Mortar Mixtures Research Articles

LC3 cementitious binder incorporating microencapsulated phase change materials for self-defrosting traffic surfaces

Exposed surfaces of bridge decks, viaducts and pavements incur ice formation and accumulation of snow in cold seasons, which threatens traffic safety. Mitigating this problem using traditional methods such as deicing salts have caused ecosystem damage and inflicted substantial reinforcement corrosion and surface scaling to bridge decks and pavements, thus compromising their service life and causing colossal economic loss. This paper presents an alternative solution to overcome this problem through the development of a sustainable LC3 cementitious material incorporating micro-encapsulated phase change material (MEPCM) with low phase transition temperature to delay the surface temperature drop and mitigate snow accumulation and ice formation. MEPCM was incorporated in the cementitious matrix at 0 %, 10 % and 20 % by binder mass. Paste and mortar mixtures were prepared to investigate the microstructural, mechanical, physical, and thermal properties. Test results showed that incorporating MEPCM in the LC3 matrix achieved adequate compressive strength. Thermal simulations and visual observations conducted on mortar samples in the laboratory and outdoor exposure showed that MEPCM can effectively regulate the surface temperature of the LC3 matrix and mitigate temperature drops as well as snow accumulation. Analysis of temperature data in the 2023–2024 winter season of Hamilton, Ontario, Canada indicated that the MEPCM incorporated in mortar samples could effectively regulate 40 % of the total days considered and mitigate surface ice formation and snow accumulation, which provides both economic and environmental benefits.

Development of Biodegradable and Recyclable FRLM Composites Incorporating Cork Aggregates for Sustainable Construction Practices

Reducing energy consumption in the building sector has driven the search for more sustainable construction methods. This study explores the potential of cork-modified mortars reinforced with basalt fabric, focusing on optimizing both mechanical and hygroscopic properties. Six mortar mixtures were produced using a breathable structural mortar made from pure natural hydraulic lime, incorporating varying percentages (0–3%) of cork granules (Quercus suber) as lightweight aggregates. Micro-computed tomography was first used to assess the homogeneity of the mixtures, followed by flow tests to evaluate workability. The mixtures were then tested for water absorption, compressive strength, and adhesion to tuff and clay brick surfaces. Adhesion was measured through pull-off tests, to evaluate internal bonding strength. Additionally, this study examined the relationship between surface roughness and bond strength in FRLM composites, revealing that rougher surfaces significantly improved adhesion to clay and tuff bricks. These findings suggest that cork-reinforced mortars offer promising potential for sustainable construction, achieving improved hygroscopic performance, sufficient mechanical strength, internal bonding, and optimized surface adhesion.

Studying of Mechanical Behavior of Waste Materials Modified Cement Mortar

Large-scale environmental problems have been triggered by ceramic tiles from demolished buildings and animal bone waste. Therefore, optimizing their potential for reuse and recycling is an important goal of sustainable solid waste management. The primary objective of this study is to evaluate the feasibility of partial replacement of the fine aggregates in cement mortar with a combination of natural animal bone powder and industrial waste materials which is wall tiles ceramic powder. This study measures thermal and mechanical characteristics. Recycling construction waste is one of many ways to deny waste material from entering landfills and create new eco-friendly material that reduces energy consumption in buildings. Modified mortar cement specimens with 5% up to 25% mixtures were combined using a 1:3 ratio and a 0.5 W/C ratio to see how the ratios would affect the material’s properties. The addition of a superplasticizer boosted the cement mortar’s workability and compressive strength. The compressive strength, flexural strength, density, and thermal conductivity were evaluated for each mortar mixture ratio. Results showed that compared to regular cement mortar, cement mortar combined with 20% bone and ceramic powder wastes reached the optimal replacement percentage. Compressive strength increased by 54% and flexural strength by about 67%. At the 28-day mark, thermal insulation was lowered by 25%.It is concluded from this study that it is possible to use bone waste as a natural material with ceramic waste as an industrial material to modify the insulation and mechanical properties of cement mortar.

