Structural Building Materials Research Articles

Design strategy of super tough hydrophobic bamboo framework composites with internal network entanglement reinforcing structure

The low strength and high hygroscopicity of natural bamboo limit its use in structural building materials. Herein, lignin and hemicellulose were partially removed from natural bamboo in order to create bamboo frameworks featuring well-aligned bamboo fibers. Subsequently, these bamboo frameworks (BF) are infused with epoxy resin (EP) modified with PDMS and subjected to hot-pressing to fabricate bamboo-epoxy composites (PDMS-EP/BF). The incorporation of flexible PDMS chains facilitated intermolecular chain entanglement, which inhibited crack propagation and improved the bonding between bamboo and EP. The findings of the research indicated that the PDMS-EP/BF composites exhibited a significant enhancement in flexural strength by 98%, modulus of elasticity by 129%, toughness by 399%, and tensile strength by 177% when compared to natural bamboo. Additionally, the modification led to a decrease in the surface energy of the composites, resulting in increased hydrostatic contact angle and imparting water repellency to the material. Compared to natural bamboo, PDMS-EP/BF has 309% higher water contact angle and 143% lower surface energy. In addition, large composites have been prepared and their interface strength was tested. The findings of the study offer insights into the potential enhancement of bamboo composites to achieve increased flexural strength, modulus, and toughness. This could expand the utilization and significance of bamboo in the realm of construction materials.

ОСОБЛИВОСТІ ОЦІНЮВАННЯ ТЕХНОЛОГІЧНОЇ ПОШКОДЖЕНОСТІ БЕТОНУ

The article deals with the issue of obtaining building materials and equipment with specified quality parameters with reduced material consumption. It is shown that one of the possible ways to reduce the material density of structural building materials is the use of fillers. In this article, considering concrete as a structural material, it is stated that it is the formation of the structure or product that is difficult to control its quantitative and qualitative parameters, but it is practically possible only after receiving the finished product or structure. Properties of the structure are determined as individual properties of all subsystems (concrete, reinforcement), and changes in these properties during structural interactions. In turn, the construction material (concrete) is a subsystem that consists of characteristic structural inhomogeneities. Since the composition of concrete affects the structure, strength characteristics and deformable properties of reinforced concrete structures operating under the influence of external influences, there is a need for a more thorough study of it and the determination of optimal components in order to ensure the operational reliability of structures. During the technological processing of concrete into products, at all levels of structural in homogeneities in the material, technological cracks appear, which, being the structural parameters of concrete, determine the damage of structures, and thus their operational reliability. Research has established that technological damage significantly affects the strength and deformation properties of concrete.

Biomimetic Approach for Enhanced Mechanical Properties and Stability of Self-Mineralized Calcium Phosphate Dibasic–Sodium Alginate–Gelatine Hydrogel as Bone Replacement and Structural Building Material

Mineralized materials are gaining increased interest recently in a number of fields, especially in bone tissue engineering as bone replacement materials as well as in the architecture-built environment as structural building materials. Until the moment, there has not been a unified sustainable approach that addresses this multi-scale application objective by developing a self-mineralized material with minimum consumption of materials and processes. Thus, in the current study, a hydrogel developed from sodium alginate, gelatine, and calcium phosphate dibasic (CPDB) was optimized in terms of rheological properties and mineralization capacity through the formation of hydroxyapatite crystals. The hydrogel composition process adopted a three-stage, thermally induced chemical cross-linking to achieve a stable and enhanced hydrogel. The 6% CPDB-modified SA–gelatine hydrogel achieved the best rheological properties in terms of elasticity and hardness. Different concentrations of epigallocatechin gallate were tested as well as a rheological enhancer to optimize the hydrogel and to boost its anti-microbial properties. However, the results from the addition of EPGCG were not considered significant; thus, the 6% CPDB-modified SA–gelatine hydrogel was further tested for mineralization by incubation in various media, without and with cells, for 7 and 14 days, respectively, using scanning electron microscopy. The results revealed significantly enhanced mineralization of the hydrogel by forming hydroxyapatite platelets of the air-incubated hydrogel (without cells) in non-sterile conditions, exhibiting antimicrobial properties as well. Similarly, the air-incubated bioink with osteosarcoma SaOs-2 cells exhibited dense mineralized topology with hydroxyapatite crystals in the form of faceted spheres. Finally, the FBS-incubated hydrogel and FBS-incubated bioink, incubated for 7 and 14 days, respectively, exhibited less densely mineralized topology and less distribution of the hydroxyapatite crystals. The degradation rate of the hydrogel and bioink incubated in FBS after 14 days was determined by the increase in dimensions of the 3D-printed samples, which was between 5 to 20%, with increase in the bioink samples dimensions in comparison to their dimensions post cross-linking. Meanwhile, after 14 days, the hydrogel and bioink samples incubated in air exhibited shrinkage: a 2% decrease in the dimensions of the 3D-printed samples in comparison to their dimensions post cross-linking. The results prove the capacity of the developed hydrogel in achieving mineralized material with anti-microbial properties and a slow-to-moderate degradation rate for application in bone tissue engineering as well as in the built environment as a structural material using a sustainable approach.

