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Individual and hybrid pre-treatments, including hot water, steam and microwave were used on wheat straw to mitigate the surface quality deficiencies for an intimate interfacial bond between substrate and Polylactic Acid matrix. Microstructural analysis showed the expansion of cells due to the pre-treatments which in turn promotes mechanical entanglement between wheat straw and PLA, thus, improving the tensile properties of bio-based composites. The tensile strength, elongation at break, elastic modulus, and toughness increased by 166 %, 18 %, 68 %, and 285 %, respectively, for hot water followed by steam pre-treated wheat straw bio-based composites compared to untreated. Engineering and Physical Sciences Research Council

The research carried out in this study presents the effectiveness of using sodium acetate as a protective material for concrete pavement. A newly developed freeze-thaw method that depends on the alteration of temperature and humidity is introduced in this research to investigate the efficacy of integrating sodium acetate with concrete with different water to cement ratios (w/c). Results from the introduced freeze-thaw method were compared with the outcomes of a standard freeze-thaw testing method. The distressed concrete was tested for water absorption and compressive strength after finishing six months of freeze-thaw testing. Additionally, the morphology of sodium acetate and its interaction with concrete were investigated by using Scanning Electron Microscope (SEM). Results demonstrated the effectiveness of sodium acetate in protecting concrete. Keywords: Fresh concrete, Concrete pavement, Microstructure, Freezing and thawing, Sodium acetate, Concrete protection

Mycobacterium tuberculosis (M.tb) infection results in approximately 1.3 million human deaths each year. M.tb resides primarily inside macrophages, and maintains persistent infection. In response to infection and inflammation, platelet activating factor C-16 (PAF C16), a phospholipid compound, is released by various cells including neutophils and monocytes. We have recently shown that PAF C-16 can directly inhibit the growth of two representative non-pathogenic mycobacteria, Mycobacterium bovis BCG and Mycobacterium smegmatis (M. smegmatis), by damaging the bacterial cell membrane. Here, we have examined the effect of PAF C-16 on M. smegmatis residing within macrophages, and identified mechanisms involved in their growth inhibitory function. Our results demonstrated that exogenous PAF C-16 inhibited the growth of M. smegmatis inside phagocytic cells of monocytic cell line, THP1; this effect was partially blocked by PAF receptor antagonists, suggesting the involvement of PAF receptor-mediated signalling pathways. Arachidonic acid, a downstream metabolite of PAF C-16 signalling pathway, directly inhibited the growth of M. smegmatis in vitro. Moreover, the inhibition of phospholipase C and phospholipase A2 activities, involved in PAF C-16 signalling pathway, increased survival of intracellular M. smegmatis. Interestingly, we also observed that inhibition of inducible nitric oxide synthase (iNOS) enzyme and antibody-mediated neutralization of TNF-α partially mitigated the intracellular growth inhibitory effect of PAF C-16. Use of a number of PAF C-16 structural analogues, including Lyso-PAF, 2-O-methyl PAF, PAF C-18 and Hexanolamino PAF, revealed that the presence of acetyl group (CH3CO) at sn-2 position of the glycerol backbone of PAF is important for the intracellular growth inhibition activity against M. smegmatis. Taken together, these results suggest that exogenous PAF C-16 treatment inhibits intracellular M. smegmatis growth, at least partially, in a nitric oxide and TNF-α dependent manner.

