Mortar Mixtures Research Articles

Exploring Lime Mortar Microstructure: Investigating the Impact of Mixed-in Additives and their Role in Salt Efflorescence Inhibition

This study presents the analysis of the crystallization impact in four lime-based mortar mixtures in order to determine the extent of decay during salt crystallization, affected by the use of additives and change in microstructure. For this purpose, non-destructive micro-computed tomography was used to monitor salt crystallization in lime mortar cores. This technique allowed tracking of salt precipitation after accelerated weathering steps and further enabled the localization of damage due to salt crystallization in both time and space. Results indicate that the internal 3D microstructure of the lime mortars is greatly influenced by the type and the amount of additive used. Polyacrylic acid (PAA) acted as a superplasticizer and air entrainer in the mixture, resulting in the formation of larger air voids, which led to a decrease in compressive strength. Mobilization of salts within the mortar matrix was observed, causing accumulation and cracking of the mortar wall towards the end of the weathering experiment.

Avaliação do desempenho de argamassas autonivelantes utilizando resíduos de fosfogesso e cerâmica branca

Abstract This study investigates the properties of self-leveling subfloor mortar mixtures with natural and calcined phosphogypsum waste in the form of calcium sulfate called anhydrite and white ceramic, by replacing 50% of the mass of Portland cement CP II Z-32. The effects of using waste were evaluated in the fresh (initial fluidity, flow retention, regeneration time, setting time, and heat of hydration) and hardened (compressive and flexural tensile strength, density, water absorption, void ratio, linear shrinkage, and tensile adhesion strength) state. The optimized mixture at a 1:1.5 cement/sand ratio (by mass) with 50% white ceramic had a 32.66 ± 4.26 MPa compressive strength at 28 days, low shrinkage and heat of hydration, showing the best performance among the wastes studied. In the calcium sulfate mortars, the mixtures with anhydrite showed better results for compressive and flexural tensile strength and tensile adhesion strength, with the waste calcination being beneficial.

3D басып шығару арқылы қалдықтар негізінде бетонды қалыптау технологиясының ерекшеліктері

This article provides an overview of world practice in the field of additive technologies and features of waste-based concrete molding technology using 3D printing in the construction industry. The initial stage of the formation and development of additive manufacturing processes in construction 3D printing technology of construction by multilayer extrusion is one of the technologies of concrete molding and regulatory documentation and literature sources are analyzed to determine the place of the technology under study in additive manufacturing processes. Based on the literature review and analysis, the need to ensure optimal rheotechnological properties in the construction 3D printing technology in order to achieve maximum efficiency is determined. The article formulates the main technical requirements for the concrete mix in terms of performance and installation time, as well as the features of the choice of concrete composition. It is possible in principle to obtain fine-grained concretes with specified characteristics based on Portland cement. The results of a study using the methodology of mathematical planning and analytical optimization of the results are presented, the purpose of which is to create scientific prerequisites for the promotion of 3D concrete-based construction and the results of a study of the rheological and physico-mechanical properties of modified concrete with the addition of special alkali-resistant fiberglass for three-dimensional construction printing. In this case, the rheological and technological characteristics of the structure of a cement-sand mortar mixture are shown for its shape stability, plastic strength, adhesion, and defect. In this regard, the first stage analyzes the regulatory documentation, as well as the processes and methods of construction 3D printing, the state of the additive manufacturing market. At the second stage, the composition of raw materials mixtures used in construction 3D printing technology is studied.

Lime-activated one-part geopolymer mortars from construction, demolition and industrial wastes

