Natural Pozzolana Research Articles

A contribution to the study of phosphate’s effects on calcareous soils to be stabilized with lime and natural pozzolana

When investigating the potential use of lime and natural pozzolana for subgrade soils containing phosphate, especially on agricultural lands, the effectiveness of these traditional binders needs to be assessed because of the possible deleterious effect of phosphates anions. This paper addresses this question using the problematic marly soil of Medea which was deliberately contaminated with a common fertilizer mono ammonium phosphate (0, 2, 4 and 6% by dry weight) and then stabilized with lime and/or natural pozzolana (0, 8%),(0, 20%) by dry weight respectively. Micro and macrostructural changes of these mixtures were studied under X-Ray diffraction test and Scanning electron microscope imaging. Variations of pH levels on a 90 days period, Atterberg limits between 1 to 30 days of curing, normal Proctor parameters, immediate bearing index at optimum moisture were also carried out. Overall, the results indicate that the uncontaminated marly clay soil wasn’t very reactive to lime stabilization even with 8% lime and it required the addition of natural pozzolana with lime to exhibit some improvements. Aside from that, phosphates proved to be deleterious for stabilizing marly clay of Medea producing considerable impact on all the results. It was also shown that calcite present in the soil can interfere with the employed stabilization technique.

Effects of Volcanic Tuff Use on the Rheological and Mechanical Properties of Self-Compacting Concrete

The rise in demand of concrete products has led to overexploitation of river sand the main fine aggregate in concrete resulting in major environmental degradation. As a result, researchers have focused their efforts on developing eco-friendly concrete using alternative renewable materials like volcanic tuff and other natural pozzolana types. This study therefore, aims at investigating the use of Kenyan, Kitengela volcanic tuff as a partial replacement of river sand in self-compacting concrete, and determining the effects it will have on the rheological and mechanical properties of the self-compacting concrete. The study involved partially replacing river sand with volcanic tuff in percentages of 0%, 2.5%, 5%, 7.5% and 10% and carrying out rheological tests (V-funnel test, L-box test, T-500 test and J-ring test) on fresh concrete and mechanical tests (compressive strength and tensile strength tests) on hardened self-compacting concrete on days 7, 14, and 28 to determine the effects of volcanic tuff on properties of both fresh and hardened self-compacting concrete. There was a general decrease in rheological properties (flow and passing abilities) of self-compacting concrete with increase in volcanic tuff percentage replacement from 0 % to 10%, with least flow and passing abilities recorded at 10% replacement. Similarly, increase in volcanic tuff percentage replacement led to decrease in both compressive and tensile strength of self-compacting concrete with lowest values recorded at 10% volcanic tuff replacement.

Life Cycle Analysis Comparison of Stabilizing Materials for Expansive Soils

Expansive soils present significant challenges to infrastructure stability, necessitating the use of stabilizing materials. This study conducts a comprehensive life cycle analysis (LCA) research design to evaluate the environmental sustainability of various stabilizing materials for expansive soil. The study uses a quantitative analysis assessing materials, including cement, limestone, natural pozzolana, iron ore tailings, and geopolymers (especially alkali-activated slag cement). The method involves a comprehensive LCA, considering phases from raw material extraction through production, use, and disposal. The analysis reveals distinct differences in environmental impact. Cement and lime, common stabilizers, show a high carbon footprint. Natural pozzolana and iron ore tailings exhibit potential as supplementary cementitious materials with reduced environmental impact. Geopolymers, particularly alkali-activated slag cement, offer promising alternatives with lower carbon emissions. This research contributes insights into sustainable geotechnical practices, guiding material selection aligned with environmental goals for effective expansive soil stabilization.

