Search

The release of Neogene volcanism in the southeastern part of the Iberian Peninsula produced a series of volcanic structures in the form of stratovolcanoes and calderas; however, other materials also accumulated such as large amounts of pyroclastic materials such as cinerites, ashes, and lapilli, which were later altered to form deposits of zeolites and bentonites. This work has focused on an area located on the northern flank of the San José-Los Escullos zeolite deposit, the only one of its kind with industrial capacity in Spain. The main objective of this research is to characterize the zeolite (SZ) of this new area from the mineral, chemical, and technical points of view and establish its possible use as a natural pozzolan. In the first stage, a study of the mineralogical and chemical composition of the selected samples was carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF), and thermogravimetric analysis (TGA); in the second stage, chemical-qualitative and pozzolanicity technical tests were carried out at 8 and 15 days. In addition, a chemical analysis was performed using XRF on the specimens of mortars made with a standardized mixture of Portland cement (PC: 75%) and natural zeolite (SZ: 25%) at the ages of 7, 28, and 90 days. The results of the mineralogical analyses indicated that the samples are made up mainly of mordenite and subordinately by smectite, plagioclase, quartz, halloysite, illite, and muscovite. Qualitative chemical assays indicated a high percentage of reactive silica and reactive CaO and also negligible contents of insoluble residues. The results of the pozzolanicity test indicate that all the samples analyzed behave like natural pozzolans of good quality, increasing their pozzolanic reactivity from 8 to 15 days of testing. Chemical analyses of PC/SZ composite mortar specimens showed how a significant part of SiO2 and Al2O3 are released by zeolite while it absorbs a large part of the SO3 contained in the cement. The results presented in this research could be of great practical and scientific importance as they indicate the continuation of zeolitic mineralization beyond the limits of the San José-Los Escullos deposit, which would result in an increase in geological reserves and the extension of the useful life of the deposit, which is of vital importance to the local mining industry. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This paper investigates the use of excavated soil from the Grand Paris Express (GPE) project in blended low-carbon binders. The GPE targets to improve the quality of life of the inhabitants of the Paris metropolitan area by providing better transportation, housing, and job opportunities. However, the quantity of excavated material since the start of the GPE project is around 28 million tons (Mt) and will reach 47 Mt by 2027 (Bilan des émissions de gaz à effet de serre de la Société du Grand Paris et du Grand Paris Express, 2022). Soil samples were taken from 4 sites of the GPE project and analyzed for their physical, chemical, and mineralogical characteristics. Results have evidenced that using flash-calcination (FC) treatment can sensitively enhance material properties. Pozzolanic activity of both raw and treated materials, assessed by Chapelle and Frattini tests showed that flash-calcined excavated soils have a chemical reactivity. Mortars formulated with blended cement produced with the FC materials were mechanically tested and disclosed interesting performances. The evaluation of the environmental impact consisting of leaching tests demonstrated that the treated material can be considered as inert as well as the mortars prepared. These findings indicate soils from the GPE project are suitable for reuse in cementitious matrixes and have the potential to provide economic and environmental benefits. [ABSTRACT FROM AUTHOR]

An effective method to make cement and concrete more sustainable is to blend them with the proper supplementary cementitious materials (SCMs). This study evaluates a pair of schist‐type materials with slightly different phase compositions, as a partial replacement for ordinary Portland cement (OPC). Materials received from several mines in ground powder form were studied by X‐ray diffraction, thermogravimetric analysis (TGA), and scanning electron microscopy. According to the TGA results, the activation procedures for the candidate SCMs were determined. The as‐received powders were heat treated in three different decomposition regimes (30%, 50%, and 80% of the total weight losses during thermal decomposition). These regimes corresponded to the activation level of the potential SCMs due to the de‐hydroxylation of the clay‐type minerals within them. Pozzolanic reactivity (pozzolanicity) of untreated as well as treated powders were estimated via electrical conductivity measurements in saturated calcium hydroxide solution. Blended cement pastes with 30 wt.% of OPC substituted with calcined clay‐type materials have developed mechanical properties equal to those of pure cement (100 wt.% OPC) paste after 28 days of hydration time. Two blended cement pastes prepared with candidate SCMs were compared to 100% OPC and OPC composite paste with metakaolin, which is regarded in the literature as a standard. [ABSTRACT FROM AUTHOR]

Abstract An effective method to make cement and concrete more sustainable is to blend them with the proper supplementary cementitious materials (SCMs). This study evaluates a pair of schist‐type materials with slightly different phase compositions, as a partial replacement for ordinary Portland cement (OPC). Materials received from several mines in ground powder form were studied by X‐ray diffraction, thermogravimetric analysis (TGA), and scanning electron microscopy. According to the TGA results, the activation procedures for the candidate SCMs were determined. The as‐received powders were heat treated in three different decomposition regimes (30%, 50%, and 80% of the total weight losses during thermal decomposition). These regimes corresponded to the activation level of the potential SCMs due to the de‐hydroxylation of the clay‐type minerals within them. Pozzolanic reactivity (pozzolanicity) of untreated as well as treated powders were estimated via electrical conductivity measurements in saturated calcium hydroxide solution. Blended cement pastes with 30 wt.% of OPC substituted with calcined clay‐type materials have developed mechanical properties equal to those of pure cement (100 wt.% OPC) paste after 28 days of hydration time. Two blended cement pastes prepared with candidate SCMs were compared to 100% OPC and OPC composite paste with metakaolin, which is regarded in the literature as a standard.

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. [ABSTRACT FROM AUTHOR]

Climate change is already an undeniable reality, and it is a direct consequence of our society's lifestyle and the indiscriminate use of certain materials, such as Portland cement, which causes the emission of gases and waste that contributes to the greenhouse effect. The object of this work is to present the results obtained from research on pyroxenic andesites that have become altered to zeolite and their use as alternative, eco-efficient materials that improve the quality of cement through a standardized partial substitution. In this work, four samples of pyroxenic andesites altered to zeolites (PAAZ) and two samples of unaltered andesites (UPA) were analyzed. The methods used in this study are as follows: petrography of thin section (PTS), chemical analysis of X-ray fluorescence (XRF) and phase determination by X-ray diffraction (XRD). Other tests were carried out to determine the quality of the PAAZ from a technical and practical application point of view, such as chemical analysis of pozzolanicity (CPT) at 8 and 15 days, as well as mechanical compression tests at 2, 7, 28 and 90 days. Petrographic and phase analyses show that the original mineral components of the samples such as pyroxene, amphibole, plagioclase and mica were leached and replaced by more than 90% with mordenite and smectite. XRF analyses indicates an anomalous rise in SiO2, a drastic reduction in alumina Al2O3 and a significant increase in alkaline compounds over alkaline-earth compounds in samples of altered pyroxenic andesites (PAAZ) with respect to samples of unaltered andesites (UPA). The pozzolanicity test establishes that the samples of unaltered andesites do not behave like pozzolans at 8 or 15 days; however, altered andesites experienced remarkable pozzolanic reactivity in the same periods. The mechanical compression tests carried out on specimens made with PAAZ and Portland cement showed a growing increase in mechanical resistance from 2 days (15.2 MPa) to 90 days (72.1 MPa). These results suggest that pyroxenic andesites altered to zeolite can be an ideal alternative to partially replace Portland cement, which in turn could contribute to the preservation of the environment and a more rational use of traditional resources. [ABSTRACT FROM AUTHOR]

