Pozzolanic Cement Research Articles

Experimental Study about the Influence of Storage Conditions of Bulk Cement on the Early-Age Stiffness Evolution of Cementitious Pastes

The effects of uncontrolled storage and curing temperature on the early-age mechanical behavior of cement are under-investigated issues, and the few available studies in the literature analyze their influence mainly from a chemical-physical point of view. The present study, on the contrary, aims at studying the effects of temperature and, above all, cement prehydration due to uncontrolled storage from a phenomenological perspective through the application of the EMM-ARM method. In particular, the influence of those factors on the early-age evolution of the Young’s modulus of cement pastes produced from Portland as well as pozzolanic cement is experimentally assessed. The obtained results confirm the possibility of exploiting the EMM-ARM method to characterize those effects on a phenomenological basis, sorting back to the comparison of the curves of prehydrated cement with reference ones in controlled storage conditions. As a result, the methodology shows promising applicative perspectives for acceptance checks of the materials before use.

The Influence of Pulverized Fuel Ash (PFA) on the Thermal and Transport Properties of Foamed Concrete

The incorporation of materials derived from industrial waste presents a viable avenue for mitigating the exorbitant production expenses associated with building materials, while concurrently ameliorating the deleterious ecological ramifications of said waste. The utilization of pulverized fuel ash (PFA), an industrial residue resulting from the combustion of powdered coal in an electricity-generating facility, as a substitute for cement in the composition of concrete, is a viable option owing to its inherent pozzolanic properties. The present study endeavours to investigate the potential of Partially-Fumed Ash (PFA) as a viable substitute for cement in the production of foamed concrete (FC). The thermal and transport properties were meticulously assessed, with a particular focus on thermal conductivity, thermal diffusivity, specific heat capacity, water absorption, and porosity. A series of experiments have been undertaken wherein varying proportions of Portland Pozzolan Cement have been substituted for PFA, specifically at levels of 10%, 20%, 30%, 40%, and 50% by weight. The findings suggest a prospective application of PFA in the manufacturing of FC. The utilization of PFA (Pulverised Fuel Ash) assumes a pivotal role in enhancing the thermal conductivity, thermal diffusivity, specific heat capacity, water absorption, and porosity of FC. Therefore, it can be inferred that the utilization of PFA holds promising potential in the production of cost-effective, lightweight construction materials, while simultaneously mitigating the adverse environmental consequences.

Manufacture of eco-friendly cementitious building materials of high performance from Egyptian industrial solid wastes

One of the goals of modern societal development is to achieve environmental sustainability by expanding the number of smart cities with eco-friendly buildings. A research was carried out to investigate the possibility of utilizing Egyptian industrial solid wastes from factories to create sustainable construction materials in order to accomplish this goal. Along with various waste products including cement kiln dust (CKD) and silica fume (SF), which were chemically categorized, the investigation identified metakaolin (MK) and dealuminated kaolin (DK). Various dry mixes were used to determine the hydration characteristics of the binders, including MK-CKD, DK-CKD, OPC-DK, DK-CKD-SF, MK-CKD-SF, and OPC-DK-SF.The physico-chemical and mechanical properties of the cement pastes were analyzed using compressive strength (CS), chemically combined water (Wn, %), and free lime (CaO, %) content over time. The hydration products were identified using differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Scanning electron microscopy (SEM) analyses. The findings revealed that DK had a larger surface area (95 m2/g) than MK and displayed greater pozzolanic activity, particularly during early hydration. Moreover, the inclusion of SF provided further densification of the microstructure of the hardened DK-CKD-SF and/or OPC–DK–SF pastes.According to the findings, the OPC-DK pozzolanic cement pastes had a denser structure than the neat OPC paste. Moreover, the inclusion of SF resulted in additional densification of the microstructure of the hardened OPC-DK-SF pastes, which was evident in the observed increase in compressive strength values at all ages of hydration. The use of industrial solid waste as a sustainable building material has the potential to assist Egypt in meeting its goals for sustainable development and climate protection.

