Natural Pozzolan Research Articles

Durability properties of concrete containing amorphous silicate tuff as a type of natural cementitious material

Due to the increasing growth of building technology, the production of new durable concrete using sustainable material is one of the most important aspects of this industry. With regard to the destructive environmental aspects of cement production, many efforts have been made to partially replace cement with pozzolanic materials that have less destructive effects and can improve the performance of the produced concrete. In this study, an amorphous silicate tuff (AST) has been introduced as a natural pozzolan and its chemical and physical properties have been assessed, as well as, the compressive strength and durability of the produced concrete. Using the full factorial design method, the total number of 24 concrete mix samples was designed by replacing 0–40% Portland cement with AST and water to binder ratios between 0.45 and 0.6. Compressive strength, rapid chloride permeability, rapid chloride migration, and bulk electrical conductivity tests were carried out at various ages (384 experiments). The results show that the best-improved properties of concrete were achieved for samples with 5% AST replacement. In addition, there are relatively good correlations among the results of mechanical and durability tests.

Characterization of scoria rock from Arabian lava fields as natural pozzolan for use in concrete

The feasibility studies of using alternative cementitious materials (ACMs) in concrete construction are conducted using various characterization tests. Different samples of scoria rocks (SR) were procured from different regions of the Arabian Shield and investigated for use as ACMs. Various methods and characterization techniques were conducted. Characterization results revealed that the pozzolanic activity of SR in mortar does not correlate well with the sum of the main elemental oxides (SiO2+Al2O3+Fe2O3), as per the requirement of ASTM C618. Concrete mixtures containing 30% SR per cement weight were prepared and tested at 28 and 90 days to evaluate the performance of SR for construction applications. Furthermore, the mortar and concrete mixtures containing SR have shown a slow rate of pozzolanic activity at early ages. However, the development in compressive strength was enhanced at later ages dependent on the mineralogical compositions of SR. It is concluded that the improvement in strength could be corroborated based on the formation of tobermorite-like structures, as confirmed using XRD and thermal analyses. These structures result from the reaction of minerals of amorphous sodium aluminosilicate phase (albite minerals) in SR with portlandite liberated during cement hydration. Conclusively, SR reacts as a pozzolan not as a filler.

Evaluation of Mechanical and Durability Properties of Concrete Containing Natural Chekneh Pozzolan and Wood Chips

In this paper, effects of natural pozzolan, called Chekneh, as a part of cement replacement and wood chips as a part of mixture aggregates on the mechanical and durability properties of concrete were studied. Nine concrete mixtures proportions within two categories were prepared. In the first category, the properties of concrete were evaluated by adding 10 and 15% of Chekneh pozzolan or wood chips and the second category containing combination of Chekneh pozzolan and wood chips was prepared. The results showed that adding optimal content of natural Chekneh, 10% of cement weight replacement to concrete improves the mechanical properties including flexural, compressive and tensile strength and durability properties of concrete including volumetric water absorption, electrical resistance and rapid chloride permeability. Also, the replacement of 10% wood chips as a part of aggregates causes improvement in mechanical properties of concrete. The combined effect of natural pozzolan and wood chips has the most positive effect on increasing the compressive, tensile and flexural strength in concrete, and the sample which contains 10% pozzolan and 10% wood chips has the most improvement compared to the control sample.

Using Natural Pozzolan, Cement and Lime for Stabilizing Soil in Earth Dams

The paper has focused on studying the ability of using natural pozzolan to combine lime and cement in process of stabilized soil, implementing experimental contents for on-site soil including: grain composition, plastic limit, plasticity index, mineral parts and other common mechanical properties, standard compaction. Followed by experiments for soil, cement and pozzolan stabilized soil mixtures, including standard compaction, compressive strength. A suitable model of physical experiments to simulate and prove lime, cement and pozzolan stabilized soil meets the criteria for making waterproofing materials for earth dams in the Central Highlands

Optimization of production parameters of geopolymer mortar and concrete: A comprehensive experimental study

