High-performance Construction Materials Research Articles

Alkali activated steel slag – oil composites: Towards resource efficiency and CO2 neutrality

This study describes advances in high-performance construction material development using a minimum of primary resources while enabling simultaneous CO2 sequestration capacities. Two so far unutilized Austrian steel slags were combined with metakaolin and vegetable oil to produce alkali-activated materials exhibiting high compressive and flexural strength of up to 94 MPa and 13 MPa, respectively. This approach enabled a reduction in primary mineral resources of up to 82 wt%, with an average reduction in global warming potential (GWP) of 52 % compared to a traditional high-performance Portland cement material. Oil addition led to the formation of mainly water unsolvable metal soap phases precipitating within the pore spaces without significantly altering the phase assemblage and chemistry of the binder matrix, but further reducing the GWP by 74 %. The (heavy metal) leaching behavior coincides with that of traditional concrete materials and was even further reduced by the addition of oil.

Multi-response optimization of thermally efficient RC-based geopolymer binder using response surface methodology approach

This research addresses the persistent challenge of strength degradation in geopolymer-based materials incorporating rubber crumb (RC). An optimization model was developed, focusing on critical variables such as RC grade (particle size), percentage incorporation, and the molarity of NaOH, using slags as alumina-silicate precursors. Response surface methodology (RSM) was employed for experimental design and statistical modelling to predict the strengths and thermal conductivity of the resulting geopolymer. The study meticulously analyzed the influence of each parameter on the performance of RC-based geopolymers to understand their practical implications. The models generated were highly significant, demonstrating high practicability and minimal errors. The optimization revealed that a geopolymer with the highest strength (41.91 MPa) and lowest thermal conductivity (0.504 W/mK) can be achieved using a molarity of 10, grade 20 RC, and 18.5% RC content. This study highlights the potential of optimizing RC-based geopolymer mixes to enhance material performance, promoting the sustainable use of waste tires and advancing the development of high-performance construction materials.

Understanding the synergistic geopolymerization mechanism of multiple solid wastes in ternary geopolymers

The use of ground granulated blast furnace slag (GBFS), fly ash (FA) and steel slag (SS) to form ternary geopolymers consumes several industrial solid wastes and produces high-performance construction materials. However, the unexplored synergistic geopolymerization mechanism of multiple solid wastes limits the design of high-performance ternary geopolymers. This study investigated the synergistic mechanism through testing the macroscopic performances such as unconfined compressive strength (UCS), final setting time (FST) and fluidity, and characterizing the microscopic structure of ternary geopolymers with different mixture proportions. In addition, the influence of variables on strength development of ternary geopolymers is analyzed by developing machine learning models. Results reveal that the highest strength of ternary geopolymers was achieved at a ratio of FA to GBFS to SS of 3:5:2, and alkali activator to precursor materials of 0.08. Addition of 20 % SS refines the pore network, reducing cumulative and detrimental pore volumes, thus enhancing compressive strength. In addition, the SS addition extends the heat generation peak during geopolymerization due to its slower reaction kinetics. Material components (Na/Al, Si/Al, Ca/Si) have a significant influence on UCS, with Na/Al ratio being the most sensitive variable. The study provides a new approach for utilization of bulk industrial wastes.

Analysis of Strength and Bond Behaviour of Bacterial Concrete

Incorporating bacterial activity within concrete holds promise for enhancing its mechanical and durability characteristics. This research delves into assessing bacterial concrete's strength and adhesion behavior, investigating the synergistic effects of bacterial activity. Scientific inquiry has confirmed the effectiveness of Bacillus species as microbial agents in augmenting concrete's self repair capabilities. Bacillus Subtilis is employed for sample preparation, with a concentration of 105 cells per millilitre chosen as the parameter. The mechanical properties of bacterial concrete are analyzed, considering the impact of bacterial strains on these properties. The study also focuses on evaluating the bonding behavior of bacterial concrete through pull-out tests, aiming to assess the efficacy of bacterial activity in enhancing the bond strength of the concrete matrix. This investigation yields a comprehensive understanding of the intricate interplay of bacterial activity within concrete. The findings contribute to optimizing bacterial concentration and mix proportions for the development of sustainable and high-performance construction materials.

