Natural Limestone Aggregates Research Articles

Utilizing waste rocks from phosphate mining in Jordan as concrete aggregates

This study investigates the potential of replacing natural aggregates in concrete with aggregates obtained from Phosphate Mine Waste (PMW) rocks in Jordan. Several tests were conducted to determine the PMW rocks' chemical, physical, and mechanical properties according to ASTM standards. A comprehensive experimental investigation was conducted, involving thirty-six concrete cylinder specimens, to evaluate the strength and durability properties of concrete made with PMW rocks compared to concrete made with natural limestone aggregates. The tested aggregates of PMW rocks consist mainly of quartz, dolomite, montmorillonite, and fluorapatite. Their physical and mechanical properties were found to be similar to the natural aggregates used for concrete. Concrete specimens made of waste rocks had an average compressive strength of 28.72 MPa at 28 days versus 30.18 MPa for concrete specimens made with natural aggregates. The tensile splitting strengths of the concrete made with PMW aggregates were higher than expected, with an average of 5.36 MPa at 28 days, whereas the reference specimens had an average tensile splitting strength of 5.49 MPa at 28 days. According to the findings, PMW rocks can successfully replace natural aggregates in structural and infrastructural constructions, enhancing the circular economy concept and contributing to a more environmentally friendly mining industry.

Analyzing the Mechanical and Durability Characteristics of Steel Slag-Infused Asphalt Concrete in Roadway Construction

Steel slag is a solid byproduct of the steelmaking process, widely generated in the metallurgical industry. Due to its alkaline nature and excellent adhesive properties with asphalt, it represents a potential road construction material with outstanding road performance, making it well-suited for utilization in highway construction. This paper conducts a systematic analysis of the physical and chemical properties of steel slag, specifically South Steel Electric Furnace slag, and compares it with natural basalt and limestone aggregates. The aim is to establish a foundation for the application of steel slag in asphalt mixtures. Building upon this foundation, we carry out proportioning design for AC-13C and SMA-13 steel slag asphalt mixtures, followed by a comprehensive study of their high-temperature stability, low-temperature stability, water stability, and fatigue performance. Our research reveals variations in the chemical composition of different steel slags, with CaO, SiO2, and Fe2O3 being the primary components. The content of harmful elements varies depending on the steelmaking raw materials and additives used. Notably, the optimum asphalt-to-aggregate ratios for AC-13C and SMA-13 significantly surpass the specified requirements. The freeze–thaw splitting strength ratio and residual stability of steel slag AC-13C and SMA-13 asphalt mixtures exceed the specified requirements, with AC-13C demonstrating the highest water stability, boasting a freeze–thaw splitting strength ratio of 94.07%, and a residual stability of 93.8%. In terms of fatigue characteristics, SMA-13 exhibits a longer fatigue life than AC-13C, indicating superior fatigue performance for steel slag SMA-13. Steel slag enhances the abrasion resistance and rutting resistance of asphalt pavement surface layers, fully meeting the performance requirements for high-grade road surface layers.

The use of marine seashells as aggregates in pervious concretes

Waste recovery is now a favourable solution for technical and economic reasons. The purpose of this study is the valuation of marine co-products – seashells, whose goal is to produce an eco-material that responds to the environmental problem. The experimental study focuses on the idea of replacing natural aggregates with recycled shell aggregates and studying their influence on the properties of pervious concrete. For this purpose, six concrete mixtures were prepared, where three of them were based on natural crushed limestone aggregates with 20% of porosity but had different dosages of cement 250, 300, and 350 kg/m3. The other three concretes have identical compositions, except that crushed shell aggregates substitute the natural aggregates. The obtained results are showing that the use of crushed shells considerably influences the properties of the studied concretes. In the fresh state, all concretes present high slump values and low density. Using shell aggregates improves the mechanical resistance, especially the tensile strength, by bending for the hardened state. Despite their shapes, the shell aggregates used in this study do not affect the concrete porosity, and consequently, draining concretes with good permeability have been obtained.

