Volcanic Scoria Research Articles

Phase Evolution, Mechanical, and Electrical Properties of Lightweight Ceramic Prepared Using Scoria at Low Temperature

This study aimed to produce lightweight, eco-friendly ceramic materials with superior properties using natural raw materials and low processing temperatures. Five ceramic samples were fabricated using red clay and varying contents of volcanic scoria (10%, 20%, 30%, 40%, and 50%) through sintering at 950 °C for 4 h. The crystalline phases, electrical properties, porosity, and mechanical strength of all the ceramic specimens were comprehensively evaluated. It was determined that the chemical composition of the raw materials and the resulting phases significantly influenced these various attributes. The XRD analysis revealed that the ceramic samples primarily consisted of the crystalline phases gehlenite, low quartz, and anorthite, along with the minor wollastonite and hematite phases. As the scoria content was increased, the MgO and Fe2O3 concentrations also increased, leading to a reduction in dielectric constant, dielectric loss, and electric conductivity. Moreover, the porosity of samples decreases from S10 to S50 due to the increase in the percentage of scoria and this reduction in porosity led to increased bending strength. The findings of this study suggest that volcanic scoria can serve as a viable eco-friendly raw material to produce lightweight ceramics with excellent electrical and mechanical properties, presenting cost-effective and energy-efficient solutions for various applications.

Effects of Mix Components on Fracture Properties of Seawater Volcanic Scoria Aggregate Concrete.

The fracture mechanism and macro-properties of SVSAC were studied using a novel test system combined with numerical simulations, which included three-point bending beam tests, the digital image correlation (DIC) technique, scanning electron microscopy (SEM), and ABAQUS analyses. In total, 9 groups and 36 specimens were fabricated by considering two critical parameters: initial notch-to-depth ratios (a0/h) and concrete mix components (seawater and volcanic scoria coarse aggregate (VSCA)). Changes in fracture parameters, such as the load-crack mouth opening displacement curve (P-CMOD), load-crack tip opening displacement curve (P-CTOD), and fracture energy (Gf), were obtained. The typical double-K fracture parameters (i.e., initial fracture toughness (KICini) and unstable fracture toughness (KICun)) and tension-softening (σ-CTOD) curve were analyzed. The test results showed that the initial cracking load (Pini), Gf, and characteristic length (Lch) of the SVSAC increased with decreasing a0/h. Compared with the ordinary concrete (OC) specimen, the P-CMOD and P-CTOD curves of the specimen changed after using seawater and VSCA. The evolution of the crack propagation length was obtained through the DIC technique, indicating cracks appeared earlier and the fracture properties of specimen decreased after using VSCA. Generally, the KICun and KICini of SVSAC were 36.17% and 8.55% lower than those of the OC specimen, respectively, whereas the effects of a0/h were negligible. The reductions in Pini, Gf, and Lch of the specimen using VSCA were 10.94%, 32.66%, and 60.39%, respectively; however, seawater efficiently decreased the negative effect of VSCA on the fracture before the cracking width approached 0.1 mm. Furthermore, the effects of specimen characteristics on the fracture mechanism were also studied through numerical simulations, indicating the size of the beam changed the fracture toughness. Finally, theoretical models of the double-K fracture toughness and the σ-CTOD relations were proposed, which could prompt their application in marine structures.

Resistance to magnesium sulphate attack of binary and ternary cementless self-compacting alkali-activated mortar

The aim of this study is to investigate the effect of sulphate on self-compacting alkali-activated mortars (SCAAMs) produced using volcanic scoria (V), boron waste (B) and granulated blast furnace slag (G) together with alkali activators. Thus, the production of cement-free alkali-active mortar by recycling waste and reducing the CO2 effect increases the importance of this study. The fact that the waste material is provided free of charge and that V is readily available from nature provides economic advantages in the production of these mortars. In this experimental study, magnesium sulphate solution was utilized to define the sulphate resistance of SCAAMs. In binary SCAAMs, B was used with G in a ratio of NS:NH = 3.0, with an increase from 5 % to 15 %; in ternary mixtures, B was used together with G and V in the same proportions, in a ratio of NS:NH = 1.0. The tests involved immersion in 5 % magnesium sulphate solution for 1, 3 and 6 months. Mass development, compressive strength, visual inspection and microstructural changes were investigated. In general, the binary SCAAMs performed better in magnesium sulphate solution than the ternary SCAAMs, except in the 6th month. Considering the samples with the highest B content, a 100 % loss of compressive strength occurred in the B15G85 sample under the influence of sulphate for 6 months, while a loss of compressive strength of about 15 % occurred in the B15G40V45 sample. The results showed that the increase in B content caused a severe deterioration of the sulphate effect in the samples over time and that the V additive had a positive effect on the sulphate resistance.

