Adhesive Mortars Research Articles

The feasibility of recycling marble & granite sludge in the polymer-modified cementitious mortars Part A: In polymer-modified cementitious adhesive mortar

In the present scientific article, a potential assessment and feasibility study of the recycling process of marble and granite sludge into the system of pre-packed polymer-modified cementitious mortar products has been investigated instead of being disposed of or landfilled. Therefore, several polymer-modified mortar formulations were designed to explore the inclusion effect of marble and granite sludge waste on the overall performance of the prepared mortar formulations in the application area of the polymer-modified cementitious adhesive. In this work, starting raw materials and hardened mortar specimens (28 days) of the prepared mortar formulations were well-characterized by different scientific techniques, including X-ray fluorescence for chemical oxides composition, X-ray diffraction for mineral phases composition Fourier-transform infrared (FTIR). To achieve the study's goals, different percentages of marble and granite sludge were incorporated into the prepared mortar formulations in the range of 0%, 5%, 10%, 15%, 20%, 25%, and 30% to replace the used silica sand in each formulation. The results showed that the marble and granite sludge waste is mainly composed of calcite and quartz minerals, with an average particle size of 4.86 µm. The results also showed an improvement in the workability, performance, and adhesion strength of the prepared polymer-modified cementitious adhesive mortar formulation upon using the optimum sludge addition percentage. Moreover, the experimental results show that the compressive and flexural strength of the prepared mortar formulations were also enhanced by increasing the sludge content.

Bond stress distribution in adhesive anchor systems: Interplay of concrete and mortar creep

The safe design of fastening systems, especially considering the multi-decade performance, relies on a thorough understanding of mechanisms and processes that lead to excessive deformations or even failure in course of time. According to current design guidelines and standards, adhesive anchor system are designed based on the uniform bond model. The uniform bond model is a generally good approximation of the real stress distribution during short-term testing and for loads close to the pull-out capacity of the system. However, both concrete and adhesive mortar are characterized by pronounced time-dependent deformation, especially at elevated temperatures. Thus, noteworthy shear stress redistributions are expected due to creep in course of a structure’s life-time. Depending on the level of stress redistributions potentially critical stress levels may be reached locally, triggering progressive failure. Therefore, it is quintessential to understand bond stress redistribution phenomena in adhesive anchor systems under sustained load. Unfortunately, it is experimentally impossible to decouple the intertwined effects of concrete and adhesive creep. Thus, in this study a numerical approach is adopted. The response of concrete is modeled by a discrete meso-scale damage model in combination with the micro-prestress solidification theory coupled to a hygro-thermal chemical analysis while the adhesive layer is represented by a visco-elastic shear stress–slip law. After separate calibration of concrete creep and creep of the visco-elastic interface the obtained model is validated on independent experimental data on anchor systems. Finally, the established computational framework is utilized to virtually isolate concrete creep, adhesive creep and study their mutual interaction. Results show strong antagonistic redistribution mechanisms driven by concrete and adhesive creep with varying dominance depending on the investigated time-scale.

Permeability of concrete with recycled aggregate coating treatment

The effective use of construction waste is of great significance to the construction of a sustainable society. This study investigated the permeability of recycled aggregate concrete with different qualities. The recycled aggregates were treated with crystallizing agent. The improvement effect of crystallization was evaluated by rapid chloride ion migration test and electron microscope observation. The results show that calcium silicate hydrate was generated by the reaction of crystallizer and hydration product in the adhesive mortar, which effectively improves the chloride ion impermeability of reclaimed aggregate concrete.

Analysis of Deformation and Stresses of a Lightweight Floor System (LFS) under Thermal Action.

