Hybrid Cement Research Articles

Shrinkage and Creep Properties of Low-Carbon Hybrid Cement.

Hybrid cements combine clinker with large amount of supplementary cementitious materials while utilizing hydration and alkali activation processes. This paper summarizes shrinkage and creep properties of industrially produced H-cement, containing only 20% of Portland clinker. In comparison with a reference cement CEM II/B-S 32.5 R, autogenous shrinkage is smaller after 7 days, and drying shrinkage is similar at similar times. A different capillary system of H-cement leads to faster water mass loss during drying. Basic and total creep of concrete remains in the standard deviation of B4 and EC2 creep models. The results demonstrate that shrinkage and creep properties of concrete made from H-cement have similar behavior as conventional structural concrete or high-volume fly ash concrete.

Effect of Radiotherapy on the Adhesive Interface of Caries-affected Dentin and Bioactive Restorations: A Micro-CT Analysis.

This study aimed to analyze the presence of defects within the adhesive interface formed with five bioactive dental materials and caries-affected dentin concerning the timing of radiotherapy (before or after the restorative procedures) by micro-CT. A total of 96 carious human molars were randomly allocated into the following groups based on the timing of the radiotherapy sequence: radiotherapy followed by restoration (RT1) or restoration followed by radiotherapy (RT2). Then, six subgroups were established within these groups based on the type of materials used (n=8). Following cavity preparation and caries removal, a universal adhesive (G-Premio Bond) was administered in self-etch mode or accompanied by applying suitable cavity conditioners according to the manufacturers' guidelines. Subsequently, restorations were performed using five bioactive restorative materials (resin-modified glass-ionomer [Fuji II LC], high-viscosity glass-ionomer hybrid [EQUIA Forte HT], giomer [Beautifil II], alkasite [Cention N], and dual-cure bulk-fill composite [Activa Bioactive Restorative]) and a conventional microhybrid resin composite (Filtek Z250). The radiotherapy regimen encompassed 60 Grays (Gy) administered at a rate of 2 Gy/day over 6 weeks, 5 days a week. Micro-CT analysis was employed to assess adhesive defects at the interface between caries-affected dentin and the restorations. The data were analyzed using Kruskal-Wallis, Mann-Whitney U, and Dunn tests (α=0.05). RT2 caused significantly higher adhesive defects than RT1 for the Filtek Z250 and Activa Bioactive Restorative subgroups (p<0.05). For RT1, no significant differences were found in adhesive defects among all tested subgroups (p>0.05). By contrast, for RT2, adhesive defects were significantly higher for the Activa Bioactive Restorative and Cention N subgroups than for the EQUIA Forte HT and Beautifil II subgroups (p<0.05). When using most bioactive restorative materials, the timing of radiotherapy had no significant influence on the adhesive interface. Regarding restoration following a radiotherapy protocol, a favorable impact was identified with high-viscosity glass ionomer hybrid cement and giomer bioactive restorations compared with dual-cure bioactive bulk-fill composite and alkasite restorations.

Effect of alkaline carbonate-based activators on the properties of one-part ternary hybrid cement

This paper investigates the use of solid alkaline carbonates (Na2CO3 and K2CO3) as activators for the production of one-part hybrid cement from a combination of three precursors: blast furnace slag, metakaolin, and clinker. The impact of activator dosage and the nature of the alkaline cation (Na+ or K+) on the compressive strength (Cs) and microstructure of the elaborated materials was studied. The results indicate that the highest Cs values are achieved with 5 % Na2CO3. The analysis of the reaction products’ microstructure reveals that the inclusion of Na2CO3 mainly produces (N,C)-A-S-H and C-A-S-H cementitious gels, along with metastable carboaluminates and different types of calcium carbonate. Additionally, the presence of K2CO3 results in the creation of hemicarboaluminate.

Sustainable Hybrid Lightweight Aggregate Concrete Using Recycled Expanded Polystyrene.