The work aims to observe the effect of waste ceramic brick (WCB), ground in two times, 60 and 120 min for use in mortar. The crystalline phases presented in clays of the north of Rio de Janeiro have already been identified, indicating that after firing at an adequate temperature, it is possible to apply it as a pozzolanic material. In this direction, in Brazil there is a single metakaolin industry in São Paulo operating in the domestic market supplying pozzolanic material for all regions of the country. The researched material was burned in the industry at approximately 700 °C, and its pozzolanic activity was tested by the Luxán test presenting 2.01 mS/cm (good pozzolanicity). The mortars proportions were 1:6 (cement: sand), with the addition of 0% (reference), 10%, 20% and 30% of WCB, and their crystalline phases were analyzed by XRD and it was not identified a kaolinite peak, a good indication of the transformation to metakaolinite. The tests in both fresh and hardened state were performed. For both grindings, the residue reacted with the paste, a fact confirmed by the nucleation calorimetry of particles

The search for alternative materials to replace ordinary Portland cement has been the object of work that enhances the investigation of the use of pozzolanic materials and the reduction of the carbon footprint with supplementary cementitious materials. However, not all materials are available to meet the large-scale demand for cement replacement. A relevant exception is the calcined clay, a material found worldwide that, when subjected to appropriate heat treatment, presents pozzolanic reactivity and can be used as a supplementary material to cement. This review presents, through a systematic search, methods for measuring the pozzolanic reactivity of calcined clays, namely, direct, indirect, qualitative, quantitative, chemical and physical methods such as electrical conductivity (Lùxan), the force activity index, the modified Chapelle, R3, Frattini test, thermal analysis, X-ray diffraction and X-ray fluorescence spectrometry. The most usual methods to assess the pozzolanic reactivity of calcined clays were exposed and analyzed. It should be pointed out that there is greater use of the Frattini and modified Chapelle methods as well as the analysis of the mechanical strength behavior of the material in cementitious matrices. X-ray diffraction and thermal analysis were exposed as the most used correlation methods but it was also concluded that different tests are needed to generate accurate results. [ABSTRACT FROM AUTHOR]

Presently, the search for urgent solutions to mitigate climate change has become a global priority. One of the most important challenges is the characterization, standardization, and technology of sustainable natural raw materials, which will significantly improve the quality of common types of cement, the production process of which emits large amounts of greenhouse gases into the atmosphere. This work is focused on the study of natural kaolinitic clays (NKC) from the eastern part of the Iberian Peninsula and its main objective is to define and normalize their properties as natural pozzolanic materials. This research consists of an initial study to determine the morphological and chemical properties using SEM and XRF. Furthermore, the physical properties of the samples were studied, such as thermic treatment (TT), Blane particle finesse (BPF), real density (RD) and apparent density (AD), porosity (P), volume stability (VS) and start and final setting time (SFST). On the other hand, technological analyses were carried out as follows: chemical analysis (CATQ), pozzolanicity (CAP), mechanical compression strength tests at 7, 28, and 90 days (MCST) as well as the ultrasonic pulse velocity (UPV). XRF results indicated that the SiO2 content (49.9–51.0%) of kaolinitic clay in its natural state (NKC) increases to 57.41 and 58.10%, respectively, when calcined (CKC). The chemical analysis of pozzolanicity established that the NKC does not show pozzolanic activity during the first 8 and 15 days; however, once calcinated, its pozzolanic reactivity increases substantially. On the other hand, the results of the mechanical stress tests (MCST) indicate an exponential increase in mechanical resistance from 7 to 90 days, which is higher in mortars made with CKC; similarly, and according to the results of the calculation of the Resistant Activity Index (RAI), it shows that the substitutions of Portland cement (PC) by NKC are effective between the ranges of 10 and 25%, while in the case of the substitution of PC by CKC, all formulations (10, 25 and 40%) are effective. This research establishes that the kaolinitic clays of the east of the Iberian Peninsula can be considered quality pozzolanic materials, capable of partially replacing Portland cement. The results presented here could be used as guidelines for the understanding and application of natural pozzolanic materials contributing to the improvement of types of cement, mortars, and concretes, which would positively affect the quality and preservation of the environment as well as the sustainability of eco-efficient construction materials. [ABSTRACT FROM AUTHOR]

The natural kaolin deposits are crystalline inert with low CaO contents and surface area. Therefore, kaolin is not a suitable material used to produce Alkali Activated Binders (AAB) due to the low strength resulting. This work aims to optimize kaolin into metakaolin and use them later as AAB. Initially, kaolin was characterized to determine its chemical compositions and reactivity before and after calcination through XRF, XRD and Chapelle test. Kaolin is thermally treated at different firing conditions (500, 550, 600, 650 and 700 °C for 15, 30 and 60 min, i.e., 15 firing trials). The optimum calcination parameter revealed according to the Chapelle method is 600 °C for 60 min. Paste specimens were fabricated from selected metakaolin according to different pozzolanicity using 5, 10 and 14 wt% NaOH as activation media. The paste specimens were cured at 40, 60 and 80 °C for 24 hrs, then cured at room temperature with 98 ± 2 % relative humidity for 28 days. It is found that metakaolin paste with high optimum pozzolanicity produces AAB with higher mechanical compressive strength values (20.9 MPa) after curing at 60 °C. The latter mechanical compressive strength is maximized (27.09 MPa) when metakaolin pastes are activated by 14 wt% NaOH and 10 wt% Na2SiO3 mixture.