Sustainable use of boron waste and volcanic scoria in slag-based self-compacting alkali-activated mortars: Fresh, mechanical and durability properties

Sustainable self-compacting alkali-activated concrete (SCAAC) manufacturing is an environmentally friendly concrete that has a reduced carbon footprint than ordinary concrete. Alkali-activated binders have been demonstrated in experiments to reduce concrete's energy consumption and carbon emissions by over 50%. This paper focuses on manufacturing boron waste (BW), volcanic scoria (VS) and ground blast furnace slag (GBFS) incorporated binary and ternary blends of self-compacting alkali-activated mortars (SCAAM). The main objective of this study is to investigate the fresh, mechanical, durability and microstructural properties of SCAAM based on binary and ternary mixtures of BW, VS, and GBFS. SCAAM samples were synthesized at 60 °C and 100 °C for 72 h then exposed to ambient cured at 3, 28 and 90 days. The compressive strength, flexural strength, physical, and sorptivity properties of the SCAAM mixtures, as well as flowability, were investigated. The performance of the produced blends at freeze-thaw exposure were also examined. SEM, and EDS was also used to examine the microstructures of the mixtures. The findings showed that 50% GBFS and 50%VS based SCAAM mixture heat cured at 100oC activated with NS/NH ratio of 3.0 produced a compressive strength of 40 MPa at 90 days. The findings indicated that inclusion of BW to the SCAAM mixtures decreased the compressive strength notably regardless of NS/NH ratio and curing temperature. Inclusion of BW also affected the durability performance negatively.

Formulation of geopolymer binder based on volcanic-scoria and clay brick wastes using rice husk ash-NaOH activator: Fresh and hardened properties

The present study investigated the influence of the replacement of waste clay bricks (WB) by volcanic scoria (Zg) on the fresh and hardened properties of geopolymer binders for potential construction applications at ambient temperature. Geopolymer paste samples were prepared using Zg as raw material blended with WB ranging from 0 to 50 wt% of total raw materials. Alternative alkaline activator used for the geopolymer synthesis was prepared by mixing rice husk ash (RHA) and 6 mol/L of NaOH solution. The geopolymers were cured at room temperature for 28 days, then subjected to mechanical property tests; microstructural and macrostructural characterization studies. Results showed that both flowability and setting time of geopolymer mixtures decreased with increases in WB content. The reduction in workability could be attributed to increase in the relatively rough surface of WB particles, which resulted in inter-particle friction. Flexural strength increased from 4 to 12 MPa while the compressive strength 24–52 MPa with the increase in WB up to 50%. The WB powders enriched Al content in mixtures, establishing the Si-O-Al bonds, confirmed by 27Al MAS NMR spectroscopy exhibiting the more Al(IV) sites integrating the N-A-S-H network. Incorporating the WB powders contributed to the development of densified matrix.

Mechanical properties of seawater volcanic scoria aggregate concrete-filled circular GFRP and stainless steel tubes under axial compression

Abstract In this study, the properties of seawater volcanic scoria aggregate concrete (SVAC)-filled circular stainless steel (SFCST) and glass fibre-reinforced plastic (GFRP) tubes (SFCGT) were investigated. Ten groups were considered and 30 specimens were prepared, including four different parameters: the concrete type (SVAC and ordinary concrete [OC]), outer tube type (GFRP and stainless steel tubes), concrete strength (C30 and C40), and tube thickness (0, 3, and 4 mm). The typical influences of the SVAC and outer tube on the mechanical properties of specimens were then analysed. The research findings show that the strength and ductility of the SFCGT and SFCST are significantly higher than those of plain SVAC. The peak strain and strength enhancement factor of the SFCGT and SFCST increase with an increase in the tube thickness, and the concrete strength has a detrimental impact on the toughness of the specimen. Unlike in the confined OC specimens, a sudden decrease is observed in the stress–strain curves of the SFCGT and SFCST owing to the changes in the deformability of the SVAC. Generally, the strengths of the SFCGT and SFCST specimens are 10.3% lower and 4.1% higher than those of the confined OC specimens, respectively. Finally, analytical models of the strength and stress–strain curves considering the influences of the SVAC and passive confinement were established, and numerical simulations were performed to provide a basis for the practical application of the SFCGT and SFCST.

