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Structural lightweight concrete (SLWC) is crucial for reducing building weight, reducing structural loads, and enhancing energy efficiency through lower thermal conductivity. This study explores the effects of incorporating silica fume (SF), micro-polypropylene (micro-PP), and macro-PP fibers on the workability, thermal properties, and strength of SLWC. SF was added to all mixtures, substituting 10% of the Portland cement (PC), except for the control mixture. Macro-PP fibers were introduced alone or in combination with micro-PP fibers at volumetric ratios of 0.3% and 0.6%. The study evaluated various parameters, including slump, Vebe time, density, water absorption (WA), ultrasonic pulse velocity (UPV), thermal conductivity coefficients (k), compressive strength (CS), and splitting tensile strength (STS) across six different SLWC formulations. The results indicate that while SF negatively impacted the workability of SLWC mortars, it improved CS and STS due to the formation of calcium silicate hydrate (C-S-H) gels from SF's high pozzolanic activity. Additionally, using micro-PP fibers in combination with macro-PP fibers rather than solely macro-PP fibers enhanced the workability, CS, and STS of the SLWC samples. Although SF had a minor effect on reducing thermal conductivity, the use of macro-PP fibers alone was more effective for improving thermal properties by creating a more porous structure compared to the hybrid use of micro-PP fibers. Moreover, increasing the ratio of micro- and macro-PP fibers from 0.3% to 0.6% resulted in lower CS values but a significant increase in STS values. [ABSTRACT FROM AUTHOR]

The development of self-compacting lightweight concretes is associated with solving two conflicting tasks: achieving a structure with both high flowability and homogeneity. This study aimed to identify the technological and rheological characteristics of the flow of concrete mixtures D1400...D1600 based on hollow microspheres in comparison with heavy fine-grained D2200 concrete and to establish their structural and physico-mechanical characteristics. The study of the concrete mixtures was carried out using the slump flow test and the rotational viscometry method. The physical and mechanical properties were studied using standard methods for determining average density and flexural and compressive strength. According to the results of the research conducted, differences in the flow behaviors of concrete mixtures on dense and hollow aggregates were found. Lightweight concretes on hollow microspheres exhibited better mobility than heavy concretes. It was shown that the self-compacting coefficients of the lightweight D1400...D1600 concrete mixtures were comparable with that of the heavy D2200 concrete. The rheological curves described by the Ostwald–de Waele equation showed a dilatant flow behavior of the D1400 concrete mixtures, regardless of the ratio of quartz powder to fractionated sand. For D1500 and D1600, the dilatant flow behavior changed to pseudoplastic, with a ratio of quartz powder to fractional sand of 25/75. The studied compositions of lightweight concrete can be described as homogeneous at any ratio of quartz powder to fractional sand. It was shown that concrete mixtures with a pronounced dilatant flow character had higher resistance to segregation. The value of the ratio of quartz powder to fractional sand had a statistically insignificant effect on the average density of the studied concretes. However, the flexural and compressive strengths varied significantly more in heavy concretes (up to 38%) than in lightweight concretes (up to 18%) when this factor was varied. The specific strength of lightweight and heavy concrete compositions with a ratio of quartz powder to fractional sand of 0/100 had close values in the range of 20.4...22.9 MPa, and increasing the share of quartz powder increased the difference between compositions of different densities. [ABSTRACT FROM AUTHOR]

In spite of the demonstrated efficacy of basalt stone powder as a cost-effective and readily available additive in enhancing the mechanical properties and durability of ordinary-weight concrete, its application in Structural Lightweight Concrete (SLWC) remains unexplored. This study introduced a mixing design for SLWC incorporating Light Expanded Clay Aggregates (LECAs) and basalt stone powder with a subsequent evaluation of its strength and durability characteristics. The experimental procedure involved creating various samples, considering differing proportions of cement, water, basalt stone powder, sand, LECA, superplasticizer, and aerating agent. The compressive strength and density of the 28-day-cured concrete specimens were determined. An optimal SLWC with a compressive strength of 42 MPa and a density of 1715 kg/m3 was identified. The flexural and tensile strength of the optimal SLWC exceeded those of ordinary-weight concrete by 6% and 3%, respectively. Further evaluation revealed that the optimal SLWC exhibited 1.46% water absorption and an electrical resistivity of 139.8 Ohm.m. Notably, the high porosity of LECA contributed to the low durability of SLWC. To address this, cost-effective external coatings of emulsion and fiberglass were applied to enhance the durability of the SLWC. Four coating scenarios, including one-layer bitumen, two-layer bitumen, three-layer bitumen, and three-layer bitumen with fiberglass, were investigated. The measurements of electrical resistance and compressive strength revealed that the use of three layers of emulsion bitumen and fiberglass improved the durability of the concrete by over 90% when the SLWC was exposed to severe chloride attack. Consequently, the durability of the SLWC with an external coating surpassed that of ordinary-weight concrete. [ABSTRACT FROM AUTHOR]

The primary goal of engineering design of buildings is to reduce the weight of the structure and its resistance to earthquakes and explosions because the occurrence of these events is inevitable. In this research, lightweight concrete has been used due to its unique advantages in weight reduction, and attention has also been paid to increasing the resistance and behavior of this concrete in the face of any type of accident and investigating its static and dynamic behavior. The dynamic behavior of concrete has been studied by using Hopkinson compression machine at three strain rates of 100, 200 and 300/s. Static and dynamic properties of concrete include compressive strength, modulus of elasticity, and dynamic increase modulus. For this purpose, a study has been conducted on 8 mixing designs for samples without metal fibers and nanosilica and samples containing different percentages of nanosilica and metal fibers. The results have shown that nanosilica and metal fibers play a role in improving compressive strength and the best results are obtained by adding 3% nanosilica and 1% metal fibers. Nanoparticles are more effective in static loads because the pozzolanic interactions of nanosilica improves the microstructure, and in dynamic loads, nanoparticles are less efficient due to nano's sensitivity to high loads, and also metal fibers prevent cracks in concrete. In this study, a mathematical relationship for the dynamic increase coefficient has also been extracted and compared with the experimental results. [ABSTRACT FROM AUTHOR]

