Archaeobotanical macro remains from Late Bronze Age Kinet Höyük and Tell Atchana (Alalakh) in southern Turkey: Economical and Environmental Considerations

The geographical locations of Tell Atchana and Kinet Höyük between the Eastern Mediterranean region, North-Syria and South-Anatolia define them as a focal point of cultural and economic relations between these regions. One of the aims of this archaeobotanical study, which is based on the plant macro-remains from Kinet Höyük and Tell Atchana, is to contribute to the knowledge of the economic position of these settlements during the Late Bronze Age. It is of interest under which conditions the crops were grown, which general agricultural techniques were used, (e.g. soil management, fallowing etc.) as well as how and where crop-processing and storage were conducted within both settlements and how they compare to other relevant sites in the area. The main socio-economic question of this archaeobotanical study is whether crops were primarily brought to Tell Atchana and Kinet Höyük from neighbouring regions with trade relations or grown in their immediate vicinities by the inhabitants themselves or farmers from surrounding villages. The environment and its development under anthropogenic influence and natural factors is also focus of this investigation, as it defines the possibilities of cultural developments of Tell Atchana and Kinet Höyük during Late Bronze Age. In order to answer the mentioned questions, 33 samples from Kinet Höyük and 35 samples from Tell Atchana were studied. About 3350 seeds and fruits were identified, counted and grouped into 77 categories, which include plant species or types belonging to 20 families. Statistical analysis indicates that the organisation of agriculture in the stratified society of Tell Atchana, as far as plant production is concerned, is similar to north-eastern Syrian sites. Tell Atchana probably imported surplus food from surrounding villages and supported large-scale, but also small-scale specialised crop production. In Late Bronze Age Kinet Höyük there is evidence for intensification in large-scale agriculture, with a broad spectrum of crop plants, as a kind of risk-buffering. The spectrum of crops and wild species of Late Bronze Kinet Höyük and Tell Atchana reflects agricultural characteristics of the eastern Mediterranean cultures

Comparative Study of Ageing, Heat Treatment and Accelerated Carbonation for Stabilization of Municipal Solid Waste Incineration Bottom Ash in View of Reducing Regulated Heavy Metal/metalloid Leaching

This study compared the performance of four different approaches for stabilization of regulated heavy metal and metalloid leaching from municipal solid waste incineration bottom ash (MSWI-BA): (i) short term (three months) heap ageing, (ii) heat treatment, (iii) accelerated moist carbonation, and (iv) accelerated pressurized slurry carbonation. Two distinct types of MSWI-BA were tested in this study: one originating from a moving-grate furnace incineration operation treating exclusively household refuse (sample B), and another originating from a fluid-bed furnace incineration operation that treats a mixture of household and light industrial wastes (sample F). The most abundant elements in the ashes were Si (20 to 27 wt.%) and Ca (16 to 19 wt.%), followed by significant quantities of Fe, Al, Na, S, K, Mg, Ti, and Cl. The main crystalline substances present in the fresh ashes were Quartz, Calcite, Apatite, Anhydrite and Gehlenite, while the amorphous fraction ranged from 56 to 73 wt.%. The leaching values of all samples were compared to the Flemish (NEN 7343) and the Walloon (DIN 38414) regulations from Belgium. Batch leaching of the fresh ashes at natural pH showed that seven elements exceeded at least one regulatory limit (Ba, Cr, Cu, Mo, Pb, Se and Zn), and that both ashes had excess basicity (pH \u3e 12). Accelerated carbonation achieved significant reduction in ash basicity (9.3–9.9); lower than ageing (10.5–12.2) and heat treatment (11.1–12.1). For sample B, there was little distinction between the leaching results of ageing and accelerated carbonation with respect to regulatory limits; however carbonation achieved comparatively lower leaching levels. Heat treatment was especially detrimental to the leaching of Cr. For sample F, ageing was ineffective and heat treatment had marginally better results, while accelerated carbonation delivered the most effective performance, with slurry carbonation meeting all DIN limits. Slurry carbonation was deemed the most effective treatment process, achieving consistently significant leaching stabilization, while also effectively washing out Cl ions, a requirement for the utilization of the ashes in construction applications. The benefits of carbonation were linked to the formation of significant quantities of Ca-carbonates, including appreciable quantities of the Aragonite polymorph formed in the slurry carbonated samples

Effect of Accelerated Carbonation on AOD Stainless Steel Slag for Its Valorisation as a CO2-sequestering Construction Material