Synthesis of alkali-activated volcanic scoria and rice husk ash based composite materials for adsorptive removal of crystal violet: Optimization, kinetics, isotherms and mechanism

In this study, central composite design (CCD) was used to optimize the porosity structure of NaOH-activated volcanic scoria (VSc) and rice husk ash (RHA) composite materials. The synthesis conditions, namely VSc and RHA fractions by mass and NaOH concentration were used as the input (independent) variables and the porosity parameters, iodine index and methylene blue index, as the output variables. The optimum conditions that gave the material, CM, with the highest iodine index and methylene blue index, and hence porosity structure, were attained at 0.67 VSc (2g)/RHA (3g) ratio by mass and 5M NaOH. The CM and precursors were characterized using FTIR, SEM, pHpzc, Methyl Blue index, and Iodine index. The CM and the precursor VSc were used to sorb crystal violet (CV) dye from synthetic wastewater. The pseudo-second-order kinetic and Langmuir models best-described CV adsorption by both materials. The adsorption mechanism was controlled by Coulombic interactions. At an initial CV concentration of 20–60 mg/L, 0.1g/30 mL adsorbent dosage, and pH of 6 at 25 °C, the CM had a slightly higher (∼1.13 times) adsorption capacity (11.06 mg/g) for the uptake of crystal violet dye than the precursor VSc (9.75 mg/g) consistent with their methylene blue indices. Electrostatic interactions and ion exchange are proposed dominant adsorption mechanisms. The porosity and adsorption performance of the VSc-RHA alkali-activated materials are shown to be strongly and significantly dependent on the RHA fraction and NaOH concentration relative to VSc.

Experimental Investigation on the Utilization of Marble and Scoria Powder as Partial Replacement of Cement in Concrete Production

This paper explores how marble and scoria powder can be used as partial substitutes for ordinary Portland cement in creating C-25 concrete. Both materials contain over 50% of the major oxides found in cement, with marble high in CaO and scoria high in SiO2. Experimental investigations were conducted to study the chemical, physical, mechanical, and fresh properties of concrete containing marble and scoria powder. For the investigation, 13 different mixes, including the control mix, were used with a constant water–cement ratio of 0.5 and a slump range of 25–50 mm for concrete with a compressive strength (CS) of 25 MPa. Marble-to-scoria ratio of 2 : 1, 1 : 1, and 1 : 2 was used, and then the combined fraction of both marble waste and scoria in concrete was increased from 0% to 20% in 5% range. Including the control test specimens, a total of 117 (150 × 150 × 150 mm) concrete cubes for CS test, 39 (100 × 100 × 500 mm) concrete beam specimens for flexural strength test, 39 (100 × 200 mm) cylinder specimens for splitting tensile strength (STS) test and, 39 (100 × 100 × 100 mm) cube specimens for water absorption test were cast and tested at 3, 7, 28, and 56 days. The test results indicate that marble and volcanic scoria powders with marble-to-scoria ratio of 1 : 1 could replace cement up to 15% without compromising the CS and up to 10% without compromising the flexural and STS; also, the water absorption decreases up to 10% replacement; however, the workability of the fresh mix decreases as the combined replacement level of marble and scoria increases. Generally, a 10% replacement with marble-to-scoria ratio of 1 : 1 produces concrete with higher compressive, flexural, tensile strength, and water absorption manifestations when compared to conventional concrete.

