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Pozzolanic reaction of volcanic ash with hydrated lime is thought to dominate the cementing fabric and durability of 2000-year-old Roman harbor concrete. Pliny the Elder, however, in first century CE emphasized rock-like cementitious processes involving volcanic ash (pulvis) \"that as soon as it comes into contact with the waves of the sea and is submerged becomes a single stone mass (fierem unum lapidem), impregnable to the waves and every day stronger\" (Naturalis Historia 35.166). Pozzolanic crystallization of Al-tobermorite, a rare, hydrothermal, calcium-silicate-hydrate mineral with cation exchange capabilities, has been previously recognized in relict lime clasts of the concrete. Synchrotron-based X-ray microdiffraction maps of cementitious microstructures in Baianus Sinus and Portus Neronis submarine breakwaters and a Portus Cosanus subaerial pier now reveal that Al-tobermorite also occurs in the leached perimeters of feldspar fragments, zeolitized pumice vesicles, and in situ phillipsite fabrics in relict pores. Production of alkaline pore fluids through dissolution-precipitation, cation-exchange and/or carbonation reactions with Campi Flegrei ash components, similar to processes in altered trachytic and basaltic tuffs, created multiple pathways to post-pozzolanic phillipsite and Al-tobermorite crystallization at ambient seawater and surface temperatures. Long-term chemical resilience of the concrete evidently relied on water-rock interactions, as Pliny the Elder inferred. Raman spectroscopic analyses of Baianus Sinus Al-tobermorite in diverse microstructural environments indicate a cross-linked structure with Al3+ substitution for Si4+ in Q3 tetrahedral sites, and suggest coupled [Al3++Na+] substitution and potential for cation exchange. The mineral fabrics provide a geoarchaeological prototype for developing cementitious processes through low-temperature rock-fluid interactions, subsequent to an initial phase of reaction with lime that defines the activity of natural pozzolans. These processes have relevance to carbonation reactions in storage reservoirs for CO2 in pyroclastic rocks, production of alkali-activated mineral cements in maritime concretes, and regenerative cementitious resilience in waste encapsulations using natural volcanic pozzolans.

Ceramic-based wastes generated from different industrial activities have increasingly been reused as construction material incorporated into concrete. In general, these wastes just replace common concrete aggregates such as sand and gravel. In the present work, waste from clay brick industries composted of kaolinite minerals were for the first time evaluated for their potential to be reused as the pozzolan constituent of a cement for structural concrete. Initial standard testes revealed that the clay ceramic waste (CCW) displays high pozzolanicity. Concrete was then produced with 10 and 20 wt.% of CCW mixed with ordinary Portland cement (OPC) as its pozzolan constituent. Compression strength of these concretes and of pure OPC as a control sample were determined in standard tests after 14 and 28 days of curing. In addition, the corresponding density, water absorption, capillarity and percentage of voids were measured together with the evaluation of microstructural indices by scanning electron microscopy. The initial tests confirmed that the CCW is indeed an effective pozzolanic potential due to a chemical effect by reacting with CH to generate C–S–H. Moreover, the technological results proved that CCW might effectively replace the pozzolan cement constituent for structural concrete.

Cement factories in Indonesia rarely produce OPC due to the high cost of production and less environmentally friendly, so they prefer to produce PPC or PCC. Cement factories located in areas that are rich in natural pozzolan will prefer producing PPC. In general, there is an assumption that increasing the compressive strength of concrete using PPC is slow at the early age. Based on these assumptions, it is necessary to conduct research on increasing the compressive strength of concrete using PPC at an early age. The specimen used was a concrete cylinder, with 3 specimens for each variation. The compressive strength test of concrete is carried out at the ages of: 3, 7, 14, 21, and 28 days. From the research results obtained, compressive strength of concrete has increased with increasing age of the concrete. The increasing the compressive strength of concrete using PPC is comparable with concrete using OPC. The unit weight of concrete is almost the same for all ages of concrete.