In recent years the application of transformative technologies has, across a number of industries, represented a challenge to current industry paradigms, resulting in significant improvements in both technical capabilities and output efficiency, whilst disrupting established business models. Many industries are facing an uncertain future in which today’s technological limitations cannot be assumed to apply. The construction industry is likely to be significantly affected by potentially transformative technologies such as additive manufacturing (3D printing), artificial intelligence, and virtual/augmented reality. The application of such technologies presents both significant opportunities and challenges. There are a lot of bottlenecks that need to be resolved before we can maximize the positive impacts of transformative technologies on the construction industry. It is often claimed that additive manufacturing (AM) will transform the way we construct structures and buildings. Although, still in its infancy, this technology is likely to become an important part of the construction industry in relatively near future. AM as one of the most highlighted key enabling technologies has the potential to create disruptive solutions along with automation and robotics, that are at the forefront of building innovation. Material formulations and the science behind the interactions of different components undoubtedly counts as a vital workforce that determines the successful implementation of AM technology in the construction industry. There are fundamental interdependencies between the materials, the printing technologies, and both the scale and geometrical complexity of any printed structure. The construction industry can potentially take utmost advantage of the benefits of AM, e.g. improve safety, reduce labor and time, and advance customization. The key for successful development and implementation of AM is industry stakeholder collaboration involving materials science, architecture/design, computation, and robotics. Automation in construction will happen, there is no question about it and AM will have its role to a certain extent, as it cannot be the sole solution to major problems in the sector.

A new line of research is presented in this study where sodium acetate is used as a protective material for concrete. A newly developed freeze-thaw method that depends on the alteration of temperature and humidity is introduced in this research to investigate the efficacy of integrating sodium acetate with concrete with different water to cement ratios (w/c). Results from the introduced freeze-thaw method were compared with the outcomes of a standard freeze-thaw testing method. The distressed concrete was tested for water absorption and compressive strength after finishing six months of freeze-thaw testing. Results demonstrated the effectiveness of sodium acetate in protecting concrete

In this study an extensive experimental campaign has been conducted on mortars modified with nano-Graphite (nG) aimed to assess the properties of the resulting nanocomposites in terms of density, microstructure, flexural and compressive strength, damping ratio, thermal and electrical conductivity. Permeability properties were also investigated in terms of initial surface absorption, water contact angle, volume of permeable voids and chloride ion diffusion. Premixed mortars have been modified with different dosages of commercial nG, i.e. 0.01%, 0.1%, or 0.2% by weight of cement. The rheological behavior of the fresh admixtures has been investigated. Specimens were casted in bars and hardened in water for 7, 14 or 28 days. At 28 days all samples showed enhanced density (i.e. up to 16%) and mechanical properties (i.e. up to 30%) combined to remarkable decreased overall permeability. The lowest dosage of nG (i.e. 0.01% by weight of cement) resulted in cement nanocomposites with the highest increase in damping ratio, electrical and thermal conductivity, 68%, 30% and 55%, respectively.

The variation of physicochemical characteristics across wheat straw node and internode with their surface functionalities was investigated. Node yielded slightly higher klason lignin, extractives and ash content than internode, which could be related to their morphology; specifically the higher ash and extractives content in the node are explained by thicker epidermis tissue. These properties make nodes defects in composite and bio-energy production, while internodes could be more favourable for aerobic digestion for biogas production. Surface chemical distribution examinations revealed, higher intensities of the hydrophobic aliphatic fraction of waxes on the outer surface, whereas the hydrophilic tendency of inner surface was reflected by the broad and more intense band in the 3200–3600 cm−1 region, due to OH stretching vibration of hydroxyl groups. This could translate into better interface when water-based resins are used for wheat straw composites. An environmentally friendly pre-treatment was employed to further investigate the effects on the physicochemical properties. The results showed: i) the reduction of waxes from the outer surface, ii) significantly lower (P

The challenges of sustainable construction, industrial growth and importance of resource efficiency are clearly recognised by the UK government and are now at the forefront of strategy and policy. A critical component of the government’s sustainability strategies concerns way in which construction and demolition waste (C&DW) is managed. In this study a mixed method approach was adopted to investigate current practices of C&DW management and circular construction (re-use, recycle and recovery of materials) concept awareness in the UK. Relevant stakeholders from the construction industry (contracting, demolition and C&DW organisations) were selected and their views solicited on arguments about circular construction to help establish common visions and further encourage sustainable behaviour across the sector. The study revealed that legislation by the government on the re-use and recycling threshold for every new project can substantially improve circularity within the built environment. More specifically, focus should be on smart dismantling of buildings and ways of optimising cost effective processes. This will enable fair competition between stakeholders and eventually lead to investments in innovative approaches for resource recovery from C&DW. Further incentives and appreciations from government should also be given to stakeholders who are innovating and setting benchmarks in circular construction. This can lead to harmonised technological and non-technological solutions, closed-loop material processes and a circular economy.

