Natural Pozzolanic Materials Research Articles

Effect of Ground Diatomite on Early Strength of Self-Compacting Mortars

Portland cement fabrication is a significant factor that increases the amount of carbon dioxide released into nature. For this reason, it is very important to use natural and waste materials with pozzolanic properties instead of portland cement. In this article, the usability of diatomite rock, a natural pozzolanic material that can be substituted with portland cement, in the manufacture of self-compacting mortar was studied. In the experimental study, prismatic specimens with dimensions of 40 × 40 × 160 mm were used to examine the impact of ground diatomite on the early age mechanical properties of self-compacting mortar; it was produced by replacing 0%, 5%, 10%, 15%, 20% of diatomite with portland cement, respectively. The slump-flow test to obtain self-compacting mortar was conducted according to the European Federation of Specialized Construction Chemicals and Concrete Systems guidance. Specimens prepared using 0%, 5%, 10%, 15% and 20% diatomite were cured in water at 23±2 ̊C temperature for 3 days. 3-day (early age) flexural and compressive strength worths were gained for the samples whose curing period was completed. As a result of this experimental study, it was specified that the highest strengths were in the series containing 5% diatomite, exceeding the reference samples. Additionally, it has been determined that mechanical strength decreases when the diatomite ratio in mixtures is more than 5%.

Examination of the Physical–Mechanical Properties of Sustainable Self-Curing Concrete Using Crushed Ceramic, Volcanic Powder, and Polyethylene Glycol

This study investigates the properties of sustainable self-curing concrete (SSC) by adding volcanic powder (VP), crushed ceramic (CC), and polyethylene glycol 6000 (PEG). VP and CC are prepared from volcanic ash, as a natural pozzolanic material, and construction waste, respectively. PEG is used as an inner-curing agent. Twenty-six concrete mixtures are prepared using VP at 5%, 10%, 15%, and 20%, CC at 50%, and PEG at 1%, 1.5%, and 2% and tested after 7, 28, and 56 days. Mechanical, workability, and durability characteristics are evaluated using different tests. The bond and cohesion between aggregates and mortar are tested using a scanning electron microscope (SEM). The results show that the optimum replacement mix for enhancing strengths, by producing C-S-H, of the studied SSC is 10% VP and 1.5% PEG. This improved the compressive, tensile, and flexural strengths of SSC by 54.5%, 60.7%, and 34.9%, respectively, compared to a reference mix. Adding CC enhances the compressive strength of SSC by 41.6% and 11.5% and decreases chloride penetration by 10% and 9.1% compared to control mixes. PEG improves the mechanical, workability, and durability characteristics of SSC even with the addition of 1%. The obtained results reveal the possibility of using VP and CC in producing SSC.

Effects of raw and different calcined bentonite on durability and mechanical properties of cement composite material

Bentonite is a natural pozzolanic material mostly composed of SiO2 and employed in cementing materials for the reduction of cement consumption and CO2 emission besides improving performance of cement composite material by consuming portlandite to form extra C-S-H gel. So, many researchers studied on partial replacement of bentonite to improve concrete performance. However, bentonite mostly exists as a consolidated form that needs treatment for activation of pozzolanic reactivity to improve performance of cement composite materials. However, it is not well known how different replacement of raw and calcined bentonite affects performance of cementing materials in different hazardous environment. Hence, the present study identified the most influential replacement of bentonite, evaluating different calcined and raw bentonite in environments of acids, salt, and elevated temperature in addition to assessing the mechanical and physical properties of cement composite material. So, the results indicate that the employment of raw and calcined bentonite reduces the fresh bulk density, improves compressive strength, and Vicker hardness at 28 days, reduces the mass loss due to 56 days immersion in 5% HCl, 10% NaCl, and 5% HNO3 compared to the control mixture. Moreover, the employment of calcined bentonite at 800 °C significantly improved the durability and mechanical properties of cement composite materials compared to the control mixture. Specifically, replacing bentonite calcined at 800 °C for 3hs by 20% has the highest compressive strength than all samples after 28 and 56 days. Besides these, the study reveals that the corrosion potential of steel bars embedded in the mortar is reduced as the proportion of raw and different calcined bentonite increases. Generally, the employment of calcined bentonite is very beneficial to get improved performance on mechanical and durability properties of cement composite materials.