Global concrete production, reaching 14×1013m3/year, raises environmental concerns due to the resource-intensive nature of ordinary Portland cement (OPC) manufacturing. Simultaneously, 32.7×109 kg/year of expanded polystyrene (EPS) waste poses ecological threats. This research explores the mechanical behavior of lightweight concrete (LWAC) using recycled EPS manufactured with a hybrid cement mixture (OPC and alkali-activated cement). These types of cement have been shown to improve the compressive strength of concrete, while recycled EPS significantly decreases concrete density. However, the impact of these two materials on the LWAC mechanical behavior is unclear. LWAC comprises 35% lightweight aggregates (LWA)-a combination of EPS and expanded clays (EC) - and 65% normal-weight aggregates. As a cementitious matrix, this LWAC employs 30% OPC and 70% alkaline-activated cement (AAC) based on fly ash (FA) and lime. Compressive strength tests after 28 curing days show a remarkable 48.8% improvement, surpassing the ACI 213R-03 standard requirement, which would allow this sustainable hybrid lightweight aggregate concrete to be used as structural lightweight concrete. Also obtained was a 21.5% reduction in density; this implies potential cost savings through downsizing structural elements and enhancing thermal and acoustic insulation. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy reveal the presence of C-S-H, C-(A)-S-H, and N-A-S-H gels. However, anhydrous products in the hybrid LWAC suggest a slower reaction rate. Further investigation into activator solution dosage and curing temperature is recommended for improved mechanical performance on the 28th day of curing. This research highlights the potential for sustainable construction incorporating waste and underscores the importance of refining activation parameters for optimal performance.

Effect of a Hybrid Pumice-Portland Cement Extract on Corrosion Activity of Stainless Steel SS304 and Carbon Mild Steel A36.

The change in the corrosion activities of SS304 and the carbon steel A36 were studied during their exposure for 30 days to hybrid pumice-Portland cement extract (CE), to simulate the concrete-pore environment. The ionic composition and the initial pH (12.99) of the CE were influenced by the reduction of Portland cement (PC) content, volcanic pumice oxides and alkaline activators. Because of the air CO2 dissolution, the pH decreased and maintained a constant value ≈ 9.10 (established dynamic ionic equilibrium). The CE promoted the passivation of both steels and their free corrosion potential (OCP) reached positive values. On the surfaces, Fe and Cr oxides were formed, according to the nature of the steel. Over the time of exposure, the presence of chloride ions in the pumice caused a localized pitting attack, and for carbon steel, this fact may indicate an intermediate risk of corrosion. The chloride effect was retarded by the accumulation of SO42- ions at the steel surfaces. Based on electrochemical impedance (EIS), the polarization resistance (Rp) and the thickness of the passive layers were calculated. Their values were compared with those previously reported for the steels exposed to CEs of Portland and supersulfated cements, and the hybrid cement was considered as a PC "green" alternative.

Corrosion of ribbed carbon steels in ecological mortars and its influence on their rotative fatigue behavior

Ribbed carbon steel rebars were embedded in mortars manufactured with three different eco-friendly binders (alkali-activated slag, and slag and fly ash-based hybrid cements) and with a commercial cement (CEM IV). This research evaluates the corrosion of reinforcements, fully assessed by natural diffusion, and its impact on the fatigue performance of the bars. Results obtained after 17-month corrosion testing on reinforced innovative mortars reveal that different pit morphologies and locations appear on the bars depending on the mortar composition, with the extent of the attack being related to the pH and the free-chloride content in each mortar. Rotative fatigue tests of the corroded bars have proven that the reduction of the fatigue life is dependent on the global extent of the corrosive attack, when the shape and distribution of the pits correspond to those generated exclusively by chloride diffusion in mortars. Bars corroded in alkali-activated slag and CEM IV mortars shown the best fatigue performances.

