Mortar Formulation Research Articles

English

This study aims to evaluate the influence of different additives, including natural additives such as olive oil and eggs, on repair and restoration mortars. This work enables us to verify the effects of these natural components and their impact on the physical and mechanical characteristics of various types of repair mortars. Four mortar formulations were developed and analysed: Two jointing mortars, including the control sample MF1, without additives; and two finishing mortars (plaster). The physical and mechanical analysis of these different mortar samples showed that each additive had effects on the durability, percentage of absorption and porosity of the samples, as well as on their water repelling, and waterproofing properties. The control sample MF1 had the highest content of total porosity and water absorption. In the other samples, the water absorption and porosity contents decreased with an increase in the quantity of crushed bricks. In addition, sample MF3, which contained two volumes of crushed bricks per one volume of lime and an addition of 5% olive oil, had the lowest water absorption and porosity content and the highest resistance to compression and bending. The results obtained demonstrate that the mortars with natural additives MF3 and MF4 have reduced rate of water absorption, porosity, and water absorption by capillarity than control mortars (MF1) and samples with only crushed bricks added (MF2). Key words: Repair mortar, natural additives, compatibility, crushed brick, olive oil, eggs, water repellent, durability.  

Compatibility between thermochromic pigments and Portland cement-based materials

Encapsulated reversible thermochromic (ERTC) pigments with optical properties that change reversibly with temperature have been used in building coatings to improve energy efficiency and reduce environmental impact of buildings. This work presents a detailed characterization of commercial ERTC pigments useful for this application and an analysis of their compatibility with the aggressive cementitious matrix. Chemical reactions involving the pigment are identified through the analysis of the solid phase and pore solution of a white Portland cement paste and a mortar with calcareous aggregate during the first 3 h of hydration. The results indicate that a low concentration of potassium ions in the aqueous phase is necessary with respect to the concentration of pigment microcapsules to achieve a proper stability of the thermochromic response. This condition is fulfilled in the case of mortar formulations used for building coatings, thus ensuring the viability of developing a chemically stable thermochromic mortar coating.

Nanomaterials’ Influence on the Performance of Thermal Insulating Mortars—A Statistical Analysis

This research provides a statistical analysis of the mechanical and physical properties of thermal insulating mortars developed in the laboratory and by the industry with and without the incorporation of nanomaterials. This was evaluated by carrying out a uni and bivariate analysis, principal components and factor analysis, cluster analysis, and the application of regression models. The results show that it is possible to find associations between these mortars’ properties, but also how these formulations’ development can be approached in the future to achieve better overall performance. They also show that the use of nanomaterials, namely silica aerogel, significantly improved the mortars’ thermal insulation capabilities, allowing us to obtain mortar formulations with thermal conductivities below the values presented by classic thermal insulating materials. Therefore, with this investigation, other researchers can support their product-development choices when incorporating nanomaterials to reduce mortars’ thermal conductivities, increasing their production efficiency, overall multifunctionality, and sustainability.

Exposure Assessment During the Industrial Formulation and Application of Photocatalytic Mortars Based on Safer n-TiO2 Additives

Titanium dioxide nanoparticles (n-TiO2) are added to photocatalytic mortars to improve urban air quality. Their activity can be increased by dispersing and binding them on natural sepiolite surface. Workers handling photocatalytic additives can be exposed to n-TiO2. However, the release of nanoparticles to the workplace can be different if the material used is raw n-TiO2 powders or if the nanoparticles are supported on sepiolite. In this work, we compare occupational exposure to n-TiO2 for raw n-TiO2 and a hybrid additive n-TiO2/sepiolite obtained by a proprietary process. Measurements were performed in two industrial sites that process 1 ton batches of mortars, formulated with the same quantity of n-TiO2, followed by their application outdoors. Direct reading instruments were used to monitor particle number concentration and size distribution. Simultaneously, filter-based samples were collected for mass concentration and microscopy analysis. Two tasks produced a significant release of particles, the addition of fillers during the mortar formulation, in site 1, and the mixing of mortar with water for its application in the second site. For the first task, particle concentration was significantly lower when the n-TiO2/sepiolite was added compared to the raw n-TiO2. For the second task, once the mortar is fully formulated, this metric does not identify differences among the batches. Titanium mass concentration was 3–10 times lower when handling the mortar formulated with the hybrid additive. These results suggest that supporting the n-TiO2 on the sepiolite network not only increases the photocatalytic activity, but is also a safer design that reduces exposure to nanoparticles.

