Lightweight Aggregate Research Articles

Preparation and Properties of Lightweight Aggregates from Discarded Al2O3-ZrO2-C Refractories.

Refractory materials are an important pillar for the stable development of the high-temperature industry. A large amount of waste refractories needs to be further disposed of every year, so it is of great significance to carry out research on the recycling of used refractories. In this work, lightweight composite aggregate was prepared by using discarded Al2O3-ZrO2-C refractories as the main raw material, and the performance of the prepared lightweight aggregate was improved by adjusting the calcination temperature and introducing light calcined magnesia additives. The results showed that the cold compressive strength and thermal shock resistance of the lightweight aggregates were significantly improved with increasing calcination temperature. Moreover, the introduction of light calcined magnesia can effectively improve the apparent porosity, cold compressive strength, and thermal shock resistance of the prepared lightweight aggregates at the calcination temperature of 1400 °C. Consequently, this work provides a useful reference for the resource utilization of used refractories, while the prepared lightweight aggregates are expected to be applied in the field of high-temperature insulation.

Mechanical properties, microstructure and GEP-based modeling of basalt fiber reinforced lightweight high-strength concrete containing SCMs

The pressing need to address recent global climate changes calls for replacing high-carbon-emitting cement with environmentally friendly materials that retain the strength and properties of conventional concrete. This study explored the mechanical properties of lightweight concrete (LWC) incorporating shale aggregate and basalt fibers alongside a partial replacement of environmentally detrimental cement with pozzolanic materials like fly ash (FA), blast furnace slag (BS), and silica fume (SF) up to 30 %. Twenty mix designs were developed to examine their mechanical properties and microstructural characterization. It was also observed that SF outperformed other industrial byproducts and gave better strength with the optimum replacement of 20 % cement, achieving 102.6 %, 105.6 % and 109.5 % of the control mix compressive, flexural, and split-tensile strength, respectively. However, a further increase of up to 30 % decreased strength. FA and BS resulted in lower strength than the control sample and other byproducts-based mixes, with compressive strength decreasing by 4 %–20.5 % at replacement levels of 10 %–30 %, respectively. BS resulted in an initial increase in strength at 10 % replacement but decreased by 10.8 %–21.6 % at higher levels. This trend was similar for flexural and tensile strengths. However, adding basalt fibers resulted in higher strength compared to non-fiber mixes and increased the strength of LWC by up to 25.2 %. The micromorphology and pore structure study indicated that the high-performance paste and fibers bridging effect were crucial for high strength. Gene expression programming (GEP) based modeling, validated against our own experimental results, was employed to predict the outcomes, demonstrating strong correlation coefficients for compressive, flexural and tensile strength (0.9430, 0.9609 and 0.9353, respectively). Additionally, SHapely Additive exPlanations (SHAP) analysis was used to assess the impact of each input parameter, highlighting the positive effects of the water-to-binder ratio and lightweight aggregate on the LWC's mechanical properties. This study is novel in its comprehensive examination of the combined impact of SCMs, shale aggregate and basalt fibers on the performance of LWC, a synergy not extensively explored in prior research. Furthermore, a novel generalized constitutive model was developed, and a SHAP analysis was performed to help design an efficient mix design to enhance the mechanical performance of LWC.

Bending performance of lightweight aggregate concrete beam subjected to reinforcement corrosion: Experimental and numerical study

The application of lightweight aggregate concrete (LWAC) benefits the structural behavior of long-span and high-rise buildings. However, the corrosion-related durability issue of bending elements made of LWAC has remained unresolved for decades, and the bending performance of corroded LWAC beam, including load-bearing capacity, stiffness, cracking, and etc., has not yet been clearly defined due to limited knowledge in the available literature. This study aims to investigate the bending performance of LWAC beams subjected to reinforcement corrosion, and the test results provide valuable data for addressing the research gap relevant to the topic and contribute fundamental knowledge to the promotion of structural LWAC elements. Seven reinforced LWAC beams were tested to examine the cracking behavior, characteristic loads and deflections, deformation ability, and distribution of cross section strain at various moments. The modelling method considering the effect of rebar corrosion for LWAC beam was proposed. It was concluded that the corrosion of longitudinal rebar led to decreased cracking, yielding, and ultimate moment of LWAC beam, while the corrosion of stirrups increased the cracking moment and had little effects on the yielding and ultimate moments. The ductility of the tested specimens initially decreased and then increased with the raising corrosion level of the longitudinal rebar, which was attributed to the variation in bond performance between the rebar and LWAC. All tested beams exhibited a yielding deflection smaller than 1/235 of the span length. The strain distribution of the mid-span cross-section exhibited a nonlinear feature with increasing mass loss of the corroded longitudinal steel rebar. The proposed modelling procedure considering the corrosion effect showed good agreement with the test results, and a preliminary analysis of the bending performance of LWAC beams with different steel reinforcement corrosion ratios was completed. Data Availability StatementAll data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request.

