Natural Pozzolan Research Articles

Effect of Calcination on the Ash from Lokon Volcano and Its Potentially Sustainable Binder Material

The need for cement as a housing construction material has continued to increase due to the growing population. This high demand increases carbon dioxide emissions. Hence, it is necessary to optimize the use of natural pozzolan material. Volcanic ash is a natural pozzolan material in North Sulawesi, but its use could be more optimal. This study aimed to determine the effect of calcination on the physical properties of volcanic ash originating from the eruption of Mount Lokon. The calcination was carried out to determine the potential of Lokon ash at different temperatures to assess the structural characteristics, mineral phases, metal oxide composition, functional group bonding, morphology, and its potential as a binder for concrete mixtures. The ash material used comes from sand taken from the Pasahapen River and filtered through a 325-mesh sieve. Lokon ash was calcined at temperatures of 800, 900, and 1000oC to determine the structural and morphological characteristics. At the same time, the effects were examined using an X-ray diffractometer (XRD), Raman spectroscopy, X-ray fluorescence (XRF), Fourier Transform InfraRed (FTIR), and Scanning Electron Microscopy (SEM). The results showed that calcination triggered the formation of hematite in the ash, which will increase its reactivity as a pozzolan material. This process causes the crystallinity of ash minerals to increase, but the ash material produced is predominantly amorphous. Hence, it has excellent potential as a binder material in concrete mixtures.

Natural pozzolana as standalone photocatalyst for water treatment

This study focuses on natural pozzolana (volcanic ash) as standalone photocatalyst for removal of organic water pollutants under solar irradiation. Natural pozzolana has been modified and investigated using various techniques (XRD, EDS, FTIR, TGA, and BET surface area). The investigated pozzolana material has worked as metal oxide heterojunctions with SiO2 (35.45 %), Al2O3 (12.56 %), Fe2O3 (14.15 %) and CaO (7.89 %) in a majority, besides other oxides (MgO (5.75 %), TiO2 (3.25 %), Na2O (2.15 %), K2O (1.23 %), and MnO (0.34 %)). The XRD results showed that pozzolana materials contains different crystalline forms such as Albite, Quartz, Biotite, Hematite and Magnesio hornblende. The performance of the prepared pozzolan material has been evaluated for photocatalytic degradation of BPB dye as model water pollutant and the photocatalytic activity was related to the characterization results. It was shown that the sieved pozzolana material (Ps) has the highest photocatalytic degradation rate (0.0175 min−1) compared to raw (P0) and calcined (Pc) samples. The photocatalytic activity of Ps was also higher than that of TiO2 anatase (0.0121 min−1) used under the same experimental conditions, which was attributed to the diversity of pozzolana compositions from various oxides, with a cascade transference of charge carriers leading to effective charge separation and transfer, hence enhancing the photocatalytic activity. Based on this, natural pozzolan could be used as cost effective and green material for sustainable photocatalytic applications.

Effect of harsh environment on cement mortar containing natural pozzolans

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

Dolomitic Limestone Powder: Cement Substitute in the Production of Structural Concrete Paving Blocks

Manufacturers are replacing or combining cement with mineral additives such as slags, natural pozzolans, sand, diatomaceous earth and limestone to reduce carbon dioxide emissions and energy usage. Due to its high magnesium content, dolomitic limestone has long been utilized in concrete production to reduce costs and environmental risks associated with making cement. This study aimed to produce a reliable and appropriate concrete mixture for concrete paving blocks using dolomitic limestone powder that passed the no. 24 sieve as cement replacement at replacement levels of 0 (control mix), 8, 12, 16, 20, 24, 28 and 32%, satisfying the minimum compressive strength requirement for structural concrete of 20.7 MPa (3,000 psi). The ASTM E877-13 was used to sample the dolomitic limestone, and the 1:1.5:3 concrete class combination was utilized to proportion the quantities of cement, sand and aggregates (3/8”). After 28 days, the specimens were cured and the compressive strength, through the varying water-cement ratios in the concrete mixture, was determined. Results showed that dolomitic limestone powder can substitute cement by 16% by weight, using a concrete mix of 523-g cement, 936-g sand, 1,868-g gravel, 100-g dolomitic limestone powder, and 166-g water with a water-cement ratio of 0.318, exceeding the minimum necessary compressive strength of concrete of 20.7 MPa by 24.9% or 5.16 MPa. Therefore, it is advised to utilize this proven concrete mixture as a basis for a potential business venture in the production of concrete paving blocks for structural concrete applications such as walkways, sidewalks, parking lots and commercial areas, as well as in places where loads are very high, like airports, courtyards, docks and freight yards.