Compositional and textural characterization of historical bedding mortars from rubble stone masonries: Contribution for the design of compatible repair mortars

The present research addresses the compositional and textural properties of bedding mortars from rubble stone masonries of a historic construction, built between 13th and 17th centuries and during different constructive periods (National Palace of Sintra, Portugal). The characterization of mortars established the basis for the formulation of compatible repair mortars. The mortars revealed similar composition and depended on the raw material locally available (calcitic binder and aggregates of granitic nature), whereas the textural features (b:a and aggregate gradation) varied significantly according to mortar use (interior/exterior walls; interior/exterior leaf of exterior walls). Statistical analysis on textural data allowed to propose different repair mortar formulations according to their use; one for interior walls (b:a ≈ 1:2) and two for exterior walls (b:a ≈ 1:3 and b:a ≈ 1:4).Besides, the research found consistent correlations between mortars’ characteristics and the historical background of the monument although further analyses are required for a definitive link between masonries materials and the constructive periods.

High performance mortar for ductile seismic-resistant unreinforced masonry systems

The paper presents the results of an experimental campaign aimed at assessing the structural performances of unreinforced masonry systems realized with a novel ductile mortar. The experimental campaign described in the paper is part of the research project “Zero Environmental Risks in Our buildings” (ZERO) whose broad objective is to develop a new class of construction materials and decorative products characterized by high environmental compatibility, i.e. Volatile Organic Compounds (VOC)-free, as well as superior performances in terms of both chemical and mechanical properties. Two mortar formulations, one for thin-joints and one for thick-joints, have been tested under flexural and compressive loads, and their performances compared with those of benchmark mortars available in the market. Masonry assemblies have been realized with different types of hollow clay blocks available in the market, including flat structural and non-structural blocks for thin joints and structural clay blocks for ordinary joints. The results of the experimental tests proved the effectiveness of the innovative ductile mortar in improving both shear strength and shear deformation capacities of unreinforced masonry assemblies.

Effect of citric acid on calcium sulfoaluminate cements synthesised from industrial wastes at low temperature

A study of the effects of citric acid on the mechanical properties of calcium sulfoaluminate (C4A3S̄) cements in hydraulic pastes and mortars was performed. Clinker made up of C4A3S̄ was obtained from the calcination of a mixture of fly ash, aluminium dross and fluorogypsum at 1100°C. The C4A3S̄ cement was prepared by mixing the clinker with certain percentages of commercial hemihydrate. Hydraulic pastes and mortars were prepared with 0·05% citric acid relative to the total weight of the cement in order to slow down the reactions and also to act as a structural modifier. The initial and final setting times of the pastes were up to 189 and 336 min, respectively. The compressive strength was evaluated in specimens cured at room temperature, reaching, in some mortar formulations, more than 80 MPa at 360 d with high initial development. Hydration reactions were significantly affected by both the citric acid and the increase in temperature, as confirmed by isothermal conduction calorimetry. The main hydration product was ettringite, which promoted the formation of dense and compact microstructures.

Antimicrobial efficacy of building material based on ZnO/palygorskite against Gram-negative and Gram-positive bacteria

This study investigated ZnO nanoparticles immobilized in palygorskite clay mineral (Pal) that acted as an inorganic antimicrobial agent in a commercial mortar aiming to control microorganisms and improve safety and stability for building applications. ZnO/Pal nanocomposites were obtained by sol-gel methods at pH 7 and 11 and were calcined at 250 °C and 400 °C to evaluate different synthesis parameters. The mortar/ZnO/Pal composite was obtained using 5% (by weight) ZnO/Pal hybrid mixed with a commercial mortar. The results show that pH and calcination temperature influenced the properties of ZnO/Pal. ZnO was observed in the ZnO/Pal samples during the wurtzite phase by analyzing the XRD patterns. FTIR spectra illustrated the interactions between ZnO nanoparticles and the fibrous clay mineral. TG-DTG analysis showed the thermal events of Pal before and after zinc incorporation. Scanning electron microscopy (SEM) evaluated ZnO morphology as spherical in shape and dispersed on the fibers of the clay minerals, which presented needle-like morphology. ZnO/Palygorskite showed a possible antibacterial effect when used in mortar formulation. The mortar/ZnO/Pal composites were effective against Escherichia coli and Staphylococcus aureus bacteria when tested by the direct contact method in darkness and in visible light and could be an alternative antimicrobial material for building surfaces.

