Explore the vast range of titles available.

Sustainable and resilient construction materials are key factors influencing the structural integrity and durability of concrete. Incorporation of polypropylene fibres has become a pivotal strategy to improve shrinkage reduction and crack resistance. The necessity of intensified exploration pertaining to synergistic use of polypropylene fibres with different cementitious materials led to the formulation of this study. 12 mm polypropylene fibres with low volume dosage 0.1%,0.2% and 0.3% with respect to concrete volume was optimized. The combination included commercially available binders like Ordinary Portland cement (OPC) and Portland pozzolana cement (PPC) for which fibrous concrete (M40 grade) behavior was investigated. Compressive strength had inverse relation with fibre dosage, 0.2% fibre dosage in OPC and PPC concrete showed marginal similarity with control non fibrous mixes with a strength of 52.24 MPa and 47.7MParespectively. Split tensile strength improved up to 3.7% and 6.4% for 0.3% fibre dosage in OPC and PPC concrete respectively. Overall improvement of flexural strength was marginal up to 2% and 8.2% for 0.3% fibre dosage in OPC and PPC concrete respectively. The results depicted the synergistic combination of pozzolans and fibres. Good quality concrete with pulse velocity range between 3.75 km/s-4.40 km/s was observed for all the set of variations reaffirming the suitability of concrete in structural applications. However, it is observed that permeability increase was within 20% for both the set of concrete with varying fibre dosages. Microstructure image depicted balling of fibres for 0.3% dosage of fibres.

The cement industry is a significant contributor to CO 2 emissions worldwide, which demands new measures to reduce its environmental impacts. Therefore, finding solutions to reduce the CO 2 emissions in cement production became necessary. Pozzolanic materials offer an optimum solution approach with both environmental and functional advantages. For the investigation of pozzolan effects on the concrete mixture, the modeling part becomes a challenging task. This study models and predicts the compressive strength of pozzolanic cement-based concrete using deep residual neural networks (DRNNs) and variance-based sensitivity analysis (VBSA). The designed DRNNs architecture uses shortcuts (i.e., residual connections) that bypass some layers in the deep network structure in order to alleviate the problem of training with high accuracy. The research also examines crucial aspects such as pozzolan type, substitution ratio, component proportions, and grinding processes, using data developed by the authors and from different pozzolanic concrete compositions from various studies. The proposed model showed a high accuracy of R 2  = 0.94 for testing data that outperformed traditional literature models, enabling the generation of a large sample of synthetic experimental data for further analysis. The VBSA improves knowledge by prioritizing the importance of input factors, resulting in a complete method for designing concrete mixes. The analysis revealed that silica fume and volcanic ash were the most effective pozzolans in enhancing compressive strength, followed by scoria and metakaolin, with optimal substitution ratios ranging from 10 to 15% for most natural pozzolans and up to 20–30% for metakaolin and pumicite. Hence, this newly presented analysis framework offers an optimizing tool for pozzolanic concrete mix design that could investigate several pozzolana types/proportions, their efficiency, and the structural performance of the final concrete mixture.

Current study aims to ascertain the harmful effects of pozzolanic cement (PC) on water quality and several indicators of aquatic life. Also, the effects of PC on different life stages of rainbow trout were investigated. The PC caused an increase in various water quality parameters including pH, suspended particles, turbidity, and conductivity. In rainbow trout, no significant differences were observed between control and experimental groups in terms of enzyme parameters. Also, this study revealed that the PC has impact on various hematological parameters. The PC was linked to histological changes in gills, DNA migration was observed in the rainbow trout exposed to PC. After 24 h, LC50 values of rainbow trout exposed to PC were 499.06, 324.66, and 361.26 mg/L for egg, alevine, and fry respectively. There was adverse relation between temperature and LC50. Consequently, cement pollution in the water and different stages of rainbow trout causes various negative effects.

Recycling wastewater from washing concrete trucks in concrete production addresses both economic and sustainability needs. In the present article, wastewater from washing concrete trucks was added to cement pastes made with two different types of cement for comparison. OPC type CEM I 42.5 was compared to pozzolanic cement type CEM IV/B (P-W) 32.5 in terms of hydration behavior and compressive strength development. The hydration of ordinary Portland cement (CEM I 42.5) was accelerated, while the hydration of pozzolanic cement (CEM IV 32.5) showed a relatively lower total normalized heat. Cement pastes were produced from both cement types, and compressive strength, thermal analysis, and setting time tests were performed for their characterization. The early-age kinetics and compressive strength development of CEM I 42.5 pastes indicate that hydration with wastewater leads to a slight increase in compressive strength. Test concrete prepared with pozzolanic cement (CEM IV 32.5) exhibited increased capillary voids, which contributed to less favorable mechanical and durability performance. Compared to the reference concrete, compressive strength was reduced by 7% at 28 days. Wastewater utilization increased the initial absorption rate by approximately 20%, but the calculated chloride content at the exposed concrete surface decreased after the addition of wastewater compared to the control mix. The carbonation depth of concrete with wastewater increased by 1–2 mm, with an uneven penetration zone, but the compressive strength after carbonation increased. Overall, the type of cement used appears to significantly influence the performance of concrete prepared with wastewater. For wastewater collected from sedimentation tanks, replacing fresh water at a 100% rate and using it with pozzolanic cement to produce concrete, it seems that the mechanical properties and durability are only slightly affected.