Utilisation of Ceramic Stoneware Tile Waste as Recycled Aggregate in Concrete

The construction industry has a significant environmental impact and concrete production is responsible for a large part of CO2 emissions and energy consumption. This study focused on the reutilisation of a specific type of tiles ceramic waste (TCW), composed only of stoneware and porcelain stoneware tiles, hereafter referred to as ceramic stoneware (CS), as recycled aggregate in concrete. Natural limestone and CS aggregates (sand and gravel) were characterised (particle size distribution, water absorption, resistance to wear, density and X-ray diffraction analyses) and recycled aggregate concrete (RAC) was prepared by replacing 20, 50 and 100 vol.% of sand and gravel, separately. Concrete workability generally improved with CW addition, especially when replacing natural gravel. Although the compressive strengths of the concrete specimens prepared with recycled sand were slightly lower than those of the reference specimens, similar or better results were recorded with the recycled CS gravel. In consonance, the RAC developed with recycled gravel obtained lower water penetration depths than the reference concrete. No significant variation in tensile strength was observed when varying CS content (values within the 2.33–2.65 MPa range). The study contributes to sustainable construction practices and circular economy by promoting the valorisation and reutilisation of industrial waste and reducing the consumption of natural resources.

Intermediate Temperature Fracture Resistance of Stone Matrix Asphalt Containing Untreated Recycled Concrete Aggregate

The sustainable alternative of blending natural limestone aggregates (NAs) with recycled concrete aggregate (RCA) was investigated in this research in order to encourage the utilization of recycled concrete in heavy traffic paving applications. The Marshall Mix design method was used to optimize mix designs containing 0%, 10%, 35% and 50% RCA. Single-edge notched beam (SENB) and semi-circular bending (SCB) tests were then applied and the fracture energy and fracture toughness determined. The tests were conducted at intermediate temperatures (5 °C, 15 °C, 25 °C) and varying notch depths (0.2H, 0.3H and 0.4H). Fracture energy and toughness did not consistently follow the behaviour of mixes with only NA; however, it was determined in this study that a RCA content between 10% and 35% would achieve peak loads, fracture energies and fracture toughness values comparative to a virgin mix.

A Machine Learning Approach to Prediction of the Compressive Strength of Segregated Lightweight Aggregate Concretes Using Ultrasonic Pulse Velocity

Lightweight aggregate concrete (LWAC) is an increasingly important material for modern construction. However, although it has several advantages compared with conventional concrete, it is susceptible to segregation due to the low density of the incorporated aggregate. The phenomenon of segregation can adversely affect the mechanical properties of LWAC, reducing its compressive strength and its durability. In this work, several machine learning techniques are used to study the influence of the segregation of LWAC on its compressive strength, including the K-nearest neighbours (KNN) algorithm, regression tree-based algorithms such as random forest (RF) and gradient boosting regressors (GBRs), artificial neural networks (ANNs) and support vector regression (SVR). In addition, a weighted average ensemble (WAE) method is proposed that combines RF, SVR and extreme GBR (or XGBoost). A dataset that was recently used for predicting the compressive strength of LWAC is employed in this experimental study. Two different types of lightweight aggregate (LWA), including expanded clay as a coarse aggregate and natural fine limestone aggregate, were mixed to produce LWAC. To quantify the segregation in LWAC, the ultrasonic pulse velocity method was adopted. Numerical experiments were carried out to analyse the behaviour of the obtained models, and a performance improvement was shown compared with the machine learning models reported in previous works. The best performance was obtained with GBR, XGBoost and the proposed weighted ensemble method. In addition, a good choice of weights in the WAE method allowed our approach to outperform all of the other models.

Conversion of Municipal Solid Waste Incineration Bottom Ash in Asphalt Pavements

Abstract Municipal waste incineration (MSWI) is a widely used method in solid waste treatment that can reduce the generation of landfill waste. Meanwhile, MSWI-bottom ash (BA) can be employed as a substitute for aggregates in asphalt mixtures. This study aims to assess the feasibility and influence of MSWI-BA substitution for natural limestone aggregates in asphalt mixtures to reduce garbage accumulation and save natural resources. Through conventional methods, the energy dispersive X-ray spectrometer, and scanning electron microscope experiments, the physical and chemical features of MSWI-BA and natural limestone aggregate were analyzed. A Marshall mix design determined the optimum asphalt content of asphalt mixtures with various MSWI-BA contents. The road performances of asphalt mixtures with different MSWI-BA contents were studied using rutting, low-temperature splitting, freeze–thaw splitting, and Marshall immersion tests. The experiment results show that adding MSWI-BA to asphalt mixtures would decrease water stability. High-temperature stability is excellent when adding 10 % MSWI-BA, and low-temperature crack resistance is best at 20 % MSWI-BA content. MSWI-BA could be recycled in the asphalt pavement, and 10 % is recommended.