The object of this work is to study and characterize diatomites from the southeast of the Iberian Peninsula to establish their character and quality as natural pozzolans. This research carried out a morphological and chemical characterization study of the samples using SEM and XRF. Subsequently, the physical properties of the samples were determined, including thermic treatment, Blaine particle finesse, real density and apparent density, porosity, volume stability, and the initial and final setting times. Finally, a detailed study was conducted to establish the technical properties of the samples through chemical analysis of technological quality, chemical analysis of pozzolanicity, mechanical compressive strength tests at 7, 28, and 90 days, and a non-destructive ultrasonic pulse test. The results using SEM and XRF show that the samples are composed entirely of colonies of diatoms whose bodies are formed by silica between 83.8 and 89.99% and CaO between 5.2 and 5.8%. Likewise, this indicates a remarkable reactivity of the SiO2 present in both natural diatomite (~99.4%) and calcined diatomite (~99.2%), respectively. Sulfates and chlorides are absent, while the insoluble residue portion for natural diatomite is 1.54% and 1.92% for calcined diatomite, values comparatively lower than the standardized 3%. On the other hand, the results of the chemical analysis of pozzolanicity show that the samples studied behave efficiently as natural pozzolans, both in a natural and calcined state. The mechanical tests establish that the mechanical strength of the mixed Portland cement and natural diatomite specimens (52.5 MPa) with 10% PC substitution exceeds the reference specimen (51.9 MPa) after 28 days of curing. In the case of the specimens made with Portland cement and calcined diatomite (10%), the compressive strength values increase even more and exceed the reference specimen at both 28 days (54 MPa) and 90 days (64.5 MPa) of curing. The results obtained in this research confirm that the diatomites studied are pozzolanic, which is of vital importance because they could be used to improve cements, mortars, and concrete, which translates to a positive advantage in the care of the environment. [ABSTRACT FROM AUTHOR]

On Earth, there are several natural disasters, many ask the question of what is happening. The Earth is suffering from the harms of global climate change. The DRC, in its Southwestern part, is vulnerable to this phenomenon. The main cause is the presence of cement plants that produce Portland cement, by heating the limestone to about 1450°C. At this process temperature, limestone releases CO2 which is among the very harmful greenhouse gases. It is for this reason that a study of an ecological cement with 75% clinker and 25% basalt was conducted. The resistance of this composite cement is well. [ABSTRACT FROM AUTHOR]

The eruption of the Cumbre Vieja volcano on 19 September 2021, resulted in the deposition of large quantities of volcanic ash (VA), causing a great impact on the citizens. This work aims to study the properties of this volcanic ash as pozzolanic raw materials to establish their potential use in the development of sustainable cement. Results of chemical and technical characterization are presented. To achieve this goal, Ordinary Portland Cement (OPC) was replaced with standardized percentages of OPC/VA: 10, 25, and 40%. Characterization studies were carried out using chemical analysis of X-ray fluorescence (XRF), chemical quality analysis (QCA), pozzolanicity test (PT) at 8 and 15 days, as well as determining the mechanical strength (MS) at 7, 28, and 90 days. The results obtained by XRF and QCA established that the chemical composition of the VA corresponds to that of the natural pozzolan typical of pyroclastic genesis. The PT test showed that the analyzed samples have a marked pozzolanic nature, both at 8 and 15 days, showing a significant increase in their hydraulic reactivity. Likewise, the MS tests confirmed a continuous increase in mechanical compressive strength, which increased significantly from 7 to 90 days of curing, reaching more than 58 MPa. On the other hand, mechanical tests showed that the three types of dosages used OPC/VA: 10, 25, and 40% were equally effective, with OPC/VA formulations: 10–25% being the most effective. The results obtained in this research could be used by local industries as a guide for the correct use of the volcanic materials of this island, both for the manufacture of construction materials, such as aggregates, and to produce pozzolanic cement with low CO2 emissions, thus having a positive impact on the environment. Finally, the great natural availability of natural VAs in the surrounding areas of La Palma could cover part of the needs for materials used in the construction and restoration of houses and infrastructures damaged during the volcanic eruption. [ABSTRACT FROM AUTHOR]

The geological nature of the territory of the Republic of Cuba has favoured the formation of large and varied deposits of volcanic tuffs enriched by various species of zeolites. Today, new zeolite deposits continue to be discovered in the country. This work aims to present the results of a study carried out in an unexplored area that is located approximately 1.2 km east of the Loma Blanca deposit, outside the mining operation limits. To carry out this research and to establish a qualitative comparison between both sample populations, four samples were taken from the study area, and another four were taken from the Loma Blanca deposit. The characterisation of the samples was performed by XRD, SEM, and XRF. The pozzolan quality was determined by the pozzolanicity test (PT) and quality chemical analysis (QCA). Finally, a study of the mechanical strength (MST) was performed at 7, 28, and 90 days, using mortar specimens made with PC/ZT: 75–25% and PC/ZT: 70–30%, respectively. The results of the studies using XRD, SEM, and XRF indicated that both groups of samples had a similar complex mineralogical composition, consisting mainly of mordenite and clinoptilolite accompanied by secondary phases such as quartz and amorphous materials in the form of altered glass. The pozzolanicity test showed that both the samples from the study area and those from the Loma Blanca deposit behaved like typical pozzolans, which is a trend that can be seen in the high values of mechanical strength to compression up to 72 MPa for the PC/ZT: 75–25% formulation and 66 MPa for the PC/ZT: 70–30%. The results obtained establish that the zeolite varieties detected in the study area are similar to those of the Loma Blanca deposit, which could have a positive impact on the increase in current reserves, especially for manufacturing pozzolanic cements with properties that contribute to the preservation of the environment.

The speed at which climate change is happening is leading to a demand for new pozzolanic materials that improve the quality of cements and, at the same time, limit the emission of greenhouse gases into the atmosphere. The main objective of this work is the detailed characterization of an ignimbrite sample (IGNS) to demonstrate its effectiveness as a natural pozzolan. To meet this objective, a series of tests were carried out. In the first stage, mineral and chemical analyses were performed, such as petrographic analysis by thin section (TSP), X-ray diffraction (XRD), oriented aggregate (OA), scanning electron microscopy (SEM) and X-ray fluorescence (XRF). In the second stage, the following technical tests were carried out: chemical quality analysis (QCA), pozzolanicity test (PT) and mechanical compressive strength (MS) at 7, 28 and 90 days, using mortar specimens with ignimbrite/cement formulation (IGNS/PC): 10, 25 and 40% to establish the pozzolanic nature of the ignimbrite. The results of the mineral and chemical analyses showed that the sample has a complex mineralogical constitution, consisting of biotite mica, potassium feldspar, plagioclase, smectite (montmorillonite), quartz, volcanic glass, iron, titanium and manganese oxides, chlorite and chlorapatite. On the other hand, the technological tests revealed the pozzolanic nature of the sample, as well as visible increases in the mechanical compressive strengths in the three proportions, the most effective being IGNS/PC:10% and IGNS/PC:25% at 7, 28 and 90 days of setting. The results obtained could be applied in the formulation of new pozzolanic cements with ignimbrite as a natural pozzolanic aggregate. [ABSTRACT FROM AUTHOR]

Multiple studies propose the incorporation of waste glass into concrete as a sustainable solution covering many aspects, including preserving natural resources, utilizing waste materials and reducing concrete cost. In the present study, the suitability of different types of flat glass waste from a local industry as a supplementary binder or aggregate was examined. Different protocols were followed based on the European and American Standards. The chemical composition, density, mineralogy and salts content of the samples were tested. For the use of the glass waste as a binder, the strength activity and pozzolanicity indexes were measured according to EN 450-1 and ASTM C593, respectively. For the use of the glass waste as aggregates, the granulometry and the flakiness and shape indexes of the samples were determined. Alkali-silica reaction, freeze-thaw and magnesium sulfate tests for the aggregates were also performed. It can be concluded that waste glass has a medium pozzolanic behavior and can be used as a supplementary cementitious material. Nonetheless, the chemical composition, as well as the purity, of waste glass play an important role for the binder and aggregate in the mixture. [ABSTRACT FROM AUTHOR]

