Fresh Sand Research Articles

Mechanical Reclamation of Spent Moulding Sand on Chromite Sand Matrix; Removal of Alkali-Phenolic Binder

The foundry industry generates large amounts of waste when casting metal into sand moulds. An important issue is the activities that are related to the re-recovery of the grain matrix (the main component of the moulding sand) for realising subsequent technological cycles. This process is particularly important in the case of the expensive chromite matrix that is necessary for use in manganese steel casting. The effects of the reclamation treatments of spent alkali-phenolic binder sand were evaluated by scanning electron microscopy with EDS, analysing the chemical composition in micro areas and proving the loss of binder on the surfaces of the matrix grains. Tests were also performed using the main criteria for evaluating a reclaimed organic binder: sieve analysis and ignition loss. A thermogravimetric analysis study was performed to assess the change in the chromite character of the grain matrix under the influence of temperature. The effects of the reclamation measures were verified by making moulding compounds on a matrix of reclaimed sand and a mixture of reclaimed and fresh sand. The tests and analyses that were carried out indicated the direction of an effective method for reclaiming used alkali-phenolic binder masses and the extent of the proportion of the regenerate in moulding sand in order to maintain the relevant technological parameters of the moulding sand.

Performance-optimised design of sand fog seal for pavement cold repair using RSM I-optimal methodology

ABSTRACT Sand fog seal is a preventive maintenance material to repair the early distresses in asphalt pavements. The objective of this study is to develop an optimal design guideline for sand fog seal to balance the demand for rapid traffic opening with the need to keep good road performance. Based on the response surface methodology (RSM) and I-optimal methodology, the effects of the components’ ratios (including water, filler, and sand) and their interactions on the curing process and surface function of sand fog seal were investigated. The test results showed that water can regulate the fluidity and dispersibility of the fresh sand fog seal mortar, but will prolong the curing process. The modified sodium bentonite, as the filler, can shorten the full curing time of sand fog seal due to its good moisture absorption and permeability. Moreover, the interaction of water and filler significantly affected the bonding strength, and the recommended water-filler ratio was 1.5. The sand content should be controlled to less than 25% to ensure good adhesion and abrasion resistance. Finally, a formulation design guideline for sand fog seal based on desirability optimization methodology (DOM) was proposed, with recommended formulation of 21.8% water, 30% filler, and 25% sand.

Reutilization of ferro-arsenic waste sludge for the development of concrete blocks through solidification: conservation of natural aggregates with policy suggestion

ABSTRACT In the present study, arsenic sludge and iron sludge extracted from a laboratory scale water treatment plant were aimed to reutilize for the development of concrete blocks. Three different grades (M15, M20 and M25) of concrete blocks were made by blending of arsenic sludge and improved iron sludge (50% sand and 40% iron sludge) in the range of density of 425 to 535 kg/m3 at an optimum ratio of 10:90 (arsenic: iron sludge) followed by mixing of designed quantity cement, coarse aggregates, water and additives. Concrete blocks developed based on this such combination exhibited 26 MPa, 32 MPa and 41 MPa compressive strengths, and 4.68 MPa, 5.92 MPa and 7.78 MPa tensile strengths for M15, M20 and M25, respectively. In comparison with the developed concrete blocks and the blocks made with 10% arsenic sludge and 90% fresh sand, the developed ones (employing 50% sand, 40% iron sludge and 10% arsenic sludge) showed more than 200% higher strength perseverance on average. Successful Toxicity Characteristic Leaching Procedure (TCLP) and compressive strength of the sludge-fixed concrete cubes classified it as a non-hazardous and completely safe to use value-added material. This process involves stabilization of arsenic-rich sludge generated from high-volume long-run laboratory-based arsenic-iron abatement set-up from contaminated water with successful fixation in solid matrix of concrete through complete substitution of natural fine aggregates (river sand) in cement mixture. Techno-economic assessment reveals such concrete block preparation at $0.09 each which is lesser than 1/2 of the present market price of same quality concrete block in India

Influence of Weather Conditions and Mechanical Reclamation on Molding Sand with Alkali-Phenolic Binder for Manganese Cast Steel

