Portland Cement Type Research Articles

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.

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.

To Evaluate the Degradation of Heat Damaged Concrete Specimens after Curing Using Non-Linear Ultrasound Technique

In this research, Non-linear Ultrasound (NLU) technique was used to evaluate the degradation on heat damaged cement mortar specimen behaving explicit nonlinear. Mortars of Portland cement type I (or normal cement, NC) were chosen to mold the specimens with water cement ratios of 0.4, 0.5 and 0.6, and size of 5x5x5cm-cube and 5x5x2cm-brick. The specimens were grouped for heating at different temperatures (30, 200, 300, 400, 600, 800℃ for 24 hours) to create degradations of different levels. After curing process in water for 28 days, mechanical property tests were carried out on each cube to get its stress-strain relation and strength. NLU tests were conducted on the brick specimens. The RITEC SNAP System with 250kHz/transmit and 500kHz/receive transducers was used to conduct the measurement of harmonics. The obtained amplitudes in spectrum of fundamental, 2nd and 3rd harmonics (A1, A2 and A3) and the amplitudes due to the background nonlinearity by facility (A01, A02 and A03) were analyzed to approach the nonlinear parameters for each specimen, such as the β and γ. The [(A01- A1),(A03/A 3 2 01 -A3/A13)] and[(A01-A1), |A02/A01 -A2/A12|] were applied as a nonlinear characteristic index to mark the quality of the microstructure of material, which could be related to the durability and workability of the material. The results showed a promised quantification method using NLU. Extended application can be expected.

Assessment of Durability of Chemically Stabilized Soils Using Different Moisture-Susceptible Methods

The durability of chemically treated subgrade soils is important for pavement design life, and it is a major concern for transportation and defense agencies. Stabilized soil layers should retain strength and stiffness properties under wetting–drying-related durability cycles and moisture exposure. Many durability test methods, including wetting and drying, tube suction, and Engineer Research and Development Center’s wet-test methods, have been developed and used in several stabilization studies in the past. It is important to study and determine how these methods address the long-term performance of chemically stabilized soils with a focus on stabilizer permanency. Therefore, this research study conducted a comprehensive laboratory investigation using all three methods to assess the durability of stabilized soils as per the US Department of Defense protocols. Three types of soils, silty sand, clayey sand, and high-plasticity clay, and three types of stabilizers, vinyl acetate-ethylene (VAE) copolymer, Portland cement type I, and hydrated lime, were considered in this study. Silty sand, clayey sand, and high-plasticity clay soils were treated with VAE copolymer, cement, and lime, respectively. Results of cement-stabilized soil showed that it is unsusceptible to moisture fluctuations, whereas VAE-stabilized soil indicated its higher susceptibility to moisture variations. Both the ASTM wet–dry (W-D) test and tube suction test methods revealed that lime-treated clayey soil is moisture-susceptible. All three methods showed similar findings, with good agreement existing between tube suction and ASTM W-D tests for all combinations of soils and stabilizers considered in this study.

Harmonizing smart technologies with building resilience and sustainable built environment systems

Given the escalating concerns posed by climate change-related disasters, there is an urgent need for a more sustainable and resilient built environment. The developing digital revolution in recent years has the potential to harness its superior features to achieve sustainable and resilient building sector goals. This paper aims to present a futuristic perspective on the three basic pillars of a more sustainable and resilient built environment. These pillars comprise sustainability, resilience, and the utilization of Artificial Intelligence (AI) for monitoring and managing structural health and performance. This is evident in the context of smart buildings and their ability to enhance energy consumption efficiency, improve quality of life, and strengthen structural health monitoring in terms of reducing damage and facilitating timely maintenance operations. Through comparing the components of the virtual city designed from two types of alkali-activated binder concrete (AABC) and ordinary Portland cement (OPC) concrete, all components of the city designed from AABC showed a reduction in the amount of emitted CO2. The highest decrease was observed in the schools designed from AABC, where the reduction was about 25 %, while the lowest decrease was for the villas and infrastructure; about 11 % and 10 % respectively, compared to those designed from OPC concrete. The results also indicated that the utilization of sustainable concrete instead of traditional varieties has the potential to decrease CO2 emissions by up to 25 %. The importance of this work resides in establishing a basis for forthcoming research that combines intelligent, environmentally friendly, and resilient building practices.