Assessment of particle packing models for aggregate dosage design in limestone and EAFS aggregate-based concretes

An experimental method and two discrete Particle Packing Models are assessed for aggregate mix design. The aim is to model the most compacted structure of commercial natural limestone aggregate and electric steelmaking slag fractions. The experimental method is reliable and effective, although somewhat laborious. Regarding the discrete models, the Compressible Packing Model and the 3-Parameter Particle Packing Model showed high reliability when used to perform the most compact of both the ternary and the quaternary aggregate mixtures. Eight concrete mixes were manufactured to produce concretes of low and medium workability, containing the highest possible content by volume of coarse aggregate, and their resultant in-fresh properties, defined through slump and density, confirmed the validity of using the Particle Packing Models for each mix dosage under study.

Utilization of BOF steel slag aggregate in metakaolin-based geopolymer

Steel slag, an industrial by-product during the steelmaking process, has not been effectively utilized so far. In this paper, the feasibility of using basic oxygen furnace (BOF) steel slag aggregate in metakaolin-based geopolymer was systematically evaluated. Tests results showed the use of steel slag aggregate (SSA) as full replacement of natural limestone aggregate could yield higher volume stability, improved compressive strength, smaller drying shrinkage and enhanced anti-freeze property of geopolymer concrete. Moreover, the activator of water glass was demonstrated to be superior to NaOH because free oxides in steel slag could be consumed in water glass solution. Discussion on the mechanism behind the superiority of BOF SSA in conjunction with alkalis was elaborated from the perspective of chemical reaction. The geopolymer matrix and interfacial transition zone (ITZ) were enhanced due to the diffusion of Ca ions to form the gel and densify the microstructure. Techniques of XRD, TGA, SEM/EDX were utilized for the analysis of the improved geopolymer matrix and strengthened ITZ. This research could facilitate the recycling and upgrading of steel slag for construction.

Bituminous base courses for flexible pavements with steel slags

The purpose of this research was to study the feasibility of incorporating steel slags into coarse bituminous mixtures. The objective was twofold: to reduce dependence on natural aggregates, and to provide a use for industrial by-products. The slags studied come from the manufacture of carbon steel in electric furnaces and are divided into two types: Electric Arc Furnace (EAF) slag and Ladle Furnace (LF) slag. The mixture designed is coarse bituminous concrete (AC22G), for base courses in flexible pavements. In a first phase, the physical characterization of the materials was carried out to check their suitability. In a second phase, three types of mixes were designed: a control mix (made with natural limestone aggregates), a mix where LF slag was introduced to replace the filler and the fine fraction (sand) of the mix; and finally, the feasibility of manufacturing a totally sustainable mix was analyzed, which would fully incorporate EAF slag as coarse aggregate and LF slag as fine aggregate and filler. In a third and final phase, the designed mixes were subjected to different mechanical, water sensitivity, and durability tests. The research demonstrated that the incorporation of EAF and LF steel slag as a substitute for natural aggregate in coarse bituminous mixtures is feasible, meeting regulatory requirements, improving sustainability in the construction industry, as well as reducing emissions, and contributing to climate change mitigation.

