Substitution Of Natural Sand Research Articles

Quantifying the informal sand market and its consequences: The case of Brazil

Sand is a globally abundant resource and one of the most used minerals in construction. Local scarcity is becoming more common owing to the increasing demand in urban areas and stricter environmental regulations. In addition, the environmental impact caused by sand mining is worsened by clandestine extraction, which operates in a predatory manner. To reach the targets proposed by the United Nations Sustainable Development Goals, a country needs to combat the illegal extraction of sand, and this is only possible by knowing the local situation that needs to be changed. This study aims to estimate more accurately the total sand consumption that is being illegally extracted and is used by the Brazilian construction sector, its consequences, and ways to mitigate it. The method is applicable to any country with a similar problem. The results show that 76% of the extracted sand in Brazil is being mined illegally. The sum of unspent funds in environmental recovery, annual uncollected taxes, and annual unpaid social charges due to the activities of unregulated mining companies were equivalent to USD 774 million (0.05% of Brazil's GDP) in 2020. Strategies for concrete and mortar industrialization, and the substitution of natural sand by secondary materials could mitigate half of the illegal sand market that supplies sand for Brazilian construction, but it requires efforts of the entire construction sector, society, and government.

Pore structure characteristics of artificial sand aggregate mortar

With the progressive depletion of natural sand, the substitution of natural sand with artificial sand as a construction aggregate has received significant attention. To analyzed the pore structure characteristics of artificial sand aggregate mortars, nuclear magnetic resonance (NMR) technology was utilized to analyze the distribution characteristics and dynamic changes of five types of aggregate gradation mortars, and fractal theory was employed for characterization. The study examined on the correlation between aggregate gradation and pore structure, fractal dimension, and assessed the connectivity of the pore structure. The results showed that: water-saturated samples were mainly composed of micropores and movable fluid pores after 28 days of hydration, while the micropores and clay-bound fluid pores dominated after 365 days of hydration. The formation of the pore structure in multi-aggregate-graded mortar is influenced by both the surface-to-volume ratio and aggregate packing density. At the same hydration time, lower porosity in water-saturated mortar results in increased non-homogeneity of the pore structure and a reduced permeability coefficient. Well-graded aggregate mortar has stronger resistance to hydraulic erosion, and the stronger the erosion effect of water will be with more developed pore structure.

Recycling of foundry sand wastes in self-compacting concretes: Use as cementitious materials and fine aggregates

Abstract This paper discusses waste recycling as a compound in building materials. Foundry sand-based self-compacting concretes (SCC) were investigated to see the possibility of recycling foundry sand wastes (FSW). FSW was used as a cementitious addition (by partial cement replacement: 10%, 20% and 30% wt. cement), then as a fine aggregate (by partial sand substitution: 10%, 30% and 50% wt. sand). For this, an experimental study was carried out to evaluate physical and mechanical properties of SCC at fresh and hardened states. The results show that the FSW also played the role of a filling material, which slightly improved the compactness of the concrete while saving part of the cement. According to the results of the non-destructive tests by ultrasonic tests, all concretes gave a dynamic modulus of elasticity that was almost identical and which was greater than 36 GPa. Compressive strength value slightly reduced with the cement substitution by the crushed foundry sand waste. However, up to 30% FSW, the compressive strength recorded after 28 days was around 30 MPa. A slight decrease in the fluidity of concrete at 10% substitution of natural sand by FSW was observed. After up to 30% replacement of sand by foundry sand wastes, the fluidity of the concrete was improved. The improvement in the fluidity of the concretes was perhaps due to the fineness of the natural sand and that of the foundry sand. When used as up to 50% of sand substitution, FSW can be used as a fine aggregate for concretes without affecting the essential proprieties of concretes.

Study on density and water absorption properties of timbercrete block

The demand for sand as natural aggregates has recently increased in building and construction, resulting in a significant decrease in resources and a rise in prices. At the same time, developing countries are concerned about managing sawdust waste. This experiment investigates the density and water absorption properties of timbercrete block (cement-sand-sawdust). This study partially substituted natural sand with sawdust to create lightweight material. The demand for sand as natural aggregates has recently increased in building and construction, resulting in a significant decrease in resources and a rise in prices. At the same time, developing countries are concerned about managing sawdust waste. The sand replacement with sawdust was at four (4) levels (0, 5, 10, and 15%) at two (2) levels of mix proportions: 1:4 and 1:6, and curing age at five (5) levels (7, 14, 21, 28 and 56 days). A total of one hundred and twenty (120) cubes were used to measure the density of the material at five different levels (7, 14, 21, 28, and 56 days). In comparison, 16 cubes were explicitly used for the water absorption test after seven days of curing. “Full immersion” was employed as a method of choice for curing. The results revealed that the water absorption rate increases for the two mix proportions as the replacement percentage with sawdust increases from 5 to 15%. In comparison, density declines as the percentage of sawdust replacement increases from 5 to 15%. The study concluded that for mix ratios 1:4 and 1:6, a maximum of 5% sawdust should be utilised to avoid excessive loss of mortar physical properties, which will also contribute to the reduction of sawdust waste generated in society. However, the best mix proportions at a maximum of 5% substitution of natural sand with sawdust is 1:4.