Performance of Lightweight Aggregates Comprised of Sediments and Thermoplastic Waste

The management of dredging sediments and plastic waste is of increasing environmental, societal, and economic importance. To address this, we produced lightweight aggregates composed of 70% sediment based mineral filler and 30% thermoplastic waste containing polypropylene, polyethylene, and polystyrene. When tested, the aggregates satisfied the requirements of the European Standard EN 13055-1 for lightweight aggregates and exhibited good mechanical properties and low water absorption compared to natural aggregates. Based on these results, the formulated lightweight aggregates were found to be suitable for use as a partial replacement for up to 30% of the natural sand in mortar formulations.

Biocolonisation of polymer-modified mortars

Polymer-modified mortars are cementitious materials that integrate polymers from 5 to 20 wt.%. Those materials are widely used for protecting and/or repairing concrete surfaces among which building facades, civil engineering structures, or sewage networks. In this context, polymer-modified mortars are applied into thin layers of about 1–3 cm. However, previous studies performed regarding such materials were carried out on massive pieces and did not consider the interactions between polymer-modified mortars and microorganisms. Nevertheless, such interactions can lead to undesired aesthetical or structural modifications of those materials. As a result, the main objective of this paper is to evaluate the resistance to biocolonisation of polymer-modified mortars applied into thin layers in environmental conditions that are representative of the on-site applications. Two formulations of polymer-modified mortars and a polymer-free mortar are characterised in the hardened state. Then, the resistance of those mortars to biocolonisation is tested by means of two laboratory accelerated tests. The first experiment is performed in order to recreate biofouling at the surface of the specimens, while the second one exposes the materials to biodeterioration. The results and analyses show that in the presence of polymer, both porosity and capillary absorption of mortars are reduced, but this does not allow preventing or slowing down biocolonisation. In addition, this study suggests that the nature of the polymer has an influence on bioreceptivity of polymer-modified mortars. Finally, our results suggest that in the presence of polymer, the global material may have an improved inner cohesion.

The effect of fly ash and granulated blast furnace slag on slip and tensile adhesion strength of tile adhesives mortars

In the formulations of adhesive mortars for tiles almost exclusively CEM I Portland cements are used. Practically no CEM II - CEM V cements with additives are used, although they are often produced with strength classes 32.5 R and some even 42.5R. Relationship between strengths of tile adhesives in which cement was partially replaced with fly ash and granulated blast furnace slag was studied. A fly ash was used in three different replacement levels from 5% to 25% by weight of either cement. The tensile adhesion were determined at 28 and 90 days after various conditioning conditions of the samples. The influence on the flexibility of mortars was also assessed. In small substitution levels, fly ash replacement increased the tensile adhesion strength. The results indicate that the optimal amount of fly ash and granulated blast furnace slag additive replacing a given amount of cement allows to obtain adhesive mortars for tiles with high functional parameters.

Development of Chemical Compositions of Artificial Cement Stone Using Coal and Waste Rock

The use of cement support is being currently introduced during drivage. The correct, competent choice of grouting mortar formulations according to mining and geological conditions and their timely use can reduce unproductive labor, time and money, increase productivity and timely commissioning of the mine. An analysis of chemical composition of grouting mixtures using coal and waste rock required for their production was carried out using IR spectroscopic, chemical and X-ray fluorescence analyzes.