Utilization of polypropylene waste and zeolitic by-product in composite materials

Polypropylene is a widely used polymer that generates a lot of polypropylene waste. This study presents composite materials with matrix made from polypropylene waste reinforced with zeolitic powder (ZP). This zeolite is a waste from the oil industry. The relationships between the density, compressive strength, microstructure, durability for UV radiation and incorporation of ZP in the polypropylene waste matrix were observed. The durability in UV environmental increased due to powder acting as screen of UV radiation in polypropylene composites. This composite could be used as a civil engineering building material for light structures.

Thermal Comfort Comparison and Cause Analysis of Low-Temperature High-Humidity Indoor Environments of Rural Houses in Gansu Province, China

Low temperatures and high humidity often occur in the northern basins and mountainous regions of China. This research reveals a common winter indoor environment in this rural areas characterized by low-temperature and high-humidity indoor thermal conditions. Improving this environment directly with equipment would inevitably result in significant energy consumption. Therefore, comprehending the thermal performance mechanisms of different structural building materials is of vital importance as it provides crucial baseline values for environmental improvement. This study conducted a survey utilizing user questionnaires, resulting in the collection of 214 valid responses. Additionally, a local experiment regarding thermal comfort was conducted. Simultaneously, this study monitored the indoor physical environments of these houses (a sample of 10 rooms was taken from earth houses and 12 rooms from brick houses). Parameters measured on site included air temperature, relative humidity, light illumination, and CO2. The results showed that the humidity inside the earth houses is more stable and regression models can be developed between thermal sensations and temperature for long-term residents. The residents of these earth houses are more sensitive to temperature step. In contrast, the residents of brick houses, experiencing greater environmental variability, demonstrated lower sensitivity and greater adaptability to temperature changes. In addition, heating from bottom to top is more comfortable and healthier for the residents of brick houses in Gansu. Moreover, it is more favorable for the inhabitants’ livelihood to regulate the temperature steps to a maximum of 4 °C. This study provides valuable reference information for the future design of houses in low-temperature and high-humidity environments.

Choosing Conventional Concrete, Ultra-High Performance Concrete or Steel as Material of Construction: An Opinion

Ultra-High Performance Concrete (UHPC) is an emerging concrete material that has potential to become a popular choice of material for construction of structures. UHPC is defined as concrete with characteristic compressive strength of anywhere from 120-150 MPa and above combined with superior properties such as high durability, corrosion resistance, low water permeability among many others. However its high tensile strength and cracking behavior is what makes it unique and interesting. UHPC is reported to have 10 to 15 MPa of tensile strength and excellent post-crack behavior as compared to Conventional Concrete (CC). UHPC is reported to indicate strain-hardening behavior when subjected to post-cracking loads. This unique combination of high compressive strength with tensile strength and resilient cracking behavior reminds us of structural steel which is the other major structural building material with similar behavior. In view of these behavioral similarities, an effort has been made in this paper to compare and contrast the properties of UHPC with structural steel. The stress-stain and load-deflection behaviors of both materials are compared. Also a comparison is made between the two materials when subjected to loading beyond post-crack or post-yield regions. To make this study complete, a comparison of material behavior of UHPC, CC and structural steel with regards to their engineering properties, cost, environmental footprint, construction ease and design life is made. All these three materials are rated based on several parameters such as performance, economy, reusability, sustainability, among others. Finally, the order of choice of these three construction materials for various types of structures for typical scenarios is recommended.