Effect of particle size distribution and content of limestone powder on compressive response of high-early-strength cement mortars

This study examined the effect of particle size distribution and content of limestone powder on the compressive response of high-early-strength portland cement mortars cured either in water or under ambient conditions. Nineteen mortar mixtures were classified into three groups based on the particle size distribution of the pulverized limestone powders: L (blaine = 3467 cm2/g), M (blaine = 4710 cm2/g), and H (blaine = 5764 cm2/g). The design equations for the compressive strength gain rates and stress–strain relationship of ordinary portland cement (OPC) concrete were adapted for the present mortars. The test results revealed that the 28-d compressive strength (fc′) of the mortars tended to decrease with an increase in limestone powder content, even for mortars containing 5 % limestone powder with small particle sizes. This contrasts with the common trend of the positive effect of limestone powder on the compressive strength of OPC concrete up to a certain substitution level. Furthermore, mortars containing finer limestone powders exhibited a greater rate of decrease in fc′, regardless of the curing conditions. The modified equations show promise for reliably assessing both the compressive strength gain rates at different ages and the stress–strain behavior of high-early-strength portland cement mortars containing limestone powders.

Effect of shell composition on watertightness and mechanical performance of cement-based capsules used as self-healing additives of cement

The aim of this work is the development of cementitious macro-capsules for self-healing cement and concrete materials. Emphasis is placed on shell properties, including size, thickness, strength, and volume to active component ratio. This enhancement is aimed at protecting the healing agent and ensuring adequate reactivity upon crack formation, surpassing survivability considerations. To this direction, core/shell particles have been produced following the pan-coating method, while different types and concentrations of setting acceleration solutions for the shell stabilization were studied. The formation of core-shell capsules encompasses the formation a spherical core through agglomeration, followed by simultaneous spraying of cement powder and a setting acceleration solution for the shell formation, under continuous rotation. The microstructural characteristics of the shell were studied through scanning electron microscopy (SEM), while the reactivity of the protected core (reactive agent) inside the hardened mortar mixtures was evaluated using thermogravimetric analysis (TGA). Moreover, the crushing load of the capsules under compression and their survivability during mixing process were examined and interpreted in relation to their diameter, circularity, and shell thickness.The results revealed the ability of the encapsulation methodology proposed to tailor the shell properties and modify the capsule properties so as satisfy the requirements of different applications. The use of setting accelerators during shell formation proved essential for enhancing the density and the strength of the shell layer. As a consequence, this leads to macro-scale capsules with elevated survivability rate and core reactivity.

Influence of ground slag and dune sand behavior of binary and ternary cement

This study examines the effect of slag and dune sand replacement (binary and ternary) in cement production, focusing on key mechanical properties and chemical behavior, especially on fire loss and residual an insoluble examined at different curing times ranging from 2 to 210 days. The findings show that the addition of slag and dune sand powder significantly influences the mechanical and thermal properties of mortar mixtures replaced by slag the compressive strength increases up to 30% and a slight decrease up to 40 is observed %. Ternary mixes show improved long-term compressive strength, especially after 120, 210 days, although generally young strength is lower than control When binary and ternary are combined with high flexural strength, ternary mixes exhibit good long-term performance, especially in mixtures of 20-30% slag and 10% dune sand lime (ACHOURA, D and al. 2008). From a thermal perspective, the replacement of slag with dune sand lime reduces losses during combustion, indicating excellent thermal stability. The addition of dune sand lime increases the proportion of impervious residue, indicating stability and durability of the cement. Overall, the study concludes that the proper use of slag and dune sand lime especially in ternary mixes can significantly improve the long-term mechanical and thermal performance of cement mortars Thus these findings provide valuable insights for designing building materials with higher durability and strength to suit specific construction application applications.

