Natural Pozzolan Research Articles

Experimental analysis of lime putty and pozzolan-based mortar for interventions in archaeological sites

The study aims at defining and characterizing a specific restoration mortar for archaeological masonry structures made with traditional materials and to assess the suitability of the mixture compared to other mortars; such a goal is crucial to develop and define interventions in the archaeological sites. The mixture was defined to ensure compatibility with ancient materials and following frequently adopted recommendations at the site, specifically by using: (1) raw materials as similar as possible to the ancient ones; (2) traditional mix design. Therefore, the mixture was made with commercial lime putty CL 90-S type and natural Phlegrean pozzolan, i.e. volcanoclastic material collected from the volcanic area located in the West of Naples in Italy. The precious and limitedly available natural pozzolan used in the experiments resulted in an exclusive mortar which is very similar to the archaeological ones. The mortar has a binder to aggregate ratio 1:3 by volume, according to traditional techniques typically encountered in the ancient Roman city of Pompeii and Vesuvius surrounding area. The evolution of the flexural and compressive strength, elastic modulus, bulk density, open porosity and ultrasonic pulse velocity has been monitored for up to 200 days, based on standard procedures. Moreover, the hardening process was monitored with Differential Thermal Analysis up to 90 days, through the evaluation of phase transitions associated with dehydroxylation and decarboxylation, considering different depths from the external surface of the mortar. The achieved mechanical properties were compatible with those of lime-based mixtures for repair interventions of ancient masonry structures. Moreover, the mortar was found to be well-suited to mitigate cracking, showing a low ratio between its stiffness and load capacity compared to other typologies of mortars used for masonry restoration. Ultrasonic pulse velocity test proved to be a reasonable complementary method to monitor the evolution of the hardened properties of the mortar. Carbonation was found to be still progressing at 90 days. The data presented provide useful and reliable information to approach the complex process of restoration in archeological sites.

Effect of mineralogical composition of clinoptilolite-bearing tuffs on their performance as a natural pozzolan in cementitious systems

In this study, pozzolanic reactivity and strength activity of zeolitic tuffs containing similar amount of zeolitic phase (clinoptilolite) and different types and amounts of impurities were examined in order to understand the role of mineralogical composition in the efficiency of zeolitic natural pozzolans. Mineralogical and chemical compositions as well as the physical properties of the zeolitic tuffs were determined. Their pozzolanic reactivity were measured as depletion of calcium hydroxide in the pastes containing lime and zeolitic tuff, which is determined by thermogravimetric analysis. Furthermore, compressive strength of blended cement mortars prepared with 20% replacement of Portland cement by finely ground tuffs were determined at 7, 28 and 56 days of age. It was demonstrated that the type and amount of impurities in mineralogical composition of zeolitic tuffs are significantly effective on their early pozzolanic reactivity. Zeolite mineral content, however, is more determinative on long term reactivity. For a strength activity, mineralogical composition was clearly effective on the preparation of mortar samples, which depends on water requirement of zeolitic tuffs.

Producing of Lightweight Concrete from Two Varieties of Natural Pozzolan from the Middle Atlas (Morocco): Economic, Ecological, and Social Implications

Producing of Lightweight Concrete from Two Varieties of Natural Pozzolan from the Middle Atlas (Morocco): Economic, Ecological, and Social Implications

Natural pozzolan super-absorbent polymer: synthesis, characterization, and its application on plant growing under drought condition

Natural pozzolan super-absorbent polymer: synthesis, characterization, and its application on plant growing under drought condition

Experimental and Modelling of Alkali-Activated Mortar Compressive Strength Using Hybrid Support Vector Regression and Genetic Algorithm.

This paper presents the outcome of work conducted to develop models for the prediction of compressive strength (CS) of alkali-activated limestone powder and natural pozzolan mortar (AALNM) using hybrid genetic algorithm (GA) and support vector regression (SVR) algorithm, for the first time. The developed hybrid GA-SVR-CS1, GA-SVR-CS3, and GA-SVR-CS14 models are capable of estimating the one-day, three-day, and 14-day compressive strength, respectively, of AALNM up to 96.64%, 90.84%, and 93.40% degree of accuracy as measured on the basis of correlation coefficient between the measured and estimated values for a set of data that is excluded from training and testing phase of the model development. The developed hybrid GA-SVR-CS28E model estimates the 28-days compressive strength of AALNM using the 14-days strength, it performs better than hybrid GA-SVR-CS28C model, hybrid GA-SVR-CS28B model, hybrid GA-SVR-CS28A model, and hybrid GA-SVR-CS28D model that respectively estimates the 28-day compressive strength using three-day strength, one day-strength, all the descriptors and seven day-strength with performance improvement of 103.51%, 124.47%, 149.94%, and 262.08% on the basis of root mean square error. The outcome of this work will promote the use of environment-friendly concrete with excellent strength and provide effective as well as efficient ways of modeling the compressive strength of concrete.