Influence of Corn Cob Ash-Silica Fume Blend on the Mechanical and Durability Properties of Concrete

— This research explored the feasibility of corn cob ash-silica fume blend in the production of pozzolanic cement to produce High-Performance Concrete. The cement in concrete was partially replaced by corn cob ash-silica fume blend in 5,10,15 and 20% by weight of cement and was compared to a control mix of 0% replacement. An intelligent mix design, Densified Mix Design Algorithm (DMDA), was used to effectively reduce both water and cement content. In order to create high strength and workability, a polycarboxylate-based super plasticizing admixture was utilized in conjunction with a low water binder ratio of 0.35. Compressive strength was appraised to determine the mechanical properties at days 3,7,14,28 and 56 to determine the optimum percentage replacement and compared to the control at the specific ages. With the optimum percentage replacement, the flexural test was investigated at 28 days. Water absorption and electrical resistivity tests were also investigated as potential indicators of durability. All of the blends that included corn cob ash and silica fume produced a higher strength than the control except 15 and 20%, with 10% replacement yielding a cube strength of 61 MPa at day 56.

Study of degree of saturation in durability models of reinforced concrete for chloride attack

The depth of penetration of chloride content (normally considered around 0.4% in relation to the mass of cement, as it is approximately the depassivation content of the steel inside the concrete) depends on the concentration of chlorides on the surface of the structure, on the temperature, exposure time and diffusion coefficient of the concrete. In turn, the diffusion coefficient of concrete depends on the characteristics of the concrete and the environment in which it is inserted. Considering the materials and concrete used in this research, the pozzolanic cement presented lower diffusion coefficients in relation to the ARI types of cement, even considering the greater resistance of the ARI Cement. Concrete made with ARI cement with 10% micro silica was the closest in performance to concrete made with pozzolanic cement with the same w/c ratio.

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

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

Replacement of pozzolanic blended cement by supplementary cementitious materials: Mechanical and environmental approach

Pozzolanic blended cements, used in several markets, can be mixed with supplementary cementitious materials (SCMs) to improve environmental performance keeping a similar compressive strength. Many SCMs are industrial byproducts that do not require intensive processing. Six industrial byproducts were studied as replacement of pozzolanic blended cement. Reactivity, compressive strength, and environmental performance were measured. Results showed that the use of SCMs as partial replacement for pozzolanic blended cement increases the reactivity of cement and, therefore, the compressive strength of cementitious pastes. Furthermore, environmental results showed beneficial or detrimental effects depending on replacement level, compressive strength, and CO2 footprint of each SCM.

Experimental Research on Natural Pozzolan as Cement Replacement

This paper presents the properties of mortar and concrete with NBRRI pozzolan as partial replacement of cement. In this research, NBRRI pozzolan from NBRRI and local cement (Dangote) are used. Firstly, chemical composition of NBRRI pozzolan and Dangote cement are analyzed. And then the physical properties of local materials used in this research are determined according to ASTM procedure. Partial replacement percentages of pozzolan are considered 10%, 20%, 30% and 40%. The strength of mortar and concrete with NBRRI pozzolan (0%, 10%, 20%, 30%, and 40%) is tested at 7 days, 14 days and 28 days. From the trial mix design, the water-cement ratio (0.555) is obtained by using the least square method. To get target strength (4000 psi), by using water-cement ratio (0.555) and 68% of maximum aggregate size (20 mm), the concrete mix proportion (1:1.9:3) is obtained. The compressive strength of concrete with various percentages of NBRRI pozzolan at 21 days and 28 days are more than 7 days and 14 days strength. Therefore, it can be concluded that NBRRI pozzolan can be used as cement replacement material when high strength performance in structures is not required.

Optimised processes for the production of performance concrete constituents based on agricultural wastes

In most parts of the world urban populations are growing. This inevitably requires resources for construction materials, which is a challenge to achieving global climate goals. Since there is no alternative to concrete as structural material, novel approaches are required to use cement in concrete more efficiently and to use as little Portland cement clinker in the binder for concrete. With novel approaches, Africa can spearhead green urban construction technologies globally, as the continent’s carbon emissions re marginal today in comparison to the rest of the world and the potential to use local resources are enormous. The authors of the paper develop conclusions on how bio-waste can be converted to organic and mineral concrete constituents that have a potential to create rural livelihoods and urban construction materials markets. A three-step solution including a hydrothermal process, a pyrolysis step and a co-fuelling process with brick production in a vertical shaft kiln is suggested to derive organic components, various by-products as well as bricks and pozzolanic cement replacements, respectively.