РОЛЬ САСО3 У ФОРМУВАННІ МІЦНІСНИХ І ДЕКОРАТИВНИХ ВЛАСТИВОСТЕЙ ПОРОШКОВОГО ЛУЖНО-АКТИВОВАНОГО ШЛАКОПОРТЛАНДЦЕМЕНТНОГО БЕТОНУ

The article discusses approaches to the formation of compositions of alkali-activated decorative Portland slag cements containing Portland cement type CEM1 5...45% with high performance and decorative properties. The optimization of the compositions of decorative alkali-activated Portland slag cements was carried out using statistical methods for designing experiments. Finely dispersed TiO2 and CaCO3 additives with a whiteness of 90% were used as bleaching components. The alkaline component is sodium metasilicate in the form of a non-hygroscopic powder. The research carried out made it possible to obtain decorative Portland slag cements with a whiteness of 45...77%, which allows them to be used to produce colored cements with a wide range of colors from white to black. It has been established that alkali-active decorative Portland slag cements have an activity of 37...59 MPa at the age of 28 days. All compositions have good hardening dynamics and, based on the strength at the age of 2 days  22...36.6 MPa, they can be classified as fast-hardening. Based on them, it is possible to produce dry construction mixtures. All mortar compositions based on alkali-active decorative Portland slag cements demonstrate fairly high frost resistance  F200. This allows them to be used for the manufacture of products and solutions both for indoor use and when exposed to atmospheric influences without loss of design characteristics and decorative appeal. The inherent shrinkage strains of decorative alkali-activated Portland slag cements are 0.51...0.61 mm/m, which eliminates cracking and premature destruction of products. The use of the CaCO3 additive is especially effective for controlling the shrinkage deformations. Thus, the CaCO3 additive performs the functions of not only a decorative component, but also a structure-forming component. Concrete and mortar mixtures can be used to produce decorative products using the traditional method, extrusion, 3D printing on construction printers, etc. And not too long setting times and a rapid increase in strength make it possible to produce products without thermal treatment or with minimal consumption of thermal energy.

Salt weathering resilience in masonry: An accelerated laboratory study involving wind-induced variations

Salt weathering resistance is a critical parameter governing the durability of coastal masonry units and mortars. Accelerated weathering cycles are employed at the laboratory to investigate the responses of substrates and mortars upon exposure to salt, moisture, temperature fluctuations and humidity. In this paper, the individual and synergistic performances of bricks and mortar formulations when exposed to accelerated salt weathering cycles are investigated, incorporating the influence of wind on their resilience. The study examines the behaviour of brick-mortar sandwich specimens and separate specimens of bricks and mortar mixtures comprising cement, dry hydrated lime, fly ash, and limestone. These specimens are exposed to repeated weathering cycles in a 5 % sodium sulphate solution. Along with the mass variations during each weathering cycle, physicomechanical, microstructural, mineralogical and morphological characterization of the specimens are used to compare their salt weathering resistance. The results highlight that the responses of individual masonry components might not collectively translate to the overall performance of the combined system due to hygric resistance, which is minimal when the components have comparable pore size distribution. Higher microporosity (pores of diameter between 0.1 μm and 10 μm) and mechanical strength enough to resist the crystallization stresses together provide better resistance to salt weathering to the individual mortars. However, pore structure compatibility and pore fraction similarity between the components govern the behaviour of the combined system and, therefore, reflect the better performance of sandwich specimens with brick and lime mortars. The study demonstrated that wind accelerates material degradation during salt weathering through progressive erosion, accelerated evaporation and subsequent formation of isolated thenardite.

Rapid Assessment of Sulfate Resistance in Mortar and Concrete.

