∼37% when compared to the reference material. It was generally observed that the waste material can be considered as a viable partial substitute to the current commercial gypsum for the production of gypsum plasterboards.

Determining the Causes of Fluctuation in Productivity in Construction Projects

Construction projects are sophisticated in nature and require close attention and project management techniques to complete projects on time by monitoring and controlling the project resources. Productivity is one of the significant factors affecting the project life-cycle in terms of time and cost. In this study, actual productivities of construction tasks such as gypsum board, suspended ceiling, ceramic, gypsum plaster, satin plaster, paint and thermal insulation board were determined at one of the Research and Training Hospitals in Istanbul. The site records were obtained from the daily reports reported in February, March, April and May. The laborers working for the concerning tasks worked 8 hours a day. Afterwards, the actual unit man-hour data for each activity obtained from the project reports were compared with the planned man-hours and unit man-hour data provided by the Ministry of Environment and Urbanization. In the wake of the comparison of planned, actual and ministry data, the factors affecting productivity were examined and necessary suggestions were made in order to improve productivity domain in the practice

Thermoregulating gypsums by using nanoencapsulated phase change material slurry

Thermoregulating composites were produced by using a thermoregulating slurry (NPCS) containing nanoencapsulated phase change material (NPCM) from poly(styrene-co-divinylbenzene) as shell and the commercial paraffin Rubitherm®RT27 as core material. These composites were synthesized by using the constitutive water of the slurry as setting water and changing the NPCM/Hemihydrate (NPCM/Hem) mass ratio within 0.0–0.41. It was found that nanoparticles were uniformly dispersed into the gypsum, and the gypsum crystal morphology was tuned by the addition of the slurry. Attending to the thermal properties, these materials can work either as insulating or thermal energy storage materials, decreasing the thermal conductivity up to ~ 50%, whereas the thermal energy storage (TES) capacity is enlarged in a ~ 140%, respect to the pure gypsum, when the maximum NPCM/Hem mass ratio was used. This composite had a latent heat of 30.2 J g−1 and a heat capacity of equivalent 3.5 J g−1 K−1. Composites from a NPCM/Hem mass ratio up to 0.15 satisfied European mechanical standard EN 13,279–1 for gypsum binders and gypsum plasters and all of them, presented a bulk density higher than 0.60 g cm−3. The addition of a 41% in mass of nanocapsules allowed to save 13.5 kWh m−3 and, reducing the CO2 emissions up to 3.4 kg of CO2 per operating cycle. The use of this new material would lead to significant energy and economic savings, as well as a considerable reduction in the emission of polluting gases into the atmosphere.

Study some Mechanical and Thermal Properties of reinforced Perlite Concrete

Expanded perlite as an aggregate in concrete may make insulating concrete and fire-resistant suitable for roof decks and other purposes. Expanded perlite aggregate (EPA) may be used with gypsum plasters and Portland cement to protect columns, beams, and external applications. Other building uses are chimney linings, under-floor insulation, ceiling tiles, gypsum boards, and roof insulation boards. The primary goal of this research is to learn more about the effects of employing perlite aggregate (EPA) as a partial or complete substitute for sand on various characteristics of expanded perlite concrete (EPC) at 7 and 28 days. Air-dry density, compressive strength, water absorption, flexural strength, and thermal conductivity are all investigated in this research. EPA replacement by volume of sand was used to create five EPC mixes with 0%, 25 %, 50 %, %, and 100%. The effects of introducing 0.5% polypropylene fiber on the characteristics of EPC mixes were investigated. To increase the EPC workability, superplasticizer was utilized, particularly at the higher EPA replacement levels. The test outcomes reveal that the measured mechanical and physical properties of EPC decrease when increasing the EPA content. Thermal insulation of EPC increases with increasing the percentage of perlite aggregate replacement. In addition, using polypropylene fibers in the EPC specimens cause a slight reduction in density, compressive strength, and thermal conductivity compared to unreinforced specimens. Polypropylene fibers significantly increase in modulus of rupture reach 29% at 28 days, and increase in water absorption compared with unreinforced specimens.

Raman and ATR-FTIR analyses of medieval wall paintings from al-Qarawiyyin in Fez (Morocco)

A multi-analytical study has been undertaken to characterise wall paintings from the al-Qarawiyyin university in Fez, dating back to the 9th century and still in activity, with the aim of identifying the pigments used and going back to the painting techniques adopted by the Moroccan craftsmen of the time. The investigation crossed Raman and ATR-FTIR structural analyses along with XRF elemental ones, as well as colorimetric measurements. The colours and shades of six representative fragments collected during a recent excavation have been examined. Hence, red ochre (mainly hematite) was used to obtain brown-red colour, calcite for white, bistre for carbon-based black, while blue shades were achieved using azurite. Mixtures of pigments were created to widen the colour palette: cinnabar, minium and hematite were identified in orange hues while lapis lazuli and azurite were observed in grey-blue areas. The exploration of mortar layers revealed gypsum, gypsum/calcite and calcite type plasters. Furthermore, the observation of the morphological aspect of the interface between the plaster and the painting layer seems indicating that the lime-secco-painting skill had been the adopted painting technique.