Performance of brick masonry prisms retrofitted with fiber reinforced lime-based grouts

Lime-based grouts have been widely used for the consolidation of historic masonries, whereas additives of various origin and proportion are used to enhance their properties at fresh and hardened state. Testing their efficiency includes analysis of their fresh and physico-mechanical properties, as well as experimental assessment of their applicability in masonry prisms and wallettes. In the present study, four grout compositions based on hydrated lime and natural pozzolan, including 0.1% v/v glass and polypropylene fibers, were manufactured and tested. They were injected in brick masonry prisms which were previously partially loaded to compression. Macroscopic observations and measurements of pulse velocity and compressive strength were performed prior and after grouting, in order to investigate the prisms behavior and the efficacy of the fiber reinforced lime-pozzolan grouts. According to the results, fibers maintained the grouts fresh properties, improving volume stability (shrinkage deformations were decreased) and long-term mechanical characteristics. The masonry prisms showed a pulse velocity increase after grouting, while compressive strength was also enhanced, especially in the case of 3 mm glass fibers addition. Generally, it was asserted that the application of fiber reinforced lime-based grouts could be feasible in the case of historic masonries restoration, rendering their study a well promising field.

Production of environmentally-friendly, high-strength repair mortar for the restoration of historical buildings

In this study, repair mortars with artificial and natural pozzolan additives were produced for the restoration of historical buildings. Class C fly ash, an artificial pozzolan and zeolite the natural pozzolan, were substituted into these lime-based mortars. Two different aggregate types were used in the preparation of the mortars: natural river sand and crushed brick. A total of 18 batches of mortars were produced, two of which were reference batches. In the first group of batches, fly ash, which is the major pozzolan, was tested in both aggregate groups in 20%, 40%, and 60% ratios of lime substitution. In the second group of batches, fly ash and zeolite were used in different proportions as lime substitution. In the reference series, air lime was used alone. At the end of the 28, 56, and 90 days curing period, mechanical, physical properties, and phase composition of the mortars were determined. When the pozzolan-added mortars were compared with the reference mortars, it was observed that pozzolans provided significant improvements in the physical and mechanical properties of the repair mortars. While significant improvements were observed in the physical properties of the mortars where fly ash was used as the only pozzolan, mechanical properties were better in the mortars with zeolite.

The selection of an appropriate concrete mixture for casting a pile cap in hot weather using 3D finite element model

In this study, the finite element model (FEM) was developed to select an appropriate concrete mixture for a large heavily reinforced bridge pile cap located in Qassim region of Saudi Arabia. The pile cap with dimensions of 9 m x 9 m in plan and 1.8 m in depth was exposed to hot weather conditions in summer season. The heat of hydration in mass concrete results in high temperature gradients across the depth of the concrete creating excessive thermal stresses resulting in micro-cracking at the surface. The concrete mixtures with 30% date kernels ash, 30% fly ash, 30% natural pozzolan, 30% limestone powder, 30% ground granulated slag and 60% ground granulated slag were investigated. The experimental investigations were conducted on the concrete mixtures to determine the mechanical properties, such as tensile and compressive strength, thermal properties, such as thermal conductivity, specific heat, and thermal resistivity, and heat of hydration. The chemical compositions of ordinary Portland cement, date kernels ash, fly ash, natural pozzolan, limestone powder and ground granulated slag were analyzed using wavelength dispersive X-ray fluorescence (WDXRF). Based on the experimental and finite element model results, the concrete mixtures with 30% fly ash (FA), 30% ground granulated blast furnace slag (GGBFS), and 60% GGBFS were found to be less prone to cracking. Notably, the mixture with 60% GGBFS demonstrated the lowest likelihood of cracking, leading to its selection for casting the pile cap.