Experimental study and analytical modeling of tensile performance of ultra-high-performance concrete incorporating modified recycled aggregates

Incorporating recycled aggregates (RA) into Ultra-High-Performance Concrete (UHPC) is pivotal for the sustainable development of high-performance construction materials. This study investigates the enhancement of RA through two methods: low-concentration acid treatment and sodium silicate treatment, focusing on improving physical properties and microstructural integrity. Experimental designs encompassed varying types of modified RA (URA, T1RA, T2RA), RA replacement rates (0%, 25%, 50%, 100%), and two steel fiber shapes (SSF and HSF), resulting in twenty-one distinct axial tensile specimen formulations. The study reveals substantial improvements in modified RA's physical properties, effectively mitigating internal microcracks and pores. Modified RA significantly bolstered UHPC-RA's tensile strength, notably when chemically strengthened, underscoring its efficacy in enhancing RA quality. However, escalating RA content correlated with diminished mechanical indices like tensile strength and toughness, attributed to reduced specimen quality. Digital Image Correlation (DIC) accurately forecasted crack locations, highlighting the minimal influence of modified RA and fiber bridging on specimen failure modes. A comprehensive theoretical model incorporating RA deterioration and hooked steel fiber anchorage predicted tensile behaviour, offering vital insights for designing UHPC-RA systems.

Resource recovery of sludge incineration residue in lightweight aggregate: Performance mechanism, and environmental safety analysis

In response to escalating global environmental concerns and the need for sustainable waste management, this study explores the transformative potential of high-temperature sintering in converting sludge incineration residues (SIR) into lightweight aggregates. The research investigates the influence of sintering temperature and time on the physical, mechanical, and environmental characteristics of the resulting aggregates. High-strength lightweight aggregates with optimal properties are achieved at 1085 ℃ and 10 minutes, exhibiting favorable freeze-thaw resistance. Microscopic analyses reveal the presence of glassy substances in the aggregates, with higher sintering temperatures leading to increased glassy content but also more substantial pores. Importantly, high-temperature sintering significantly reduces the leaching rate of heavy metal ions. This study contributes valuable insights into the micro-characteristics and environmental safety of SIR-sintered lightweight aggregates, providing a sustainable solution for waste utilization in the development of high-performance construction materials.

Effective microorganism solution-imbued sustainable self-curing concrete: Evaluation of sorptivity, drying shrinkage and expansion

Production of various concrete elements at early ages requires careful water curing to ensure the development of a hydration reaction that fills and discontinues the capillary voids, thus achieving the desired strength of the hydrated products. In real practice, problems occur where appropriate curing is tricky to attain targeted structural components like inclined, high-rise, and thick concrete elements. To meet this goal, this study evaluated the engineering properties of some newly designed concrete incorporated with effective microorganism (EM) solutions as new self-curing agents at varying contents (5, 10, 15, 20, and 25% in place of water). The casted specimens were subjected to wet and dry curing regimes. The effects of EM solutions at various contents on the strength development, sorptivity, drying shrinkage, expansion, and microstructures of the proposed concrete were determined. The results indicated that the specimens containing 10% of EM (optimum) as water replacement achieved the highest strength (48.9 MPa) at 28 days of curing. Compared to the control sample, the permeability, drying shrinkage, and expansion of the specimen made with 10% of EM were correspondingly reduced by 2.5%, 48%, and 49%. In addition, the optimum sample displayed denser texture and gel formation with fewer voids than other specimens. The optimum specimen exhibited nearly 12% more hydration than normal concrete in water curing. It was established that an EM solution in place of water in concrete can serve as an effective self-curing agent for the sustainable growth of high-performance construction materials.