The impact of thermal treatment on the mechanical properties and thermal insulation of building materials enhanced with two types of volcanic scoria additives

The need to substitute cement with eco-friendly building materials has increased in recent years, and attempts to enhance the mechanical and thermal insulation properties of these materials are ongoing. Therefore, the present study aims to use two different types of scoria as substitutes for cement in building materials and investigate the impact of thermal treatment on improving mechanical characteristics and thermal insulation. Black and red volcanic scoria, both before and after thermal treatment at different temperatures (600, 700, 800, and 900 °C), were utilized as cement substitutes in concrete specimens. Concrete specimens with different proportions (0–30 % wt.%) of black and red scoria were cured for different durations (14, 21, 28, and 91 days), and then tested for compressive strength. The compressive strength of specimens increased with increasing curing time, but decreased when scoria content exceeded wt.10 %. Furthermore, thermal treatment positively impacted the compressive strength of concrete specimens with red scoria, but negatively affected those with black scoria, owing to the increase in crystalline phases with increasing temperature. The specimen containing 10 % red scoria thermally treated at 900 °C and cured for 91 days yielded the highest compressive strength (60 ± 1.22 MPa). Further, the thermal insulation analysis of the concrete specimens with each type of thermally treated scoria was performed on day 28 of curing. The thermal insulation increased as the proportions of black and red scoria increased, which involved increasing the thermal treatment temperature of both scoria from room temperature to 900 °C on day 28 of curing. Additionally, the thermal insulation of concrete specimens treated with red scoria was more optimized than that of concrete treated with black scoria, particularly at high thermal treatment temperatures, and more than seven times as much as that of ordinary concrete. The lowest thermal conductivity value of the specimen was 0.157 ± 0.01 W m−1 K−1. Based on the findings, concrete with thermally treated red scoria is a suitable eco-friendly building material with high compressive strength and efficient thermal insulation properties.

Meat Quality Changes in Aged Pork Loin using Jeju Volcanic Scoria Earthenware.

This study aimed to investigate changes in the quality of meat aged using Jeju scoria earthenware. Water-holding properties, pH, color, tenderization, fatty acid composition, and free amino acid characteristics of aged pork loin were evaluated to determine the effects of wet and dry (normal and Jeju Scoria) aging methods and aging time (0, 10, 20, 30, and 40 days) on meat quality. The aging methods altered pH and CIE L* after 10 days of aging. However, the aging method did not alter the pH and CIE L* of the aged pork loin after 10 days of aging. The shear force was significantly lower in the Scoria aging method than in the wet aging method after 10 and 20 days of aging. Both the normal and Scoria aging methods increased aging loss compared to the wet aging method, which could be attributed to longer air exposure times of the two non-packaged aging methods than in the packaged aging method. The scoria aging method had significantly higher contents and ratios of saturated (SFA) to mono-unsaturated fatty acids but lower ratios of poly-unsaturated fatty acids to SFA than the wet aging method. The content of most free amino acids significantly increased with aging time, especially those related to the sweet, and umami categories. In summary, this study suggests that the Scoria aging method provides positive aspects of eating quality, such as improvement of meat tenderness and taste, including umami, with minimum changes in the overall meat quality.

Napoliite, Pb2OFCl, a new mineral from Vesuvius volcano, and its relationship with dimorphous rumseyite

AbstractNapoliite, ideally Pb2OFCl, is a new fluoroxychloride mineral found in a specimen from a fumarole formed subsequent to the 1944 eruption of Vesuvius volcano, Naples Province, Italy. It occurs as well-shaped lamellar crystals up to 0.25 × 0.25 × 0.01 mm typically forming clusters up to 0.4 × 0.4 mm on the surface of volcanic scoria in association with anglesite, artroeite, atacamite, calcioaravaipaite, cerussite, challacolloite, cotunnite, hephaistosite, manuelarossiite, matlockite and susannite. Napoliite is colourless with white streak and adamantine lustre. It is brittle and has a laminated fracture. Cleavage is perfect on {001}. Dcalc = 7.797 g cm–3. The calculated mean refractive index is 2.10. Chemical composition (wt.%, electron microprobe) is: PbO 91.71, F 3.89, Cl 7.34, –O=(F+Cl) –3.30, total 99.64. The empirical formula calculated on the basis of 3 anions is Pb1.999O0.997F0.996Cl1.007. Raman spectroscopy confirms the absence of OH– groups and H2O molecules in the mineral. Napoliite is tetragonal, space group P42/mcm, a = 5.7418(11), c = 12.524(4) Å, V = 412.9(2) Å3 and Z = 4. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (hkl)] are: 3.860 (85) (111); 3.139 (20) (004); 2.914 (100) (113); 2.866 (63) (200); 2.118 (19) (204); 2.027 (19) (220); 1.665 (20) (313); and 1.642 (23) (117). The crystal structure was refined to R1 = 0.024 for 222 reflections with F > 4σ(F). It is based on lead oxide blocks derived from that of litharge PbO, which alternate with layers of chloride ions. Napoliite represents a new structure type with a unique order/disorder pattern of fluorine and oxygen atoms. The new mineral is dimorphous with rumseyite. It is named after the city of Naples (Napoli in Italian).

