Applicability of waste foundry sand stabilization by fly ash geopolymer under ambient curing conditions

PurposeThe purpose of this paper is to investigate the effect of the replacement of natural coarse aggregate (NCA) with different percentages of recycled coarse aggregate (RCA) on properties of low calcium fly ash (FA)-based geopolymer concrete (GPC) cured at oven temperature. Further, this paper aims to study the effect of partial replacement of FA by ground granulated blast slag (GGBS) in GPC made with both NCA and RCA cured under ambient temperature curing.Design/methodology/approachM25 grade of ordinary Portland cement (OPC) concrete was designed according to IS: 10262-2019 with 100% NCA as control concrete. Since no standard guidelines are available in the literature for GPC, the same mix proportion was adopted for the GPC by replacing the OPC with 100% FA and W/C ratio by alkalinity/binder ratio. All FA-based GPC mixes were prepared with 12 M of sodium hydroxide (NaOH) and an alkalinity ratio, i.e. sodium hydroxide to sodium silicate (NaOH:Na2SiO3) of 1:1.5, subjected to 90°C temperature for 48 h of curing. The NCA were replaced with 50% and 100% RCA in both OPC and GPC mixes. Further, FA was partially replaced with 15% GGBS in GPC made with the above percentages of NCA and RCA, and they were given ambient temperature curing with the same molarity of NaOH and alkalinity ratio.FindingsThe workability, compressive strength, split tensile strength, flexural strength, water absorption, density, volume of voids and rebound hammer value of all the mixes were studied. Further, the relationship between compressive strength and other mechanical properties of GPC mixes were established and compared with the well-established relationships available for conventional concrete. From the experimental results, it is found that the compressive strength of GPC under ambient curing condition at 28 days with 100% NCA, 50% RCA and 100% RCA were, respectively, 14.8%, 12.85% and 17.76% higher than those of OPC concrete. Further, it is found that 85% FA and 15% GGBS-based GPC with RCA under ambient curing shown superior performance than OPC concrete and FA-based GPC cured under oven curing.Research limitations/implicationsThe scope of the present paper is limited to replace the FA by 15% GGBS. Further, only 50% and 100% RCA are used in place of natural aggregate. However, in future study, the replacement of FA by different amounts of GGBS (20%, 25%, 30% and 35%) may be tried to decide the optimum utilisation of GGBS so that the applications of GPC can be widely used in cast in situ applications, i.e. under ambient curing condition. Further, in the present study, the natural aggregate is replaced with only 50% and 100% RCA in GPC. However, further investigations may be carried out by considering different percentages between 50 and 100 with the optimum compositions of FA and GGBS to enhance the use of RCA in GPC applications. The present study is further limited to only the mechanical properties and a few other properties of GPC. For wider use of GPC under ambient curing conditions, the structural performance of GPC needs to be understood. Therefore, the structural performance of GPC subjected to different loadings under ambient curing with RCA to be investigated in future study.Originality/valueThe replacement percentage of natural aggregate by RCA may be further enhanced to 50% in GPC under ambient curing condition without compromising on the mechanical properties of concrete. This may be a good alternative for OPC and natural aggregate to reduce pollution and leads sustainability in the construction.

Effect of waste foundry sand and fly ash on mechanical and fresh properties of concrete

This exploratory study investigates the use of waste foundry sand (WFS), combined with supplement cementitious materials (SCMs), in concrete production. The Preliminary Investigation is based on three groups, where the first group studies different percentages of natural sand replacement with WFS (i.e. 5%, 10%, 15% and 20%), the second group analyses the addition of 5% silica fume with WFS, and the third group observes 10% metakaolin inclusion with WFS. The studied parameters include density, nondestructive test (UPV), compressive and tensile strength, acid resistance, and environmental benefit analysis. According to the results, the compressive strength of the concrete mix is enhanced by 17% by adding 20% WFS and 5% silica fume, and this value increases by 23% when adding an additional 10% metakaolin. Furthermore, the use of 20% WFS leads to a 3.27% decrease in the cost of concrete as compared to the control mix, with a decrease of 2.1% and 5.1% for silica and metakaolin-containing mixes, respectively.

