Artificial Aggregates Research Articles

Research on the durability and Sustainability of an artificial lightweight aggregate concrete made from municipal solid waste incinerator bottom ash (MSWIBA)

This study chooses to use three common cementing materials, Portland cement (OPC), ground granulated blast furnace slag (GGBFS) and fly ash (FA), as the binder for the production of three artificial lightweight coarse aggregates (ALCAs) through cold bonding with municipal solid waste incineration bottom ash (MSWIBA) in which MSWIBA accounts for 70% of the total content by volume. In this study, three ALCAs were used to replace 0%, 30%, 60%, and 100% of natural aggregates used in the production of concrete. Through capillary water absorption and rapid migration of chloride ions, the effect of the replacement amount of ALCAs on the durability of concrete was explored. Additionally, in accordance with the Material Sustainability Index (MSI), a statistical analysis of the CO2 emissions, energy consumption and cost of the concrete made of the three ALCAs was carried out. Studies have shown that ALCAs can improve the Interfacial Transition Zone (ITZ) and pore structure of concrete, thereby improving the ability of concrete to resist chloride ion penetration. In addition, the use of ALCAs can reduce the cost of concrete. Among the ALCAs used in this study, those which use GGBFS and FA as adhesives (without OPC) can improve the durability of concrete the most and reduce CO2 emissions.

A Preliminary Laboratory Evaluation of Artificial Aggregates from Alkali-Activated Basalt Powder

The widespread use of natural aggregates is one of the main causes of the depletion of natural resources, as aggregates are constituents of several construction materials. Alternatively, it is, today, proven to be feasible to use mining tailings, either natural or recycled materials, to produce artificial aggregates through specific processes. A possible way to produce artificial aggregate is through the alkali activation of the powdered material in a process called geopolymerization. This study proposes to use a basalt powder and two different metakaolins as precursors for the production of an alkali-activated artificial aggregate, with a specific shape and size achieved by using 3D-printed molds. The experimental aggregates were evaluated using traditional tests for natural aggregates, such as resistance to compression, specific density and resistance to abrasion and fragmentation. Furthermore, the material was chemically analyzed in order to evaluate the geopolymerization process promoted by the two adopted metakaolins. The physical tests showed that artificial aggregates do not perform well in terms of resistance to wear and fragmentation, which can be improved. However, they revealed promising results in terms of skid, polishing and micro-texture.

Tensile over-saturated cracking of Ultra-High-Strength Engineered Cementitious Composites (UHS-ECC) with artificial geopolymer aggregates

Ultra-High-Strength Engineered Cementitious Composites (UHS-ECC) incorporating artificial geopolymer aggregates (GPA) were developed and over-saturated cracking (i.e., average tensile crack spacing smaller than the theoretical limit) was observed in this novel material. The developed UHS-ECC exhibited an ultra-high compressive strength (over 150 MPa) and an ultra-high tensile ductility (over 8%) simultaneously. The influences of GPA size on the matrix properties, tensile performance, micromechanics, and cracking behavior of UHS-ECC were systematically investigated. Over-saturated cracking and double-stage crack evolution (i.e., a bilinear relation between average crack width and tensile strain) were observed in UHS-ECC with GPA size smaller than 0.60 mm, while saturated cracking and single-stage crack evolution (i.e., a linear relation between average crack width and tensile strain) were observed in the other groups. Finally, the mechanism of over-saturated cracking and double-stage crack evolution was illustrated. The findings of this study extend the fundamental knowledge of ECC technology, which is meaningful for designing and developing UHS-ECC materials towards ultra-high tensile ductility.

A Review on the Application of Circulating Fluidized Bed Fly Ash in Building Materials