Diamine functionalized volcanic tuff: a promising CO2 adsorbent

AbstractBackgroundGreenhouse gases, especially CO2, are primary factors for global warming and CO2 emissions continue to increase annually. Many legislations and agreements have been made to decrease, or at least stabilize, CO2 concentrations in the atmosphere. Moreover, promising CO2 capture technologies, such as adsorption using solid sorbents, have been developed and shown high CO2 adsorption capacity.ResultsVolcanic tuff, a natural pozzolanic material, was evaluated as a solid CO2 adsorbent in this study. Following pre‐treatment of the volcanic tuff with HCl solution, CO2 adsorption experiments were conducted by thermogravimetric analysis (TGA). Diamine functionalization of the volcanic tuff was carried out using amine based compounds with different chain lengths, including ethylenediamine, 1,4‐diaminobutane and 1,6‐diaminohexane. The CO2 adsorption capacity of the volcanic tuff was significantly enhanced in the presence of 1,6‐diaminohexane. Maximum CO2 adsorption capacity was determined to be 42.94 mg g−1 with 70 wt% 1,6‐diaminohexane loading. The CO2 adsorption capacity of the 1,6‐diaminohexane functionalized volcanic tuff decreased with increasing temperature, which was an indication of exothermic adsorption. Adsorption–desorption cycles revealed that the 1,6‐diaminohexane functionalized volcanic tuff was a reusable CO2 adsorbent with high stability.ConclusionThe results show that the low cost, eco‐friendly, and highly stable diamine functionalized volcanic tuff can be considered a promising adsorbent for CO2 capture. © 2023 Society of Chemical Industry (SCI).

Mechanical properties of eco-friendly cement based composite mortars plastic fiber reinforced partially replaced by natural pozzolan and marble waste

This research presents a study on the mechanical properties of mortar specimens reinforced with plastic fibers incorporating natural Moroccan pozzolan and marble waste as partial substitutes for cement. Cement is a widely used material, but its production contributes significantly to CO2 emissions. And reducing the carbon footprint of materials without increasing costs is a critical challenge. Hence, numerous studies have investigated the partial or complete substitution of cement. Moroccan pozzolan, a natural pozzolanic material, offers an alternative to energy-intensive cement production. Marble waste, an industrial byproduct generated during the sawing, shaping, and polishing of marble, poses a significant environmental threat. Likewise, the issue of environmental pollution caused by plastic has received lot of attention, and the ideal solution recommended is recycling. In this sense, twenty-one mixes were synthesized and evaluated to explore the mechanical properties of the fiber-reinforced mortars based on natural pozzolan and marble waste added at different weight percentages (5–5/10–5/5–10/15–0/0–15/7.5–7.5) as a partial replacement for cement and 1% and 2% plastic fibers, based on the mortar volume. The hardened mortar mixtures were tested for compressive strength determined after 7 and 28 days, and flexural strength by a three point bending machine. The test results revealed that the mortar specimens containing marble waste and natural pozzolan exhibited the highest compressive strength. The addition of plastic fibers positively influenced the compressive and flexural strength of the mortars. Optimal percentages of natural pozzolan, marble waste, and plastic fibers were identified. The best-performing mixture achieved a compressive strength of 18.67 MPa with 5% pozzolan, 5% marble waste, and 2% plastic fibers added to the mortar mix. This approach not only addresses the uncontrolled disposal of plastic and marble waste but also provides an opportunity to utilize abandoned natural resources, creating more durable and environmentally friendly composite mortars.

Improvement of the Mechanical Properties of Mortars Manufactured with Partial Substitution of Portland Cement by Kaolinitic Clays

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.