Effect of Hydrophobic Water Repellent Admixture on the Compressive Strength of Concrete in Highly Aggressive Water (Dead Sea Water as a Case Study)

The compressive strength of concrete may be affected by seepage of salt water. Dead Sea water is a hazardous environment for concrete due to high concentration of salts. The aim of this study was to investigate the effect of Dead Sea water on the compressive strength of concrete containing hydrophobic water-repellent admixture, and to determine the optimum dosage of admixture to be used to reduce this effect. Three types of cement were used (Ordinary Portland Cement, Pozzolanic Cement, and Sulphate-Resisting Cement) with various dose rate of hydrophobic water repellent admixture (0%, 2%, and 4% of cement weight). An experimental approach, in which the specimens were divided based on the type of cement and the specimen’s age, was adopted. Nine control cubic specimens were cured in plain water to ensure that the required compressive strength was reached and (54) specimens were cured in Dead Sea water. The specimens cured in Dead Sea water were tested at 7 and 28 days to investigate the effect of Dead Sea water on the early and long-term strength. The results showed that a reduction in the 28-day compressive strength occurred in all specimens for the three types of cement used, but with the addition of water repellent, this reduction was alleviated, and the optimum percentage of admixture was 2% of cement weight.

Mechanical, durability and microstructural characteristics of Portland pozzolan cement (PPC) produced with high volume pumice: Green, cleaner and sustainable cement development

Nowadays, it is frequently preferred to use pozzolans instead of clinker to reduce the CO2 emissions that increase with cement production. Because in the future, the release of artificial pozzolans, such as fly ash and blast furnace slag, will decrease. Therefore, the demand for natural pozzolanic cement will increase. This study aimed to produce Portland Pozzolan Cement (PPC) by using pumice instead of clinker up to 40%. The Chemical, physical, mechanical, durability, microstructure, and carbon footprint characteristics of PPCs were investigated experimentally. As the pumice volume in the PPCs increased, the CaO/SiO2 ratio and specific gravity decreased. Due to the hygroscopic moisture of the pumice, its grindability has become difficult. While the 40 µm sieve residue of PPCs ranges from 0.8 to 1.7%, the sieve residue ratio generally increases as the pumice volume increases. The porous structure of pumice led to an increase in Blaine fineness as the replacement ratio increased. The Blaine fineness of PPCs containing 40% pumice rose by about 20% more than the reference cement. The consistency water of PCs varies between 29 and 36%. As the water consistency increased, the setting time of the pastes was prolonged. Initial setting times of PPCs are between 150 and 220 min. If the CaO/SiO2 ratio decreased with the pumice volume, the compression strength of the mortars decreased. While the 28-day compression strength of PPC containing 10% pumice was measured as 36.2 MPa, this value was measured as 21.6 MPa for PPC containing 40% pumice. As the pumice volume increased, the mortars' drying shrinkage and sulfate-induced expansion values decreased significantly. According to the sustainability analysis, the CO2 emissions of cement vary between 518 and 880 kg CO2/t. By using pumice instead of clinker, CO2 emissions of cement can be reduced. In SEM examinations, it was determined that pumice concentrated the microstructure. As a result, it has been determined that eco-friendly cement can be obtained by using 10% and 20% pumice in PPC production.

Effects of acid attack and cassava flour dosage on the interfacial transition zone thickness, durability and mechanical characteristics of high-strength (HS) concrete

Due to its higher porosity, the interfacial transition zone (ITZ), that is, the zone between the hardened cement paste (HCP) and the aggregate, is the weakest point in concrete. It is less resistant to cracking than both HCP and aggregate, and microcracks begin in this zone when the load is applied and propagates into the mass of concrete. The goal of this research is to investigate how various dosages of cassava flour (CF) addition affect the ITZ and how this is related to the mechanical properties of concrete, including its resistance to sulfuric acid. CF is added as a percentage of Portland pozzolanic cement (PPC) used as a binder, with dosages of 1, 2, 3, 4, and 5%. The morphology of CF and PPC was studied using x-ray diffraction (XRD) and x-ray fluorescent (XRF) techniques. Changes in the thickness of the ITZ were observed using a scanning electron microscope (SEM). The effect of sulfuric acid was observed by immersing samples of concrete in a 2% sulfuric acid solution. The results show that adding CF up to 3% progressively reduced the thickness of ITZ and improved the densification of concrete. As more CF was added, the ITZ began to widen again, but even at 5% CF addition, the thickness of the ITZ remained well below that of the control. The workability of fresh concrete decreased with an increase in CF dosage, but CF addition increased the compressive, tensile, and flexural strengths of hardened concrete. The greatest compression resistance was achieved at a 3% cassava flour addition level, which was 83.8 MPa after 180 days of curing and 8.9 MPa, 4.7 MPa for flexural and splitting strengths, respectively, after 90 days of curing. All the concrete samples containing CF had lower strengths than the control after immersion in sulfuric acid, with the concrete with 3% CF performing better than the others. The research concludes that CF used as an additive to concrete in dosages up to 5% improves the ITZ zone, leading to improved mechanical properties. However, resistance to sulfuric acid attacks is reduced. In all tests, it has been shown that a CF dosage of 3% gives the best results.