The safe disposal of an enormous amount of waste glass (WG) in several countries has become a severe environmental issue. In contrast, concrete production consumes a large amount of natural resources and contributes to environmental greenhouse gas emissions. It is widely known that many kinds of waste may be utilized rather than raw materials in the field of construction materials. However, for the wide use of waste in building construction, it is necessary to ensure that the characteristics of the resulting building materials are appropriate. Recycled glass waste is one of the most attractive waste materials that can be used to create sustainable concrete compounds. Therefore, researchers focus on the production of concrete and cement mortar by utilizing waste glass as an aggregate or as a pozzolanic material. In this article, the literature discussing the use of recycled glass waste in concrete as a partial or complete replacement for aggregates has been reviewed by focusing on the effect of recycled glass waste on the fresh and mechanical properties of concrete.

Development of sustainable concrete as an alternative to conventional concrete helps in reducing carbon dioxide footprint associated with the use of cement and disposal of waste materials in landfill. One way to achieve that is the use of fly ash (FA) as an alternative to ordinary Portland cement (OPC) because FA is a pozzolanic material and has a high amount of alumina and silica content. Because of its excellent mechanical properties, several studies have been conducted to investigate the use of alkali-activated FA-based concrete as an alternative to conventional concrete. FA, as an industrial by-product, occupies land, thereby causing environmental pollution and health problems. FA-based concrete has numerous advantages, such as it has early strength gaining, it uses low natural resources, and it can be configurated into different structural elements. This study initially presents a review of the classifications, sources, chemical composition, curing regimes and clean production of FA. Then, physical, fresh, and mechanical properties of FA-based concretes are studied. This review helps in better understanding of the behavior of FA-based concrete as a sustainable and eco-friendly material used in construction and building industries.

The global cement industry faces a critical challenge of reducing its substantial carbon footprint while maintaining material performance. Portland cement production significantly contributes to global CO2 emissions, necessitating innovative sustainable alternatives. This study evaluates the transformative potential of calcined natural pozzolans as a strategic approach to developing low-carbon cement. By systematically investigating the effects of calcined natural pozzolans derived from kaolinite and pyroclastic rocks on cement paste properties, the research demonstrates a promising pathway to environmentally efficient cement formulations. Utilizing advanced characterization techniques including XRD, TGA, SEM-EDX, and gas adsorption porosimetry, this study provides insights into hydration kinetics, compressive strength development, microstructural evolution, and porosity refinement. The results reveal that calcined natural pozzolans strategically enhance cement performance by accelerating hydration processes, improving compressive strength, and sophisticating microstructural characteristics. Notably, pastes incorporating pyroclastic rock pozzolans exhibited superior mechanical properties, with 28-day compressive strengths exceeding ordinary Portland cement by 35.2%. These findings not only validate the technical feasibility of natural pozzolan-based low-carbon cement but also underscore their potential to meaningfully reduce the construction industry’s environmental impact.

ASTM C618 is used to qualify fly ash and natural pozzolans for use in concrete and for sale to the concrete industry. This study tests the notion that ASTM C618 does not adequately qualify natural pozzolans for use in concrete, with the primary concern that ASTM C618 has the potential to provide \"false positives\" for inert materials. Pozzolanicity tests and the tests outlined in ASTM C618 were performed on a variety of natural materials, including those that were known to be pozzolanic or inert and those with unknown pozzolanicity. Compressive strength testing at a fixed water-cementitious materials ratio (w/cm) was also performed on the materials, and the results were compared against the results of the strength activity index (SAT) from ASTM C618, which has a variable w/cm. This study proves that inert natural minerals passed ASTM C618 for a Class N natural pozzolan for use in concrete, suggesting that the standard is inadequate. Keywords: ASTM C618; Class N; natural pozzolan; pozzolanic reaction.

Two waste fired brick powders coming from brick factories located in Argentine and Czech Republic were examined as alternative mineral admixtures for the production of blended cements. In pastes composition, local Portland cements (Argentine and Czech) were substituted with 8–40%, by mass, with powdered ceramic waste. For the ceramic waste-Portland cement system, workability, the heat released, pozzolanity, specific density, compressive strength, hydrated phases, porosity, and pore size distribution were tested. The relevance of the dilution effect, filler effect, and pozzolanic activity was analyzed to describe the general behavior of the pozzolan/cement system. The properties and performance of cement blends made with finely ground brick powder depended on the composition of ceramic waste and its reactivity, the plain cement used, and the replacement level. Results showed that the initial mini-slump was not affected by a low ceramic waste replacement (8% and 16%), and then it was decreased with an increase in the ceramic waste content. Brick powder behaved as a filler at early ages, but when the hydration proceeded, its pozzolanic activity consumed partially the calcium hydroxide and promoted the formation of hydrated calcium aluminates depending on the age and present carbonates. Finally, blended cements with fired brick powder had low compressive strength at early ages but comparable strength-class at later age.