PREDICTING THE STRENGTH OF CEMENT MORTARS CONTAINING NATURAL POZZOLAN AND SILICA FUME USING MULTIVARIATE REGRESSION ANALYSIS

In this study, mortars containing locally available natural pozzolan (NP) in Almadinah Almunawara, Kingdom of Saudi Arabia, were investigated as a partial substitute for sand or cement in mortars and silica fume (SF). The benefit of using local NP powder as a replacement for cement is that it reduces the carbon dioxide emission during the cement manufacturing process, whereas the benefit of using local NP as fine aggregates is that it reduces the density of the produced mortars and improves its properties because of its pozzolanic effect. Because of these reasons, there is a need to develop an effective predictive model to estimate the compressive strength of mortars with partial replacement of cement or sand with NP and with SF as a replacement for cement at 28 days. Data of 68 cubic specimens of 50 mm were established through experimental work with other researchers, and they were chosen to create a database for the proposed model. There were three input parameters: a) level of partial substitution of cement with NP powder, b) level of partial substitution of sand with NP, and c) level of partial substitution of cement with SF. The output parameter was compressive strength. Best correlations were obtained between the compressive strength and sand replacement with NP. To predict the compressive strengths of cement mortars containing NP and SF, multivariate regression models were proposed and compared to find the best one. It was concluded that the full quadratic model was the best model with highest correlation when compared with other proposed models.

The influence of brick dust and crushed brick on the properties of lime-based mortars exposed at elevated temperatures

Brick residues, such as brick dust and crushed brick, have been diachronically used in historic mortars, both as binders and aggregates. Their application served as a mean to increase the pozzolanicity of the matrixes, enhancing resistance to humidity, decrease the density of the mixtures and add special hue to the structures. On the other hand, the performance of traditional mortars at elevated temperatures is a significant aspect that should be taken into account, in order to assess the preservation state and residual capacity of historic structures, as well as to design fire resistant restoration materials, under the prism of compatibility. In this study, three mortar series were manufactured, based on lime (L), lime : natural pozzolan (LP-1:1 by weight), lime : natural pozzolan : brick dust (LPB-1:0.8:0.2 by weight). In order to envisage the role of crushed brick in the matrix, they substituted the 40% of natural aggregates in the same gradation (0–8 mm). The physico-mechanical properties of the mortars were tested at 28 and 90 days, while they were further exposed at elevated temperatures, concerning 200 °C, 400 °C, 600 °C, 800 °C and 1000 °C. Their post fire properties (physico-mechanical, microstructural) were recorded, so as to identify the preferable testing age of lime-based mortars and the impact of brick residues on their behavior. From the evaluation of the results, it was asserted that the 90d age seems to be more representative, while crushed brick and brick dust enhanced structural integrity throughout extreme temperatures.

Durability of Blended Cements Made with Reactive Aggregates.

Featured Application In this paper, blended cements are proposed as an effective means of meeting the needs of mitigating climatic change. This proposal is a two-pronged strategy, i.e., durable and sustainable. The pozzolanic reaction of four binders is assessed, which is related to an alkali–silica reaction (ASR). Thanks to the findings made here, mix-design optimization can be performed. Alkali–silica reaction (ASR) is a swelling reaction that occurs in concrete structures over time between the reactive amorphous siliceous aggregate particles and the hydroxyl ions of the hardened concrete pore solution. The aim of this paper is to assess the effect of pozzolanic Portland cements on the alkali–silica reaction (ASR) evaluated from two different points of view: (i) alkali-silica reaction (ASR) abatement and (ii) climatic change mitigation by clinker reduction, i.e., by depleting its emissions. Open porosity, SEM microscopy, compressive strength and ASR-expansion measurements were performed in mortars made with silica fume, siliceous coal fly ash, natural pozzolan and blast-furnace slag. The main contributions are as follows: (i) the higher the content of reactive silica in the pozzolanic material, the greater the ASR inhibition level; (ii) silica fume and coal fly ash are the best Portland cement constituents for ASR mitigation.