Investigation the behavior of LWAC encased steel columns after exposure to elevated temperature

AbstractThis paper presents experimental and numerical investigations on the behavior of eccentrically loaded lightweight aggregate concrete encased steel (LWACES) columns after exposing to elevated temperatures. Sixteen concrete encased steel (CES) columns were considered in the study, 12 of which were exposed to elevated temperature then eccentrically loaded up to failure at different eccentricity ratios. The effect of temperature on the load–displacement relationships, failure load, and failure modes of the concrete encased steel (CES) columns was monitored and evaluated. Experimental results have shown that as the temperature increases, the load bearing capacity of the CES columns decreased. It has also been showed that, at high temperature, the normal‐weight concrete encased steel (NWCES) columns experienced larger degradation of the load bearing capacity compared to that of LWACES columns. Also, this study presents a numerical simulation of the behavior of LWACES columns at elevated temperatures with eccentric compressive load. The numerical model was implemented in conducting parametric study to understand the effect of temperature distribution, concrete cover, eccentricity ratio, and high temperature levels on the behavior of the thermally exposed (CES) columns. Numerical results have revealed that, at temperature value of 500°C, the ultimate capacity of LWACES with eccentricity ratios of 0.75, and 1 has decreased by 17%, and 23%, respectively, compared to that of the column with eccentricity ratio of 0.5.

Performance Evaluation of Foamed Concrete with Lightweight Aggregate: Strength, Shrinkage, and Thermal Conductivity.

Lightweight concrete offers numerous advantages for modular construction, including easier construction planning and logistics, and the ability to offset additional dead loads induced by double-wall and double-slab features. In a previous study, authors proposed incorporating lightweight aggregate into foamed concrete instead of adding extra foam to achieve lower density, resulting in lightweight concrete with an excellent strength-to-density ratio. This paper further investigated the performance aspects of foamed concrete with lightweight aggregate beyond mechanical strength. To evaluate the effect of aggregate type and foam content, three mix compositions were designed for the lightweight concrete. Specimens were prepared for experimental tests on thermal conductivity and drying shrinkage of lightweight concrete. Results showed that while both the increase in foam volume and the incorporation of lightweight aggregate led to higher drying shrinkage, they also contributed to improved insulating properties and reduced potential of cracking. Using typical multi-storey modular residential buildings in Hong Kong and three other Chinese cities as case studies, simulations were performed to assess potential savings in annual cooling and heating loads by employing the proposed lightweight concrete. These findings demonstrate the practical benefits of using foamed concrete with lightweight aggregate in modular construction and provide valuable insights for further optimization and implementation.

Metallic aluminium in municipal solid waste incineration fly ash as a blowing agent for porous alkali-activated granules.

Porous alkali-activated materials are synthetic aluminosilicates that should be often produced as granules for practical applications. In the present study, municipal solid waste incineration fly ash with ~1.2 wt% of metallic aluminium was used as a novel blowing agent for metakaolin (their ratio ranged from 0% to 100%) with an aqueous sodium silicate solution as the alkali-activator and granulation fluid in high-shear granulation. The compressive strength of all granules was sufficient (≥2 MPa). Water absorption indicated an increase in porosity as the fly ash content increased. However, X-ray microtomography imaging showed no clear correlation between the fly ash content and porosity. The granules exceeded the leaching limits for earth construction materials for antimony, vanadium, chloride and sulphate. Of those, antimony, chloride and sulphate could be controlled by decreasing the ash content, but the source of vanadium was identified as metakaolin. The increase in the fly ash content decreased the cation exchange capacity of the granules. In conclusion, the recommended fly ash content is equivalent to 0.3 wt% of Al0 and the developed granules could be best suited as light-weight artificial aggregates in concrete where the additional binder would provide stabilization to decrease the leaching.