Flexural behaviour of one-part fibre-reinforced geopolymer beams

This research focuses on the structural application of one-part fibre-reinforced geopolymer composite (OP-FRGC), a pioneering low-carbon, high-performance construction material. While extensive studies have been conducted on the basic mechanical properties and mix proportions of OP-FRGC, structural applications remain underexplored. This investigation of the flexural performance of steel-reinforced OP-FRGC beams employed four-point bending tests and digital image correlation (DIC) to elucidate bending failure mechanisms. The results were then compared with those of conventional steel-reinforced concrete (RC) beams. Findings indicate that the integration of fibres in OP-FRGC effectively distributes cracks and enhances flexural toughness. Additionally, the research evaluates the predictive accuracy of existing structural codes from China, the United States, and Europe for steel-reinforced OP-FRGC beams. A comparative analysis of the carbon emissions from these structural systems underscores the environmental advantages of steel-reinforced OP-FRGC beams, highlighting their potential to reduce the carbon footprint in the construction sector.

Recycled Household Plastic and Oil Palm Filler Reinforced Epoxy Composite for Lightweight Construction Applications

Polypropylene is extensively used in aerospace, automotive and construction applications due to its versatile properties. This project aims to reduce plastic and oil palm waste and promote the development of strong, sustainable and eco-friendly construction materials. The objective of this project is to develop a sustainable yet high-performance construction material by incorporating polypropylene particles, oil palm empty fruit bunch (OPEFB) fibres and oil palm shell (OPS) particles into epoxy composites through the hand lay-up method. The composite specimens undergo ASTM D638 tensile test to determine the tensile properties. The addition of PP particles in varying weights shows decrease in tensile strength, likely due to poor dispersion and compatibility with the epoxy matrix. Incorporating 3 wt% OPEFB fibres with fibre length from 2mm to 4mm improves tensile strength by 2.32% and 23.36% respectively at higher PP particle loadings which are 15 wt% and 25 wt%. Adding 1 wt% and 3 wt% OPS particles improves the tensile strength by 2.96% and 4.68% respectively, in composites with 10 wt% PP particles and 3 wt% OPEFB fibres. The tensile performance may be improved by treating PP particles with compatibilizers such as silane or maleic anhydride grafted polypropylene.

Propriedades no estado fresco e endurecido de compósitos cimentícios com a adição de celulose nanofibrilada

Abstract Evaluating the effects of nanomaterials in cementitious systems is paramount to projecting high-performance construction materials. However, the synthesis of some nanomaterials on a large scale and their toxicity may limit their application. In this context, nanofibrillated cellulose (NFC), a biodegradable and natural material stand out. Thus, this paper aims to study the influence of NFC on the fresh, hardened properties (compressive and flexural strengths) and mineralogy of cementitious systems. The results indicated that incorporating up 0.075 wt.% to CNF reduced the spread of cement pastes by up to 14.0%. A CNF content of 0.025 wt.% increased the 28-d compressive and flexural strengths by 22.0% and 25.0%, respectively, compared to the control sample. The X-ray diffraction (XRD) results indicate that higher NFC contents (>0.025 wt.%) resulted in lower intensity portlandite peaks after 7 days, which may show a lower hydration degree, especially concerning the plain cement paste. These results suggest that the NFC can affect the hydration of cementitious matrices at early ages; however, it did not significantly affect the hydration degree after 28 days of hydration.

Surface modification of miscanthus fiber with hydrophobic silica aerogel for high performance bio-lightweight concrete

Bio-fiber reinforced cementitious material is now attracted widespread attention thanks to its low carbon footprint and its advantages in energy conservation in buildings. However, the main concerns of using large volume of bio-fibers in concrete is its high water absorption and the leaching of organic matter that is incompatible with cement. This study investigates a surface modification method of a bio-fiber (miscanthus) by using hydrophobic silica aerogel and further evaluates its mechanical and insulating performance in lightweight concrete and increase its compatibility with cement. X-ray diffraction, thermal gravimetry and calorimeter test were carried out to investigate the effect of hydrophobic miscanthus fibers on the microstructure of cement matrix. The results show silica aerogel modified miscanthus fiber enhances both the compressive and flexural strength, meanwhile significantly improving the insulating performance of concrete. The use of superhydrophobic aerogel particles reduces the sugar leached from miscanthus and the hydration heat peak is only slightly delayed with the incorporation of aerogel coated miscanthus fibers. The results of this study shed light on surface modifications of bio-fibers for applications in high performance construction materials.