Geopolymers are a new type of material offered as an alternative to traditional Portland cement. Geopolymers, produced by activation of natural and waste pozzolans with alkali activators such as NaOH (SH) and Na2O·3SiO2 (SS) solutions, have been widely supported and investigated due to environmental and economic advantages. In this study, a detailed experimental program was conducted to investigate the influence of activator type, activator concentration and curing temperature on mechanical and microstructural properties of volcanic tuff based geopolymer mortar (GPM) and concrete (GPC) samples. A total of 1080 GPM and GPC samples were produced and a number of parameters were investigated with 360 combinations. Maximum compressive strength was obtained as 37.09 MPa in 90-day samples in which the SH concentration was 16 M, activator/binder (a/b) ratio was 0.45 and the curing temperature was 120 °C. As a result of optimization of the production parameters, a considerable development in mechanical and microstructural properties of GPM and GPC samples was obtained. Experimental results demonstrated that alkali activation with sole SH bring about superior characteristics compared to alkali activation with SH + SS. Higher a/b ratio led to higher UPV values because of more dense and compact microstructure resulting from increase in gopolymerization reactions. This is also supported by compressive strength and microstructure findings.

The Influence of Natural Pozzolans Structure on Marl Soil Stabilization

Marl as a calcareous soil has heterogeneous nature in terms of structure and properties. Any change in the water content of marl can cause significant strength loss; therefore, prior stabilization while constructing civil infrastructures is necessary. A fundamental element in soil stabilization is the relationship between soil structure and stabilizers, but this important factor has been ignored in the available literature, especially in the case of marl soil. Lately, alternative environmentally friendly additives (natural pozzolans) as well as traditional chemical stabilizers (cement and lime) have been successfully used for stabilization of marl soil. This paper presents the results of an experimental study which investigates the influence of natural pozzolans structure on marl soil stabilization. Transmission electron microscopy (TEM), X-ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR) tests were used for size and structure analysis of marl soil and two types of natural pozzolans called Qizkorpi and Mamaloo of Iran which have been successfully used for marl soil stabilization by the authors, recently. Based on the obtained results by TEM, FTIR, and XRF tests, due to the similarity of the structure and size of Gizkorpi volcanic ash and marl soil when compared to that of Mamaloo volcanic ash, it can be concluded that the electrostatic and magnetic interactions in marl and Gizkorpi volcanic ash lead to a better stabilization and strengthen of the marl, while these interactions are less in Mamaloo volcanic ash when mixed with the marl soil.

Stabilisation of Urmia Lake peat using natural and artificial pozzolans

Peat generally found in thick layers in limited areas such as Urmia Lake, Iran has low shear strength and high compressive deformation. Therefore, an appropriate soil improvement method is required. This paper presents an experimental study of the stabilisation of Urmia Lake peat on the Urmia–Tabriz highway, 7·8 km to the east of Urmia city in Iran. A type of fly ash (artificial pozzolan) and two types of volcanic ashes (natural pozzolans) were used in this investigation. Unconfined compressive strength (UCS) and California bearing ratio (CBR) tests were conducted on stabilised mixtures and untreated soil samples after 3 and 7 d of curing. According to the obtained results, the UCS of peat can be increased by using both the fly ash and the volcanic ash, but the amount of strength increase depends on the organic content, water content, stabiliser content and its particle size. Furthermore, the CBR test showed that the filling property of the stabiliser is as useful as its pozzolanic activity in increasing the bearing capacity of peat in road constructions.