Opportunities and barriers of pozzolanic cements

AbstractNatural pozzolans have been used as building materials since ancient times. They are used as a supplementary cementitious material in combination with portland clinker to produce cements, characterized by high mechanical strengths and good durability performance. In the past the production of pozzolanic cement was mostly restricted to countries with natural pozzolan availability (Italy, Turkey, Greece, Philippine for example) and considered or even rejected in other countries that had the possibility of using other types of SCMs such as slag or fly‐ash. The market acceptance of natural pozzolanic cement also shows regional dependency. Colour and water demand strongly affect the perception and rheological properties of concrete containing natural pozzolan resulting in poor acceptancy in regions not used to working with this type of cement. Although, this SCM has been studied for very long time, today it makes sense to look closely at new pozzolanic binders. Innovative types of pozzolanic cement with very low clinker content are approaching the traditional cement market, due to the need for clinker factor reduction, and to the availability of separate grinding technology. New applications are being investigated with the aim of exploiting the behaviour of certain pozzolanic material to act as CO2 adsorbers for the removal of the exhaust gas during the production process. This paper will provide an overview of the most recent research work dealing with natural pozzolanic cement and the possible future opportunities and barriers offered by this very traditional and long‐used building material.

Non-traditional aluminosilicate based alkali-activated mortars - statistical optimization of solution parameters and processing conditions for optimal compressive strength, workability and setting time

The recent shortage of traditional fly ash and slag, commonly used precursors in alkali-activated binders, prompted a rigorous search for alternative materials. This study evaluated four groups of currently underused supplementary cementitious materials (SCMs) as precursors for producing alkali-activated mortars. The materials evaluated include three calcined clays, three ground bottom ashes, three volcanic ashes, and two fluidized bed combustion ashes, collectively named non-traditional and natural pozzolans (NNPs). Firstly, the compositions of the NNPs were optimized using trial-and-error methods to minimize the concentration of the activating solution. Then, the two solution parameters i.e., silica modulus and Na2O% were optimized for compressive strength using a central composite design. The compressive strength (ASTM C109), the workability (ASTM C1437), and the setting time (ASTM C191) of the mortar were determined. The results show that all 11 materials could produce mortar mixtures with compressive strength in the 20–40 MPa range at 28 days, satisfactory workability of at least 50 % (flow value), and at least 30 min of initial setting time without heat curing and without blending with conventional SCMs. Most of the materials were activated with lower solution parameters than those used in the literature. The binder optimization suggested Si/Al range 1.0–3.0 and a minimum Ca/Al of 0.25 as favorable molar ratios for potentially reactive aluminosilicate precursors. Multiple linear regression models validated by higher R2 and minimum RMSE and MAE could accurately predict the compressive strength of NNP mortar. Furthermore, calcium hydroxide and shrinkage-reducing admixtures were identified as set regulators in alkali-activated NNP mortars.

Effects of fineness and content of pozzolan on mechanical property, microstructure, and early-age chemical shrinkage of cement-based material

Natural pozzolan is a promising supplementary cementitious material for hydraulic concrete due to the pozzolanic effect, especially in the area where fly ash is scarce. In this paper, the physical properties of pozzolan were evaluated. The effects of pozzolan fineness and content on the microstructure, compressive strength, and early-age chemical shrinkage of pozzolan blended cement pastes were investigated. The results showed that the addition of pozzolan decreased the compressive strength of hardened cement pastes. The pozzolanic reactivity was closely related to the fineness of pozzolan, and higher pozzolan content led to lower strength. X-ray diffraction (XRD) and thermogravimetric (TG) analysis proved that Ca(OH)2 was consumed by reacting pozzolan, forming new calcium silicate hydrated (C-S-H). Besides, the addition of pozzolan caused the increase in porosity, which was reflected by the increase in macro-pores content. The chemical shrinkage of cement pastes was mainly determined by the hydration rate of cement, so the early-age chemical shrinkage was notably reduced after adding pozzolan due to its lower reactivity than cement clinker. In addition, finer pozzolan particles resulted in less macro-defects in the cement matrix, which enhanced the deformation resistance of hardened cement paste, and thus the chemical shrinkage was also decreased.