Plastic is a widely consumed material with a high decomposition time, occupying significant space in landfills and dumps. Thus, strategies to reuse plastic waste are imperative for environmental benefit. Plastic waste is a promising eco-friendly building material for cement-based composites due to its reduced specific gravity and thermal conductivity. However, this waste reduces the composites' mechanical strength. This work aims to produce and evaluate lightweight concretes made with only lightweight aggregates and mostly recycled plastic aggregates. Initially, an optimized dosage approach for lightweight concrete is presented. The mixture proportion of the lightweight concrete was based on the performance of mortars with the complete replacement of natural aggregate by recycled polyethylene terephthalate (PET) aggregates. The PET aggregates showed irregular shapes, impairing workability and providing lightweight concretes with around 18% water absorption and 21% void index. However, the concretes presented significantly low-unit weight, approximately 1200 kg/m3. This work presented a structural lightweight concrete (ACI 213-R) using only lightweight aggregates and mostly plastic waste aggregate, with a compressive strength of up to 17.6 MPa, a unit weight of 1282 kg/m3, and an efficiency factor of 12.3 MPa·cm3/g. The study shows that with an optimum dosage, reusing plastic waste in concrete is a viable alternative contributing to environmental sustainability. [ABSTRACT FROM AUTHOR]

Nanotechnology has made significant inroads across various sectors, augmenting properties and economic impacts. Its pivotal role extends notably to the realm of construction and building. This study focuses on the tangible consequences of incorporating nano-silica (NS) into lightweight concrete (LWC) and its influence on mechanical attributes. The primary aim is to illustrate how NS impacts the mechanical properties of LWC, specifically its effects on compressive strength, flexural strength, and tensile strength in comparison to conventional LWC. The research encompassed the casting and examination of seven distinct concrete mixtures, including a reference mix, in laboratory settings. The study findings highlight that the utilization of lightweight Iraqi porcelanite stone resulted in a one-third reduction in the weight of standard concrete. Furthermore, the introduction of varying quantities of NS into structural LWC yielded enhancements in compressive, tensile, and flexural strength when contrasted with the reference mix, albeit at the expense of workability. Remarkably, The results showed an introduction of varying quantities of NS into structural LWC yielded enhancements in compressive, tensile, and flexural strength when contrasted with the reference mix, albeit at the expense of workability. The findings demonstrated that when doses of 1, 3, 5, 10, 15, and 20% NS were applied, the rate of three models for determining compressive strength at 90 days old rose by 19, 45, 62, 32, 15, and 37%, respectively. On the other hand, when dosages 1, 3, 5, 10, 15, and 20% were added, the percentage of improvement in tensile strength at 28 days of age was 77, 75, 84, 51, 55, and 53%. Additionally, while employing the same above doses, the bending strength at 28 days of age improved by 141, 140, 171, 115, 114, and 108%, respectively. Remarkably, the results also underscored the sustained efficacy of NS, particularly during the later stages of concrete maturation.

Structural lightweight concrete (SLWC) is crucial for reducing building weight, reducing structural loads, and enhancing energy efficiency through lower thermal conductivity. This study explores the effects of incorporating silica fume (SF), micro-polypropylene (micro-PP), and macro-PP fibers on the workability, thermal properties, and strength of SLWC. SF was added to all mixtures, substituting 10% of the Portland cement (PC), except for the control mixture. Macro-PP fibers were introduced alone or in combination with micro-PP fibers at volumetric ratios of 0.3% and 0.6%. The study evaluated various parameters, including slump, Vebe time, density, water absorption (WA), ultrasonic pulse velocity (UPV), thermal conductivity coefficients (k), compressive strength (CS), and splitting tensile strength (STS) across six different SLWC formulations. The results indicate that while SF negatively impacted the workability of SLWC mortars, it improved CS and STS due to the formation of calcium silicate hydrate (C-S-H) gels from SF’s high pozzolanic activity. Additionally, using micro-PP fibers in combination with macro-PP fibers rather than solely macro-PP fibers enhanced the workability, CS, and STS of the SLWC samples. Although SF had a minor effect on reducing thermal conductivity, the use of macro-PP fibers alone was more effective for improving thermal properties by creating a more porous structure compared to the hybrid use of micro-PP fibers. Moreover, increasing the ratio of micro- and macro-PP fibers from 0.3% to 0.6% resulted in lower CS values but a significant increase in STS values.

The development of self-compacting lightweight concretes is associated with solving two conflicting tasks: achieving a structure with both high flowability and homogeneity. This study aimed to identify the technological and rheological characteristics of the flow of concrete mixtures D1400…D1600 based on hollow microspheres in comparison with heavy fine-grained D2200 concrete and to establish their structural and physico-mechanical characteristics. The study of the concrete mixtures was carried out using the slump flow test and the rotational viscometry method. The physical and mechanical properties were studied using standard methods for determining average density and flexural and compressive strength. According to the results of the research conducted, differences in the flow behaviors of concrete mixtures on dense and hollow aggregates were found. Lightweight concretes on hollow microspheres exhibited better mobility than heavy concretes. It was shown that the self-compacting coefficients of the lightweight D1400...D1600 concrete mixtures were comparable with that of the heavy D2200 concrete. The rheological curves described by the Ostwald–de Waele equation showed a dilatant flow behavior of the D1400 concrete mixtures, regardless of the ratio of quartz powder to fractionated sand. For D1500 and D1600, the dilatant flow behavior changed to pseudoplastic, with a ratio of quartz powder to fractional sand of 25/75. The studied compositions of lightweight concrete can be described as homogeneous at any ratio of quartz powder to fractional sand. It was shown that concrete mixtures with a pronounced dilatant flow character had higher resistance to segregation. The value of the ratio of quartz powder to fractional sand had a statistically insignificant effect on the average density of the studied concretes. However, the flexural and compressive strengths varied significantly more in heavy concretes (up to 38%) than in lightweight concretes (up to 18%) when this factor was varied. The specific strength of lightweight and heavy concrete compositions with a ratio of quartz powder to fractional sand of 0/100 had close values in the range of 20.4...22.9 MPa, and increasing the share of quartz powder increased the difference between compositions of different densities.

In this study, LC30 structural lightweight concrete and LC60 high performance structural lightweight concrete were produced by using completely pumice aggregate. A total of 6 mixture designs were created by substituting 40% fly ash (FA) by weight into cement and adding 5.5 kg/m3 polypropylene fiber (PPF) to two different lightweight concrete designs. Flexural strength, compressive strength, total water absorption, electrical resistivity, rapid chloride ion penetrability tests were carried out on the produced concretes, and SEM-EDS analyzes were performed. As a result, lightweight structural concretes with a unit weight below 2000 kg/m3 could be produced by using 100% pumice aggregate, and LC60 high-performance lightweight concrete exhibited superior performance in all mechanical and physical tests compared to LC30 lightweight concrete. Since pumice has a porous structure, it has been confirmed by SEM images that there is a good interface between the aggregate and the matrix. [ABSTRACT FROM AUTHOR]