The remarkable potential of machine learning algorithms in estimating water permeability of concrete incorporating nano natural pozzolana

This paper aims to estimate the permeability of concrete by replacing the laboratory tests with robust machine learning (ML)-based models. For this purpose, the potential of twelve well-known ML techniques was investigated in estimating the water penetration depth (WPD) of nano natural pozzolana (NNP)-reinforced concrete based on 840 data points. The preparation of concrete specimens was based on the different combinations of NNP content, water-to-cement (W/C) ratio, median particle size (MPS) of NNP, and curing time (CT). Comparing the results estimated by the ML models with the laboratory results revealed that the hist-gradient boosting regressor (HGBR) and K-nearest neighbors (KNN) algorithms were the most and least robust models to estimate the WPD of NNP-reinforced concrete, respectively. Both laboratory and ML results showed that the WPD of NNP-reinforced concrete decreased with the increase of the NNP content from 1 to 4%, the decrease of the W/C ratio and the MPS, and the increase of the CT. To further aid in the estimation of concrete’s WPD for engineering challenges, a graphical user interface for the ML-based models was developed. Proposing such a model may be effectively employed in the management of concrete quality.

Understanding the role of natural pozzolana in regulating the early hydration reaction process and microstructure of Portland cement

The present study examines the regulatory role of natural pozzolana (NP) on the early-age hydration process and microstructural development of Portland cement. Through a series of experiments, including low-field nuclear magnetic resonance (NMR), X-ray diffraction (XRD), thermogravimetric (TG) analysis and scanning electron microscopy (SEM), it was found that NP significantly influences the hydration kinetics and chemical shrinkage of cement paste. The addition of NP was shown to reduce the early-age chemical shrinkage and refine the microstructure by decreasing the quantity of harmful pores and increasing harmless pores, as evidenced by the bimodal distribution observed in pore size distribution (PSD) analysis. XRD and TG results indicate that NP reacts with calcium hydroxide to form additional calcium silicate hydrate (C-S-H) gel, thus improving the interfacial transition zone and resistance to carbonation. SEM micrographs further confirm the improved microstructure with fewer microcracks. The findings suggest that NP can be effectively utilized to optimize the early-age performance of concrete, offering a sustainable approach to improving its durability and long-term structural integrity.

Effect of Natural Pozzolana on Physical and Mechanical Properties of Concrete

Construction industries are rapidly growing, sacking high amounts of concrete which has a highly dense microstructure with excellent mechanical properties, more durable, and highly eco-friendly materials. Hence, many of the researchers are interested in solving this problem with replacing concrete by natural pozzolana (NP) which is a supplementary cementitious material mostly from volcanic sources having much active silica content that can improve the durability and mechanical properties of concrete. However, it is not well-known which common optimum replacement range can give the most desirable concrete properties. So, the present study sought to review the effects of replacing NP from volcanic sources on the durability, physical, mechanical, and microstructural properties of concrete, also, to identify the most common dose of a positive effect as a replacement in concrete. The review shows that many of NP used by different literature from different places satisfy ASTM replacement standard in concrete, especially, based on its chemical compositions. Also, the review observed that employing NP in concrete significantly improves concrete workability, lengthens setting time, and reduces bulk density, porosity, water absorption, and chloride ion migration by making denser concrete microstructure. In general, adding 5%–20% of NP in concrete significantly improves compressive strength, split tensile strength, and flexural strength. Specifically, most of the studies found 15% replacement of NP having volcanic sources can give optimum strength. Besides these, most of the studies indicated that the improvement of the strength was more visible at the concrete age of 7–28 days.

Improved of Mechanical Characteristics of Gargar Mud by Mineral Additives

The operational dams in Algeria lose 32 million m3 of water storage capacity each year, and fifteen of these dams are threatened by siltation. This investigation forms a component of a management strategy for dredged silt in the Gargar Dam, the third-largest dam in Algeria with considerable sedimentation. This paper comprises two main axes: a detailed experimental study based on the studied dam mud's physico-chemical, rheological, and mechanical analysis. The second part is based on the study of the valorization of Gargar mud to be acceptable for use in road civil engineering. In order to obtain this goal, the Gargar mud was treated with lime (0-6%), sand (20%), and natural pozzolana (20%). Test results show that the properties of Gargar mud are significantly improved after treatment, and the soil becomes more friable and more resistant; it can therefore be used as a foundation layer in road civil engineering.

Experimental investigation on strength characteristics of autoclave aerated concrete block using natural pozzolanas

In this present study we have studied about the strength enhancement of autoclaved aerated block by using natural pozzolanas. Fly ash has been partially replaced with GGBS. GGBS has been used in place of fly ash at percentages of 6%, 12%, and 18% of the total amount of fly ash plus super plasticizer. GGBS improves resistance to damage from alkali silica reaction. It also reduces the thermal cracking. The role of super plasticizer is to reduce the water content in block.we have used 1% of super plastizer to the 1 litre of water. Each block's compressive strength is measured and computed for varying fly ash and GGBS ratios. It has been observed that replacing GGBS with 12% yields higher compressive strength than replacing it with 6% or 18%.