Additive manufacturing (AM), popularly known as ‘3D printing’, is a manufacturing technique that builds physical 3D objects layer by layer using materials such as polymers, metals, and cementitious composites. The widespread popularity of additive manufacturing in most industries ranging from biomedical to aerospace suggests a revolution in manufacturing which has recently emerged to the construction sector. Considered as the future of construction, AM is used in 3D concrete printing due to its benefits in reducing the waste and contributing towards circular economy goals through the use of recovered waste materials from demolition sites. This paper presents an active extrusion system for the 3D printing of cementitious materials for the construction industry. The system has been designed from first principles and therefore can be extended to other materials and scaled up with slight hardware modifications. A robust design has been realized using an unconventional yet simplistic approach. The extrusion system uses some additions to the design to generate a consistent output of material throughout a print. The effectiveness of the extruder is demonstrated through an extensive printing and testing of various printed objects.

In this study, properties of cement composites and mortars were investigated in presence of Nano-Fe2O3 as their modifier. Cement composites were synthesized using the sol-gel method with tetraethylammonium orthosilicate as the complex legend. Subsequently, Nano-Fe2O3 was added at 2, 4, and 6 wt% dosages to the cement composite, while for mortars 2, 3 and 4 wt% of Nano-Fe2O3 dosages were used. FTIR and XRD tests were conducted to analyze the phase composition, molecular, and microstructure of cement composites, additionally, the effects of adding Nano-Fe2O3 on compressive and flexural strengths of mortars were investigated. The results indicated a change in the phase composition of the molecular-structure of cement composites, leading to stronger bonds in silicate network with more ordered arrangement in the presence of nanoparticles. The formation of three-membered silicate rings was also evident in composite samples containing higher amounts of Nano-Fe2O3 (i.e. 4 and 6 wt%). The microstructure analysis revealed that samples with Nano-Fe2O3 had a denser structure with a smaller pore size in comparison with control samples. The mechanical performance of mortar samples were enhanced with the incorporation of Nano-Fe2O3, where 3 wt% dosage was identified as the optimum.

This paper focuses on straw biomass and its main composition with the emphasis on the concept of bioengineering where agricultural biotechnology is discussed with references to success and limitations for the bioconversion of straw biomass to value added bio-products, mainly bio-energy and bio-composite. Biological pre-treatments on straw biomass have been reviewed where the function of biological enzymes and fungi have been discussed in details. Biological pre-treatments have been linked with fungi capable of generating enzymes that biodegrade lignin, hemicellulose and polyphenols. Lignocellulolytic enzymes are considered as prospective biomass degraders for industrial applications, although lignin which is the most recalcitrant constituent of straw biomass, links to hemicellulos and cellulose, thus turns into a barrier for enzymes and stops the infiltration of enzymes to biomass structure. White-rot fungi are identified to be responsible for effective lignin biodegradation in straw biomass decay procedures. It was found that biological pre-treatment in combination with mild chemical and or physical pre-treatments are the most critical process for the success of bioengineering. Bioconversion of biomass to bio-products e.g. bioethanol, biogas and bio-composites has achieved some success, however, several limitations such as long incubation times remain to be solved. The summarised information presented in this paper shall serve as scientific insights and directive fundamentals for researchers and industries for further developments and investments in biotechnology of straw biomass.

