Overview on bio-based building material made with plant aggregate

Global warming, energy savings, and life cycle analysis issues are factors that have contributed to the rapid expansion of plant-based materials for buildings, which can be qualified as environmental-friendly, sustainable and efficient multifunctional materials. This review presents an overview on the several possibilities developed worldwide about the use of plant aggregate to design bio-based building materials.  The use of crushed vegetal aggregates such as hemp (shiv), flax, coconut shells and other plants associated to mineral binder represents the most popular solution adopted in the beginning of this revolution in building materials.  Vegetal aggregates are generally highly porous with a low apparent density and a complex architecture marked by a multi-scale porosity.  These geometrical characteristics result in a high capacity to absorb sounds and have hygro-thermal transfer ability.  This is one of the essential characteristics which differ of vegetal concrete compared to the tradition mineral-based concretes.  In addition, the high flexibility of the aggregates leads to a non-fragile elasto-plastic behavior and a high deformability under stress, lack of fracturing and marked ductility with absorbance of the strains ever after having reached the maximum mechanical strength.  Due to the sensitivity to moisture, the assessment of the durability of vegetal concrete constitutes one of the next scientific challenging of bio-based building materials

Design and multi-physical properties of a new hybrid hemp-flax composite material

International audienc

Influence of the type of viscosity-modifying admixtures and metakaolin on the rheology of grouts

The Viscosity-modifying admixtures (VMAs) contribute to the control of the rheology of grouts and are used to enhance plastic viscosity, cohesion, stability, and resistance to bleeding of cement-based systems.  This paper reports the results of an investigation on the effect of type of VMAs, namely two types of diutan gums and a welan gum and metakaolin (MTK), plus a superplasticiser, on the rheology behaviour of cement grouts.  All mixes were made with polycarboxylic superplasticiser at 0.6% and 0.9%.  The dosages of VMAs were 0.05%, and 0.10%, with a fixed water-to-binder ratio of 0.40.  The investigated fresh properties of the grouts included the mini-slump flow, plate cohesion, and rheology parameters: namely yield value and plastic viscosity.  The rheological parameters were obtained using a vane viscometer.  Control grouts (with and without superplasticiser and VMA) were also tested and compared to mixes containing VMAs.  The results indicated that the incorporation of MTK reduced the fluidity and increased the plate cohesion and yield stress, and plastic viscosity due to the higher surface area of MTK.  The diutan gum grouts improved the grout fresh properties and rheology compared to the welan gum grouts

Application areas of phosphogypsum in production of mineral binders and composites based on them: a review of research results

The increase of the consumption of gypsum products in construction industry with a limited amount of natural gypsum deposits requires alternative sources of gypsum-containing raw materials. In some countries which have fertilizers industry plants, the problem can be solved using industrial wastes, e.g. phosphorgypsum – a byproduct of fertilizers’ production. Kept in dumps over decades, phosphorgypsum is subjected to the chemical changes due to washing out impurities with rain and other natural factors. However, there are observed deviations of harmful impurities in dumped PG depending on its age., Phosphorgypsum of any age requires chemical treatment to neutralize remains of phosphorus and sulfuric acids, fluorine compounds. According to our researches one of the most simple and effective method of neutralization the impurities is using lime-containing admixtures. The paper presents results of laboratory tests of phosphorgypsum as a component of clinker and non-clinker binders. There were investigated the impact of phosphorgypsum as admixture for clinker binders to substitute natural gypsum. Neutralized phosphorgypsum can be applied as mineralizing admixture in calcination of Portland cement clinker. Adding 2 to 2.5% of phosphorgypsum as setting time regulator resulted in a similar physical and mechanical properties compared to mix made with natural gypsum. Another important area of phosphorgypsum application is sulphate activatoion of low-clinker blast-furnace slag cement (clinker content is less than 19%). According to results, the incorporation of phosphorgypsum as sulphate activator in cement has the better effect as natural gypsum. Other development has been carried out to modify the phosphorgypsum binder properties. Complex additive consisted of polycarboxylate-based superplasticizer and slaked lime permitted an increase mechanical properties of hardened phosphorgypsum binder due to significant a reduction of water consumption. Such modified binder can be used as partial or complete replacement of gypsum binder for filling cements and finishing plasters. It can substitute gypsum in non-clinker binders like supersulphated cements. There were also developed compositions of supersulphated cements based on low-alumina blast furnace slag and phosphorgypsum. Supersulphated cements were tested in normal-weight and light-weight concrete