This work focused on the production of one-part geopolymer mortars from construction and demolition wastes (CDW) blended with steel slag. Previous related studies on geopolymer production from CDW utilized conventional two-part geopolymers comprised of highly alkaline activator solutions and CDW materials. Thus, the study's significance consists in producing high-strength (≥35 MPa) ambient-cured mortars from CDW with predominantly concrete waste by replacing conventional highly alkaline activator solutions with an environmentally-friendly alkaline activator, Ca(OH)2 powder. Four mortar mixtures were produced with CDW contents ranging from 50 to 65 % dry weight, varying the brick waste content from 3 to 18 %. The effect of elevated temperature (40 °C) curing was also considered. The results showed that 55 % CDW content had optimum performance across all parameters studied such as compressive and flexural strengths, setting time, as well as changes in nuclear magnetic resonance (NMR)-determined pore structure (porosity and mean pore size) and x-ray diffraction (XRD)-determined degree of crystallinity over time. It had 28-day compressive and flexural strengths of 42 and 5.8 MPa, respectively, and initial and final setting times of 25 and 50 min. The importance of sufficient brick waste content in the geopolymer mixtures for effective mechanical performance is highlighted. The inclusion of concrete waste in powder form reduced compressive strength under ambient curing but improved performance at 40 °C curing. It is concluded that sustainable structural mortars can be produced by ‘just adding water’ to an optimized CDW mixture with predominantly concrete waste blended with brick waste and slag and activated by powdered Ca(OH)2.

Вплив механохімічної активації композиційного цементу на міцність будівельного розчину

The article discusses issues related to the use of technology for the production of mortar mixtures and mortars based on high-speed mixers, the operation of which causes mechanochemical activation of the binder. The rotary counterflow mill used in the work acts as an activator of the surface zone of both Portland cement grains and quartz sand grains and, thus, contributes to the intensification of the processes of structure formation of cement paste and mortar based on it. Based on the fact that one of the promising ways to reduce the cost of cement activation is to reduce the energy intensity of the dispersion process itself, the use of relatively low-energy rotary mills can be considered as an effective way to increase the activity of the binder. After the joint activation of Portland cement and unground quartz sand (the amount of which was adjusted from 0 to 50 % of the cement mass; activation period - 300 seconds), samples were made from equal-viscosity cement paste. It was experimentally established that the maximum strength of cement stone at 28 days of age was achieved when using composite cement with a 20 % content of activated sand. To determine the influence of the studied factors, such as the consumption of mechanically activated composite binder, the concentration of superplasticizer C-3 (0...1,5 %) and the consumption of microsilica (0...10 %) on the strength of the mortar in 2 and 28-day old, a 3-factor experiment was conducted. It was established that in the studied hardening period, the content of mechanically activated composite cement has the greatest influence on the compressive strength for the studied mortar compositions (from 1:3 to 1:1). The next most important influence on the strength of the mortar is the consumption of superplasticizer C-3. The increase in compressive strength of a mortar from the introduction of microsilica into its composition does not exceed 10-15 %. The combined effect of mechanical activation of the binder and the use of the C-3 additive ensures an increase in the strength of the mortar (mortar composition 1:1) at 28 days of age from 43,5 MPa (non-activated binder; no C-3 additive) to 63 MPa, that is, almost by 45 %. For a mortar of similar age with a lower consumption of composite cement (mortar composition 1:3), mechanical activation of the binder in the presence of 1,5 % C-3 additive ensures an increase in the compressive strength of the mortar from 21 MPa (non-mechanically activated binder; C-3 = 0 %) to 39 MPa.

Optimizing The Na2O Dosage to Develop Mechanical Properties of Ferrochrome Slag-Based Alkali-Activated Mortar

The purpose of this study is to investigate the effect of alkali dosage on the compressive strength and ultrasonic pulse velocity of alkali-activated ferrochrome slag/Portland mortar. A total of eight mortar mixtures were produced. While four of the mixtures contain 15% Portland cement, the binder material of the other four mixtures consists entirely of ferrochrome slag. These alkali-activated mortar mixtures were prepared with four alkali dosages (4, 6, 8, and 10). The alkali modulus of all mixtures was kept constant at 1.4. Compressive strength and ultrasonic pulse velocity tests were performed to examine the effect of alkali dosage on both PC-substituted and PC-free mortars. As the alkali dosage increased, the compressive strengths of both PC-substituted and unsubstituted mortar specimens increased. It was seen that the critical alkali dosage of the alkali-activated mortar was 6%. Compressive strength and UPV values of the mortar specimens increased significantly with PC substitution

Class-C fly ash from coal as a partial substitute in cement-based paste and mortar design mix – A case in the Philippines