This study is aimed at fully understanding wheat straw by investigating important properties for the processing of wheat straw (node and internode) for further production of bio-composites and bio-fuels as they server as great renewable resource. A combination of mild physical treatments and the synergetic effect of each physical treatment were investigated in terms of chemical, surface and mechanical properties. Functional groups changes were monitored in two anatomical sections of wheat straw stem inner and outer surface and the results showed a reduction in the intensities assigned to aliphatic fractions of waxes and silica after each stage of pre-treatments when compared to the untreated samples. The penetration rate (wettability) and hydrophobicity of wheat straw internode outer surface was analysed through contact angle measurements which indicated 35% decrease in hydrophobicity of straw surface therefore increasing the wettability of surface after the combinational pre-treatment. The relationship of surface characteristics to the mechanical properties of wheat straw was also investigated by testing the single strand tensile strength of nodes and internodes before and after pre-treatments. Mechanical test revealed 35% increase in tensile strength of wheat straw after the pre-treatment in comparison to untreated wheat straw. The thermogravimetric analysis clearly illustrate that the thermal stability of the wheat straw increased after the pre-treatment which is encouraging for the bio-composite application.

The weak mechanical properties the 3D printed parts can limit the competence of this technology when compared to conventionally cast-in-mold cementitious composites structures. However, experimental results in this study showed that the incorporation of nano additives could improve the mechanical property of printed structures. Six geopolymeric mixtures were designed and tested for their flow-ability, shape stability, buildability and mechanical performance. Different dosage of nano graphite platelets (NGPs) ranging from 0.1% to 1%, by the weight of geopolymer, were incorporated to the best performing geopolymer. The 3D printed geopolymer with 1% of NGPs increased the flexural strength by 89% and 46% compared to the same 3D printed and casted geopolymer without any NGPs, respectively. The same increase for compressive strength was 28% and 12%. Moreover, the geopolymer mix containing 1% of NGPs demonstrated the best shape retention and buildability.

This study investigates the interfacial bonding of natural fibre reinforced (NFR) cementitious composites by exploring the incorporation of 20–30 mm strands of uncoated and resin coated flax/wool twine into various cementitious matrices. Cementitious matrices consisting of pulverised fly-ash (FA), ground granulated blast furnace slag (GGBS) and ordinary Portland cement (OPC) in various ratios were tested with the addition of flax/wool twine (1% volume ratio). The mechanical properties of these samples were assessed at 7 and 28 days. The results showed a reduction in the flexural and compressive strength of uncoated NFR samples compared to unreinforced (UNR) counterparts due to weak interfacial bonding between the uncoated fibres and the cementitious paste, therefore, formation of voids. Epoxy (EP) and polyurethane (PU) resin were then used to coat the flax/wool twine prior to their inclusion in various cementitious pastes. The results revealed improvements in both flexural and compressive strengths exhibited at 7 and 28 days compared to UNR and uncoated NFR samples. The greatest improvement of flexural strength, 61% compared to UNR, was achieved by the mix consisting of 50% OPC and 50% FA matrix with EP resin coated flax/wool twine at 28 days. While PU coated samples exhibited an increase of 31% in flexural strength at 28 days for the same cementitious mix ratio. The morphology of the resin coated NFR samples showed an intimate interfacial bond to surrounding cementitious paste, which explains the increased mechanical performance.

To valorize the naturally abundant biomass, bio-composites made of biomass and functional nano-materials have attracted a great deal of attention. By incorporating alginate with TiO2/RGO nanocomposites, TiO2/RGO/Alginate composite (TRGA) aerogels are fabricated via a facile freeze-drying method. TiO2/RGO nanocomposites can effectively improve the surface roughness and mechanical performance of alginate-based matrix, and provide the aerogels with light-driven self-cleaning ability. Without further chemical modification, the as-fabricated TRGA aerogel shows: i) collective underwater superoleophobicity (θoil > 150° for various oils), ii) effective oil/water separation performance (9.76 L·m−2·s−1 water permeate flux and 99.96% separation efficiency) and iii) excellent light-induced recyclability. With light-driven self-cleaning ability, the continuously deteriorated separation performance of aerogel can be easily renewed, and maintain an effective oil/water separation performance even after 120 cycles. Benefiting from its facile fabrication and excellent properties, the developed aerogel can be a promising candidate for practical oil/water separation in marine oil spill clean-up applications.