Novel applications of waste foundry sand in conventional and dry-mix concretes

The primary objective of this research is to utilize an industrial waste byproduct such as waste foundry sand (WFS) as an alternative for fine aggregate in self-compacting concrete (SCC). This research focuses on the use of WFS in SCC to enhance durability and mechanical properties, to find an alternative for fine aggregate in SCC, to reduce the disposal challenges of WFS, and to make SCC lightweight and environmentally friendly. Initially, WFS was treated with chemical (H2SO4), segregating, and sieving to remove the foreign matter and clay content. For this study, WFS is considered in varying percentages such as 0, 10, 20, 30, 40, and 50. For this investigation, M60 grade SCC is considered as per Indian standards and EFNARC guidelines. After that, this research focuses on tests on various fresh properties of SCC in each batch to find the flowability and passing ability of various mixes prepared using WFS. Similarly, the mechanical properties of SCC such as compressive, flexural, and split tensile strength tests were performed at 7, 28, and 90 days curing periods, respectively. Likewise, durability properties of SCC were found in all the mixes prepared using WFS such as water absorption, sorptivity, resistance to chemical attack, and chloride ion penetration; tests of these properties were performed at 28 and 90 days curing periods, respectively. Based on the experimental investigation of SCC, it was found that WFS can be used in M60 grade SCC as an alternative for fine aggregate up to 30% without compromising much on its properties. Finally, this establishes that using treated WFS in SCC helps in reducing the generation of waste and prevails as a meaningful utilization method. This research will also establish that the use of treated WFS will reduce the density and make SCC a lightweight, green, and sustainable material.

This study is directed towards remedying some of the deficiencies in the present state-of-the-art concerning the behavior and design of flowable fill. The focus is on the utilization of waste foundry sand (WFS) and class F fly ash. However, the study addresses a much broader perspective so that a unified and rational approach becomes available to understand and predict the behavior of flowable fill in general. The objective is also to answer some of the questions which need to be answered before flowable fill can be used in many geotechnical applications. The report is organized in ten chapters. Chapter 1 outlines the objectives. Chapter 2 reviews the developments, applications, and advantages of flowable fill in general. Statistical data on the production and consumption of coal combustion by-products both in the United States and the state of Indiana are provided. A broad picture of the foundry industry in the United States, and in the state of Indiana is provided. The process of WFS generation is described. The environmental concern with regard to the use of WFS is briefly discussed. Lastly, the economics are addressed. Chapter 3 presents the basic physical and chemical properties of the materials, namely, cement, sand, and fly ash, used in this research. Chapter 4 deals with flow behavior of dry sand and fresh flowable fill mix. Flow curves are developed which help understand the mechanics of flow. Chapter 5 discusses penetration resistance test results using mortar penetrometer. A soil pocket penetrometer is also used to estimate the unconfined compressive strength as the fresh flowable fill hardens. The effect of drainage is studied by introducing geotextile drainage layers. Penetration resistance is correlated with the unconfined compressive strength. Penetration resistance necessary for walkability is defined. Chapter 6 presents 28-day and 90-day unconfined compressive strength test results. The 28-day compressive strength is correlated with the water/cement ratio. A step by step mix design procedure is described. Chapter 7 discusses mercury intrusion porosimetry and permeability test results, and bioassay toxicity test results on expressed pore solutions from hardened flowable fill. Chapter 8 discusses results of consolidated drained and undrained triaxial tests at different confining pressures, and also the Brazilian Tensile Strength test results. Chapter 9 presents the results of accelerated strength testing using hot water bath. Chapter 10 summarizes and presents conclusions for the present work.

Waste foundry sand (WFS) is a by-product of the metal casting process, which constitutes a sustainable solution as a replacement for natural sand (NS) in the production of concrete. This article provides an overview of two types of WFS, along with their physical and chemical properties. The present research highlights the potential applications of WFS in mortars, concrete, and self-compacting concrete (SCC). In addition to examining the influence of WFS substitution on workability, mechanical properties, and durability. The literature consulted indicates that the workability, mechanical properties, and durability of mortar, concrete, and SCC may be affected when increasing the substitution of NS with WFS. However, in some cases, WFS can offer comparable or improved mechanical and durability properties to NS. It has been observed that in some studies, impurities in the form of clay particles, dust, and phenolic resins of the WFS particles are the reason for the resulting decrease reported in workability, mechanical properties, and durability. Few studies report durability in terms of ultrasonic pulse velocity (UPV), freeze-thaw resistance, abrasion, chloride penetration, and sulphate resistance, which is a research gap that should be addressed. Moreover, the use of WFS is a viable alternative to NS, leading to a more sustainable and environmentally friendly approach for the construction industry.

The aim of this manuscript is to provide an environmental assessment of the creation and use of waste foundry sand (WFS) via an LCA in a foundry for grey cast iron. A life cycle impact assessment was carried out using SimaPro 8. This environmental analysis assessed the impact of creating waste foundry sand (WFS) in a foundry, Hronec (Slovakia, Central Europe). According to BREF, this foundry is classified as an iron foundry with a production capacity greater than 20t/day with processes typical for grey cast iron foundries. Molten metal is poured into single-use sand moulds. We identified those factors influencing the creation and use of WFS which significantly affect the quality of the environment. The use of WFS from the production of cores in regenerated moulding mixtures with installed circuits brings marked minimisation of material and energy inputs in the processes of creating WFS and it positively influences the consumption of resources and the quality of the ecosystem. Space for lessening the impact of WFS processes upon the consumption of resources and ecosystem quality is mainly found in recycling WFS in the building sector. In the next step, it is necessary to thoroughly verify the eco-toxicological properties of not only the created WFS and other foundry waste, but mainly the building products for which this waste is used. In terms of transportation, it is important that waste is recycled at local level. The processes of creating WFS have a marked influence upon all the selected waste categories (consumption of resources, ecosystem quality, human health). By minimising material inputs into processes and the effective adjustment of production technology, a foundry can significantly lessen the impacts of processes for creating WFS upon the environment.

