Pozzolanic Materials Research Articles

Target dispersion of pozzolanic materials nearby hydration-released calcium hydrates to improve the pozzolanic reaction degree

The random distribution of pozzolanic materials (PM) using direct mixing strategy reduces their contact possibility with hydration-released calcium hydroxide (CH), and limits the corresponding reinforcing efficiency to cement-based materials via pozzolanic reaction. In this study, a target dispersion strategy of PM nearby CH was proposed using super absorbent polymers (SAPs) as the carrier. On the one hand, nano silica (NS) and calcined clay (CC), two typical PM, can be encapsulated into SAPs through the hydrogen bonding interaction; on the other hand, the region around SAPs was enriched with more water and higher Ca2+ concentration, which triggered the in situ crystallization of CH. In this case, the contact possibility between the NS or CC (NS/CC) and hydration-released CH was improved by the target dispersion strategy, and resulted in a 60 %–253 % increase in pozzolanic reaction degree (PRD) of NS/CC. Furthermore, the reinforcing effect of NS/CC on compressive strength of cement paste was enhanced by 25 % through this strategy. Therefore, the current study introduces a novel method for increasing the pozzolanic reinforcing efficiency of cement-based materials by turning the random to target dispersion of PM nearby CH.

Mechanical properties of geopolymer concrete incorporating supplementary cementitious materials as binding agents

This research investigates the environmental impact of cement production by exploring eco-friendly geopolymer binders as alternatives. Geopolymer concrete, developed using silica and alumina-rich precursors such as pozzolanic materials, achieves high compressive strength, up to 43.6 N/mm2 with a 16 M concentration and integrated steel fibers. Utilizing manual mixing and industrial by-products, the study pioneers cast-in-situ geopolymers with innovative curing techniques. The paper presents experimental results on the engineering properties of geopolymer concretes of 40 MPa, cured at 100 °C and 60 °C. The study systematically varies binder content, examining proportions of fly ash, GGBS, metakaolin, and silica fume, along with different mix ratios and molar concentrations. Key findings include increased compressive strength with higher NaOH concentration, peaking at 35.2 N/mm2 and 34.22 N/mm2 for 14 M mixes at 7 and 28 days, and 40.29 N/mm2 for 16 M mixes at 7 days. Optimal results were observed at higher curing temperatures, especially with 14 M and 16 M compositions at 100 °C. The study recommends mechanized mixing for efficiency and calls for further investigation into the microstructure and chemistry of geopolymers to advance sustainable construction practices. This research represents a significant step towards eco-conscious building materials, reducing the environmental impact of the construction industry.

Harnessing Natural Pozzolan for Sustainable Heating and Cooling: Thermal Performance and Building Efficiency in Moroccan Climates

The need to construct environmentally friendly buildings to meet current environmental and ecological standards is urgent. This study introduces a new multi-layer construction material with two outer layers of ordinary mortar and an inner layer of a pozzolane-limes composite to meet this need. The thermal efficiency of this material in building construction is investigated using TRNSYS18 simulations for two distinct climatic zones in Morocco, with a particular focus on its impact on heating dynamics. The primary objective is to evaluate the thermal performance of multi-layered pozzolanic materials, for which mortar samples are meticulously prepared as a reference in the two different climatic zones (Azilal and Errachidia). Using the asymmetric hot plate method under both stable and transient conditions, the authors conduct thermal characterization experiments. The results underscore the improvement in thermal performance made possible by the incorporation of pozzolan as an aggregate in the multi-layer material compared to ordinary mortar. Specifically, thermal conductivity improves significantly, from 0.735 W m−1 K−1 for ordinary mortar to 0.4 W m−1 K−1 for multi-layered pozzolanic materials, representing a 46% mass gain. Additionally, effusivity decreases from 730 to 604 J m−2 K−1 s−1/2, while diffusivity decreases from 3.78 to 2.23 × 10−7 m2 s−1, further attesting to the material’s thermal efficacy. TRNSYS18 simulations corroborate the viability of using multi-layered materials as building envelopes, revealing potential annual heating gains of 25% in Azilal and 5% in Errachidia. These findings underscore the promising prospects of integrating these materials into sustainable construction practices.