This research presents new insight on the performance of concrete when integrated with sodium acetate and cured under extremely harsh environmental conditions: freezing temperature of −25 °C and hot temperature of 60 °C. Mechanical properties, water absorption, microstructural analysis and interaction mechanism of concrete and sodium acetate were evaluated by conducting the compressive strength test, Initial Surface Absorption Test (ISAT), Scanning Electron Microscope (SEM) analysis and Fourier-transform Infrared Spectroscopy (FTIR) analysis. Despite the harsh curing conditions, results showed an enhancement of 64% in compressive strength when 4% (based on the weight of cement) sodium acetate is incorporated within concrete with w/c ratio of 0.32 and cured under temperature of 60 °C. Also, water absorption was observed to decrease by more than 79% when 2% sodium acetate is added to concrete with w/c ratio of 0.32. SEM and FTIR analyses revealed the formation, high distribution and strong bonding of sodium acetate crystals within the concrete’s micropores.

A series of uniaxial tensile tests on cylinders made from steel fibre reinforced self-compacting concrete (SFR-SCC) have been carried out to investigate the influence of fibre geometry and the combined effect of fibre content and distribution on the post-cracking behaviour. Three types of commercially available hooked end fibres (3D (single hooked), 4D double (double hooked) and 5D (triple hooked)) have been used in this study, which are added to the concrete mixture at two fibre dosages (0.5 and 1% by volume). The experiments show that the post-cracking strength increases significantly (P

There has not been extensive research into the subjects of the interfacial bonding quality and the interaction mechanisms of biopolymers and natural fibres. Attempts have been made to incorporate natural fibres/fillers (biofibres) into the manufacture of composites in order to increase the functionality and performance of biopolymers synthesised from natural sources/microbial systems. However, the interfacial bonding quality and other substantial technical challenges still need to be addressed if their industrial use is to be realized. The interfacial bonding quality ultimately dictates the mechanical and physical performance of bio-composites. This review paper attempts to collate the state-of-the-art regarding coupling agents/ additives and their roles in interaction mechanisms with biofibres and biopolymers. Two potential pathways for narrowing the performance gap between biopolymer-based bio-composites and their petroleum-based counterparts are: i) improving the interfacial bonding quality by the synthesis of a specific coupling agent, and ii) improving the processability of bio-composites by blending two or more biopolymers.

Morphology and chemical distribution of wheat straw stem, including nodes and internodes, were profiled and thoroughly analysed through a combination of qualitative and quantitative analytical techniques. It was found that the morphology across node area has great variety when the longitudinal profile was investigated in the upwards direction to the grain head; the node core morphology revealed a very dense zone with elliptical shaped rings organised in order to provide the mechanical strength to the overall stem. ATR-FTIR results for the chemical functional groups of outer and inner surfaces of node and internode also showed differences in terms of concentration of functional groups present in each section. It was revealed that the outer surface of wheat straw stem has a higher concentration of aliphatic fraction of waxes compared to the inner surface, with the highest being in the node area. EDX-SEM results were averaged for node and internode and also for inner and outer surfaces for quantitative comparison. It was found that the outer surface of wheat straw had considerable higher Si contents than the inner surface. Also higher content of C in the node outer surface is an indication of high quantity of wax which is in agreement with ATR-FTIR results. The crystallinity of node and internode was investigated using XRD; it was found that node is more amorphous than internode with the crystallinity index of 34.73% compared to 45.00% of internode. The profile of wheat straw morphology in the nodes has never been reported; the results of the quantitative and qualitative structural analysis through in-depth microstructure interpretation, and detailed and accurate chemical composition improved the understanding of straw biomass.

In order to efficiently utilize wheat straw, the systematic examination of their cell wall components, chemical structures, morphology, and relation to the physicochemical and mechanical properties is necessary. Detailing of node and internode signifies their different features and characteristics which can ultimately lead to their separated processing for enhanced efficiency and higher value-added biorefinery. In this study, distinct variations were found among characteristics of node and internode, inner and outer surface. It was revealed that the node has more extractives, Klason lignin, and ash content than the internode; higher contents of extractives and ash in the node are related to the thicker epidermis tissue. Hot water followed by mild steam pretreatment was used to examine the effects on the characteristics of wheat straw. The results showed: (1) reduced level of waxes and Si (weight %) from the outer surface and (2) significantly lower (P < 0.05) extractives content in both internode and node.