An indirect way to minimize greenhouse emissions from the cement industry is partially substituting cement with coal fly ash (CFA). Despite CFA being widely studied, the quality, performance, and water requirements, when used in formulating paste and mortar, vary depending on the source. This study assessed CFA from a power plant in the Philippines as a partial substitute for cement. Paste and mortar mixture were designed to have varying CFA-to-binder ratios (CBR) and water-to-binder ratios (WBR). The effect of CBR and WBR on the consistency and workability of fresh paste and mortars were modeled, adopting multivariate non-linear regression to objectively assess the individual and interactive effects. Properties (compressive strength, density, and voids) of hardened mortar formulated with different CBRs but having normal consistency/workability were determined and assessed. Models generated could be used to estimate the WBR required for formulations to achieve normal consistency/workability. The water requirement for mortar formulation to have normal workability may be predicted based on the WBR for paste formulated to have normal consistency. Increased cement replacement with CFA improved the compressive strength, with replacement up to 20 wt% resulting in better performance than pure cement.

Investigation the effect of nanocarbon tube prepared from tea waste on microstructure and properties of cement mortar.

Environmental contamination and the massive high cost of waste disposal have been a huge concern for scholars throughout the globe, prompting them to alternatives of recycling waste materials in various implementation fields. The rising expenditure on disposal and the shortage of naturally main resources such as aggregate have increased interest in reusing recycled waste materials to manufacture concrete and mortar. The annual consumption of a country's population of hundreds of tons of black tea results in considerable numbers of discarded teabags. These huge quantities are disposed in landfills without being recycled or otherwise used. Moreover, such landfills are considered one of the country's biggest global issues. Therefore, the aim of this experimental work is to investigate the influence of nanocarbon tube produced from tea waste as cement replacement materials in mortar mixtures. Cement mortar mixes contain four replacement levels (1%, 2%, 3%, and 4%) of cement with nanocarbon tube produced from tea waste. The compressive strength, ultrasonic pulse velocity, and water absorption were tested to demonstrate the effect of the nanocarbon tube made from recycled tea waste on the mechanical properties of the mortar mix. The fresh properties such as flow rate were evaluated in accordance to specific standards. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDX) analyses were performed to demonstrate the microstructure of the mixtures. The results show that the fresh properties (flowability) of mortar containing nanocarbon tubes from tea waste were improved with the increase of the replacement ratio. In addition, the compressive strength was improved by substitution of up to 2%. For the other levels of substitution, it decreased with an increasing replacement percentage. In contrast, the density had increased with the increase of substitution levels of the tea waste. Based on the results of the experiments, it seems that the suggested biomixture could increase the compressive strength of the material by up to 2% of the replacement at 28days of curing.

The Use of Pre-Wetting to Improve the Mechanical Behavior of Masonry Mortar Elaborated with Crushed Oyster Shell

In this research, the use of the pre-wetting technique is proposed as an ecological alternative to reduce water absorption in waste oyster shells used in the production of masonry mortar as a partial substitute for natural sand. An experimental study was conducted to assess the properties in both the fresh and hardened states of masonry mortars. Two mortar groups were prepared based on a control mixture, with natural aggregate replaced by crushed oyster shell (COS) in varying proportions. In one group, the COS was pre-wetted, while in the other group, the COS was used at its natural moisture content. The experimental results demonstrated that the pre-wetting process aided in reducing the water–cement ratio (w/c) in the mortar mixture, thereby improving its properties. In both mortar groups, favorable results were observed with respect to capillary water absorption. Although the compressive strength was affected by the incorporation of COS, pre-wetted mortars with substitutions of up to 30% achieved the reference value established in this research. The pre-wetting process proves to be a straightforward and cost-effective technique; it is environmentally friendly and will contribute to decreasing the accumulation of COS in landfills, thereby safeguarding natural material reserves.

