Pozzolanic Behavior Research Articles

Bentonite Clays Related to Volcanosedimentary Formations in Southeastern Spain: Mineralogical, Chemical and Pozzolanic Characteristics

The volcanism that took place during the Neogene in the southeastern Iberian Peninsula caused a large accumulation of volcanosedimentary materials, which were subsequently altered and transformed into bentonite deposits. The mineral composition and technical quality of these deposits have been demonstrated and established in this work. The main object of this research is the mineral, chemical and thermal characterization of the bentonites that lie in the southeastern region of Spain and to demonstrate their technical capabilities to be used as pozzolans. The first phase of characterization of the samples was carried out by X-ray diffraction (XRD), oriented aggregates (OAs), X-ray fluorescence (XRF) and thermogravimetric analysis (TGA). In the second phase, a chemical–technical quality test (CTQT) was carried out, aimed at determining reactive SiO2 and reactive CaO, whereas in the third phase, a chemical pozzolanicity test (CPT) was carried out to establish the pozzolanic behavior of the samples over two test periods: 8 and 15 days. The XRD and OA analyses showed that the bentonite samples are made up of a main phase formed by montmorillonite, quartz, plagioclase-albite and chabazite–Ca. The results obtained by XRF on the bentonite samples indicated that the SiO2 contents are high and vary between 43.33% and 64.71%, while Al2O3 ranges between 15.81% and 17.49%. The CTQT established that more than 80% of the SiO2 and CaO present in the samples are reactive, which was confirmed by the results of the chemical pozzolanicity test (CPT). The results obtained show that the bentonites in this study present technical qualities that are undoubtedly reinforced by their mineral constitution and chemical composition. These tests could become a practical guide for the selection of eco-efficient materials in the production of pozzolanic cements and environmentally friendly ceramic products.

Valorization of Fine-Fraction CDW in Binary Pozzolanic CDW/Bamboo Leaf Ash Mixtures for the Elaboration of New Ternary Low-Carbon Cement

This paper presents the characterization of a binary mixture of construction and demolition waste (CDW) and bamboo leaf ash (BLAsh) calcined at 600 °C (novel mixture) and the study of its pozzolanic behavior. Different dosages in a pozzolan/Ca(OH)2 system were employed. The aim is the valorization of fine-fraction CDW that achieves a more reactive binary mixture and allows an adequate use of CDW as waste, as CDW is a material of limited use due to its low pozzolanic activity. The pozzolanic behavior of the mixture was analyzed using the conductometric method, which measures the electrical conductivity in the CDW + BLAsh/CH solution versus reaction time. With the application of a kinetic–diffusive mathematical model, the kinetic parameters of the pozzolanic reaction were quantified. This allowed a quantitative evaluation of the pozzolanic activity based on the values of these parameters. To validate these results, other experimental techniques were used: X-ray diffraction, thermogravimetry and scanning electron microscopy. Also, mechanical compressive strength assays were carried out. The results show an increase in the pozzolanic activity of binary mixes of CDW + BLAsh for all the dosages used in comparison to the pozzolanic activity of CDW alone. The quantitative assessment (kinetic parameters) shows that the binary mixture CDW50 + BLAsh50 is the most reactive (reaction rate constant of 7.88 × 10−1 h−1) and is superior to the mixtures CDW60 + BLAsh40 and CDW70 + BLAs30. Compressive strength tests show higher strength values for the ternary mixes (OPC + CDW + BLAsh) compared to the binary mixes (OPC + CDW). In view of the results, the binary blend of pozzolans CDW + BLAsh is suitable for the manufacture of future low-carbon ternary cements.