A review on substitution of natural sand with granite fines in sustainable concrete

• Irregular, angular and porous shape of GF particles caused high friction, water absorption and inferior workability. • The workability issue can largely be addressed by addition of water reducer. • Mechanical properties of 30% GF concrete can reach maximum strength due to filler effect, among others. • Due to similar reasons, durability of GF concrete can generally be improved as well. • Cement usage may be reduced due to more compacted microstructure of GF concrete. A mass amount of granite fine (GF), a byproduct of the cutting and grinding process in the masonry industry, is generated every year all around the world. Most of these wastes are landfilled which will cause serious environmental problems. The usage of GF as the sand substitution in concrete may ideally not only help minimize the environmental issues but also provide economic benefit. Due to significant variations on the properties of the material being used and different understanding of GF substitutional concrete existing among different researchers based on their experimental works and local material sources, a more conclusive and reconciled understanding should be established to improve industrial stakeholders’ confidence in applying this material for construction. In this paper, the laboratory tests and findings from various latest research papers and industrial reports are gathered to shed light on the effects of GF on the performance of concrete as natural sand (NS) substitute. Comprehensive reviews of GF concrete on the fresh property (e.g., slump, bleeding), hardened property (e.g., compressive strength, flexural strength, splitting tensile strength) as well as the durability (e.g., water permeability, water absorption, resistance to sulfate attack, and acid attack, carbonation, and chloride permeability) are presented. A comparative life cycle impact assessment study of four concrete mixes with different GF replacement levels is conducted by considering the cradle-to-gate boundary for the Singapore scenario. The results turn out that around 20% environmental impact reduction can be realized via the replacement of 25.6%−50% NS with GF.

Experimental Study on Mechanical Performance of Recycled Fine Aggregate Concrete Reinforced With Discarded Carbon Fibers

With the development of technology in every field, it is necessary to recommend an eco-friendly material to be utilized in the construction industry. Recently, using waste/recycled materials in the concrete as a substitute is a trend to bring sustainability to the construction industry, but the recycled/waste materials has poor mechanical properties, thus to enhance these poor properties, this research studies the mechanical performance of sustainable concrete incorporating waste materials as aggregates, the study is performed in the three stages. In the first stage, the natural sand was substituted with recycled sand in the percentage of 0, 35, 70, and 100%, and all the tests i.e. compressive strength, split tensile strength and flexural strength were performed on concrete which was cured in water for 28 days. As the 35% substitution of natural sand with recycled fine aggregate presented the optimum mechanical performance, it was selected for the third stage of the research. In the second and the third stages, the discarded carbon fibers were utilized in concrete with 2, 4, and 6% by weight. A total of 90 samples were prepared for this research, in which 30 samples were cubes, 30 samples were cylinders and 30 samples were beams, all the samples were tested at 28 days. Comparative analysis was performed to validate and verify the results of this paper with the relevant literature. The SEM test was also performed on a fractured concrete surface to study its microstructure. The outcome of tests revealed that the utilization of discarded carbon fibers in concrete enhances compressive, split tensile and flexural strength by 27.8, 17.8, and 35.9% and acts as a crack bridging and also restrain the propagation of the first cracks. Fibers also helped the concrete to improve its energy absorption capacity and ductility.

Compressive mechanical properties of cement mortar containing recycled high-density polyethylene aggregates: Stress–strain relationship

This study contributes to the understanding of the effect of recycled high-density polyethylene (HDPE) aggregates on the compressive mechanical properties and stress–strain relationship of cement mortar. HDPE aggregates recycled from plastic wastes were used to substitute natural sand in cement mortar, thereby offering a novel approach to plastic waste management and reducing the overconsumption of limited natural resources. The compressive behavior of cement mortar containing 0–100% HDPE contents was investigated after 7 and 28 days. The experimental results showed the negative effect of HDPE aggregates on the modulus of elasticity (Ec) and compressive strength (fcmax) of cement mortar. However, the substitution of natural sand with HDPE aggregates reduced the density and increased the axial deformation capability of cement mortar, particularly when the volumetric substitution percentage exceeded 50%. The Ec, peak strain, and ultimate strain exhibited strong relationships with the substitution percentage and fcmax. Furthermore, the proposed empirical relationships between the parameters were evaluated. Finally, stress–strain models of HDPE mortars were established based on the available models for concrete. The proposed models appropriately predicted the complete stress–strain curves of cement mortars containing various amounts of plastic content.