The influence of crystalline technology as concrete admixture on compressive strength and permeability

In regions prone to frequent rainfall or coastal exposure, concrete gradually becomes porous due to environmental influences. This study systematically examines the impact of different concrete formulations on compressive strength and permeability. It evaluates standard concrete, concrete with 1% and 2% crystalline admixtures, and concrete utilizing Portland cement type V. Compressive strength tests reveal that concrete with 1% and 2% crystalline admixtures, alongside Portland cement type V concrete, exhibit superior quality compared to standard concrete. Permeability assessments unveil intriguing trends: Portland cement type V concrete displays heightened permeability relative to standard concrete, while 1% and 2% crystalline admixture concretes exhibit significantly reduced permeability, surpassing both standard concrete and Portland cement type V concrete. The heightened concrete density associated with crystalline admixtures can be attributed to their dual influence on augmenting compressive strength and decreasing permeability. By reinforcing these mechanisms, crystalline admixtures effectively enhance concrete durability. This research contributes to the understanding of advanced construction materials and offers insights into sustainable infrastructure development possibilities. Subsequent sections delve into experimental intricacies, result explications, and wider implications of these findings, shaping the trajectory of future construction practices.

Performance of a novel structural insulated panel in tropical climates: Experimental and numerical studies

This article investigates experimentally and numerically the thermal performance of a new type of structural insulated panel (SIP) termed ‘UWall’. The panel core consists of an ad-hoc waffle skeleton of Expanded Polystyrene (EPS), EPS beads mixed with cement mortar (Portland cement type I and recycled concrete aggregate), and two external water-proof cement boards. The experimental programme examined the panels in three Phases. In Phase 1, 200×200×100 mm block specimens were exposed to a temperature of 70°C for 12 hrs. It was found that the new UWall specimens had a better thermal performance (by up to 20%) over other types of walls typically used in house construction in Southeast Asia such as Mon block wall. In Phase 2, five scaled-down house units (1.5×1.5×2.8 m) were built in Thailand. Temperature and relative humidity outside/inside the units were continuously monitored for 7 days during the summer season. It was found that the new UWall has a good thermal resistance, reducing temperatures by up to 4°C compared to mon-block wall material. The house units were subsequently modelled in Abaqus® software, and the modelling approach proved accurate (within 10%) at simulating the thermal performance of the house units. UWall panels were also tested in bending to determine their structural capacity. It was found that the panels can be safely used as load-bearing walls for single-storey houses. Design charts are then proposed and used to design and build a full-scale house in Phase 3. In Phase 3, a 10×7 m full-scale single-storey house was built using the new UWall panels. Based on results from bioclimatic charts, it was found that daytime temperature and humidity in the full-scale house were deemed as uncomfortable. However, if air movement was provided, the house remained within the comfortable zone at all times. New design charts for full-scale houses with UWall are proposed to meet a desired user-comfort level. This study is expected to promote the use of SIPs in house construction in tropical climates, which in turn is envisaged to save energy and make construction more sustainable.

Strength development and self-desiccation of saline cemented paste backfill.