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.

Effect of Natural Pozzolana and Scrap Tire Rubber Mixture on Compacted Clayey Soils

Effect of Natural Pozzolana and Scrap Tire Rubber Mixture on Compacted Clayey Soils

Evaluating the Printability and Rheological and Mechanical Properties of 3D-Printed Earthen Mixes for Carbon-Neutral Buildings

This research delves into the vital aspect of adapting local soil properties for 3D printing and explores the mix design of collected earthen materials to tackle challenges in printability, shrinkage, and mechanical properties. Initially, soil samples from six local sites underwent characterization based on Atterberg’s limits, focusing on identifying the most suitable high-clay-content soil. The soil with a higher clay content was used for further study, and its clay type was determined using an X-ray diffraction (XRD) analysis, revealing the presence of 49% kaolinite, 15% nontronite, and 36% illite clay minerals. Four earthen mixes were designed by including stabilizers (i.e., hydrated lime), natural pozzolana, and degradable natural fibers (wheat straw fiber). Subsequently, the study examined their rheological properties, shrinkage behavior, compressive and flexural strength, and printability (including extrudability and buildability). The pure soil mixture excelled in printing quality and mechanical strength, but suffered from cracking and drying shrinkage due to its high nontronite clay content. The existence of 15% nontronite clay mineral in the soil resulted in significant shrinkage and extensive cracking of specimens. However, fiber incorporation effectively mitigated large cracks and reduced shrinkage to as low as 2.6%. Despite initial expectations, introducing lime and pozzolana as soil stabilizers did not improve strength, prevent shrinkage, or improve the printability of soil mixes.

Behavior of Natural Pozzolana-Lime-stabilized Clayey Soils Artificially Contaminated by Sulfates

The use of lime in sulfate-bearing clayey soils has historically caused structural damage to infrastructures due to the formation of an expansive ettringite mineral. In this paper, a research was conducted to study the effectiveness of natural pozzolana (NP) for providing better stabilization of sulfate-bearing soils. Compaction and free-swell potential tests were first performed on lime-stabilized grey and red clayey soils (GS and RS) containing different contents of added sodium and calcium sulfates (2, 4 and 6% Na2SO4 or CaSO4·2H2O). Then, the same tests were repeated by adding 20%NP. The test results indicated that the presence of 4% and 6% Na2SO4 in the soil resulted in an abnormal increase in the swell potential of both lime-stabilized GS and RS. The X-ray diffraction (XRD) results confirmed the growth of the ettringite mineral responsible for this higher swell potential. However, the use of 8% lime with 20%NP in stabilizing sulfate-bearing clayey soils produced significant improvements in the optimum moisture content (OMC) and maximum dry density (MDD), as well as in the swell potential. The addition of 20%NP into the lime-stabilized GS and RS eliminated the harmful effect of Na2SO4. In addition, for 120-day curing period, the use of 6% CaSO4·2H2O was found very effective by reducing the swell potential of NP-lime-stabilized GS and RS from 7.33% to 0.4% and from 2.79% to 0.2%, respectively trips. KEYWORDS: Clayey soils, Mineral additives, Sulfates, Compaction, Swell potential, Stabilization.

Slags from roasting of antimony ore in the Brioude-Massiac (France) area used as aggregates: An early example of circular economy.

Towards the end of the 19th century and the early 20th century, France was the world's largest producer of antimony, especially due to the rich deposits in the Brioude-Massiac area. Even though all the mining and smelting activities are long gone, there are still some remains of those activities. The most original of those is the use of roasting slags as aggregates in former plant walls or industrial building. They are macroscopically characterised by a black or red colour with a vesicular aspect similar to natural pozzolanas. Common petrography and mineralogy tools have been used to characterise those slags: optical mineralogy, scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction (XRD). To gain an insight into their mineral complexity, a QEMSCAN map has been produced. The mineralogy is typical of high-temperature slags: cristobalite, quartz, mullite, fayalite-forsterite series and spinel. The antimony content is quite high, up to seven percent, under the form of various antimony oxides and native antimony.

