Volcanic Aggregates Research Articles

An Experimental Study on Modified Concrete Using Partial Replacement of Gravel and Admixtures

Abstract: This study aims to test a concrete specimen with replacement partially of 15 % of the coarse aggregate by pieces of tires and volcanic aggregates and reduce 5% of the water/cement ratio by substituting with 4% percentages of styrene butadiene rubber (SBR) and 1% of superplasticizer. The main concrete components (cement: sand: gravel) were used in weight ratios (1:1.5:3) and a water to cement 0.45 was used and it was considered as a reference sample (Mix1). A water to cement ratio 0.40 was depended for the modified mixtures. Samples were cast for testing the compression strength with sizes 150 ×150 ×150 mm for ages 7 and 28 days. the absorption rate, with a size of 100 ×100 ×100 mm at age 28 days. Moreover, 150 ×150×150 mm for depth of penetration test at the age of 28 days. Briefly, the observed results were exhibited that the partial replacement of normal aggregate in concrete with volcanic aggregate affects negatively on the workability, so 4% of the polymer SBR and 1% of the superplasticizer have improved the workability. The improvement in the workability of concrete contributed to reducing the ratio of water to cement required for mixing compared to ordinary concrete, and this in turn led to an improvement in performance of hardened concrete. In addition, the reduction of the permeability level. The results also illustrated that the replacement of the gravel in the modified mixtures (Mix 3 and Mix 2) reduces the weight of hardened concrete by (10-12%) and (7-9%) compared with conventional concrete, respectively, which makes it suitable for use in mediumweight concrete applications. Moreover, it can be concluded that the strength properties of the modified mix with volcanic aggregate improved by 19-20% compared to that of the unmodified concrete. While the modified concrete by cutting tires showed significant deterioration in the concrete's resistance 21% despite the reduction of concrete permeability.

Living in the shadow of Vesuvius: Analysis of the wall paintings of Pollena Trocchia’s Roman buildings across historical eruptions

Through a multi-analytical approach the research focused on the evolution of wall painting technology used for two decorated buildings in Pollena Trocchia buried by volcanic deposits of Vesuvius. The study highlighted a different stratigraphy (with two or three layers) of mortar-based supports. Volcanic aggregate was added to lime binder for rinzaffo and arriccio, whereas calcite and marble dust first, then organogenic limestones were used for intonachino. Pictorial layers, applied using fresco and mezzo-fresco techniques, were obtained combining common (e.g., ochre) and expensive pigments (e.g., cinnabar, aragonite, Egyptian blue), showing diachronic changes in raw materials selection and the refinement of decoration.

Characterization and Analysis of the Mortars of the Church of San Francisco of Quito (Ecuador)

The relevance of the Franciscan community is reflected in the San Francisco church in Quito, which was built between 1535 and 1755. This architectural work belonging to the Franciscan complex was implanted on a plot of land with an area of 3.5 hectares and was one of the first buildings in the Audience of Quito. Eleven mortar samples that covered the walls of the central nave and side chapels were taken from the church’s main temple. The procedure proposed by the authors is based on a combined methodology following the standards and protocols for the less-invasive extraction of heritage samples. Tests included X-ray diffraction, petrography, and scanning electron microscopy with a microanalysis of the samples. Mortars with a rustic composition and rough manufacturing were identified to differentiate two types of mortar, one of earthen with volcanic aggregates and another of lime with volcanic aggregates. The mining data validated the existing historical documentation, the imaginary process, and the stages of the established constructions.

Durability tests on lime-based mortars from the historic built heritage of Catania (Eastern Sicily, Italy): An experimental study

Mortars, like any other natural and artificial stone materials, are subject to atmospheric weathering agents which affect their durability according to the intrinsic characteristics of the material, such as mineralogical composition, texture and pore structure.This paper aims to investigate the physical-chemical durability of lime-based mortars made with two different volcanic aggregates, locally known as azolo and ghiara, peculiar of the historic built heritage of Catania (Eastern Sicily, Italy). An experimental approach has been used, based on the reproduction in laboratory of historic mortars by using ancient recipes. The experimental samples have been characterized from a physical point of view and then subject to accelerated aging tests. Specifically, the samples have undergone: i) mineralogical investigations through X-ray diffraction (XRD); ii) thin section analysis by polarized optical microscopy; iii) pore structure analysis through mercury intrusion porosimetry (MIP); iii) water absorption by capillarity; iii) water vapor permeability test; iv) accelerated aging test by salt crystallization; v) decay by sulfur dioxide.Results obtained highlight that the higher microporosity which characterizes the ghiara mortars is certainly responsible for their greater water absorption by capillarity as well as for their lower resistance to salt crystallization and exposure to sulfur dioxide, with respect to azolo-based ones.