Frost-resistance prediction model for stress-damaged lightweight aggregate concrete based on BPNN: a comparative study

Frost-resistance prediction model for stress-damaged lightweight aggregate concrete based on BPNN: a comparative study

An Experimental Investigation of Light Weight Concrete Using Pumice Aggregate for Short Wall Panel Under the Application of Axial Load

The project study with the special concrete such as light weight concrete by using pumice aggregate (Natural aggregate). One of the disadvantages of conventional concrete is having high self weight. This heavy self-weight will make it to some extent an uneconomical structural material. Light weight concrete having low density reduces dead load and increase the thermal insulation. The reduction in density is produced by using it as a replacement of coarse aggregate partially in concrete. In this Study an attempt has been made to find the compressive strength of light weight aggregate concrete using mix M25 with poly carboxyl ether admixture under the application of axial load on short wall panel. Light weight concrete is made by replacement of Coarse Aggregate of Pumice aggregates.

Characterization of heat-processed artificial lightweight aggregates from polyethylene terephthalate plastic waste

Plastic waste is an undeniable source of pollution that threatens the existence of the earth’s flora and fauna. The bulk of plastic waste generated globally does not go through the proper methods of disposal but is carelessly discarded into the aquatic or terrestrial environment. Current recycling efforts are largely inadequate and disposal in landfills is still fraught with environmental and land use challenges. The proper disposal of plastic waste, as well as mitigating the environmental, social, and health impacts of extracting natural aggregates can be achieved by incorporating plastic waste as aggregates in the construction industry. This paper presents a characterization of aggregates manufactured from polyethylene terephthalate plastic waste using thermal/mechanical methods. From the cost analysis, 24,341.67 Ugx (6.09 USD) was spent to produce 1 kg of PET aggregates. Morphological, intrinsic and mechanical characteristics of the produced aggregates were established using standard procedures and equipment. The results of morphological characterization indicate an irregular shaped aggregate with smooth surface, a dense graded aggregate with a fineness modulus of 4.25, flakiness index of 26%, elongation index of 16% and particle index of 13. Intrinsic characterization yielded particle density of 1330 kg/m3, bulk density of coarse aggregates of 715 kg/m3 and water absorption of 0.445%. Mechanical characteristics of aggregates were evaluated, with compressive strength of 50Mpa, Aggregate Crushing Value of 37%, Ten Percent Fines Value of 71KN, Aggregate Impact Value of 24% and Aggregate Abrasion Value of 20%. The characteristics of PET aggregates confirm their suitability for application in structural lightweight concrete and rigid pavement. The produced PET aggregates can be considered in mix design as a total or partial replacement of natural aggregates in concrete.

Horizontal shear behavior of self-compacting lightweight concrete composite beams with dry joints and unbonded reinforcements

This study aims to investigate the horizontal shear behavior of self-compacting lightweight concrete (SCLC) composite beams with dry joints and unbonded transverse reinforcement. For this, the experimental program included different concrete types, joints configurations, and the use of unbonded high-strength bars with varying levels of prestressing and transverse reinforcement ratios in composite beams. Two precast beams were fabricated using a match-cast method and integrated horizontally to form composite beams, utilizing unbonded transverse reinforcements. The composite beams incorporating lightweight aggregates (LWA) instead of normal weight aggregates (NWA) exhibited a decreased ultimate shear strength of 19.5 %; however, the addition of steel fibers into the mixtures mitigated this decrease, resulting in a 22.8 % increase in strength compared to mixture without steel fibers. The vertical prestressing level significantly influenced the horizontal shear behavior and failure mode of composite beams, with adequately prestressed composite beams exhibiting similar ductile behaviors to the monolithic beam. Composite beams with keyed joints exhibited higher horizontal shear strength, up to 65.3 % more than the beam with flat joint, attributed to the interlock provided by the shear keys. Increased slip between two precast beams activated the dowel action of unbonded reinforcements, effectively resisting horizontal shear. Predictions of the horizontal shear strength, as per current codes, were compared to the experimental results. The results indicate that the design approach in Eurocode 2 provides reasonable estimations of the strengths of composite beams with dry joints and unbonded reinforcements.