Adding hydrated lime for improving microstructure and mechanical properties of mortar for ultra-high performance concrete

Because of the insufficient calcium hydroxide content required for the pozzolanic reaction in ultra-high performance concrete (UHPC) incorporating high-volume mineral admixtures, hydrated lime was intentionally added to the mortar used for UHPC to investigate its influence on the compressive strength and splitting tensile strength of mortar. The mechanism of the effect of hydrated lime on the mechanical properties of mortar was analysed by microstructural tests, including X-ray diffraction (XRD), thermogravimetric analysis (TGA), environmental scanning electron microscopy (E-SEM), and mercury intrusion porosimetry (MIP). The results showed that supplementary hydrated lime at various proportions was conducive to the improvement in the mechanical properties of mortar under the combined curing of hot water at 90 °C and subsequent dry-air heating at 250 °C. The improvement in mechanical properties was due to the transformation of calcium-(aluminium)-silicate-hydrate (C-(A)-S-H) gels generated by the pozzolanic reaction into crystalline tobermorite and xonotlite and the subsequent refinement of the microstructure. Furthermore, a denser microstructure and better mechanical properties were achieved when the pozzolanic reaction and cement hydration reached an optimal balance, accompanied by a relatively high content of crystallised phases, including tobermorite and xonotlite.

Volcanic Ash from the Island of La Palma, Spain: An Experimental Study to Establish Their Properties as Pozzolans

The eruption of the Cumbre Vieja volcano on 19 September 2021, resulted in the deposition of large quantities of volcanic ash (VA), causing a great impact on the citizens. This work aims to study the properties of this volcanic ash as pozzolanic raw materials to establish their potential use in the development of sustainable cement. Results of chemical and technical characterization are presented. To achieve this goal, Ordinary Portland Cement (OPC) was replaced with standardized percentages of OPC/VA: 10, 25, and 40%. Characterization studies were carried out using chemical analysis of X-ray fluorescence (XRF), chemical quality analysis (QCA), pozzolanicity test (PT) at 8 and 15 days, as well as determining the mechanical strength (MS) at 7, 28, and 90 days. The results obtained by XRF and QCA established that the chemical composition of the VA corresponds to that of the natural pozzolan typical of pyroclastic genesis. The PT test showed that the analyzed samples have a marked pozzolanic nature, both at 8 and 15 days, showing a significant increase in their hydraulic reactivity. Likewise, the MS tests confirmed a continuous increase in mechanical compressive strength, which increased significantly from 7 to 90 days of curing, reaching more than 58 MPa. On the other hand, mechanical tests showed that the three types of dosages used OPC/VA: 10, 25, and 40% were equally effective, with OPC/VA formulations: 10–25% being the most effective. The results obtained in this research could be used by local industries as a guide for the correct use of the volcanic materials of this island, both for the manufacture of construction materials, such as aggregates, and to produce pozzolanic cement with low CO2 emissions, thus having a positive impact on the environment. Finally, the great natural availability of natural VAs in the surrounding areas of La Palma could cover part of the needs for materials used in the construction and restoration of houses and infrastructures damaged during the volcanic eruption.