Traditionally, residential buildings in Vojvodina have masonry walls. Various types of mortar of mineral origin are most often used for joining masonry elements and finishing. The total amount of mortar for the construction of one building is not negligible. The estimated annual consumption of mortar in Vojvodina is about 198 thousand tons i.e. 27 thousand tons of cement and about 31.5 thousand tons of hydrated lime. It can easily be seen conventional mortars based on cement and lime are unacceptable in the light of environmental protection and sustainable development in the contemporary construction industry. Therefore, there is a need for research and development of new, alternative types of binders, based on locally available renewable and/or waste materials. The ceramic masonry elements and tiles industry generates ceramic waste during the production process. This waste, in powder form, could potentially be used as supplementary cementitious material (SCM). Biomass ash, generated by the combustion of harvest residues, as a renewable energy source, is another alternative to cement in modern building composites. This paper emphasizes the physical, chemical, and pozzolanic characteristics of the available agro-waste ashes and ceramic waste powder, originating from Vojvodina. The results indicate relatively high pozzolanicity of all tested ceramic powders and biomass ash based on cob corn, owing to their high fineness and reactive silica content. Furthermore, a catalogue of collected waste materials, illustrating basic data on the raw materials, processing method, landfilling, available quantities, and their tested properties is given.

Climate change is already an undeniable reality, and it is a direct consequence of our society’s lifestyle and the indiscriminate use of certain materials, such as Portland cement, which causes the emission of gases and waste that contributes to the greenhouse effect. The object of this work is to present the results obtained from research on pyroxenic andesites that have become altered to zeolite and their use as alternative, eco-efficient materials that improve the quality of cement through a standardized partial substitution. In this work, four samples of pyroxenic andesites altered to zeolites (PAAZ) and two samples of unaltered andesites (UPA) were analyzed. The methods used in this study are as follows: petrography of thin section (PTS), chemical analysis of X-ray fluorescence (XRF) and phase determination by X-ray diffraction (XRD). Other tests were carried out to determine the quality of the PAAZ from a technical and practical application point of view, such as chemical analysis of pozzolanicity (CPT) at 8 and 15 days, as well as mechanical compression tests at 2, 7, 28 and 90 days. Petrographic and phase analyses show that the original mineral components of the samples such as pyroxene, amphibole, plagioclase and mica were leached and replaced by more than 90% with mordenite and smectite. XRF analyses indicates an anomalous rise in SiO2, a drastic reduction in alumina Al2O3 and a significant increase in alkaline compounds over alkaline-earth compounds in samples of altered pyroxenic andesites (PAAZ) with respect to samples of unaltered andesites (UPA). The pozzolanicity test establishes that the samples of unaltered andesites do not behave like pozzolans at 8 or 15 days; however, altered andesites experienced remarkable pozzolanic reactivity in the same periods. The mechanical compression tests carried out on specimens made with PAAZ and Portland cement showed a growing increase in mechanical resistance from 2 days (15.2 MPa) to 90 days (72.1 MPa). These results suggest that pyroxenic andesites altered to zeolite can be an ideal alternative to partially replace Portland cement, which in turn could contribute to the preservation of the environment and a more rational use of traditional resources.

The geological nature of the territory of the Republic of Cuba has favoured the formation of large and varied deposits of volcanic tuffs enriched by various species of zeolites. Today, new zeolite deposits continue to be discovered in the country. This work aims to present the results of a study carried out in an unexplored area that is located approximately 1.2 km east of the Loma Blanca deposit, outside the mining operation limits. To carry out this research and to establish a qualitative comparison between both sample populations, four samples were taken from the study area, and another four were taken from the Loma Blanca deposit. The characterisation of the samples was performed by XRD, SEM, and XRF. The pozzolan quality was determined by the pozzolanicity test (PT) and quality chemical analysis (QCA). Finally, a study of the mechanical strength (MST) was performed at 7, 28, and 90 days, using mortar specimens made with PC/ZT: 75–25% and PC/ZT: 70–30%, respectively. The results of the studies using XRD, SEM, and XRF indicated that both groups of samples had a similar complex mineralogical composition, consisting mainly of mordenite and clinoptilolite accompanied by secondary phases such as quartz and amorphous materials in the form of altered glass. The pozzolanicity test showed that both the samples from the study area and those from the Loma Blanca deposit behaved like typical pozzolans, which is a trend that can be seen in the high values of mechanical strength to compression up to 72 MPa for the PC/ZT: 75–25% formulation and 66 MPa for the PC/ZT: 70–30%. The results obtained establish that the zeolite varieties detected in the study area are similar to those of the Loma Blanca deposit, which could have a positive impact on the increase in current reserves, especially for manufacturing pozzolanic cements with properties that contribute to the preservation of the environment. [ABSTRACT FROM AUTHOR]

The utilisation of locally available agro-waste ashes in concrete is a sustainable alternative to carbon-intensive cement production. Although earlier studies have reported the potential of palm oil fuel ash as a pozzolan, its industrial acceptance is highly limited. The present review focuses on a critical comparison of palm oil fuel ash blended concrete with fly ash or slag based blended concretes which are widely accepted. Fresh, hardened and durability characteristics of blended concretes are meticulously compared. The addition of fly ash and palm oil fuel ash enhances the workability of concrete, whereas the addition of slag reduces the workability of concrete. At a replacement level of 60%, POFA blended concrete exhibited an increase in slump value of 21% as compared to the control concrete. All the three pozzolans exhibited lower earlier strength owing to their slower rate of reaction. The optimum replacement levels of palm oil fuel ash, fly ash and slag are 10%, 30% and 40%, respectively. For a constant replacement level (20%), the reduction in the water absorption as compared to the control concrete was 26.5%, 26.73% and 26.2% for POFA, fly ash and slag blended concrete, correspondingly. Chloride penetration and water absorption are lesser for all blended concretes than the control concrete up to their optimum replacement levels.

Ground coal bottom ash is considered a novel material when used in common cement production as a blended cement. This new application must be evaluated by means of the study of its pozzolanic properties. Coal bottom ash, in some countries, is being used as a replacement for natural sand, but in some others, it is disposed of in a landfill, leading thus to environmental problems. The pozzolanic properties of ground coal bottom ash and coal fly ash cements were investigated in order to assess their pozzolanic performance. Proportions of coal fly ash and ground coal bottom ash in the mixes were 100:0, 90:10, 80:20, 50:50, 0:100. Next, multicomponent cements were formulated using 10%, 25% or 35% of ashes. In general, the pozzolanic performance of the ground coal bottom ash is quite similar to that of the coal fly ash. As expected, the pozzolanic reaction of both of them proceeds slowly at early ages, but the reaction rate increases over time. Ground coal bottom ash is a promising novel material with pozzolanic properties which are comparable to that of coal fly ashes. Then, coal bottom ash subjected to an adequate mechanical grinding is suitable to be used to produce common coal-ash cements.