DURABILITY OF CONCRETE CONTAINING RECYCLED ASPHALTIC CONCRETE AGGREGATE AND HIGH CALCIUM FLY ASH

In this research, the durability of concrete containing Recycled Asphaltic Concrete (RAC) aggregate and fly ash were studied. The concrete was made from Ordinary Portland Cement (OPC), fly ash, water, sand and combination of natural limestone and RAC aggregates. The RAC aggregate was obtained from the discarded asphaltic pavement. The RAC aggregate was used to replace natural limestone aggregate at the replacement levels of 0, 10, 20, and 30 % of the total weight of aggregate. In addition, the high calcium fly ash from Mae Moh power station in the north of Thailand was used to partially replace OPC at the dosages of 0, 20, and 40 % by mass. The compressive strength, water absorption, porosity, flexural strength, modulus of elasticity and resistance to sulfuric acid were tested. The results showed that concretes with 28-day compressive strengths between 22.5 and 33.0 MPa, water absorption between 5.3-5.9 %, porosity between 12.2 and 13.5 %, flexural strength between 4.4 and 5.5 MPa, modulus of elasticity between 25.6 and 30.0 GPa were obtained. The replacement levels of RAC at 10 % and fly ash at 20 % gave the optimum compressive strength and mechanical properties of concrete for use as pavement concrete. In addition, the using of RAC aggregate together with fly ash in concrete work improved water absorption, porosity and sulfuric acid resistance and the use of RAC and high calcium fly ash will also increase the sustainability of the construction industry.

Investigation of the bond strength and microstructure of the interfacial transition zone between cement paste and aggregate modified by Bayer red mud

In this study, a method is proposed for modifying aggregate with Bayer red mud (RM), and the bond strength and microstructure of the interfacial transition zone (ITZ) in the concrete prepared using the modified aggregate is determined. Compared to concrete prepared using natural basalt aggregate, concrete prepared with RM-modified basalt aggregate aged for 7 and 28 days had a 25.08 % and 21.75 %, respectively, higher compressive strength and a 39.53 % and 15.30 %, respectively, flexural strength. Compared to concrete prepared using natural limestone aggregate, the compressive and flexural strengths of concrete prepared with RM-modified limestone aggregate increased by over 10.00 % and 20 % respectively, after aging of both 7 and 28 days. The RM had a higher wettability to cement paste than basalt and limestone, implying that cement paste on the surface of RM-modified aggregate had a correspondingly stronger microflow and filling capacity. In addition, concrete prepared with the RM-modified aggregate had a low voidage, a compact ITZ structure and strong interfacial adhesion, resulting in considerably enhanced mechanical properties. This study provides novel applications for RM that can be widely used in building materials and waste reduction and a new method for improving the mechanical properties of concrete.

Sustainable alternative aggregates: Characterization and influence on mechanical behavior of basalt fiber reinforced concrete

Demands to assess the feasibility of utilizing alternative sustainable aggregates in concrete have been raised because of the rapid depletion of virgin aggregates resources. In this study, a comparison of the physio-chemical properties of commonly used natural gabbro aggregates (NGA) and natural limestone aggregates (NLA) and their possible sustainable alternatives recycled concrete aggregates (RCA) and steel slag aggregates (SSA) is presented. The suitability of these alternate aggregates is assessed through several standardized tests. Chemical compositions, mineralogical and morphological properties of these aggregates are also reported. To determine the possible leachates of hazardous metals into the environment when used as concrete aggregates, the inductively coupled-plasma atomic emission spectroscopy was carried out on acid digestions of these aggregates. Additionally, basalt macro-fibers (BMF) were incorporated to improve the mechanical properties of concrete made with RCA and local NLA which are deemed as weak and unfit for use as aggregates in structural concrete. Experimental results revealed that both RCA and SSA could be used as sustainable alternative aggregates to have a cleaner production of structural concrete. They had acceptable leachate limits of the hazardous elements. The soundness test results and expansion under autoclave of SSA were well below the acceptable limits. The concrete made with SSA showed higher mechanical properties than the concretes made with other aggregate types. As expected, BMF improved the mechanical properties of concrete made with the low-strength NLA and RCA.