Producing self-compacting concrete with lightweight aggregates is a difficult task. Mixtures with a high content of expanded aggregate tend to separate. It is possible to evaluate the possibility of producing self-compacting lightweight concrete with low average density. This work presents the results of a study of self-compacting lightweight concrete on hollow microspheres. The ability of a lightweight concrete mixture on hollow microspheres with low density (ρ = 1450 ± 25 kg/m3) to self-compact has been established. The closeness in the values of the spreading diameter before and after shaking on the table Dsp,1 → Dsp,2 confirms this. The dependences (regression equations) of mobility, coefficients of the Ostwald–Weil equation, and density and strength on the W/C ratio and plasticizer concentration for lightweight concrete with a volume content of hollow microspheres of 46.4% have been established. The limits for homogeneity of lightweight concrete mixtures on hollow microspheres are W/C ≤ 0.6 and CPl ≤ 1.0%. The dispersion of quartz sand (varying the Sp/Sf ratio) in an amount of 8.7% in the composition of lightweight concrete does not have a significant effect on the self-compaction criterion and physical and mechanical properties. Changes in the physical and mechanical properties of lightweight concrete on hollow microspheres in the selected range of varying the W/C ratio and plasticizer concentration are in the following ranges: ρ = 1403–1485 kg/m3, Rfl = 3.34–5.90 MPa, Rcom = 29.6–45.7 MPa. The presence of delamination at W/C ≥ 0.6 does not allow one to correctly establish the influence of variable factors. [ABSTRACT FROM AUTHOR]

Abstract There is growing interest in the use of recycled materials in the building sector as a way to reduce waste and improve environmental sustainability. Polyethylene terephthalate (PET) is a thermoplastic polymer that has attracted the attention of researchers due to its application in the building industry. In the recent past, many studies have reported on the application of PET aggregates in structural lightweight concrete. This paper presents a review of the findings of 20 studies conducted between 2010 and 2022 randomly. The preliminary findings highlighted include the method of production of PET aggregates and their physical/thermal properties. The review extended further to focus on the extent of incorporation, physical properties, strength properties, and durability of concrete with PET aggregates. The substitution of PET aggregates up to 20% reflected positively on the compressive strength, while tensile and flexural strength had positive responses up to 10%. Water absorption as a measure of concrete durability increased with the addition of PET aggregates. A meta-analysis of these findings was performed using hypothesis testing (t-test and f-test) to identify significant differences between the experimental outcomes of PET incorporation in concrete. Experimental procedures with greater tolerance for PET inclusion and satisfactory concrete properties were highlighted. The paper recommends the formulation of hybrid mix proportions, developed from experimental designs with noteworthy inclusion of PET aggregates and those that attained high values of desired concrete properties. Furthermore, optimization should be performed to provide robust mix designs for high-strength or lightweight concrete with PET aggregates.

In spite of the demonstrated efficacy of basalt stone powder as a cost-effective and readily available additive in enhancing the mechanical properties and durability of ordinary-weight concrete, its application in Structural Lightweight Concrete (SLWC) remains unexplored. This study introduced a mixing design for SLWC incorporating Light Expanded Clay Aggregates (LECAs) and basalt stone powder with a subsequent evaluation of its strength and durability characteristics. The experimental procedure involved creating various samples, considering differing proportions of cement, water, basalt stone powder, sand, LECA, superplasticizer, and aerating agent. The compressive strength and density of the 28-day-cured concrete specimens were determined. An optimal SLWC with a compressive strength of 42 MPa and a density of 1715 kg/m3 was identified. The flexural and tensile strength of the optimal SLWC exceeded those of ordinary-weight concrete by 6% and 3%, respectively. Further evaluation revealed that the optimal SLWC exhibited 1.46% water absorption and an electrical resistivity of 139.8 Ohm.m. Notably, the high porosity of LECA contributed to the low durability of SLWC. To address this, cost-effective external coatings of emulsion and fiberglass were applied to enhance the durability of the SLWC. Four coating scenarios, including one-layer bitumen, two-layer bitumen, three-layer bitumen, and three-layer bitumen with fiberglass, were investigated. The measurements of electrical resistance and compressive strength revealed that the use of three layers of emulsion bitumen and fiberglass improved the durability of the concrete by over 90% when the SLWC was exposed to severe chloride attack. Consequently, the durability of the SLWC with an external coating surpassed that of ordinary-weight concrete.

Because of the ever-increasing demand for lightweight concrete (LC), especially in structural applications where it is used to reduce dead load of the structure and construction costs while contributing to environmental protection thanks to decreased use of aggregates and cement, presenting optimal mixing design for preparing structural LC (SLC) is of paramount importance. In this article, application of artificial neural networks in predicting the compressive strength of SLC was investigated. For this purpose, we used some pattern recognition neural network and genetic expression programming (GEP) with experimental data from tests to predict the compressive strength of SLC. A total of 10 input parameters from the SLC mix design were utilized for predicting the compressive strength by means of a scaled conjugate gradient backpropagation algorithm in the form of a neural network. The outputs were classified into 5 strength groups of M1, M2, M3, M4 and M5. The simulation results were 98.8% accurate in classifying SLC samples under different predefined ranges of compressive strength using the confusion matrix diagram. Moreover, the cross-entropy error obtained from testing the neural network (NN) model and correlation coefficient (R2) of GEP for predicting compressive strength of the SLC were evaluated at 0.0076082 and 0.9912, respectively, indicating high accuracy of the model. Application of this model could greatly help relevant practitioners formulate SLCs with desired compressive strength. [ABSTRACT FROM AUTHOR]

There is growing interest in the use of recycled materials in the building sector as a way to reduce waste and improve environmental sustainability. Polyethylene terephthalate (PET) is a thermoplastic polymer that has attracted the attention of researchers due to its application in the building industry. In the recent past, many studies have reported on the application of PET aggregates in structural lightweight concrete. This paper presents a review of the findings of 20 studies conducted between 2010 and 2022 randomly. The preliminary findings highlighted include the method of production of PET aggregates and their physical/thermal properties. The review extended further to focus on the extent of incorporation, physical properties, strength properties, and durability of concrete with PET aggregates. The substitution of PET aggregates up to 20% reflected positively on the compressive strength, while tensile and flexural strength had positive responses up to 10%. Water absorption as a measure of concrete durability increased with the addition of PET aggregates. A meta-analysis of these findings was performed using hypothesis testing (t-test and f-test) to identify significant differences between the experimental outcomes of PET incorporation in concrete. Experimental procedures with greater tolerance for PET inclusion and satisfactory concrete properties were highlighted. The paper recommends the formulation of hybrid mix proportions, developed from experimental designs with noteworthy inclusion of PET aggregates and those that attained high values of desired concrete properties. Furthermore, optimization should be performed to provide robust mix designs for high-strength or lightweight concrete with PET aggregates. [ABSTRACT FROM AUTHOR]