Circulating fluidized bed (CFB)-based coal burning technology is a type of clean coal combustion technology. Owing to its characteristics of low temperature combustion and desulfurization in furnace, the CFB fly ash is quite different from ordinary fly ash. Based on the comprehensive understanding of physical and chemical characteristics of CFB fly ash, this review summarizes the research progress of the application of CFB fly ash in Portland cement, magnesium oxysulfate (MOS) cement, solid-waste–based cementitious material (SWCM), concrete, geopolymer, artificial aggregate, and other building materials. The study shows that CFB fly ash can improve the early physical and mechanical properties and reduce the drying shrinkage properties for cementitious materials. Its unique chemical composition endows it with good application performance in the MOS cement, geopolymer, and SWCM. However, unfavorable characteristics of CFB fly ash, such as loose and porous structure, self-hardening behavior, and expansibility greatly hinder its practical applications in building materials. Therefore, some measures, such as addition of rational water-reducing agent, ultrafine grinding, mixing of ordinary fly ash, controlling the dosage of CFB fly ash, and water-cement ratio, must be taken to improve the negative influence of CFB fly ash on the building materials, in order to expand its application range. This article summarizes the application and research status of CFB fly ash in building materials, aiming at further promoting the research studies on CFB fly ash resource utilization in building materials and improving the efficiency of CFB fly ash resource utilization.

Mechanical Properties of Concrete Produced by Light Cement-Based Aggregates

There is great growing concern regarding the environmental impact of the building and construction industry. Aggregate, one of the most crucial ingredients of concrete, is among the concerns in this regard. There will be a steady increase in demand for aggregates in the near future, but limited natural reserves will not be able to respond to this demand due to the risk of depletion. This current situation is forcing researchers to conduct new and artificial material production techniques that keep the resources within the allowed boundaries. Artificial aggregate production is one of the new methods for sustainable, environmentally friendly material production. The mechanical and environmental properties of lightweight concrete produced via artificial aggregates in different ratios were investigated in this study. Fly ash (FA), ground granulated blast-furnace slag (GGBFS), and quartz powder (QP) were utilized in the production of artificial lightweight aggregate (LWA) by using a special technique known as cold-bonding pelletization. The prepared concrete samples with the artificial aggregates were subjected to compressive, tensile, flexural, and bonding tests. The test results demonstrated that the bonding, tensile, and compressive strength values of lightweight concrete with a 20% GGBFS coarse aggregate replacement ratio of lightweight aggregates increased by 11%, 12%, and 30%, respectively. Moreover, it has been observed that a 41% increase in compressive strength is possible with a 40% QP coarse aggregate replacement ratio of lightweight aggregates. Finally, in addition to significantly impacting the mechanical properties of the lightweight concrete produced via artificial lightweight aggregates, we demonstrated that it is possible to control and reduce the harmful environmental effects of waste materials, such as FA, GGBFS, and QP in the present study.

Exploring the carbon capture and sequestration performance of biochar-artificial aggregate using a new method

To achieve the ambitious goal of carbon neutrality, more carbon sequestration channels need to be developed. In this study, we tried to combine biochar with cold-bonded artificial lightweight coarse aggregate (ALCA) which is made from municipal solid household waste incineration bottom ash (MSWIBA).The strong carbon capture ability of biochar was used to attract external CO2 into the interior of ALCAs, which combined with CaO in MSWIBA to form CaCO3 to achieve the effect of chemical carbon sequestration. The total carbon sequestration and carbon sequestration rate of biochar-ALCAs were quantified by a self-designed CO2 concentration change test box, the physical and mechanical properties of biochar-ALCAs were investigated, as well as the changes before and after carbonization. The results showed that biochar and ALCAs had good synergistic carbon sequestration ability. The total carbon sequestration of biochar-ALCAs could reach 30.58–33.06 kg/ton. The carbon sequestration efficiency could reach 70.2 % and 84.9 % at 28 d/56 d in a low CO2 concentration environment (0.05 % VOL). In addition, the water absorption of biochar-ALCAs decreased by 4.3 %–13.9 %, the apparent density increased by 0.9 %–2.8 %, and the strength increased by 4.3 %–7.0 % after carbon sequestration, and the physical and mechanical properties were significantly improved. The purpose of this paper is to investigate the synergistic carbon sequestration of biochar in combination with ALCAs and to quantitatively assess its ability to solidify low concentrations of CO2 in the natural environment. A new test apparatus and test method were designed for this purpose. This paper may contribute for an important advance on the preparation of recyclable cement-type composites able to capture and solidify CO2 from the natural environment.