Detection of Fatigue Cracks for Concrete Structures by Using Carbon Ink-Based Conductive Skin and Electrical Resistance Tomography.

Concrete is among the most widely used structural materials in buildings and bridges all over the world. During their service life, concrete structures may inevitably display cracks due to long-term fatigue loads, leading to the degradation of structural integrity. Thus, it is very important to detect cracks and their growth in concrete structures using an automated structural health monitoring system. In this paper, experimental research on crack detection and imaging of concrete structures by using sensing skin and electrical resistance tomography (ERT) is presented. Carbon ink is screen-printed on the surface of concrete as a conductive material to form sensing skins. With these sensing skins, when cracks occur on or near the surface, it breaks the continuity of the sensing skins and significantly reduces conductivity in cracking areas. Then, after exciting small currents in sensing skins and measuring related voltage data, an inverse analysis based on total variation (TV) regularization is adopted to reconstruct tomographic images showing conductivity changes in sensing skins, to detect the occurrence and growth of cracks. The effectiveness of conductive sensing skins and our related crack detection method is validated in experimental studies on a concrete beam subjected to fatigue tests.

Thermal characteristics analyses of clay bricks with wheat straw additives

The production technology of the environmentally polluting baked bricks suggests that they can be replaced by bricks that are produced in an ecologically clean environment, such as the unbaked ones. In the present research work, different brick samples were made and studied, built with clay, sand and agricultural waste raw materials. With the development of the construction industry and increasing environmental requirements, research studies in the field continue to improve the thermal characteristics of the new construction materials. Thus, in the presented work bricks were made, which are a mixture of yellow clay and sand with added 5, 10, 15 and 20% wheat straw. The finished bricks are 0.35/0.08/0.17 m in size. Then, non-destructive measurements were carried out and thermal conductivity coefficient (k), specific heat capacity (Cp), thermal diffusivity (a) and density (ρ) were determined. The results of the measurements show that as the amount of wheat straw increases, the thermal characteristics of the samples improve. Finally, it is proved that the use of unbacked bricks from local clays and the utilization of binders from agricultural waste raw materials, will help to improve the energy performance of the produced environmentally friendly and economically beneficial structural building materials.

Thermal Performance, Microstructure Analysis and Strength Characterisation of Agro-Waste Reinforced Soil Materials

The use of raw-earth materials reinforced by natural fibres, i.e., livestock waste in the form of greasy wool, represents an eco-friendly alternative for a variety of construction applications. This proposal is based on the analysis of unfired adobe blocks stabilised with wool fibres for use as both structural and non-structural building materials. The influence of fibre length on the thermophysical and mechanical properties of the tested material was investigated. The thermal conductivity coefficient (λ) of raw-earth samples was assessed by following three different test setting procedures (T = 20 °C, and HR at 30%, 50%, and 70%), with the aim to evaluate the effects of different fibre lengths in the raw-earth mix. Samples reinforced by fibres 20 mm in length exhibited the lowest thermal conductivity coefficient (λ = 0.719 W/mK) obtained by a test reproducing typical indoor conditions within the Mediterranean area, i.e., T = 20 °C, and HR 50%. The best mechanical performance was exhibited by samples reinforced by fibres 40 mm in length, with a flexural and compression strength of 0.88 MPa and 2.97 MPa, respectively. The microstructure of these biocomposites was also examined with a scanning electron microscope (SEM) and an energy dispersive X-ray (EDX) to qualitatively evaluate the variation of thermal and mechanical properties due to the different adhesion among the fibres and the soil. The experimental data show good efficiency and a significant improvement in the behaviour of these materials compared to the control samples. The evaluation of the results, with the length of the fibres being the only variable of the analysed samples, allowed for the identification of the mix suitable for the best mechanical and thermal performances, depending on the final use of the material.

