Ordinary Portland Cement Mortar Research Articles

Optimization and characterization of sustainable geopolymer mortars based on palygorskite clay, water glass, and sodium hydroxide

Abstract The synthesis of ambient-cured sustainable geopolymer mortars (GMs) was studied throughout this work. To reduce carbon dioxide emissions, new materials must be used in the production of sustainable concrete and mortars. Many types of binders are used in the synthesis of GM and concrete (GPC), especially clay minerals. These clay minerals are considered sources of alumina and silica in GM and concrete. The geopolymerization process relies on the alkaline solution activating the alumino-silicate to produce geopolymer gel products. The palygorskite (PA) clay mineral, sodium hydroxide (NaOH), and sodium silicates (Na2SiO3) were chosen as a binder (solid material) and alkaline activator solution to synthesize GM at ambient temperature. PA was thermally treated at 550, 650, 700, and 750°C, respectively, to convert into high-reactive PA (HRP) HRP550, HRP650, HRP700, and HRP750, respectively. The characteristics of PA clay, HRP powders, and HRP-based GM were evaluated using compressive strength (CS) testing, X-ray fluorescence analysis, carbon footprint analysis, X-ray diffraction (XRD) diffractograms, Fourier transform infrared spectroscopy (FTIR) spectroscopy, scanning electron microscopy (SEM) images, and energy-dispersive X-ray spectroscopy (EDS) analysis. The maximum CS of 25.1 MPa was acquired for geopolymer synthesis utilizing HRP700-based GM cured at 30°C for 28 days. FTIR spectroscopy demonstrated that HRP-based GM showed the presence of Si–O, Al–O, and O–C–O bonds stretching vibrations in the alumino-silicate network. The results showed that the CO2 emissions had a reduction in the HRP-based GM compared with the reference mix of ordinary Portland cement mortar (OPM). The percentage of reductions was 14.1, 13.7, 13.1, and 12.4 for HRP550, HRP650, HRP700, and HRP750, respectively, compared with the OPM mixture. SEM images/EDS analysis and XRD diffractograms confirmed the presence of sodium alumino-silicate hydrates, magnesium silicate hydrate, and calcium silicate hydrate gels with high quantities particularly in the HRP700-based GM than that in HRP550, HRP650, and HRP750, respectively. The results indicate the suitability of HRP calcined at 700°C (HRP700) in the synthesis of the GM.

Durability-Related Transport Properties of Limestone Calcined Clay Cement Mortars

This study investigates the effect of utilizing a combination of limestone and calcined clay as cement re-placement on the transport properties that indirectly define the behavior of the matrix throughout its service life, such as total porosity, water absorption due to capillary action, water permeability penetration, chlorine diffusion, and car-bonation depth. Mortars were made of blends with different levels of cement replacement (%15, %30, %45) by a substi-tution ratio of 2:1 (calcined clay: limestone), with adjusted gypsum content in each system composition. Furthermore, the influence of kaolinite content in clays on transport prop-erties was also investigated. Based on the results, all LC3 blends exhibited a significant improvement in terms of total porosity, capillary water absorption, water penetration re-sistance, and chloride diffusion compared to OPC mortars. Moreover, the higher the replacement level of cement, the higher the resistance to movement or transport of ion spe-cies through the mortars. The improvement in the transport properties for LC3 blends can be attributed to its enhanced porosity refinement as well as the enhanced chloride bind-ing capacity. In contrast, a slight improvement in the transport properties was observed with increasing the kao-linite content of the calcined clays. This result indicates that utilizing low-grade calcined clay has no significant effect on the transport properties. The carbonation resistance of the LC3 blends was lower as compared to OPC. Furthermore, increasing the cement substitution rate resulted in a pro-gressive decrease in carbonation resistance. Overall, an in-crease in cover depth would be required to achieve a similar service life in terms of carbonation as that of the OPC.

Utilizing calcined and raw fly oil shale ash in the carbonation process of OPC cement-paste and mortar

This study investigates how carbon dioxide (CO2) curing interacts with raw and calcined fly oil shale ash (FOSA) in ordinary Portland cement paste and mortar (OPC), providing information on previously overlooked synergistic effects of CO2 curing and FOSA calcination. Specimens exposed to CO2 curing followed by water curing were compared to those continuously cured in water. The results reveal that samples containing calcined FOSA as a binder increased compressive strength by up to 200% during the curing stages compared to water-cured samples. Microstructural investigations show that calcium carbonate crystals and other hydration products form, which enhance material properties. The substitution of cement with FOSA results in a reduction in porosity regardless of the curing technique used; however, this issue is efficiently managed by CO2 curing. Higher pH values can be measured from raw FOSA samples, and higher calcination temperatures can result in slightly higher pH values, making the phenolphthalein indicator approach less accurate in detecting carbonation. The application of raw and calcined FOSA as a cement substitute gives long-term benefits while also contributing to environmental awareness in the construction sector.