Cold Bonded and Low Temperature Sintered Artificial Aggregate Production by Using Waste Materials

The paper presented the possibility of manufacturing aggregates from industrial waste materials and their ecological benefits. The cold bonding process to create aggregates uses substantially less energy than the sintering technique. This study deals with the outcomes of an experimental assessment of the physical and strength properties of environment-friendly cold-bonded and sintered fly ash (FA), ground granulated blast furnace slag (GGBFS), and quartz (Q) lightweight aggregates. The waste materials were mixed with Portland cement at 20–50 percent by weight to make artificial lightweight aggregates. To investigate the impacts of temperature on the physical properties, such as crushing strength, density, and water absorption, the pellets were sintered at 300, 600, and 900 °C for an hour. The results show that all the produced aggregates might be categorized as lightweight aggregates due to the combinations' average densities being less than 2,000 kg/m3. The fly ash lightweight aggregates had higher density and crushing strength, as well as decreased water absorption. The density and crushing strength improved somewhat by raising the temperature, while the water absorption decreased with increased temperature. In this research, the most efficient mineral admixture concentration has been evaluated as 50 percent for both fly ash and ground granulated blast furnace slag and 30 percent for quartz for cold-bonded pellets. Furthermore, superior physical qualities have been reported at the 900 °C sintering temperature.

Water permeability, water retention capacity, and thermal resistance of green roof layers made with recycled and artificial aggregates

Substituting natural aggregates in the green roof substrate and drainage layers with lightweight artificial and recycled coarse materials is an eco-friendly alternative for applying lower load to the rooftops and preserving natural resources. However, a lack of precise understanding of the thermal resistance, water passing ability, and water holding capacity of green roof materials, including recycled and artificial materials, has raised a demand for measuring their Rc-value, water permeability, and water retention capacity as three main indicators for green roof systems. This study comparatively evaluated the thermal resistance, water permeability, and water retention capacity of green roofs with substrate and drainage layers, including coarse recycled and artificial materials. Different kinds of coarse granular aggregates were separately used for the drainage layer, including Natural Coarse Aggregate (NCA), Recycled Coarse Aggregate (RCA), Incinerated Municipal Solid Waste Aggregate (IMSWA), and Lightweight Expanded Clay Aggregate (LECA). The substrate layers were made with coarse recycled materials (SC) and without coarse recycled materials (SP) in wet and dry states. The outcomes revealed the highest thermal resistance and the lowest weight were obtained for 20-cm green roofs with a 15-cm substrate layer and 5-cm drainage layer of LECA. The water permeability of NCA was obtained 1.5 times more than that of LECA, whereas there was no significant difference between the result of the former, RCA, and IMSWA. The water retention capacity of the LECA was two times higher than that of the NCA. SC and SP satisfied the water passing and retention criteria given for green roofs.

Design, synthesis, and preliminary evaluation of [18F]-aryl flurosulfates PET radiotracers via SuFEx methods for β-amyloid plaques in Alzheimer’s disease

[18F]BAY-94-9172, [18F]AV-45, and [18F]GE-067 were FDA approved positron emission tomography (PET) imaging radiotracer of β-amyloid plaques (Aβ) in Alzheimer’s disease (AD). However, the radiochemical synthesis requires multi-step reactions and complex procedure. Recently, a protocol for radiochemical synthesis of sulfur fluoride exchange (SuFEx) using ultrafast 19F/18F isotopic exchange had been reported. We developed three pairs of novel 18F-labeled radiotracers by the “SuFEx” method for PET imaging Aβ plaques. The 18F labeling reaction can be completed quickly (30 s) at room temperature and purified using solid-phase extraction (SPE). The radiochemical purity (RCP) of the products was all greater than 95 %. In vitro fluorescent staining using Aβ-transgenesis mice section preliminary verified the affinity of tracers with Aβ. Competitive binding assay displayed high affinity of tracers for towards artificial Aβ1-42 aggregates (Ki values ranging from 3.53 ± 0.39 to 42.0 ± 4.24 nM). In vivo biodistribution and Micro-PET imaging showed that [18F]-Sulfur Fluoride β-Amyloid ([18F]SFA 1–6) could penetration the blood–brain barrier (BBB) in wild-type mice, and [18F]SFA 5–6 had a high initial brain uptake value (3.65 ± 0.9 % and 5.07 ± 0.1 % ID/g, respectively) and a fast washout (Brain uptake2 min/60 min = 4.15 and 4.61, respectively) from the brain. In vitro autoradiography demonstrated the affinity of the [18F]SFA 5–6 to Aβ plaques in AD human brain tissues. Our results suggested that [18F]SFA maybe a potential PET radiotracers for detecting Aβ in Alzheimer’s disease.