Current and potential materials for the low-carbon cement production: Life cycle assessment perspective

Given the carbon-intensive nature of cement production, conducting a comprehensive environmental evaluation using life cycle assessment (LCA) modeling is paramount to achieving eco-friendly cement standards. This study meticulously compiles and evaluates LCA findings from diverse analyses of current and potential supplementary cementitious materials (SCMs) within the blended cement sector. It underscores the impact of the functional unit (FU) within the LCA approach, supply chain considerations, and technical and regulatory factors on the sustainability of blended cement mixtures. Most of LCAs studied herein show that integrating SCMs into the cement matrix typically reduces land use, energy consumption, and greenhouse gas (GHG) emissions, thereby lowering the global warming potential (GWP) of ordinary portland cement (OPC) samples from 831 to 980 kg of CO2-eq to 768-481 kg of CO2-eq per ton of cement. However, in some instances, environmental indicators like abiotic depletion potential-elements (ADP-E) and human toxicity potential (HTP) rise due to increased mining, electricity, and transportation demand for SCMs. Regarding the environmental potential of alkali-activated cementitious materials and low-carbon clinker formulations, we found that limitations arise in fully replacing OPC due to global raw material availability constraints, rendering them economically unfavorable and impeding their widespread adoption. Among the SCMs examined in this study, clays, which are more widely available compared to industrially sourced materials like fly ash, slag, and silica fume, exhibited a more favorable environmental profile when evaluated using a mass-based FU. Incorporating compressive strength into the FU resulted in greater environmental benefits from high-strength blendedcement composites. However, this approach might lead to inaccurate results because higher strength does not always correspond to a lower environmental impact. Thus, establishing a FU that accurately reflects the environmental impact of blended cement and its composites (e.g., concrete and mortar) is crucial. Despite the potential of various pozzolanic materials to reduce clinker content in cement mixtures, their wide utilization remains restricted due to the absence of widescale market-based initiatives, green procurement strategies, and effective policy measures, which hampers their industrial and public acceptance. Consequently, governmental support is essential for developing and integrating sustainable cement solutions.

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%.

Investigation of Strength Concrete Materials Using Pozzolanic Additives

In the study, pozzolanic materials serve as replacements for additives, namely Palm Shell Ash (PSA), Coal Fly Ash (CFA), and Rice Husk Ash (RHA). The purpose of the study is to determine the optimum proportion of additives used in high-performance concrete. The addition of 15% PSA resulted in a strength of 69.227 MPa over a test period of 56 days, while the addition of 15% CFA yielded a strength of 69.369 MPa, and the addition of 5% RHA resulted in a strength of 59.984 MPa. The maximum concrete strength is achieved by adding 15% PSA. Correlation analysis between stress-strain indicates that aggregates exhibit higher strength compared to cement paste, mortar, and concrete, highlighting the relationship between the aggregate, cement paste, mortar components, and concrete as a composite material. Aggregate strength values found to be the highest among concrete, cement paste, and mortar, indicating that cement paste contributes the least to the strength of concrete, followed by mortar as concrete reinforcement. The results suggest that aggregates remain the primary strength component supporting concrete. The finding indicates that the relationship between the basic substances in this study aligns closely with existing theory. Moreover, it suggests that all concrete materials with pozzolan variants can classified as high-quality concrete. The optimum percentage is obtained by adding 15% palm shell ash, resulting in the highest compressive strength compared to counterparts and test objects with other types of pozzolan additions. The relationships between the constituents of concrete demonstrate that aggregates continue to be important contributors to concrete strength, with the cement paste contributing the least. Concrete strength values fall between those of aggregates and those of cement and mortar pastes.