Ignimbrites Related to Neogene Volcanism in the Southeast of the Iberian Peninsula: An Experimental Study to Establish Their Pozzolanic Character

The speed at which climate change is happening is leading to a demand for new pozzolanic materials that improve the quality of cements and, at the same time, limit the emission of greenhouse gases into the atmosphere. The main objective of this work is the detailed characterization of an ignimbrite sample (IGNS) to demonstrate its effectiveness as a natural pozzolan. To meet this objective, a series of tests were carried out. In the first stage, mineral and chemical analyses were performed, such as petrographic analysis by thin section (TSP), X-ray diffraction (XRD), oriented aggregate (OA), scanning electron microscopy (SEM) and X-ray fluorescence (XRF). In the second stage, the following technical tests were carried out: chemical quality analysis (QCA), pozzolanicity test (PT) and mechanical compressive strength (MS) at 7, 28 and 90 days, using mortar specimens with ignimbrite/cement formulation (IGNS/PC): 10, 25 and 40% to establish the pozzolanic nature of the ignimbrite. The results of the mineral and chemical analyses showed that the sample has a complex mineralogical constitution, consisting of biotite mica, potassium feldspar, plagioclase, smectite (montmorillonite), quartz, volcanic glass, iron, titanium and manganese oxides, chlorite and chlorapatite. On the other hand, the technological tests revealed the pozzolanic nature of the sample, as well as visible increases in the mechanical compressive strengths in the three proportions, the most effective being IGNS/PC:10% and IGNS/PC:25% at 7, 28 and 90 days of setting. The results obtained could be applied in the formulation of new pozzolanic cements with ignimbrite as a natural pozzolanic aggregate.

Investigating the role played by portlandite and C-A-S-H in the degradation response of pozzolanic and slag cements to external sulphate attack

Cements made with pozzolanic materials and/or latent hydraulic materials are developed to replace Portland cement and decrease the impact of cement production on the CO2 emissions. Those cements need to be qualified regarding their performances and durability, knowing they exhibit good behavior when exposed to external sulphate attack. Pozzolanic materials offer a specific composition of hydrated cement phases with less portlandite and more C-A-S-H than Portland cement. Moreover, they contain a reduced proportion of clinker, hence a reduced share of C3A. All these characteristics explain the unique response of pozzolanic cement to external sulphate attack. However, the pozzolanic reaction is more than often incomplete, with some remaining portlandite in the hydrated cement paste. In order to investigate the role played by this remaining portlandite fraction during external sulphate attack, the behavior of two CEM III and two CEM IV cement-based mortar samples were studied and compared to two CEM I- type cements, one SR and one non-SR. The pozzolanic nature of these cements has been investigated by monitoring the portlandite content of cement paste over time by thermogravimetric analysis. In addition, the behavior of synthetic C(-A)-S-H containing portlandite and in suspension in sulphate solutions has been assessed by X-ray diffraction and scanning electron microscopy. Results have confirmed the sulphate resistance of the studied blended cements compared with a sulphate-resistant Portland cement (CEM I SR3), although the cements still containing portlandite did undergo a slight expansion. The test on C(-A)-S-H showed that the presence of portlandite encourages the precipitation of ettringite within the C-A-S-H nano porosity, even in the absence of pH regulation.

Influence of a High Degree of Filling on the Properties of Pozzolanic Cement

Slagash wastes of the Angren and Novo–Angren TPPs of dry selection high pozzolanic and hydraulic activity and its compliance with the requirements for State Standard of the Republic of Uzbekistan 901 for active mineral additives have been established, and therefore, it is recommended as an active mineral additive for the production of pozzolanic cements with a high degree of filling. Replacing from 25% to 50% of high–temperature portland cement clinker with dry–selection composite ash and slag waste ensures the production of pozzolanic cement grades 400–500. Concretes based on pozzolanic cements with a high content of СASW show a fairly high resistance to the aggression of sulfate salts, frost and changes in atmospheric vibrations, which makes the developed cements in demand in the construction industry of the Republic.

Study of the Genetic Formation of New Formations during the Hardening of Pozzolanic Cement with a High Content of Ash and Slag Waste of Dry Selection

Study of the Genetic Formation of New Formations during the Hardening of Pozzolanic Cement with a High Content of Ash and Slag Waste of Dry Selection

Https://doi.org/10.47191/ijcsrr/V6-i2-09

The results of physical and chemical studies of the processes of hydration and structure formation during hardening of pozzolanic cements containing dry–selection ash and slag waste from the Angren TPP as an active mineral additive are presented. It has been established that, despite the replacement of up to 50% of the clinker part, the experimental cements acquire high hydraulic activity, which ensures their grade 400–500, which is facilitated by the presence of active silica, alumina and low–basic calcium silicates in the composition of the additive, which in the process of chemical interaction with hydration products clinker minerals are involved in the formation of a dense microstructure of the cement composite.

Influence of a High Degree of Filling on the Properties of Pozzolanic Cement

Influence of a High Degree of Filling on the Properties of Pozzolanic Cement