Non-stabilized Argon Oxygen Decarburisation (AODNS) slag in powdered form was examined for its carbon dioxide sequestration capacity and for its potential utilization in the fabrication of high value building materials. The curing of the sample was carried out in two accelerated carbonation environments: i) in a carbonation chamber, maintained at atmospheric pressure, 22 °C, 5 vol.% CO2 and 80% RH; and ii) in a carbonation reactor, where the CO2 partial pressure (pCO2) and temperature could be further increased. In the carbonation chamber, an average compressive strength of over 20 MPa, on a 64 cm3 cubic specimen, was obtained after one week of curing, which is sufficient for many construction applications. Further carbonation resulted in a linear increase of strength up ~30 MPa after three weeks. The CO2 uptake followed a similar trend, reaching a maximum of 4.3 wt.%. In the reactor, the compressive strength improved with an increase in pCO2 up to 8 bar, temperature up to 80 °C, and duration up to 15 h where the maximum CO2 uptake was 8.1 wt%. The reduction in porosity in the carbonated specimens was approximately in line with the strength gain in the samples. Phase analysis by X-ray powder diffraction and inspection by scanning electron microscopy showed the precipitation of calcite and formation of significant amounts of amorphous material after carbonation. Infrared spectroscopy also pointed to the presence of aragonite and vaterite. In the carbonation chamber, the calcite morphology was uniform throughout the specimen. In the reactor, however, the calcite crystals near the outer edges of the cubes had different morphology than those near the core. Carbonation of the slag resulted in the reduction of basicity by up to one pH unit, and contributed to controlling the leaching of several heavy metals and metalloids

Utilization of Carbonated BOF Slag as Partial Replacement of Aggregate in Cement Mortars

After direct mineral carbonation, a material rich in carbonates and with reduced quantities of free oxides is obtained. The aim of this work was to show that such materials can be used in the construction domain. Basic Oxygen Furnace (BOF) slag from the steelmaking process has been traditionally seen as unfit for bounded applications due to its propensity to swelling, resulting from hydration of its high free lime content. Here, BOF slag was crushed to suitable particle sizes, carbonated in an aqueous solution of carbonic acid, and utilized to replace 50% of natural sand aggregate in cement mortars. The mechanical and chemical properties of these mortars were compared to mortars containing non-carbonated slags, and a standard cement mortar as a reference. Tests were conducted to determine mortar flow and soundness, and cured mortar compressive strength and leaching tendencies. The results showed a satisfactory performance for all considered aspects (comparable with the reference) of the mortar sample containing 37.5 wt% (1.5 in 4 parts solids) carbonated BOF slag o

Understanding the autogenous shrinkage in alkali-activated slag/fly-ash blends

Alkali-activated materials offer the potential for more durable, sustainable and low-CO2 construction and building materials with reduced environmental footprints when compared to Portland cement concrete. However, this new concrete technology suffers substantially from early-age autogenous shrinkage and micro cracking. The aim of this work is to illuminate the intrinsic reasons that are responsible for larger autogenous shrinkage in alkali-activated slag/fly-ash (AASF) blends by understanding the essential link between solidification process (reaction mechanism, kinetics, phase formations and binder structures) and early-age autogenous shrinkage deformations. In this study, six different compositions of AASF are studied by varying the type and the concentration of three different activators: sodium metasilicate, combinations of sodium metasilicate with sodium carbonate and sodium sulfate . The results show that the solidification process strongly depends on both the alkalinity and anion type of the alkaline solution. A higher alkalinity (high amount of Na2O) accelerates the reaction process, as the presence of OH- ions enhances the dissolution of slag and also increases the solubility of silica and alumina. Therefore, the intense autogenous shrinkage of alkali-activated slag at early-ages can be attributed to the high amount of chemical shrinkage. Autogenous shrinkage of alkali-activated slag is not only caused by well-known self-desiccation process in hardened state, but related to the condensation shrinkage. The larger autogenous shrinkage in AAS may also be attributed to refined pore structure and silica polymerization, which is controlled by the nature of anion presence in the solution

Efecto de la distribución de absorción de agua del árido grueso reciclado en la distribución de resistencia a la compresión del hormigón de altas prestaciones

