Assessment of Wall Salinity in the Selection of Renovation Plaster Systems

This article presents issues related to assessing the degree of wall salinity to select plaster systems for renovations of damp building walls. The most commonly used salt concentration tests pose many difficulties. If used uncritically, they risk failing to select the right system or its incorrect make. The accuracy of the colorimetric method for testing chloride, nitrate, and sulphate content was analysed to exemplify the magnitude of the problem. Both multi-salt solutions of known concentrations and unknown composition extracted from drillings in the walls of a historical facility were examined. A comparative methodology using ion chromatography as a standard was employed in the research. The analytical methods and the selected modules of the „Statistica” software were used to analyse data and present the results. The colorimetric method has been shown to distort salt concentration values, posing a risk of unsuccessful repair work on high-salinity walls. A method for determining the correction reducing the measurement error has been proposed. The factors affecting the error were also mentioned. Attention has also been drawn to the resolution and application of a method with a correct concentration range intended to improve work efficiency and optimize the costs incurred in renovating the salty wall.

Characteristics of Semi-Refined Carrageenan From Kappaphycus Seaweed Farmed in Coastal Waters of Northern Java, Indonesia

Kappaphycus seaweed is the primary source of carrageenan, a polysaccharide widely utilised as a thickening and gelling agent in many commercial products. Unlike pure refined carrageenans, semi-refined carrageenans (SRC) are considered more cost-efficient and easier to produce. This study evaluates the quality of SRC extracted from Kappaphycus alvarezii (Doty) Doty ex Silva 1996, and Kappaphycus striatus (F. Schmitz) Doty ex P.C. Silva 1996, seaweeds farmed in the northern part of Java Island, particularly in Serang, Seribu Islands, and Karimunjawa Islands. Using 8 % KOH as a solvent, SRC was extracted from clean dried seaweed. Physical and chemical characteristics of the SRC were measured by assessing the percentage SRC yield, ash content, moisture, sulphate content, viscosity (cp) and gel strength (g.cm-2). Pearson’s correlation analysis was performed to investigate the relationship between SRC quality and environmental factors. Fourier transform infrared spectroscopy (FTIR) analysis showed that all samples had kappa-carrageenan from peak absorbance of 1218–1224 cm-1 indicating ester sulphate bonds, 924–925 cm-1 indicating 3,6–anhydrogalactose, and 843–844 cm-1 suggesting galactose–4–sulphate groups. Furthermore, ash content, moisture, and viscosity of SRC passed the FAO standard, while the sulphate content was below the threshold limit. Several environmental factors had a significant correlation with SRC quality, such as water pH positively correlated with gel strength, salinity level positively correlated with gel strength, and depth positively correlated with ash content. This study concluded that SRC produced from the sampling sites had varying qualities and may be affected by environmental parameters in their cultivation site.

Mechanism of Post-Radiation-Chemical Graft Polymerization of Styrene in Polyethylene

Structural and morphological features of graft polystyrene (PS) and polyethylene (PE) copolymers produced by post-radiation chemical polymerization have been investigated by methods of X-ray microanalysis, electron microscopy, DSC and wetting angles measurement. The studied samples differed in the degree of graft, iron(II) sulphate content, sizes of PE films and distribution of graft polymer over the polyolefin cross section. It is shown that in all cases sample surfaces are enriched with PS. As the content of graft PS increases, its concentration increases both in the volume and on the surface of the samples. The distinctive feature of the post-radiation graft polymerization is the stepped curves of graft polymer distribution along the matrix cross section. A probable reason for such evolution of the distribution profiles is related to both the distribution of peroxide groups throughout the sample thickness and to the change in the monomer and iron(II) salt diffusion coefficients in the graft polyolefin layer. According to the results of electron microscope investigations and copolymer wettability during graft polymerization, a heterogeneous system is formed both in the sample volume and in the surface layer. It is shown that the melting point, glass transition temperature and degree of crystallinity of the copolymer decreases with the increasing proportion of graft PS. It is suggested that during graft polymerization a process of PE crystallite decomposition (melting) and enrichment of the amorphous phase of graft polymer by fragments of PE macromolecules occurs spontaneously. The driving force of this process is the osmotic pressure exerted by the phase network of crystallites on the growing phase of the graft PS.