Testing the volcanic material burying Pompeii as pozzolanic component for compatible conservation mortars

The aim of this work is to evaluate the potential use of ashes and lapilli that buried Pompeii as pozzolanic material for the formulation of conservation mortars. XRD analyses proved that the mineralogical composition of these volcanic products is consistent with the original pozzolanic mortars preserved at the archaeological site. A first set of pozzolanic mortars were prepared by using silica sand as aggregate. After curing the lapilli-based mortars, the measured compressive and flexural strengths proved to be higher than those of the control samples made of commercial pozzolan. A second set of samples, prepared by replacing silica sand with similar size coarse ash and lapilli, proved that volcanic aggregates further enhanced the mechanical properties by the formation of interfacial transition zones. The result of this research demonstrates that the volcanic material burying the archaeological site of Pompeii could be used as raw material in the formulation of compatible conservation mortars. As volcanic pozzolan is increasingly investigated as potential Supplementary Cementitious Material (SCM) for the production of sustainable concretes, preliminary considerations about the impact of the present work to this field of research are also provided.

Cleaner technologies for asphalt mixtures combining reuse of residual aggregates, waste crumb rubber and warm mix asphalt additive

The reuse of waste materials and residual aggregates as well as the reduction of emissions has become vitally important for the environment, the economy and logistics of the asphalt paving industry. This study characterizes the performance and production properties of asphalt mixtures with waste crumb-rubber modifier from scrap tires, a warm mix asphalt surfactant additive and residual poor-quality volcanic aggregates as the single mineral component. The combination of these three cleaner technologies provides a promising solution to produce more sustainable materials by reusing two different types of waste and decreasing the manufacturing temperature at the same time. The compactability, stiffness modulus and fatigue performance characteristics were assessed in the laboratory for different low production temperatures and compared to conventional mixtures. The results indicate that these rubberized warm asphalt mixtures with residual vesicular and scoriaceous aggregates comply with the technical specifications for paving materials. The dynamic properties are maintained or even improved while reusing waste materials and allowing reductions of the manufacturing and compaction temperatures up to 20 °C, therefore, decreasing energy consumption and emissions.

Integrated design optimization framework for green lightweight concrete

The increasing global concern for the environment and advancements in computational tools and techniques are transforming the way building structures are designed and constructed. The current economic climate and growth of the Architecture, Engineering, and Construction (AEC) industry demand the creation of environmentally sustainable and efficient buildings, starting from the design stage. Despite the AEC industry being a thriving sector in many countries, it is vulnerable to environmental degradation due to the impact of building materials. This paper presents a decision support framework for the optimal structural design of green concrete buildings using recycled plastic aggregates and lightweight concrete. The framework considers uncertainties such as design safety, architectural requirements, material efficacy, cost-effectiveness, and environmental impact. The approach evaluates four concrete aggregate materials with varying characteristics: Natural Weight Aggregate, Lightweight Volcanic Aggregate, and Plastic-Based Green Lightweight Aggregates. The proposed approach is demonstrated through a prototype model, which shows cost savings of up to 5% per floor compared to the conventional concrete mix. The results provide quantitative evidence of the direct financial benefits of using green concrete in lieu of the optimization framework, which is expected to encourage construction professionals to use environmentally friendly concrete and take part in greening the construction industry.

The technology of ancient lime mortars from the Żejtun Roman Villa (Malta)