High water absorption is a typical characteristic of recycled coarse aggregate and is often used to explain the loss of performance of concrete when replacing natural coarse aggregate with recycled coarse aggregate. Extensive attention has been paid to the mean value of the water absorption of recycled coarse aggregate, but not to the standard deviation. This paper aims to assess whether recycled coarse aggregates with the same mean water absorption but different standard deviations will perform equally in high-performance concrete (HPC). The resulting HPC mixtures exhibited very similar compressive strength. Even so, it was hypothesised that as the standard deviation of the water absorption of recycled coarse aggregate increases over a wide range, the compressive strength of HPC will first increase due to local variations in the water/cement ratio, then decrease due to the presence of weak particles, and finally remain constant due to the role of the surrounding new mortar.La elevada absorción de agua es una característica típica del árido grueso reciclado. Esta característica se utiliza a menudo para explicar la disminución en el rendimiento del hormigón cuando se sustituye el árido grueso natural por el árido grueso reciclado. Se ha prestado mucha atención al valor medio de absorción de agua en el árido grueso reciclado, pero no a la desviación estándar. Este artículo tiene como objetivo evaluar si áridos gruesos reciclados con la misma absorción media de agua, pero diferente desviación estándar, tienen un rendimiento igual en el hormigón de altas prestaciones (HPC). Las mezclas de HPC resultantes mostraron una resistencia a la compresión muy similar. Aun así, se planteó la hipótesis de que a medida que aumenta la desviación estándar de absorción de agua del árido grueso reciclado en un amplio rango, la resistencia a la compresión del HPC aumentará primero debido a las variaciones locales en la relación agua/cemento, posteriormente disminuirá debido a la presencia de partículas débiles y, finalmente, se mantendrá constante debido al papel del nuevo mortero circundante

Advances in alkali-activation of clay minerals

To future-proof alkali-activation technology, there is a need to look beyond well-established precursors such as fly ash and blast furnace slag, due to resource competition, geographical distribution and technical limitations. Clay minerals are abundant and diverse aluminosilicate resources available around the world. However, due to the mineralogical complexity amongst the most common 1:1 (kaolinite, halloysite) and 2:1 (montmorillonite, illite) clay minerals, and practical issues such as workability, their use has been more limited. Recent advances have improved understanding both of pre-activation treatments (thermal, mechanical, chemical), and of the factors influencing clay reactivity, phase assemblages and properties of final products. This opens new opportunities for the exploitation of these resources to produce sustainable cements. A one-size-fits-all approach for processing and activating clay minerals is not viable. Instead, activation routes need to be tailored according to the clay mineralogy to achieve the binder properties required for key applications

Autogenous shrinkage of alkali-activated slag: a critical review

This paper provides a critical review on autogenous shrinkage of alkali-activated slag (AAS). It is reported that AAS paste, mortar, and concrete generally show larger autogenous shrinkage than Portland cement (PC) counterparts. Self-desiccation is the main driving force of the autogenous shrinkage of hardened AAS, but other mechanisms also play roles, particularly at early age. Existing models developed for PC do not give satisfactory estimations of the autogenous shrinkage of AAS, unless the pronounced viscoelasticity of AAS is considered. The susceptibility of AAS concrete to extensive cracking is not necessarily high due to the effects of stress relaxation, but local creep can exacerbate the development of microcracks. Various strategies have been proposed to mitigate the autogenous shrinkage of AAS, but many exhibit side effects, e.g., strength reduction. Existing testing methods for autogenous shrinkage of PC seem applicable to AAS, but the starting time and test duration need to be reconsidered

On the Effects of Relative Humidity and CO2 Concentration on Carbonation of Cement Pastes

Many environments to which concrete is exposed are highly aggressive due to various chemical components. In such environments, concrete is subjected to processes of chemical degradation, among which carbonation is one of the most frequently seen degradation processes. Though, the influence of saturation degree (or relative humidity - RH) of the specimen and CO2 concentration on the carbonation of cementitious materials is still not comprehensively described with respect to carbonation rate/degree as well as alteration in microstructure and mineralogy. This work aims at thoroughly investigating how these two key parameters affect the carbonation under accelerated conditions. Furthermore, the effect of initial moisture state of the specimen on the carbonation rate is also demonstrated. For such purpose, a numerical model at continuum scale is developed to investigate the effects of RH and CO2 concentration on the carbonation depth, phase changes in phases and porosity of hardened cement pastes due to carbonation under accelerated conditions. Verification with experimental results from accelerated carbonation tests shows a good agreement. The modelling results with supporting experimental data help to better understand the modification of material properties under different carbonation conditions and to optimize the carbonation conditions

Setting behavior and bioactivity assessment of calcium carbonate cements

Calcium carbonate cements have emerged in the last few years as an attractive candidate for biomedical applications. They can be easily prepared by mixing water with two metastable calcium carbonate phases––amorphous calcium carbonate (ACC) and vaterite––which (re)crystallize into calcite during setting reaction. The transformation kinetics (and therefore the final surface cement composition) strongly depends on the initial mixture design and is controlled by the dissolution of ACC, whereas calcite nucleation typically controls their recrystallization in fluid batch experiments. Novel compositions are presented in this paper by incorporating organic molecules as a proxy to test their capability to carry on other biomolecules like proteins or antibiotics. The hardened samples are microporous and show excellent bioactivity rates, although their mechanical properties still remain poor. However, this would not be a handicap for in‐vivo applications such as bone filling, especially in low mechanical stress locations