The lightweight floor system (LFS) with a heating coil is one of many types of radiant heating systems. It differs from most of the others, as it has a much higher thermal efficiency at low flow temperature. To verify whether adhesive mortars can safely connect the ceramic floor with the insulating substrate, the deformations and stresses values of all light system layers under thermal action should be checked and compared to their maximum strengths. For this purpose, an LFS test field was conducted using the strain gauges and digital measurement techniques, and floor displacements and deformations were determined. The results obtained from the tests were confirmed by finite element method calculations. It was also found that the stress of each floor component was much lower than their strength. This proves that the LFS with a heating coil, without metal lamellas, meets the safety regulation for use. The results of the analysis can be useful in the design of heated/cooled LFSs.

Analysis of the influence of partial replacement of mineral aggregate by basaltic rock dust on the production of industrialized adhesive mortar

The production of adhesive mortar uses large proportions of sand, causing undesirable environmental impact as this is a finite resource. In recent years, the insertion of civil construction waste in cement matrixes has intensified with the objective of replacing sand in the mortar manufacturing process. Therefore, in this study, the proportions of 5%, 10%, 15% substitution of the mineral aggregate by basalt dust waste in the production of industrialized adhesive mortar were adopted. The reference mixture of 1:3 (cement: sand) was adopted and the water/dry material ratio was set at 0.20. The adhesive mortars produced in the tests to determine the consistency index, water retention, mass density, open time, tensile strength and water absorption by capillarity were analyzed. The results were satisfactory, demonstrating that it is feasible to use the waste as a substitute for sand in the production of industrialized adhesive mortars.

Laboratory-based investigation of the materials' water activity and pH relative to fungal growth in internally insulated solid masonry walls.

This project investigated fungal growth conditions in artificially contaminated interfaces between solid masonry and adhesive mortar for internal insulation. The project comprised several laboratory experiments: test of three fungal decontamination methods; investigation of development of fungal growth in solid masonry walls fitted with five internal insulation systems; and investigation of volatile organic compounds (VOC) diffusion through materials and whole insulation systems. One aim was to examine whether the alkaline environment (pH>9) in the adhesive mortars could prevent fungal growth despite the water activity (aw ) in the interface exceeds the level (aw >0.75) commonly considered critical for fungal growth. The findings indicate that do-it-yourself decontamination solutions were inadequate for removal of fungal growth, while professional solutions were successful. However, the choice of decontamination method was of minor importance in the case of application of internal insulation with high pH adhesive mortar, as the high pH adhesive mortars were found to inactivate existing growth and prevented spore germination during the experimental period. The three tested VOCs were capable of diffusing through most of the examined products and could potentially affect the indoor air quality.

Hardening process of polymeric adhesive mortars: Approach by phase angle analysis from oscillatory rheometry

The main goal of this work was to study the viscoelastic behaviour of cement-polymer fresh mortar using an oscillatory rheometer to compare the influence of polymers percentage (%P), aggregate/cement (A/C) and water/solid (W/S) ratios on hardening process mechanisms of polymeric mixes evaluating the phase angle. A Brazilian Portland cement type CPII-F-32, limestone sand and two usual polymers, namely herein as latex (ethylene vinyl acetate – EVA) and cellulose ester (Methyl Hydroxyethyl Cellulose- MHEC) were used. For the experimental analyses, eleven mortars mixtures were tested using different values of aggregate/cement volumetric ratio (A/C), polymer percentage (%P) in relation to the cement mass and water/solid materials ratio (W/S). It was used three values of %P (4%; 5.5% and 7%), five values of A/C (2.5; 3.5; 4.5; 5.5 and 6.5) and tree initial moisture ratio (0.56; 0.68 and 0.79). From the experimental tests it was possible to conclude that the moisture rate stands out as the most influential parameter for changing the phase angle of the mixture during the time testing, the use of oscillatory rheometer method could be applied for evaluation of physical properties changing like the initial hardening process of adhesive mortar in suspension.