Effect of Volcanic Ash and Natural Pozzolana on mechanical properties of sustainable cement concrete: A comprehensive review

Environmental degradation is on the rise due to escalating pollution caused by raw material depletion and the increasing demand for concrete products. Consequently, researchers and scientists have dedicated significant efforts towards developing sustainable, eco-friendly concrete using renewable materials. Among these materials, Volcanic Ash (VA) and other Natural Pozzolana (NP) types have emerged as promising Supplementary Cementitious Materials (SCMs). VA and NP types play a crucial role in reducing costs, energy consumption, and environmental impacts associated with cement production. Thus, it is imperative to investigate the characteristics of VA and NP and their influence on the performance of concrete and cement mortar. This paper presents a comprehensive review of previous studies examining the effect of VA and other NP types on the mechanical properties of concrete while evaluating their chemical, physical, and microstructure characteristics. The findings from these studies indicate that the properties of concrete primarily depend on the characteristics and quantities of NP employed. Notably, silica dioxide (SiO2) comprises the predominant component in VA compositions. In most cases, an increase in VA and NP content within concrete mixtures leads to a reduction in strength. Finally, recommendations and suggestions for future research are provided to enhance concrete properties and achieve the development of sustainable construction materials.

Fly Ash and Natural Pozzolana Impacts on Sustainable Concrete Permeability and Mechanical Properties

This paper studied the effect of fly ash (FA) and natural pozzolana (NP) as partial cement substitutes on sustainable concrete permeability and mechanical and microstructural properties. Batches with 10, 20, 30, 40, and 50% FA and NP replacements for cement were prepared and tested for compressive strength after 7, 28, and 56 curing days and for flexural strength after 28 curing days. Permeability testing was conducted on all samples. A qualitative microstructural analysis was performed using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX). The mechanical properties results showed slight strength improvements when replacing the cement with low percentages of the pozzolanic materials. The compressive strengths of the batches with 10% FA and NP replacements of cement showed compressive strength increases of 11.63 and 8.75%, respectively, compared to that of plain concrete. On the other hand, the flexural strength for the batches with FA replacement of cement achieved at least a 15.6% increase compared to that of the control. Moreover, FA and NP replacement of cement had a positive impact on batch permeability, with decreased permeability values reaching 78.3 and 56.5%, respectively, compared to that of the control. Furthermore, the microstructural analysis indicated that adding FA and NP would enhance cement hydration by the formation of dense hydration products such as calcium–silicate–hydrate (C-S-H) crystals, which increased hardened concrete strength. Finally, the cost analysis showed that the batch with a 10% FA replacement of cement is the ideal one in this study.

Strength Improvement Using Polypropylene Fiber as Reinforcement in Natural Pozzolana-lime-stabilized Expansive Clayey Soil Artificially Contaminated by Sulfates

This paper aims to assess the behavior of the unconfined compressive strength (UCS) of polypropylene fiber (PF) reinforced natural pozzolana-lime-stabilized expansive grey clayey soil (GS) contaminated by sulfates. Lime (0–8%), natural pozzolana (NP) (0–20%), and PF (0–3%) by dry weight of soil were used. GS was contaminated by different sulfate contents (0-6%) and UCS was assessed at various curing periods (7–120 days). Results showed that adding 8% lime alone or with 20% NP considerably improved UCS. Including 1% or 2% PF as reinforcement without sulfates in lime-stabilized GS transferred stress from GS to PF due to bonding. However, increasing PF beyond 2% formed lumps, reducing contact and friction coefficient, thus decreasing UCS. This means that the optimum PF dosage was found to be 2%. The UCS of GS increased with PF content up to 2% and then decreased. The UCS significantly increased with higher calcium sulfate content and curing period due to observed cementing agents in X-ray diffraction (XRD) and scanning electron microscopy (SEM). Adverse effect of ettringite mineral on UCS caused by sodium sulfate addition was suppressed with the combination of 20% NP and 2% PF in lime-stabilized GS. Binding forces from lime and NP resisted to ettringite expansion. Sensitivity of UCS to sulfate effect was more pronounced with sodium sulfate than calcium sulfate. In addition, NP–PF mixture in lime-stabilized GS was more effective, improving the strength of expansive soil, especially with sodium sulfate. In conclusion, reinforcement of NP-lime-stabilized expansive soils with PF is an effective method.