Given that many mines around the world are located in areas where fresh water is scarce, and companies are being held to increasingly stringent sustainability and environmental responsibility standards, many mines are looking to use locally available saline groundwater or seawater as mixing water in cemented paste backfill (CPB). However, the impacts of this decision on key engineering properties of CPB (e.g. strength and self-desiccation) that affect its mechanical stability need to be better understood to allow confident selection of this practical and more sustainable solution. Thus, the effect of mixing water salinity and binder type on the strength (unconfined compressive strength, UCS) development and self-desiccation (measured by suction and volumetric water content) of CPB is explored in this research. NaCl concentrations from 0 to 300g/L were used in CPB made with silica tailings and Portland cement type I (PC). Concentrations of 10 and 35g/L were found to moderately increase UCS, while a concentration of 100g/L had comparable UCS to non-saline CPB and a concentration of 300g/L was found to significantly decrease UCS over all curing times. The overall trend is 10g/L > 35g/L > 0g/L > 100g/L > 300g/L. The UCS of the 60-day-old CPB with a NaCl of 300g/L is significantly lower, registering a 26% decrease compared to the UCS of the 60-day-old CPB without salt. In contrast, the UCS of the 60-day-old CPBs containing 10g/L and 35g/L of salt exhibits a notable improvement, being 15% and 10% higher, respectively, than the UCS of the 60-day-old CPB without salt. Water content and suction monitoring were conducted up to 28days of curing time, and it was found that suction only slightly contributed to UCS gain of the saline CPB, and high salt contents (100 and 300g/L) significantly inhibited the self-desiccation ability of CPB due to inhibition of cement hydration by the excessive amount of salt. The increase in strength of both saline and non-saline samples was attributed primarily to the increase in cement hydration products, while the increased strength of the samples with salinities of 10 and 35g/L was mainly attributed to the enhancement of the binder hydration due to the low amount of salt and the presence of Friedel's salt in the pores. The effect of PC replacement by 25 to 75% with slag on CPB with 35g/L mixing water salinity was also studied. Slag replacement of 50% and higher resulted in significantly higher UCS over most curing times. Suction likely moderately contributed to UCS of the saline CPB with slag, in addition to the presence of Friedel's salt in the pores and the acceleration of cement and slag hydration by the presence of NaCl.

Resistance of Chloride and Sulfate of Geopolymer based on fly ash and silica fume as alternative raw materials.

Concrete durability to salt resistance is the main factor affecting the service life of concrete used in acid or salt environment. This project aims to develop the concrete composition for salt resistance of chloride and sulfate at 50,000 mg/L as the simulated salt solution in this project. Geopolymer consisted of 10%wt ordinary Portland cement (OPC type 1) with the other alternative raw materials which were pozzolanic materials and wastes (fly ash, silica fume and rice husk ash). The various parameters which were type and content of the alternative raw materials, plasticizers content, liquid to powder ratio, etc, were studied for developing the compressive strength of geopolymer after soaking in the simulated salt solution for 14 days as comparison with those in the normal water and the ordinary Portland cement. The results found that geopolymer consisted of fly ash and silica fume with the mixture of NaOH (10M): Na2SiO3 in a ratio of 24:16 (wt./wt.) could improve the compressive strength of geopolymer cement after soaking in the simulated sulfate salt solution for 14 days as compared to the ordinary Portland cement type 1 and type 5. Moreover, this geopolymer showed low density which was beneficial for use in the engineering structure in the high salt area. In addition, the change of chemical reaction and phases after setting of geopolymer in high concentrations of chloride and sulfate solution were studied to understand the mechanism of salt resistance of geopolymer and to develop the concrete composition for salt resistance in the future.

The Flue Gas Desulfurization Gypsum Applications in Production of Eco-Friendly Cementitious Matrices

Portland cement is one of the most manufactured materials in the world. The worldwide cement industry accounts for at least 5-8% of the anthropogenic CO2 emissions and therefore is an important sector for CO2-emission mitigation strategies to limit global warming. One of the strategies for reducing the carbon footprint of the cement industry is replace traditional Portland cement with other solid wastes. In the present study, the influence of the application of flue gas desulfurization gypsum (FGD gypsum) generated from coal-fired power plant in construction mortar was investigated. Cylindrical specimens were molded with Portland cement type CPII-F 32, sand and 0%, 25%, 50% and 75% amounts of FGD gypsum. After curing time of 1, 3, 7, 28 and 91 days, the cementitious materials were characterized mechanically by axial compressive strength, setting time and slump. The pastes in the age of 28 days were further characterized by X-ray diffraction with Rietveld analysis. Results showed that FGD gypsum can be used as a substitute for cement as a setting retarder in an amount of up to 25%, and as an accelerator in an amount of 75%, being necessary dosage of the specific traces of the materials depending on the purpose of its use.