Influence of cement with different calcium sulfate phases on cementitious tile adhesive mortars: Microstructure and performance aspects

Cement is generally used as a mineral binder in construction materials. The components formed as a result of the reaction between cement and water give physical strength to construction products. This reaction is influenced by the mineralogical composition of the cement. The clinker composition does not vary greatly for ordinary Portland cement. However, the calcium sulfate composition may vary from manufacturer to manufacturer, and even from batch to batch, depending on the effect of heat dissipation during the process of grinding the clinker with calcium sulfate. The type of calcium sulfate affects the hydration reaction and performance properties of cementitious tile adhesive (CTA). In this study, the hydration behavior and performance of CTA samples prepared from cement containing different calcium sulfate forms were investigated. The developed microstructures were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), and calorimeter, while the performance was tested according to EN 12004 standards.

Hygrothermal assessment of diffusion open insulation systems for interior retrofitting of solid masonry walls

The present project investigated the hygrothermal performance and risk of mould growth in solid masonry walls fitted with three diffusion-open capillary active interior insulation systems installed in containers with a controlled indoor climate. The project was carried out as a large experimental study in two 40-feet reefer containers reconfigured with 24 holes (1 × 2 m), in which solid masonry walls with embedded wooden elements were installed. The focus of the study was on the conditions in the interface between the masonry and the interior insulation, and in the embedded wooden elements. The effect of exterior hydrophobisation was also investigated. Relative humidity and temperature were measured at several locations in the test walls over a period of four years. The findings indicate that exposed walls with interior insulation and high indoor RH performed poorly in terms of the risk of mould growth. Combined with exterior hydrophobisation against driving rain, the semi diffusion-tight insulation system performed better than the highly diffusion-open systems. Good performance was observed for the semi diffusion-tight polyurethane foam insulation with calcium silicate channels combined with exterior hydrophobisation. The effect of hydrophobisation varied with the orientation. Mould observations found no growth in the interface in most walls, probably because the high alkalinity of the adhesive mortars and scarce nutrition prevented growth. Growth was however found in some walls having low alkalinity and possibly available nutrition. Little correlation was found between on-site and modelled mould growth.

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.

Application of surface modifiers in ceramic tile to improve adhesion strength with mortars

Nowadays, ceramic floor or wall tiles have been composed mainly of large ceramic tiles with low water absorption, which requires a greater need for bond strength between the tile and the adhesive mortar. Some researchers argue that adhesion is obtained mainly by mechanical interlocking, while othersclaim that adhesion is obtained mainly by increasing the contact surface. To provide this increase in the contact surface, some studies indicate the use of surface modifiers on the back of the ceramic plate. Thus, this research aimed to evaluate the influence of surface treatment on tensile strength. The research showed that factors such as the polymer content of the adhesive mortar, the absorption and the roughness of the ceramic back were more influential in the tensile strength than the use of the mentioned surface treatments.

Environmental assessment of valorisation alternatives for woody biomass ash in construction materials

Ash generated during the combustion of woody biomass for energy production is an industrial waste that should be properly managed in order to minimise the respective environmental impacts. Woody biomass ash valorisation in construction materials to replace conventional materials is an alternative that has proven to be technically feasible. On the other hand, it can present potential environmental impacts that should be evaluated to support the choice of more sustainable alternatives. Thus, the purpose of this work is to assess the potential impacts of woody biomass ash valorisation of through incorporation in construction materials using life cycle assessment. The valorisation alternatives consider the incorporation of woody biomass ash in cement mortars, adhesive mortars, concrete blocks, and bituminous asphalts. In addition, a base scenario consisting of ash landfilling is also assessed. Four types of woody biomass ashes were considered, namely fly and bottom ashes generated in a vibrating grate and fly and bottom ashes generated in a fluidised bed. The impact assessment method used is that suggested in the International Reference Life Cycle Data System for selected impact categories. The results showed that the impacts of ash transport and pre-processing and the impacts of producing the avoided materials are factors that affect the net impact of the valorisation scenarios and should be considered in the end-of-life management of biomass ash. Nevertheless, all valorisation scenarios had a lower impact than landfilling in all the impact categories under study, resulting in a significant decrease of the environmental impacts in some scenarios.