Effect of the titanium-dioxide addition on the structural, dielectric, and mechanical properties of different cement-based mortars with corundum aggregate

The primary objective of this study was to look into the role of titanium dioxide in the production of corundum-based mortars, with a focus on finding the optimal mortar composition for achieving improved mechanical and dielectric performances. Changes in the mix design (different binders, different additive dosages), as well as their effects on the hydration pathway, chemical bonds, phase modifications, and microstructure, were examined. These findings were then correlated to the designed mortars' mechanical strengths and dielectric properties. Experimental mortars were produced with binders made from ordinary Portland cement, high alumina cement, and their mixtures, and corundum as aggregate. Titanium dioxide was employed as an additive (3 and 5wt.%). Nine different mortars were submitted for comprehensive mineralogical and microstructural characterization upon curing and solidification. The compressive and flexural strengths were monitored throughout the 28-day period. The dielectric constant (εr), dielectric loss tangent (tanδ), and electrical resistivity (ρ) were measured over a frequency range of 100Hz to 1MHz. XRD analysis highlighted the appearance of mayenite as a dielectric-prone phase in the samples doped with titanium dioxide. Differential thermal analysis and FTIR spectroscopy identified a higher amount of extra-low crystalline phase in OPC and HAC mortars with TiO2 addition, which accelerated hydration mechanisms, created a surplus of hydration products and made a more compact cement matrix. TiO2 added in 3wt.% amount led to higher mechanical strengths in OPC-based mortars, while it improved the dielectric properties of HAC mortars.

Unveiling the Influence of Varied Alumina Sources on Fresh Properties of Ordinary Portland Cement Mortar and Concrete: A Comprehensive Review

Unveiling the Influence of Varied Alumina Sources on Fresh Properties of Ordinary Portland Cement Mortar and Concrete: A Comprehensive Review

Acoustic Emission monitoring of OPC mortars at elevated temperatures in fracture tests

The action of moderate and high temperatures produces the degradation of main physical and mechanical properties of Ordinary Portland Cement (OPC) composites. As an example, from an application point of view and at a structural level, the case of concrete radiation shielding containers in nuclear facilities can be mentioned, which can be severely affected by thermal cracking. In this work, the results of Acoustic Emission (AE) monitoring of mortar prismatic specimens under three-point bending tests are analyzed. Samples are firstly submitted to a heating treatment in an electrical furnace, with maximum target temperatures ranging between 100 to 600 ºC. After the heating process, the prisms were cooled down and finally, mechanically tested, i.e. under residual conditions. The AE signals were continuously recorded during each bending test and its characteristics at different loading stages were explored, scrutinizing variations in AE parameters, such as event rise time, amplitude and energy. Additionally, average frequency (AF) and RA value parameters were employed to assess fracture modes aiming to highlight situations where tension or shear/mixed modes predominate through the test. A comparative analysis of the AE characteristics during loading path and progressive damage is presented.

Enhancing sustainability and performance in alkali-activated mortars with recycled rubber aggregates subjected to varied curing methods

Rubber waste represents a significant waste stream that can be used as a substitute for natural aggregates in concrete. The main objective of this innovative study is to evaluate the effectiveness of alkali-activated mortars (AAM) incorporating recycled rubber aggregates in the development of an environmentally friendly construction material. Different replacement rates of sand with rubber particles (10%, 20%, and 30% by volume) are analysed. Rubberized alkali-activated mortars (RAAM) were produced using a combination of 10 M sodium hydroxide (NaOH) and a Na_2 SiO_3/NaOH ratio of 3. Additionally, the influence of three curing methods on the properties of RAAM is also examined: air drying, curing in a climate chamber, or in an oven. The properties of RAAM were evaluated through tests including the flow table test, density test, water absorption test, and compressive strength test. Furthermore, the study also assessed the cost-effectiveness and environmental impact of RAAM. This variable study is complemented by an ANOVA parametric analysis. The results show a decrease in the compressive strength and flowability of AAM proportionally to the increase in R content. Experimental and statistical analysis reveal that curing in an oven at 60°C significantly optimizes compressive strength by approximately 50.52%. It is worth noting that this curing method of RAAM has demonstrated superior economic and environmental benefits compared to OPC mortar. The study highlights the strong potential of RAAM cured at 60°C or in a humid chamber, combining mechanical performance with reduced CO_2 emissions, as a sustainable and eco-friendly solution to replace traditional concrete.