Combined effect of silica fume and various fibers on fresh and hardened properties of concrete incorporating HDPE aggregates

Recycling of waste plastics has become essential to mitigate their detrimental impact on the environment. However, it can be used in the construction sector to fulfill construction needs and conserve natural resources. Previous research has demonstrated that incorporating plastic aggregate reduces the strength properties of concrete; hence, there is a need to improve its strength properties. In this study, high-density polyethylene (HDPE) plastic is incorporated in aggregate form, as a partial substitute for natural coarse aggregates (NCA) at volumetric ratios of 10 %, 30 %, and 50 %. Various strength enhancement techniques, including the addition of macro synthetic fibers (MSF), steel fibers (SF), and substituting 20 % of cement with silica fume, were employed. The results indicated that workability of concrete is improved with an increase in the content of HDPE coarse aggregates (HCA). Furthermore, concrete containing 30 % HCA performed better in terms of strength compared to concrete with 10 % and 50 % HCA. The findings demonstrate that concrete containing fibers performs better than concrete without fibers. The utilization of 0.75 % MSF and 1 % SF dosage leads to a 93 % improvement in splitting tensile strength, a 72 % improvement in flexural strength, and a 48 % improvement in compressive strength for concrete containing 30 % HCA. Using scanning electron microscopy, it was found that incorporating HCA weakens the internal matrix. However, the addition of a precise amount of fibers and pozzolanic materials resulted in improvements in microstructure. The significance of this research lies in the utilization of HDPE waste materials in concrete by simultaneous usage of different fibers.

Study of Sago Fine Waste (SFW) as a Pozzolanic Material in Cement Bricks with Different Water-Cement Ratio

Study of Sago Fine Waste (SFW) as a Pozzolanic Material in Cement Bricks with Different Water-Cement Ratio

The influence of cement bypass dust composition on the properties of slag-based mortars

Research on sustainable alternatives to Ordinary Portland Cement aims to reduce global CO2 emissions from cement production. Utilizing byproducts or waste materials to create sustainable binders is a promising approach. Cement bypass dust is being investigated as a potential activator of pozzolanic materials, however there is large variability in the composition of this dust and research is necessary to understand the differences for the potential application of the waste material. The objective of this work was to compare two bypass dusts where ternary and binary mortars of bypass dust (50 %, 30 %, 10 %, 0 % and by weight), cement (100 %, 80 %, 40 % and by weight), and blast furnace slag (50 %, 30 %, 10 % and 0 % by weight), were produced. Mortars were all ambient cured and a water to binder ratio of 0.6 was maintained for all mixes. The results showed that one bypass dust had a much higher free lime and chloride content, whereas the other had more calcite and sulphates. Compressive strengths of the 1:1 slag and sulphate rich bypass dust were of 18.6 MPa at 90 days, and lime rich bypass dust achieved 15.1 MPa. X-ray diffraction and thermogravimetric analysis revealed that sulphate rich bypass dust formed more ettringite, enhancing strength, while lime rich bypass dust formed more portlandite due to its lime content. Chemical shrinkage results showed volumetric expansion at early ages for both bypass dusts with lime rich bypass dust swelling up to 0.057 ml/g and sulphate rich bypass dust up to 0.015 ml/. Despite this, both bypass dust binders exhibited higher shrinkage strains over a 150-day period compared to cement, where sulphate rich and lime rich bypass dust had strain percentages of 0.225 % and 0.228 %, respectively. This work found the main differences between the composition of two bypass dusts, and it was found that these materials can be reused to fabricate cementless binders.

Research on the effect of tuff powder on the properties of moderate-heat portland cement-based materials and the methods for evaluating pozzolanic activity

Tuff powder (TP) has attracted significant attention due to its abundant resources, low carbon emissions, and potential enhancements in concrete property. This study investigates the effect of TP on the mechanical properties, hydration behavior, pore structure, microstructure morphology, economic and environmental analysis of moderate-heat portland cement (MHPC), comparing it with MHPC-based materials containing fly ash (FA). The synergistic morphological effect and micro-aggregate filling action of FA and TP result in higher early strength in the fly ash-tuff powder (FT) group mortar. The CH content and chemically bounded water content of TP paste are higher, showing a better early hydration promotion effect. The pore structure of the composite cement mortar is changed due to the addition of the admixture. Furthermore, the multi-factor response strength and strength activity index (SAI) model were developed based on response surface methodology (RSM), linking to TP specific surface area, dosage, and specimen curing age. This provides a reference for more accurate and comprehensive prediction of cement mortar property, quantification of effects, optimization of mix proportions, and evaluation methods for the activity of pozzolanic materials.