Potential CO2 reduction and cost evaluation in use and transport of coal ash as cement replacement: A case in the Philippines

Coal ash can potentially be utilized as partial replacement for cement in concrete and mortar formulations. The use of coal ash can lessen the cost and energy production, and reduce the impact on the environment. At present, the annual coal ash generation amounts to ~2.78 Mt and may reach to ~13.02 Mt by 2035 in the Philippines. If coal ash is utilized as clinker replacement in the production of cement at a clinker-to-cement ratio of 0.7, GHG emissions can potentially be reduced to at least ~1.26 Mt CO2_eq in 2018 and could further be reduced by ~5.89 Mt CO2_eq by 2035 when surplus coal ash is utilized as partial cement replacement in concrete mixtures in concrete batching plants. As transport of coal ash can also result in GHG emission owing to fuel combustion, a critical distance is calculated in order to achieve positive net reductions. Critical distance is obtained by comparing the emission on coal ash transportation with that of cement production, while taking into consideration the emissions of the return trip. Thus, transporting the coal ash is limited to a distance of ~2841 km. Existing concrete batching plants are situated within 2,000 km from existing coal-fired power plants, where the transport of coal ash to these plants would not result in additional emissions but instead result in annual net reduction of GHG. Further, the cost of coal ash per bag varies according to the distance travelled and is much lower than the cost of cement per bag.

Use of supplementary aggregates in mortars produced using a novel lime-drying technique

Formulated lime mortars suitable for long-term storage in silos or bags can be produced by adding quicklime to wet, as-received quarried sand. However, sands with high water content may require the addition of more quicklime that would alter the mortar proportioning. This work investigates the possibility to replace part of the lime-dried sand with dry, crushed, mixed glass cullet and calcium carbonate aggregate to allow greater control over mortar formulations. It is shown that the use of glass yields a similar or slightly weaker product, depending on curing regime, than the control while calcium carbonate generates the strongest mortar.

Fabrication of novel formulations from rigid polyurethane foams and mortar for potential applications in building industry

Rigid polyurethane (PU) foams are widely used in modern life owing to excellent strength and weight carrying capacity. Most of the rigid PU foams in the market are based on polypropylene oxide (PPO) and methylene diphenyl diisocyanate. Amine catalysts, especially tertiary amines, are used to balance both the gelling and gas-foaming reactions, responsible for foam formation. The objective of present work is to prepare rigid PU foams from PPO based polyol and 4,4′- methylene diphenyl diisocyanate (MDI). The morphological and mechanical properties of polyurethane foam using tertiary amine and water blowing agent have been investigated. Moreover, acoustic and thermal insulation of polyurethane foam ordinary Portland cement mortar formulations were also examined. The results indicated that polyurethane ordinary Portland cement mortar formulations have good sound absorption and thermal insulation characteristics compared to blank formulations.

Alkaline activation of high-calcium ash and iron ore tailings and their recycling potential in building materials

Abstract Alkali-activated materials are agglomerates obtained from the alkaline activation of aluminum- and silicone-rich precursors. The most popular precursors for this type of activation are low-calcium fly ashes, blast furnace slag, and metakaolin. However, both high-calcium ashes (HCAs) and iron ore tailings (IOTs) are interesting wastes that can be investigated as precursors because of their available volume and environmental impact during their final deposition. Therefore, by performing tests of compressive strength, FTIR spectrometry and scanning electron microscopy, we sought to identify the products formed during HCA and IOT activation without thermal treatment. Nine mortar formulations with different HCA and IOT proportions were developed using sodium hydroxide and sodium silicate as activators. Thus, using FTIR spectrometry, we observed the reaction between the industrial wastes. Additionally, the compressive strength result suggested that the material could be used as compressed blocks in masonry walls for the development of more environmentally friendly building materials, which would mitigate the impact of waste disposal and convert industrial solid waste into value-added products.

Microstructural Modeling of Rheological Mechanical Response for Asphalt Mixture Using an Image-Based Finite Element Approach.

In this paper, an image-based micromechanical model for an asphalt mixture’s rheological mechanical response is introduced. Detailed information on finite element (FE) modeling based on X-ray computed tomography (X-ray CT) is presented. An improved morphological multiscale algorithm was developed to segment the adhesive coarse aggregate images. A classification method to recognize the different classifications of the elemental area for a confining pressure purpose is proposed in this study. Then, the numerical viscoelastic constitutive formulation of asphalt mortar in an FE code was implemented using the simulation software ABAQUS user material subroutine (UMAT). To avoid complex experiments in determining the time-dependent Poisson’s ratio directly, numerous attempts were made to indirectly obtain all material properties in the viscoelastic constitutive model. Finally, the image-based FE model incorporated with the viscoelastic asphalt mortar phase and elastic aggregates was used for triaxial compressive test simulations, and a triaxial creep experiment under different working conditions was conducted to identify and validate the proposed finite element approach. The numerical simulation and experimental results indicate that the three-dimensional microstructural numerical model established can effectively analyze the material’s rheological mechanical response under the effect of triaxial load within the linear viscoelastic range.