Optimization of alkali-activated binders using natural minerals and industrial waste materials as precursor materials

This paper presents the results of a study on developing optimized alkali-activated binders (AABs) utilizing selected natural minerals and industrial byproducts as precursor materials in addition to sodium hydroxide and sodium silicate as activators. Four selected precursor materials (natural pozzolana, limestone powder, red mud, and silicomanganese fume) were characterized in terms of their physical and chemical properties. The proportioning of the four precursor materials was optimized based on the results of flow, setting time, and compressive strength tests conducted on trial mortars. After reaching an optimal proportioning of the four precursor materials, the natural pozzolan was partially replaced by ordinary Portland cement (maximum 30% by wt.) to significantly enhance the properties of the AABs. The activator to precursor (A/P) ratio, sodium silicate to sodium hydroxide (NS/NH) ratio, sodium hydroxide (NH) molarity, and water to precursor (W/P) ratio, were varied from 0.3 to 0.6, 1 to 2.5, 8 to14 M, and 0.35 to 0.55, respectively. The influence of these activation parameters (at the optimally selected proportioning of precursor materials) on the physical and mechanical properties of AABs besides their mineral composition and morphology was investigated leading towards selecting the optimum AABs. The compressive strength at 28 days ranged from 28.5 to 32 MPa, 24.15 to 31.8 MPa, 24.2 to 33.1 MPa, 15.33 to 31.16 MPa, and 19.7 to 34.1 MPa, as A/P ratio, NS/NH ratio, NH molarity, W/P ratio, and curing method and duration were varied, respectively. XRD, FTIR, and SEM analyses of the AABs were conducted to validate the trends observed in the compressive strength results with variation in the activation parameters. The main phases detected by XRD included CSH, CASH, Mn-SH, KASH, and NASH. FTIR analysis showed bands that coincide with reported vibration and stretching of Si–O-M (M → Al, Si, or Mn) that are associated with geopolymerization, while SEM imaging showed dense microstructure with a homogenous distribution of polymerization gels that filled the microcracks and voids. Additionally, the effect of curing regimes (oven, steam and ambient-air curing) on the performance of AABs was also examined. The results of the present work enabled to identify the optimum proportioning of the selected precursor materials, optimum combination of A/P ratio, NS/NH ratio, NH molarity, and W/P ratio for producing the AABs with enhanced performance.

Calcium-Based Binders in Concrete or Soil Stabilization: Challenges, Problems, and Calcined Clay as Partial Replacement to Produce Low-Carbon Cement.

Calcium-based binders, such as ordinary Portland cement (OPC) and lime (CaO), are the most common artificial cementitious materials used worldwide for concrete and soil improvement. However, using cement and lime has become one of the main concerns for engineers because they negatively affect the environment and economy, prompting research into alternative materials. The energy consumption involved in producing cementitious materials is high, and the subsequent CO2 emissions account for 8% of the total CO2 emissions. In recent years, an investigation into cement concrete's sustainable and low-carbon characteristics has become the industry's focus, achieved by using supplementary cementitious materials. This paper aims to review the problems and challenges encountered when using cement and lime. Calcined clay (natural pozzolana) has been used as a possible supplement or partial substitute to produce low-carbon cement or lime from 2012-2022. These materials can improve the concrete mixture's performance, durability, and sustainability. Calcined clay has been utilized widely in concrete mixtures because it produces a low-carbon cement-based material. Owing to the large amount of calcined clay used, the clinker content of cement can be lowered by as much as 50% compared with traditional OPC. It helps conserve the limestone resources used in cement manufacture and helps reduce the carbon footprint associated with the cement industry. Its application is gradually growing in places such as Latin America and South Asia.

Effect of Natural Pozzolana on the Unconsolidated Undrained Shear Strength of a Lime-Stabilized Clay Soil

Effect of Natural Pozzolana on the Unconsolidated Undrained Shear Strength of a Lime-Stabilized Clay Soil