Mechanical properties of coal ash concrete in the presence of graphene oxide

ABSTRACT Modern concrete technology places a strong emphasis on incorporating diverse resources, particularly industrial byproducts, into the concrete production process. The utilization of fly ash, a notable industrial waste, has gained increasing importance due to its potential to enhance concrete properties and provide economic advantages. In this study, we conducted experimental investigations on concrete, varying the concentrations of graphene oxide (ranging from 0.1% to 0.5%) and coal ash (at levels of 5%, 10%, and 15%). We evaluated the mechanical characteristics of concrete, including compressive strength, tensile strength, and flexural strength, by creating a total of 45 different mix specimens across 15 distinct mix formulations. Remarkably, the combination known as 4GOCA (Graphene Oxide and Coal Ash at 5%, 10%, and 15%) exhibited the highest strength, demonstrating a remarkable 65% increase compared to the reference mix. Similarly, both 2GOCA and 3GOCA demonstrated strength gains exceeding 50%. The unique aspect of this research lies in its innovative utilization of graphene oxide and coal ash in the concrete mix, showcasing the potential for sustainable and high-performance construction materials.

Localised Web Bearing Behaviour of Cold-Formed Austenitic Stainless-Steel Channels: Review of Design Rules and New Insight under Interior Loading

Stainless steels are modern high-performance construction materials exhibiting excellent corrosion resistance, recyclability, ductility, and durability which make them appealing to use in the construction industry. However, when used as structural sections, they are subjected to localised failure in the web. This study aims to examine the structural behaviour of cold-formed low-carbon content standard austenitic 304L and 316L stainless steel channels under localised interior bearing loads. The results of 21 tests on unlipped channels with different cross-section sizes and thicknesses are presented. A nonlinear quasi-static Finite Element (FE) model is then developed. The FE model is validated against experimental test results and demonstrated good agreement in terms of bearing strength and failure modes. In addition, the experimental and FE results are used to compare the results against the results predicted in accordance with the American specification SEI/ASCE 8:2002 and European Standard EN 1993-1-4:2006. It is found that the current design equations are unreliable and too unconservative to use for cold-formed austenitic stainless steel unlipped channels, especially when compared to SEI/ASCE 8:2002, as much as 41%.

Enhancing structural, thermal, and mechanical properties of Acacia pennata natural fibers through benzoyl chloride treatment for construction applications

In recent years, there has been growing interest in exploring natural fiber reinforced composites as potential alternatives to conventional materials in various structural applications. The aim of this study on Acacia pennata fibers (APFs) and treating them with benzoyl chloride was to explore their potential as reinforcement in construction-related materials. The aim was to investigate the physico-chemical, thermal, and mechanical properties of these fibers to understand their suitability for applications in concrete reinforcement, retrofitting, roofing, and wall panels. By enhancing the understanding of the treated fibers' characteristics, this study contributes to the development of sustainable and high-performance construction materials. The fibers were extracted using both water retting and chemical retting methods. The physico-chemical properties of the fibers were assessed through X-ray diffraction (XRD) analysis, which determined a calculated crystalline index (CI) of 72.14% and a crystalline size of 2.6 nm. Thermo-gravimetric analysis was conducted to evaluate the thermal stability of the APFs, revealing a temperature of 366°C and a maximum degradation temperature of 226.7°C. Mechanical analysis included measurements of the APFs' tensile strength (467.86 MPa), tensile modulus (14.62 GPa), microfibrillar angle (14.79˚), and elongation at break (3.2%). The findings derived from these analyses suggest that the APFs that underwent treatment exhibit desirable mechanical characteristics, rendering them a viable option for utilization in construction-related materials like reinforcement in concrete, retrofitting, roofing and wall Pannels. This research presents a novel exploration of Acacia pennata fibers (APFs) treated with benzoyl chloride, aiming to establish their potential as reinforcements for construction materials. While natural fiber-reinforced composites have drawn interest, the unique application of APFs in construction and their treatment with benzoyl chloride to enhance properties remain relatively unexplored in the literature. This study fills a significant gap and contributes to the advancement of sustainable and high-performance construction materials by utilizing treated APFs. The results highlight the remarkable capability of these fibers to enhance the properties of composite materials in the construction industry.