Effect of Temperature on Moisture Migration in Earth and Fiber Mixtures for Cob Materials

This paper highlights the impact of environmental conditions on cob buildings. Different factors such as wall thickness, material permeability and interactions between moisture and heat fluxes can all have significant effects on the performance and durability of cob buildings. An experimental and modeling-based study was conducted on the hygrothermal characterization of cob building materials, which were obtained by mixing earth and fibers. Two types of cob materials that can be used as insulation and to form structural materials in buildings were tested. The effect of outside temperature on adsorption isotherms was investigated for both materials. The experimental data were fitted using the GAB model, after which a new correlation of water content correlation was proposed. Three specific configurations were investigated in which cob material was subjected to moisture transfer and a zero, positive or negative temperature gradient. Based on the resulting measurements, a high coupling effect between heat and moisture transfer inside the structural material was analyzed. A comparison of the experimental and modeling results demonstrated the satisfactory correlation and reliability of the developed model. Simulations were carried out for various wall thicknesses, in order to assess the effect of heat and moisture transfer on water content. The three scenarios were simulated and distributions of water content inside the walls were determined. The results show that the wall thickness of cob buildings and the direction of heat and moisture fluxes affect water content distribution in the structure. A greater thickness of the cob wall leads to higher water content, but this relationship reverses when the heat and moisture fluxes move in the same direction.

Matrix design and performance development of eco-friendly high-strength, lightweight engineered cementitious composites

This study develops a novel eco-friendly high-strength, lightweight engineered cementitious composite (EHLECC) using lightweight sand fines (LSF) and fly ash cenospheres (FAC) based on the theory of micromechanics, dense packing theory and method of performance driven design. The mechanical properties, microstructures, and micromechanism of EHLECC are examined. The results indicate that the accumulation compactness between different particles in EHLECCs is optimized due to the appropriate particle size range brought by LSF and FAC. LSF and FAC slightly reduced the mechanical strength of EHLECC matrix but had a significant weight reduction effect for EHLECC. All EHLECCs exhibited remarkable mechanical properties with the tensile strain exceeding 6%, tensile stress more than 10 MPa, and compressive strength surpassing 80 MPa. Moreover, the incorporation of LSF enhanced the degree of saturated cracking behavior in EHLECC, resulting in better ductility. Furthermore, LSF substitution rate of 75% led to the optimum matrix design. This study provides a new approach for designing and producing an EHLECC, which would be a promising building material for load-bearing structures and construction reinforcement.

Enhanced mechanical performance and fire resistance of poplar wood: Unilateral surface densification assisted with N/P doped acrylic resin impregnation

It is difficult to significantly improve the mechanical performance and fire-resistance of fast-growing wood without increasing its density. In this study, a modified poplar wood (USD-RA-W) with low-density, high dimensional stability, high mechanical strength, and fire resistance was successfully prepared by unilateral surface densification assisted with the impregnation of waterborne acrylic resin (WAR)/ammonium phytate (APA). The flexural and impact strength values of USD-RA-W increased by 52% and 48%, respectively, compared to the control samples (C-W). The surface hardness and wear resistance of USD-RA-W were also significantly improved, with a 132% increase in hardness and a 22% reduction in weight loss relative to C-W. The improvement in mechanical properties is attributed to the synergistic effects of surface densification and impregnation modification of APA-doped acrylic resin. The in-situ-cured resin network provides excellent dimensional stability by fixing the spring-back of the densified surface of the material. USD-RA-W shows significantly improved fire retardancy due to the introduction of bio-based APA. UL-94 analysis results show that the fire-retardant grade of the USD-RA-W passed V-0 and the limited oxygen index reached 50%. Cone calorimeter test results indicate that the total heat release rate and smoke release rate of the experimental group decreased by 32% and 77%, respectively, while the char residue reached 41%. A simple and green physic-chemical method for the preparation of high-performance USD-RA-W was established in this study. The proposed treated wood may be applicable in structural building materials and interior decoration fields.

DENSITY, COMPRESSIVE STRENGTH, AND IMPACT OF SEAWATER ON UNTREATED TIMBER-FOAMED CONCRETE AS A FLOATING MECHANISM

Land shortages and rising sea levels are now being addressed by floating architecture. Studies on lightweight concrete as a suitable building material for structures on the water have been conducted. Therefore, this article focuses on the addition of untreated timber husk to lightweight concrete (foamed concrete) to diversify and sustainably produce construction materials. This study was designed to examine the durability and buoyancy of untreated timber husk as an addition to foamed concrete as a building material for floating architecture through an experimental approach fixed with numerical analyses on the specification and qualities of lightweight. The results of the quantitative method demonstrated that it was possible to build floating timber-foamed concrete using samples that range in density from 437.5 to 993.3 kg/m³. Each model's compressive strength was measured over a range of curing times, with TH05 producing the highest readings of 2.27 MPa and 0.89 MPa after submerging in seawater. The impact rate from saltwater towards the strength was highest at TH10 with only a 0.25 MPa difference, and the surface of each concrete showed the most reaction on TH15, which was also used to analyse the buoyancy of samples over time. To determine the effects of seawater overtime on the density and strength of timber-foamed concrete, further analysis of seawater’s influence shall be conducted to enhance the materiality of floating architecture.