As global demand rises and natural aggregates become scarcer, using supplementary materials and industrial waste for concrete production offers a sustainable solution that conserves resources and reduces waste. Previous studies have demonstrated that pozzolanic additives, such as natural pozzolans and ceramic waste powders, can enhance concrete performance by refining the pore structure, reducing permeability, and improving long-term strength. However, limited research has explored the synergistic use of these materials, particularly in the context of predictive modeling and performance optimization. In the current study, an investigation was conducted to evaluate the effects of replacing cement with waste ceramic powder (at 10%, 20%, and 30%) and natural pozzolan (at 5%, 10%, 15%, and 20%) on the performance of concrete. The physical, mechanical, and durability properties of the resulting concrete mixes were comprehensively assessed, including compressive, tensile, and flexural strength, water absorption, and permeability. These properties were evaluated at various curing ages —7, 28, and 91 days—for compressive, tensile, and flexural strengths and water absorption, while permeability was measured at 91 days. Machine learning models—namely XGBoost, Random Forest, Gradient Boosting, and Elastic Net, were employed to predict compressive, tensile, and flexural strengths, with XGBoost yielding the highest accuracy for compressive and tensile strengths (RMSE = 0.8 and 0.08, respectively) and Gradient Boosting excelling for flexural strength (RMSE = 0.2). The results identified the Kh15C10 mix design (15% Natural pozzolan and 10% waste ceramic powder) as the optimal configuration, exhibiting enhanced compressive strength (8.12–11.49% increase), tensile strength (3.60–6.33% increase), flexural strength (2.99–12.45% increase), as well as reduced water absorption (35.74–77.33% decrease) and permeability (99.82% decrease) compared to the control sample. The integration of waste ceramic powder and natural pozzolan not only enhances mechanical and durability performance but also significantly contributes to environmental sustainability by lowering cement demand, reducing CO 2 emissions, and promoting circular economy principles through waste valorization. In predictive modeling, XGBoost excelled for compressive and tensile strengths with the lowest RMSE values (0.8 and 0.08, respectively), while Gradient Boosting outperformed for flexural strength with an RMSE of 0.2. These findings highlight the potential of these models in optimizing sustainable concrete designs.

Foamed concrete (FC) is a high-quality building material with densities from 300 to 1850 kg/m3, which can have potential use in civil engineering, both as insulation from heat and sound, and for load-bearing structures. However, due to the nature of the cement material and its high porosity, FC is very weak in withstanding tensile loads; therefore, it often cracks in a plastic state, during shrinkage while drying, and also in a solid state. This paper is the first comprehensive review of the use of man-made and natural fibres to produce fibre-reinforced foamed concrete (FRFC). For this purpose, various foaming agents, fibres and other components that can serve as a basis for FRFC are reviewed and discussed in detail. Several factors have been found to affect the mechanical properties of FRFC, namely: fresh and hardened densities, particle size distribution, percentage of pozzolanic material used and volume of chemical foam agent. It was found that the rheological properties of the FRFC mix are influenced by the properties of both fibres and foam; therefore, it is necessary to apply an additional dosage of a foam agent to enhance the adhesion and cohesion between the foam agent and the cementitious filler in comparison with materials without fibres. Various types of fibres allow the reduction of by autogenous shrinkage a factor of 1.2–1.8 and drying shrinkage by a factor of 1.3–1.8. Incorporation of fibres leads to only a slight increase in the compressive strength of foamed concrete; however, it can significantly improve the flexural strength (up to 4 times), tensile strength (up to 3 times) and impact strength (up to 6 times). At the same time, the addition of fibres leads to practically no change in the heat and sound insulation characteristics of foamed concrete and this is basically depended on the type of fibres used such as Nylon and aramid fibres. Thus, FRFC having the presented set of properties has applications in various areas of construction, both in the construction of load-bearing and enclosing structures.