Investigating the impact of alkaline activator on the sustainability potential of geopolymer and alternative hybrid materials

Geopolymer binders are considered highly sustainable due to their utilization of industrial wastes. However, previous studies highlight the limited industrial-scale applications of geopolymers. Therefore, this study critically investigates the strength, cost, and environmental impact of geopolymers and alternative hybrid cement mixes to provide a complete picture for the sustainability analysis. Geopolymers and hybrid cement mixes are designed with varying proportions of alkaline activator (sodium hydroxide 5–25 wt%) and ordinary Portland cement (OPC) (15–35 wt%) respectively for the comparative analysis. The strength characteristics of designed mixes have been assessed by analyzing their compressive strength and microstructure. A comparative economic assessment has been made by contemplating the manufacturing and production costs of different materials used in geopolymer and hybrid cement mixes. ReCiPe Midpoint Life cycle assessment (LCA) has been performed to examine the environmental performance by considering the manufacturing and production processes of various binder and aggregate materials used in geopolymer and hybrid cement mixes. Mechanical and microstructural analysis shows that hybrid cement mix with 35 wt% of OPC yields the highest strength due to the formation of excess calcium aluminum silicate hydrate (C-A-S-H) and calcium silicate hydrate (C–S–H) gels than geopolymer mix containing 25 wt% of NaOH. Economic and life cycle assessment reveals that the geopolymer mix with 5 wt% NaOH offers the lowest cost and environmental impact as compared to others containing higher proportions of alkaline activator and OPC. Owing to the conflicting nature of the results, multi-criteria decision making approach has been used which presents the hybrid cement mix (with 35 wt% OPC) as the optimal and sustainable solution for the construction applications. The study's findings offer a sustainable direction for the construction industry by suggesting the application of hybrid concretes.

Alkaline activation of brick waste with partial addition of ordinary Portland cement (OPC) for reducing brick industry pollution and developing a feasible and competitive construction material

This study shows an alkaline activated cement (AAC), also known as geopolymer, made from red brick waste with partial addition of Ordinary Portland Cement (OPC). This is a sustainable material since incorporates waste from the brick industry to make cements, therefore increasing the materials circularity and this reducing pollution. The material was cured at room temperature. The brick residue was activated with sodium hydroxide and sodium silicate in aqueous solution to form the hybrid cement. Several mixtures were made with different amounts of waste and proportions of alkaline activator. The mechanical properties of the materials were studied to determine their feasibility to be used in the construction sector. Three contents of OPC were used: 10, 20, and 30 wt%, which were added to improve the mechanical behavior and post-curing time. The activated hybrid cement was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), compression, and flexural tests. The main results show that the addition of OPC to the brick derived AAC produces an increased compressive strength of 106 MPa when 30 wt% OPC was added, a very significant result since the control sample found was 33 MPa in compression strength, an improvement for more than 3 times. The data were corroborated by statistical analysis.

Sulphate-based activation of a binary and ternary hybrid cement with portland cement and different pozzolans

The purpose of this study was the development of a hybrid cement based on ordinary Portland cement (OPC) and different sulfate-based alkaline activated pozzolans using the one-part method dosed in binary and ternary mixtures. The factors evaluated were the percentage and type of pozzolan between fly ash, tepojal and volcanic sand and the use of alkaline activators between sodium and potassium sulfate. The amount of cement in conjunction with the use of alkaline activators benefits the reaction of the pozzolans, reducing the setting time according to isothermal calorimetry due to the consumption of portlandite when reacting with the pozzolans, which can be observed with the derivative of thermogravimetry at approximately 450°C. The shift of the main peaks in FTIR implies the reaction of the cementitious compounds towards the thermodynamically stable phase of C-A-S-H. The ternary mixture of OPC-Fly Ash-Tepojal/Volcanic Sand activated with 4% sodium sulfate are presented as the dosages with the best mechanical performance based on compressive strength due to a synergy effect between pozzolans. Tepojal and volcanic sand are chemically and physically presented as an eco-efficient alternative to natural pozzolan for use as cementitious material.