Studies on original mortars can greatly assist archaeological interpretations, as elucidating the composition of such mortars gives clues on the origin of raw materials, manufacturing technology, and the construction phases of a site. This article presents the multi-analytical characterisation of 24 mortars and plasters from the Żejtun Roman Villa, Malta, to support archaeological hypotheses on the history of the construction of the site. The samples, belonging to at least three distinct phases included in the stratigraphy of the Żejtun archaeological site, were analysed using polarised light microscopy (PLM), scanning electron microscopy (SEM–EDS), X-ray diffraction (XRD), thermogravimetry (TGA/DSC), X-ray fluorescence (XRF), ion chromatography (IC), and stable isotope analysis (13C and 18O). The assessment of the results through correlations with archaeological evidence identifies five types of mortars with varying degrees of hydraulicity. These are associated with different development phases of the site and distinctive uses and were mainly produced using local resources, except in the Early Roman period when natural pozzolanic raw materials started being used. As there are no natural pozzolans on the Maltese Islands, it is hypothesised that the pozzolanic materials used as aggregate in the mortars were imported to the Islands from neighbouring volcanic regions. This volcanic aggregate was especially abundant in one of the mortar types, which was used mainly as a bedding mortar for floors.

Characterization and Analysis of the Mortars of the Church of Santo Domingo in Quito (Ecuador)

The religious art of the Dominican order is reflected in Santo Domingo Church, which was built between 1541 and 1688. This work of heritage architecture, one of the first to be built in the colonized city, was affected by multiple earthquakes, interventions, and constructions that have not been clearly recorded. A total of 13 samples were taken from the mortar inside the cloister, central nave, and side chapel, following the minor destruction-testing protocols and standards suggested by the research team. The analysis included mineral characterization studies and quantitative analysis by X-ray diffraction, petrographic, and scanning electron microscopy with microanalysis of the samples. The results showed the presence of volcanic aggregates and lime mortars, mortars of rustic composition and coarse manufacture. The results of mineralogical data and texture have allowed us to corroborate the historical information described by the chroniclers, to date relatively studied sites and to establish a hypothesis of constructive stages.

Multilayer Technology of Decorated Plasters from the domus of Marcus Vipsanus Primigenius at Abellinum (Campania Region, Southern Italy): An Analytical Approach

Situated on the left bank of the Sabato river, the city of Abellinum (Campania region, southern Italy) represents a tangible testimony to the influence of the Roman civilization in Irpinia. At the site, where the remains of the public area of the town are preserved, archaeological excavations unearthed a monumental Pompeian domus, likely owned by Marcus Vipsanius Primigenius, a freedman of Agrippa, son-in-law of Augustus. The rooms preserved fine wall paintings of 3rd and 4th Pompeian style, reflecting the social status of the owner. From four rooms overlooking the peristyle, eight specimens of decorated plasters were collected, and petrographic and spectroscopic analyses were carried out to investigate the plastering and painting technology. Thin sections of all plasters depicted a multilayer technology, although differences in mix designs of the supports were highlighted. Some samples are pozzolanic plasters, containing volcanic aggregate, others can be classified as cocciopesto because of the presence of ceramic fragments mixed to the volcanic aggregate. Finally, the presence of marble powder also permitted the identification of marmorino. Moreover, the pigments, applied using a fresco or lime-painting techniques, consist of pure or mixed Fe- and Cu-based pigments to obtain yellow, orange, red, pink, and blue decorations.

Mechanical performance under dynamic loading of rubberized asphalt mixtures with highly-porous vesicular aggregate

In volcanic regions, the use of certain abundant aggregates of scoriaceous nature with high porosity to manufacture bituminous paving mixtures is a major problem due to the excessive heterogeneity, absorption and limited strength of these aggregates. Consequently, the properties of the mixtures often do not meet technical specifications. The aim of this research is to study the improvement of the mechanical performance of asphalt mixtures with these residual volcanic aggregates by using binders modified with rubber from end-of-life tyres, since environmental and economic requirements make it necessary to reuse both types of waste. Laboratory studies determining the compactability, dynamic stiffness, fatigue resistance and elastic constants have made it possible to characterise the mechanical performance of these mixtures during production and in service, and to compare them with conventional mixtures. It was found that the use of tyre rubber modified bitumen makes compaction somewhat more difficult, but reduces the particle size degradation of the porous aggregates and improves the mixture performance and durability, showing higher stiffness moduli and increased resistance to fatigue.

First field evidence of the electrical multipolar nature of volcanic aggregates.

The description of the formation of ash aggregates is crucial to our understanding of tephra dispersal and, therefore, to the forecasting of volcanic ash concentration in the atmosphere. Regardless of the importance of electrostatic processes, particle and aggregate charge is of complex determination both in the field and in the laboratory. We have measured the bulk charge carried by single aggregates at Sakurajima volcano (Japan) by inverting the sedimentation trajectory across two high-voltage copper plates filmed using a high-speed camera. Some aggregates were filmed during their breakage caused by the external electric field, which revealed the presence of inner highly charged multipoles with bulk charge up to one order of magnitude larger than the bulk aggregate. This electrical multipolar nature reveals the key role played by multipoles in aggregate formation and the shielding effect of aggregation on particle charge.