Appraising Mahallat Geothermal Region using thermal surveying data accompanied by the geological, geochemical and gravity analyses

Mahallat Geothermal Region, located in the central part of Iran, is known as one of the largest low-temperature geothermal fields. In this study, Mahallat geothermal resource has been evaluated based on integrated geological, geochemical and geophysical analyses. Gravity data revealed three major negative anomaly zones. Based on the geochemical analyses, quartz geothermometers are more reliable than others and confirmed that the reservoir is about 90 °C. Lithological properties of Jurassic layers and high sulphate content observed in geochemical data showed traces of the coal-rich layers on the hot fluids. Measured temperatures in 7 boreholes with the depths ranging from 50 to 100 m, have proposed that expected geothermal gradient will be about 81.5 °C/km. Among all drilled boreholes, the data coming from only one resulted in this almost reliable gradient. Other boreholes are clearly too shallow or affected by upflow or downflow of water along existing faults. Geological, geochemical, gravity and measurements of drilled boreholes suggested the existence of a shallow reservoir with an approximate temperature of 90 °C. Regarding gravity and observed faults, geothermal reservoir is elongated parallel to one of the main faults of the region with NE-SW strike.

Role of supplementary cementing materials on reducing damage due to internal sulphate attack in concrete

The effect of supplementary cementing materials (SCM) on internal sulphate attack in mortars was evaluated. Different types and levels of SCM were investigated where a mixture of hemihydrate and calcium carbonate fillers were used in the mixtures as a source of sulphate and carbonate, respectively. In addition, mixtures containing aggregates with high sulphate content were also examined to understand the role of sulphate from aggregate on the expansion. It has been found that the internal sulphate attack can be reduced through the use of SCM with high reactive alumina such as Metakaolin. It was hypothesised that the beneficial effect of Metakaolin lies in its ability to reduce ion mobility within the matrix, and perhaps raise the alumina/sulphur in the system favoring the formation of non-expansive monosulphoaluminate. However, at high levels of sulphate, none of the SCM provided successful protection against internal sulphate attack.

Studies on the fresh properties an durability of unshrinkable fill containing recycled concrete aggregate or natural aggregates of marginal quality

The intention of this research is to explore the feasibility of incorporating aggregates of low or marginal quality, such as Recycled Concrete Aggregate (RCA) and aggregate with high sulphate content, in U-fill mixtures. It has been determined that where RCA is used, water dissipation may be hindered due to the increase in fines caused by abrasion, hence causing an increase in hardening time. To reduce this effect, addition of natural aggregates may be necessary. Moreover, through a series of investigation it has been found that high percentages of sulphate may cause severe damage due to Ettringite and Thaumasite formation; however by incorporation of supplementary materials such as slag the deleterious effects of internal sulphate attack can be reduced. The effects of using Na2SO4 and gypsum in the presence of slag have also been investigated. Results indicated that due to the lower available calcium content within bars containing Na2SO4 expansion rate is low.

Studies on the fresh properties an durability of unshrinkable fill containing recycled concrete aggregate or natural aggregates of marginal quality

The intention of this research is to explore the feasibility of incorporating aggregates of low or marginal quality, such as Recycled Concrete Aggregate (RCA) and aggregate with high sulphate content, in U-fill mixtures. It has been determined that where RCA is used, water dissipation may be hindered due to the increase in fines caused by abrasion, hence causing an increase in hardening time. To reduce this effect, addition of natural aggregates may be necessary. Moreover, through a series of investigation it has been found that high percentages of sulphate may cause severe damage due to Ettringite and Thaumasite formation; however by incorporation of supplementary materials such as slag the deleterious effects of internal sulphate attack can be reduced. The effects of using Na2SO4 and gypsum in the presence of slag have also been investigated. Results indicated that due to the lower available calcium content within bars containing Na2SO4 expansion rate is low.