Presently, the search for urgent solutions to mitigate climate change has become a global priority. One of the most important challenges is the characterization, standardization, and technology of sustainable natural raw materials, which will significantly improve the quality of common types of cement, the production process of which emits large amounts of greenhouse gases into the atmosphere. This work is focused on the study of natural kaolinitic clays (NKC) from the eastern part of the Iberian Peninsula and its main objective is to define and normalize their properties as natural pozzolanic materials. This research consists of an initial study to determine the morphological and chemical properties using SEM and XRF. Furthermore, the physical properties of the samples were studied, such as thermic treatment (TT), Blane particle finesse (BPF), real density (RD) and apparent density (AD), porosity (P), volume stability (VS) and start and final setting time (SFST). On the other hand, technological analyses were carried out as follows: chemical analysis (CATQ), pozzolanicity (CAP), mechanical compression strength tests at 7, 28, and 90 days (MCST) as well as the ultrasonic pulse velocity (UPV). XRF results indicated that the SiO2 content (49.9–51.0%) of kaolinitic clay in its natural state (NKC) increases to 57.41 and 58.10%, respectively, when calcined (CKC). The chemical analysis of pozzolanicity established that the NKC does not show pozzolanic activity during the first 8 and 15 days; however, once calcinated, its pozzolanic reactivity increases substantially. On the other hand, the results of the mechanical stress tests (MCST) indicate an exponential increase in mechanical resistance from 7 to 90 days, which is higher in mortars made with CKC; similarly, and according to the results of the calculation of the Resistant Activity Index (RAI), it shows that the substitutions of Portland cement (PC) by NKC are effective between the ranges of 10 and 25%, while in the case of the substitution of PC by CKC, all formulations (10, 25 and 40%) are effective. This research establishes that the kaolinitic clays of the east of the Iberian Peninsula can be considered quality pozzolanic materials, capable of partially replacing Portland cement. The results presented here could be used as guidelines for the understanding and application of natural pozzolanic materials contributing to the improvement of types of cement, mortars, and concretes, which would positively affect the quality and preservation of the environment as well as the sustainability of eco-efficient construction materials.

Two sources of natural scoria rocks were procured and ground for use in concrete as natural pozzolans (NP1 and NP2). The evaluation of their pozzolanic reactivity is carried out using different techniques and approaches. The primary goal of employing these techniques is to monitor the amount of portlandite (CH=Ca(OH)2) consumed during steam curing at low or high pressure. The pozzolanicity of NP powders is determined either directly by monitoring CH variation or indirectly by compressive strength and microstructure development. Autoclave curing is known to stimulate the pozzolanicity of the inert siliceous and aluminosiliceous materials under its high-pressure steam conditions. Both steam-curing conditions were applied in this investigation. In this study, X-ray diffraction, scanning electron microscope, thermogravimetric, Fourier transform infrared, and isothermal analyzers were used. It is concluded that the nature and types of minerals in SR determine their pozzolanic reactivity as either low-pressure steam-reactive or high-pressure steam-reactive cementitious materials. Due to the nature of their silicate structures, notably single-chain or 3D-framework structures, plagioclase feldspars (albite-anorthite) minerals are high-pressure steam-reactive minerals, whereas pyroxene (enstatite and diopside) minerals are low-pressure steam-reactive minerals. Using high-pressure steam curing, varied replacement levels of up to 60% were achieved in NP1, with a consistent strength activity index (SAI) of 99%, while an SAI of 79% was obtained with NP2. During low-pressure steam curing, NP1 and NP2 consumed around 72 and 80% of portlandite, respectively, demonstrating their relative pozzolanic reactivity. When compared to the control concrete mix, the strength activity indices of NP1, NP2, and class F fly ash in their normal concrete mixes reached 74.3, 82, and 73.7%, respectively, after 56 days of normal curing conditions. [ABSTRACT FROM AUTHOR]

Abstract The use of supplementary cementitious materials (SMCs) is one of the three essential factors for the sustainability of the cement industry. To reduce CO2 emissions, several studies have introduced new methods for the utilization of industrial wastes such as the addition into cementitious materials. The objectives of this study were to chemically and physically characterize refractory ceramic industry waste and determine its viability as an SMC. The pozzolanic characteristics or SMC characteristics of the refractory waste were investigated using standard tests. The results revealed that the refractory waste was mainly composed of Al2O3 and SiO2. The mineralogical analysis revealed that the mullite was the major phase of the waste, followed by small amounts of cristobalite and quartz phases. The results of the modified Chapelle test and pozzolanic activity index with lime after 7 days indicated that the waste did not meet the minimum pozzolanicity required by the standard. However, the waste improved the mechanical resistance of the cement specimens containing the waste after 28 days compared with the reference sample, indicating the promising potential of the material for this application. This result indicated that the refractory waste shows a filler type effect, and thus, can be employed as an SCM.

An estimated 2100 tonnes of solid sludge is generated per annum from the water-based paint industries of Bangladesh. This paint sludge (PS) is usually incinerated, consuming energy and generating greenhouse gases and other pollutants. Through chemical analysis and standardized tests, it was shown that PS contains a similar array of oxides as Ordinary Portland Cement (OPC) and has pozzolanic characteristics. Considering these, PS was examined as a cement replacement material to create an alternative and economically beneficial way of disposing of this waste. Cement paste and mortar samples were prepared by replacing 5%, 10%, 15%, 20% and 30% of OPC with PS. To assess mechanical and durability properties of PS-incorporated samples, different tests were carried out that included consistency, setting time, compressive strength, soundness, sulfate attack, alkali silicate reactivity and chloride diffusion. Both initial and final setting times of PS-incorporated cement increased with an increase in PS fraction but remained within the standard limit. Compressive strength increased for 5% PS replacement but decreased with further increase in PS replacement compared to 100% OPC mortar. A slightly higher rate of compressive strength gain was observed at later ages for PS-incorporated cement than 100% OPC, which confirmed the pozzolanic characteristic of PS. The addition of PS was found to reduce the expansion of mortar bars in both soundness and ASR tests. It also inhibited ettringite crystal formation in the mortar matrix for sulfate exposure. Initially, chloride permeability increased in the early days for PS-incorporated mortar but was found to decrease rapidly at later ages. Altogether, it may be concluded that a 15% replacement of OPC with PS would comply with the necessary strength and durability standards.