Extensive research has been conducted on the sulfate attack of concrete structures; however, the need to adopt the use of more sustainable materials is driving a need for a quicker test method to assess sulfate resistance. This work presents accelerated methods that can reduce the time required for assessing the sulfate resistance of mixtures by 70%. Class F fly ash has historically been used in concrete mixtures to improve sulfate resistance. However, environmental considerations and the evolving energy industry have decreased its availability, requiring the identification of economically viable and environmentally friendly alternatives to fly ash. Another challenge in addressing sulfate attack durability issues in concrete is that the standard sulfate attack test (ASTM C1012) is time-consuming and designed for only standard mortars (not concrete mixtures). To expedite the testing process, accelerated testing methods for both mortar and concrete mixtures were adopted from previous work to further the development of the accelerated tests and to assess the feasibility of testing the sulfate resistance of mortar and concrete mixtures rapidly. This study also established criteria for interpreting sulfate resistance for each of the test methods used in this work. A total of 14 mortar mixtures and four concrete mixtures using two types of Portland cement (Type I and Type I/II) and various supplementary cementitious materials (SCMs) were evaluated in this study. The accelerated testing methods significantly reduced the evaluation time from 12 months to 21 days for mortar mixtures and from 6 months to 56 days for concrete mixtures. The proposed interpretation method for mortar accelerated test results showed acceptable consistency with the ACI 318-19 interpretations for ASTM C1012 results. The interpretation methods proposed for the two concrete sulfate attack tests demonstrated excellent consistency with the ASTM C1012 results from mortar mixtures with the same cementitious materials combinations. Metakaolin was shown to improve sulfate resistance for both mortar and concrete mixtures, while silica fume and natural pozzolan had a limited impact. Using 15% metakaolin in mortar or concrete mixtures with Type I/II cement provided the best sulfate resistance.

Effect of PCE anionic charge density on fly ash cementitious system-PCE compatibility

In this study, the compatibility of polycarboxylate-based water-reducing admixtures (PCEs) with cementitious systems containing fly ash (FA) was investigated. For this purpose, PCEs with carboxylate, phosphate, and sulfonate anionic groups having different anionic charge densities were synthesized. The effects of PCEs on fresh properties and compressive strength of cementitious systems containing FA were investigated. The PCE with 9% phosphate substitution and high anionic charge density was found to be the most effective, requiring the least amount for the target flow. Similarly, in terms of the PCE requirement for the minimum Marsh funnel flow time and rheological parameters, the best performance was obtained with 5% sulfonate substituted PCE having high anionic charge density. While FA had a positive effect on the PCE requirement and consistency retention of the mixtures; it had a negative effect on Marsh funnel flow time, rheological properties, and compressive strength. However, the rheological properties of the mortar mixtures were not adversely affected by the FA substitution as much as that of the paste mixtures. Regarding the 28-day compressive strength of mortar mixtures, the optimum FA substitution ratio was 15%. Fly ash substitution above this level reduced the compressive strength at all ages including 28-day strength. Anionic charge density variation of PCE had no significant influence on the compressive strength of the mortars.

Hydrothermal and mechanical performance of mortars containing waste brick powder

It is widely recognised that green building, environmental sustainability, and technical performance have recently become requirements in the field of civil engineering. For this reason, the new trend in research is to focus on the recycling and recovery of materials, even if some of them such as industrial waste are still underexplored. In this perspective, the main objective of this work is to study the influence of brick powder on the thermophysical and mechanical properties of mortars containing this type of waste, in different environments, and within the temperature range between ambient temperature and 50 °C. To this end, a number of mortar mixtures, in which cement was replaced by brick powder in different proportions, were studied and characterised according to technical standards in order to define the optimal substitution percentage. Three batches of samples were examined at different ages, i.e., 3, 7, 28, and 90 days. The samples of the first batch were kept in water at a temperature of 20 ± 2 °C with a relative humidity RH = 100 %, while those of the second batch were immersed and stored in water at 50 °C in order to simulate a hot and humid climate. As for the samples of the third batch, they were kept in a dry oven at 50 °C in order to investigate the effect of the hot and dry climate. The results obtained revealed that the partial replacement of cement by brick powder makes it possible to improve the thermal insulation characteristics but reduce the mechanical strength of the mortar. In addition, it was shown that in a hot and dry environment, the mechanical characteristics of the different mortars decrease as the rate of weight substitution of cement by brick powder rises. However, in a hot and humid environment, a reverse trend is observed. The findings also suggested that the optimal recommended rate of substitution of cement by brick powder is 20 %.