Structural optimization is a broad term in the construction sector, whereby material efficiency, as well as cost effectiveness of structures, are optimized. In concrete technology, high‐performance lightweight concrete structures often represent such optimized properties, including cost‐effectiveness and ease of application, while having a lower structural dead load. Although the use of lightweight concrete is often viewed as a sustainable practice, it does not address the high use and dependance on Portland cement, which has a high ecological footprint. In this regard, this study evaluates the engineering properties of structural lightweight concrete containing expanded shale and clay, as coarse aggregate, with a high quantity of coal fly ash (class F and C). For this purpose, a total of 15 mixes have been produced and a comprehensive series of physico‐mechanical and durability tests have been conducted. Based on the results, it is found that expanded clay outperforms expanded shale in terms of physico‐mechanical and durability properties of the resulting concrete, potentially due to its lower particle size distribution (used in this study) and the resulting porosity compared to expanded shale. Nonetheless, comparable physico‐mechanical properties are achieved when expanded shale and clay are used, as a full replacement of limestone. In turn, the performance of class C fly ash is found to be better in mechanical, but lower in certain durability variables, compared to their class F companions. The result of this study is found significant and point to suitability of using expanded shale and clay in combination with high‐volume fly ash. [ABSTRACT FROM AUTHOR]

Utilization of waste crushed bricks (WCB), which are obtained from brick factories and demolition waste as coarse and fine aggregate for preparing concrete, is an adequate strategy to reuse them and save natural resources to achieve environmental sustainability. This study investigates the possibility of developing eco-friendly structural lightweight concrete (SLWC) with a 100% replacement of WCB. Different contents (5%, 10%, and 15%) of supplementary cementitious materials such as silica fume, fly ash, metakaolin, and slag as a replacement by weight of cement were investigated. The slump test, dry density, and mechanical properties (compressive, splitting tensile, and flexural strengths), as well as elevated temperature resistance and water absorption, were evaluated. Microstructure tests, including thermogravimetric analysis, X-ray diffraction and scanning electron microscopy (SEM), were performed. The performance of the developed concrete under high temperature exposure of 200 °C, 400 °C, and 600 °C was evaluated. The experimental results indicated that SLWC can be obtained using WCB as a 100% replacement of aggregate and by using 15% metakaolin and 15% silica fume as alternatives to cement, with a 39.5 and 41.5 MPa compressive strength, respectively. Incorporation of 15% slag as cement replacement exhibited the best performance after 600 °C exposure compared to other fine materials. The SEM images showed an improvement in transition zone characteristics and increased bond between coarse aggregate and cement paste.

Plastic is a widely consumed material with a high decomposition time, occupying significant space in landfills and dumps. Thus, strategies to reuse plastic waste are imperative for environmental benefit. Plastic waste is a promising eco-friendly building material for cement-based composites due to its reduced specific gravity and thermal conductivity. However, this waste reduces the composites’ mechanical strength. This work aims to produce and evaluate lightweight concretes made with only lightweight aggregates and mostly recycled plastic aggregates. Initially, an optimized dosage approach for lightweight concrete is presented. The mixture proportion of the lightweight concrete was based on the performance of mortars with the complete replacement of natural aggregate by recycled polyethylene terephthalate (PET) aggregates. The PET aggregates showed irregular shapes, impairing workability and providing lightweight concretes with around 18% water absorption and 21% void index. However, the concretes presented significantly low-unit weight, approximately 1200 kg/m3. This work presented a structural lightweight concrete (ACI 213-R) using only lightweight aggregates and mostly plastic waste aggregate, with a compressive strength of up to 17.6 MPa, a unit weight of 1282 kg/m3, and an efficiency factor of 12.3 MPa·cm3/g. The study shows that with an optimum dosage, reusing plastic waste in concrete is a viable alternative contributing to environmental sustainability.

Producing self-compacting concrete with lightweight aggregates is a difficult task. Mixtures with a high content of expanded aggregate tend to separate. It is possible to evaluate the possibility of producing self-compacting lightweight concrete with low average density. This work presents the results of a study of self-compacting lightweight concrete on hollow microspheres. The ability of a lightweight concrete mixture on hollow microspheres with low density (ρ = 1450 ± 25 kg/m3) to self-compact has been established. The closeness in the values of the spreading diameter before and after shaking on the table Dsp,1 → Dsp,2 confirms this. The dependences (regression equations) of mobility, coefficients of the Ostwald–Weil equation, and density and strength on the W/C ratio and plasticizer concentration for lightweight concrete with a volume content of hollow microspheres of 46.4% have been established. The limits for homogeneity of lightweight concrete mixtures on hollow microspheres are W/C ≤ 0.6 and CPl ≤ 1.0%. The dispersion of quartz sand (varying the Sp/Sf ratio) in an amount of 8.7% in the composition of lightweight concrete does not have a significant effect on the self-compaction criterion and physical and mechanical properties. Changes in the physical and mechanical properties of lightweight concrete on hollow microspheres in the selected range of varying the W/C ratio and plasticizer concentration are in the following ranges: ρ = 1403–1485 kg/m3, Rfl = 3.34–5.90 MPa, Rcom = 29.6–45.7 MPa. The presence of delamination at W/C ≥ 0.6 does not allow one to correctly establish the influence of variable factors.

Plastic is one of the prominent solid wastes and its ineffective disposal has caused environmental issues. Previous research focused onthe replacement of aggregates with waste plastic in the concrete mix. This study focused on the utilization of waste polyethylene terephthalate (PET) plastic as a binder for construction application. The waste PET plastic was melted and mixed with different filler materials to give a homogenous and uniform mortar/concrete-like composite using different formulation ratio of 1:0, 1:1, 1:2, 1:3. The influence of the filler materials and the varying mix composition on the engineering and morphology properties of the resulting composite was investigated. The morphology of the waste plastic composite samples showed that the filler materials filled the pores present in the molten plastic, thereby reinforcing it. The results indicated that, the density, compressive strength, and water absorption increase as the content of the filler material increases. However, composites of plastic-sand, and plastic-quarry dust at ratio 1:3 gave higher compressive strength values of 20.30 and 20.10 N/mm2 respectively, which meet up with the minimum requirement of 17 N/mm2compressive strength for structural lightweight concrete as specified by ACI and BS standards. Thus, they can be adopted for structural purposes.