Microchemistry and microstructure of sustainable mined zeolite-geopolymer

Geopolymers are three-dimensional amorphous Si-O-Al networks that generally can be synthesized from low-Ca aluminosilicate mineral sources. Such materials were first introduced as a sustainable construction material but today their application goes beyond the building industry. So far, a broad range of aluminosilicate minerals including fly ash, natural pozzolans, kaolin and metakaolin have been used to produce geopolymers; however, there are limited studies on the geopolymerization of porous and crystalline aluminosilicate minerals such as mined zeolites. Use of zeolite as it is for commercial applications depends on the shape and architecture of these materials. Therefore, the hypothesis was that geopolymerization provides the possibility of using mined zeolite in different shapes. Moreover, zeolite as a nontoxic mineral material with an inherent 3D structure may result in the formation of the cleaner geopolymeric product with different physical properties compared to when waste materials such as fly ash are employed. In this study, the viability of creating geopolymers from mined zeolite has been demonstrated. The aim of this study was to evaluate the influence of different parameters such as zeolite particle size, curing temperature, reagents ratio and time on amorphous content and mechanical strength. The conversion of the crystalline phase of mined zeolite to amorphous gel and/or synthetic zeolite phases was comprehensively studied using X-ray diffraction. It was found that finer zeolite particles resulted in the formation of a material with higher amorphous content (max ∼60%) and higher mechanical strength (max ∼33 MPa). It was also shown that the higher amorphous content did not necessarily translate to higher mechanical strength due to the formation of intermediate species that cannot transfer into the polycondensation stage. It was revealed that the formation of analcime and chabazite may occur through the geopolymerization process. Microstructure studies using infrared spectroscopy confirmed the geopolymer formation and development over time.

Dealing with workability loss challenge in SCC mixtures incorporating natural pozzolans: A study of natural zeolite and pumice

Substituting portland cement with natural zeolite (NZ) and pumice in self-consolidating concrete (SCC) is used to improve the workability and hardened properties of mixtures. The workability retention of SCC incorporating these natural pozzolans has remained a challenge in the literature. In this study, different methods of workability retention improvement on the natural pozzolan-SCC mixtures were investigated. These methods include the use of polycarboxylate with larger molecular weight and side chain density, retempering with superplasticizer (SP), retempering with withhold water, and a combination of retarder and SP. The fresh and hardened properties of the NZ and pumice-incorporated mixtures were investigated through measuring workability retention, setting time, and compressive strengths, in two ratios of water-to-cementitious materials (w/cm). Results show that the SCC mixtures incorporating NZ had lower setting time in comparison to the SCCs without natural pozzolans, although the setting time of SCC contained pumice increased. The NZ-incorporated SCCs required a higher dosage of SP for retempering however the pumice contained SCCs required lower SP than the reference due to the low-polymer adsorption of pumice-blended cement. The slump loss in SCC mixture without pozzolan (Ref-0.36) was more severe than the mixtures containing NZ. The reduction in compressive strength of mixtures treated with different retempering methods was insignificant but more tangible when superplasticizer and retarder were used. A larger quantity of SP was required for retempering the SCCs with retarder and SP compared with the those retempered with SP only. The increase or decrease in the SCC compressive strength in case of using retarder and SP for SCC retempering purpose was dependent on the amount of pozzolan replacement and the w/cm ratio in the mixtures. Overall, in w/cm ratio of 0.40, the SCC mixtures incorporating 10 and 15% NZ and pumice, respectively, possessed as the optimal mixtures considering the slump loss and the compressive strength.

Characterization of Hemp-Lime Bio-Composite

Hemp-lime bio-composite (hempcrete) is a new building material consisting of two main constituents: hemp shiv and lime-based binder. Hemp shiv is a woody core of Cannabis Sativa plant obtained in decortication process and chopped into particles. Lime-based binder is a mix of binders with highest content of hydrated lime (other ingredients often present in a mix are: natural hydraulic lime, pozzolans, cement and others). Its natural origin, ability to crate healthy indoor environment, good thermal properties and especially high ecological values (including low carbon emission in the entire life-cycle) makes it an sustainable alternative to commonly used materials in construction industry. Due to its mechanical properties hempcrete is not a load-bearing material. It is used as a filling material for single-layer walls with a structural frame and as an insulation material for existing walls, floors and roofs. Construction techniques include forming monolithic walls by compacting the mix in a formwork, spraying, bricklaying from precast blocks and prefabrication of entire wall elements. In this paper the results of mechanical and hygrothermal properties of the developed hemp-lime composites will be presented. The results will be used to obtain the hygrothermal characteristics of the building partitions applying numerical simulation methods.