Moisture Impact on Static and Dynamic Modulus of Elasticity in Structural Normal-Weight Concretes.

In the case of concrete built into a structure, the static secant modulus of elasticity (Ec,s) is often estimated based on its dynamic value (Ed) measured by the ultrasonic pulse velocity method instead of direct tests carried out on drilled cores. Meanwhile, the prevailing equations applied to estimate Ec,s often overlook the impact of concrete moisture. This study aimed to elucidate the moisture impact across two normal-weight structural concretes differing in compressive strength (51.6 and 71.4 MPa). The impact of moisture content was notably more evident only for the weaker concrete, according to dynamic modulus measurements. In other cases, contrary to the literature reports and expectations, this effect turned out to be insignificant. These observations may be explained by two factors: the relatively dense and homogeneous structure of tested concretes and reduced sensitivity of Ec,s measurements to concrete moisture condition compared to Ed measurements obtained using the ultrasonic method. Additionally, established formulas to estimate Ec,s were verified. The obtained modulus results tested under different moisture conditions of normal-weight concretes were also compared with those of lightweight aggregate concretes of identical volume compositions previously obtained in a separate study.

Shear strengthening of self-compacting lightweight concrete beams with steel fibers and unbonded prestressing bars

This study aims to investigate the shear behavior of self-compacting lightweight concrete (SCLC) beams strengthened with steel fibers and unbonded prestressing bars. For this, the experimental program included the use of hooked-end steel fibers with volume fractions of 0.5 %−0.75 %, and high-strength prestressing bars with varying prestressing forces and transverse reinforcement ratios. The addition of steel fibers in SCLC significantly increased the normalized shear capacity of beams, reaching up to 2.50 times higher values, whereas the substitution of normal coarse aggregates with lightweight aggregate resulted in a decrease of up to 10.1 %. The shear strengthening of SCLC beams with unbonded prestressing bars provided a substantial increase in the ultimate shear capacity up to 2.06 times higher than that of beam without reinforcement. Increasing the prestressing force of bars effectively restrained the occurrence of critical shear cracking, consequently enhancing the shear capacity. Utilizing hybrid reinforcement with fibers and prestressing bars resulted in a transition of failure mode from shear to flexural, attributed to the improved shear capacity. For the SCLC beams reinforced with steel fibers, the shear strengths were predicted by previous prediction models. When modifier for lightweight concrete was considered, the Imam’s model most precisely predicted the shear strengths with an average vu/vn ratio of 1.00 and SD of 0.07. The fib model Code, based on the modified compression field theory, provided accurate predictions for the shear capacities of SCLC beams with unbonded prestressing bars, exhibiting an average Vu/Vn ratio of 1.00 and SD of 0.09. The fiber-resisting component was reasonably considered in the model with an average Vu/Vn ratio of 1.02 and SD of 0.07.

Using plastic waste to produce lightweight aggregate for RC structures

Using plastic waste to produce lightweight aggregate for RC structures

Dematerialization of Concrete: Meta-Analysis of Lightweight Expanded Clay Concrete for Compressive Strength

The construction industry is responsible for a significant share of global material consumption, including natural resources. Therefore, the United Nations Sustainable Development Goal 12.2 on sustainable management and efficient use of natural resources cannot be achieved without significant advances and contributions from the construction sector. Furthermore, various materials used by the construction industry contribute to the development and expansion of the LEED (Leadership in Energy and Environmental Design) system. LECA (Light Expanded Clay Aggregate) is one such material that enhances LEED performance through its key benefits, including lightness, thermal insulation, sound insulation, and fire resistance. One of the most effective methods for reducing the weight of concrete is the incorporation of lightweight aggregates, and the advantages of LECA include lessening loads and enabling reduced cross-sections, directly improving the sustainability of the built environment via reduced materials consumption. This study aims to develop a prediction model for the compressive strength of LECA-incorporated concrete through a meta-analysis. More than 140 data points were compiled through literature via 15 separate studies, and results were analyzed to conduct the meta-analysis. Moreover, an experimental program was carried out to verify the model and evaluate its accuracy in predicting compressive strength. Results from the developed model and the experimental program were in accordance with concrete having lower compressive strengths compared to those at high strength values. Likewise, more accurate results were obtained for concrete mixes that have w/b ratios of 0.5 or higher. Concrete mixes that have higher amounts of LECA by volume of concrete yielded more accurate results when using the prediction model. A sensitivity analysis was carried out to quantify the impact of several parameters on the compressive strength of LECA concrete.