Ways of mitigating the menace caused by the abundance of waste plastic generated have been a global concern. Efforts are geared towards intensification of the recycling culture for circular economy. Recent studies combined waste plastic and sand to make Waste Plastic Binder (WPB) composite materials. However, sand mining operation has been associated with environmental and ecological issues. This study explores the engineering properties of waste plastic and quarry dust composite for sustainable infrastructural development. The polyethylene terephthalate type of plastic (PET) was employed, and which was melted and mixed with QD at different compositions of 1:0, 1:1, 1:2, and 1:3 respectively. The influence of the varying compositions on the morphological and engineering properties of resulting WPB composite was investigated. The scanning electron microscopy image showed that WPB composite with higher percentage of QD possess lesser pore space, and which influenced the high strength values. The findings showed P&QD 1:3 have highest compressive strength value of 20.1MPa, and which meets up with the American Concrete Institute and South African standard minimum requirement of 17MPa for structural lightweight concrete applicable for walkways, walling and water retaining structures constructions.

Combining structural lightweight concrete and self-compacting concrete advantages is a significant challenge in modern concrete technology research. The density of concrete can be reduced by using lightweight aggregate. Consequently, structural self-weight is also reduced. Porous lightweight aggregates have low compressive strength, which presents a challenge in developing high-strength structural lightweight self-compacting concrete. The strength and weight of self-compacting concrete can be enhanced to obtain a special concrete with multiple benefits. Pumice from North Sinai in Egypt was used as a locally available natural lightweight aggregate. The properties of the concrete produced were studied at fresh and hardened states in different proportions of partial replacement of dolomite with pumice to find the optimum replacement percentage. The optimum mix has a high strength of 60 MPa and 1.98 g/cm2 unit weight, which is considered structural lightweight concrete and high strength. Moreover, it has self-compacting concrete characteristics. Results showed that the workability of self-compacting concrete increased with the decrease of concrete unit weight. [ABSTRACT FROM AUTHOR]

Plastic is one of the prominent solid wastes and its ineffective disposal has caused environmental issues. Previous research focused onthe replacement of aggregates with waste plastic in the concrete mix. This study focused on the utilization of waste polyethylene terephthalate (PET) plastic as a binder for construction application. The waste PET plastic was melted and mixed with different filler materials to give a homogenous and uniform mortar/concrete-like composite using different formulation ratio of 1:0, 1:1, 1:2, 1:3. The influence of the filler materials and the varying mix composition on the engineering and morphology properties of the resulting composite was investigated. The morphology of the waste plastic composite samples showed that the filler materials filled the pores present in the molten plastic, thereby reinforcing it. The results indicated that, the density, compressive strength, and water absorption increase as the content of the filler material increases. However, composites of plastic-sand, and plastic-quarry dust at ratio 1:3 gave higher compressive strength values of 20.30 and 20.10 N/mm² respectively, which meet up with the minimum requirement of 17 N/mm²compressive strength for structural lightweight concrete as specified by ACI and BS standards. Thus, they can be adopted for structural purposes. [ABSTRACT FROM AUTHOR]

In this study, it is aimed to produce structural lightweight concrete (SLWC) containing pumice aggregate and to evaluate its contribution to energy performance. Fly ash and metakaolin were used as substitutes with cement in the production of lightweight concrete. It was also produced normal weight concrete (NWC) for comparison. The compressive strength, the unit weight and the coefficient of thermal conductivity of the concretes produced were determined in accordance with relevant standards. The unit weights of the lightweight concrete are in the range of 1880-1900 kg/m³, and the compressive strengths are between 20-27 MPa. It was observed that the thermal conductivity coefficients of the SLWCs are ranging from 0.54 to 0.63 W/mK and they decrease as the unit weights decrease. The properties of the SLWCs determined are used in the energy simulation software DesignBuilder to assess the primary energy consumption for a case study. With the use of SLWCs, it can be seen that the annual energy requirement decreases by 15% to 19% compared to NWC. In addition, when monthly heating and cooling loads are analysed, it can be seen that the SLWCs reduces the heating energy requirement significantly. However, the cooling energy needs were not significantly affected due to the type of concrete produced. [ABSTRACT FROM AUTHOR]

In the present study, the mechanical properties and the residual stress–strain behavior of lightweight concrete (LWC) containing pumice coarse aggregate and rock wool waste (consisting of mineral fibers) were explored prior to and following thermal loading. Key variables included the volume percentage of rock wool waste (0%, 2.5%, 5%, 7.5%, and 10%) and exposure temperature (20°C, 200°C, 400°C, and 600°C). Here, parameters playing a role in the compressive performance of LWC containing rock wool waste were examined. These parameters included the elastic modulus, compressive strength, strain at peak stress, ultimate strain, toughness index, stress–strain relationship, and failure mode. Then, several empirical relationships were proposed to predict different mechanical characteristics in terms of temperature and volume percentage of rock wool. Furthermore, the compressive strength, elastic modulus, and strain at peak stress values were compared to the prediction results of the ACI 216, EN 1994-1-2, ASCE, and CEB-FIP 1990 codes. The results demonstrated that the mechanical properties of the LWC specimens were degraded with temperature. The highest degradation in the temperature range under study occurred at 600°C, with around 50% and 80% drop in the compressive strength and elastic modulus, respectively. Furthermore, after exposure to 600°C, an increase of 2 to 2.8 folds occurred in the strain at peak stress and an increase of 2.6 to 3.4 folds occurred in the ultimate strain of the specimens relative to those at the ambient temperature. In the end, two stress–strain models were presented to capture the compressive performance of LWC including rock wool waste after elevated temperature exposure based on the empirical equations obtained for the mechanical characteristics. These models showed a relatively good correlation with the experimental data. [ABSTRACT FROM AUTHOR]

For the production of this lightweight concrete, expanded polystyrene (EPS) associated with expanded clay sintered lightweight aggregates were used to replace nature aggregates. Materials characterization tests were performed, as well as tests of the concrete in the fresh and hardened state. It is worth noting that the fresh tests displayed that the EPS concretes produced met the requirements of ABNT NBR 15823-1: 2017, classifying them as self-compacting. The hardened concrete tests observed the compressive strength, tensile strength, water absorption, void index, and specific mass. All concretes achieved resistances above 20 MPa, considered structural, and presented low specific mass, below 2000 kg/m3, classifying them as light concrete. Scanning electron microscopy (SEM) images allowed a better understanding of the microstructure, justifying the mechanical results obtained. The transition zone between the cement paste and the light aggregates, the number of voids in the cement paste, and the appearance of microcracks were considered. [ABSTRACT FROM AUTHOR]

Lowering the weight of concrete used in buildings and other structures has been one of the main priorities of the specialists. This will reduce the dead load and the forces involved in the structure during the earthquake. A wide range of research has been done around the world.In this work, a research on the construction of lightweight aggregates of Scoria has been used to increase the flexural strength of the beams tested in the glass fiber, as well as to reduce the use of cement, reduce the amount of pollutants in Iran, as well as increase the efficiency of concrete from zeolite and ash powder The wind has been used and the mechanical characteristics of these lightweight concrete structures, in particular the flexural behavior of lightweight structural beams, have been investigated in the laboratory environment, and the results indicate that light concrete was constructed and pressurized in Due to the presence of a network of fibers up to 3% by weight of cement and the resulting flexibility, the strain is very crisp And preventing it from breaking down and increasing the compressive strength by up to 20% and 10% of the flexural strength compared to the control sample. Addition of powdered zeolite along with ash to 15% by weight of cement has the same adhesion properties as cement to light concrete Data has increased the flexural strength by up to 15%.