Effects of FeNi3 Nanoparticles and Coal Slag on Mechanical and Durability Properties of Concrete against Acidic Environments

In recent years, natural pozzolans have been proposed as a way to improve the mechanical and biocompatible properties of concrete. This study investigated the effects of different amounts of nanoparticles, coal slag pozzolan, and their combination on the mechanical properties and durability of concrete. For each mixed design, nine cubic samples of 10 × 10 × 10 cm and 30 × 15 cm were made and then cured in water for 28 days before being tested for compressive and tensile strength. According to the results, pozzolan at about 5% of cement weight increased the compressive strength of concrete compared to samples without pozzolan. Nanoparticles of FeNi3 greatly enhanced the compressive and tensile strength of concrete in most samples containing nanoparticles. The compressive and tensile strength of 28-day concrete increased by 27% and 18%, respectively. Pozzolan (10%) and 2% of FeNi3 (CP10F2) in concrete also reduced the water absorption of the samples, which can improve the durability parameters of concrete. In concrete exposed to sulfuric acid, sample CP0F2 (2% of FeNi3 nanoparticles) had a positive effect on compressive strength, and samples containing 2% of FeNi3 nanoparticles had higher compressive strength than those with pozzolan replacing cement. The simultaneous use of coal slag and FeNi3 nanoparticles has increased the mechanical properties and durability of concrete in addition to reducing cement consumption.

Durability and Mechanical Aspects of UHPC Incorporating Fly Ash and Natural Pozzolan

Durability and Mechanical Aspects of UHPC Incorporating Fly Ash and Natural Pozzolan

Systematic Mix Design Study on Geopolymers—Prediction of Compressive Strength

Due to the demand for decarbonization of the construction sector, research on alkali-activated binders and material-minimized carbon-reinforced structures has gained momentum in recent years. Most of the research into alkali-activated binders is focused on developing market-ready alternatives, mainly using a trial-and-error approach. In this study, an attempt is made to identify and quantify the factors influencing compressive strength development. Due to their worldwide availability, investigations are being carried out into binders based on calcined clays and natural pozzolans. The goal is to develop a method to produce tailor-made AAB for continuous manufacturing methods to combine carbon reinforcement and alkali-activated materials. For this purpose, an experimental matrix with 20 variation parameters was set up, in which the activator solution and the precursor composition varied. The design of the experiments was used to minimize the number of experiments. It was shown that no single factor is responsible for the development of compressive strength but instead involves several interacting factors. It was possible to find empirical formulas for predicting the compressive strength after 2, 7, and 28 days.

Rapid estimation of natural pozzolan dosages for mitigating ASR using the innovative chemical screening tool (CST)

Our research aimed to validate a previously developed chemical screening tool (CST) for estimating the dosage of natural pozzolans (NPs) in mitigating alkali-silica reaction (ASR) in concrete. Experimental evaluation showed that NPs contribute low soluble alkalis into pore solution despite their high bulk alkali contents. Consequently, CST predicted a 28–30 % dosage of NPs to mitigate ASR for a highly reactive fine aggregate satisfying concrete pore solution alkalinity ≤ aggregate threshold alkalinity criterion. CST-based estimations were favorably validated through ASR tests. Overall, the effectiveness of CST for rapid estimation of NP dosages for ASR mitigation with acceptable accuracy was successfully validated.