A multistory, ultra-strong lignocellulose-based structural material for passive solar heating

Currently, most people spend 90% of their daily time inside, relying on mechanical heating and air conditioning. Space heating is the largest source of final energy demand, making up about 50% of the total each year. Existing buildings often have insulation and central heating added to reduce energy consumption for heating, which increases construction costs and carbon emissions. Here, a potent and attainable strategy was demonstrated to process lignocellulose into a high-performance passive solar heating wood with satisfactory passive solar heating and mechanical properties. The passive solar heating wood could absorb ultraviolet light and convert it into thermal energy, resulting in continuous above-ambient heating during the cold day. Compared to traditional building materials, passive solar heating wood exhibits superior heating performance (average daytime heating of ∼25.6 °C) and thermal insulation performance (mid-IR emissivity of 0.51). In addition, the passive solar heating wood exhibits ultra-strong specific strength (80.1 MPa g−1 cm3) and specific impact toughness (56.33 kJ m−2 g−1 cm3) than the most of common polymers, ceramics, and concrete, which opens the way for practical application of lignocellulose based structural materials in advanced thermal management buildings.

Greener homes: Factors underpinning Europeans' intention to live in multi-storey wooden buildings

Climate policies aimed at curbing greenhouse gas emissions embodied in the built environment support the wider implementation of multi-storey wooden buildings. A body of research on public perceptions toward wood as a structural building material is emerging, but close examination of behavioral factors underpinning prospective dwelling is scarce. We used contextualized constructs from the theory of planned behavior to quantify and compare the roles of attitudes, subjective norms, and perceived behavioral control on intentions to dwell in multi-storey wooden buildings. Structural equation models were fitted to survey data from seven European countries (Austria, Denmark, Germany, Finland, Norway, Sweden, United Kingdom; n = 7056). We found that attitudes consistently explain intention to dwell in multi-storey wooden buildings. We also found a varied pattern of relationships between factors underpinning intention across countries. An implication of our results is that national-level policies aimed at promoting social acceptability of dwelling in multi-storey wooden buildings should universally address attitudes toward such novel buildings. But in some countries policies might in addition be tailored to emphasize citizens' subjective norms or perceived behavioral controls.

On the Problems and Prospects of Construction and Reconstruction of Storages for Hay, Haylage, Briquettes and Granules

The problems of construction and reconstruction of storages for hay, haylage, briquettes and granules, the prospects for increasing the scale of construction and reconstruction using new structural models and composite building materials are considered. It reflects the need to update the regulatory and methodological documentation for technological design, construction and reconstruction of storage facilities for hay, haylage, briquettes and granules.

STUDY OF ALTERNATIVE METHODS FOR CARBON DIOXIDE APPLICATION IN CONCRETE PRODUCTION

It is known, concrete ranks second after water in the total annual volume of consumption. Currently, there is no construction material that could replace concrete. It is the main structural building material. The required raw material for concrete production is Portland cement. Unfortunately, the Portland cement production emits carbon dioxide, which accounts for up to 8 % of global emissions of this gas, and is a real threat to the environment.
 The World Business Development Council predicts an increase in cement production by 12–23 % by 2050. This suggests that it is necessary
 to look for methods for Portland cement production with the lowest carbon dioxide emission and methods for its recovery and use.
 The purposes of the research are to study the factors contributing to CO2 emission in Portland cement production; analysis of the main ways of carbon dioxide recovery.
 To solve the problem, popular methods and equipment for concrete production of using dioxide, as well as devices for determining the compressive and tensile strength of concrete, have been investigated.