Enhancing pozzolanic activity of fly ash via dry and wet milling: A comparative study for sustainable construction material enhancement

This investigation delineates the enhancement of fly ash (FA) properties through mechanical treatments for sustainable construction applications and reducing carbon dioxide (CO2) emissions. FA, a byproduct of coal combustion in power generation, inherently exhibits limited pozzolanic activity. This research evaluates the impact of particle size reduction via dry and wet milling treatments on FA's pozzolanic behavior. The study's comparative analysis involves three FA variants: untreated raw material, dry-milled, and wet-milled FA. Extensive characterization encompassed chemical composition, physical properties, and microstructural features. Results demonstrate a marked improvement in pozzolanic activity in milled FAs, with wet milling yielding superior outcomes in particle size reduction (98% diminution compared to raw FA) and pozzolanic reactivity. The comparative assessment underscores wet milling's efficacy over dry milling and untreated FA in enhancing FA's performance as a sustainable construction material. In light of these findings, the study advocates for continued exploration of FA treatments, aiming to optimize their utility in eco-friendly construction practices.

Environmental – Solar thermal effects a long-term on the efficiency of amorphous climate-resilient mortar using a central composite design application

The objective of this investigation is to evaluate the durability of dune sand mortar containing display e-glass waste (DEGW) in severe Saharan environments, chemical attacks, or other factors that can cause cementitious materials to deteriorate at long- term. The aim is to use DEGW powder as a partial replacement for dune sand in various mortar mixtures and assess the performance of hardened mortar in terms of ultrasonic pulse velocity, dynamic elasticity modulus, compressive strength, and flexural strength and sportivity. The study also examines the influence of the curing period and different climatic conditions in curing environments, such as those in Algeria's Sahara region. The Response Surface Methodology (RSM) was used to adjust the e-waste glassy mortar, with the statistical tool Central Composite Design (CCD) approach. The hydration of cement compounds was monitored using differential thermal analysis (DTA), thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC), and X-ray diffraction (XRD). The DEGW was replaced in 5% increments from 0% to 20%. The results showed that the glassy dune sand mortar exhibited the highest properties at 20% incorporation after 365 days of severe climatic conditions. The feasibility of the proposed quadratic model was recommended for the five responses by RSM, in which the coefficient of determination (R2) ranges from 0.93 to 0.97, showing the model’s high significance. For structural display e-glassy dune sand mortar, display glass E-waste can replace 20% of dune sand, which improves all durability and environmental sustainability. Furthermore, the DSC, TGA / DTA results and XRD analysis showed that the < 0.08 mm class exhibited good pozzolanic behaviour, and the specimens significantly improved as curing periods increased.

Insights on the Mortars of Ancient Roman Aqueducts: Aqua Virgo and Aqueduct Y, Rome (Italy)

Despite the archaeological importance of Aqua Virgo, a Roman aqueduct built in 19 BC and still functioning nowadays, there is a lack of information about the mortars coming from the inner duct. This work aims to investigate the mortars from Aqua Virgo and Aqueduct Y, an unidentified aqueduct running under the first one in the La Rinascente area (between Via del Nazareno and Via dei Due Macelli, Rome, IT) through Optical Microscopy (OM), X-ray Powder Diffraction (XRPD) and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS). The aim is to understand which materials guarantee such longevity and differentiate between different intervention phases. Local natural materials with pozzolanic behaviour—in particular, Pozzolane Rosse—and ceramic fragments are widely employed, mixed or not, for the realisation of the hydraulic mortars under investigation, independently of the intervention phase. Of particular interest is the discovery of an amorphous binder composed of Si, Al, Ca, K and Mg in some samples characterised by the absence of calcite.

Bentonite Clays from Southeastern Spain as Sustainable Natural Materials for the Improvement of Cements, Mortars and Concretes