Strength and Durability Studies on Micro Concrete

The use of pozzolanic materials in concrete to partially replace cement is increasing. Economic benefits are obtained by replacing a significant portion of cement with low-cost natural pozzolan or industrial by- products. The durability of the final product is also increased. Pozzolanic can be used to increase durability, reduce costs, and reduce pollution without reducing the final compressive strength or other performance characteristics. To investigate the durability and strength properties of micro-concrete, an extensive literature study was performed. From the review of the literature, it was found that industrial wastes such as fly ash, Ground Granulated blast slag, waste glass powder, silica fumes and metakaoline products are used to produce concrete. In this study, it is proposed to produce micro-concrete by replacing cement with Ground Granulated blast slag and waste glass powder.the strength and durability studies will be performed. Key Words: Micro Concrete, Rehabilitation, GGBS, Waste Glass Powder, Strength, Durability

A Locally Available Natural Pozzolan as a Supplementary Cementitious Material in Portland Cement Concrete

For several decades, class F fly ash has been an attractive supplementary cementitious material, at least in part, due to its ability to reduce Portland cement consumption and mitigate alkali-silica reactions in concrete. However, fly ash availability is becoming uncertain as the energy industry decommissions coal burning power plants as it transitions to renewable energy production. This situation creates a need to identify viable and sustainable alternative supplementary cementitious materials. There are several types of supplementary cementitious materials, such as natural pozzolans, metakaolin, or ground granulated blast-furnace slag, which appear to be potential alternatives to fly ash in concrete. In this research, a locally available natural pozzolan (pumicite) was selected to replace fly ash in concrete. After conducting alkali-silica reaction tests on mortar mixtures, rheological and strength properties, shrinkage, resistance to freezing and thawing, and chloride ion permeability of concrete mixtures containing different amounts of fly ash and natural pozzolan were evaluated. The results showed that pumicite was more effective than fly ash at mitigating the alkali-silica reaction, and a pumicite content of 20% was necessary to mitigate the alkali-silica reaction. Ternary mixtures containing both pumicite and fly ash were the most effective cementitious materials combinations for mitigating the alkali-silica reaction expansion. Additionally, pumicite provided acceptable compressive strength and modulus of rupture values (greater than 4.0 MPa) that exceeded the flexural strengths provided by established mixtures containing only fly ash. Shrinkage and durability factor values for all mixtures were less than 710 μstrain and greater than 75, which are generally considered acceptable. Additionally, all mixtures with acceptable alkali-silica reaction expansions had very low chloride permeability. These results indicate that pumicite can be a reliable alternative for fly ash.

Impact of Partial Replacement of Cement with a Blend of Marble and Granite Waste Powder on Mortar

The purpose of this study is to examine the effects of partially replacing cement with a blend of marble waste powder (MWP) and granite waste powder (GWP) in mortar, with the goal of reducing the environmental harm caused by cement. The investigation included an analysis of the distinctive properties of the two waste powders individually, as well as initial tests with various ratios to determine the optimal combination that yields the highest strength. It was observed that a 50% MWP to 50% GWP blend produced the most substantial strength. Subsequently, the effect of partial replacement of cement with the blend of marble and granite waste powder (MGWP) at various increments of 5%, ranging from 0% to 30%, was evaluated by subjecting the mortar to numerous tests to assess its workability, physical, mechanical, durability, and microstructural properties. The analysis of the employed waste powders confirmed that the GWP can be classified as a natural pozzolan material belonging to Class N. As the proportion of MGWP increased, the workability of the mortar mixes decreased. However, incorporating MGWP up to 15% resulted in enhancements in bulk density, compression strength, and homogeneity, with the best performance observed at a 10% MGWP content. Microstructure analysis confirmed that the addition of MGWP enhanced the bonding of C–S–H and C–H, leading to a denser morphological structure in the mixes, particularly at a 10% MGWP content. The utilization of MGWP not only significantly reduced the carbon footprint associated with cement production but also fostered sustainability.