Artificial lightweight aggregate made from alternative and waste raw materials, hardened using the hybrid method

Lightweight aggregates are a material used in many industries. A huge amount of this material is used in construction and architecture. For the most part, lightweight construction aggregates are obtained from natural resources such as clay raw materials that have the ability to swell at high temperatures. Resources of these clays are limited and not available everywhere. Therefore, opportunities are being sought to produce lightweight artificial aggregates that have interesting performance characteristics due to their properties. For example, special preparation techniques can reduce or increase the water absorption of such an aggregate depending on the needs and application. The production of artificial lightweight aggregate using various types of waste materials is environmentally friendly as it reduces the depletion of natural resources. Therefore, this article proposes a method of obtaining artificial lightweight aggregate consolidated using two methods: drum and dynamic granulation. Hardening was achieved using combined methods: sintering and hydration, trying to maintain the highest possible porosity. Waste materials were used, such as dust from construction rubble and residues from the processing of PET bottles, as well as clay from the Bełchatów mine as a raw material accompanying the lignite overburden. High open porosity of the aggregates was achieved, above 30%, low apparent density of 1.23 g/cm3, low leachability of approximately 250 µS. The produced lightweight aggregates could ultimately be used in green roofs.

Investigation on Properties of Pervious Concrete Containing Co-Sintering Lightweight Aggregate from Dredged Sediment and Rice Husks

The utilization of dredged sediment (DS) as a transformative material in building applications presents an ideal consumption strategy. This study endeavors to create a novel ceramsite lightweight aggregate (LWA) through the co-sintering of DS and rice husks (RHs), further integrating this LWA into the construction of pervious concrete. Results revealed that the optimum production procedure for the DS-based LWA incorporated a 21% RH addition, a sintering temperature of 1100 °C, and a sintering duration of 21 min. Notably, the optimal ceramsite LWA, denoted as SDC-H, exhibited a cylinder compressive strength of 28.02 MPa and an adsorption efficiency for Pb2+ of 94.33%. Comprehensive analysis (encompassing bulk density, cylinder compressive strength, water absorption, and the leaching concentrations of heavy metals) confirmed that SDC-H impacted the specification threshold of high-strength light aggregate derived from solid waste (T/CSTM 00548-2022). Substituting 50% of SDC-H led to a diminution in the mechanical properties but an improvement in the dynamic adsorption capacity of the innovative pervious concrete, registering a mechanical strength of 26.25 MPa and a cumulative adsorption capacity for Pb2+ of 285 mg/g. These performances of pervious concrete containing 50% SDC-H might correlate with the evolution of an interconnected and open-pore structure.

Possibilities of producing lightweight aggregates from silica-clay raw material and cellulosic waste

The subject of the work is the characterization of lightweight aggregates intended for construction using the example of silica-clay raw material from south-eastern Poland (Dylągówka-Zapady deposit). The primary objective of the research is to assess the possibility of managing the accumulated organic waste, including cellulose pulp. This storage is problematic for processing plants and local government bodies and incurs high costs annually. Therefore, based on the patent (Kukułka et al. Method of producing raw meal, dried clay granules, and fired clay granules and the production line of raw meal, dried clay granules, and baked clay granules. Patent RP no P.429284.), an attempt was made to confirm the assumptions of the technology of fired clay granules, which can be used for zootechnical, agricultural, and construction purposes. The presented work assessed the physicochemical transformations in the clay-silica raw material after adding a significant amount of cellulose waste (10%, 20%, and 30%) in the temperature range of 25–1300 °C were assessed. Thermal methods such as thermodilatometry, Hot-Stage Microscopy with image analysis (IA-HSM) and thermal DSC/TG analysis with gas analysis were used for this purpose. Based on the first method, a temperature range was established in which sintering occurs without an apparent effect of densification. Therefore, the range of 850–950 °C was used to obtain fired granules, which were tested as a material for lightweight aggregates.