Outcomes of Metaphyseal Cones and Stem Fixation Following Rotating Hinge in Complex Primary and Revision Total Knee Arthroplasty

BackgroundAlthough hinged prostheses have been used successfully in complex revision total knee arthroplasty (TKA), concerns exist regarding early failure due to aseptic loosening and other mechanical complications. The use of metaphyseal cones and hybrid cement fixation have been studied in unlinked constrained primary or revision TKA, but their impact on the survivorship of hinged prostheses has yet to be investigated. MethodsWe identified a consecutive series of 164 hinged prostheses and collected data on demographics, indications, complications, and re-revisions in patients who had fully cemented versus hybrid stems, with and without metaphyseal cones. A multivariate analysis was performed to identify independent variables associated with re-revision as the primary end point. ResultsIn total, 84 patients (51.2%) had fully cemented stems, and 80 patients (48.8%) had hybrid stems. Cones were used in 73 patients (44.5%). At a mean follow-up of 3.4 ± 2.2 years, 42 patients underwent re-revision (25.8%), most commonly for infection (12.2%), followed by loosening (6.7%) and periprosthetic fracture (3.7%). Patients who had fully cemented stems had lower re-revision rates than hybrid fixation constructs (19 versus 26%, P = .043). Using multivariable regression, a construct with hybrid fixation with cones (odds ratio = 2.39; P = .037) was an independent risk factor for failure. Utilization of cones alone did not have an effect on re-revision rates at 3.4-year follow-up. ConclusionsWhile we found no difference with the use of cones, patients undergoing revision TKA with a hinge prosthesis and fully cemented stems had better overall survivorship than hybrid stems.

Exploring diatomite as a novel natural resource for ecofriendly-sustainable hybrid cements

The primary goals of the present study are to decrease CO2 emissions and minimize the excessive consumption of natural resources associated with cement production. The main natural resource was diatomite (DIO), a naturally abundant material found in several regions of Mexico. Four different hybrid cement (HC) mixtures were prepared using NaOH, while maintaining a consistent OPC percentage of 10 % across all the mixtures. The obtained results demonstrate the exceptional performance of one of these HC mixtures, surpassing OPC properties in terms of compressive strength at 1, 7 and 28 days, with values of 28.8, 47.16 and 62.9 MPa, respectively. The outstanding HC mixture underwent thorough confirmation through a range of analyses, such as TG, FTIR, SEM and EDX. This innovative HC composite offers several solutions to reduce CO2 emissions and conserve natural resources currently wasted in cement manufacturing, making it a compelling choice for various industrial and construction applications.

Development of paste-like organic/inorganic artificial bones compatible with bone remodeling cycles, consisting of β-tricalcium phosphate, calcium sulfate hemihydrate, and poly(lactic-co-glycolic acid) particles

Schematic illustration of organic/inorganic hybrid cement with the simultaneous addition of CSH and PLGA particles.

Eco-friendly hybrid binders based on waste from the chemical industry

The purpose of the study is to show the possibility of using high-tonnage waste from the chemical industry in the production of building materials. Methods and materials. Methods of data comparison and analysis were used. Solid residues of distiller sludge with a moisture content of 25-30%, an active calcium oxide content of 12-13% and quartz sand with a grain size of 2.2, humidity of 5-6% were used as materials. Results. Compositions and methods for obtaining a cement-free binder based on the solid residue of soda and quartz sand production are proposed. The possibility of obtaining a binder based on the solid residue of distiller slurries according to two technological schemes: drying of the solid residue and grinding together with quartz sand; firing of the solid residue and grinding together with quartz sand, has been confirmed by our tests. The introduced concept of “Eco-friendly hybrid cements” (Eco-friendly hybrid binders (EHB)) emphasizes that they are binders made up of multicomponent mineral raw materials of secondary resources. Practical significance. Solid by-products of the chemical industry can be used as an auxiliary inorganic component. This will make it possible to create eco-friendly hybrid cements ready for use, which are sealed only with water, which contributes to the development of such binders by industry and the rational use of secondary mineral resources.