Mixture of biochar as a green additive in cement-based materials for carbon dioxide sequestration

Cement production for concrete is one of the main reasons why the building industry contributes significantly to carbon dioxide emissions. This paper investigates an innovative approach to utilizing CO2 by incorporating mixed biochar in mortar. Various dosages (0%, 3%, 5%, and 10%) of mixed biochar were explored to assess their impact on the structural properties and environmental sustainability. In this study, mixed biochar was prepared using the pyrolysis method, in which biomasses (rice husk and sawdust) were heated in the absence of oxygen for 2 h in a muffle furnace at the heating rate of 10 ℃/min to 550 ℃ with a 2-h holding time. The replacement of biochar was done with cement in a mortar mixture for casting the cubes followed by putting them in the carbonation chamber for 28 days curing. After that, the cured samples were tested for mechanical strength, porosity, density, and water absorption. X-ray diffraction (XRD) and thermo-gravimetric analysis (TGA) showed that biochar supplementation promoted cement hydration products. Field emission scanning electron microscope (FESEM) analysis showed that several cement hydrates such as C-S–H, Ca(OH)2, and CaCO3 were formed with different doses of biochar and increased mechanical strength. Addition of 10 wt. % biochar increased the compressive strength of the composite by 24.2% than the control respectively, and successfully promoted the CO2 sequestration with 6% CO2 uptake after 28 days of accelerated CO2 curing. The present research has shown the benefits of optimally integrating mixed biochar with cement in the development of low-carbon, sustainable cementitious materials that have the potential to convert building materials like concrete in the future.

Life-Cycle Assessment and Environmental Costs of Cement-Based Materials Manufactured with Mixed Recycled Aggregate and Biomass Ash.

The development of new building elements, such as concrete and mortar with sustainable materials, which produce a lower carbon footprint, is an achievable milestone in the short term. The need to reduce the environmental impact of the production of cement-based materials is of vital importance. This work focuses on the evaluation of the life-cycle assessment, production costs, mechanical performance, and durability of three mortars and three concrete mixtures in which mixed recycled aggregates (MRAs) and biomass bottom ash from olive waste (oBBA) were included to replace cement and aggregates. Powdered MRA and oBBA were also applied as complementary cementitious materials with a reduced environmental footprint. Chemical and physical tests were performed on the materials, and mechanical performance properties, life-cycle assessment, and life-cycle cost analysis were applied to demonstrate the technical and environmental benefits of using these materials in mortar and concrete mixtures. This research showed that the application of MRA and oBBA produced a small reduction in mechanical strength but a significant benefit in terms of life-cycle population and environmental costs. The results demonstrated that finding long-term mechanical strength decreases between 2.7% and 14% for mortar mixes and between 1.7% and 10.4% for concrete mixes. Although there were small reductions in mechanical performance, the savings in environmental and monetary terms make the feasibility of manufacturing these cement-based materials feasible and interesting for both society and the business world. CO2 emissions are reduced by 25% for mortar mixes and 12% for concrete mixes with recycled materials, and it is possible to reduce the cost per cubic meter of mortar production by 20%, and the savings in the cost of production of a cubic meter of concrete is 13.8%.

Characterization of Phosphogypsum for Potential Uses in Soil Stabilization

This research investigated the influence of phosphogypsum (PG) addition to mortar mixture and determined the possibility of utilizing PG in soil stabilization. Originally, the chemical composition and mineralogy of the PG were determined using X-ray fluorescence (XRF) and X-ray diffraction (XRD) tests. The principal constituent of PG becomes calcium sulfate hemihydrate with the presence of some impurities. A total of 9 mixes have been developed: A plain mortar mix is a comparative base, and the other 4 mixes are with 5, 10, 15, and 20 % cement replacement with PG for each type (fresh and stockpiled PG called PGF and PGS, respectively). The experimental program focuses on analyzing the effects of PG on setting time, hardened density, compressive strength, and water expansion of mortar mixtures before its soil stabilization application. Test results indicate that with higher PG, the setting time of the mortar mix is delayed except for the mixture with 20% PG, which experienced an early false set. The results of the compressive strength tests revealed that the 5% PG mixes exhibited higher values compared to the control mix, starting from the 28-day curing period, regardless of PG type. Although the higher PG content and compressive strength lowered, the expansion levels were very low based on the ASTM C 1260 limits for all mixtures, excluding heaving risks.