Evaluation of zeolite as supplementary cementing material

The current paper researches the impacts of including zeolite in M30 grade of concrete mix as a plausible type of pozzolanic material. Pozzolans comprise of incredibly fine particles of siliceous and aluminous based materials. They rarely possess little or no binding ascribes, but in the presence of water, they respond with calcium hydroxide to create cementing compounds. Zeolite is one among the natural pozzolanic materials which has been successfully utilized to supplant the cement content fractionally in preparation of mortar or concrete elements. The objective of this experimentation is to replace cement content with zeolite which is accessible in the vicinity, and to concentrate on its impact on the mechanical properties of concrete. The construction industry has been hit hard with skyrocketing prices and severe shortage of natural river sand across many parts of the nation. Hence an attempt is also made to utilize manufactured sand instead of natural river sand. The incorporation of zeolite up to the degree of 15% resulted in an optimum magnitude of mechanical strengths of the concrete blend.

The technology of ancient lime mortars from the Żejtun Roman Villa (Malta)

Studies on original mortars can greatly assist archaeological interpretations, as elucidating the composition of such mortars gives clues on the origin of raw materials, manufacturing technology, and the construction phases of a site. This article presents the multi-analytical characterisation of 24 mortars and plasters from the Żejtun Roman Villa, Malta, to support archaeological hypotheses on the history of the construction of the site. The samples, belonging to at least three distinct phases included in the stratigraphy of the Żejtun archaeological site, were analysed using polarised light microscopy (PLM), scanning electron microscopy (SEM–EDS), X-ray diffraction (XRD), thermogravimetry (TGA/DSC), X-ray fluorescence (XRF), ion chromatography (IC), and stable isotope analysis (13C and 18O). The assessment of the results through correlations with archaeological evidence identifies five types of mortars with varying degrees of hydraulicity. These are associated with different development phases of the site and distinctive uses and were mainly produced using local resources, except in the Early Roman period when natural pozzolanic raw materials started being used. As there are no natural pozzolans on the Maltese Islands, it is hypothesised that the pozzolanic materials used as aggregate in the mortars were imported to the Islands from neighbouring volcanic regions. This volcanic aggregate was especially abundant in one of the mortar types, which was used mainly as a bedding mortar for floors.

The influence of cement substitution with rice husk ash on high-strength concrete

High-strength concrete is a crucial construction material in modern infrastructure development. It involves replacing some conventional raw materials with environmentally friendly alternatives to enhance concrete quality. Rice husk ash (RHA) is an agricultural waste that contains natural pozzolanic materials capable of improving the mechanical properties and strength of concrete. The use of rice husk ash (RHA) in high-strength concrete mixtures has the potential to reduce cement consumption and enhance crack resistance. The aim of this study is to investigate the impact of substituting cement with rice husk ash (RHA) and adding superplasticizer on the compressive strength of concrete. The targeted concrete strength is 45 MPa with variations of rice husk ash substitution at 5%, 10%, and 15% by weight of cement. This research obtained the compressive strength of concrete at 7 days with variations of 5% at 30.59 MPa, 10% at 25.20 MPa, and 15% at 20.77 MPa. Subsequently, at 14 days, the compressive strength increased with variations of 5% at 37.48 MPa, 10% at 27.56 MPa, and 15% at 22.23 MPa. The compressive strength continued to rise at 28 days, with variations of 5% at 44.26 MPa, 10% at 29.36 MPa, and 15% at 29.19 MPa.

