Comprehensive Characterization of Spent Chemical Foundry Sand for Use in Concrete

The foundry industry generates large amounts of spent foundry sands, which are stored, available for recovery in other industrial sectors but unfortunately poorly exploited. Different authors have studied the possibility of recovering them in concretes, which would also allow production of more sustainable cementitious materials. The variability of their results highlights the importance of a better understanding of the potential influential parameters of the by-products. Unfortunately, exhaustive characterizations of the materials are rarely performed, especially for chemically bound foundry sands. This article presents a case study for the recovery of a spent chemical foundry sand with an exhaustive physicochemical characterization of the by-product and an analysis of its influence on the workability and mechanical strengths of cementitious materials. The tests recommended by the European standard for aggregates for concrete confirmed the suitability of the by-product. Associated with additional chemical tests (scanning electron microscopy, X-ray fluorescence, X-ray diffraction, etc.) as well as metallic particles characterization, they highlighted possible influential parameters. The workability and mechanical resistance tests carried out on mortars and concretes confirmed the influence of the fineness of the by-product associated with other parameters. Its use at a substitution rate of 30% results in a strength class C 30/37 concrete.

Waste foundry sand characterization as paving aggregate

Waste Foundry Sands (WFS) are by-products of the steel industry due to the foundry process. The residual material can be used in civil construction as an aggregate because of its mineral origin. This paper aimed to characterize the WFS obtained at two sources, using laboratory tests that are regularly required in highway engineering specifications. The laboratory program showed that the tests results satisfy the main specifications in Brazil. Laboratory tests results also show that WFS has characteristics that are similar to the manufactured sand that is usually used in asphalt pavement construction. It is concluded that the WFS could be used in asphalt pavement projects, as a subgrade reinforcement, sub-base or base layer and in asphalt wearing courses.

Durability Study of Concrete using Foundry Waste Sand

This research was conducted to investigate the performance of fresh and hardened concrete containing discarded foundry sands as a replacement of fine aggregate. A control concrete mix was proportioned to achieve a 28-day compressive strength of 37 MPa . Other concrete mixes were proportioned to replace 15% and 35% of regular concrete sand with cleaned foundry sand and used foundry sand by weight. Concrete performance was evaluated with respect to compressive strength, tensile strength and modulus of elasticity. At 28-day age, concrete containing used foundry sand showed about 20 to 30% lower values than concrete without used foundry sand. But concrete containing 25% and 35% cleaned foundry sand gave almost the same compressive strength as that of the control mix.

Assessment of the mercury contamination of landfilled and recovered foundry waste – a case study

Environmental pollution by mercury is a local problem in Poland and concerns mainly industrial sites. Foundry waste are usually characterized by low mercury content compared to other heavy metals. Spent foundry sands with low content of Hg are the main component of foundry waste. However, Hg may be present in foundry dust, which may also be landfilled. Due to Hg toxicity, even a minimal content may have a negative impact on biota. This study focuses on assessing the mercury content of landfilled foundry waste (LFW), to assess its toxicity. Currently tested waste is recovered and reused as a road aggregate. The results were compared with the mercury content of local soils as the reference level. Waste samples were taken from foundry landfill. The mercury content, fractional composition, organic matter (OM) and total organic carbon content, pH and elementary composition of waste were analysed. It was found that the mercury content in LFW was very low, at the level of natural content in soils and did not pose a threat to the environment. The statistical analysis shows that mercury was not associated with OM of the waste, in contrast to soils, probably due to different types of OM in both materials.

Ophiolite Chromite Deposits as a New Source for the Production of Refractory Chromite Sands

Chromite foundry sands, mixed with binding resins, are employed in the industry to form molds for high demanding casting of metals and steel. As there is no substitute, these sands highly contribute to placing chromium at the top value of the economic importance parameter in the EU classification of critical raw materials. Finding new sources to produce these sands can contribute to lowering its criticality. Chromite foundry sands must meet strict quality parameters, referred to as Cr2O3 content, Fineness Index, SiO2 content, and Acid Demand. The foundry chromite market is dominated by South Africa production deriving from layered intrusion chromite deposits. Chromite sands from ophiolite chromite deposits, normally used for the metallurgical-grade chromite market, were tested as an alternative starting raw material to produce chromite foundry sands. The study of the silicate impurities assemblage showed that its mineralogy strongly affects the result of the most crucial parameter, the Acid Demand. Ophiolite chromite with serpentine impurities should be depurated to a hardly affordable 0.31% SiO2 content to meet Acid Demand quality threshold, due to high reactivity of this silicate with the acid environment of the test. Those with olivine impurities require to be depurated to a much more easily affordable 2.11% SiO2 content. As a result, ophiolite chromite with an olivine dominated silicate assemblage can be used as an alternative source of chromite foundry sands.

Investigation of complex permittivity spectra of foundry sands

This paper discusses impedance spectroscopy as a method to characterize different types of quartz sand, chromite sand, and mixtures of sand. Based on two types of measurement cells, the impedance spectra for various dry sands were measured. The spectra differ enough to allow the sands to be distinguished. The results were validated by extracting the relative permittivity from the impedance and comparing it to literature data. After that, the method could be applied with confidence to other material systems. The influence of moisture was investigated with two types of quartz sand, and typical mixtures of form sand, chromite sand, and regenerated (quartz) sand were studied. In each case, the sand composition had a distinct influence on the Nyquist plot of the impedance spectrum. Compared to results from a laboratory foundry system, the new method exhibits a much more systematic dependence on the sand composition. If one succeeds in describing the impedance spectra with an equivalent circuit model parameterized by only a few parameters, these parameters could be used to identify and classify sand mixtures in the field. This would allow one, for example, to implement feedback control strategies in foundry regeneration processes, which would stabilize the processes and improve the quality of the casting products.

Examination of Behavior from Selected Foundry Sands with Alkali Silicate-Based Inorganic Binders

The automotive industry is one of the most important customers for the foundry industry. In particular, casting of engine parts for combustion engines is one of the most demanding areas of casting technology. New generation of engine blocks and cylinder heads are getting geometrically more complicated in order to maintain or even increase performance. With the increased complexity, the strain for the casting molds is growing and the widely used technology of core making with standard silica sands is, for several applications, no longer reaching the demanded results. Furthermore, in last decade, there has been an effort in using inorganic binders in core making process, which brings along some additional technological challenges. In order to cope with these challenges, in this paper, silica and non-silica sands with round and angular grains as well as with fine and coarse grains are examined using an inorganic binder for strength, permeability, and thermal stability. The results shall provide useful information about the possibilities of application and combining different types of foundry sands, both silica and non-silica. With their impact on the selected sand core properties, they can help in solving problems in the core making process as well as reaching a high quality of the final product-casting.

A sustainable approach to optimum utilization of used foundry sand in concrete

Conservation of natural resources, healthy environments, and optimal utilization of waste materials are intimate needs of the present time, and this research work was carried out to fulfill these needs. In this experimental and analytical study, concrete was prepared by replacing natural fine aggregates with two types of used foundry sands by 10%, 20% and 30% (by volume). The properties of fresh and hardened concrete were investigated and compared with a replacement amount of fine aggregates from 0% to 30%. Compressive strength was evaluated after 7, 28 and 63 days of moist curing. Along with compressive strength, the modulus of elasticity was also investigated and a reduction in compressive strength and modulus of elasticity was observed with the increase in the amount of used foundry sand. A prediction formula was proposed to predict the compressive strength, and verified by current experimental observations and also with a large database that was also established in this work. The prediction formula may be considered as very helpful for predicting the potential of using used foundry sand as an aggregate in concrete.