Mechanical properties, microstructure and GEP-based modeling of basalt fiber reinforced lightweight high-strength concrete containing SCMs

The pressing need to address recent global climate changes calls for replacing high-carbon-emitting cement with environmentally friendly materials that retain the strength and properties of conventional concrete. This study explored the mechanical properties of lightweight concrete (LWC) incorporating shale aggregate and basalt fibers alongside a partial replacement of environmentally detrimental cement with pozzolanic materials like fly ash (FA), blast furnace slag (BS), and silica fume (SF) up to 30 %. Twenty mix designs were developed to examine their mechanical properties and microstructural characterization. It was also observed that SF outperformed other industrial byproducts and gave better strength with the optimum replacement of 20 % cement, achieving 102.6 %, 105.6 % and 109.5 % of the control mix compressive, flexural, and split-tensile strength, respectively. However, a further increase of up to 30 % decreased strength. FA and BS resulted in lower strength than the control sample and other byproducts-based mixes, with compressive strength decreasing by 4 %–20.5 % at replacement levels of 10 %–30 %, respectively. BS resulted in an initial increase in strength at 10 % replacement but decreased by 10.8 %–21.6 % at higher levels. This trend was similar for flexural and tensile strengths. However, adding basalt fibers resulted in higher strength compared to non-fiber mixes and increased the strength of LWC by up to 25.2 %. The micromorphology and pore structure study indicated that the high-performance paste and fibers bridging effect were crucial for high strength. Gene expression programming (GEP) based modeling, validated against our own experimental results, was employed to predict the outcomes, demonstrating strong correlation coefficients for compressive, flexural and tensile strength (0.9430, 0.9609 and 0.9353, respectively). Additionally, SHapely Additive exPlanations (SHAP) analysis was used to assess the impact of each input parameter, highlighting the positive effects of the water-to-binder ratio and lightweight aggregate on the LWC's mechanical properties. This study is novel in its comprehensive examination of the combined impact of SCMs, shale aggregate and basalt fibers on the performance of LWC, a synergy not extensively explored in prior research. Furthermore, a novel generalized constitutive model was developed, and a SHAP analysis was performed to help design an efficient mix design to enhance the mechanical performance of LWC.

Carbonated calcium silicates as pozzolanic supplementary cementitious materials

This study examined the carbonation mechanisms and products of various precursors, including hydrated cement pastes and calcium silicate clinkers. Regardless of the materials investigated, all exhibited rapid carbonation reactions and achieved high degrees of carbonation. Calcium carbonate and siliceous gel were consistently formed as carbonation products. The starting materials significantly influenced the characteristics of the siliceous gel. Carbonated concrete pastes displayed a higher presence of alumina in the gel, resulting in greater surface area and nano-porosity compared to gels formed from calcium silicate clinkers. The pozzolanic reaction products also differed depending on the precursor, with carbonated concrete pastes forming C-S-H and AFm phases, while carbonated calcium silicate clinkers produced only C-S-H phase. Such variations impacted the evolution of mechanical performance in composite cements. Notably, carbonated composite cements containing recycled concrete pastes exhibited higher early compressive strength compared to carbonated calcium silicate clinkers. However, the final compressive strength is similar.