Strength, porosity and life cycle analysis of geopolymer and hybrid cement mortars for sustainable construction

Owing to the application of industrial wastes, geopolymers are generally regarded as a sustainable alternative to traditional construction materials. However, their lack of adoption on the industrial scale demands detailed investigations. This study conducts a comparative analysis of the compressive strength of different geopolymer and hybrid cement mortars with varying proportions of sodium hydroxide (from 5 to 25 wt%) and ordinary Portland cement (OPC) (from 15 to 35 wt%), respectively. The porosity of all designed mixtures was also analyzed using X-ray computed tomography (XCT) and water absorption tests. ReCiPe 2016 Midpoint (H) method was used for the Life cycle analysis of the geopolymer and hybrid cement mortars. Multi-criteria decision making (MCDM) approach was used to assess the sustainability potential of the designed mixtures based on compressive strength, porosity and overall environmental impact. Experimental results revealed that the increase in sodium hydroxide in geopolymer mortars up to 15 wt% offered its maximum compressive strength. Superior compressive strength was obtained at 35 wt% of OPC in hybrid cement mortars due to the formation of more C-S-H, C-A-S-H and N-A-S-H gels which fill up the voids and pores. Analysis of the macro and micro-porosity revealed that hybrid cement mortars yield denser structure than geopolymer mortars. Life cycle analysis based on 8 distinct impact categories showed that hybrid cement mortars outperform the geopolymers in all impact categories except ‘mineral resource scarcity’. However, the overall environmental impact assessment using the ‘coefficient of performance’ depicts that hybrid cement mortars offer a significantly lower environmental burden than geopolymers. MCDM analysis shows that hybrid cement mortar with 5 wt% of sodium hydroxide and 35 wt% of OPC is the best choice for construction applications. This idea of sustainable hybrid cement mortar will be helpful for the construction industry to limit the environmental impact without compromising their structural performance.

Characteristics of micro structure and strength development of alkali activated GGBS-FNS hybrid cement

A study was conducted to improve the performance of FNS (ferronickel slag) and GGBS (ground granulated blast furnace slag) incorporated in cement with alkali activator. First, setting time, compressive strength and ultrasonic pulse velocity were measured to evaluate the physical properties of FNS incorporated cement mixed. After that, the morphology of cement matrix was confirmed through XRD, DTG, SEM and MIP analysis. As a result, it was confirmed that, despite the use of an alkali activator, FNS adversely affected the physical properties of the mixed cement due to its low alkalinity. On the other hand, it was confirmed that a proper alkalinity and excellent physical properties were obtained when FNS was used with GGBS. Moreover, it was observed that the activation effect of the alkali activator was further amplified in the ternary blended cement. Therefore, it seems appropriate to mix FNS up to 30%, and it is suitable to be used in ternary blended cement.

Influence of NaOH molarity and Portland cement addition on performance of alkali activated cements based in silicomanganese slags

The aim of this research is to explore the potential of recycling the waste of silicomanganese slag (SiMnS) from the ferroalloy industry in the synthesis of alkali-activated cements. The influence of the concentration of the activator NaOH (4, 6, 8, and 10 M) and the partial substitution of the waste with Portland cement (PC) (10–30 wt%) on the technological properties and microstructure of binders cured at room temperature has been studied. The SiMnS binders and the hybrid cements incorporating PC have been characterized using X-ray diffraction analysis (XRD), infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) combined with energy-dispersive spectroscopy (EDS). The results indicate that compressive strength improve with an increase in molarity from 4 to 6 M from 7.8 up to 14.0 MPa, respectively, at 28 curing days. Similar mechanical properties are observed for higher molarity increments (8 M and 10 M) (12.9 and 13.6 MPa, respectively). The main reaction product formed is a (C,N)-A-S-H gel with different morphologies. Partial substitution of SiMn slag with PC led to hybrid cements with a denser structure due to a greater amount of C-S-H gel, coexisting with C,N-A-S-H gel. Therefore, the optimal combination of SiMn slag (70 wt%) and PC (30 wt%) significantly enhances the technological properties of the SiMn slag binders obtaining optimum compressive strengths of 24.7 MPa. The results of this study demonstrate that silicomanganese slag can be utilized as an environmentally friendly solution in the production of binders and hybrid cements that meet the required technical specifications and standards for use and application in the construction sector in the line of current circular economy policies and Sustainable Development Goals.