Potential Use of Scoria as a Cementitious Material for Green Concrete Production

The demand for cement, which is one of the key components of concrete, is high in Ethiopia, but it is the most expensive and environmentally unfriendly construction material. Due to the increasing concerns about the environment worldwide, researchers have started looking for other resources that can be used to reduce the pollution caused by the cement industry. One of the most effective ways to reduce the pollution caused by the cement industry is by using volcanic scoria powder as a partial replacement for cement in concrete production. Scoria is a locally available natural volcanic material in Ethiopia, especially around the rift valley regions. This natural resource can also be used to reduce energy consumption and the cost of production of cement. To investigate this study, nonprobability sampling techniques were adopted to collect samples from the study area. A differing proportion of scoria powder was considered as a partial replacement of cement after analyzing its characteristics, and its effect on the fresh and mechanical properties of hardened concrete was examined. The test results on the characteristics of scoria revealed that the material is suitable to be used as a supplementary cementitious material in concrete production; hence, its main constituents SiO2 + Al2O3 + Fe2O3 are higher than 70% as per ASTM C618. As the content of scoria powder replacement in cement is increased, it reduces the slump of freshly mixed concrete properties. The hardened concrete specimens made with 10%, 20%, and 30% partial replacement of cement with scoria achieved the specified minimum strength after 28 days of curing time. But concrete specimens made with 40% scoria content do not satisfy the minimum specified concrete strength even after 90 days. The significant strength achievement in scoria blended concrete specimens occurred when moving from 56 to 90 days of curing with 10% replacements. However, in reference specimens, this was observed during 28 days of curing times. The findings of this investigation revealed that scoria powder could replace cement by 30% for the production of normal concrete and it also has the potential to protect the environment from carbon dioxide emissions. These findings satisfy the basic strategy of green concrete production in worldwide.

Thermal behaviour, microstructural changes and mechanical properties of alkali-activated volcanic scoria-fired waste clay brick blends

The present work aims at producing volcanic scoria (Zg) based geopolymer containing high volume of waste fired clay brick (WB). The objective was producing Zg-based geopolymer incorporating WB powders up to 50 wt% and then investigated a potential thermal stability. All formulated samples were prepared with sodium silicate made from rice husk ash and 6 M of an aqueous NaOH solution. The first series of consolidated geopolymer samples were cured at 25 °C, while the second ones were exposed to high temperatures of 400, 600 and 800 °C. The specimens were subjected to mechanical performance, physicochemical and microstructural properties evaluation. The results indicated that incorporating the WB positively influenced the physicochemical performances of geopolymers. Sample prepared with 10 wt% of WB gave highest mechanical property (33 MPa) at 600 °C. The use of WB favoured the densification and strength development of end products in the range of 25–600 °C.

Development of energy-efficient hollow concrete blocks using perlite, vermiculite, volcanic scoria, and expanded polystyrene

Sustainable development programs focus on reducing traditional energy usage and finding alternative energy sources. Thermal insulation materials can improve energy efficiency and reduce negative environmental impact, and be cost-effective by using low density, strong heat resistance, good thermal conductivity, and durability. Consequently, a novel arrangement of hollow concrete blocks was manufactured on-site in this research. In order to assess the commercial viability of these hollow concrete blocks, four distinct variants (perlite, vermiculite, scoria, and polystyrene) were investigated. Economic viability, fuel energy use, and CO2 emissions were also assessed using experimentally obtained thermal resistance. All the newly produced blocks have fulfilled the compressive strength and absorption criteria set by the standards for non-load-bearing blocks. The perlite and scoria blocks, with their respective lowest dry density of 1544 and 1673 kg/m3, qualified as lightweight concrete blocks. As a result, their thermal conductivity was over 60% lower than that of the commercially made blocks. In addition, the scoria block proved to be the most cost-effective option. When compared to a normal market block, the best scoria wall may enhance the heat resistance by 144%. In terms of the net present value (NPV) for 40 years, this solution cut energy consumption from 272 to 109 $/m2 (about a 150 % reduction). As an additional benefit, constructing a wall out of scoria blocks resulted in a 2.4 and 1.15-fold decrease in CO2 emissions compared to conventional and control blocks. Furthermore, this study emphasizes the potential environmental benefits, such as saving natural resources, energy, and money by using these by-products to make greener concrete masonry units.