Numerical analysis of a reinforced concrete beam under blast loading

The types of Dynamic loads that might face an engineer during any design procedure vary. One of these loads is the explosion's pressure on buildings which is in other words the blast load. This research has examined the possibility of using a finite element method as a tool for predicting the dynamic response of blast loaded reinforced concrete beams. In this study, the advanced software, ABAQUS is used in order to model materials and consider the material nonlinearity, stiffness degradation and strain rate effects. Experimental results for several beams under explosion are chosen to be modeled and verified using ABAQUS. These experiments were carried out at the National University of Defense Technology in China. The results show that the material properties of concrete under impact loads (high strain rates) can be well defined in ABAQUS. Also the built in model CONWEP for blast load in ABAQUS can be used in the simulation process with an acceptable error

Rheology characterization of 3D printing mortars with nanoclays and basalt fibers

3D printing has become one of the most innovative technologies for cement-based systems (CBS). However, recent studies have shown some issues related to printability and buildability (water drainage, plugs on extruder die, spreading of first layer, etc). To achieve a proper rheology control of CBS, it is essential to adapt the material fresh state properties (initial shear yield stress and structural build-up). In this study, a reference cement-based mortar with fly ash (25%), a 1:1.5 binder to sand ratio and a 0.38 water to binder ratio was used. A polycarboxilate ether-based superplasticizer was added until a consistency of around 1 kPa, measured with the cone-penetration test, was reached. Then, small amounts of several types of nanoclays (NC) in powder and slurry form (sepiolite, attapulgite and bentonite) and natural fibers were added to modify mortar rheological properties. The aim of the study was to characterize the rheological properties of 3D printing mortar samples with NC and basalt fibers (BF) to understand printability and buildability of this material. Cone-penetration test, flow table test and slump test were used to characterize 3D printing capacities. The cone-penetration test was performed in stirred and left at rest samples to assess shear yield stress before and after material deposition. Nanoclays showed a remarkable capacity to retain water and avoid drainage during extrusion but also to increase fresh state strength of material over time. Besides, they increased shear yield stress over time when left at rest. On the contrary, samples stirred over time did not show any increase of shear yield stress, especially samples with slurry nanoclays. Natural fibers also reduced drainage and enhance printability control regarding to reference mortar. BF also enhanced a performance on stirred sample but showed slightly changes on structural build-up at rest, mainly governed by NC effect.This study was partially funded by the Spanish Ministry of Science and Innovation, project Print3Dcement (grant number PID2019-106525RB-I00); by MCIN/AEI/10.13039/501100011033 and the European Union ‘‘NextGenerationEU”/PRTR, project CALTHED (grant number TED2021-132585B-100), and by the University of Alcalá, Grant for training of Lecturers (FPU-UAH 2019) and the trainee Research Personnel Mobility Grant (Movilidad PIF-UAH 2021). The authors acknowledge the experimental help of Sandipan Kaushik of Queen´s University Belfast (QUb). The authors also thank the materials’ supply of the company TOLSA GROUP S.A

Développement des bétons autonivellants à haute performance pour des travaux de réparation sous l'eau