Study of fresh properties of cemented paste backfill material with ternary cement blends

This study is aimed at evaluating the effects of ternary blended Portland cement type I (PCI) with slag and limestone (LS) powder on key engineering fresh properties of CPB: (i) rheological properties and (ii) setting time. CPB samples with PCI/Slag ratios of 50/50 (Group A) and 80/20 (Group B) were considered in this study. The effect of LS in the ternary mix was investigated by replacing the slag with increasing doses of LS (5, 10, and 20 wt%). The specimens were cast and cured over periods of 0, 0.25, 1, 2 and 4 h and tested for rheological properties (yield stress, viscosity). In addition, tests were performed to identify the initial and final setting time of the samples. In addition, microstructural tests, zeta potential and pH measurements, and monitoring experiments (temperature, electrical conductivity) were carried out to better comprehend the underlying mechanisms behind the observed changes in rheological behavior and setting time. The findings have shown that the replacement of slag by a higher dosage of LS in the ternary binder significantly affects the rheological properties of the studied CPB. It reduces the yield stress and increases the viscosity of CPB. The effect of LS on the rheological properties of CPB is mainly attributed to the physical (e.g., filler effect, lubrication, particle size) and chemical (nucleation and changes in repulsive forces between CPB particles) effects of LS in the ternary system. The findings also revealed that increasing the proportion of limestone in the CPB ternary binder system prolonged the setting time (initial and final) of the CPB mixture due to the nucleation and dilution effects of LS. Overall, the synergy between slag and LS was observed; the optimal use of LS and slag in the ternary system can serve as a sustainable alternative to the predominantly used ordinary Portland cement (OPC) or OPC/Slag binary binder, thereby reducing the energy consumption and carbon footprint associated with cement and CPB technology. The results of this research will be valuable for a better comprehension of the impacts of ternary binder with an increasing percentage of LS on the rheology and setting time of the CPB mix, ultimately, the efficient design of the mixing plant, especially the backfill transportation system.

Theoretical modeling on the temperature-dependent dielectric properties of concrete pavement materials

The variations of concrete pavement temperature will affect the dielectric properties of concrete, which have a substantial influence on the wireless power transfer efficiency of concrete electrified road and non-destructive accuracy of ground-penetrating radar (GPR). In order to elucidate and describe the variations in the dielectric properties of concrete with temperature, the dielectric properties of aggregates (limestone), six types of cement mortar (matrix) and concrete (two types of Portland Cement: P.O 32.5 and P.O 42.5; three W/C ratios: 0.4, 0.5 and 0.6) within the temperature of −30 ℃ to 60 ℃ were acquired via a network analyzer platform and an open-ended coaxial probe kit. The results show that the dielectric constants of limestone, cement mortar and concrete increase with varying degrees when temperature rises. Furthermore, strong linear agreement between the dielectric constants of limestone, cement mortar and concrete and temperature is identified, indicating that the variations in the dielectric properties of concrete with temperature should be taken into consideration. Meanwhile, a temperature-dependent dielectric model of concrete is established by introducing the dielectric-temperature coefficients so as to quantify the influence of temperature on the dielectric properties of concrete. Compared with the traditional models (Brown model, CRIM model, Looyenga model, and Rayleigh model), the proposed model has the highest precision and is less sensitive to temperature variations. Therefore, the proposed model is more suitable for predicting the dielectric properties of concrete at different temperatures, which is essential for the development of future electrified road and promoting non-destructive accuracy of GPR equipment.

Hy_Surf model: Viscoelastic evolution in Portland cement suspensions during the early-age hardening

The hardening of cementitious suspensions at early stages of hydration is determined by the kinetics of the binder, which can be characterized by measuring the viscoelastic changes in the elastic storage modulus (G′) using oscillatory rheometry. This study aims to propose a new model that takes into account the physical-colloidal properties of suspensions and the transformations caused by hydration reactions, particularly the changes in the specific surface area of the particles. The model considers three mechanisms that influence viscoelastic evolution: agglomeration, bridging between particles after hydrate growth, and cohesion generated by attractive forces between C-S-H hydrates. The model, named Hy_Surf, was found to be highly correlated with experimental results, demonstrating its ability to accurately describe the mechanisms involved in the evolution of G′ during the first 4 h of hydration for various types of Portland cement, even when one of them had been prehydrated.