Effect of harsh environment on cement mortar containing natural pozzolans

This investigation aims to study the effect of the harsh environment on cement mortar containing pumice powder (natural pozzolana) as a partial substitute for ordinary Portland cement (OPC). The harsh environmental conditions applied in this study consisted of seawater supplemented with 5% of sodium sulfate (Na2SO4). Mortar mixtures were produced by replacing 0%, 5%, 10%, and 20% of the OPC mass with natural pozzolana (NP). Mortar samples were treated under two conditions. First, the mortar samples were immersed in tap water. Second, mortar samples are immersed in harsh environmental conditions. In the harsh environment, mortar samples were subjected to 90 cycles of dry-wet, 48-hour drying, and 48-hour wetting over a period of 360 days. Compressive strength, flexural strength, strength loss, change in length, water absorption, and initial surface absorption tests were performed on specimens aged 7, 28, 90, 180, and 360 days. Besides thermogravimetric and microstructure analysis of cement samples that were conducted at a test age of 180 days. The inclusion of NP as a partial replacement of OPC at a rate of 10% improved the results of compressive and flexural strength and achieved the lowest rates of porosity and water absorption of the mortar samples. The inclusion of NP as a partial replacement for OPC reduced the damage caused by the harsh environment.

Impact of Crushed Natural and Recycled Fine Aggregates on Fresh and Hardened Mortar Properties

Increasing the amount of crushed natural and recycled fine aggregates in mortar and concrete can help to reduce depletion of resources and increase the recycling rate of construction and demolition waste. Differences in particle morphology influence fresh and hardened mortar and concrete properties. The quantitative assignment of this impact to specific characteristics, such as shape or angularity in differentiation to other mix design parameters, is currently scarcely known. Therefore, a multiple linear regression analysis was performed to investigate the impact of crushed natural and recycled fine particles on rheological and strength properties of mortar. The emphasis lies on the impact of differences in shape and angularity, which were quantified by the three-dimensional particle representation obtained from micro-computed tomography. A total of 160 mortar mixtures containing 5 sands of different origins and varying water-to-cement ratios, binder-to-aggregate ratios, and shapes of grading curves were produced. The results indicate that the particle shape and angularity of the crushed natural and recycled fine aggregates had a complex impact on fresh and hardened mortar properties and interacted with other mix design parameters. Careful composition of the aggregate fraction with respect to shape and angularity and their interaction with mix design parameters is necessary to maintain sufficient mortar properties.

Influence of Chopped Carbon Fibers Addition with Different Curing Methods on the Mechanical Properties of Cement Mortar Performance

Sustainability is very important to keep industrial growth and human development going. Concrete is the largest manufacturing material in the world and includes cement as a key bonding agent for developing strength. This paper shows that the use of chopped carbon fiber to reinforce cementitious materials improved the mechanical properties characteristics of the mortar. also proposes appropriate curing conditions for the chosen mortar. The experimental investigation was carried out to evaluate the mechanical properties of cement mortar, The study plan consists of four cement mortar mixtures with ratios include 0%, 0.25%, 0.5% and 1% of chopped carbon fiber volume fraction by weight % of cement using normal water for curing. The effects of four different methods of curing on the mechanical properties of cement mortar that have the best properties from adding chopped carbon fiber were investigated including the convectional curing. 1% carbon fibers showed the best improvement in the mortar strength.

Relating early-age hydration and flow loss of mortar prepared with manufactured sand

Cement-based materials prepared with manufactured sand can exhibit quick loss of fluidity. However, the estimation of the flow loss remains difficult given the variable contents and physiochemical properties of the microfines in various sands. This paper studies the fluidity loss of mortar mixtures made with different manufactured sands varying in mineral composition and content of microfines. The effect of microfines on accelerating the early-age hydration of cement before the deceleration period was evaluated by quantifying the generation of early hydration products. Test results show that the growth of yield stress corresponding to the loss of mini-slump flow of mortar mixtures were mainly determined by the formation of early hydration products, in addition to the volume fraction and packing density of aggregate grains and powder particles. An approach was then proposed that can assess the loss of mini-slump flow of mortar mixtures prepared with manufactured sand, regardless of the type and content of the microfine materials in the sand.