Detection of hidden defects of thermal protection of buildings and determination of some thermal properties of structural building materials by Non-destructive Thermal Imaging method

Objective. The purpose of the work is the practical approbation of a nondestructive thermal imaging method to identify hidden (invisible) defects and qualitative analysis of the thermal protection of a complex of construction objects in the city of Vologda, as well as the study of some physical (thermophysical) indicators (coefficients of thermal conductivity, thermal resistance (thermal insulation) and heat transfer) of structural building material in the form of silicate brick.Method. The fundamental laws of the theory of heat transfer, thermal nondestructive testing, infrared and technical diagnostics, the current domestic regulatory and technical and regulatory documentation, field experiments on real objects and laboratory samples.Result. The results of the practical determination of hidden defects in the thermal shells of the complex of civil and industrial buildings functioning in the urban environment, thermophysical properties (coefficients of thermal conductivity, thermal resistance (thermal insulation), heat transfer) of modern building materials by methods of thermal non-destructive testing are presented. The locations of identified invisible defects of thermal protection of the surveyed construction objects are determined and recommendations for their elimination are proposed. The obtained values of thermophysical characteristics for the studied structural building material are consistent with the data of current regulatory documents.Conclusion. The features of the nondestructive method of infrared thermography in determining the hidden defects of the heatshielding shells of operated buildings of various functional purposes and the complex of thermophysical parameters of modern structural building materials are shown. The demand for thermal imaging during energy and technical surveys of construction objects, their individual structural elements, life support engineering systems, as well as studies on the refinement, quantification and prediction of various thermal properties of building materials and products has been experimentally confirmed.

An all-natural fire-resistant bioinspired cellulose-based structural material by external force-induced assembly

Natural wood is a widely used structural building material because of its light weight and high strength, yet it is limited by the ignitability. Traditional top-down strategies can delay the burning time of wood-derived materials but hardly reach incombustible performance. Here, we develop a bottom-up external force-induced assembly strategy to fabricate nonburning nacre-mimetic structural materials based on the shear-thinning behavior of cellulose nanofibers, the main component of wood. The highly ordered brick-and-mortar structure endows the structural material with excellent comprehensive mechanical properties and oxygen insulation, giving it better specific flexural strength [143 MPa/(Mg m−3)] and limit oxygen index (100%) than various natural woods. Furthermore, the house model, made of bioinspired structural materials, does not burn or collapse even in a butane blowtorch flame (more than 1100 °C), demonstrating its great potential as a sustainable, lightweight, strong, and safe structural building material.

Sustainable Lifecycle of Perforated Metal Materials.

In an era of rapidly growing consumer demand and the subsequent development of production, light materials and structures with a wide range of applications are becoming increasingly important in the field of construction and mechanical engineering, including aerospace engineering. At the same time, one of the trends is the use of perforated metal materials (PMMs). They are used as finishing, decorative and structural building materials. The main feature of PMMs is the presence of through holes of a given shape and size, which makes it possible to have low specific gravity; however, their tensile strength and rigidity can vary widely depending on the source material. In addition, PMMs have several properties that cannot be achieved with solid materials; for example, they can provide considerable noise reduction and partial light absorption, significantly reducing the weight of structures. They are also used for damping dynamic forces, filtering liquids and gases and shielding electromagnetic fields. For the perforation of strips and sheets, cold stamping methods are usually used, carried out on stamping presses, particularly using wide-tape production lines. Other methods of manufacturing PMMs are rapidly developing, for example, using liquid and laser cutting. An urgent but relatively new and little-studied problem is the recycling and further efficient use of PMMs, primarily such materials as stainless and high-strength steels, titanium, and aluminum alloys. The life cycle of PMMs can be prolonged because they can be repurposed for various applications such as constructing new buildings, designing elements, and producing additional products, making them more environmentally friendly. This work aimed to overview sustainable ways of PMM recycling, use or reuse, proposing different ecological methods and applications considering the types and properties of PMM technological waste. Moreover, the review is accompanied by graphical illustrations of real examples. PMM waste recycling methods that can prolong their lifecycle include construction technologies, powder metallurgy, permeable structures, etc. Several new technologies have been proposed and described for the sustainable application of products and structures based on perforated steel strips and profiles obtained from waste products during stamping. With more developers aiming for sustainability and buildings achieving higher levels of environmental performance, PMM provides significant environmental and aesthetic advantages.