EFFECT OF RECYCLED CONCRETE AGGREGATE QUALITY ON PROPERTIES OF CONCRETE

ABSTRACTThe possibility of the use of recycled aggregates from the construction industry in green concrete production is of increasing importance to reduce the negative environmental impact associated with construction and demolition wastes. The objective of this study is to investigate the effect of recycled concrete aggregate (RCA) quality on the properties of hardened concrete properties such as compressive strength, splitting tensile strength, density, water absorption capacity and porosity accessible to water. The RCA used in this study was obtained from the crushing of waste concrete with two different compressive strengths (LRCA obtained from the crushing of waste concrete having compressive strengths below 30 MPa and HRCA obtained from the crushing of waste concrete having compressive strengths above 30 MPa). The natural coarse limestone aggregate was 100% replaced with coarse LRCA and HRCA. As a result of the study, the use of 100% HRCA and %100 LRCA instead of limestone coarse aggregate in the concrete adversely affected its mechanical and physical properties. In addition, HRCA showed better performance in terms of compressive strength, tensile strength, water absorption and porosity compared to the use of LRCA. Furthermore, the percentage of adhered mortar on the surface of LRCA and HRCA was analyzed using a computerized micro tomography device, and it was found that the percentages of attached mortar and aggregates are 61% and 35.5% for LRCA, whilst the attached mortar and aggregate contents for HRCA are 45.9% and 53.7%, respectively.

Assessment and mechanism analysis of municipal solid waste incineration bottom ash as aggregate in cement stabilized macadam

Abstract The objective of the paper is to assess the feasibility of using solid waste incineration (MSWI) bottom ash (BA) as cement-stabilized macadam (CSM) aggregate. CSM was prepared by replacing natural limestone aggregate with MSWI BA in different proportions (0%, 5%, 10%, 20%, and 30%). The physical properties, chemical properties, and micro-morphology of MSWI BA were studied to explore the mechanism of MSWI BA aggregate in CSM. The mechanical properties (unconfined compressive strength, cleavage strength, compressive resilience modulus), drying shrinkage, freezing resistance, and leaching behavior of CSM were tested. The results showed that MSWI BA had low density, low strength, high water absorption, high porosity, hydraulicity, and cementitious activity. Substitution of MSWI BA for natural limestone reduced the unconfined compressive strength, the cleavage strength, and the compression modulus of resilience of CSM, but these parameters still met the requirements of the specification. The CSM containing MSWI BA had higher cumulative water loss rate and smaller average dry shrinkage coefficient than traditional CSM. Adding 0–20% MSWI BA reduced the cumulative dry shrinkage strain of CSM. The residual strength ratio of CSM increased slightly at first and then decreased rapidly, and the CSM containing 0–30% MSWI BA met the freezing resistance requirements of semi-rigid base materials. The leaching concentration of heavy metals of CSM curing 7 days with 30% MSWI BA was still far below the limit of Chinese standard GB 5085.3.

Neutron shielding concrete incorporating B4C and PVA fibers exposed to high temperatures

Traditionally, concrete has been used in radiotherapy rooms, in nuclear fuel containers, in nuclear power plant foundations and other structures using large thicknesses to shield the radiation. Currently, the development of concrete technology allows us to produce cement-based composite materials incorporating fibers, improving mechanical properties, additives and additions, increasing certain properties such as the shielding against ionizing radiation. This paper explores the possibility of building protective walls using different specialized concrete skins, which protect against neutron radiation generated by nuclear fuels. The paper validates a lightweight neutron protection concrete for high and low activity containers considering the worst conditions of use. It has been proven that the mechanical properties, durability and behavior under fast increases of temperature are suitable for purpose. The studied concrete incorporates natural limestone aggregate, polyvinyl alcohol fibers and boron carbide as a neutron absorber. After exposure to thermal gradients of 100 °C, 300 °C, 500 °C, 700 °C and 1000 °C, the concrete is characterized by its residual physical and mechanical properties and its microstructural topography. Results show a reduction in mechanical properties, a decrease in the continuity of the material detected by ultrasonic impulse propagation and an increase in the presence of voids in the microstructure.

Coral aggregate concrete: Numerical description of physical, chemical and morphological properties of coral aggregate