Structural Lightweight Concrete (SLWC) is rarely used in Egyptian construction industry because of the unavailability of appropriate lightweight aggregates that capture its salient features. The aim of this research is to produce aggregates of low density and reasonable strength suitable for SLWC and to add new perspective for the structural lightweight concrete in the Egyptian market causing a reflection on the ECP 203 by adding limitations concerning the lightweight aggregates, as the only limitation for lightweight concrete is to install it for architecture uses. In this paper, an innovative procedure for producing SLWC using locally Manufactured Porous Basalt Aggregates (MPBA) is presented as a side product to basalt fiber industry. The scope of work is an experimental investigation to produce the MPBA then examine the feasibility to obtain SLWC. The physical and mechanical properties of Parent Basalt Rocks (PBR) are calibrated then the methodology of producing MPBA is explained and the obtained properties are assessed. The new MPBA is produced when solid basalt is melted and mixed with polypropylene through an established optimum mixing. The newly proposed process includes a sequence of temperature variations using both methods the Rheocasting and Thixocasting process. The phase diagram is illustrated showing the melting point of the basalt rocks and the MPBA. The produced MPBA is further used for SLWC mixes and the presented data provide the possible properties needed to figure out a new material. [ABSTRACT FROM AUTHOR]

[Display omitted] • Typical coarse aggregate was entirely replaced by waste rubber to produce lightweight concrete. • A casting method was introduced to improve microstructure, thermal and coronation property. • Varying rubber sizes and steel fibers were applied to improve the microstructure of concrete. • Thermal conductivity of lightweight concrete was considerably improved than control samples. • The Compression technique enhanced the carbonation resistivity of lightweight concrete. An all-encompassing effort has been performed to utilize waste tire rubber particles for replacing binders and conventional aggregates in concrete, and very little work has been found in the current literature on structural lightweight concrete (SLWC) for the complete replacement of traditional aggregates by waste tire rubber. Notably, there is no available study addressing the microstructure, thermal performance, and carbonation resistance of SLWC with 100 % waste coarser rubber content. Therefore, this study investigated the thermal conductivity, carbonation, X-ray CT scan, and extensive microstructural properties of novel structural lightweight concrete (SLWC) with 100 % waste rubber to substitute conventional aggregate for the first time. Different variables, such as large and smaller rubber particles, normal and compressed samples, and steel fibers, were introduced. Maximum compressive strength of 18 MPa with a density of 2115 kg/m3 satisfied the prerequisite for SLWC prescribed by ACI 213R. Non-destructive tests, including electrical resistivity and ultra-pulse velocity tests, were conducted to identify the soundness of concrete. The microstructural properties, i.e., energy dispersive spectroscopy, scanning electron microscopy, and X-ray CT scan, were evaluated to demonstrate the effectiveness of the novel casting method. The thermal conductivity of 0.29 W/m.k indicated excellent thermal insulation performance of SLWC, denoted by ASTM C332. Carbonation resistance was also considerably improved. The results show that the SLWC in this study has excellent potential for both structural and non-structural applications. [ABSTRACT FROM AUTHOR]

The aim of the current research is to determine the multiple influences of the amount of metakaolin and high temperature on the compressive strength of structural lightweight concrete (SLWC) applying response surface method (RSM). For this purpose, the lightweight concrete specimens were produced by pumice sand, and metakaolin replacing with cement at different ratios. The unit weight of hardened concrete, 28-day compressive strength, elevated temperature, ultrasonic pulse velocity, and sorptivity tests were performed. Moreover, then, two variables defined as the elevated temperature of 20, 400, 600, and 800 °C, and the metakaolin-to-cement ratio of 0%, 5%, 11%, 18%, and 25%, to obtain the compressive strength of structural lightweight concrete. The effects of each variable on the response which is the compressive strength were determined following the ANOVA (analysis of variation) analysis, and the equation of the model was developed. Eventually, the developed equation could be utilized to estimate the compressive strength of the structural lightweight concrete for requested values of each variable. [ABSTRACT FROM AUTHOR]

In this paper, Structural Lightweight Concrete (SLC) containing Recycled Lightweight Aggregate (RLA) is described. Damaged lightweight concrete was used as RLA by crushing it into fine particles, and used to replace fine limestone aggregate of up to 45% by weight. To enhance the strength development of SLC, silica fume and a superplasticizer were incorporated into the mixture. The compressive strength, density, water absorption, porosity, modulus of elasticity, and thermal conductivity of the concrete were tested. The results show that SLC with satisfactory 28-day compressive strengths of between 16.5 and 30.5 MPa, and densities of between 1600 and 1800 kg/m3, were obtained. The compressive strength, modulus of elasticity, and thermal conductivity decreased with an increase in RLA content, and the water absorption and porosity increased. Water absorption of 3.28-7.87%, porosity of 6.82-13.87%, modulus of elasticity of 16.5-25.2 GPa, and thermal conductivity of 0.49-0.75 W/mK were found to be within the working range of SLC. [ABSTRACT FROM AUTHOR]

Nowadays, the use of different waste fibers in concrete has started to increase rapidly due to some reasons such as economic savings and positive effects on the environment. In this study, waste steel wires taken from reinforcement and formwork which were previously utilized in construction projects, were employed in structural lightweight concrete (SLWC). The objective was to investigate the possibility of using this type of fiber as reinforcement in the SLWC. Compressive, tensile, flexural and impact tests were performed for investigating the mechanical properties of 28-day reinforced lightweight concrete specimens with the waste wires. The percentage of wire in the fiber reinforced concrete (FRC) was 0.25%, 0.5% and 0.75% in the volume fraction of the concrete. According to the results, by using waste wires, flexural, tensile and impact characteristics of SLWC were effectively improved. Moreover, it was concluded that waste steel wires could be used as a suitable micro reinforcement in the SLWC.