Effect of hemp and basalt fiber on fracture energy of cement-based composites: a comparative study

Fiber-reinforced composites are one of the most used construction materials. Nowadays, some types of fibers like steel, carbon, glass and basalt are commonly used in these composites. However, the production of these fibers consumes natural resources and a high amount of energy. Researchers have started working on natural fibers to reduce commonly used fibers productions’ drawbacks for more sustainable composites. However, the effect of natural fibers on the properties of cement-based composites -especially fracture energy- still needs further research and comparing with the behavior of commonly used fibers. In this study the effect of hemp fiber on the mechanical properties and fracture energy of cement-based fiber-reinforced mortar mixtures was investigated. The results were compared with those of the basalt fiber-reinforced mixtures. The results showed that the flexural strength and fracture energy improved with the use of hemp and basalt fiber compared to the fiber-free mixture. The flexural strength increased up to 10.7% and 19.6% with the inclusion of hemp and basalt fibers, respectively. The mean peak load and fracture energy of hemp fiber-reinforced mortar was higher than those of the fiber-free mixture by 32.2% and 17.9%, respectively. The corresponding values for basalt fiber addition 60.8% and 146.4%.

Study on the Mechanical Properties of Polyurethane-Cement Mortar Containing Nanosilica: RSM and Machine Learning Approach

Polymer-modified cement mortar has been increasingly used as a runway/road pavement repair material due to its improved bending strength, bonding strength, and wear resistance. The flexural strength of polyurethane–cement mortar (PUCM) is critical in achieving a desirable maintenance effect. This study aims to evaluate and optimize the flexural strength of PUCM involving nano silica (NS) using a central composite design/response surface methodology (CCD/RSM) to design and establish statistical models. The PU binder and NS were utilized as input parameters to evaluate the responses, such as compressive and flexural strength. Moreover, machine learning (ML) algorithms including artificial neural networks (ANN) and Gaussian regression process (GPR) were used. The PUCM mixtures were prepared by adding a PU binder at 0%, 10%, 15%, and 25% by weight of cement. At the same time, NS was incorporated into the mortar mixes at 0 to 3% (interval of 1%) by cement weight. The results showed that the simultaneous effect of PU binder at the optimal content and NS improved the performance of PUCM. Adding NS to the mortar mixture mitigated some of the strength lost due to the PU binder, which remarkably reduces the strength properties at a high content. The optimized PUCM can be obtained by partly adding 3.5% PU binder and 2.93% NS particles by the weight of cement. The performance of the machine learning algorithms was tested using performance indicators such as the determination of coefficient (R2), mean absolute error (MAE), mean-square error (MSE), and root-mean-square error (RMSE). The GPR algorithm outperformed the ANN with higher R2 and lower MAE values in the training and testing phases. The GPR can predict flexural strength with 90% accuracy, while ANN can predict it with 75% accuracy.

RHEOLOGY AS A TOOL FOR TECHNOLOGICAL ADVANCEMENTS IN SELF-COMPACTING LIGHTWEIGHT CONCRETE MIXES

This paper outlines a methodology aimed at enhancing the technological performance of self-compacting concrete using lightweight expanded clay aggregate. One of the primary challenges encountered when employing concrete with lightweight aggregate involves displacing expanded clay grains within the solution's liquid phase to ensure necessary fluidity (workability) while upholding high stability (structural viscosity and segregation resistance). To achieve this objective, the rheological parameters of the self-compacting cement matrix have been regulated by deliberately adjusting the functional groups of additives and the microfine mineral filler, employing analytical methods from computer materials science. Through the analysis of rheometric results obtained from investigating various solution mixtures, the most suitable model that describes their rheological behaviour has been identified. The impact of finely dispersed fly ash excipient, a carboxylate superplasticiser, and a stabiliser additive on the rheological parameters of self-compacting lightweight concrete mixes has been established. The inclusion of these complex additives in the composition has enabled substantial alterations in the flow index across a wide range (0,030-0,798). This adaptability allows for the adjustment of the mortar mixture's rheological behaviour throughout a spectrum ranging from «abnormally viscous liquid» to «Newtonian liquid». This approach, examining the singular-factor dependencies' analysis on the coefficients of rheological behaviour models, aids in addressing the primary challenge encountered when using concrete with lightweight aggregate.