Investigation of the dispersion of reduced graphene oxide in cementitious composites under different mixing strategies

The use of reduced graphene oxide (rGO) to enhance the strength, durability, and electromagnetic properties of cementitious composites has received extensive attention in recent years. However, the agglomeration behavior of rGO in alkaline environment greatly reduces its reinforcement effect on cement-based materials. This study aims to develop a practical and feasible dispersion scheme to facilitate the practical application of rGO in cement systems. To achieve this goal, four different mixing protocols were evaluated, including the typical combination of superplasticizer and ultrasound (Methods 1), and three preparation methods involving direct dry mixing of cement clinker with rGO (Methods 2), dry mixing of sand with rGO (Methods 3), and dry mixing of sand with rGO solution (Methods 4).The mechanical and durability properties of the cement mortar samples were analyzed under different mixing protocols to determine the effects of rGO on the performance of the composite. Furthermore, the microstructure and hydration product of the cementitious composite were investigated using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) to assess the dispersion of rGO in the cement matrix. The test results indicated that the direct dry mixing of sand with rGO (Method 3) was the most effective dispersion scheme among the evaluated mixing protocols. The flexural and compressive strengths of the cement mortar samples produced using Method 3 were increased by 26.01% and 39.8%, respectively, after 28 days as compared to the control samples. This enhancement can be attributed to the shear effect of the sand grains, which effectively reduces the aggregation of rGO in the cement matrix, leading to stronger nucleation effects occurring in the cement hydration. In addition, well-dispersed rGO improves the pore structure of the composite and increases its erosion resistance. The results of this study may provide valuable insights for the large-scale production of rGO-cement composites with enhanced properties and contribute to the development of sustainable and high-performance construction materials.

Leaching and hydrating mechanisms, economic benefits of backfill materials by using coal fly ash–slag-based binder for environmentally sustainable production

Herein, the blast furnace slag (BFS), steel slag (SS), desulphurisation gypsum (DFG) and mechanically modified fly ash (MFA) were used as a coal fly ash–slag-based binder (FSD) for the solidification/stabilisation (S/S) of non-ferrous metal tailings and to prepare a coal fly ash–slag-based backfill materials (FST). The results revealed that the optimal ratio for FST was G9I-2, which consisted of 20% MFA, with an appropriate fluidity (240 mm) and setting time (13 h) that satisfied the backfill pipeline transportation requirements, and compressive strengths with 7 and 28 d curing of 2.43 and 8.47 MPa, respectively. The diffusion coefficient (Do) of FST ranged from 2.13 × 10−11 to 2.50 × 10−10 cm2/s, with a leachability index (LI) of 10.08–10.54. These values indicated that the FSD effectively encapsulated Pb and Zn by S/S, with G9I-2 exhibiting the lowest risk of leaching and the leaching mechanism of Pb and Zn was dissolution. The solidification of lead and zinc primarily occurred through the formation of hydration products such as C–(A)–S–H gel, possibly forming a complex salt phase. The addition of an appropriate amount of MFA (20 wt%) increased the content of functional hydration products (15%, ettringite; 14%, complex salt mineral phase) and the degree of polymerization. An increase in the Al/Si ratio (0.11087 ± 0.00948 ∼ 0.38838 ± 0.01935) in the gel region of G9I-2 indicated the continuous transformation from C–S–H to C–A–S–H phase. Life cycle assessment (LCA) and economic benefit analysis (EBA) demonstrated that FST materials significantly reduced CO2 emissions (0.45 kg/t) and generated significant economic benefits (2.76 USD/t) for mine backfill applications. These findings highlight the significance of MFA in achieving sustainable and high-performance construction materials, with potential applications in various construction projects.