An Experimental Study on Compressive Strength of the Concrete Containing Type II Cement and Tire-Rubber Particles at Various Ages

Abstract Compressive strength of concrete is one of the most important properties of concrete for designers and quality control engineers and the engineering community is interested in predicting 28-day compressive strength of concrete because of the strength of concrete at younger ages such as 7 days. Portland cement type II is one of the most widely used cements, which has the highest consumption because of the weather conditions and the construction process of structures in Iran. The relation for computing the compressive strength at the age of t based on the 28-day strength has been presented only for cement types I and III and there is no relation for type II cement in ACI codes of practice. In this study, the compressive strength of concrete at the age of t based on the 28-day strength has been experimentally investigated for the concretes containing cement type II and tire rubber particles. To this end, three cement grades of 350, 400, and 450 kg/m3 as well as water-to-cement ratios (w/c) of 0.5 and 0.65 were used. Moreover, cement was replaced with tire-rubber particles at contents of 5 to 20 % by volume. The values for α and β coefficients to be applied in the concrete strength relation based on the age of 28 days according to ACI209 for the concretes containing type II cement and tire-rubber particles were obtained equal to 3.13 and 0.91 as well as 3.32 and 0.9, respectively. Finally, the best mix design was found to do with the ordinary concrete with cement grade of 400 kg/m3, w/c of 0.5 and tire-rubber particles of 5 % that leads to the highest compressive strength by which the environmental issues could be markedly mitigated.

Composition of renders and plasters of award-winning buildings in Lisbon (Portugal): A contribution to the knowledge of binders used in the 20th Century

ABSTRACT This paper reports on the study of renders and plasters from 20th-century award-winning buildings in Lisbon (Portugal) with the Valmor Prize for Architecture. The mortars have been investigated through XRD, optical and electronic microscopy (SEM-EDS), thermal analysis (TGA/DTA), wet chemical analyses and AAS. The results reveal that the use of air lime lasted until the 1940s. It also highlights the beginning of using of Portland cement in mortars in the 1930s, mixed with air-lime, and the abandonment of mortar formulations solely based on air lime. This study highlights the use of finishing lime-gypsum-based mortars until the 1940s and different types of Portland cement from the 1940s onwards. Portland cement was the main binder for the analysed stone-imitating mortars from 1940s to 1970s. Finally, salt contamination was occasionally found in mortars, which generally reveal a good state of conservation.

Rheology and setting time of saline cemented paste backfill

As many mines around the world are situated in freshwater-scarce regions and corporations are challenged to meet increasing sustainability and environmental responsibility standards, many mining operations are seeking to use locally available saline groundwater or ocean water as mixing water in cemented backfill. However, the implications of this decision on the rheological properties (which control the flow ability or transportability) and setting time of cemented backfill must be better comprehended to allow for a confident selection of this practical solution. Hence, the effects of mixing water salinity and binder type on the rheological properties and setting time of cement paste backfill (CPB) were investigated. Viscosity, yield stress, and setting time testing were conducted on CPB made with Portland cement type I (PC) and varying slag replacement quantities, silica tailings (ST), and mixing water with NaCl concentrations from 0 g/L to 300 g/L. Supplemental testing and analyses included pH determination, TG/DTG and XRD microstructure analyses, zeta potential measurements, and electrical conductivity monitoring. Results indicate that low NaCl concentrations (10 g/L − 35 g/L) in PC-CPB increased the yield stress above the control while higher concentrations (100 g/L − 300 g/L) decreased it. An increase in NaCl concentration led to slower increase in viscosity over the first two hours of curing. Low NaCl concentrations reduced the time to initial and final setting while high concentrations increased it. These behaviors were mainly due to the effects of the Na and Cl ions on the dissolution of the cement components, and on the changes in zeta potential due to chloride adsorption. Increases in slag replacement quantities on saline CPB had minimal effect on the yield stress during the first two hours after mixing but decreased the viscosity. All tested slag contents increased the time to initial setting, though a replacement content of 75% did not increase the initial setting time as much as lower quantities. A slag replacement content of 25% increased the final setting time, though higher contents decreased it. This behavior was due to the slower reaction rate of slag, combined with slag’s consumption of NaCl and CH and greater chloride binding capabilities. The results of this study will aid mines in designing more cost-effective and efficient backfill programs.