EFFECTS OF COMBINATIONS OF LIMESTONE POWDER AND METAKAOLIN ON MORTAR COMPRESSIVE STRENGTH DEVELOPMENT

Cement production is a major contributor to carbon dioxide (CO2) emissions, and concrete is one of the most widely used building materials in the world. To reduce CO2 emissions from cement, supplementary cementing materials have been widely introduced in mortar and concrete mixtures. This research will explore the mechanism that determines the development of compressive strength in mortar made with partly substituted cement and a mixture of limestone powder and laboratory-quenching heat-treated kaolinite clay (also called metakaolin). Metakaolin is rich in Southeast Asian countries and needs further investigation to adopt in cement systems. Limestone powder and metakaolin constitute 45% of the binding cement ingredient by weight (dry). The strength was evaluated using mortar, and the microstructure was determined using paste. The results show that at 28 days, the compressive strength of mortar containing 45% cement substitution by 15% limestone powder and 30% metakaolin with 1% PCE (per B45S 1:2) was 97% relative to the reference mortar. However, due to the impurities in metakaolin, its synergistic interaction is limited, which results in the compressive strength being lower than anticipated.

Load Transferring Characteristics of Expanded Pile with Cement Mortar Mixture for Pipe Pile

Two kinds of interface shear force transmission models of expanded pile are introduced in combination with FRIC subroutine. ABAQUS is used to carry out numerical analysis to study the load transfer characteristics of expanded pile under vertical load. The results show: the load on the top of the pile is transmitted by the strong cohesive force between the pipe pile and the expanded interface. Under the vertical load, the axial stress of the pipe pile in the expanded pile gradually decreases with the increase of depth, and the axial stress of the expanded part increases first and then decreases with the depth. With the increase of pile length, pipe pile diameter or expansion thickness, the axial stress of pipe pile increases as a whole. With the increase of pile length, the axial stress of the expansion body increases gradually, and with the increase of pile diameter or expansion thickness, the axial stress of the expansion body decreases gradually. The axial stress of the pipe pile in the equal core part of the non-equal core expanded pile gradually decreases with the increase of depth, and the axial stress of the expanded body increases with the increase of the pile length.

Hybrid Nucleation Acceleration Method with Calcium Carbonate and Calcium Silicate Hydrate for Fast-Track Construction

This research focuses on achieving early strength of cement-based materials through the hybrid nucleation acceleration method. Through the study of various mortar mixtures, which incorporate components such as ordinary Portland cement (OPC), fine limestone powder (with a particle size of d50: 1 μm), coarse limestone powder (with a particle size of d50: 12 μm), calcium silicate hydrate (C-S-H) nucleation seeding agent, and calcium nitrate (CN), the effect of the hybrid nucleation acceleration method was investigated. When OPC was substituted with 20% fine limestone powder, a strength of 13.5 MPa was achieved at 6 h, whereas the use of coarse limestone powder only yielded 3.5 MPa within the same time frame. The mortar containing 2% C-S-H nucleation seeding agent reached an impressive 16 MPa at 6 h. Meanwhile, through the synergistic combination of fine limestone powder and C-S-H nucleation seeding agent, the 6 h early strength attained an impressive 19 MPa. The micrograph revealed that the hybrid nucleation acceleration method significantly promoted the formation of a dense network of C-S-H within the paste, thus enhancing the packing density. Measuring the heat release demonstrated that the samples accelerated with the C-S-H nucleation seeding agent and fine limestone reached the peak 160 min earlier than the OPC sample, indicating a faster hydration process. The hybrid nucleation accelerated concrete (HNAC) achieved strengths of 20 MPa and 27 MPa within 6 and 8 h, respectively, whereas the 28-day strength surpassed 70 MPa. The concrete equivalent mortar (CEM), derived from concrete, attained a compressive strength of 25 MPa within 8 h, making it suitable for repair applications. The modulus of rupture (MOR) was 7.31 MPa at 8 h and increased to 17.27 MPa at 28 days. Overall, the developed concrete and CEM with the novel hybrid nucleation acceleration method allowed for high early and long-term strength for fast-track construction to be attained.

Investigation of Affecting Factors on Drying Shrinkage and Compressive Strength of Slag Geopolymer Mortar Mixture

Investigation of Affecting Factors on Drying Shrinkage and Compressive Strength of Slag Geopolymer Mortar Mixture