The Effect of Diatomaceous Earth Addition on CBR Values of Glee Geunteng Soil in Aceh Besar, Aceh Province, Indonesia

The soil which is the platform often used for construction activities needs the strength to resist loads. However, its physical and mechanical properties are sometimes naturally limited and this implies there is a need for improvement and stabilization. Therefore, this study uses diatomaceous earth, which is a natural pozzolanic material classified as a type of Supplementary Cementing Materials (SCM), as an additive. The chemical stabilization was conducted by mixing the soil with stabilizing materials such as cement, lime, fly ash or others that have the ability to change the chemical composition and combination of soil. It is important to note that diatomaceous earth has similar properties as other pozzolanic materials such as fly ash and metakaolin powder and this is the reason it is expected to function as a soil stabilizing agent needed to improve soil properties. This study was conducted using the soil from Glee Geunteng in Peukan Bada as well as the diatomaceous earth obtained from Lambeureunut Village, Aceh Besar Regency, Aceh Province, Indonesia. The main purpose was to determine the California Bearing Ratio (CBR) value of the Glee Geunteng soil mixed with diatomaceous earth at 5, 10, 15, and 20% dry weight of the soil. The CBR test consisted of unsoaked CBR, soaked CBR testing at 4 days, and swelling properties of CBR with a variety of diatomaceous earth mixtures. Glee Geunteng soil was classified as A-6 Group Index 3 based on the AASHTO soil classification and as the SC (silty clay) soil according to the USCS classification. The results showed that the unsoaked CBR value reduced from 35.96% for the natural Glee Geunteng soil to 31.65% for the soil mixed with 20% diatomaceous earth material. A similar trend was observed for the soaked CBR value with a reduction from 15.57% to 6.98%. The decrease in CBR value was perceived to be caused by the very small silica content (SiO2 ) in diatomaceous earth material with 42.09% compared to the 86% in the material obtained from another source in the previous research by Hidayati.

Effect of magnetized water on characteristics of sustainable concrete using volcanic ash

Renewable resources of sustainable materials that can be functioned of supplementary cementitious materials are a critical in order to minimize extra waste, especially in construction mutter. Volcanic ash (VA) is one of natural pozzolanic material that can be considered important in Egypt. The main aim of the current study produces an eco-friendly concrete using the natural material. For that this study experimentally deals with developing a sustainable concrete using VA, as a supplementary cementitious material, and assesses their characteristics with and without using a magnetic field. Five ratios of VA (0, 5, 10, 15 and 20 %) as a replacement of cement were used to prepare thirty mixes. Magnetized water (MW) was generated using two different intensity values, 1.6 and 1.4 Tesla (T), to assess different magnetization methods. In the current study, five different MW methods were carried out based on the water pass direction and speed using a designed device. The results show that: (1) VA is thermally stable up to 800 °C, (2) The best ratio of VA for producing volcanic concrete is 5 % with tap water and MW, (3) The long direction and high speed of water through 1.6 then 1.4 T (which generate more friction between water and inner surface of pipes) is the best to produce more influence MW for volcanic concrete; this method improved pH of used water by 12.6 %, (4) The workability of volcanic concrete increases by about 15 % with MW, (5) Compressive strength of concrete is improved by 24 % at 7 days with 5 % VA and tap water, (6) Compressive strength increases with MW and 5 % VA up to 22 % and 33 % at 7 and 28 days, respectively. The results reveal that volcanic concrete characteristics are associated with the thermal stability of VA and the improved pH of used water.

Micro-structural and mechanical properties of PVA fiber reinforced engineered cementitious composite incorporating natural and artificial pozzolanic materials under different temperatures

• The pozzolans' contents significantly affect the tensile strain capacity of the ECC. • Using fly ash, GGBS and zeolite can improve tensile behavior of the ECC. • The GGBS based ECC has better tensile stress–strain behavior. • At the temperatures above 50 °C, the mechanical properties of the ECC decrease. • ANN and MLR can predict the mechanical properties of the ECC with high accuracy. Engineered cementitious composites (ECC), which have high toughness and tensile ductility, as well as multiple fine cracking, satisfy the high safety and durability criteria in the development of sustainable infrastructures. The effect of different temperatures on the mechanical characteristics of polyvinyl alcohol (PVA) reinforced ECC (PVA-ECC) was examined in this work. A study was conducted to compare the modulus of elasticity, tensile strength, and compressive strength of samples containing various dosages of three available pozzolans: zeolites (ZE), fly ash (FA), and ground granulated blast furnace slag (GGBS), as well as silica fume (SF). Scanning electron microscopy was used to examine the microstructure of PVA-ECC samples subjected to various high temperatures (SEM). For 1 h, all specimens were exposed to temperatures of 150, 100, 50, and 20 °C. The experimental findings revealed that when the temperature rises to 50°, all three mechanical parameters, modulus of elasticity, tensile strength, and compressive strength, increase, then drop. The study of the microstructure of PVA-ECC reveals a basic explanation for the loss of macro mechanical characteristics. Finally, using ANOVA analysis, the relationship between independent parameters such as the age of the sample (AS), temperature (T), and water to pozzolan materials (W/P), and dependent parameters (i.e., compressive strength, tensile strength, and modulus of elasticity) was evaluated, and the multivariate linear regression (MLR) and the artificial neural network (ANN) were shown to be useful for modeling.