High-temperature resistance of ceramic sanitaryware waste and fly ash-based geopolymer and hybrid geopolymer mortars produced at ambient curing conditions

In this study, five different hybrid geopolymer mortar mixtures were prepared, incorporating two different geopolymers and low percentages of Portland cement (PC), (16.6 % and 33.3 %). In geopolymer mixtures, 100 % ceramic sanitaryware waste (SW) and 100 % fly ash (FA) were used as precursor materials. In hybrid mixtures, the precursor materials include FA+ PC, SW+PC, and FA+SW+PC. The flexural and compressive strengths of mortars were determined up to 56 days to investigate their strength development. Additionally, the mortars were exposed to elevated temperatures up to 800 °C, separately. After the high-temperature exposure, phase (XRD) and microstructure (SEM/EDS) analyses were conducted on the selected mortars. All the hybrid geopolymers had higher flexural and compressive strengths than the geopolymers for all the curing ages. The highest 28-day flexural and compressive strength values of 5.3 MPa and 37.0 MPa were obtained on the mixture where FA+SW+PC precursors were used in equal amounts, respectively. The geopolymer and hybrid geopolymer mortars (containing 16.6 % PC) performed well under the high-temperature effect up to 800ºC. The strength values of all the mortars were obtained higher at 800ºC than at 600ºC. After high-temperature exposure, additional crystalline phases such as gehlenite were detected in hybrid mortars.

Experimental Study on the Effects of Tapioca Starch on Cement Mortar Quality Improvement.

In this study, the effect of tapioca starch (TP) on mortar was evaluated by incorporating TP into the mortar mixture. The evaluation involved analyzing the mortar's quality characteristics, performance, and fundamental quality improvements. The addition of TP resulted in a decrease in flow, which was attributed to increased viscosity. Specifically, a 10% reduction in flow was observed with a 0.025% increase in TP content. After 28 days, the impact of TP on the compressive strength of the mortar remained consistent, regardless of the TP amount. However, within the first 3 days, higher TP content accelerated strength development, with early compressive strength increasing by up to 20% at a 0.050% TP level. Additionally, bond strength improved by approximately 60% at a 0.050% TP concentration, and final shrinkage was reduced by 5%.

Silica Quartz Characteristics from Local Silica Sand on Compressive Strength of Mortar

Many minerals, including quartz sand, granite, and feldspar, contain silica (SiO2), a substance that performs the same function as quartz. Silicate (SiO2), the primary mineral found in silica sand, can be added to concrete mixtures to boost strength. This means that silica sand can be employed as a cementitious component in concrete because it is believed to have pozzolanic and amorphous qualities. This study is part of a series that tries to use silica sand from an area in Indonesia. The purpose of this research was to manufacture and describe quartz silica (QS) from Kolaka silica sand, which was acquired from Southeast Sulawesi province in eastern Indonesia. In order to improve the characteristics of mortar mixtures that use composite Portland cement as a binder, it is advised to combine the X-ray diffraction process with an evaluation of the impact of addition (QS) on their physical and mechanical properties (volume weight and compressive strength). Laboratory experimentation is being conducted here. Water, cement, and silica sand are used to make mortar specimens. Red and white silica sand is the type of silica utilized. The specimens were created with a 50 mm diameter and a 100 mm height. Tests on mortar's compressive strength were performed after 7, 14, and 28 days. The study's findings indicated that the amounts of quartz formed in red and white silica sand were 45.05% and 91.87%, respectively. The volume weight that results is approximately 2.78 gr/cm3. Red silica sand was tested for compressive strength at ages 7, 14, and 28 days, and the findings were 20.73, 23.32, and 24.61 MPa, respectively. White silica sand has compressive strengths of 21.83, 24.67, and 26.52 MPa. We are aware of no prior studies examining the use of crystalline silica from Kolaka silica sand to enhance the mechanical qualities of cement mortar. Doi: 10.28991/CEJ-2024-010-08-010 Full Text: PDF

Multi-scale study of the effect of superabsorbent polymers on microporosity, dimensional stability, and durability of cementitious materials