The article presents the results of research on the properties of molding sands in Alphaset technology (alkaline-phenolic). These sands are often used in steel foundries, producing large castings. However, knowledge about them, and especially about the changeability of their properties with the change of environmental conditions (seasons), is still insufficient. Various compositions of molding sand were analyzed based on fresh chromite sand and reclaimed sand. A binder and hardener in various mass ratios were used to prepare the mass. The research methodology included, among others, tests of tensile and bending strength, permeability, abrasion, gas emissivity, and ignition losses. These tests were carried out for summer and winter conditions. The results showed the optimal proportions of resin and hardener, showed the influence of ambient temperature on the properties of the molding sand, and the possible ratio of reclaimed sand in relation to fresh sand. However, you should always remember to verify them under the conditions of a specific foundry.

Optimal design of fresh sand fog seal mortar using response surface methodology (RSM): Towards to its workability and rheological properties

As a popular preventive maintenance material, sand fog seal (SFS) could fill the micro-cracks and improve the skid-resistance and wear-resistance of road surface, but little research has been conducted to explain how the components of fresh SFS mortar affect its workability and rheological behavior. In this paper, an improved workability evaluation system is established for fresh SFS mortar based on self-developed devices, including the basic indexes such as dynamic uniformity DUt,s, slump flow X, and seepage velocity Vs. There is a negative correlation between the fluidity index (slump flow and seepage velocity) and the uniformity index (dynamic uniformity), and both of them are important bases for the performance balance design of fresh SFS mortar. Then, the effects of water, filler and sand on the workability are evaluated using response surface methodology (RSM) with I-optimal design method. The results show that water mainly regulates the consistency of the SFS mortar, which in turn affects its flowability. The sodium bentonite filler could alter the suspension capacity of the fog seal paste and determine the state of dispersion of sand in the paste. Besides, the addition of sand plays a negative role in the fluidity of fresh SFS mortar. Meanwhile, three design intervals for fresh SFS mortar are proposed based on its workability, ① Easy-to-separate interval: DUt,s < 0.8; ② Hard-to-flow interval: X ≤ 54.9 mm and Vs = 0. ③ Recommended interval: DUt,s > 0.8, Vs > 0, and X > 54.9 mm, where the fresh SFS mortar can balance stability and fluidity well. Hence, to maximize the balance between uniformity and fluidity of fresh SFS mortar, a formulation design optimization guideline is proposed based on desirability optimization methodology (DOM). The formulation has the widest distribution of high desirability when the sand content is 25%. Finally, the results of rheological test show that fresh SFS mortar is a typical shear-thinning pseudoplastic fluid, which can fit the “Herschel-Bulkley” model well. Yield stress and plastic viscosity can be used as the important rheological indexes to predict the workability of fresh SFS mortar. In general, based on the approach proposed herein, an optimized fresh SFS mortar with both good uniformity and fluidity could be produced.

Colonial versus solitary breeding: nesting patterns of Brown-throated Martins Riparia paludicola in Morocco

This study explored reasons for variable nesting habits in a hole-nesting bird species that sometimes breeds colonially and sometimes alone. Nesting was surveyed over ten years in natural sand cliffs and similar features created by human activity along a river and nearby habitats. Two-thirds of nests were in small colonies of 2–16 birds, where nests were less than 25 m from neighbouring breeders. Many others were hundreds of metres apart. Individual breeding locations were abandoned after only a few years’ occupation, often without obvious habitat change. Birds responded very rapidly to the sudden exposure of fresh sand cliffs by starting new colonies. If floods occurred in the first half of the season, nesting in the second half shifted to less vulnerable areas. Substantial changes from year to year, in the location of breeding activity and the ratio of colony to solitary nests, were unrelated to variations in rainfall (a likely measure of feeding conditions) in the previous breeding season or the six months prior to breeding. The proportion of nests in colonies was positively correlated with the numbers of birds breeding, indicating that coloniality was not limited by available sites. Behaviour at colony and solitary nests suggested that one benefit of group nesting is more frequent and stronger response to birds of prey. Extra adults visiting nests alongside the breeding pair were more frequent at colonies, though the significance of this is unknown. There was no evidence for neighbouring breeders coordinating their visits to and from colonies. Costs of group nesting (more frequent disturbance by groups of non-breeders, and time in defence of nests) were higher at colonies, though levels of aggression were very low. Coloniality is more likely to be an incidental result of birds independently selecting good nesting sites in an unpredictable habitat, than because of social benefits of breeding close together.