Properties and Durability of Cement Mortar Using Calcium Stearate and Natural Pozzolan for Concrete Surface Treatment.

Applying a concrete surface treatment method (epoxy or primer) can prevent water from penetrating concrete through surface pores. However, if the concrete surface is damaged, the subsequent reconstruction can be expensive and time-consuming. Concrete that is resistant to internal and external water has been extensively developed and used to supplement the surface treatment method. Herein, we prepared specimens by mixing cement mortar with fatty-acid-salt-based calcium stearate attached to two natural pozzolanic materials—diatomite and yellow clay. The physical tests measured (1) the air content, (2) flow test, (3) compressive strength, and (4) activity Factor. Durability experiments were performed on (1) the contact angle, (2) chloride ion diffusion coefficient, and (3) water absorption test. The results revealed that the compressive strength of concrete decreased as the calcium stearate content increased. Furthermore, it was confirmed that the contact angle of the test piece using the pozzolanic substance and calcium stearate was twice as high. It was confirmed that the sand test specimen had the highest water absorption rate, and the DT3% had the lowest. (Sand%: 11.8 > OPC: 6.5 > DT3%: 2.4), the chloride diffusion coefficient also showed similar results. (Sand%: 12.5 > OPC: 8.4 > DT1%: 8.8)Due to its unique insolubility, calcium stearate retards hydrate formation when mixed alone and negates compressive strength loss when combined with pozzolanic mixtures rich in SiO2 and Al2O3. Furthermore, the ideal method for producing water-resistant cement mortar is to evenly disperse calcium stearate in the porous powder of cement mortar.

Optimization of reinforced bentocrete column parameters under eccentric compression

Replacing cement with pozzolanic materials to some extent in construction is found to be one of the sustainable approaches in construction industry. Pozzolanic materials of industrial origin like fly ash and GGBS will have to be replaced with natural pozzolanic materials once the world moves towards renewable energy sources. Bentonite is one such pozzolanic clay materials which is rich in SiO2 content. The performance of bentonite modified concrete (Bentocrete) was assessed in the present study. Bentocrete exhibited better performance than OPC concrete in terms of strength durability. However, no test results are available on columns using Bentocrete. The evaluation of Bentocrete in a structural component is essential to find out its applications as structural concrete. So, a research program was undertaken to investigate the strength and behavior of reinforced Bentocrete columns under eccentric compression and providing the optimal solutions. The experimental study of this investigation consisted of tests on forty columns with Bentocrete and OPC concrete in eight series. All the specimens were nominally of same length and cross-sectional dimensions. The performance of Bentocrete columns in terms of load carrying, deflection, compressive strain and resistance to cracking was better with 5% replacement, on par with OPC columns, and slightly less than OPC columns with 15% replacement. A novel optimization model was developed based on the experimental data; optimization was performed using Response Surface Methodology (RSM). The variables of the study are bentonite substitution (0%, 5%, 10% and 15%), longitudinal reinforcement ratio (2.09 and 3.04) and eccentricity (0, 0.1, 0.3, 0.5 and 0.7). Ultimate load, transverse deflection at mid-span, and compressive strain were considered as responses influenced by these variables. The models generated from RSM were valid with statistical significance in all the factors considered. The optimum solutions were proposed with desirability of 1.0. Suitability of use of Bentocrete in structural concrete was confirmed by this investigation.