Effect of silica modulus on the geopolymerization activity of natural pozzolans

The present study evaluates the effect of silica modulus on the reaction kinetics, degree of reaction and phase composition of natural pozzolan-based geopolymers. Six natural pozzolan samples have been subjected to geopolymer synthesis in the alkaline medium using sodium hydroxide and sodium silicate solutions at ambient conditions. Reaction kinetics studied by isothermal conduction calorimetry show that the early age dissolution of aluminate and silicate species depends on the SiO2 and Na2O molar content of the alkaline solution. The degree of reaction increases with the reduction of silica modulus. However, the reduction of silica modulus beyond certain limit has a negative influence on the mechanical properties of resultant geopolymers. The optimum silica modulus requirement depends on the mineralogical composition of the raw sample used. The rate of partial dissolution of semi-crystalline and crystalline mineral phases present in natural pozzolan depends on the silica modulus of the alkaline solution used.

Effect of slaked lime on the geopolymers synthesis of natural pozzolan from Moroccan Middle Atlas

This study presents the effect of slaked lime (Ca(OH)2) on the physical and microstructural properties of geopolymers based on natural Moroccan pozzolan. The slaked lime was incorporated at 4, 8, and 12% replacement by weight of pozzolan. Aqueous solutions of sodium hydroxide (NaOH) with different molarities (4, 6, 8, 10, and 12 M) and sodium silicate (Na2SiO3) were used as alkali activators. The molarity of 8 M NaOH was selected as the optimal concentration. The effect of slaked lime was evaluated by measuring the compressive strength (Rc), P wave propagation velocity (Vp), bulk density (D), porosity (P), and water absorption (A). Complementary studies using X-ray diffraction (XRD) and scanning electron microscopy (SEM) were also performed. The results revealed that the incorporation of 8% of slaked lime catalyzed the geopolymerization reaction and promoted the dissolution of the crystalline phases as well as the amorphous phase of pozzolan. These improvements in the geopolymerization reaction resulted in the formation of new phases such as phillipsite-type calcium zeolite and calcium aluminosilicate hydrate, producing the best-performing geopolymer from a physico-mechanical point of view (Rc = 23.05 MPa, Vp = 2.21 km/s, D = 2.05 g/cm3, P = 5.13%, and A = 2.49%).

Development of ceramic porcelain stoneware pastes by the revalorization of Colombian clays subjected to bleaching process

The objective of this work has been the development of porcelain stoneware pastes by using clays from Colombia, obtaining a product exhibiting at least the same technical characteristics that the conventional one. For this purpose, different raw materials, including kaolinitic clays, feldspars, and pozzolans, have been studied from the central area of the country, specifically from the regions of Cundinamarca and Boyacá. Some of these raw materials, having contents of iron oxide above 1%, were subjected to both physical and chemical benefit processes in order to reduce the amount of this coloring oxide. The heap leaching method with oxalic acid at environmental temperature has obtained the best results, with a reduction in iron oxide content of 60 wt%. As for the need to achieve a high degree of sintering, in this work different fluxes such as natural pozzolan, nepheline-syenite and recycled glass have been used, showing that the introduction of these materials into the composition can provide the complementary fluxing and can also reduce the sintering temperature.

Alkali-activated binary concrete based on a natural pozzolan: physical, mechanical and microstructural characterization

This article presents the physical, mechanical and microstructural characterization of an alkali-activated binary concrete (AABC) based on a natural pozzolan (NP) of volcanic origin (70%) and granulated blast furnace slag (GBFS) (30%) cured at room temperature (25°C). A solution based on the combination of NaOH and waterglass (Na2SiO3·5H2O) was employed as an alkaline activator. The concrete design was obtained using a modified version of the “absolute volume” method (ACI 211.1). The performance of the AABC was similar and even superior to that of the reference concrete (OPC); e.g., it exhibited a compressive strength of up to 43.4 MPa at 360 days. These results demonstrate that the NP has potential for use in the industrial-scale production of these types of materials in the foreseeable future.