Topographic zonation and polycyclic pedogenesis in the northern atolls of the Chagos Archipelago, Indian Ocean

We conducted soil surveys on two islands in the Peros Banhos and Salomon atolls of the northern Chagos Archipelago, Indian Ocean. We found muted but consistent topographic and soil zonation from the ocean shores to the lagoons. The main elements of the zonation are: berms of coral boulders and rubble along the heads of the ocean-side beaches; rubble-strewn soils inland of the berm; and pale sands with shallower topsoils and few coral clasts on slight rises and declivities over the rest of the islands. The ocean-side rubbly soils have interstitial coarse sand and are the most fertile on the islands, with dense tangled stands of unmanaged coconuts, profuse litter, and deep humic topsoils. Topsoils are shallower and less humic in the pale sands inland. Sand size decreases from ocean to lagoon, but increases with depth in most profiles. Water tables are often <2 m deep, and many soils have faint pale brownish mottling in the lower subsoils. There is a low tabular outcrop of bare Holocene coral sandstone on one of the islands. It is incised by shallow grikes that are partly infilled with silty muck, as are some small depressions in the central parts of both islands. The pedogenic environment appears to be dynamic, with storm surges depositing fresh sand, eroding coastlines, and infilling inter-island channels. Some soils have buried humic topsoils, stone layers, sand size inversions, and slight changes in sand colour, which are attributed to polycyclic pedogenesis. Some topsoils have elevated levels of total Zn, which is thought to be derived from long distance volcanic ash. Our data indicate that the soils are of low nutrient fertility. Total N and available P do not attain the strikingly eutric levels found in some atoll soils. The low fertility is attributed to the predation of seabirds by inadvertently introduced black rats. This precludes soil enrichment with marine-derived nutrients by guano deposition.

Numerical study of crosshole electromagnetic tunnel detection

Electromagnetic tunnel detection is studied numerically using a 3D analytic infinite lossy homogeneous space solution to magnetic dipole radiation and scattering from an infinite cylinder, in a crosshole context. At low frequencies, this serves as a model for a transmit coil radiating a time-varying magnetic field that is then detected from the open-circuit voltage induced on a receive coil. Numerical simulations illustrate how various parameters influence the signal strength and the ability to discern the scattered signal. Tunnel detection is achieved at relatively high frequencies (but below typical ground-penetrating radar frequencies) for fresh water-saturated sand and for weathered granite, which are lower loss media; for the coil and tunnel parameters used here, the optimum frequencies appear to be between 100 kHz and 1 MHz. Tunnel detection for fresh water-saturated clay, a much more lossy medium, can be achieved at a quite low frequency, with an optimum frequency between 1 and 10 kHz. These results suggest that, when a resonant coil system is used, tunnel detection may be possible in a wider range of earth media than previously reported, when the best-suited choice of frequency is used.

Lime-rich and lime-poor coastal dunes: Natural blowout activity differs with sensitivity to high N deposition through differences in P availability to the vegetation

In industrialized countries, biodiversity is threatened by high atmospheric N deposition. In coastal dunes, blowouts can mitigate this through deposition of fresh sand, but lime-rich and lime-poor dunes may differ in blowout activity. We studied natural blowout activity and explanatory factors in 2000 and 2014 in up to 51 sites along the Dutch coast, representative for other parts of Europe. We further analyzed plant and soil characteristics related to P nutrition in seven sites in 2019 and found that blowout activity was intrinsically linked to interactions between the geosphere, pedosphere and biosphere. Blowout activity was higher in lime-rich than in lime-poor dunes, especially in 2014. This difference could not be explained by wind velocity and only partly by position in the landscape, but was associated with pH, critical N load and rabbit density. At high pH, P availability to the vegetation was low. Arbuscular mycorrhizal (AM) plant species thus predominated, which belong to the most characteristic dune plants and may provide rabbit food of better quality than nonmycorrhizal (NM) or ericoid mycorrhizal (ErM) plants. Root biomass was also low at high pH, which may reduce cohesion of the sand and increase blowout activity, especially in areas with high rabbit density. At low pH, P availability increased, which favored NM and ErM rather than AM plants, and root biomass increased, which increased stability of the blowouts. As a restoration measure, (re)activation of blowouts may improve buffer capacity, characteristic biodiversity and conservation status of coastal dune grasslands. However, lime-poor dunes are more vulnerable to acidification, increase in P availability and blowout stabilization than lime-rich dunes. In extremely lime-poor dunes, it may even be better to let vegetation develop towards Dune heathlands, which are also EU priority habitats.