Engineering Properties of Mortar Containing Calcined Local Clay as a Supplementary Cementitious Material

The use of natural and artificial cementitious and pozzolanic materials is gaining importance and become an essential component in today's cement-based materials. Supplementary cementitious materials are recognized to provide an added value to concrete/mortar both for mechanical and durability performances as well as to their sustainability with reduced environmental impacts of the construction industry. Developing locally produced natural pozzolans is vital in the efforts towards enhancing the construction industry's sustainability. Locally extracted raw soil from Nizwa city (NZS) in Oman was ground, calcined, characterized, and used at 10%, 25%, 35%, and 50% as partial replacement of ordinary Portland cement (OPC) in mortar mix. The blend mortar was assessed with regard to compressive strength and durability properties. The obtained results indicate a slight reduction in the flow of the blended mixes. An insignificant effect of the NZS replacement on the hardened mortar's density was observed while slightly reduced strength at 1-day and 28-day for some replacement levels. Meanwhile, around a 1% reduction in the porosity and absorption. Blended cement mortar with NZS demonstrated adequate resistance to sulphuric acid and (sulphate + chloride) exposure with lower weight and strength losses compared to the control mortar.

Performance of natural clinoptilolite zeolite in the cementitious materials: A comparative study with metakaolin, fly ash, and blast furnace slag

Different pozzolanic materials possess different chemical and mineralogical compositions and could show different performances in the blended hydrated cementitious materials. In the present study, the performance of natural clinoptilolite zeolite, a popular silica-alumina-based natural pozzolanic material in recent times, was investigated to compare with other commonly available silica-alumina (metakaolin) and silica-calcium (blast furnace slag, and Class C-fly ash) enriched pozzolanic materials in the blended cementitious system. The performance was evaluated on fresh (workability), hydration (setting time and chemical shrinkage), and mechanical (compressive strength) properties of hydrated cementitious materials. Thermogravimetric analysis (TGA) was accomplished to measure the pozzolanic activities of all respective pozzolanic materials. The water absorption, porosity, and chloride ion penetrability of concrete via surface resistivity were measured as the transport properties. For the durability properties, drying shrinkage and the alkali-silica aggregate reaction (ASR) of mortars were investigated. Results revealed that the addition of clinoptilolite zeolite reduced the workability but accelerated the setting time of hydration compared to other pozzolanic materials. Zeolite particles increased the volume of chemical shrinkage compared to other pozzolanic materials due to the particle packing effects. The addition of zeolite led to decreasing the compressive strength due to relatively slow pozzolanic activity compared to the other pozzolanic materials as measured by the TGA analysis. Zeolite blended samples had a similar water absorption and porosity compared to the metakaolin, slag, and fly ash blended samples. All pozzolanic materials were equally effective in reducing the drying shrinkage, while zeolite particles attributed to the internal curing capacity. Overall, clinoptilolite zeolite exhibited excellent resistance to chloride-ion penetrability due to the finer pore size, and a reduction in deleterious expansion due to ASR through cation exchange compared to slag and fly ash particles.

Optimization of bentonite modified cement mortar parameters at elevated temperatures using RSM

The inaccessibility of industrial wastes necessitated the search for natural pozzolanic materials. This paper deals the optimization of bentonite utilization in cement mortar at elevated temperatures using response surface methodology. The substitution of calcined bentonite (0%, 10%, 20% and 30%) and temperature exposure (24°C, 200°C, 400°C and 600°C) were taken as variables. The compression strength and strength activity tests for all mixes were carried out for bentonite. Design Expert 11.0 version was utilized for modelling using RSM. The peak compressive strength was displayed by 20% replaced bentonite calcined at 200°C cement mortar after 28 days curing. Strength activity was improved upon increasing the percentage of bentonite calcined at 200°C. The generated models from RSM are significance in all the factors considered. Optimum solutions were proposed with more than 0.90 desirability.