Cement industry produces the 7% of the global CO2 emission. The most effective way to decrease CO2 emission of cement industry is the substitution of a proportion of cement with supplementary cementing materials. Metakaolin (MK) is a silica-based product that, on reaction with Ca(OH)2 (CH), produces C–S–H gel at ambient temperature. MK also contains alumina that reacts with CH to produce additional alumina-containing phases, including C4AH13, C2ASH8 and C3AH6. The aim of our research is to investigate the effect of MK up to 20 mass% substitutions of OPC on the hydration characteristics of MK-blended cement pastes. The physico-chemical properties of the hardened cement pastes were studied up to 90 days of hydration. The hydration products of some selected samples were investigated using XRD, DTA and TG techniques. The results indicated that substitution of up to 20 mass% OPC by MK as a pozzolanic materials resulted in an increase in the standard water of consistency, acceleration of the initial setting times, high compressive strength values at earlier ages and improvement of the mechanical, durability properties as well as performance of MK pozzolanic cement pastes.

Acidic attack represents a topic of increasing significance, owing to the spread of damages of concrete structures in both urban and industrial areas. Cement type is an important factor affecting performance of cement based materials in an aggressive environment. The goal of this study was to compare the acid resistance of a pozzolanic cement (CEM IV-A/32·5) with Portland cement (CEM I 32·5) that was made from the same clinker. For this purpose, 50mm mortar cubes were prepared with two different kinds of cement according to TS EN 196-1. After 28 days of hardening, the samples were immersed into four different concentrations of hydrochloric, nitric and sulfuric acid solutions for a period of 120 days. The changes in weight loss and compressive strength values for each acid solution within the test period were recorded. The acid resistance of mortars made from Portland cement was better than the pozzolanic cement incorporated samples after 120 days of acid attack.

This research intends to investigate and analyze the usage of Jordanian oil shale ash (OSA) as a replacement material for ordinary Portland cement and pozzolanic cement in mortar. To start, oil shale was collected from the Wadi Al-Shallala location, crushed, sieved and burned at 800 °C for 24 h. OSA partially replaced the ordinary Portland and pozzolanic cements with ratios of 10%, 20%, and 30%. This research looked into the effect of cement substitution on the standard consistency and hardening time for cement paste. The water contents as well as beginning and final hardening times increased due to the higher replacement ratios of the cements. Also, pozzolanic activity index (PAI) along with scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) testing and mechanical properties (compressive and flexural strengths) of mortar with both types of cement substitution were evaluated. The compressive strength and flexural strength were checked following 3, 7, 14, 28, 56 and 90 days of curing, while (SEM) was conducted just at 28 days old with a 20% replacement ratio in mortar specimens. Results show that 20% OSA substitution for ordinary Portland cement or Pozzolanic cement raises compressive strength and flexural strength, plus provides better morphology. Thus, oil shale is seen as a natural pozzolanic material that increases efficiency in cement mixtures.

In recent years, the use of supplementary cementitious materials (SCMs) in building materials has increased due to concerns about CO 2 emissions from the cement industry. On the other hand, the scarcity of traditional sources of SCMs in certain regions exacerbates the issue of high demand for these materials in concrete production. In this context, this article explores the chemical, mineralogical, morphological, and physical properties and pozzolanic activity of two types of diatomaceous earth (DE) obtained from industrial waste and by-products. The waste was classified into two categories: low-density DE (DE-LD) and high-density DE (DE-HD), representing particles attached to the cyclone wall and those lacking suitable characteristics for use as filter material and/or loading agent, respectively. Results showed that both DE types are rich in silicon oxide and have a highly porous surface. DE-LD and particles smaller than 0.075 mm of DE-HD contain more amorphous phases. DE-HD consists of a mixture of quartz sand and DE particles. Both DE types have a lower apparent specific mass compared to cement, with DE-LD standing out for its high specific surface area (~ 8.7 times that of cement) and uniform particle size distribution. Pozzolanic activity tests indicate that DE-LD exhibits greater reactivity, whereas the < 0.075 mm fraction of DE-HD displays latent hydraulic behavior, likely due to the presence of amorphous silica. Based on these findings, DE-LD can serve as SCMs due to its pozzolanic characteristics, while DE-HD (< 4.75 mm) can be used as fine aggregate in concretes and mortars or as SCMs after sieving to obtain particles smaller than 0.075 mm. Thus, these waste materials show potential for use in the production of pozzolanic cements, mortars, and concretes, contributing to the valorization of waste that would otherwise be disposed of improperly and helping to address SCMs shortages.

This study reports an experimental program involving delayed ettringite formation (DEF) of composites with several pozzolanic cements. Mortars were prepared using a standard mix in the presence of 6 cements. DEF was induced by thermal curing (Peak of 85°C). Laboratory assessments included expansion measurements, mechanical properties, and microstructural analyses. Results indicate that pozzolanic cements produced less damage from DEF in comparison to a cement with no pozzolan. Whereas mortars containing pozzolanic cements showed less expansions ranging between 0.10% and 0.20%, reference mortar (with no pozzolan) exhibited larger expansions, up to 0.40%). Nevertheless, the level of expansion and negative impacts on mechanical properties proved that DEF was not able to be mitigated. Furthermore, pozzolans appeared just to delay damages from DEF. The use of pozzolans in the production of Portland cements contributes to a reduction of cement and, thus, CO2, and must be considered in the mix designs of concretes improving durability in front of external agents. Nevertheless, studies on hydration heat of cements, prediction of internal temperature of concrete and also limitation of curing temperature must be considered before concrete placement in structures to avoid risks of thermal cracking and also an internal sulfate attack by DEF.

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.