The potential use of cold-bonded lightweight aggregate derived from various types of biomass fly ash for preparation of lightweight concrete

• Cold-bonded artificial lightweight aggregate was produced from biomass fly ash. • Strength of artificial aggregate was compared to expanded clay aggregate. • Artificial aggregates could be applied as reinforcement for lightweight concretes. This paper explores the potential use of various types of biomass fly ash (FA); palm oil (P-FA), wood chip (W-FA), bagasse (BA-FA), and rice husk (R-FA), as raw material for lightweight aggregate formed by cold-bonded pelletization (CBP) for the first time. The results suggest it is possible to form 756–881 kg/m 3 lightweight aggregate with 20.30–28.84% water absorption, using FA and 10% Portland cement type 1 (PC). Single pellet crushing strength of 4–8 mm BA-FA and W-FA aggregates were 272.97 N and 194.82 N, making it comparable in strength to a commercially available ECA. The high strength of CBP aggregates was attributed to the SAI values, SiO 2 and Al 2 O 3 content of the ashes. Compressive strength of lightweight concrete reinforced with CBP biomass ash aggregate was found to be as high as 19.65 MPa.

Application of Artificial Functional Aggregates Encapsulated Bacteria for Self-Healing of Cement Mortars

Application of Artificial Functional Aggregates Encapsulated Bacteria for Self-Healing of Cement Mortars

The Use of Lightweight Aggregate in Concrete: A Review

One of the artificial lightweight aggregates with a wide range of applications is Lightweight Expanded Clay Aggregate. Clay is utilized in the production of light aggregates. Using leftover clay from significant infrastructure development projects to manufacture lightweight aggregates has a favorable environmental impact. This research examines the expanded clay aggregate production process and the impact of processing parameters on its physical and mechanical qualities. It also looks at secondary components that can be used to improve the qualities of concrete with expanded clay aggregates. The effect of the quantity of expanded clay aggregate on the fresh, hardened, and durability qualities of concrete is also studied. Expanded clay aggregates improve workability, fire resistance, sound insulation, and thermal insulation in concrete. Its inclusion, on the other hand, diminishes concrete's density, strength, elastic modulus, and resistance to freeze-thaw action.

Development of artificial geopolymer aggregates with thermal energy storage capacity

Integrating phase change materials (PCMs) into building materials has been widely used to improve the energy efficiency of buildings, in which microencapsulation and shape stabilization of PCMs are considered as two most effective solutions. In this study, artificial geopolymer aggregate (GPA) was employed as a novel PCM carrier for energy storage purposes. Detailed investigations were conducted into the physical, mechanical, and thermal properties of GPA-PCM, which can be engineered through different raw material selections (e.g., slag content, water/binder ratio, and incineration bottom ash (IBA) content). It was demonstrated that increasing the IBA content is an efficient means to increase the porosity of GPA, an index of the capacity to accommodate PCM. Up to 16 wt% PCM could be absorbed into the GPA through vacuum suction, resulting in a significant melting enthalpy of 24.74 J/g. Besides, GPA-PCM could achieve an excellent mechanical strength greater than 53.2 MPa and thermal conductivity of 0.510–0.589 W/mK. The time-temperature history curves of GPA revealed that up to 10.5 °C of thermal regulation was achieved due to PCM impregnation. The developed GPA-PCM composites facilitate an innovative and low-carbon solution for utilizing PCMs in construction for temperature-regulating and energy-saving purposes.

Performance of Artificial Compared to Natural Coarse Aggregates as Road Pavement Materials

Aggregates are the main material for road pavement made of natural stone. The availability of this natural stone will decrease because the stone is a non-renewable resource. The use of artificial aggregates can be an alternative to natural aggregates. The promotion of the use of waste as an artificial aggregates is starting to develop, especially with fly ash. Aggregates road materials must be tested to determine their characteristics by methods according to applicable standards. In this study, it can be seen that the aggregates of all quarries can be used as pavement materials, but the aggregates of the KB quarry show a poor flakiness index value. The test results of geopolymer-made aggregates made from fly ash showed that the abrasion and absorption values were not good. However, in general, it has good characteristics as road materials, so further research is needed to obtain geopolymer-made aggregates that meet the abrasion and absorption requirements for use as road materials.