Investigation of Dehydroxylated Sodium Bentonite as a Pozzolanic Extender in Oil-Well Cement

Summary Fly ash, which is a pozzolan generated as a byproduct from coal-powered plants, is the most used extender in the design of lightweight cement. However, the coal-powered plants are phasing out due to global-warming concerns. There is the need to investigate other materials as substitutes to fly ash. Bentonite is a natural pozzolanic material that is abundant in nature. This pozzolanic property is enhanced upon heat treatment; however, this material has never been explored in oil-well cementing in such form. This study compares the performance of 13-ppg heated (dehydroxylated) sodium bentonite and fly-ash cement systems. The raw (commercial) sodium bentonite was dehydroxylated at 1,526°F for 3 hours. Cement slurries were prepared at 13 ppg using the heated sodium bentonite as partial replacements of cement in concentrations of 10 to 50% by weight of blend. Various tests were done at a bottomhole static temperature of 120°F, bottomhole circulating temperature of 110°F, and pressure of 1,000 psi or atmospheric pressure. All the dehydroxylated sodium bentonite systems exhibited high stability, thickening times in the range of 3 to 5 hours, and a minimum 24-hour compressive strength of 600 psi. At a concentration of 40 and 50%, the 24-hour compressive strength was approximately 800 and 787 psi, respectively. This was higher than a 13-ppg fly-ash-based cement designed at 40% cement replacement (580 psi).

Effect of the use of volcanic pozzolan from Mbepit Massif (West-Cameroon) on the mechanical properties of mortar and composite cements production

The rise in industrialization and infrastructural development is increasing leading to a constant need for construction materials; however, some of these materials continue to pose a problem to the concerned environments. There is a need to search for materials that will reduce environmental degradation and ensure sustainability. Natural pozzolanic materials possess certain characteristics such that their use in mortar and cement production could reduce the emission of carbon dioxide (CO2) due to the transformation of limestone (CaCO3) into lime for production of Portland cements. Colossal deposits of volcanic pozzolan outcrop in the Njimbouot II locality and the characterization of those materials is vital in deciphering their suitability in cement production as a construction material for sustainable development. Grinding is the only treatment performed on pozzolans in order to increase their specific surface area and reactivity. The rate of substitution of cement with pozzolan in the samples varied from 0%, 10%, and 15% to 25%. Mechanical tests were carried out after 7, 28 and 90 days on mortar specimens (4 × 4 × 16 cm3). Results revealed the presence of amorphous phases. The activity index obtained was approximately 75% and the lapilli and volcanic ash in this area are classified as pozzolans (classification ASTM C618). Regardless of the rate of substitution, the mechanical proprieties of mortars are observed to increase with age. The compressive strength values changed from 33.72 to 52.5 MPa while the flexural strength evolved from 5.62 to 8.29 MPa revealing that the Njimbouot II Pozzolan are advantageous in the manufacture of ecological cements.

Tagabo Volcanic Ash as Cement Replacing Materials

This paper aims to assess the pozzolanic characteristics of the volcanic ash obtained from Jebal Tagabo (Tagabo Mountains) in western Sudan (North Darfur State) as potential Supplementary Cementitious Materials for use in blended cement and concrete. Four natural Pozzolanic materials samples have been obtained; the first is volcanic ash from the Garma region (TG1VA), the second from the Mabo region (TG2VA), the third from the Mawo region (TG3VA) and the last from the Daim Sanosi region (TG4VA). This study has investigated the chemical and physical characteristics of the samples and their pozzolanic activities with Ordinary Portland cement (OPC) at different substitution levels of cement by weights, which are 10, 20, 30, 40, and 50%. And the results of chemical analysis show that all samples can be classified as Class N according to the American standard ASTM C618. The strength activity indices of the four samples at 20% level were found to be 75, 84, 89, and 83% respectively. These results indicate that the Jebal Tagabo Pozzolans are potential supplementary cementitious materials for use in blended cement.