Experimental investigations on substitution of natural sand in concrete with copper slag and blast furnace slag

The constant decrease in the availability of good quality natural sand across the globe has led to increasing investigations on the possibility of utilizing by-products obtained from different industries as a replacement for natural sand. Copper slag and blast furnace slag are by-products of metallurgical processes occurring during copper and pig iron production, respectively. The substitution of natural sand using copper slag and blast furnace slag in plain and reinforced concrete has been permitted in Indian Standard IS: 383-2016 up to a certain percentage as replacing natural sand in concrete. In the present study, investigations were carried out to check the feasibility of increasing copper slag and blast furnace slag as a substitution of natural sand in concrete. Conventional (Natural) sand was replaced (by volume) with copper slag (0%, 25%, 50% & 75%), Granulated Blast Furnace Slag (GBFS) (0%, 30%, 60% & 100%) and Air-Cooled Blast Furnace Slag (ACBFS) (0%, 30%, 60% & 100%). Concrete mixes were examined by substituting conventional sand with copper and blast furnace slag in different proportions and were evaluated for different mechanical properties and durabil-ity-related parameters. Leaching studies were also carried out on selected concrete samples.

Application of self-produced artificial sand in the production of green mortar

Due to the large disposal of locally industrial wastes and the shortage of natural resources, turning industrial by-products into green artificial materials has been attracting many researchers in the world. Following this trend, this study evaluated the potential application of self-produced artificial sand (AS) in the production of green mortar. The AS was produced by the alkali-activated method using a mixture of 36.4% fly ash, 36.4% slag, 3.5% 10M NaOH solution, 11% Na2SiO3 solution, and 12.7% water. The mortar mixtures were designed based on the densified mixture design algorithm with the incorporation of the AS as the substitution of natural sand (NS) by 0 – 100 wt.% (interval of 20%). The engineering properties of the mortar samples in both fresh and hardened states were evaluated through the tests of workability, compressive strength (CS), water absorption (WA), and shrinkage/ expansion. The experimental results showed that the mortar sample incorporating 20% of AS to replace NS performed superior engineering properties in comparison to other samples. Further increasing the AS content generally caused a negative impact on the mortar’s performance. Increasing AS content beyond 20% systematically decreased the CS while both WA and expansion were increased noticeably. However, the properties of the green mortar produced for this study satisfied all of the requirements of the official Vietnamese standards. Thus, the research results further confirmed a great potential in producing green mortar using AS to either partially or fully replacement of NS. In addition, the use of AS greatly contributes to not only saving natural resources but also limiting the negative effects on the environment due to the exploitation and use of naturally sourced materials.

Evaluation of mortars produced with Baosteel slag short flow (BSSF) steel slag as fine aggregate

The objective was to evaluate the influence of Baosteel slag short flow (BSSF) steel slag, a byproduct of a Brazilian steel mill, as a fine aggregate on the properties of fresh state and on the compressive strength of mortars. The experimental work was to characterize the BSSF steel slag and to produce simple mortars (only cement) and mixed mortars (cement and lime), replacing the natural sand with the slag aggregate in 20%, 40%, and 60% by volume. The fresh state tests were specific mass, incorporated air, water retention, and squeeze-flow, while in the hardened state, compressive strength at 28 days was investigated. It was verified that mortars with higher slag contents required greater amounts of water to obtain the spread (consistency) on the flow table, which was fixed at 260±5 mm. The mortars with slag presented higher specific mass since the slag had a higher density than natural sand and less water retention in the case of simple mortars. In addition, it was verified that the mortars with BSSF steel slag presented lower values of maximum displacement in the squeeze-flow test, which negatively affected its workability in the fresh state, besides the properties of mortar adherence. In addition, it was verified through the analysis of variance that the substitution of natural sand by BBSF steel slag did not significantly influence the compression strength of mortars.

Sugarcane bagasse ash sand (SBAS): Brazilian agroindustrial by-product for use in mortar

SBAS (sugarcane bagasse ash sand) is the term used for the residue left over from burning sugarcane bagasse. Large amounts of this agro-industrial by-product are generated in Brazilian sugar and ethanol plants, and its disposal is an environmental problem. The application of SBAS as a fine aggregate in mortars can add value to this waste and also reduce the use of natural sand. The growing need to extract natural sand from Brazilian rivers has caused environmental problems. In this article, the effect of SBAS on mortars was investigated, specifically its compressive strength, porosity, carbonation depth and chloride penetration. The present study fills the gap in knowledge on the durability of mortars using different levels of SBAS. The substitution of natural sand by SBAS, especially with content of 30%, can lead to maintenance of mechanical properties, micropore clogging and improvement of the durability of mortars, in comparison with a reference mixture.