A Study into the Influence of Different Factors on the Behavior of Alkaline Element Concentrations that Cause Bed Agglomeration

In recent years, studies into the processes of bed agglomeration during the combustion of biomass have become increasingly relevant. The agglomeration processes are most largely influenced by the alkaline components of ash, which form low-melting eutectics by reacting with silicates. Therefore, it is very important to determine the critical concentration, primarily, of potassium that forms the most low-melting eutectics in the bed, at which the particles begin to sinter. The experimental studies are aimed at to investigate the effect of the temperature and the concentrations of alkaline elements on the process of particle agglomeration during the combustion of various types of biomass as well as biomass and coal, studying the presence of bed drain, determining the critical concentration of potassium in the bed, and calculating the estimated time before the start of sintering under conditions of an increase of potassium concentration in the bed. The experimental techniques and characteristics of the four studied types of biomass are described. Data on the fraction of agglomerated particles in the bed at different temperatures and concentrations of alkaline elements are given. Upon replacing a part of the sand by iron oxides, agglomeration is observed only at high temperatures (850°C and more). The obtained data are compared with the results of similar experiments carried out under conditions of the fluidized bed; in these experiments, the effects of the fluidization rate, particle size, and excess air on the agglomeration processes are considered. It is noted that the limiting potassium concentration is lowest in the case of a fixed bed. It is shown that real objects should be used when studying the dependence of the behavior of the potassium concentration in the bed on the operation time. The choice of the fraction of bed drain with the addition of a screened material or fresh sand is of practical interest. The calculation techniques and calculated data obtained with use of them on the behavior of the potassium concentration in the bed under various conditions are presented. The fractions of bed drain during combustion of sunflower husks and bark and wood waste are determined. In addition, it is shown that the joint combustion of husks and coal sharply reduces the probability of bed agglomeration.

Achieving environmental sustainability in the shell mould foundry through thermal reclamation

Shell moulding is a process for producing simple or complex near-net-shape castings and maintaining tight tolerances with a high degree of dimensional stability. The main objective of the present research is to achieve environmental sustainability by thermal reclamation of the used shell mould foundry sand and present the results of achieving environmental sustainability. The investigations indicate that the thermal reclamation of the used foundry sand helps in achieving sustainability, and the selection of optimal process parameters like percentage of resin, catalyst, and fresh silica sand addition are very important in the shell mould foundry.

Isolation and Identification of a Bioflocculant-Producing Strain and Application in Rice Vinegar Clarification

A bioflocculant-producing bacterium S-3# was isolated from fresh sand bones 40-50 cm underground in the desert region of China’s Ningxia Province. It was identified as Paenibacillus sp. based on 16S rDNA sequence along with its biochemical and morphological characteristics. Chemical analysis found that the bioflocculant from S-3# is mainly composed of extracellular polysaccharide. Researchers observed no noticeable change (above 91%) in its flocculating activities in pH range 2.0-9.0 in kaolin suspensions and hypothesized that it could be useful in clarification of rice vinegar (pH 2.9-3.5). Using one-factor-at-a-time experiments, dosage of bioflocculant, temperature of flocculation system and metal cations were investigated for their efficacy on rice vinegar clarification. The Box-Behnken design, an experimental design for Response Surface Methodology (RSM), was also used to create a series of 17 runs to optimize the operating conditions. Quadratic regression models with estimated coefficients were developed to describe the suspended particle removals of rice vinegar. Results showed that the optimal flocculation conditions were 3.94 mg/L bioflocculant, 0.32 mM CaCl2 and flocculation system temperature of 41.5°C, respectively. These findings were in reasonable agreement with the modeled values. Under these conditions, the increase rate of transmittance (λ = 900 nm) of rice vinegar ranged over 240.63% under these conditions.