Investigation of usability of quarry dust waste in fly ash-based geopolymer adhesive mortar production

Crushed-stone dust is a harmful waste product of crushed-stone aggregate concrete production. It has no added value and is disposed of by washing in well-organized facilities. This study experimentally investigated the geopolymer-based adhesive mortar in order to use crushed-stone dust as a building material at the best rates. Fly ash (FA) was used as the geopolymer binder and sodium silicate (SS) and NaOH were used as alkali activators. NaOH was used in three different molarities (3M, 6M and 12M). Two different materials were used as adhesive mortar mineral filler: 100% quarry dust and quarry dust mixed with silica sand at a ratio of 1/3. Geopolymer adhesive mortars were cured in an oven at 80 °C for 1, 3 and 5 h. Bulk density, apparent density, water absorption, apparent porosity, capillary water absorption, compressive strength, flexural strength, tensile adhesion and rheology experiments were performed on adhesive mortar specimens. All series had higher tensile adhesive strength than the standard. 100% of the waste material was used with the binder and mineral filler, and 33% silica sand addition made a positive contribution to some mortar properties.

Effects of different test apparati and heating procedures on the bond properties of post-installed rebar connections under elevated temperatures

The use of chemical bonds to fasten reinforcement bars in existing concrete structures has been widely developed in the previous years, showing in many cases higher bond values compared to cast in rebars due to better performance of the adhesive mortar. However, at elevated temperatures the concrete-adhesive bond tends to weaken endangering the construction under a fire situation. The paper presents the result of an experimental campaign carried out at Scientific and Technical Center of Building and Politecnico di Milano laboratories on a post-installed connection using vinyl-ester polymer. This paper aims to investigate the behavior of rebar connections through chemical resin when subjected to high temperatures, with particular emphasis on the effects of water vaporization in the concrete and on the influence of heating procedures on the mortar post-curing. Two different pull-out test procedures were adopted, differentiating each other for the loading and heating sequences. Results showed that specimens with the same water content may present different thermal gradients; however, comparable mean temperatures along the bar are detected for the same values of applied load. Moreover, for a given temperature, the increase of bond strength with exposure time showed a convergence towards an asymptotic value.

Skin formation in adhesive mortars evaluated by MRI and interfacial rheology

The formation of a dry skin on fresh adhesive mortars is an undesirable side effect of polymeric admixtures that are indispensable to this type of material. This investigation adapted a classical interfacial rheology technique to study the evolution of the skin's properties. The introduced technique and magnetic resonance imaging (MRI) were used to evaluate the effects of cellulose ether (CE) content and degree of substitution's (DS) on skin formation of mortars prepared with two types of cements. MRI results of water distribution within the sample over time indicated a dryer zone formed at the exposed surface that is dependent on CE content. Oscillatory interfacial measurements pointed out that skin's storage modulus (G′) was firstly dominated by water loss, presenting smaller increasing rate with higher CE content, then an inversion occurred due to polymer properties predominance. Wind conditions accelerated the effects of CE on G′ kinetics of the skin.

Assembly of Ceramic Coverings on Gypsum Surfaces

Ceramic claddings in the buildings are often tiled on gypsum surfaces, which mainly consist of plasters made of ready dry mixes and walls made of gypsum blocks. One should know about their specific properties, such as absorbency, smoothness and lack of chemical bonding with cement based adhesive mortars. This paper discusses the subject of assembly of ceramic claddings on such substrates and shows examples of damages caused by executive errors. The first part of the paper describes methods of preparing the surface before assembly of ceramic claddings, with particular emphasis on the proper surface priming. The principles of choosing the right mortar for tiling works are also presented. In the second part of the paper, examples of assembly errors are presented, as a result of which the ceramic claddings become detached from the gypsum surfaces. The results of measurements and observations have been described and the reasons for failure of wall claddings have been given.