Improving the geopolymeric reactivity of Earth of Datça as a natural pozzolan in developing green binder

The purpose of the current study is to investigate the geopolymeric reactivity of volcanic tuff of Datça Peninsula (Earth of Datça) in Turkey and to evaluate whether it can be used as a green binder. The effects of alkali activator type, alkali hydroxide concentration, activator ratio, and curing conditions on the physical and mechanical properties were investigated. A combination of sodium silicate solution (SS) and potassium hydroxide (KOH) (12.5 M) with an activator ratio of 2.5 is selected as optimum activator type. Sealed curing at 90 °C and 90 ± 5% RH for 24 h provides the highest physical and mechanical properties. Results reveal that “Earth of Datça" as a natural pozzolan is a suitable precursor for the production of a geopolymer material with the properties of 2.0 g/cm3 bulk density, 5.4% water absorption ratio, 0.64 saturation coefficient, and 10.5 MPa compressive strength. The mortar produced in this research has promising characteristics to be used as a building material.

The Role of Glass Additives in the Properties of Lime-Based Grouts

Various types of additives have been diachronically used in historic mortars, whereas their use in lime-based grouts, used for the restoration of historic structures, is rather limited. In this study, an effort was made to investigate the performance of glass additives in grouts, consisting of lime and natural pozzolan. The additives concerned glass fibers (3 and 6 mm in length), glass beads and bubbles, added in a proportion 0.3–3% w/w of binders. Five grout compositions were manufactured and their properties at fresh and hardened states were tested. From the evaluation of the results, it was asserted that glass additives influenced the grouts’ performance in a favorable way. Their fresh state and physical properties were maintained or slightly improved, while there was a significant enhancement of the long-term mechanical characteristics of the mixes. Additionally, the adhesion capability of grouts was notably increased, which is a crucial aspect indicating their efficacy.

Enhanced Mechanical and Durability Performances of Low Cement Concrete with Natural Pozzolan Addition

Enhanced Mechanical and Durability Performances of Low Cement Concrete with Natural Pozzolan Addition

Synergic effect of nano-silica and natural pozzolans on transport and mechanical properties of blended cement mortars

The mechanism of the synergic effect of nano-silica and natural pozzolans on the structure of mortar samples in single, binary, and ternary blends was investigated. Mortar mixtures were prepared by replacing 2, 3, and 4% of cement mass with nano-silica and 15% with zeolite, trass or pumice as natural pozzolans with w/cm ratio of 0.485 and flow ranged from 14 to 16 cm. Compressive strength, electrical resistivity, chloride permeability, capillary absorption, and SEM analysis were carried out on mortar samples. Considering the results, nano-silica improved mechanical and durability properties of all mortar samples, but in binary samples, the nano-silica's effect on the mechanical properties improvements in the early ages was more pronounced. Interestingly, in ternary blends nano-silica had remarkable effect even at older ages. Furthermore, the combination of nano-silica and natural pozzolan showed a superior effect on the properties of mortars. As a consequence, the combined positive effect of three-component blends on the compressive strength of control samples was superior to the summation of the progressive effects of nano-silica and natural pozzolans in binary blends. It can be concluded that natural pozzolans amplified the ameliorating effect of nano-silica at older ages (90 days). The synergic effect of components was more pronounced with the increase in the percentage of nano-silica replacement and the selection of more active natural pozzolan. Finally, the ternary blends containing nano-silica and natural pozzolans outperformed the binary ones containing Portland cement and nano-silica not only in terms of reducing costs and negative environmental effects, but also in improving the mechanical properties and durability. Ternary mixtures incorporating 4% nano-silica together with 15% zeolite demonstrated the best results in all tests at the age of 90 days. Compared to the control sample, it improved compressive strength by 51.9% with changing from 48.2 to 73.2 MPa and chloride ions migration coefficient by 570.7% with changing from 16.7 to 2.5 *10 −12 m2/s.