Hybrid Cements and Construction Elements Based on Alkaline Activation with Sodium Sulfates from Fly Ash and Construction and Demolition Waste.

This article demonstrates the possibility of producing hybrid cementitious materials (pastes, mortars, concretes, and precast elements) based on fly ash (FA) and construction and demolition wastes (CDW) using alkaline activation technology. Sodium sulfate was used as an activator and fine and coarse aggregates were obtained from CDW residues. An addition of Portland cement (OPC) (10 to 30%) allowed for improvement in the mechanical behavior of the hybrid cements and them to be cured at room temperature (25 °C). The FA and CDW cementitious materials obtained compressive strengths of 37 MPa and 32 MPa, respectively. The compressive strength of FA and CDW alkali-activated concretes at 28 days of curing was 22 MPa and 18 MPa, respectively, which identifies them as structural concretes according to NSR-10 title C in Colombia. The potential use of these concretes was validated by obtaining and classifying precast materials.

Application of hybrid cement in passive fire protection of steel structures

PurposeThe aim of this paper is to determine the thermal conductivity of a protective layer of alkali-activated cement and the possibility of performing fire protection with fireclay sand and Lightweight mortar. Unprotected steel structures have generally low fire resistance and require surface protection. The design of passive protection of a steel element must consider the service life of the structure and the possible need to replace the fire protection layer. Currently, conventional passive protection options include intumescent coatings, which are subject to frequent inspection and renewal, gypsum and cement-based fire coatings and gypsum and cement board fire protection.Design/methodology/approachAlkali-activated cements provide an alternative to traditional Portland clinker-based materials for specific areas. This paper presents the properties of hybrid cement, its manufacturability for conventional mortars and the development of passive fire protection. Fire experiments were conducted with mortar with alkali-activated and fireclay sand and lightweight mortar with alkali-activated cement and expanded perlite. Fire experiment FE modelling.FindingsThe temperatures of the protected steel and the formation of cracks in the protective layer were investigated. Based on the experiments, the thermal conductivities of the two protective layers were determined. Conclusions are presented on the applicability of alkaline-activated cement mortars and the possibilities of applicability for the protection of steel structures. The functionality of the passive fire layer was confirmed and the strengths of the mortar used were determined. The use of alkali-activated cements was shown to be a suitable option for sustainable passive fire protection of steel structures.Originality/valueEco-friendly fire protection based on hybrid alkali-activated cement of steel members.

Factors Affecting the Setting Times of Pumice Based Alkali-Activated Hybrid Cements

Factors Affecting the Setting Times of Pumice Based Alkali-Activated Hybrid Cements

3D Printing of Hybrid Cements Based on High Contents of Powders from Concrete, Ceramic and Brick Waste Chemically Activated with Sodium Sulphate (Na2SO4)

This article evaluates the synthesis, characterization and 3D printing of hybrid cements based on high (70%) contents of powders from concrete waste (CoW), ceramic waste (CeW) and red clay brick waste (RCBW) from construction and demolition waste. For the synthesis of the hybrid cements, 30% (by weight) of ordinary Portland cement (OPC) was added. Sodium sulphate (Na2SO4) (4%) was used as a chemical activator. The effect of the liquid/solid ratio on the properties in the fresh state of the mixes was studied by means of minislump, flowability index, and buildability tests. The compressive strength was evaluated at 3, 7, 28 and 90 days of curing at room temperature (≈25 °C), obtaining strengths of up to 30.7 MPa (CoW), 37.0 MPa (CeW) and 33.2 MPa (RCBW) with an L/S ratio of 0.30. The results obtained allowed selecting the CoW 0.30, CeW 0.33 and RCBW 0.38 mixes as optimal for carrying out 3D printing tests on a laboratory scale, successfully printing elements with good print quality, adequate buildability, and compressive strength (CoW 0.30 = 18.2 MPa, CeW 0.33 = 27.7 MPa and RCBW 0.38 = 21.7 MPa) higher than the structural limit (≥17.5 MPa) established for concrete by Colombian Regulations for Earthquake Resistant Construction (NSR-10).