Thermal-Humidity Parameters of 3D Printed Wall

The purpose of the external walls is to secure the internal microclimate of the building. External walls not only must have proper strength and durability but also prevent heat escape, overheating during summer, protect from noise and increase of humidity. The main parameter that describes the thermal properties of external walls is the heat transmission coefficient U [W/(m2⋅K)] determined in accordance with EN ISO 6946:2008. One of most recent technology of constructing walls is the additive manufacturing. The aim of the study is to determine the thermal properties of wall printed with use of High Performance Concrete and insulated with mineral wool. The study determines the temperature and vapour pressure inside the wall and presents calculations of thermal factor. The study compares the characteristics of traditional walls with 3D printed elements. The tests have shown that insulating printed structures does not pose any difficulty. Corrugated structure of printed walls increases the adhesion of adhesive mortar. Proposed tests are the starting point for further studies on the thermal-humidity of 3D printed structures. The main goal is to propose a solution for cheap, efficient insulation technology for 3D printed structures.

Principles of polymer film in tile adhesive mortars at early ages

Principles of polymer film in tile adhesive mortars at early ages had been investigated by three redispersible polymer powders under SEM and CT. Morphology and distributions of polymer film of these redispersible polymer powders(EVA, E/VA/VE and E/VCVL) both in fresh cement pastes after natural stratification and in hardened C3S pastes were random and regional. Intergrowth relationship between polymer film and hydrates was universal and this intergrowth in microzones should be regarded as one unique microstructure which named ‘hybrid intergrowth zone, HIZ’. Inside these HIZs, there were two types of polymer film, ‘pure type’ only containing polymer particles and ‘hybrid type’ containing both polymer particles and inorganic particles. There were enlargement effects of redispersible polymer powders on porosity, average pore diameter and mean pore diameter of pores in cement mortars. Based on mean sphericity of CT, the connectivity of pores in cement mortars had been improved by redispersible polymer powders. 3D shapes of pores had also been changed by redisperisble polymer powders. Effects of redispersible polymer powders were quite different.

Influence of Glass Residue Addition on the Properties of Adhesive Mortar

The use of glass residue as a finely ground mineral additive, in partial replacement of cement and aggregates, is a promising direction for recycling. This work aimed to analyze the influence of residues from the glass cutting process on adhesive mortar, as partial replacement of cement and small aggregates. The powdered glass was used in amounts of 10, 15 and 20 wt% in substitution for Portland cement and, in another moment, in substitution for small aggregates. It was verified that the substitution enhances the adhesion resistance of the mortar with increasing curing temperature.

Concrete creep and shrinkage effect in adhesive anchors subjected to sustained loads

The safe design of fastening systems requires an accurate understanding of all time-dependent phenomena that may lead to damage or even failure during its service life of typically 50 years. Generally, safety and serviceability requirements are ensured through rigorous experimental testing during the approval phase. In the case of time-dependent phenomena, or more specifically the behavior under sustained load, the common practice of directly testing all critical service conditions fails. The long-term response can only be approximated e.g. by short-term structural system tests that are extrapolated to the full life-time utilising empirical models as required by current guidelines. These are based on the assumption of uniformly distributed bond stress along the anchor, attribute all creep deformations to the adhesive mortar, neglect the concrete creep contribution, and assume a stationary creep process represented by a power-law. Generally, it can be assumed that reliable predictions of the time-dependent behavior of complex systems can only be obtained by models that are derived from a systematic investigation of all involved factors and their interaction. In this study, specifically the effect of concrete creep and shrinkage on the long-term behavior of adhesive anchor systems, based on extensive experimental data and numerical analyses, is investigated. A state-of-the-art computational framework is applied which can explicitly model the underlying physical and chemical mechanisms at early age and beyond. The well-established Lattice Discrete Particle Model (LDPM) describes the time-dependent mechanical response of the structure considering the local maturity of concrete, temperature, and moisture content. After calibration and validation of the numerical framework, structural deformations owing to concrete creep, bond stress redistributions over time, and the gradual development of damage at higher load levels are discussed.