Using expanded cork dust as a cheaper substitute of fumed silica, the expanded cork/fumed silica composites with hierarchical porous structure were designed and constructed as an alternative lower cost material for vacuum insulation panel (VIP) core. A novel strategy compromised of microwave pretreatment and vacuum impregnation method is developed for cork restructuring and recombination. The morphology, microstructure and thermo-physical properties of expanded cork/fumed silica composites were thoroughly investigated. It is found that the microwave pretreatment is a rapid and effective method to restructure cork, and then fumed silica can be introduced into the cork pores efficiently by the vacuum impregnation method, resulting in a hierarchical microstructure of cork micro-pores and nano-porous fumed silica micelle. Thanks to this unique hierarchical porous structure, the hybrid expanded cork-fumed silica materials show an excellent thermal insulation property (as low as 6.3 mW/m∙K at pressure < 1 mbar). The results demonstrate that the proposed strategy is an efficient means to construct a hierarchical porous expanded cork/fumed silica hybrid network system, and the as-prepared composites could have a potential application for VIPs core materials due its cost-effective and good thermal insulation performance. The research is supported by the European Union's Seventh Framework Program managed by REA-Research Executive Agency [FP7-SME-2013], under the GA No. 606037.

The relevant information about the lignin in straw and its applications in the industry is scattered and scarce compared to the wood lignin. This review is focused on the chemical structural and composition of lignin in the straw, and its modification and uses as an adhesive. The review has showed that (1) lignin as a by-product in the pulping process and as an abundant natural and renewable product has been used and there is a great potential for many applications across various industrial sectors as a replacement for increasingly scarce and expensive petroleum based materials, including traditional products, e.g. resins, and composites, and emerging materials, e.g. biofuel and commodity chemicals. (2) The type of lignin differs not only from one to another species but also depending on the isolation protocol. However, the lack of optimising or processing technologies is significant when it comes to using technical lignin. The review has also shown a great encouragement in studying the lignin within the straw and other herbaceous crops, and the creation of the functionalities of lignin as it does with cellulose and hemicellulose could lead to radical development of lignin as bio-matrix for green composites and biomass as biofuel or other high value added applications.

Agricultural by-products are the most promising feedstock for the generation of renewable, carbon neutral substitutes for synthetic materials (e.g. biofuel, building materials). The demand for efficient utilisation of lignin biomass has induced detailed analyses of its fundamental chemical structures and development of analysing technologies. This paper reviews the structural analysis techniques for straw lignin together with the morphology of the lignin biomass and the study of the form and structure of organisms and their specific structural features. The review showed that the studies on lignin could be divided into the qualitative and quantitative analyses; different analytical methods could provide significantly different results that are even sometimes not directly comparable. Among many techniques reviewed, the magnetic resonance techniques have proved to be efficient analytical tools for the structural elucidation of these complex biopolymers. Quantitative and qualitative structural analysis of lignin indicated a great potential for industrial crops optimisation due to in-depth microstructure interpretation, and detailed and accurate chemical composition although the composition and structure of straw lignin have been discovered highly complex and varied considerably within and among plants. The structure of lignin has remained one of the most difficult biopolymers to characterise, however recent advances in analytical chemistry and spectroscopy have dramatically improved the understanding of this natural resource, and further value added utilisations are being expected for the lignin and its related biomass.