The effects of global climate change are becoming more evident and accelerating at an unprecedented pace. For this reason, human activities urgently need a paradigm shift to stop this entropic process before the consequences become irreversible. In this sense, the use of highly eco-efficient materials aimed at conveniently neutralizing CO2 greenhouse gas emissions entering into the atmosphere can contribute significantly to mitigating and reversing this process. This work aims to demonstrate the positive effects obtained when Portland cement is partially replaced by bentonite clays of volcano-sedimentary origin. The samples were initially characterized by various methods, such as Thin-Section Petrographic Study (TSP) and the analysis of mineral phases with XRD, chemical composition was determined via XRF, and morphological analysis was determined via scanning electron microscopy (SEM). To determine the technical properties of the samples, a qualitative chemical analysis (QCA) was performed, as well as a chemical analysis of pozzolanicity (CAP) at 8 and 15 days, respectively, and a study of the mechanical compressive strengths at 2, 7, 28 and 90 days. Characterization studies using TSP, DRX, FRX and SEM established that these bentonite clays have a complex mineralogical variety, composed mainly of smectite, mordenite, plagioclase and biotite, as well as altered volcanic glass and sericite. The results of the qualitative chemical analysis establish that more than 93% of the SiO2 present in the samples is reactive. Chemical analysis of pozzolanicity (CAP) showed significant pozzolanic behavior in all samples analyzed at both 8 and 15 days, while mechanical tests highlighted significant increases in mechanical strengths, with maximum values varying between 52.2 and 70.6 MPa at 90 days. These results show that the materials can be used as quality pozzolans for the manufacture of cements, mortars and concretes, which could be considered as a favorable factor and, therefore, relevant in the management and control of greenhouse gas emissions responsible for the deterioration of the environment.

Mitigation Measures of Swelling Characteristics in Alkali-Contaminated Red Earth using Fly Ash and GGBS Blends

Alkali contamination induces swelling in the inherently non-swelling soils, resulting in heave severely damaging the sub and superstructures. Stabilization measures must be taken in vulnerable areas to prevent such colossal losses. Considerable research has been conducted regarding the swelling behavior of soils contaminated with alkalis and the impact of subsequent stabilization techniques utilizing different industrial byproducts and pozzolanic materials. However, there is a paucity of such studies on the Red Earth (RE) of the Visakhapatnam region. Furthermore, limited attention was given to the effects of extremely low concentrations of alkalis on the swelling behavior of soils. RE in the study area of the Visakhapatnam region predominantly consists of quartz, kaolinite, and hematite. In phase 1 of the experimental analysis, RE was contaminated with a highly dilute NaOH solution (0.05 N), and the resulting swell characteristics were investigated. A free swell of 10% was observed. One-dimensional standard oedometer tests revealed an equilibrium swelling of 5.6%, indicating significant potential for substantial heave and subsequent damage. X-ray diffraction (XRD) analysis revealed the formation of natrolite and analcime zeolites with a hollow structure, which caused the swell. Peaks of silicate minerals like paragonite and ussingite were also observed, indicating the dissolution of authigenic minerals and new precipitations even at lower concentrations of NaOH. In phase 2, swell tests were conducted on a mixture of contaminated red earth (50% w/w), fly ash (25% w/w), and ground granulated blast furnace slag (GGBS, 25% w/w), and it was observed that the swelling was completely arrested. XRD analysis unveiled that even though siliceous zeolites were formed, the development of chrysotile, attapulgite, tobermorite, and dicalcium silicate effectively inhibited the swelling with their pozzolanic behavior.

Aqua Alexandrina and Fragole cistern: characterization of mortars from Roman constructions, Rome (Italy)

Aqua Alexandrina is the last aqueduct built by ancient Romans for the city of Rome. At Giovanni Palatucci Park, the archaeological ruins run close to a pre-existent water system, Fragole cistern. This research aims at characterizing mortar samples from both constructions, to identify the materials used and infer about the technological level and the provenance of materials, using a multi-analytical approach. Combining the information obtained through the petrographic investigation of mortar thin sections at optical microscopy and scanning electron microscopy with energy-dispersive X-ray spectroscopy, and X-ray powder diffraction on finely powdered samples and thermogravimetric analysis on the binder fraction, it was possible to attest the presence of both artificial and natural materials with pozzolanic behavior, which conferred hydraulicity to the mortars. The results show that materials are very similar in both constructions, confirming a well-established know-how in the production of hydraulic mortars by the Romans. The volcanic products used as aggregate are identified with two large pyroclastic-flow deposits erupted by the Colli Albani Volcanic District which extensively crop out in the area of Rome: Pozzolane Rosse and Pozzolanelle.