Development of robust ultra-high-performance carbon nanofiber aggregates (UHPCNFAs) for structural health monitoring

Ultra-high-performance concrete (UHPC) is rapidly implemented to build robust, durable, and sustainable structures. This study presents the development of a robust self-sensing sensor with the motivation to monitor structures with high-performance construction material, such as UHPC. The ultra-high-performance carbon nanofiber aggregates (UHPCNFAs) are carbon nanofibers (CNFs) and UHPC-based smart aggregates. The newly developed UHPCNFAs are experimentally investigated in uniaxial compression. Sweep-frequency and fixed-frequency tests are adopted in alternating current measurements for determining the electrical behavior of the UHPCNFAs. UHPCNFAs are compressed in parallel and perpendicular loading orientations to understand the difference in the sensor's electrical sensitivity and mechanical behavior in each case. In addition, the robustness of the UHPCFNA is examined to the point of failure in both orientations. The relationship between stress, strain, and electrical impedance variation is established for eight different frequencies. Furthermore, the UHPCNFAs are compressed at a fixed frequency to verify the repeatable behavior. This paper examines the effect of loading orientations on electrical and mechanical response, robustness, and sensitivity of UHPCNFA in a wide range of frequency spectrum to check its suitability in real-time structural health monitoring.

Durability characteristics and quantification of ultra-high strength alkali-activated concrete

Clinkerless ultra-high strength concrete formulated using alkali-activated binders (AAB-UHSC) emerges as a green high-performance construction material, but its durability characteristics have not been systematically investigated yet. In this work, the resistances of AAB-UHSC against water absorption, carbonation, chloride diffusion, and chloride-induced electrochemical corrosion of steel, are quantitatively evaluated and compared with those of ordinary Portland cement (OPC)-based UHSC and normal-strength AAB (AAB-NSC) counterparts. The results show that in comparison with OPC-UHSC of similar strength of ∼150 MPa, AAB-UHSC has lower water-permeable porosity and demonstrates superior performance against water absorption and chloride ingress, but a weaker carbonation resistance. However, despite lower CO2 uptake capacity, the carbonation resistance of AAB-UHSC is about six times stronger than that of AAB-NSC, owing to its highly densified microstructure. Under the same chloride level and relative humidity conditions, the corrosion rate of steel embedded in AAB-UHSC is higher than that in OPC-UHSC, likely due to its higher moisture content and [Cl−]/[OH−] ratio that expedite steel dissolution. Moreover, the incorporation of steel fibers has limited influence on the transport-related durability performance of AAB-UHSC, implying a densified interfacial zone between steel fibers and AAB-UHSC matrices.

A state-of-the-art review on mechanical performance characterization and modelling of high-performance textile reinforced concretes

• A detailed discussion on the constituents and design parameters of TRC is presented. • The mechanical properties of TRC are critically reviewed under various loading conditions. • The fracture mechanisms and modes under different loadings are discussed. • The outcome of the review highlights the research gap and perspective of TRC. Textile reinforced concrete (TRC) is becoming an emerging high-performance construction material due to its outstanding load-bearing capacity, corrosion resistance, and durability. However, the influences of textile type and design parameters on the mechanical performance of TRC have not been fully understood. Therefore, this study aims to enhance the understanding of the mechanical performance of TRC and identify further research needs. The tensile, compressive, and flexural performances of TRC are first discussed based on the literature review. It is found that the mechanical properties of TRC are highly dependent on the shape, geometry, woven type, and yarn properties of the textile. The failure patterns of TRC under tensile and flexural loadings generally include three stages: linear elastic (before the first crack), strain hardening (with multiple cracking), and softening (with fracture failure). The bonding performance of the textile embedded in the cementitious matrix is also reviewed using the pullout test results. The geometric parameters and surface characteristics of the textile significantly affect the interfacial bonding strength. Currently, the analytical models for the mechanical analysis of TRC and the numerical analysis for the 2D and 3D textile-reinforced concrete are available to predict their mechanical behaviours. This study can provide a valuable reference for further investigations on TRC materials and promote their applications in civil engineering.

High-Performance Construction Materials: Latest Advances and Prospects

Our civilization has used construction materials extensively, especially for infrastructure projects [...]