This article has been made available through the Brunel Open Access Publishing Fund. This paper conducted research on fracture and impact properties of short discrete jute fibre reinforced cementitious composites (JFRCC) with various matrix for developing low-cost natural fibre reinforced concretes and mortars for construction. Fracture properties of JFRCC were tested on notched concrete beams at 7, 14 and 28 days and the results were interpreted by the two-parameter fracture model (TPFM). Impact resistance of JFRCC were examined on mortar panels with the dimensions of 200×200×20 mm3 at 7, 14 and 28 days through repeated dropping weight test. Qualitative and quantitative analyses were conducted for crack pattern, impact resistance and energy absorbed by JFRCC mortar panels based on eye observations and measurement from an oscilloscope. In addition, compressive, flexural and splitting tensile strengths of JFRCCs were tested at 7, 14 and 28 days conforming to relevant EN standards. It was found that, by combining GGBS with PC as matrix, JFRCC achieved higher compressive strength, tensile strength, fracture toughness, critical strain energy release rate, and critical stress intensity factor than those with combination of PFA and PC as matrix. Impact tests, however, indicated that JFRCC mortar panels with PFA/PC matrix possessed higher impact resistance, absorbed more impact energy and survived more impact blows upon failure than those with GGBS/PC matrix at the ages of 14 and 28 days. JFRCC mortar panels did not shatter into pieces and demonstrated a ductile failure while the plain mortar ones behaved very brittle and shattered into pieces. Upon impact failure, fibre pull-out was observed in JFRCC mortar panels with PFA/PC matrix while fibre fracture in those with GGBS/PC matrix. Besides, the impact resistance, in terms of the number of impact blows survived and the total energy absorbed upon failure, of JFRCC mortar panels decreased with age.

The construction industry has seen an incredibly fast increase in utilizing natural fibres for making low-cost building materials to achieve sustainable construction. One of such applications is natural fibre-reinforced cementitious materials for either structural or non-structural purpose. Impact properties are engineering properties received increasing attentions from engineering community for structural materials. This research therefore studies impact resistance of hemp fibre reinforced cementitious composites at early ages. Hemp fibre with various lengths, 10 mm and 20 mm, are utilized to reinforce cementitious materials. Hemp fibre reinforced cementitious composite slabs were tested under repeating dropping mass till failure at the age of 7, 14 and 28 days. Cracking behaviour, impact resistance, absorbed impact energy and survived impact blows upon failure are qualitatively/quantitatively analysed. It has been found that 20 mm-long hemp fibre reinforcement leads to higher impact resistance, more absorbed impact energy and survived more impact blows upon failure. Cementitious composite slabs reinforced by 20 mm-long hemp fibres exhibit higher impact crack resistance ratio than those reinforced by 10 mm-long fibres. Longer fibres are more effective in inhibiting the growth of micro-cracks and blunting the propagation of micro-cracks before they join up to form macro cracks leading to ultimate failure. Partial finance support from the European Commission Horizon 2020 MARIE Skłodowska-CURIE Research and Innovation Staff Exchange Scheme through the grant 645696 (i.e. REMINE project) is greatly acknowledged.

Copyright © 2021 The Author(s). One of the fields in the construction industry where 3D printing of cementitious composites can play a significant role is associated with manufacturing of lightweight structures. Thanks to 3D printing, structural self-weight can be reduced by topology optimization of printed elements. Moreover, further decrements of self-weight and improvement of thermal insulating properties can be achieved by the mixture design and introduction of materials of low thermal conductivity. To date, limited knowledge on lightweight printable mixtures is available. The main objective of this study is to develop 3D printed lightweight concrete (3DPLWC) mixture, with the intention of replacing natural aggregate with waste glass (WG) by 50 vol.-% and 100 vol.-%. Moreover, expanded thermoplastic microspheres (ETM) were incorporated into the mixture. This led to a reduction in density of the mixtures as well as the thermal conductivity by up to 40%. Comprehensive evaluation of material's fresh properties revealed that the addition of ETM results in 3D printable material with lower yield shear stress and higher plastic viscosity by 28% and 66%, respectively, compared to the mixes without ETM. Moreover, improvement of shape retention, flowability, setting times, and early-hardened mixtures' properties was observed. The mechanical properties of 3DPLWC showed that the replacement of natural aggregate by 50 vol.-% WG led to enhanced flexural and compressive strength of the composite, while full replacement resulted in retaining or slight reduction of the mechanical properties. European Union's Horizon 2020 research and innovation program, under the Marie Skłodowska-Curie grant agreement No. 841592.