La réparation des ouvrages sous l'eau occupe aujourd'hui une place de choix parmi les différentes techniques de réparation. Il reste que le problème de la qualité de béton doit être assurée afin de minimiser le risque de lessivage dû au contact de béton frais avec de l'eau et de ségrégation du béton ainsi que la durabilité de la réparation. À cet effet, un béton autonivelant peut être utilisé afin d'assurer une meilleure résistance au lessivage et une bonne capacité de remplissage. C'est pourquoi l'utilisation d'un agent colloïdal (AC) dans ce type de béton améliore à la fois la stabilité, la déformabilité et les propriétés mécaniques in-situ. Les bétons autonivelants coulés sous l'eau sont optimisés en tenant compte de la fluidité (étalement), de la déformabilité et de la stabilité. Cette optimisation fait elle-même l'objet d'une autre optimisation qui porte sur l'augmentation de la viscosité, du volume de la pâte ainsi que la réduction de la teneur en gros granulats. Pour améliorer davantage la stabilité, la fluidité, la déformabilité et les performances mécaniques in-situ, on devra forcément utiliser des constituants autres que le ciment, comme la fumée de silice, une cendre volante et un laitier. L'utilisation de ces ajouts minéraux permet aussi de réduire la chaleur d'hydratation. Les bétons autonivelants nécessitent plus de particules fines afin d'assurer une meilleure déformabilité et fluidité. Dans cette thèse, on a montré que les bétons autonivelants, ayant un rapport de volume de gros granulats de 0,30 (par rapport un mètre cube de béton) et un rapport de volume de sable sur pâte (S/P[indice inférieur t]) de 0,60, ont une meilleure fluidité et une bonne déformabilité ainsi qu'une très bonne capacité de remplissage. L'utilisation d'agent colloïdal tel que la gomme welan ou le Rheomac 450 augmente la résistance au lessivage et à la ségrégation du béton. Le lessivage et l'étalement dépendent principalement de la nature et du dosage d'AC et du liant, du rapport E/L (eau/liant) ainsi que du dosage de superplastifiant (SP) et de la vitesse d'écoulement de l'eau. Les rapports de résistance résiduelle à la compression f'[indice inférieur c eau]/f'[indice inférieur c air] et à la traction f'[indice inférieur t eau]/f'[indice inférieur t air], obtenus sur béton coulé dans l'eau par rapport à celui coulé dans l'air, s'améliorent en augmentant le dosage d'AC et de liant et en réduisant le rapport E/L. L'utilisation de 10% de fumée de silice (FS) ou 6% de fumée de silice combiné à 20% de cendre volante (CV) améliore beaucoup la stabilité, la fluidité, les rapports f'[indice inférieur c eau]/f'[indice inférieur c air] et f'[indice inférieur t eau]/f'[indice inférieur t air] et l'adhérence entre un ancien béton et nouveau béton coulé sous l'eau. Les rapports f'[indice inférieur c eau]/f'[indice inférieur c air] et f'[indice inférieur t eau]/f'[indice inférieur t air] sont plus élevés si on réduit le rapport E/L, le lessivage et la hauteur de chute libre du béton dans l'eau (HC). Avec une hauteur de chute libre du béton dans l'eau inférieure ou égale à 450 mm, un mélange contenant 10% FS ou 20% CV + 6% FS, a montré que les rapports f'[indice inférieur c eau]/f'[indice inférieur c air] et f'[indice inférieur t eau]/f'[indice inférieur t air] à 28 d sont tous supérieurs à 84 et 88% pour un rapport E/L = 0,41 (f'[indice inférieur c eau] de 43 MPa et f'[indice inférieur t eau] de 3,5 à 4,6 MPa in-situ) et à 82% pour un rapport E/L = 0,47 (f'[indice inférieur c eau] et f'[indice inférieur t eau] de 38 et 3,4 MPa in-situ). Des bétons autonivelants de haute performance fabriqués avec un rapport E/L = 0,41 et 8% FS ayant un lessivage inférieur à 5% et un étalement de 500 mm peuvent être coulés dans de l'eau, qui circule à une vitesse inférieures [i.e. inférieure] 0,65 m/s, à l'aide d'une trémie conventionnelle. À une vitesse de l'eau, de 0,40 m/s, les rapports f'[indice inférieur c eau]/f'[indice inférieur c air] et f'[indice inférieur t eau]/f'[indice inférieur t air] à 28 d sont supérieurs à 71 et 82% (f'[indice inférieur c eau] et f'[indice inférieur t eau] in-situ sont de 41 et 3,5 MPa). Mais, à une vitesse de 0,65 m/s, ils sont de l'ordre de 60 et 77% (f'[indice inférieur c eau] et f'[indice inférieur t eau] in-situ sont de 36 et 3,3 MPa). Il est donc possible de produire un béton autonivelant à haute performance coulé sous l'eau qui est très fluide, qui a un bon étalement et une bonne capacité de remplissage, ainsi qu'une meilleure résistance au lessivage et à la ségrégation afin d'améliorer les performances mécaniques in-situ et la durabilité

Verso elementi in calcestruzzo armato precompresso senza acciaio: uno studio sperimentale

I materiali compositi sono i principali attori nella sfida verso la ricerca di alternative sostenibili e durevoli all’acciaio per il rinforzo di elementi strutturali in calcestruzzo armato. Tra di essi, le barre costituite da fibre di basalto annegate in matrice polimerica rappresentano un’interessante novità, visto il loro basso costo di produzione, sia ambientale sia economico, e le loro proprietà meccaniche e di resistenza alla corrosione. In questo lavoro vengono presentati i risultati di una campagna di studio, svolta nell’ambito di un più ampio progetto di ricerca europeo denominato EiroCrete, che ha visto la collaborazione del Politecnico di Milano e della Queen’s University of Belfast con aziende italiane (Azichem srl) ed irlandesi (Banager Precast ltd.), e finalizzata a verificare la possibilità di utilizzare tali barre per la precompressione di elementi in prefabbricati in calcestruzzo armato precompresso, realizzati in calcestruzzo autocompattante rinforzato con fibre polimeriche