INFLUENCE OF PUMICE POWDER ON SOME PROPERTIES OF PHENOL-FORMALDEHYDE BONDED PARTICLEBOARDS

In this study, pumice powder as a volcanic aggregate was added in the particleboards' production. The effect of various ratios of pumice powder (10%, 20%, 30%, and 40%) on physical, mechanical, thermal and fire resistance properties was investigated. Pumice powder did not significantly affect particleboards' water absorption and thickness swelling values. However, the mechanical properties were significantly affectedwith raising pumice powder content. The modulus of rupture and modulus of elasticity decreased up to 46% and 45%, respectively. There was also a decrease in the internal bond strength up to 42%. Conversely, pumice powder improved the thermal degradation temperatures. Theonset temperatures increased with increasing pumice powder content above 300°C. Similarly, thepumice powder improved the fire resistance of particleboards up to 7% compared to control samples.

First field evidence of the electrical multipolar nature of volcanic aggregates

First field evidence of the electrical multipolar nature of volcanic aggregates

Investigation of geomechanical properties of tephra relevant to roof loading for application in vulnerability analyses

Tephra fall can lead to significant additional loading on roofs. Understanding the relevant geomechanical properties of tephra is critical when assessing the vulnerability of buildings to tephra fall and designing buildings to withstand tephra loads. Through analysis of published data and new experimental results on dry tephra (both natural samples from Ascension Island, South Atlantic and synthetic tephra made from crushed aggregates), we discuss the geomechanical properties of tephra relevant to roof loading, which include bulk density, grain size distribution and internal angle of friction. Compiled published data for deposits from 64 global eruptions reveal no clear trend in deposit densities based on magma composition or eruption size. The global data show a wide range of values within single eruptions and between eruptions of similar compositions. Published grain size distributions near to source (≤ 10 km) vary widely but again there are no clear trends relating to magma composition. We used laboratory tests to investigate the internal angle of friction, which influences deposit sliding behaviour. For dry tephra, at the low normal stresses likely to be experienced in roof loads (≤ 35 kPa), we found similar values across all our tests (35.8° - 36.5°) suggesting that any internal sliding will be consistent across a variety of deposits. By considering different magma compositions, densities and grain size distributions, we have provided an envelope of values for deposit parameters relevant to roof loading, in which future eruptions are likely to sit. Finally, we created synthetic tephra (fine- and coarse-grained pumice and scoria) by crushing volcanic aggregates and compared it to samples from Ascension and published data. Our results reveal that synthetic tephra successfully replicated the properties relevant to loading, potentially reducing the need to collect and transport natural samples.

Mineralogic and petrographic evaluation of aggregate quality – effect on compressive strength of concrete pavement

ABSTRACT The causes of low compressive strength in newly placed slip-form concrete pavement were investigated using stereo and transmitted polarised light microscopy and scanning electron microscopy (SEM). The poor-quality, low-strength concrete is attributed to cracks and gaps that fully or partially surrounded unsuitable, weathered, and altered basic and intermediate volcanic gravel coarse and fine aggregate particles and lack of bond with the cementitious paste. Weathering and mineral alteration was more severe at the rims of affected coarse particles, causing thin weathering rinds of weak minerals at aggregate surfaces. SEM X-ray elemental mapping showed rock-forming elements such as sodium, magnesium, calcium, and iron were present in higher concentrations in the interior portion of the aggregates; but occurred in lower concentrations at the rims, suggesting that these elements leached out during weathering processes. This study shows the importance of periodically evaluating aggregates for deleterious materials and overall quality so that changes in the quality of the mined and processed aggregate can be detected before incorporation into concrete. Also, it is important that materials engineers who select or approve aggregates should have a petrographer evaluate new or changed concrete aggregate sources for unstable minerals and the nature of any surface coatings that can affect concrete-making properties.