Assessing regional variability in chemical composition and pozzolanic reactivity of corn stover ash in the United States

This study examines the regional variability in the chemical composition and pozzolanic reactivity of corn stover ash (CSA) produced from corn stover samples collected from different locations in the U.S. Corn stover samples were collected from local farms in Nebraska and Iowa, while information about Kansas CSA was obtained from existing literature. The findings reveal significant variability in the chemical composition of untreated CSA across different regions. However, through the use of pretreatment techniques such as acid soaking, the compositional variations can be considerably reduced. The results of the modified R3 test demonstrate that CSA exhibits pozzolanic behavior that falls between that of fly ash and silica fume. The reactivity of CSA was found to be independent of geospatial factors but heavily influenced by the specific pretreatment methods employed in the study. Furthermore, the study indicates that the reactivity of CSA is less variable compared to fly ash and silica fume.

Retracted: A study on the strength and durability characteristics of fiber-reinforced recycled aggregate concrete modified with supplementary cementitious material

Recycled aggregate (RA) made from waste concrete is an environmentally friendly alternative to natural aggregate (NA) for concrete manufacturing. However, compared to NA concrete, concrete produced with recycled aggregates has poor characteristics. Supplementary cementitious materials (SCMs) can be used to enhance the poor properties of recycled aggregate concrete (RAC). Silica fume and fly ash are commonly used SCMs in the World, but their high usage led to a shortage of silica fume and fly ash. Still, the deficiency of these materials in large parts of the world is a challenge that requires exploring alternative feedstock materials for the construction industry in the coming years. Wheat straw ash (WSA) is an agricultural waste product that could be used as an alternative SCM due to its pozzolanic behavior to enhance the properties of RAC. In addition, concrete is brittle and needs reinforcement, for which polypropylene fibers (PPFs) can be used. The current research examines the mechanical characteristics of fiber-reinforced RAC, including compressive strength, splitting tensile strength, and ductility performance. Durability indicators, such as chloride diffusion, chloride penetration, acid resistance, and water absorption test, were also assessed. The results showed that concrete samples with 10% WSA, 50% RA and 1.5% PPFs had the highest compressive and splitting tensile strength, 60.2 MPa and 7.25 MPa, respectively, representing increases of 24.75% and 30.65%, as compared to plain samples at 56 days. In these samples, water absorption was reduced by 13% due to the finer WSA particles resulting in the lowest reduction in strength and mass recorded when exposing concrete samples to acidic media. The statistical analysis also validated that irrespective of WSA and PPFs, the concrete with 0% RA had the highest performance in strength and durability behavior. The study showed that WSA and PPFs might be employed in tandem to offset the poor behavior of RA, enhance the bond between fibers and concrete, and improve the mechanical strength and durability performance of RAC, thus demonstrating its suitability as a sustainable and economical construction material.

Efficient use of ceramic waste powder in Cementitious Grout for the Development of Sustainable Semi-Flexible Pavement Surfaces

Cement-based grouts are described as a liquid mixture with higher flowability that contains cement, additives, water, and a superplasticizer. Cement-based grouts can be utilized to fill minor voids and gaps in addition to repairing cracks in earthen structures to restore structural continuity. In most cases, structural grouting is used in conjunction with other strengthening methods like adding tie-rods or reinforcing meshes. Grout is usually used with semi-flexible pavement (SFP). SFP is a new pavement technology comprised of open-graded asphalt concrete with a high air void content that is filled by injecting special grouting materials. The goal of this research is to figure out what happens to the mechanical properties of grout when a proposed by-product is used as a supplement to cementitious materials. The specified grouts were made from cement, water, ceramic waste powder (CWP), and superplasticizer (SP). Scanning electron microscopy (SEM) and energy-dispersive x-ray (EDX) analysis were used to characterize the physical and chemical properties of the waste material after it had been crushed and finely ground. The pozzolanic behaviour of the material was evaluated by substituting ceramic waste for Portland cement at varying percentages (from 15% to 50%), and the modified grout was characterized through a variety of tests that included flow cone testing, as well as compression and flexural strength tests Based on the results of these tests, the best amount of CWP to use as a replacement for cement in terms of its mechanical properties is 20%.