Portland cement production is an energy-intensive process that releases carbon dioxide into the atmosphere. To reach carbon neutrality by 2050, it would be necessary to implement innovative measures in the cement industry to deliver carbon neutrality. In this respect, it is striking that the new cement types made with high contents of industrial by-products will act as a lever to combat climate change. Accordingly, the purpose of this study is to assess coal–ash blended cements in light of climate change mitigation. In particular, ground coal bottom ash could be considered as a novel constituent for common cement production. The performance of these coal–ash mortars was assessed by measuring pozzolanic reactivity, mechanical strength gain, and microstructural characteristics. Mortars were made with 10%, 25%, or 35% of coal ash (fly ash and/or bottom ash). Therefore, by considering an emission intensity factor of 830 kgCO2/kg of clinker, a reduction in carbon dioxide emissions for all coal fly ash cements is expected, which will be about 83 kgCO2/kg of cement, 208 kgCO2/kg of cement, and 290 kgCO2/kg of cement, respectively. Ground coal bottom ash presented similar characteristics to the coal fly ash. Consequently, ground coal bottom ash is a promising Portland cement constituent with properties comparable to coal fly ash, and its increased usage can contribute to the climate change mitigation. [ABSTRACT FROM AUTHOR]

The effect of using calcined bentonite (CB) as a partial replacement for Ordinary Portland cement (OPC) in self-compacting mortar (SCM) is investigated. The pozzolanicity of this calcined clay is evaluated using the strength activity index and TG/ATD analysis. The cement in SCM has been replaced with CB at 0, 5, 10, 15, 20, 25 and 30% by mass of cement. The effect of CB on fresh SCM properties is examined using mini-slump flow and V-funnel flow time. The compressive strength is determined at the age of 3, 7 and 28 days, and the ultrasonic pulse velocity (UPV), hardened density and water absorption are determined at the age of 28 days. The behaviour of SCM exposed to high temperature is also studied. The results indicate that CB significantly decreased the flowability of SCM, but these results are good enough for SCM and SCC production. Incorporating 10 and 15% of CB improves the compressive strength and UPV. Water absorption tends to increase slightly with an increase in CB content and there is a decrease in density as the amount of CB increases. SCM containing CB is stronger when exposed to high temperature than those exposed to normal temperature (23 °C). [ABSTRACT FROM AUTHOR]

This paper reports on the possible use of sewage sludge ash as a pozzolanic supplementary cementitious material to Portland cement. Samples of sewage sludge were incinerated at 700°C, 800°C and 900°C and these were then cooled in the furnace (FISSA), in air (AISSA) or by quenching in water. The resulting ashes were ground to suitable fineness and used to prepare cement pastes and mortars in which the binder consisted of 30% ash and 70% Portland cement. The paste samples were used for microscopic and chemical assessment of the evolution of hydration products, while the mortars were used to assess the effects of the ashes on workability and compressive strength of laboratory-prepared samples using a water/binder ratio of 0.5. Fly ash was used as a reference pozzolanic material to assess the performance of sewage sludge ashes. Analysis of the sewage sludge ashes showed the presence of cementitious compounds and hydration products that suggest that this material can be used as a partial replacement of Portland cement. However, sewage sludge ash reduces the workability of the mortar. Compressive strength results indicate that the highest strength is obtained when the sewage sludge is incinerated at 900°C and then quenched in water. [ABSTRACT FROM AUTHOR]

Seventeen pozzolan samples from Tombel Plain, Bamileke Plateau and Noun Plain within the Cameroon Volcanic Line (CVL) were analysed in order to determine their ability to partially replace clinker in blended cement manufacture. Electrical conductivity (ΔEc) ranges from 0.26 to 3.83 mS/cm, SiO2 + Al2O3 + Fe2O3T (SAF) from 69.58 to 81.01% and loss on ignition (LOI) from − 0.73 to + 7.21%. Except for sample TMC18 (ΔEc < 0.4 mS/cm), others show good pozzolanicity. Microdeval (MD = 24.2–93.2%) and water gassing (ωG = 25.20–28.80%) indicate high-grinding ability and good consistency respectively. The obtained pozzolanic cements display longer setting time (149–256 > 143 mn) than Portland cement, highlighting pozzolan's contributions to mortar's workability. Only sample ML37 reaches the target of 32.5 MPa whereas others show low (26.4–32.1 MPa) compressive strengths after 28 days (Rc 28d). Strength activity index (SAI = 55.0–68.33%) are low. Samples with SAI > 60% while using 40% highlight the contribution of pozzolans to strengths. Increasing strength gain (SG) with curing time indicates high-activity of pozzolans. These pozzolanic cements show lower durability gain index (DGI = − 7.21 to − 2.68 < 0) than Portland. A part from sample TDJ16 (DGI = − 2.91), other good (Lim52, Lim53, TDJ16, TMC18, BL32, FM42, MB46, MB47) to excellent (N35, ML37, TMjo19) pozzolans in term of strength, display poor durability. Based on standard ASTM C 618 (2015), SAF used till now to make assumption on the quality of pozzolans seem to be less reliable than CIM (CaO + FeO + MgO); instead of decreasing with SAF (R2 = 0.24), compressive strength (Rc28d) increases with CIM (R2 = 0.31). [ABSTRACT FROM AUTHOR]

This paper investigates the potential application of red ceramic waste as supplementary cementitious materials in structural concrete as a strategy to implement a circular economy in the Brazilian construction industry from a sustainable infrastructure perspective. The experimental program comprehends the waste characterization and application in concrete mixtures produced with different w/b (0.35, 0.45, and 0.55) and Portland cement replacement (5%, 10%, 20%, and 40%). Eco-efficiency intensity indicators considering cement consumption, carbon dioxide emission, and embodied energy complement the structural concrete assessment. Concrete mixtures with up to 40% of waste, combined with w/b 0.35 and 0.45, did not compromise the concrete structural performance regarding compressive strength. The relatively low water absorption in concrete mixtures produced with up to 40% Portland replacement by red ceramic waste suggests concrete ability to restrain water and vapor ingress on a satisfactory level. Structural concrete with Portland cement replacement by 20% or 40% of waste showed better performance from the eco-efficiency perspective. Structural concrete with Portland cement replacement by 20% or 40% of waste can preserve mechanical properties, reduce carbon dioxide release, and implement a circular economy in the construction industry. [ABSTRACT FROM AUTHOR]

Ground coal bottom ash is considered a novel material when used in common cement production as a blended cement. This new application must be evaluated by means of the study of its pozzolanic properties. Coal bottom ash, in some countries, is being used as a replacement for natural sand, but in some others, it is disposed of in a landfill, leading thus to environmental problems. The pozzolanic properties of ground coal bottom ash and coal fly ash cements were investigated in order to assess their pozzolanic performance. Proportions of coal fly ash and ground coal bottom ash in the mixes were 100:0, 90:10, 80:20, 50:50, 0:100. Next, multicomponent cements were formulated using 10%, 25% or 35% of ashes. In general, the pozzolanic performance of the ground coal bottom ash is quite similar to that of the coal fly ash. As expected, the pozzolanic reaction of both of them proceeds slowly at early ages, but the reaction rate increases over time. Ground coal bottom ash is a promising novel material with pozzolanic properties which are comparable to that of coal fly ashes. Then, coal bottom ash subjected to an adequate mechanical grinding is suitable to be used to produce common coal-ash cements. [ABSTRACT FROM AUTHOR]