A GIS-based image processing approach to investigate the hydraulic behavior of mortars induced by volcanic aggregates

Since Roman Age, the reactiveness of the mortars was empirically sought using different aggregates added to lime to confer hydraulic properties. With the advent of microanalytical studies, great strides have been made toward a better understanding of how the aggregates can catalyze the formation of hydraulic phases. However, due to the small scale and the different distribution speeds of the reactions, the techniques routinely used are not fully performing for answering this task. In this work, an innovative semi-automated image processing procedure based on the multivariate statistical analysis of X-ray maps is adopted to highlight and quantify, for the first time, the hydraulic behavior of mortars in terms of reactivity between binder and aggregate. The method proposed has been applied to two different volcanic-based mortars (known as “ghiara- and azolo-mortars”) collected from historic buildings in Catania (Sicily, Italy). Obtained results allowed identifying, in both mortars, four distinct compositional sub-zones within the binder as well as mapping the distribution of the Hydraulicity Index (HI). This latter resulted to be quite higher for the ghiara mortar (HI from properly hydraulic lime to cement for ∼50% of the binder) with respect to the azolo one (HI from properly hydraulic lime to cement for ∼10% of the binder).

Investigating Factors Affecting Stability of Volcanic Ash Soil Aggregates under Heat

Volcanic ash soil aggregates can be disaggregated using heat under wet conditions. This study aimed to investigate factors affecting the disaggregation of volcanic ash soil aggregates in a field with organic cattle manure (M plot) and a field with chemical fertilizer (F plot) that were exposed to heat. The two-step wet sieving method, in which aggregates were sieved twice at different water temperatures for different times, was used to investigate the disaggregation caused by heat. It was found that increasing the temperature during the second sieve was more effective in disaggregating aggregates than extending the second-step sieve time. When the water temperature was increased to 80 °C, macroaggregates became more vulnerable, especially those in the F plot. The total carbon (TC) remaining in the soil aggregates was also measured after sieving. Although the TC content in aggregates decreased after sieving, there was only a minor relationship between decreasing TC content and the degree of disaggregation. This suggests that aggregates were not disaggregated by eluting binding agents containing carbon contents, but by partial breakage of the binding agent and/or the peeling of particles with binding agents from the aggregates.

Alkali-silica reaction in volcanic rocks: a worldwide comparative approach

The potential alkali-silica reactivity (ASR) of volcanic aggregates, especially basalts, remains a source of debate in the scientific community. When evaluating the potentially deleterious character of this type of aggregate, different laboratory testing methods may produce contradictory data; this is particularly evident when using the accelerated mortar bar test (AMBT). In order to better understand such discrepancies, this study applied several methods of characterizing potential aggregate alkali reactivity, including the accelerated mortar bar test (AMBT), petrographic characterization, and the concrete prism test (CPT). Moreover, this study assessed volcanic aggregate samples from sites around the world, including the Azores, Brazil, Canada, the Canary and Hawaiian Islands, Iceland, Japan, Mozambique, New Zealand, Norway, and Turkey. The results obtained contribute to accurately assessing the potential alkali reactivity of volcanic aggregates and enhance the understanding of their different behaviours.

High‐performing mortar‐based materials from the late imperial baths of Aquileia: An outstanding example of Roman building tradition in Northern Italy

AbstractThis study provides the first detailed insight into the composition and properties of structural mortars used in a 4th‐century AD bath complex in Aquileia, the emblematic center of Roman culture in Northern Italy. Eighteen mortars, taken from different structures of the site, and three stone samples from the vaulting opus caementicium have been analyzed adopting a multianalytical approach integrating optical microscopy, X‐ray powder diffraction, X‐ray fluorescence, and scanning electron microscopy coupled with energy‐dispersive spectroscopy. The properties of the compounds are outstanding, as revealed by the formation of hydraulic phases (i.e., Al‐tobermorite and AFm) in most of the samples: the waterproofing capabilities of cocciopesto mortars are remarkable, as revealed by the formation of anthropogenic Al‐tobermorite (5.5 wt%) in pool coating samples; the lightweight of the vaults was guaranteed by the use of porous caementa and pozzolanic volcanic aggregates imported from the Gulf of Naples, as demonstrated by petro‐mineralogical features and chemical analysis of major and trace elements. This is the first proven case of trade in these building materials to the north of the Italian peninsula. These outcomes shed new light on the robust technical expertise of local artisans in Aquileia and indicate that the Cisalpina province was by no means a peripheral reality in the Roman Empire, as far as mortar‐based materials are concerned.