Comparative Life Cycle Assessment of Different Portland Cement Types in South Africa

Cement has long been recognized as an energy- and emission-intensive construction material. Cement production has recently experienced significant growth despite its high energy consumption, resource usage, and carbon emissions. This study aims to assess and compare the life cycle assessment (LCA) of traditional Portland cement (CEM I) to those of three blended cement types (CEM II/B-L, CEM II/B-V, and CEM III/A), which assume mature technologies for reducing carbon emissions in South Africa, using LCA in compliance with ISO/TS 14071 and 14072. As its scope, the study employs the “cradle to gate” method, which considers the raw materials, fuel usage, electricity, transportation, and clinkering stages, using 1 kg of cement as the functional unit. The LCA analyses were performed using SimaPro 9.1.1.1 software developed by PRé Consultants, Amersfoort, Netherlands and impact assessments were conducted using the ReCiPe 2016 v1.04 midpoint method in order to compare all 18 impact categories of 1 kg of cement for each cement type. The assessment results show reductions in all impact categories, ranging from 7% in ozone depletion and ionizing radiation (CEM II/B-L) to a 41% reduction in mineral resource scarcity (CEM III/A). The impacts of global warming were reduced by 14% in the case of CEM II/B-L, 29% in the case of CEM II/B-V and 35% in the case of CEM III/A. The clinkering process was identified as the primary cause of atmospheric impacts, while resource depletion impacts were attributed to raw materials, fuels, and electricity processes, and toxicity impacts were primarily caused by raw materials. Alternative materials, like fly ash and ground granulated blast furnace slag (GGBFS), can significantly help to reduce environmental impacts and resource consumption in the cement industry.

Effect of Portland Cement on Mechanical and Durability Properties of Geopolymer Concrete at Ambient Temperature

Environmental concerns have prompted researchers to focus on the development of alternative building materials like geopolymer concrete. However, their implementation requires curing beyond 60°C, which limits their application on building sites. This study aims to design a geopolymer concrete at room temperature (30 ± 5°C) in a laboratory in Burkina Faso using a metakaolin-based geopolymer binder activated by an alkaline solution of NaOH and natural aggregates. Portland cement type CEM I 42.5 was used by mass substitution (0 to 25%) of metakaolin to promote curing at ambient temperature. The samples were cured for 7 to 28 days and characterized for physical, mechanical, and durability properties. The results showed that the incorporation of 0 to 20% cement significantly improved the compressive strength from 9.9 to 30.5 MPa and the tensile strength from 1.2 to 2.2 MPa. However, Portland cement has various effects on the durability of geopolymer concrete. It reduces the porosity accessible by water from 15 to 13% and decreases the resistance to acid attack by increasing the mass loss from 2 to 7%. This confirms that common concrete types C20/25 or C25/30 can be casted using geopolymer concrete on the sites in Burkina Faso once their durability is confirmed. Doi: 10.28991/CEJ-2023-09-07-04 Full Text: PDF

Walnut shell ash as a partial subtitute for portland cement type I and its effect on compressive strength

Walnut shell ash as a partial subtitute for portland cement type I and its effect on compressive strength

Evaluation of the Alkali-Aggregate Reaction Mitigation Potential of Alkali-Activated Fly Ash-Based Matrices Containing Different Reactive Aggregates

The present study evaluated the use of alkali-activated fly ash-based matrices containing different reactive aggregates (quartz, basalt and limestone) to mitigate the alkali-aggregate reaction (AAR). The fly ash activation was performed with sodium hydroxide (NaOH) solution, with a molar ratio (Na2O/SiO2) of 0.4. Reference matrices were prepared using Portland cement type V (ARI). All composites were prepared with a mass ratio of 1:2.25:0.47 (binder: aggregate: water/agglomerant ratio). The petrographic analyses allowed the identification of potentially reactive phases in the three studied aggregates. From the results, it was verified that the Portland cement-based matrices with basalt and quartz aggregates confirmed the reactivity of these aggregates. On the other hand, the reactivity of the same aggregates was not manifested in the CVAA-based matrices, classifying the basalt and quartz aggregates as innocuous in the alkali-activated matrix. Therefore, CVAA-based matrices mitigated AAR when using reactive basalt and quartz aggregates. However, the limestone aggregate did not show reactivity in the matrices studied.