A new formulation for lightweight oil well cement slurry using a natural pozzolan

Fluid loss during cementing operation in depleted reservoirs or in deep wells of reservoirs with low breakdown pressure is a major concern for maintaining well integrity. To overcome this problem, the weight of cement slurry is usually reduced. Although various slurry formulations have been proposed during the last decade, the cost and availability of required additives is still an important concern, especially when the oil price is low. The objective of this study is to make lightweight cement slurry with a density of 105 lb/ft 3 , using the combination of natural pozzolan and API class G cement. In this study, a new formulation based on the optimum amount of a natural pozzolan and other additives is proposed. Based on the results of 24-hour compressive strength test and free water volume, 30% replacement of cement powder with pozzolan was selected as an optimal amount. Addition of more pozzolan into the slurry reduces its pumpability even at room temperature. Bottom-hole condition was simulated by increasing the temperature to 150°F and chemical additives were used to maintain the rheological properties of this slurry. Fluid loss control agent, dispersant and retarder were used at optimum values 0.5, 0.08 and 0.05 (%bwoc), respectively. The compressive strength of the cement rock was monitored at 3, 7 and 30 days, reaching 3528 psi after 30 days. Cited as : Larki, O., Norouzi Apourvari, S., Schaffie, M., Farazmand, R. A new formulation for lightweight oil well cement slurry using a natural pozzolan. Advances in Geo-Energy Research, 2019, 3(3): 242-249, doi: 10.26804/ager.2019.03.02

EFFECT OF INCORPORATING NANO ZEOLITE ON THE STRENGTH OF NATURAL POZZOLAN-BASED GEOPOLYMER CONCRETE

Natural pozzolan is a green and sustainable material, which has a strong potential for utilization in the geopolymer concrete. At room temperature, the development of strength in natural pozzolan based geopolymer concrete is fair, however, it is desirable, to have higher strength and to enhance the early age strength development. The effect of nano zeolite (NZ) as an additive to the mix by incorporating it at 3% and 5% by weight of natural pozzolan on the strength development and microstructural properties of natural pozzolan based geopolymer concrete mixes are presented. Scanning electron microscopy (SEM) was utilized to determine the morphology of the paste. The results indicated that 5% nanozeolite replacement resulted in superior strength and denser microstructure compared to other mixes. The addition of nanozeolite improved dissolution of source material in the alkaline activators and enhanced transformation of it to form polymeric compounds.

CONSTITUTIVE MODELS FOR PREDICTING MECHANICAL PROPERTIES OF NATURAL POZZOLAN-BASED ALKALI ACTIVATED CONCRETE

A large variety of mix design variables and environmental conditions in which alkali activated concretes (AAC) are cured, influences the nature and intensity of the binder formed. Equations developed for OPC-based concrete in various codes and published work may not accurately predict engineering properties of these AAC. AAC in this study was synthesized utilizing natural pozzolan (NP) in the presence of alkaline activators. Nano-SiO2 was added for enhancing the strength development at room temperature curing as NP is a low calcium precursor material. Development of compressive strength, flexural strength and modulus of elasticity were investigated. Using the data generated, two constitutive models, relating the compressive strength to flexural strength and modulus of elasticity were developed and compared with the equations specified in international codes for OPC-based concrete and previous studies in the area. The results show that the ACI 318, underestimates the flexural strength and overestimates the modulus of elasticity of alkali activated concrete. However, constitutive models developed in this study are in good agreement with the equations proposed in the previous works for AAC. Only the limited data available to date on the engineering properties of AAC cannot be used to establish robust constitutive relationships and more research is required in this area.