Use of the Algerian natural pozzolan for the production of a geopolymer as a complete cement replacement

This paper investigates the use of the Algerian Beni Saf natural Pozzolan (BSP) to produce a geopolymer (GP) as a complete replacement material for the traditional binder of OPC. No such study has been carried out on using the Algerian BSP for GP synthesis, especially as the latter’s properties have a high dependency on the precursor material characteristics. The research sets to establish the optimal combination of alkaline activators that corresponds to the BSP, sand content, and curing temperature. A series of experiments were carried out on BSP-based GP mortars in fresh and hardened states to investigate properties such workability, CS, and FS at 3, 7, 28, and 90 days. Selected GP samples were subjected to microstructure characterization experiments, including FTIR and SEM-EDS. The results have shown that workability is greatly affected by the studied parameters. The optimal values of CS and FS at 28 days were 38 and 12 MPa, respectively. These were obtained for sand/pozzolan ratio, Si/Al, Si/Na, and temperature equal to 2.5, 6.1, 2, and 80 °C respectively. The microstructure analyses also revealed a considerable change in the microstructure GP samples.

A comparative study of compressed lateritic earth bricks stabilized with natural pozzolan-based geopolymer binders synthesized in acidic and alkaline conditions

Two geopolymer binder systems made under alkaline and acidic conditions have been evaluated for the stabilization of compressed lateritic earth bricks (CEBs) using natural pozzolan as aluminosilicate precursor. The preparation of alkaline and acidic activators involved the combination of sodium silicate and 10 mol/L sodium hydroxide solutions, as well as 10 mol/L phosphoric acid solutions, respectively. CEBs were prepared to comprise different proportions of natural pozzolan of 5, 10, 15, and 20 %. The physico-mechanical and mineralogical properties of compressed earth bricks were studied using the compressive strength, the dry and wet bulk density, the water absorption rate, Fourier transform infrared spectroscopy (FTIR), powder X-Ray Diffraction (PXRD) and optical microscopy (OM).The results showed that in the acid environment, the mechanical performance increased considerably with the pozzolan content and slightly with the curing time, whereas in the alkaline environment these performance decrease for the sample with 0 to 10 % of pozzolan and remain constant for the sample with 15 to 20 % of pozzolan after 14 days of curing. The utilization of acid-activated geopolymer binder in the production of laterite-based compressed earth bricks has been shown to be more effective compared to the utilization of an alkali-activated geopolymer binder. The high performance of acid-stabilized CEBs is related to the best reactivity of natural pozzolan in acid medium allowing the formation of Al-O-P bonds.

Decarbonization of the concrete railway sleeper production: bringing the low-dosage pozzolanic cement usage in the sleeper production via novel laminated CFRPU reinforcement technique

This study presents four new concrete railway sleeper models' environmental emission and service life investigations. Both of these two factors are crucial for a sustainable railway sleeper model. Investigated sleepers are solely reinforced with engineered laminated carbon-fiber-reinforced polyurethane (L-CFRPU) materials. This novel concrete sleeper reinforcement technique was needed to overcome the following two challenges preferred because of the environmental sustainability objectives: First, the new LCR-G-type sleepers are produced with a 30% lower (on average) cement dosage. Second, an eco-friendly cement containing approximately 50% natural pozzolan is utilized. Accordingly, the new sleeper model's total concrete raw materials-based equivalent CO2 emission value is 54% less (on average) than conventional concrete railway sleepers. This emission decrease (decarbonization) rate is well above the other eco-friendly concrete sleeper studies in the literature. However, the compressive strength of the sleeper concrete has almost halved. For this reason, investigations continued with the mechanical strength tests specified in the concrete sleeper standards for preliminary service life evaluations. For these purposes, in this study, the latest EN 13230-3:2016 standard test setup was used with some improvements, such as precise deflection measurements oriented to the sleeper-rail-seat- center points. The test results show that all four models of new LCR-G-type sleeper variations have met the sleeper technical specifications' static strength limits and crack-reclosing conditions. Consequently, it is recommended to investigate further the sustainability potential of this new concrete sleeper production method, whose preliminary evaluations have been made in this study for the first time in the literature.