Effective Use of Pozzolanic Materials for Stabilizing Expansive Soils: A Review

Effective Use of Pozzolanic Materials for Stabilizing Expansive Soils: A Review

Pemanfaatan Abu Cangkang Kopi Sebagai Substitusi Semen Untuk Bahan Beton Ringan Menggunakan Bahan Tambah Sikament NN

The chemical reaction of cement and water produces compounds that are alkaline and react with various acids so that they can reduce the quality of concrete. To minimize this effect, pozzolanic materials need to be added. Organic pozzolan materials such as coffee shell ash waste can be used as material for making lightweight foam concrete which can be applied to non-structural buildings such as lightweight bricks. This research was conducted to see the effect of coffee shell ash substitution for cement on the properties of fresh concrete and the mechanical properties of lightweight foam concrete and to find the most optimal substitution composition for coffee shell ash for cement as well as lightweight foam concrete with FAS 0.5. Substitution of coffee shell ash for cement weight was carried out with variations of 0% BBN, 5% BBAAK1, 10% BBAAK2, and 15% BBAAK3 using 1% superplasticizer additive. The test object used is a cylinder with dimensions of 15 cm x 30 cm. The number of test objects used was 24 pieces. Tests for compressive strength and split tensile strength were carried out at the age of 28 days. The results of compressive strength tests carried out at 28 days for the lightweight foam concrete variations BBN, BBAAK 1, BBAAK 2 and BBAAK 3 were respectively 15.29 MPa, 12.21 MPa, 18.29 MPa and 19.52 MPa. The greater showing variation in the percentage of coffee shell ash substitution used, the greater the resulting compressive strength and split tensile strength values. This is because Sikament NN also plays a role in increasing the compressive strength of concrete

Mechanical properties of rice husk ash and glass powder concrete: Experimental and mesoscopic studies

Using glass powder and rice husk ash as supplementary cementitious materials (SCM) can effectively reduce cement usage, protect the environment, and promote waste recycling. In this study, ordinary concrete, glass powder concrete, and glass powder rice husk ash concrete were studied through a series of experiments, including tests for slump and water absorption, uniaxial compression, variable angle shear, cyclic compression, and numerical simulation. The following results were identified. Glass powder increases the slump of concrete and reduces its water absorption, whereas the opposite is the case with the addition of rice husk ash. The uniaxial compressive strength of glass powder concrete is higher than that of ordinary concrete at 28 days of curing. Glass powder concrete has the maximum bearing capacity, in terms of the shear test. The minimum damage index is shown under cyclic compression. When the rice husk ash content is 15 %, the combination with glass powder has the strongest pozzolanic effect, while the replacement rates of 30 % and 45 % are not suitable for pozzolanic materials. The dissipation energy conversion rate of the sample containing rice husk ash is always greater than the elastic strain energy conversion rate. In addition, the samples containing rice husk ash showed ductile failure and reduced cracks during compression. This study can provide new insights into the combination of glass powder and rice husk ash as SCM.

Sustainable ground improvement of soft clay using eggshell lime and rice husk ash

Stabilization of clay using lime or cement is conventionally accepted practice. Although it is effective, they impose several implications on the environment. Hence, it is high time that an alternate sustainable binder needs to be investigated. Eggshell, a waste from food industry, is an alternate source for calcite and can be considered to produce eggshell lime (EL). Also, rice husk ash (RHA), an agricultural waste product, is a silica rich source which is a pozzolanic material. In the current study, the efficiency of both the materials in stabilizing the soft soil is investigated and the results suggests that the plasticity and the strength characteristics of soft clay can be significantly improved by the addition of EL. After adding optimum concentration of 3 % EL, the liquid limit decreased from 74 % to 53 %, plastic limit increased from 27 % to 46 % and shrinkage limit increased from 8 % to 44 %. On increasing the EL content, the swelling got reduced from 88 % of virgin clay to 17 % in case of 3 % EL and finally to zero with 5 % of EL. Also, the addition of combination of EL and RHA to the soft clay has improved the strength characteristics significantly. As the curing days increased, slight variation was only seen in the plasticity characteristics which may be due to rapidity of cation exchange. But strength characteristics increased suggesting the occurrence of pozzolanic reactions and formation of gel. The 28th day strength of the clay treated with 3 % EL increased to as high as 757 kPa. The strength characteristics showed that as we increase the percentages of EL and RHA combination, the strength would increase tremendously much better than the treatment with eggshell lime alone. This is because of the supply of CaO and SiO2 sources. For 5 % of EL and 15 % of RHA, the 1 day curing strength was near to 500 kPa. With less concentration of eggshell lime and RHA, the treated soil was appearing to be more porous in SEM while when the binder concentration was increased, the pores were filled and presence of C-S-H gel was also detected. XRD test results also showed the presence of C-S-H gel.