Enhancing Sustainability in Construction: An Evaluation of Lightweight Concrete with Sintered Fly Ash and Waste Marble Sand

Abstract Marble waste and fly ash are industrial waste, and disposal of these wastes is a big challenge for environmental sustainability. In this study, we explore an innovative approach to sustainable construction by utilizing industrial by-products: sintered fly ash aggregate (SFA) and waste marble sand in lightweight aggregate concrete (LWAC). This study used SFA as a coarse aggregate, whereas river sand was partially replaced by waste marble sand (10–50 %). The waste marble sand modified LWAC has been investigated for mechanical and durability properties. The test related to permeability like water absorption, sorptivity, permeability, and drying shrinkage has been performed. Mercury intrusion porosimetry test was performed to validate durability results. The results indicate that 30 % of river sand can be replaced with waste marble sand as it improves the overall performance of LWAC. Our research contributes to global sustainability efforts by providing a method to reduce industrial waste through its incorporation in building materials. This study not only addresses the urgent need for environmental preservation but also offers potential enhancements in the mechanical properties of LWAC, making it a viable and eco-friendly option in the construction industry worldwide.

Preparation of carbon-negative artificial lightweight aggregates by carbonating sintered red mud (SRM): CO2 sequestration, microstructure and performance

This study investigated the possibility of employing CO2 curing for the production of cement-free artificial aggregates using low-value sintering red mud (SRM) and fly ash (FA). The effects of different curing methods (CO2 and air curing) and varying FA dosages on the properties of SRM artificial aggregates were analyzed. For SRM artificial aggregates subjected to CO2 curing, the calcium silicates depleted accompanied by precipitation of calcite and aragonite. The carbonated SRM artificial aggregates (CRAAs), exhibited a denser microstructure, with the pores of the SRM filled with carbonation products. For CRAAs with 100 wt% SRM, up to 9.67 wt% CO2 was sequestered and in turn produced calcium carbonate, which resulted in a 149.0% enhancement in crushing strength and a 29.5% reduction in water absorption compared to the similar aggregates under air curing. The introduction of FA led to an accelerated strength development in the CRAAs during subsequent air curing, which was attributed to the formation of carboaluminates as a result of the hydration between the carbonation products and aluminates derived from FA. From the perspective of environment, CRAAs was carbon-negative, with a potential reduction of up to 40.2 kg of CO2 per ton of CRAAs production, presenting a cleaner and sustainable alternative to natural aggregates. The results of the study provided a feasible solution for the effective treatment of SRM on a large scale and can be used as a reference for subsequent studies.

Development of lightweight structural concrete with artificial aggregate manufactured from local clay and solid waste materials

The partial replacement of conventional natural coarse aggregate (NCA) with artificial light weight aggregate (LWA) manufactured from local clay and solid waste to develop a lightweight aggregate concrete (LWAC) for the structural use was studied in this paper. Red clay and Savar clay were used individually with solid wastes like rice husk ash (RHA) and waste glass to produce LWA. The suitability of raw materials and LWA was evaluated by investigating various properties. The mechanical, thermal and durability properties of manufactured LWAC were explored. The results of physical, chemical, thermal and geotechnical properties revealed that Red clay is better than Savar clay for the preparation of LWA. All the physical and mechanical properties of LWA prepared from Red clay are suitable for the preparation of LWAC compared to Savar clay. The test results demonstrated that the concrete manufactured by replacing 30 % of NCA with LWA produced a concrete of lightweight properties. The compressive strength of LWAC for 7 and 28 days was observed as 28 and 48 MPa, respectively. The results of modulus of elasticity, splitting tensile strength, flexural deformation, and creep test of LWAC revealed that these mechanical properties meet the requirements for the structural concrete. The RCP test proves that chlorine permeability of LWAC is comparable with NCA. It was observed that the superior performance of LWAC can be achieved only when the optimized mix designed is followed strictly. The suitability of the replacement of natural aggregate by LWA may be helpful for Bangladesh due to the scarcity of natural coarse aggregate and reusability of solid waste materials.