Role of Alkalis in Natural Pozzolans on Alkali-Silica Reaction

Role of Alkalis in Natural Pozzolans on Alkali-Silica Reaction

Natural pozzolans-like Bahariya basalts used as alternative raw materials for cement clinker Portland

Mid-Tertiary volcanism in the Western Desert Egypt was associated with the opening of the Red Sea, a period of 30 Ma. Basalts are composed of plagioclase, pyroxene, and olivine minerals. Basalt used as natural volcanic pozzolans materials; represent large interest of researches as a real alternative to replace ordinary Portland cement (OPC). The present work was performed on six samples of experimental cement clinker, one with ordinary raw materials (limestone & shale) as a reference sample, and five others with various substance (limestone & basalts), which show the possibility of the utilization of natural pozzolan for maintainable construction material. The chemical, mineralogical composition and texture produced clinkers were determined by scanning electron microscopy (SEM-EDS), X-ray diffraction (XRD) and differential thermal analysis (DTA). It is concluded that the produced clinkers which made from basalt are coincidence ordinary Portland cement clinker. They are characterized by increasing in setting time, compressive strength and resistance to sulfate attack.

Freeze–Thaw Resistance of Nonproprietary Ultrahigh-Performance Concrete

In cold regions, early deterioration of concretes due to freezing and thawing is a major concern. This study determined the freezing and thawing resistance of ultrahigh-performance concretes (UHPCs) made with different pozzolanic-material types (Class F fly ash, natural pozzolan, and silica fume) and combinations, as well as varying steel fiber contents (0%, 2%, and 3%) and shapes (straight and hooked) using conventional fine aggregate. A total of thirty 28-day cured UHPCs were used to assess their mass loss after 70 freeze and thaw (F–T) cycles (48 h per cycle). The pre- and post-F–T compressive and splitting tensile strengths of the studied UHPCs were also obtained and examined. The outcome of this study revealed that the studied UHPCs displayed excellent resistance against freezing and thawing deterioration. The post-F–T-exposed UHPCs gained strength due to the availability of unhydrated pozzolanic materials, coupled with favorable curing environment. Among the utilized pozzolanic-material combinations, UHPCs made with silica fume and Class F fly ash, as a partial replacement for the cement, performed the best against freezing and thawing, whereas the companion mixtures containing only Class F fly ash to replace a portion of the cement showed the highest mass loss. The addition of straight steel fibers had a more positive influence on the freezing and thawing resistance than hooked fibers.

Investigative Study of Partial Replacement of Cement with Bio-Cement, Fly Ash and Natural Pozzolans

Concrete is usually a combination of cement, coarse particles (aggregates and Sand) and water. It is used to design and improve the infrastructures.It is used to design and improve the infrastructures. Concrete has many advantages and disadvantage. The main property that is characteristic to a concrete’s workability is its compressive strength. Only through this single test, one can judge if cementing has been done appropriately. Possible advancements for development include the use of non-traditional and creative materials, and the reuse of waste materials with a specific end goal to replenish the absence of specific assets and to discover alternative ways to monitor the Earth..This investigation concentrate on Compressive strength, flexural and split tensile strength of Conventional Concrete (CC) and Class C fly ash remains with bio-cement and natural pozzolans to consider the impact of bio-concrete with blend extents of 0%,0.25%,0.5%,1% and 1.5% on quality properties. Moreover, effective self-healing usually occurred due to the use of polymers, microorganism and additional cementing material. It is the key issue to find out the self-healing efficiency’s effect to sealing the crack width successfully. And good resistance was observed during the bacterial chemical process against the freeze and thaw attacks.

Exploratory of the freezing–thawing behavior of clay and steel slag mixtures

Stabilization of clayey soil has been studied by mixing different additives to the soil to increase its strength and durability. Recently, there has been an increasing interest in the stabilization of soils with natural pozzolans. Nevertheless, very few articles have investigated the impact of basic oxygen furnace (BOF) slag additives under freeze–thaw cycling. This study presents the results of an experimental research study on the durability behavior of clayey soils treated with BOF slag. In this study, the effects of clay soils on the bearing value were investigated by adding 3%, 6%, 9%, 12%, 15%, and 20% BOF slag to the clay mineral sample within the scope of ASTM D-5918 tests. California bearing ratio (CBR) tests were then applied before and after freezing–thawing processes to the samples prepared at these optimum conditions. The relationship between the determined freezing and swelling speeds and the strength losses of the soil samples after freeze–thawing processes were investigated. For this purpose, eight mixtures with different geotechnical properties were subjected to freeze–thaw experiments on a total of 24 soil samples, each of which was repeated three times. Results show that the addition of steel-making slag to clay soils lead to favorable effects on freezing–thawing behavior. The effects of BOF slag on the clay sample after the freezing and thawing cycle were investigated and interpreted by considering their macro and micro phase structure. The findings indicate that using BOF slag has positive effects on strength and durability of clayey soil.