Statement of Novelty: This study analyzes the influence of the washing process and the calcination temperature on the morphological, physical, chemical and mineralogical characteristics of SCBA. The objective of the present study is to evaluate the morphological, physical, chemical and mineralogical characteristics of sugar cane bagasse ash (SCBA). The ashes were obtained by calcination of sugarcane bagasse (SCB), a waste product generated by the sugar and alcohol industry, at temperatures of 500°C, 600° C and 700°C, and the influence of this calcination on the pozzolanic activity of SCBA. The techniques used to characterize these ashes include helium gas picnometry, sedigraphy, scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-ray diffractometry (XRD) and Fourier transform infrared spectrometry (FTIR). The evaluation of the pozzolanicity of these ashes was carried according to chemical titration method as proposed by Fratini, modified Chapelle method and finally using the pozzolanic activity index (PAI) with cement. The results showed that the SCBA presented high pozzolanicity, regardless of the calcination temperature. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the cause of the self-cementing properties of recycled aggregates used for pavement base. Clay bricks were added to the recycled aggregates to study the pozzolanic reactions. The evolution of the mechanical performances of the materials was investigated in the laboratory (California Bearing Ratio) and in the field (plate test). Both tests showed that initially, the mechanical performances of recycled aggregates are equivalent or even lower than those of natural aggregates. However, recycled aggregates become much better than natural aggregates with time. Therefore, setting tests, microcalorimetric analysis, and two pozzolanicity tests (pH evolution and consumption of Ca2+ ions) were carried out in a laboratory in order to explain the observations made on the test beds. The microcalorimetric analysis showed that there is only a slight hydraulicity due to residual anhydrous cement content in recycled aggregates. However, the other tests highlight that the presence of clay bricks particles in recycled aggregates results in pozzolanic reactions that can explain the time-evolution of mechanical performances. This study suggests that recycled aggregates have a high added value when they are used as pavement base. [ABSTRACT FROM AUTHOR]

abstract: Alkali-silica reaction (ASR) is one of the most harmful distress mechanisms that affects the durability of concrete worldwide. Yet, it has been found that ASR-induced expansion and distress may be prevented by the appropriate use of supplementary cementing materials (SCMs). Recent studies suggest that rice husk ash (RHA), a by-product of the rice production, may present promising performances as a pozzolanic material and to enhance the durability of blended mixtures. There are many controversial studies regarding the use of RHA and how its properties directly affect the performance and durability of concretes and mortars. The present study aims to evaluate the influence of the RHA on ASR through the accelerated mortar bar test (AMBT), X-Rays Diffraction (XRD), Thermogravimetric Analysis (TG), Mercury Intrusion Porosimetry (MIP) and Scanning Electron Microscopy (SEM). To validate the obtained data, the results were compared with mortars made of a well-known SCM (silica fume) which has distinguished behaviour against ASR. The results indicate that, besides the silica fume mortars have showed better results, the use of RHA suggests promising results to mitigate the ASR, yet, further analysis on concrete prims test should be carried out to fully validate the use of RHA to enhance the durability of the concrete. The RHA finesses and its particle size were the most important properties in the SCM performance.

The use of supplementary cementitious materials (SMCs) is one of the three essential factors for the sustainability of the cement industry. To reduce CO2 emissions, several studies have introduced new methods for the utilization of industrial wastes such as the addition into cementitious materials. The objectives of this study were to chemically and physically characterize refractory ceramic industry waste and determine its viability as an SMC. The pozzolanic characteristics or SMC characteristics of the refractory waste were investigated using standard tests. The results revealed that the refractory waste was mainly composed of Al2O3 and SiO2 . The mineralogical analysis revealed that the mullite was the major phase of the waste, followed by small amounts of cristobalite and quartz phases. The results of the modified Chapelle test and pozzolanic activity index with lime after 7 days indicated that the waste did not meet the minimum pozzolanicity required by the standard. However, the waste improved the mechanical resistance of the cement specimens containing the waste after 28 days compared with the reference sample, indicating the promising potential of the material for this application. This result indicated that the refractory waste shows a filler type effect, and thus, can be employed as an SCM. [ABSTRACT FROM AUTHOR]

Nowadays, the preservation of natural resources, the reuse, and the recycling of waste and by-products in the cement industry are gaining increasing attention in a sustainable development project. In this perspective, many studies focus on finding solutions in order to propose environmentally friendly materials. Nowadays the sediments represent a way to preserve the natural resources by their reuse as a secondary raw material in multiple applications (concrete, roads, landscaped mound, etc.). However, they commonly contain contaminants, organic matter (5%–30%), high water content (50%–200%), and relatively small particle size (Dmax ≤ 300 μm). Therefore to improve the mechanical properties of this material as well as its physiochemical ones, specific methods of characterization and appropriate treatment techniques (calcination, chemical treatment, etc.) are required. This article presents a bibliographical review of the efficient use of sediments in cementitious matrix. It details experimental tests that must be performed to ensure the durability of sediment-based structure and assess their environmental impact under prescribed conditions. [ABSTRACT FROM AUTHOR]

Pozzolans from the Tombel Plain, Bamileke Plateau, and Noun Plain, 3 monogenetic volcanic fields in the central part of the Cameroon Volcanic Line (the Tombel Plain, Bamileke Plateau, and Noun Plain), were explored in order to constrain their petrology and make some predictions on their pozzolanicity. The rocks in this study include alkaline and subalkaline basalts, trachy-basalts, and basanites. Most of these rocks present an overall composition that overlaps with primitive mantle, suggesting rapid ascent of magmas, limited crustal contamination and crystal fractionation of olivine, clinopyroxene, and feldspar. The pozzolans present enrichment of LREE relative to HREE and high chondrite normalized ratios of La/Yb and Tb/Yb, ranging between 7 and 20 and > 1.9 respectively, similar to those of Ocean Island Basalts. Like other nearby volcanoes, partial melting in a dominantly garnet-bearing mantle zone can be assumed. Quantitative mineralogy by X-ray diffraction revealed various mineral phases with dominantly plagioclase, augite, olivine, and Fe–Ti oxides. The samples contains important amorphous phase up to 23, 51, and 69 wt% in the Tombel Plain, Noun Plain, and Bamileke Plateau, respectively. This elevated amount of amorphous phases together with the sum of SiO2, Al2O3, and total Fe2O3 (SAI = 68.50–83.50 > 70 wt%) according to ASTM C 618 standard and the sum of CaO, FeO, and MgO (CIM = 14.5–30.52 wt% and 23.58–31.08 wt%) suggest interesting pozzolanicity character for the studied pozzolans. [ABSTRACT FROM AUTHOR]