Role of supplementary cementing materials on reducing damage due to internal sulphate attack in concrete

The effect of supplementary cementing materials (SCM) on internal sulphate attack in mortars was evaluated. Different types and levels of SCM were investigated where a mixture of hemihydrate and calcium carbonate fillers were used in the mixtures as a source of sulphate and carbonate, respectively. In addition, mixtures containing aggregates with high sulphate content were also examined to understand the role of sulphate from aggregate on the expansion. It has been found that the internal sulphate attack can be reduced through the use of SCM with high reactive alumina such as Metakaolin. It was hypothesised that the beneficial effect of Metakaolin lies in its ability to reduce ion mobility within the matrix, and perhaps raise the alumina/sulphur in the system favoring the formation of non-expansive monosulphoaluminate. However, at high levels of sulphate, none of the SCM provided successful protection against internal sulphate attack.

Rare Occurrence of Mirabilite in the Thirteenth-Century Historic Salt Mine in Bochnia (Poland): Characterisation, Preservation, and Geotourism

The small stalactites found on the ceiling at level I near the Sutoris shaft in the thirteenth-century historic salt mine in Bochnia, Poland, are mainly composed of mirabilite (Na2SO4·10H2O) followed by blödite (Na2Mg(SO4)2·4H2O). The unique presence of these two minerals in only one location in this old underground mine is attributed to contemporary precipitation from percolating solutions. This can be caused by a combination of at least two factors: a specific and stable microclimate (characterised by a low temperature, high humidity, and relatively strong air circulation which accelerates the processes of evaporation and crystallisation) and the specific chemical composition of the leaking solution (contains a low carbonate and high sulphate content, and characterised by acidic pH (4.8) and intermediate-mineralisation (174,308 mg/L)). The microclimate specified above can be linked to the long distance from the ventilation shaft that pumps the air from the surface to the mine, while the composition of the leaking solution as well as the hydrochemical modelling results obtained with PHREEQC can be directly related to the top anhydrite layer and the overlying secondary cap consisting mainly of claystone, anhydrite, and gypsum. In this study, the challenges underlying the preservation of mirabilite in the underground environment of the salt mine are discussed, in terms of both nature and mining law. Based on the results of detailed geological, mineralogical, and chemical research, appropriate solutions that can be practically applied for the management, preservation, and protection of the mirabilite efflorescence are proposed. The presence of this intriguing mineral, with appropriate protection, can be another geological attraction for tourists visiting this thirteenth-century UNESCO-recognised salt mine.

Effect of locally sourced Nigerian gypsum on the strength and microstructure of Portland cement mortar

The objective of this study was to investigate the suitability of Nigerian, sourced Gypsum for the manufacture of Portland cement. Gypsum samples were obtained from eighteen deposits across Nigeria. These were classified into five purity groups based on their calcium sulphate content.Foreign Gypsum, imported from Morocco, was used as control. Six cement samples where produced for each of the five Gypsum purity groups by grounding and blending cement clinker with 3%, 4%, 5%, 6% and 7% Gypsum content. The group 1 cement mix (having not more than 65% calcium sulphate content) has displayed flash set and could not be moulded and therefore not used for further analysis. Cement mortar prisms were produced for the groups 2, 3, 4 and 5 cement mixes, and subjected to flexural and compressive strength tests at 7, 14, 21 and 28 day curing periods. The cement mortar prisms were also subjected microstructure analysis at 7 and 28 days curing period. The spongy, gel and whitish colouration observed from the microstructure of the specimens indicated silicates enriched regions which have proven the strength increase from 7 to 28 day curing period. The optimum gypsum content of 5.5% was recommended. The results show that all but the class one gypsum with less than 65% purity content are suitable for cement manufacture. Keywords: Gypsum, clinker, mortar, microstructure, compressive strength, flexural strength