Lightweight Concrete with Agglomerated Aggregate Based on Fly Ash

The production of lightweight concrete is mainly carried out in the traditional way using lightweight ceramic aggregates. The aim of the pilot research was to verify the possibility of producing lightweight concrete based on artificial aggregate in the form of agglomerated aggregate from high temperature fly ash. A representative of such aggregate is the artificial aggregate referred to as aploporite. This aggregate is characterised by comparable grain strength to ceramic aggregates but, on the other hand, has a relatively high absorption rate of up to 30 %. Concrete formulations with up to 50% replacement of natural aggregate by aploporite have been proposed in order to achieve the volumetric weights characteristic of lightweight concrete. The results obtained confirmed that it is possible to produce lightweight concrete with this aggregate and to achieve strengths comparable to those of ordinary concrete.

Potential of municipal woody biomass waste ash in the production of cold-bonded lightweight aggregates

Nowadays, increasing biomass wastes are incinerated and then transported to landfills for disposal, which occupies many land resources and causes health problems due to lack of any form of control. Therefore, a novel and green recycling method is urgently needed. In this study, a type of municipal woody biomass waste ash (MWBA) was granulated into a new type of artificial lightweight aggregates by the cold-bonded method. The effects of different water content (20–33%), rotation speed (30, 40, 50, 60 rpm) and rotation angle (30–60°) on the granulation efficiency and particle size fraction (4 mm–10 mm, 10 mm–16 mm, 16 mm–20 mm) of the municipal woody biomass waste ash aggregate (MWBAA) as well as the impact of varying cement content (5, 10, 15, 20%) and curing time (3, 7, 14, 28 days) on the performance of MWBAA were investigated. The MWBAA met the bulk density requirement of lightweight aggregate in EN13055 with bulk density between 841 and 1058 kg/m3. It was also found that 27–29% is the optimum water content for MWBAA manufacturing. The highest granulation efficiency (97.84%), as well as better gradation of MWBAA, could be achieved at a rotation angle of 55° and a rotation speed of 60 rpm. After 28 days of curing, the highest compressive strength of 2.6 MPa was achieved by the MWBAA with 20% cement content. Nevertheless, the porous and irregular shape of the unburned wood ash resulted in higher water absorption (25%), but had negligible effect on the bulk density and strength performance of MWBAA. This study thus provides an alternative solution to effectively recycle MWBA and potentially granulate MWBA into lightweight aggregate that can be utilized in concrete.

Re-cementation effects by carbonation and the pozzolanic reaction on LWAs produced by hydrated cement paste powder

This paper aims to evaluate lightweight aggregates produced with hydrated cement paste powder (HCP) using both carbonation and normal curing. The comparative study was conducted to figure out the effects of the portlandite amount in HCP I and HCP III on the aggregates during carbonation curing. The addition of up to 10 wt% silica fume to HCP I was attempted to make full use of the considerable amount of portlandite to prepare artificial aggregates under normal curing. The mechanical properties, reaction products and microstructure were analysed and the results show that the optimal carbonation periods for HCP I- and HCP III-type aggregates are different due to different amount of portlandite. HCP I-type aggregates can gain 3.14 MPa after 7-day carbonation and contain 35.60 wt% calcium carbonates. The remaining 13.95 wt% portlandite shows the enormous potential in elevating the strength and CO2 capture capacity jointly via the optimized carbonation curing method. On the contrary, HCP III-type aggregates gained 2.97 MPa after 1-day carbonation and further carbonation decomposed C–S–H and lead to the formation of calcite and amorphous silica gel with significantly elevated specific surface area (from 10.69 m2/g to 42.96 m2/g). Additionally, the individual strength development of the prepared aggregates containing silica fume benefits from the sufficiently available portlandite due to the formation of secondary C–S–H, obtaining 2.39 MPa after 28-day normal curing.