Characterization of Waste and Reclaimed Green Sand Used in Foundry Processing

The aim of this study is to discuss the importance of characterization of green, waste green and reclaimed sand. The transformations and changes which take place in the green sand, are due to the casting process. Green sand which loses its properties during the casting process at a high temperature of molten metal results into waste green sand. Various techniques are applied for characterization of foundry sands. They include Universal Testing machine (UTM) for compressive and shear strengths, texture analyzer for impact test, Thermogravimetric Analysis (TGA) for weight loss kinetics, Inductively Coupled Plasma (ICP-AES) for elemental composition, sieves for Grain Fineness Number (GFN), permeability tester for permeability number of the mold, X-Ray Diffraction (XRD) for crystallinity, Scanning Electron Microscopy (SEM) for morphology and Fourier Transform Infrared spectroscopy (FTIR) for organic functional groups. The waste green sand after being reclaimed in two- stage attrition device, through mechanical attrition, has been later compared with the fresh sand. This study confirms that reclaimed sand can be used either directly for molding or it can be mixed with the appropriate amount of fresh sand.

An Experience of a Liquid Glass Mixture Using for AlpHaset Process in Russia

The features of a technology application AlpHaset process in Russia are considered, as well as the requirements imposed on the used materials, especially to forming sand, the reasons, which lead to searching for the technology, eliminating defects of this process, and the capability of using resins and hardeners of the Russian fabricator. The question about the opportunity of substitution of resin for liquid glass for this process was elaborated. The experience of AlpHaset technology process was learned, with the usage of a liquid glass, the extent of a regeneration of such a mixture at the factories of Russia was also studied. Laboratory studies were done and recipe of the mixture was created for AlpHaset process, where a resin is completely replaced with a liquid glass. At the same time, the work on receiving a reclaim from an aged dump of liquid glass mixture, which could serve as a substitute of fresh sand in a compounding for AlpHaset process, was completed. As the result, there was created and embedded a recipe of a mixture, where the reclaim (which is completely replacing fresh forming sand), received from aged dumps of traditional liquid glass mixture for process CO2, was used. The compounding of forming a mixture began to look as follows: a reclaim of liquid glass mix, a reclaim from the line, a liquid glass, and hardener.

Doñana mobile dunes: what is the vegetation pattern telling us?

In coastal dunes, changes in plant composition and vegetation pattern can reveal processes such as plant succession, dune stabilization or reactivation. With that goal, I sampled plant species composition, topography and sand mobility along 4 parallel transects perpendicular to the coastline in the mobile dune system of Donana. I used Split Moving Window to locate boundaries between plant communities along transects. To assess the main trends in variation, data of plant cover from all transects were subject to multivariate ordination analysis. Plant composition and geomorphological traits allowed to distinguish several stretches along all transects. Multivariate analyses reflected two different trends, plant succession and dune stabilization. High cover of Halimium halimifolium in the primary dune slack was consistent with the lack of new deposits of fresh sand. Growth of pine trees facilitated the colonization of the dune tail by H. halimifolium in a positive feedback. Although several studies have pointed out a decrease in the advance rates of dunes due to an increase in plant cover, the present results suggest that the increase in plant cover in the outer dunes is due to the stabilization of the secondary dune. Therefore, vegetation pattern evidenced a process of dune stabilization, which may produce loss of original plant communities and heterogeneity of dune landscapes.

Reclamation of used green sand in small scale foundries

Disposal of Used Foundry Green Sand (UFGS) remains one of the significant challenges faced by foundry industry nowadays. Experiments were performed to reduce the total clay content from 12% to as low as 2.2% in waste foundry sand. Three prototypes were developed during the course of this work. They include vertical fluidized bed, horizontal fluidized bed and a novel ball-mill type attrition and sieving unit. The cost per ton of reclaimed sand is higher in case of fluidized bed based prototypes while in case of attrition and sieving based prototype, it is less than half of the cost of the fresh sand. The experimental data generated on the two-stage attrition and sieving unit under different conditions is further used to arrive at a semi-empirical correlation and the optimum set of design and operating parameters to get the best performance.