Development of sustainable ultra-high-performance concrete containing ground granulated blast furnace slag and glass powder: Mix design investigation

Ultra-high performance concrete (UHPC) is one of the most important advances in concrete technology. Since UHPCs possess outstanding mechanical properties and durability, they require less material consumption and post-maintenance conventional concrete. This helps reduce the detrimental impacts of concrete structures on the natural environment. However, the high price and high carbon intensity of UHPCs are main hurdles for their wide adoption. Recently, studies have revealed that waste glass at a certain fineness exhibits pozzolanic behaviour. This paper investigates the effect of replacing cementitious components in UHPCs with “medium-size” glass powder (GP) on the workability, mechanical properties, sustainability, and cost efficiency of the UHPCs. While principal binders (cement and silica fume (SF)) were replaced by “medium-size” GP in Series I, ground granulated blast furnace slag (GGBFS) and coarse GP were simultaneously used to substitute for SF in Series II. Regardless of curing regimes, slag GP-UHPC mixtures always exhibited better workability and greater compressive/flexural resistance, indicating the great synthetic effect of GP and GGBFS substitution. In addition, results showed that up to 30% of GP replacement, most specimens yielded reasonable mechanical properties, high cost efficiency, and low carbon indexes compared to the reference mixture. Specifically, while workability reduced with the increase of GP portions in the GP-UHPCs, it rose with larger replacement percentages of SF in the slag GP-UHPCs. For both series, 20% replacement of GP was the optimal ratio, resulting in cost-saving and carbon-efficient mix designs with comparable compressive/flexural capacity.

Combination of Rice Husk Ash (RHA) and Sewage Sludge Ash (SSA) as sustainable replacement material for cement in concrete

Increase in the demand of conventional construction materials and the need for providing a sustainable growth in the construction field has prompted the designers and developers to opt for ‘alternative materials’ feasible for use in construction. For this objective, the use of industrial waste products and agricultural by products are very constructive. These industrial wastes and agricultural by products such as Rice Husk Ash and Sewage Sludge Ash can be replaced instead of cement because of their pozzolanic behaviour, which otherwise requires large tract of lands for dumping. In the present investigation, Rice Husk Ash has been used as an admixture to cement in concrete and its properties has been studied. An attempt was also done to examine the strength and workability parameters of concrete. Five different replacement levels namely 5%, 10%, 15%, 20% and 25% are selected and studied with respect to the replacement method. The samples had been tested with non-destructive test to compare with normal concrete (OPC). There was an increment in number of concretes at 10% amount replacement SSA and RHA, but the rebound number declined when the amount replacement SSA and RHA are developing more than 10%. In addition, the concrete also showed increasing of compressive strength within the additional curing period, which was 7 days and 28 days. The overall results indicated that the properties and performance of concrete with 10% of combination of Rice Husk Ash (RHA) and Sewage Sludge Ash (SSA) replacement had reached the most optimum values on the measured.

Production of new generation and sustainable concrete using Rice Husk Ash (RHA): A review

Rice husk is an agricultural by-product available in huge quantities, particularly in India. This is an appropriate biomass source for the production of energy. Compared to other agricultural by-products like sugar cane bagasse, the burned rice husk yields nearly 20% of ash, with the chief constituent of silica that will be typically amorphous when properly burned. Wide-ranging research in the last two decades has permitted the use of Rice Husk Ash (RHA) as a supplementary cementitious material (SCM) in cement-based products, whereby significant enhancements in strength and durability properties can be accomplished. From published literature, it has been found that this bio-based material is possessing high pozzolanic properties which have made this a novel technology because of the green nature of the exercise. The CO2 emission with the utilization of RHA is zero. Hence, a partial replacement of OPC in cement composites with this cementing additive is a breakthrough for our environment with improved sustainability. This paper discussed the state-of-the-art pozzolanic behavior of RHA, its Physio-chemical characteristics, and its influence on the mechanical and durability properties of cementitious composites. The outcome of the review helps in fulfilling the massive burdens on the construction industry economically and sustainably.