With the increasing development of oceanic resources, coral aggregate concrete has wide potentials in the construction of islands and reefs, as well as the flood embankment, road and airport in coastal areas. However, the complex particle composition of coral aggregates, shape, surface structure and pores lead to unusual microstructure, workability, mechanical property and durability of resulting concrete. In this paper, the physical and chemical characteristics of coral aggregates are studied, and the particle shape features are analyzed. Quantitative parameters such as sphericity (ψ), angular number (AN), and index of aggregate particle shape and texture (IAPST) are used to characterize the features of aggregates. An indicator, namely texture index (TI), is proposed to characterize the surface microstructure of coral aggregate. The results show that the coral aggregates with rough surface and porous interior have unique tree-shaped and rod-shaped particles and the former accounts for 41.3% of the total weight. Coral aggregates have typical ‘concave hole’ characteristic, porosity of 48.2–55.6% and >12% water absorption. The average sphericity and AN of coral aggregate are 0.5–0.6 and 27.5–30.3, respectively. At the same particle size, the ψ of natural limestone aggregates is significantly larger than that of coral aggregates. The AN of coral aggregates is 2.4–3.0 times larger than that of limestone aggregates at a single grain size. At the same single-grain level, the IAPST of coral aggregates and natural limestone aggregates are between 31.6-34.3 and 18.6–19.6, respectively. The TI of the coral aggregates of 4.75–16 mm and 16–31.5 mm are 16.2 and 15.9, while the limestone aggregates are only 1.22 and 1.17, respectively. Compared with IAPST, the use of TI is more suitable to characterize the ‘concave hole’ feature of coral aggregate.

High-Strength Concrete Containing Recycled Coarse Aggregate Subjected to Elevated Temperatures

High-strength concrete (HSC) containing recycled coarse aggregate (RCA), as a partial replacement of natural coarse aggregate, is tested in this paper to have information on RCA concrete behavior at high temperature. The high-temperature mechanical properties were investigated with reference to a number of parameters, such as initial moisture content, ductility, heating rate, and preloading. Various factors including heating rates, moisture content, and the effects of preloading were investigated. Displacement measurements were obtained with the non-contact optical technique of digital image correlation. A scanning electron microscope (SEM) was used to view the fractured surfaces of the RCA concrete. Concrete specimens containing 100% of natural limestone aggregate or 15 and 30% (by volume) replaced with recycled aggregate were cast and heated up to 550–600°C with different heating rates (1.5, 2.0 and 10.0°C/min). A slight decrease in the compressive strength was observed (at room temperature, i.e. after cooling down to room temperature) as an effect of partially replacing natural aggregate with recycled aggregate. Nearly all HSC containing coarse RCA explosively spalled. The SEM images showed that most of the RCA concrete fractures were located along the interfacial transition zones. It appears, therefore, that increasing the replacement ratio may contribute to reducing the risk of explosive spalling in high-strength concrete.

Effect of design properties of parent concrete on the morphological properties of recycled concrete aggregates

This study attempts to highlight the effect of the old parent concrete and the crushing level on the morphological properties and surface texture of the obtained recycled concrete aggregate (RCA). Three different crushed RCAs were studied: concrete made from crushed natural limestone aggregate, concrete made of RCA and concrete made from rubberized concrete. In addition, one natural crushed limestone aggregate source was used as a reference. Two techniques were used, indirect methods and visual techniques. The visual moiré technique has been used to qualitatively visualize the 3-D particle morphological aspects and its surface texture while the image projection 2-D technique was used to determine the angularity of the aggregate particles. The following properties: angularity number, index of aggregate particle shape and texture were measured using the indirect method. The shape and texture of RCA were found to be mainly influenced by the quality of the original parent concrete and the crushing level. The visual moiré analysis results indicated that the differences in surface texture among aggregates from different parent sources can be easily distinguished. The attached mortar on the surface of RCA and the crushing level were likely found to influence the shape and roughness of aggregates from different parent concrete.

Influence of used waste cathode ray tube glass on alkali silicate reaction and mechanical properties of mortar mixtures

Rapid transition of electronic device manufacturing industry has led towards the increase of glass waste quantities, which are still being speculated. This resulted in increasing research on the use of waste glass in many different industries. In this study, the impact of using grounded waste cathode ray tube (CRT) glass as aggregate replacement (AR) on the alkali-silica reaction (ASR), mechanical properties and structure and microscopy of mortar were examined and reported. Crushed waste CRT aggregate was used to replace 0, 25, 50, 75 and 100% of natural limestone aggregate in mortar bars. ASR expansion values of mortar with added waste glass were investigated and tested for observation period according to Ultra-accelerated mortar-bar test. The results showed that the increase of AR percentage resulted in higher susceptibility to ASR. Mechanical properties and microscopy of mortar mixtures showed the potential of using waste CRT glass, due to the small difference between tested mixtures.