Investigating the effect of preheating conditions and size effect on asphalt blending in recycled asphalt mixture: New approach based on artificial aggregate and laser scanning confocal microscopy

• The influence of preheating conditions and size effect on the blending phenomena were evaluated through 3D-FIT method. • The difference of asphalt blending between virgin and RAP aggregate were also investigated. • The longer curing time does not mean better blending, which exists a limited value and an optimal storage time. • Smaller sizes of virgin aggregate can mobilize more active reclaimed asphalt from RAP aggregate. The blending phenomena between virgin and reclaimed asphalt is a significant concern in asphalt paving, which play a crucial role in the final performance of the recycled asphalt mixture. Although past studies broadly discussed the asphalt blending by various test methods, the blending process holds 3D features due to the different aging degrees of reclaimed asphalt and different dispersity of virgin asphalt. The three-dimensional observation in the asphalt blending is still limited. Simultaneously, many factors (e.g., preheating temperature and time, transportation temperature, storage time, and aggregate gradation) will affect the blending process. The relationships between those factors and the blending phenomena are still unknown. To overcome this problem, this paper proposed a 3D fluorescence image method by laser scanning confocal microscopy and artificial aggregate. The artificial aggregate in the wooden cube form was used to analyze the blending process of virgin and RAP aggregate in three-dimension, respectively. Meanwhile, preheating conditions and size effect on the blending phenomena were also evaluated. The results indicate that temperature presents a more significant influence on the blending than the curing time. A longer curing time does not mean better blending, which exists a limited value and an optimal storage time. Compared to RAP aggregate, more homogeneous blending occurred on virgin aggregate after 2 h curing time at 180 °C, so the blending process on virgin aggregate should also be considered by researchers. This study may help to explain the production of recycled asphalt mixture and understand the blending phenomena in asphalt paving.

Preparation of phosphogypsum (PG) based artificial aggregate and its application in the asphalt mixture

How to massively consume phosphogypsum (PG) has attracted worldwide attention since this industrial by-product occupies considerable land resources and causes serious environmental problems. This study adopted PG to partly prepare the artificial aggregate to replace the natural aggregate in the asphalt mixture. The disk granulation and the jaw crusher produced two aggregates (D and C). Morphology, strength, internal structure and hydration products of the aggregate were characterized, and its influences on the properties of asphalt mixture were also evaluated. The optimal composition of the aggregate was recommended with a high PG utilization rate (80%) and sufficient strength. Both C and D aggregates had a low level of texture and were not suggested to be used on the surface layer of asphalt pavement. C aggregate had an excellent angularity and imparted the asphalt mixture with a better rutting resistance than D aggregate did. However, C aggregate easily got crushed during the Marshall compaction. The continuous hydration of D aggregate improved the moisture resistance of the mixture. Since it decreased the fracture energy of the mixture, especially at low temperatures, the artificial aggregate was not suitable to be used in the cold region. Overall, the PG-based artificial aggregates can partly replace the natural aggregate to be used in the asphalt mixture. This technology could be an economical alternative for massively consuming PG and saving natural resources.

Can statistical methods optimize complex multicomponent mixtures for sintering ceramic granular materials? A case of success with synthetic aggregates

The relationship between the proportions of multicomponent mixtures with the technological properties of ceramic granular materials (synthetic aggregates) has been studied using statistical methods. The four phases involved in the formulations have been: kaolin (K) as aluminosilicate source; cork powder (C) as organic carbon source; sodium carbonate (N) as flux and pyrite (P) as source of iron and sulfur. The Mixture Experiments - Design of Experiments (ME-DOE) has been the statistical methodology applied from the initial configuration of the 36 starting formulations to the final validation of the models and optimums. After granulation, artificial aggregates have been obtained by sintering in a rotary kiln, and their main technological properties have been determined. Bloating index (BI), particle density (ρrd), water absorption (WA24) and crushing strength (S) were selected as the four key characteristics to be modeled and optimized, using response surface and effect plots to assess the effect of K, C, N and P on such properties. 32 out of 36 starting varieties met the density criteria for lightweight aggregates. In the optimum formulations obtained, the minimum percentage of K was 83 wt%, so that the variations in the percentages of P, C and N were the critical variables for determining the final properties of the aggregate. The contrast between experimental and estimated data has shown that the models fit adequately, indicating that this type of approach may have enormous potential for future research on artificial aggregates and other ceramic materials.