Pozzolanic reaction and strength activity index of dolomite powder incorporated cement mortar

Assessment of pozzolanic activity of an alternative material is a key parameter for its application as a cementitious material. This study has been conducted to check the scope of dolomite powder in its native and calcined state as a substitute for cement for sustainable construction practices. Dolomite is a variety of limestone consisting of calcium carbonate and magnesium carbonate in predominant compositions. The chemical composition of dolomite powder is determined using X-ray florescence (XRF) technique. XRF test results showed the presence of 31.08 % of Calcium Oxide and 21.3 % of Magnesium Oxide as major compounds in dolomite powder. Frattini and Strength Activity Index (SAI) tests have been conducted to analyze the pozzolanic activity of dolomite powder. Frattini test determines the consumptions of hydroxyl ion (OH–) and calcium ion (Ca+2), which are plotted in the solubility curve to decide the pozzolanic behavior of a material. The test on dolomite powder in its native state resulted in no pozzolanic activity, while in the calcined form, pozzolanic activity was observed. This behaviour was due to the activation of quick lime after the calcination process. The strength Activity Index (SAI) test is conducted to compare the compressive strength of nominal and modified mixes at 7 and 28 days. The dolomite powder in its native state satisfied the Strength Activity Index (SAI) criteria at 7 and 28 days owing to its ultra-fine particle size. The SAI test observations were on the higher side in the calcined state as both – ultra-fine particle size and quick lime contributed to the strength of the mix.

Effect of fluorite addition on the reactivity of a calcined treated spent pot lining in cementitious materials

Treating SPL by the low caustic leaching and liming process generates an inert nonhazardous residue called LCLL Ash and a fluorite byproduct Calcined LCLL Ash that is ground into a fine powder demonstrates pozzolanic behavior in cement. The effect of the calcination temperature and fluorite byproduct addition on the reactivity of LCLL Ash was studied by the compressive strength activity index, Frattini test and Rilem R3 tests followed by XRD analysis. At 800°C, the formation of nepheline causes alkali uptake, the LCLL Ash showed a slightly lower reactivity with 10% fluorite addition. At 1000°C, calcined LCLL Ash/CF showed a better amorphization of phases and increasing reactivity due to reactions between fluorite and sodium oxide. Unlike LCLL Ash, no delay in hydration or hydro reactivity was observed with calcined LCLL Ash/CF.

Effect of silica fume on the physical, hydrological and mechanical properties of pervious concrete

Pervious concrete is a special concrete which is prepared by partial or complete elimination of fine aggregates. Thus, the quality of the cement paste plays a crucial role in defining the properties of pervious concrete. This study aims at investigating the impact of replacing cement in pervious concrete by silica fume. Cement in pervious mix was replaced partially by silica fume in a range of 0 to 20% at 5% intervals. Two varying sizes of aggregates namely 12.5 mm and 20 mm (single-sized) were used in mixes and the aggregate to cementitious material ratio was maintained at 3.54 with a water cement to cementitious material ratio of 0.35. The investigated properties include density, porosity, permeability, abrasion resistance and mechanical properties namely compressive strength, tensile strength and flexural strength. Incorporation of silica fume up to 15% was found to cause considerable positive impact on the mechanical properties of pervious concrete irrespective of the aggregate size due to their pozzolanic behavior which improved the paste formation. The compressive strength, split tensile strength and flexural strength were increased to a maximum of 20.14%, 12.73% and 13.74% respectively with the use of 12.5 mm aggregates and 15% of silica fume. The output of the experiments revealed that the cement content of the pervious mix can be optimally replaced up to 15% with silica fume for balanced physical, hydrological and mechanical properties.

Potential of Palm Oil Fuel Ash as a Partial Replacement of Fine Aggregates for Improved Fresh and Hardened Mortar Performance