In this paper, the mechanical and physical properties such as strength, water absorption, type of curing, failure mode and microstructure of expanded polystyrene (EPS) structural lightweight concretes modified by Micro-silica and Nano-silica were investigated. In the specimens without EPS beads, replacement of Micro-silica and Nano-silica up to 15 and 3 wt% of cement, respectively, led to compressive strength increase and water absorption decrease, and after that, these trends were vice versa. These amounts for the concretes containing EPS were 10 and 2%, respectively. By replacing nearly each 5% of Micro-silica or each 1% of Nano-silica, the compressive strength increased by approximately 10 to 15% and water absorption decreased by approximately 15 to 20%. By adding Micro-silica and Nano-silica to the concretes containing EPS beads, proper adhesion between the EPS beads and other concrete components was created as confirmed by the SEM images of the specimens. Also the effects of three curing methods with water, limewater and steam on the strength and water absorption of concretes were investigated. The findings showed that 28-day limewater and 1-day steam curing resulted in the highest strength and the lowest water absorption compared to other curing methods. [ABSTRACT FROM AUTHOR]

The paper presents the results of a study of the physical-mechanical and operational properties of high-strength lightweight concrete and the influence of nanoscale modifier on these properties. The nano-modifier and its method of application to improve the properties of lightweight concrete with hollow microspheres at 10-25% are proposed. The method to control structure formation processes by the nano-modification is shown. The nanoscale modifier is grafted onto the surface of the hollow filler and interacts with cement and its hydration products (calcium hydroxide). This local activation of the hydration of Portland cement and the formation of an additional amount of calcium hydrosilicates at the phase boundary leads to the increasing of the strength of the concrete. This provides growth of operational properties. The high-strength lightweight concrete with an average density less than 1500 kg/m3 is characterized by a strength more than 40 MPa (specific strength Rsp > 30 MPa). The optimum range of concentrations of the precursor for preparation of nano-modifier is defined to be 1.25 ≤ [Na+]/[Cl−] ≤ 2.5. We can conclude that the developed composition has a dense and strong structure which can resist intense cracking. Application of nanoscale modifier enables an increase of the elastic modulus of 13-36% (equal to 6.2-8.5 GPa depending on the average density), a decrease of water absorption (to 1%) and an improvement of the water resistance (coefficient of water resistance is more than 0.95) and freeze-thaw resistance (up to F300). The nano-modified high-strength lightweight concrete has beneficial values of heat-conduction coefficient (0.48-0.70 W/(m · °C)), temperature conductivity coefficient ((3.43-4.04)·10−7 m2/s) and specific heat capacity (1080-1175 J/(kg · °C)). It allows us to consider this concrete as a multifunctional material with both structural and thermal insulation properties. [ABSTRACT FROM AUTHOR]

This paper addresses the prediction of the carbonation-induced corrosion service life of structural lightweight aggregate concrete (SLWAC) by means of a performance-based approach. Abacuses for the prediction of the service life of SLWAC as a function of the w/c ratio are presented. Limiting values of concrete composition for different carbonation exposure classes are prescribed for an intended service life of at least 50 years. The results reveal that even when pastes of low-to-moderate quality are considered, the carbonation-induced corrosion should not be the mechanism determining the service life of SLWAC structures, as long as appropriate thicknesses of concrete cover are adopted. [ABSTRACT FROM AUTHOR]

Oil palm shell (or palm kernel shell) and oil-palm-boiler clinker are two solid wastes from palm oil industry in tropical region. They can be used as aggregate in concrete mixture. Lightweight aggregate concrete with high strength was successfully produced using oil palm shell as coarse lightweight aggregate. However, lightweight concretes containing oil palm shell with normal and high strengths have relatively high drying shrinkage at early and later ages. This study is an effort to reduce drying shrinkage of oil palm shell lightweight concrete. It was found from previous studies that increasing the volume of oil palm shell in concrete increased its drying shrinkage. Therefore, one method to reduce the drying shrinkage is the reduction of oil palm shell volume by substituting this aggregate with another type of aggregate. For this purpose, comprehensive experimental study was carried out to investigate the effect of partial replacement of oil palm shell with oil-palm-boiler clinker aggregate on the shrinkage behaviour of this type of lightweight concrete. Two sets of concrete mixes were designed in this study. In the first set, oil palm shell was replaced with oil-palm-boiler clinker from 0 to 50% with interval of 10% in oil palm shell concrete with a constant water to cement ratio of 0.36. In the second set, the replacement of oil palm shell with oil-palm-boiler clinker was 30–50% with reduced water to cement ratios from 0.36 to 0.295. The influence of curing conditions on drying shrinkage of concretes was also considered. The test results indicated that partially substitutions of oil palm shell with oil-palm-boiler clinker could significantly reduce long term drying shrinkage of concrete. Contribution of oil-palm-boiler clinker in oil palm shell concrete in the range of 30–50% significantly increased the slump of control oil palm shell concrete. Therefore, it was possible to reduce the water content of these concretes to achieve the same workability of the control mix. Reduction on water content further reduced the drying shrinkage of the concrete. Concrete specimens under 7-day moist curing showed higher drying shrinkage compared to air drying condition. [ABSTRACT FROM AUTHOR]

• Sustainable concrete was produced utilizing coarser rubber instead of natural coarse aggregate. • Two rigs were introduced to implement an innovative method of prestressing the rubber particles. • The effects of two sizes of rubber particles and steel fiber in rubberized concrete were evaluated. • Improved bondings between matrix and rubber surfaces were observed in microstructure analysis. • Preloading of fresh rubberized concrete improved compressive strength significantly. End-of-life tires are a challenging waste because of their non-biodegradable properties, high production volume, and low utilization rate. Extensive research is currently being undertaken to look for various applications of waste tire rubber in the concrete industry to improve their utilization rate and significantly increase the uptake of this waste material. However, low strength and poor bond performance between rubber aggregates and cement matrix are hindering its application in the concrete industry. This paper introduces an innovative method of prestressing the coarser rubber aggregates (RAs) to address these challenges and limitations found in the critical literature review. Two steel mould rigs were newly designed for manufacturing the rubberized concrete (RuC). Three different mix designs containing 100% replacement of conventional coarse aggregates were prepared using (i) two different sizes of rubber particles and (ii) the addition of steel fibers. Density, SEM-EDS analysis, compressive strength, splitting tensile strength, flexural strength, and modulus of elasticity were undertaken to evaluate mechanical performances. The experimental results depict that this novel preloading method can bring a maximum of 97%, 59%, and 20% increase in compressive strength, flexural and tensile strength compared to that of the normal RuC, respectively. In addition, it provides a significant improvement in the interfacial transition zone between the matrix and RAs. This study demonstrates the efficient scientific recycling procedures in manufacturing the RuC with a maximum compressive strength of 18 MPa (density of 2000 kg/m3), which can be considered structural lightweight concrete as per ACI 213R-14 and Eurocode 2 recommendations. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, the mechanical and physical properties of structural lightweight concrete (SLC) specimens produced by substituting cement with metakaolin (MK) at ratios of 5%, 10%, 15% and 20% w/w were examined, and the corrosion behavior of the reinforcing steel bars embedded in these specimens was investigated. Corrosion rates of the bars were determined by using galvanic current measurement method. Furthermore, the corrosion potential of the steel bars in these specimens was measured daily for a period of 90 d based on ASTM C876 standard test method. As a result of this study, it was found that the MK improved the mechanical and physical properties of the SLC and the 15% w/w MK addition showed the optimum contribution to the strength development. Furthermore, the use of MK in SLC specimens, as a cement replacement up to 15% w/w, improved the corrosion resistance of the specimens, while there was no positive effect when MK was added in greater ratios. The conclusions were also supported with scanning electron microscope (SEM) studies. [ABSTRACT FROM AUTHOR]