Sustainability evaluation and life cycle assessment of concretes including pozzolanic by-products and alkali-activated binders

The construction industry's top priorities for achieving a sustainable future include minimizing the use of non-renewable resources, managing waste generation, and reducing related gas emissions. This fact emphasizes the need for using natural materials such as pozzolan as a substitute or supplemental component in the production of Portland cement concrete. This study presents a review of evaluating the sustainability performance and life cycle assessment of pozzolan-based concrete compared with ordinary Portland cement concrete using the preference selection index approach and evaluating CO2 gas emissions during material life cycle stages. Furthermore, the durability and environmental effects of using pozzolan in concrete were comprehensively investigated. The advantages of using Pozzolans-based concrete in the development of sustainability aspects have been precisely predicted through the application of the PSI method, which depends on several criteria based on the properties of different cement types. It was discovered that substituting pozzolanic material for a portion of Portland cement when producing concrete significantly reduces the environmental effects (i.e., energy use and carbon dioxide emissions).

Innovative utilization of agro-industrial by-products: Bamboo leaf ash as a pozzolanic material for extruded fiber cement composites

This study aims to promote the valorization of agro-industrial waste and sustainability in the construction industry by evaluating the potential of bamboo leaf ash (BLA) as a partial replacement for Portland cement in extruded fiber cement. Squeeze flow, physical, mechanical, and microstructural analyses (Scanning Electron Microscopy and X-ray microtomography) were conducted. The results showed that the incorporation of fibers and BLA leads to an increased water demand and, consequently, an increase in porosity and pore connectivity. However, the mix design with 10 % replacement exhibited improved mechanical behavior for modulus of rupture (10.2 %) and limit of proportionality (4.5 %), when compared to a formulation without BLA. For the other parameters, the mix design with 10 % BLA showed mechanical behavior with no statical difference to the mix design without ash. Thus, the use of BLA as a partial replacement for Portland cement represents an alternative with technical and environmental improvements for fiber cement.

Testing ECC-Concrete Using Different Fibers (PVA, S.F, Pp)

This study adopted an attempt to produce (Engineered cementitious composites) ECC concrete using different types of fibers such as (PVA, ST, Pp). Studies and researches on the structural properties of ECC concrete are relatively limited in comparison to ordinary concrete. Many investigations on several researchers have worked on ECC concrete. the output of reviewed papers explained that the pozzolanic materials and curing conditions are affected in the clear for the bond strength; it has been discovered that ECC concrete made from fly ash performs better than Conventional Concrete based on Portland cement in terms of mechanical properties, withstanding high temperature, and preservation of fundamental physical characteristics including permeability and water absorption. Whereas few studies exanimated the effect of using special amount of specific ECC fiber on bond strength and the behavior of the construction part .as a first part trials has been made for different ratios and types of ECC fibers has been done ECC mixtures were produced using (polyvynol alcohol PVA fiber, Three aggregate to binder ratios were chosen: (1:0.25, 1:0.3 and 1:0.35) with different water to cement ratio of 0.3, 0.35, 0.4 and 0.45, adding fiber with ratios (0.5,1,1.5,2 and 2.5)% from the mix total volume , After examining the mechanical (compressive and flexural strengths) on the resulted ECC concrete specimens, the mix ratio that provided an acceptable compressive strength and flexural was chosen to be used.

The effect of NaOH and KOH on the strength-mechanical properties of alkali-activated composites based on granulated blast-furnace slag

Abstract Alkali-activated systems are a more sustainable alternative to Portland cement concrete. The activation of latently hydraulic and pozzolanic raw materials in these composites is one of the many investigated factors, where the price ratio and the ability to optimally activate the mentioned precursors with the given activator play a major role. The subject of the presented work is a comparison of the influence of NaOH and KOH on the development of the strength-mechanical properties of alkali-activated materials based on granulated blast furnace slag - the secondary raw material of metallurgical processes.