Influence of the reclamation method of spent moulding sands on the possibility of creating favourable conditions for gases flow in a mould

Abstract The results of investigations concerning the influence of the applied sand matrix (fresh sand, reclaim) on the properties of moulding sands used for production of large dimensional castings (ingot moulds, ladles), are presented in the hereby paper. The performed investigations were aimed at determining the influence of various reclamation methods of spent moulding sands on the quality of the obtained reclaimed material. Moulding sands were prepared on the fresh quartz matrix as well as on sand matrices obtained after various reclamation methods. The selected moulding sand parameters were tested (strength, permeability, grindability, ignition losses, pH reactions). It can be stated, on the basis of the performed investigations, that the kind of the applied moulding sand matrix is of an essential meaning from the point of view of creating conditions minimising formation of large amounts of gases and their directional migration in a casting mould.

Assessment of the Possibility of Using Reclaimed Materials for Making Cores by the Blowing Method

Abstract The cumulative results of investigations of the possibility of using the reclaimed materials after the mechanical, thermal or mechanical-thermal reclamation for making cores by means of the blowing method in the alkaline CO2 technology, are presented in the paper. Three kinds of spent sands: with furfuryl resin, bentonite and alkaline phenolic resin, obtained from the foundry, were subjected to three kinds of reclamation: mechanical, thermal and combined mechanical-thermal, applying for this aim adequate experimental devices. The obtained reclaims were assessed with regard to the degree of the matrix liberation from the determined binding material. Reclaims of moulding sands with binders of the form of resin were assessed with regard to ignition loss values and pH reaction, while reclaims of moulding sands with bentonite with regard to the residual clay content and pH value. In all cases the results of the performed sieve analyses were estimated and the average characteristic diameter dl was determined. The reclaimed matrix was applied as a full substitute of the fresh high-silica sand in typical procedures of preparing core sands used for making shaped samples for bending strength investigations, Rgu.

Past and future of the EU-habitat directive species Liparis loeselii in relation to landscape and habitat dynamics in SW-Texel, the Netherlands

Dune slacks are important habitats, with many endangered plant species. A series of eleven dune slacks of 1–42years old was studied in SW-Texel, the Netherlands, with the EU-habitat directive species Liparis loeselii present in all except the youngest and oldest. Analysis of aerial photographs revealed that new slacks are currently formed every 4–5years. In each slack, topsoil and vegetation data were collected in 2010 and 2014–2015. During succession, vegetation changed from brackish pioneer stages to dune slacks with L. loeselii and Parnassia palustris and ultimately grassland species. Differences between dune slacks and sampling periods were mostly significant. Herb cover and soil C increased with slack age, and over the five year study period, while bare sand, bulk density and pH decreased. The annual pH-decrease was 0.055 and 0.075 for pH-H2O and pH-KCl respectively, and annual C-increase 0.16% and 35gm−2. Liparis loeselii was only present between pHH2O 5.8–7.5 and pHKCl 5.6–7.6, and only occurred at C-content below 4.3%. In lime-poor dunes, environmental conditions thus become unsuitable approximately 34years after the start of succession. In the dune slacks, Liparis loeselii established within 6years, showed peak values after 11–16years, and declined until conditions became unsuitable. Rejuvenation may occur after large storms with fresh sand deposits. However, even with further succession, the present populations are not endangered and probably last until 2040. With new dune slacks every 5years, L. loeselii occurs in approximately eight different dune slacks at the same time, ensuring viable populations also in the future. This shows that adverse effects of succession can be counteracted by dynamics on local and landscape scale.

Influence of furfuryl moulding sand on flake graphite formation in surface layer of ductile iron castings

The influence of the use of moulding sand with furan resin, prepared both with fresh sand and reclaimed matrix, on the formation of a flake graphite formation at the surface layer of ductile iron castings has been investigated. A series of experimental heats of ductile iron cast in moulds made of moulding sand characterised by different levels of surface active elements (sulphur, oxygen) were performed. The effect of the wall thickness and the initial temperature of the metal in the mould cavity on the formation of flake graphite in the surface layer of the casting is shown in the paper. Investigations carried out by means of scanning electron microscopy (energy dispersive X-ray spectroscopy and wavelength dispersive X-ray spectroscopy) showed concentration of gradient profiles of surface active elements in the castings surface layer, which are responsible for their quality. Finally, it has been shown that there exists a significant effect of the quality of the sand on the formation of the flake graphite layer and the surface characteristics of ductile iron castings.