The present paper focuses on the suitability, variability and versatility of thermal analysis and calorimetry methods in the study of cement hydration as physical and chemical process including pozzolanicity and hydraulicity of supplementary cementitious materials. Isothermal calorimeter TAM AIR and simultaneous TGA/DSC were used. Not only activation energy of system comprising SCMs, but also heat generated through alkali-activated reaction of metakaolin and ground granulated blast furnace slag (BFS) can be successfully determined by using conduction calorimetry. The incremental heat flow and incremental cumulative heat of the alkali-activated reaction of ground granulated BFS and metakaolin (MK) were determined and found dependent on temperature and mass ratio between cement and SCMs. The incremental heat flow presents the same characteristics as parent heat flow with different peaks, denoting the formation of C–S–H, ettringite and C–A–S–H trough alkali-activated reaction. While BFS and MK influenced moderately the formation of C–S–H, their influence on the formation of C–A– S ¯ –H (ettringite and monosulphate) and C–A–S–H is significant as evidenced by peak position and intensity. The method of calorimetry coupled with thermal analysis was considered sufficient to assess the pozzolanicity and hydraulicity of SCMs. [ABSTRACT FROM AUTHOR]

This work presents the results of the study of the physical, chemical, mineralogical and pozzolanic properties of the altered volcanic tuffs (AVT) that lie in the Los Frailes caldera, south of the Iberian Peninsula, and demonstrates their qualities as pozzolans for the manufacturing of mortars and pozzolanic cements of high mechanical strength. The main objective of this research is to show to what extent the AVTs can replace portland cement (PC) in mortars, with standardised proportions of 75:25% and 70:30% (PC-AVT). To achieve these objectives, three AVT samples were studied by a petrographic analysis of thin section (PATS), DRX, FRX and MEB. The pozzolanic properties were determined by three methods: electrical conductivity (ECT), chemical pozzolanicity tests (CPT) at 8 and 15 days and mechanical strength tests (MS) of the specimens at 2, 7, 28 and 90 days. Studies of a PATS, DRX, FRX and MEB showed that the AVT samples’ constitutions are complex where smectite (montmorillonite), mordenite, quartz, halloysite, illite, kaolinite, volcanic glass and lithic fragments coexist. The results of the ECT and CPT tests confirmed the pozzolanic properties of the samples analysed and proved an increase in mechanical strength from 2 to 90 days of testing.

Biomass ash results from the combustion of agricultural residues, which, in many developing countries, are a primary source of power generation for small and medium size industries. This study focuses on the performance of a binder synthesized from an Indian biomass ash, Indo-Gangetic clay, hydrated lime, and aqueous 1M NaOH solution. To measure the extent of leaching and its impact on physicochemical properties, the biomass ash binder in powder form (<45 μm size) was exposed to two different leaching media: deionized water and 0.1M HNO 3 at two different solution-to-sample ratios (by wt.) of 10 and 100. Sodium leaching was found to be prominent in the biomass ash binder irrespective of leaching medium and solution-to-sample ratio. However, calcium leaching was significantly higher in 0.1M HNO 3 than in deionized water. Calcium silicate hydrate present in the biomass ash binder was found to be less chemically stable in 0.1M HNO 3 , exhibiting complete calcium leaching at a solution-to-sample ratio of 100. Furthermore, significant leaching of calcium in 0.1M HNO 3 solution resulted in phase modification of calcium silicate hydrate, the main reaction product of the biomass ash binder. [ABSTRACT FROM AUTHOR]

The reactivity of fly ash can vary considerably when used as a supplementary cementitious material (SCM). This paper demonstrates a framework for a standard test method to quantify the maximum reactivity of fly ash. The test is based on mixing reagent-grade calcium hydroxide (CH) and fly ash in a 3:1 mass ratio and exposing the mixture to 0.5 M potassium hydroxide (KOH) solution. Isothermal calorimetry and thermogravimetric analysis (TGA) are used to measure heat release and CH consumption, respectively, which are done in conjunction with thermodynamic calculations, as a basis to characterize the maximum reactivity of the fly ash. Fifteen fly ashes were tested using the method, which revealed that the reactivities ranged from 33 to 75%. Thermodynamic modeling was used to demonstrate the effect of fly ash reactivity on the properties of blended OPC-fly ash mixtures with different fly ash replacement levels (0 to 80%) and at various reactivities (0 to 100%). It was shown that the reactivity of fly ash is a critical factor determining durability-related parameters of mixtures such as CH content, C-S-H type and content, and the pH of the pore solution. [ABSTRACT FROM AUTHOR]

Highlights • Pozzolanic test was used to develop two measures for SCM degree of reaction. • Degree of reaction increases as temperature increases but does not depend on w/cm. • Values generally agree with those from literature. • Preliminary results are promising. Abstract A pozzolanic test that can correctly identify pozzolanic materials is key in the search for alternative supplementary cementitious material (SCMs). Determination of the degree of reaction of these alternative SCMs in cementitious pastes is also important, as the reactivity of certain SCMs can be quite low. Since typical methods to determine SCM degree of reaction can be complex and laborious, the current study explores whether parameters obtained from a newly developed pozzolanic test can potentially be used to develop a simple method for determining the degree of reaction of SCMs. In the pozzolanic test, (cumulative) heat release and calcium hydroxide consumption of SCMs from a mixture of SCM and calcium hydroxide (water-to-solids ratio 0.9, pH 13.5, and testing temperature of 50 °C) are measured. Corresponding values of cumulative heat release and calcium hydroxide consumption of SCMs in a cementitious paste are also measured at two different water-cementitious materials (w/cm) ratios. The ratio between the values of cumulative heat release and the calcium hydroxide consumption in the cementitious paste and the pozzolanic test are considered to be measures of degree of reaction. Four different SCMs – class F fly ash, ground granulated blast furnace slag, metakaolin, and undensified silica fume were tested in this study. The effect of temperature and w/cm on degree of reaction were assessed. Degree of reaction values obtained from this method were compared with those from obtained from a portlandite consumption method suggested in literature and from typical values suggested in literature. Good correlation (R2 = 0.87) is obtained for the degree of reaction values determined here using the calcium hydroxide ratio and the portlandite consumption method. The degree of reaction values increase as the temperature increases but do not strongly depend on w/cm. The degree of reaction values are in general agreement with the range of values obtained from literature, however, this range is rather large, and the values depend strongly on the method used to determine degree of reaction. These preliminary results are promising and suggest that this method may potentially be used to provide information about pozzolanicity and degree of reaction of various SCMs. [ABSTRACT FROM AUTHOR]