Postfire residual capacity of steel fiber reinforced volcanic scoria concrete using PSO-BPNN machine learning

Volcanic scoria (VS) is a potential green aggregate, as it is abundant around the world. Replacing normal aggregate with vS aggregate improves economic efficiency, ecological benefits in the construction industry. In this study, an artificial neural network (ANN) is employed to predict the behavior of steel fiber reinforced volcanic scoria concrete (SFVSC). Compression strength (CS) and tensile splitting strength (STS) tests on SFVSC was first conducted to obtain 240 groups of training data. Based on the training data, appropriate neural network structures and training processes was established using several neural network models. The behavior of steel fiber volcanic scoria concrete is predicted with various parameters. The prediction accuracy of is appraised using the mean absolute percentage error (MAPE), root mean square error (RMSE), and correlation coefficient (R2) for different machine learning algorithm back propagation neural network (BPNN), genetic algorithm (GA-BPNN), and particle swarm optimization (PSO-BPNN). The main conclusion is that the PSO-BPNN model outperforms the other models in prediction accuracy. The other results show that both GA-BPNN and PSO-BPNN exhibit good accuracy and suitable in predicting the mechanical properties of SFVSC. Using machine learning, the effect of different vS aggregate replacement levels (VR) (30, 50, 70 %), steel fiber dosage (Vst) (0, 0.5, 1, 1.5 %), water-to-cement ratios (w/b) (0.4, 0.5), and temperatures (t) (20, 200, 400, 600, 800 °C) on the mechanical properties of SFVSC is also studied.

EFFECT OF SUBSTRATES AND FERTIGATION ON GROWTH AND PHOTOSYNTHETIC EFFICIENCY OF MAGUEY PULQUERO PLANTS OF MEZQUITAL VALLEY LANDRACES

Maguey pulquero (Agave spp.) seedling cultivation is an emerging alternative capable of supply the demand of its diverse products. This research aimed to evaluate the growth and maximum quantum yield of Photosystem II (Fv/Fm) of three landraces of maguey pulquero young plants (10 months-old) germinated from seeds, growing under greenhouse within interaction effect of four substrates and four concentration levels of nutrient solution. The hypothesis was that phenotypic variation of young maguey pulquero landraces growing under greenhouse conditions could help to identify genotypes ideal for commercial production and to elucidate its nutrient and substrate requirements. The variables evaluated were: Fv/Fm, number of leaves, length and width (cm) of biggest leaf, and plant dry biomass (g), the results were analyzed by a two-way ANOVA and means comparison by Tukey’s test. The results demonstrated that Penca larga landrace (Agave mapisaga Trel.) had the highest values in all the growth variables evaluated compared to Manso and Xamini landraces (both A. salmiana Otto ex Salm-Dyck). Penca larga exhibited similar growth in the substrate agricultural soil and volcanic scoria mixture (SVM), and substrate agricultural soil alone (S) regardless of the nutrient solution concentration used, while both A. salmiana landraces exhibited total biomass reduction in the maximum nutrient concentration added in the S substrate (S+L4 treatment) compared to their respective effect on SVM substrate without nutrient addition (SVM+L1 treatment). All landraces exhibited growth inhibition in the commercial substrate mixture (CSM) and volcanic scoria alone (VS) without nutrient addition (CSM+L1 and VS+L1), while growth increase of all landraces in those substrates was relative to the increasing nutrient concentration. Photoinhibition was observed in all landraces in the treatment VS+L1. The growth variations observed across the landraces were helpful to identify potential genotypes ideal for commercial production and to set adequate substrates and nutrient requirements for agave cultivation,

Leaf area and its impact in yield and quality of greenhouse tomato (Solanum lycopersicum L.)