Alkali-activated binary mortar based on natural volcanic pozzolan for repair applications

The goal of this investigation was evaluate the potential of an alkali-activated binary mortar (AABM), based on a natural volcanic pozzolan (70%) and granulated blast furnace slag (30%), as a repair material. This evaluation focused on its physico-mechanical characterisation (compressive, flexural and splitting tensile strengths; modulus of elasticity; capillary water absorption; and shrinkage) and the measurement of its adherence to three class of OPC concretes (substrates) using pull-off tests. A mixture of NaOH and Na2SiO3 was used as alkaline activator. The compressive and splitting tensile strength of AABM were 34.8 MPa and 2.13 MPa at 28 days of curing, respectively. Its capillary absorption coefficient and modulus of elasticity were 0.5088 kg/m2h0.5 and 8.66 GPa respectively. The results of the pull-off test demonstrate the adherent nature of the AABM, which was promoted by the strength (quality) of the OPC substrate, with pull-off adherences of 0.75 MPa, 1.14 MPa and 1.24 MPa for class C25/30, C35/45 and C50/60, respectively. According to the results obtained and standard specifications (EN 1504-3), this material can be classified as a class R2-repair mortar.

Effect of Synthesized Calcium Carbonate Nanoparticles on Fresh and Mechanical Properties of High Volume Natural Pozzolan Mortars

Concrete with high levels of Pozzolan suffers from poor early age strength development and an extended setting time and may therefore lead to construction delays thus limiting its use in the concrete industry. The main objective of this study has been to evaluate the effectiveness of calcium carbonate nano-particles (CCNPs) on improving the fresh and mechanical properties of high volume natural Pozzolan (HVNP) cement mortars. At the beginning, CCNPs have been synthesized in a simple and inexpensive way, and then the optimum content of nano-CaCO3 has been determined based on the highest compressive strength achieved by ordinary Portland cement mortar with different proportions of CaCO3 nanoparticles. In the end, the determined optimum content has been used in order to evaluate the effect of nano-CaCO3 on the properties of HVNP mortars containing 40% and 60% natural Pozzolan as partial replacement of cement. Scanning electron microscopy (SEM) and X-ray diffractometery (XRD) techniques have been used in order to investigate the microstructure, the properties, and the compositions of the synthesized nano-particles and the cement-Pozzolan mortars. CCNPs have been synthesized efficiently via the simple precipitation method and suitable sonication process has been used to disperse CaCO3 nanoparticles. The results have indicated that nano-CaCO3 has increased the compressive strength of the Pozzolan-cement mortars, and the best result has been obtained at an optimum content of 1% nano-CaCO3. The addition of nano-CaCO3 to the HVNP mortar improved its setting behavior; on the other hand, it has decreased its workability. However, this reduction in the workability has been offset by an increase due to partial replacement of cement by HVNP. Blending nano-CaCO3 with HVNP (40 and 60% replacement levels) has compensated for the low compressive and flexural strength at early ages of HVNP mortars. Thus, it has proved to be an effective way for improving the mechanical properties of high volume natural Pozzolan-cement mortars. The XRD and SEM results have confirmed that nano-CaCO3 has improved the early strength development and the microstructure of HVNP mortars by making it denser with less pores.

Effect of Natural Pozzolan and Calcined Paper Sludge as Pozzolanic Additions on the Physicals and Mechanicals Properties of Heat Treated Self-Compacting Mortars

The aim of this research work was to investigate the effect of thermal treatment on strength development of self-compacting mortars (SCMs) based on two pouzolanic materials: Natural Pozzolan and calcined paper waste sludge, were used in the binders of SCMs. To evaluate the effect of heat treatment, a serial of the specimens were exposed to room temperature and another serial were exposed to heating regime (at temperature 60°C for a period of 14 h). The fresh and hardened properties of all mortars were evaluated. the obtained result show that the mechanical strength at 14 days of all mortar treated are almost similar or sometimes better to those not treated mortars tested at 28 days, which reduces the curing time for precast elements.