With the growing needs for resource materials and the environmental protection requirements associated with sustainable development, it has become necessary to study all the possibilities of reusing and recycling industrial wastes and by-products, especially in the field of civil engineering. In the work presented here, non-biodegradable plastic aggregates made of polyvinylchloride (PVC) waste, obtained from scrapped PVC pipes, were used in partial replacement of conventional aggregates in concrete. For this purpose, a number of laboratory prepared concrete mixes were tested, in which natural sand and coarse aggregates were partially replaced by PVC plastic waste aggregates in the proportions of 30, 50, and 70% by volume (granular classes 0/3 and 3/8). Fresh concrete mixtures were tested for workability and density, and hardened concrete specimens were used to investigate compressive strength, ultrasonic wave velocity, and resistance to chloride ion penetration. The results of the laboratory study showed that concrete made with 50 and 70% of recycled PVC aggregates fell into the category of structural lightweight concrete in terms of unit weight and strength properties. This study gave quite encouraging results and opened up a new way of recycling PVC waste as a lightweight aggregate in concrete. [ABSTRACT FROM PUBLISHER]

The crack properties and compressive strength of structural lightweight concrete including fly ash exposed to high temperature were investigated. The design of experiments was carried out by Taguchi method using a standard L18 (2¹ × 37) orthogonal array. The main parameters of experiments were selected as the percentage of fly ash, heating degree, and cement dosage. The mixes containing the three different percentages of fly ash admixtures (0%, 10% and 20%) and two cement dosages (400 kg/m³ and 500 kg/m³) were prepared. After the specimens were exposed to temperatures of 400 °C, 600 °C and 800 °C, the lengths and widths of the concrete cracks were measured using an optical microscope. Finally, the compressive strength tests were carried out. The experimental results for compressive strength, crack width and length were obtained between 5.39 and 38.75, 0.104 and 0.346, 3.48 and 8.538, respectively. The importance of the experimental parameters on compressive strength and crack characteristics was determined by using variance (Anova) method. The anova results showed that heating degree was the most significant effect on compressive strength and crack length, but the most significant effect on crack width was determined as the cement dosage. Furthermore, Taguchi results indicated that the optimum parameters for compressive strength and crack properties of structural lightweight concrete were found as 400 °C, 500 kg/m³ cement dosage and 20% fly ash. [ABSTRACT FROM AUTHOR]

In this paper, a rule based Mamdani type fuzzy logic model for prediction of slippage at maximum tensile strength and slippage at rupture of structural lightweight concretes were discussed. In the model steel rebar diameters and development lengths were used as inputs. The FL model and experimental results, the coefficient of determination R2, the Root Mean Square Error were used as evaluation criteria for comparison. It was concluded that FL was practical method for predicting slippage at maximum tensile strength and slippage at rupture of structural lightweight concretes. [ABSTRACT FROM AUTHOR]

Ways of mitigating the menace caused by the abundance of waste plastic generated have been a global concern. Efforts are geared towards intensification of the recycling culture for circular economy. Recent studies combined waste plastic and sand to make Waste Plastic Binder (WPB) composite materials. However, sand mining operation has been associated with environmental and ecological issues. This study explores the engineering properties of waste plastic and quarry dust composite for sustainable infrastructural development. The polyethylene terephthalate type of plastic (PET) was employed, and which was melted and mixed with QD at different compositions of 1:0, 1:1, 1:2, and 1:3 respectively. The influence of the varying compositions on the morphological and engineering properties of resulting WPB composite was investigated. The scanning electron microscopy image showed that WPB composite with higher percentage of QD possess lesser pore space, and which influenced the high strength values. The findings showed P&QD 1:3 have highest compressive strength value of 20.1MPa, and which meets up with the American Concrete Institute and South African standard minimum requirement of 17MPa for structural lightweight concrete applicable for walkways, walling and water retaining structures constructions., Competing Interests: The authors declare no conflict of interest., (© 2022 The Authors.)

This paper investigates bond behavior of structural lightweight concrete (SLWC) and ordinary concrete (OC) comparatively using bending test called Standard Belgium Hinged Beam Test (SBHBT). For this purpose the experiments were carried out as three series on 36 beam specimens (12 specimens of SLWC and OC with 200 development length, 12 specimens of SLWC with 25ϕ development length). For each series bond behavior of steel rebars with 8, 10, 12, 14 mm diameters were tested. The results indicate that bond strength of SLWC is considerable lower than OC and 20ϕ development length is insufficient for steel rebars with 12 mm and 14 mm diameters. Therefore development length of SLWC was extended to 25ϕ, even if 8 and 10 mm steel rebars provided acceptable bond strength. In this way, bond strength between SLWC and 8 and 10 mm steel rebars was developed. In addition, adequate bond behavior was achieved for 12 mm rebar but the beam in which 14 mm rebar used exceeded their bearing capacity by shear forces before yield stress. This result shows that SBHBT is more convenient for small sized steel rebars. [ABSTRACT FROM AUTHOR]

Some properties of lightweight pumice stone concrete (LWPSC) are discussed, on account of a possible structural use of this material. Then the results of an experimental investigation are described, in order to show that pumice can really be considered an alternative to common artificial lightweight aggregates, taking into account the performance pointed out by loading tests carried out on structural systems made of LWPSC. Three different kinds of reinforced wall panels were made using LWPSC, lightweight expanded clay concrete and normal weight concrete; then their structural responses under horizontal cyclic and constant vertical forces were compared, above all with reference to lateral stiffness, cracking pattern, ultimate strength and associated plastic deformations. This comparison shows the effectiveness of pumice as an aggregate in manufacturing concrete, at least for this type of structural element. [Copyright &y& Elsevier]