Waste foundry sand (WFS) is the by-product of the foundry industry. Utilizing it in the construction industry will protect the environment and its natural resources, and enable sustainable construction. WFS was employed in this research as a fractional substitution of natural sand by 0%, 10%, 20%, 30%, and 40% in concrete. Several tests, including workability, compressive strength (CS), splitting tensile strength (STS), and flexural strength (FS), ultrasonic pulse velocity (USPV), Schmidt rebound hammer number (RHN), and residual compressive strengths (RCS) tests were performed to understand the behavior of concrete before and after exposure to elevated temperatures. Test findings showed that the strength characteristics were increased by including WFS at all the phases. For a substitute rate of 30%, the maximum compressive, splitting tensile, and flexural strength were observed. Replacement with WFS enhanced the 28-day compressive, splitting tensile, and flexural strength by 7.82%, 9.87%, and 10.35%, respectively at a 30% replacement level, and showed continuous improvement until the age of 91 days. The RCS of foundry sand concrete after one month of air cooling at ambient temperature after exposing to 300 °C, 400 °C, 500 °C, 600 °C, 700 °C, and 800 °C was found to be in the range of 67.50% to 71.00%, 57.50% to 61.50%, 49.00% to 51.50%, 38% to 41%, 31% to 35% and 26% to 31.5% of unheated compressive strength values for 0% to 40% replacement of WFS, respectively. The RCS decreases with increasing temperature; however, with increasing WFS, the RCS was enhanced in comparison to the control samples. In addition, the replacement of 30% yielded excellent outcomes. Hence, this study provides a sustainable construction material that will preserve the Earth’s natural resources and provide a best use of WFS.

Globally, 113 million tonnes (Mt)/year of cast metal are produced, generating 10-20 Mt/year of waste foundry sand (WFS). In the UK alone, 200,000 tonnes of WFS are disposed via landfilling, challenging current efforts in tackling climate change and sustainable development (CO2 emissions due to transportation, extraction of natural resources, increase in landfill inputs). Concrete uses up to 90% of natural aggregate per tonne of concrete produced, including sand. The latter is the most extracted material in the world today. Approximately 40-50 billion tons of sands are mined around the globe for construction each year (UNEP2016). This work examines the use of waste foundry sand (WFS) as a replacement for fine aggregate (sand) in concrete. Two types of WFS supplied by Weir UK were used: quartz and chromite sand. After initial chemical and physical characterization, both types of sand were deemed suitable for use in construction. We compared the physical and chemical properties of both WFS types to river sand used for concrete production. Quartz and chromite WFS were finer and contained less silicon than conventional sand but richer in metallic ions. Leaching tests showed that WFS released metals, but their chloride, fluoride and sulphate content was less than river sand. WFS was then used in concrete at different fine aggregate replacement levels (30%, 50% and 100%). We investigated the mechanical performance at 28 days of curing, water transport and durability properties. Whilst the overall compressive strength decreased with increasing the WFS content, samples subjected to freeze/thaw cycles exhibited outstanding durability performance with respect to their water absorption capability. Preliminary results suggest that WFS is an environmentally sustainable solution both for the cast metal industry and the construction sector, as it repurposes a material otherwise disposed of into a raw material for durable concrete production.

Comparison of thermal performance between fly ash geopolymer and fly ash-ladle furnace slag geopolymer

Formulation, mechanical properties and phase analysis of fly ash geopolymer with ladle furnace slag replacement

One of the main challenges of the metallurgical industry is the management of the principal waste generated in the production of castings, which is the waste foundry sand (WFS). Potential solutions include the use of WFS in civil construction due to its mineral origin and the high volume available to meet possible demand. This study analyzed the influence of WFS on the mechanical and hydraulic properties of pervious concrete paving blocks. The experimental stage involved mixtures with 0% (reference) and 100% replacement of quartz sand (QS) by WFS, in concrete with consumption of 350 kg/m3 and 450 kg/m3 of Portland cement. Cylindrical specimens, pavers, and pervious concrete slabs were submitted to water absorption, compressive strength, and determination of the permeability coefficient (k) tests. Analysis for physicochemical characterization of leachate samples of the studied concretes was also carried out. After the statistical analysis of the results, it was possible to conclude that the WFS did not change the mechanical (Rc; Rt) and hydraulic (k; absorption) properties of pervious concrete mixes (WFS1; WFS2) when compared to the reference mixes (QS1; QS2). The changes in the results of the physicochemical parameters are related to the higher consumption of Portland cement from mix 2, increasing hardness, total solids, and alkalinity.

Mechanical and microstructural assessments of waste foundry sand in hot mix asphalt

Strength development of Recycled Asphalt Pavement – Fly ash geopolymer as a road construction material