As internal curing agents, superabsorbent polymers (SAPs) help enhance the degree of hydration of cement particles. In the meantime, however, they affect the dimensional stability and durability of the mixtures that benefit from them. This critical aspect, which is influenced by the type, size, and dosage of SAPs, motivated the current study. To obtain holistic assessments and side-by-side comparisons, six high-performance mortar mixtures were developed based on a control mixture. The referenced mixtures contained two types, two sizes, and two dosages of SAPs. Initially, the performance characteristics of the SAP powders were determined, in terms of water absorption and desorption. Autogenous shrinkage tests were then performed to evaluate how SAPs contribute to controlling this type of shrinkage over time. The microstructures of the developed mixtures were then analyzed using mercury intrusion porosimetry, paired with scanning electron microscope images, providing fundamental insights into to the role of SAPs in both short and long terms. To correlate the findings to the mechanical properties of the developed mixtures, a set of compressive strength and abrasion resistance tests were performed. The results were then complemented with the data obtained from the rapid chloride migration tests. This study’s outcome showed that SAP particles can effectively reduce the development of autogenous shrinkage-induced strains. Additionally, the inclusion of SAPs was found to alter microstructural characteristics, increasing the density of the binding gel, while introducing capillary pores. This was confirmed through enhanced abrasion resistance and reduced chloride resistivity.

Characterization of washing aggregate sludge waste as a novel supplementary cementitious material: Experimental study and life cycle assessment

Washing aggregate sludge (WAS), a waste collected from aggregate quarries, is examined for its application as a partial substitute of ordinary portland cement (OPC). The raw WAS initially dried, ground, and then subjected to 700 °C and 900 °C. In this study, various paste and mortar mixtures were produced to investigate the pozzolanic property and environmental impacts of raw WAS and treated WAS at a selected temperature of 700 °C. The pozzolanic activity of both raw and treated WAS at 700 °C was verified using several tests, including X-ray diffraction (XRD), Frattini test, strength-based evaluation, and thermal analysis. The calcium-silicate-hydrate (C–S–H), portlandite (Ca(OH)2), calcium silicates (C2S and C3S), and calcite (CaCO3) were identified as major reaction products indicating the participation of raw or treated WAS. While the reduced [CaO] concentration and location below the solubility curve confirmed the pozzolanic activity of both powders, the compressive strengths of blended mortars were also found greater than 75% compared to the reference mortar at all testing ages. Treated WAS demonstrated higher pozzolanic activity than raw WAS due to the reduced formation of Ca(OH)2 revealed by thermal and kinetic analysis at different time periods. Life cycle assessment resulted in the reduced CO2 emissions by the blended mortars containing either raw or treated WAS, which suggest their promising mechanical and environmental benefits.

Experimenting the effectiveness of waste materials in improving the compressive strength of plastic-based mortar

The reduction in compressive strength (CS) of cementitious composites incorporating waste plastic is the main concern limiting its applicability in the building sector. Using industrial wastes as cement substitutes to enhance the CS of plastic mortar is a sustainable approach. This study used fine powdered waste materials such as silica fume (SF), marble powder (MP), and glass powder (GP) in plastic-based mortar for their effectiveness in enhancing CS. Plastic mortar specimens were cast using plastic waste in 5–25 % contents as sand replacement by mass, and their 28-day CS was recorded as a reference. SF, GP, and MP were utilized in plastic mortar mixtures separately in proportions of 5–25 %, with a 5 % increment, substituting cement by mass. These waste powders were also used in combinations of two (SF+GP, SF+MP, and GP+MP) and three (SF+GP+MP) in plastic mortar mixtures. Moreover, prediction models were built using the experimental database for the CS of plastic mortar. Gradient boosting and bagging ensemble machine learning (ML) techniques were chosen for model development. The decrease in CS was limited by substituting SF, GP, and MP for cement in plastic mortar. It was determined that the most effective substitution levels for SF, GP, and MP in plastic mortar, according to the strength enhancement, were 15, 10, and 15 wt.% of cement, respectively. The ML models closely matched experimental results, and in terms of R2 and error evaluations, bagging model outputs were more accurate than gradient boosting. The gradient boosting and bagging models had R2 of 0.89 and 0.94, respectively, with average absolute errors of 0.87 and 0.65 MPa.