Influence of treated mud on free shrinkage and cracking tendency of self-compacting concrete equivalent mortars

The present work aims at studying the formulation and characterization of self-compacting concrete equivalent mortars, using calcined mud from the dredged sediments brought from the dam (Western Algeria) and fly ash from the Central Thermal EDF (France). Three SCCEM samples were prepared; a control mortar sample and two mortar samples containing 22% of mineral additions, with a ratio W/B = 0.47. The analysis of the experimental results obtained indicates that mortars comprising calcined mud develop greater compressive strengths than those containing fly ash. Regarding free shrinkage, mortar with calcined mud is characterized by an autogenous shrinkage similar to those of control and fly ash mortars. However, it is more sensitive to total shrinkage and drying as compared to the other mortars. Under the conditions of restrained shrinkage, control and calcined mud mortars are more sensitive to early cracking than mortar based on fly ash.

Rheology of lime pastes with biopolymer-based additives

The use of industrial limes implies obtaining mortar pastes with worse plasticity and workability compared to lime putties. To overcome this inconvenience, a great number of additives can be used, the majority of them being plasticisers and water-retaining agents. In this work three natural polysaccharides with hydrogel properties (agar–agar, alginate and hyaluronate derivatives) were added to dry-hydrated and natural hydraulic limes to investigate their influence on the rheology of the lime suspensions, as a function of the mixing and dissolving procedures, the additive type and concentration, and the type of lime. Rheological measurements have shown that the yield stress and viscosity of the lime pastes are increased if the additives are pre-mixed with water before adding the lime powder. All additives significantly increase the rheological parameters of the natural hydraulic lime pastes (with a maximum additive concentration of 0.2 g in 1 L of water) but only sodium hyaluronate is effective when mixed with dry hydrated lime. Notwithstanding this, sodium hyaluronate-lime pastes have shown a time-dependent behaviour that must be taken into account during mortar formulation and use. This study lays the foundations for the development of new sustainable lime mortars made with additives derived from natural sources.

Bio-inspired self-healing cementitious mortar using Bacillus subtilis immobilized on nano-/micro-additives

Bio-inspired self-healing strategies are much innovative and potentially viable for the production of healable cement mortar matrix. The present research explores the feasibility of gram-positive “Bacillus subtilis” microorganisms in the effective healing of nano-/micro-scale-induced structural and non-structural cracks. The main concern related to the survival of such microorganisms in cementitious environment has been successfully addressed by devising proficient immobilization scheme coherently. The investigated immobilizing media includes iron oxide nano-sized particles, micro-sized limestone particles, and milli-sized siliceous sand. The effect of induced B. subtilis microorganisms immobilized on nano-micro-additives was analyzed by the quantification of average compressive resistance of specimens (ASTM C109) and healing evaluation. The healing process was mechanically gauged by compressive strength regain of pre-cracked specimens after the healing period of 28 days. The pre-cracking load was affixed at 80% of ultimate compressive stress “[Formula: see text]” while the age of pre-cracking was kept variable as 3, 7, 14, and 28 days to precisely correlate healing effectiveness as the function of cracking period. The healing mechanism was further explored by examining the healed micro-crack using field emission scanning electron micrographs, energy dispersive x-ray spectrographs, and thermogravimetry. The results revealed that B. subtilis microorganisms contribute extremely well in the improvement of compressive strength and efficient healing process of pre-cracked cement mortar formulations. The iron oxide nano-sized particles were found to be the most effective immobilizer for preserving B. subtilis microbes till the generation of cracks followed by siliceous sand and limestone particles. The micro-graphical and chemical investigations endorsed the mechanical measurements by evidencing calcite precipitation in the induced nano-/micro-cracks as a result of microbial activity.