Effects of cyclic carbonation and chloride ingress on durability properties of mortars containing Trass and Pumice natural pozzolans

AbstractWith an increase in CO2 emission, corrosion of reinforcement as a result of carbonation has become more significant to researchers besides corrosion due to chloride ion ingress. Many structures are exposed to coupled effects of carbonation and chloride attack; therefore, investigating the effect of this combined attack on the durability of concrete is a vital subject. Also, the use of supplementary cementitious materials (SCMs) has become more common due to their contribution to concrete's properties. In this study, the combined effect of chloride attack and carbonation on the durability of mortars containing SCMs was studied. Two natural pozzolans (Pumice and Trass) were used as cement replacements in mortar mixtures with three w/b ratios of 0.485, 0.44, and 0.4. Four exposure conditions, namely normal (immersed in lime‐saturated water), chloride attack, carbonation, and cyclic carbonation and chloride attack were considered. Compressive strength, carbonation and chloride penetration depth, capillary water absorption, surface electrical resistivity, and chloride diffusion tests were performed. The results indicate that while carbonation depth is reduced in the combined attack environment, it imposed a more severe corrosive condition in comparison to pure immersion in saline water by increasing the diffusion coefficient up to 500%. Also, addition of pozzolans showed the potential to reduce the diffusion coefficient of the mortars as much as 76% pointing out that mortars without pozzolans were more vulnerable to this combined attack environment. Furthermore, cement replacement with Trass and reduction of w/b showed to be beneficial in reducing the destructive effects of the combined environment.

Eco-House Prototype Constructed with Alkali-Activated Blocks: Material Production, Characterization, Design, Construction, and Environmental Impact.

The interest of the construction industry in alkali-activated materials has increased to the extent that these materials are recognized as alternatives to ordinary Portland cement-based materials in the quest for sustainable construction. This article presents the design and construction of a prototype of an eco-friendly house built from concrete blocks produced using alkali activation technology or geopolymerization. The prototype meets the requirements of the current Colombian Regulations for Earthquake Resistant Buildings (NSR-10) and includes standards related to the performance of the materials, design, and construction method for earthquake-resistant confined masonry of one- or two-story buildings. The alkali-activated blocks were obtained from different precursors (aluminosilicates), including a natural volcanic pozzolan, ground granulated blast furnace slag, fly ash, construction and demolition waste (concrete, ceramic, brick, and mortar), and red clay brick waste. The physical-mechanical characterization of the alkali-activated blocks allowed their classification according to the structural specifications of the Colombian Technical Standard NTC 4026 (equivalent to ASTM C90). The global warming potential (GWP) or “carbon footprint” attributed to the raw materials of alkali-activated blocks was lower (25.4–54.7%) than that of the reference blocks (ordinary Portland cement concrete blocks). These results demonstrate the potential of alkali-activated materials for application in the construction of eco-friendly houses.

The Potential to Replace Cement with Nano-Calcium Carbonate and Natural Pozzolans in Cemented Mine Backfill

The effectiveness of mine backfilling depends on the properties of its constituents. The high cost of cement, which is commonly used as a binder in mine backfill, has led researchers to seek alternatives to partially replace it with other binders. This study investigated the potential to use nano-calcium carbonate (NCC) and natural pozzolans (zeolite and pumice) along with Portland cement (PC) in mine backfill. Two types of experimental samples were prepared: (1) gold tailings and silica sand to investigate the effect of NCC and (2) nickel tailings to investigate the effect of natural pozzolans. The unconfined compressive strength (UCS) was measured for samples cured for up to 56 days. Moreover, selected samples were subject to mercury intrusion porosimetry to investigate microstructural properties. Results show that addition of NCC did not improve the UCS of backfill prepared with gold tailings and cured for 28 days, whereas a dosage of 1% NCC in backfill samples prepared with silica sand improved UCS by 20%, suggesting that the gold tailings negatively affected strength development. Natural pozzolans, in particular, 20% zeolite, had 24% higher UCS after 56 days of curing compared to samples prepared with PC and thus have the potential to partially replace cement in mine backfill.