This study aimed to estimate the tomato leaf area index (LAI) by comparing two methods (destructive and interception of photosynthetically active radiation) and the consequent relationship to fruit yield and quality. The experiment was carried out in a greenhouse with tezontle (red volcanic scoria) as the substrate and a drip irrigation system. The experiment consisted of three treatments: T1, T2 and T3, with one, two and three stems per plant, respectively. The LAI was measured with a ceptometer that estimates the intercepted radiation above and below the canopy. Maximum LAI was found at 1413 cumulative growing degree days (CGDD). Those indexes were 3.69, 5.27 and 6.16 for T1, T2 and T3, respectively. Individual correlation models were fitted linearly between the two methods. The R2 values were 0.98, 0.99 and 0.99 with yields of 20, 18 and 17 kg m-2 for T1, T2 and T3, respectively. In addition, T1 produced better fruit size quality with approximately 69, 23 and 8% classified as first, second and third class, respectively. Only 1% was classified as a small fruit. Increasing the number of stems per plant increased the LAI and fruit number but decreased fruit size. Highlights: The leaf area index (LAI) is a very important variable for growth and development of crops. The ceptometer proved to be a fast, useful and statistically reliable method to estimate LAI. The increase of photosynthetically active radiation favors the photosynthetic efficiency per unit area. The number of stems per plant increase the LAI, dry matter accumulation, plant height and the number of fruits. However, the size of fruit decreases.

The viability of calcined clays and volcanic scoria from western Cameroon as Supplementary Cementitious Material (SCM)

The viability of calcined clays and volcanic scoria from western Cameroon as Supplementary Cementitious Material (SCM)

Effect of various amounts of aluminium oxy‐hydroxide coupled with thermal treatment on the performance of alkali‐activated metakaolin and volcanic scoria

This study aims to improve the stability of alkali-activated products, such as powdered volcanic scoria and metakaolin, by thermal treatment in addition to their partial replacement with aluminium oxy-hydroxide. To this effect, mixtures obtained from a partial replacement of aluminosilicate sources (volcanic scoria or metakaolin) with respectively 0, 10, 20 or 30 % of mass of aluminium oxy-hydroxide were alkali-activated and stored for 28 days at room temperature in the laboratory. The various specimens obtained were heated at 900–1200 °C and both the alkali-aluminosilicates and the heated products were analysed. It appeared that aluminium oxy-hydroxide improves the stability of heated products. Thus, without replacement, alkali-activated specimens of metakaolin showed cracks at 1100 °C while those of volcanic scoria melted at 1150 °C. Conversely, heated alkali-activated specimens of either volcanic scoria or metakaolin with the replacement showed stability up to 1200 °C and an improvement in the residual compressive strength as from 900 °C. Indeed, at 1150 °C, the metakaolin-based geopolymers or the alkali-activated volcanic scoria with 30 % of mass of the replacement showed residual compressive strength of 76.7 and 35.0 MPa, respectively, due to the sintering and to the formation of new crystalline phases (mullite, corundum, carnegieite and nepheline). Yet, residual compressive strength in the alkali-activated aluminosilicate specimens with replacement that were heated at 1200 °C dropped as a result of the partial dissolution of nepheline and carnegieite which may have generated closed pores within their microstructure. Hence, alkali-activation of volcanic scoria or metakaolin partially replaced with aluminium oxy-hydroxide is a remarkable process to get thermally stable products.

Cement-Treated Volcanic Scoria for Low-Traffic Road Pavements in the Azores Archipelago.

The Azoreans rely on an extensive network of rural roads for the most of the rural population’s activities (primary sector) and accessibility. To rehabilitate and maintain this network, asphalt concrete and crushed rock aggregate are usually used. However, in the region, the application of such paving technology can be extremely costly. It requires specialized contractors, dedicated equipment and raw materials that must be imported to most of the islands. Therefore, the use of locally available materials would result in more flexibility and fewer costs for planned interventions. In the Azores, known as bagacina, the volcanic scoria is a pyroclastic material, generally highly abundant in volcanic islands. This natural aggregate is inexpensive, easy to extract, and presents good geotechnical characteristics. However, due to its porous nature, it generally does not comply with the current specifications for pavement materials. Therefore, this study aims to evaluate cement-treated volcanic scoria to be used as low-traffic road pavement layers. The geotechnical properties and mechanical performance of the two types of scoriae were analyzed. As a result, both types of scoriae presented good behavior, according to the expected for a cement-treated material, and proved to be a suitable alternative for road pavements in the Azores Archipelago.