The growth of Malaysia has caused many industries to grow rapidly, especially construction industries due to the demand for more homes, buildings, and infrastructure. The production of concrete and mortar is highly requested. Therefore, the demand for fine aggregate becomes higher because fine aggregate is one of the main elements in concrete and mortar production. The high demand for fine aggregates will create a worrying situation where the fine aggregate crisis will worsen. An alternative was introduced to replace the fine aggregate known as palm oil fuel ash (POFA) in order to reduce the use of natural resources such as fine aggregates and lead to the reduction of fine aggregate mining activity. POFA produced from palm oil fibre, palm oil shell, and mesocarp at high temperature has no benefits in the commercial return. Thus, POFA that has accumulated in landfill has the ability to create environmental pollution. Due to the pozzolanic behaviour of POFA, it could be relevant when POFA is used in the production of mortar as a partially fine aggregate replacement. There is a limited study on the effects of POFA as a partially fine aggregate replacement in the production of mortar. The aim of this research is to study the effects of POFA on the workability of fresh mortar, and for the hardened mortar, compressive strength and microstructural analysis will be analysed. A total of 45 cubes with dimensions of 100 mm × 100 mm × 100 mm were cast at different percentages of POFA at 0%, 2.5%, 5%, 7.5%, and 10% by the weight of fine aggregates. Slump and flow table tests were conducted during the casting process to determine the workability. All the specimens were water cured at days 3, 7, and 28 before being tested with a compression test and scanning electron microscope (SEM) on the hardened mortar. It was discovered that 0% POFA recorded the highest workability. Furthermore, the laboratory results showed that the 2.5% POFA in the mortar recorded the highest compressive strength compared to other specimens. Moreover, the microstructure of the mortar specimen was observed to be denser, and the pores were refined with the presence of POFA, compared to the control specimen. Based on the findings, this research enables us to give an understanding of the effect of POFA incorporated in mortar as a partially fine aggregate replacement in terms of workability, compressive strength, and microstructural analysis. Based on the results from this research, the advantage of POFA can be fully utilized and can help reduce the environmental problems.

Valorification of Egyptian volcanic tuff as eco-sustainable blended cementitious materials

Rhyolite rocks extend from southern Egypt to northern Egypt in the Eastern Desert, and no effective economic exploitation of them has been discovered so far. The pozzolanic activities of different volcanic tuffs (VT) supplied from the Eastern Desert located in Egypt have been investigated as natural volcanic pozzolan materials to develop new green cementitious materials for achieving sustainability goals in the construction field. Experimentally in this paper, the pozzolanic activities of seven diverse specimens of Egyptian tuffs taken with standardized proportions of 75:25% (Cement: volcanic tuffs) were investigated. Pozzolanic features of such tuffs are examined comparatively via strength activity index (SAI), TGA, DTA, and the Frattini’s test. Chemical composition, petrographic, and XRD analysis were also performed for tuffs samples. The pozzolanic reaction degrees were determined according to the compressive strengths at 7, 28, 60 and 90 days with different replacement ratios (20, 25, 30 and 40%) of tuffs samples. Additionally, the micro-filler effects in mortar and concrete were determined by measuring the heat of hydration in mortar samples and the compressive strength of concrete with different additive ratios for tuffs samples besides, the concrete slump test. The results show that TF6 gives a lower cement heat of hydration value which is less than 270 J/g at 7 days. Also, its performance in concrete is better than silica fume at late strength (28 days) since the concrete index value is 106.2% by compared to the concrete index of silica fume 103.9 and therefore it can be used as an alternative to high price and quality variable silica fume (SF) for producing high-performance green concrete. Due to the good pozzolanic behavior proved by nearly most volcanic tuffs, along with their low cost, this study will be profitable for very auspicious the use of Egyptian volcanic tuffs for developing sustainable and eco‑friendly blended cement.

Quantification of the reaction degree of fly ash in blended cement systems

Fly ash (FA) usually has an insufficient reaction degree in cement-based materials, and the quantification of its reaction degree is essential for understanding its pozzolanic hydration behavior. This work presents a new approach to quantifying the reaction degree of FA in blended cement systems, based on the chemical composition differences revealed by image analysis. We considered some specific elements rich in the unreacted FA particles but poor in the surrounding paste as the characteristic elements, and then employed them to segment the unreacted FA particles from the blended cement paste. In light of the high heterogeneity of FA, one can conduct intensity normalization during the analysis, using grey-level images that are displayed in the intensity of each characteristic element, respectively. At last, the unreacted FA particles, including the partially reacted and irregular-shaped ones, were discriminated from the paste, enabling an accurate calculation of the FA's reaction degree.