Life cycle analysis of sediment valorization by means of geopolymerization from laboratory to industrial scale

Geopolymerization has become a potential competitor to cement over the last 10 years due to its lower carbon impact. However, the development of geopolymerized applications on an industrial scale still faces numerous limits. As an answer, the valorisation of local sources of materials such as dredged sediment as precursors has been identified in the literature of high interest as it could solves sediment management problems as well as reducing geopolymerization environmental and economic cost. Therefore, this study evaluates, through a Life Cycle Analysis (LCA), the impact of mortars developed from untreated dredged sediments mixed with cement or alkalis. The solutions developed in the laboratory were transposed to a hypothetical industrial scale around the Port of Bordeaux area. Four mortars were compared with equivalent mechanical resistance: a classic Ordinary Portland Cement (OPC) mortar and three geopolymer mortars with NaOH and Na2SiO3 alkalis. Results showed that, compared to the use of cement, in this specific case, geopolymerization effectively reduces the impact on climate change by 66% when sediment beneficial recovery was taken into account. This article is a first step in the industrial development adoption of waste geopolymer based mortar for public works as several conclusions were found to justify their implementation on a larger scale. Among them the use of alternative local precursors is effective in order to reduce the environmental cost of geopolymer. However, the market potential of geopolymer mortars will also highly depend on alternatives to silicate as an alkaline reagent.

The pH measurement of cement-based materials: Effect of leaching time, leaching technique and water-to-solid ratio

Corrosion of steel is an electrochemical process that is affected by pH and potential difference. The pH of concrete may change due to physical, chemical, and biological influence over time. Therefore, it is important to measure and monitor the pH of reinforced concrete as a structural health monitoring parameter related to durability. Ex-situ leaching (ESL) method is commonly applied to produce the equilibrated aqueous solutions for the pH measurement of cement-based materials. However, there are limited studies about the effect of leaching time, leaching technique and water-to-solid (w/s) ratio when applying this method. This may lead to underestimation of pH and unnecessary prolonged leaching time. The solution temperature compensated pH value was used during analysis of the data. By testing on the OPC mortar with cement-to-sand ratio of 1:3 and water-to-cement ratio of 0.55, the optimum w/s ratio and minimum leaching time are 2 and 5 min, respectively. The minimum quantity for solid per sample shall not be less than 5.0 g. The findings of this research will contribute to a more accurate pH measurement and may play a part in regulating a standard for cement-based materials.

Effect of long-term drying on the performance of sulfoaluminate cement

The effect of continuous drying for 360 days on the performance of sulfoaluminate cement (SAC) with different contents of gypsum was investigated, with ordinary Portland cement (OPC) selected as the control. First, the compressive strengths and deformation of mortars dried at 40 °C for different times were tested. Meanwhile, for the hardened cement pastes dried under the same condition, the mineral phase, micromorphology, and pore structure evolutions were monitored. Results indicated that the compressive strength of SAC mortars showed a significant decrease after 360 days of drying, whereas the compressive strength of OPC mortar was still higher than that before drying. Moreover, the SAC mortars with high gypsum content exhibited significant shrinkage after drying. This was because the ettringites lost crystal water during the drying process, and the crystallinity decreased gradually until they were amorphous. Meanwhile, the ettringites showed a shriveled morphology after drying, and became weaker than before drying. Besides, both the pore size and total porosities of the SAC hardened cement pastes showed a noticeable increase after 360 days of drying. However, the hydration products of OPC were stable under the same dry condition. This study provides direct evidence to explain the mechanical strength reduction of SAC in service.

Reliability prediction of alkali-activated mortar during flexural loading using Weibull analysis

This study uses the Weibull analysis to predict the robustness of various mortars based on a fracture process analysis through a flexural test recorded by an acoustic emission sensor. Alkali-activated materials (AAMs) are an alternative to Portland cement that can decrease the amount of emitted CO2. This study aimed to characterise and compare the properties of AAM cement mortars to those of the commonly used ordinary Portland cement (OPC) mortars using the Weibull distribution to clarify the reliability and robustness of the prepared AAM cements; four different AAM cement mortar compositions—with fly ash (F), ground-granulated blast-furnace slag (G), and microsilica (M) alkali activation (sodium hydroxide (NaOH) and sodium silicate (Na2SiO3))—were considered in this study. The fracture process under a flexural loading of AAMs was based on four combinations of F/G/M activated by the alkaline solution—AAM-IV, AAM-V, AAM-VI, and AAM-VII, with OPC as control. The Weibull analysis showed that AAMs were more robust than the OPC mortar and possessed minor fractures compared to the OPC mortar.

Effects of flaxseed mucilage and water to cement ratio on mechanical and hydration characteristics of an OPC mortar

Effects of flaxseed mucilage and water to cement ratio on mechanical and hydration characteristics of an OPC mortar

Characteristics of Silica Fume Nano Alumina Ternary Blended Mortar

This study investigates the contribution of nano-alumina (nA: 1–3 wt.% binder) to the performance of silica fume (SF-10%) and ordinary Portland cement (OPC) binary blended mortar. Microstructural analysis and qualitative characterizations examined the fresh (workability, setting time) and hardened (compressive strength and thermal resistance; 300 degrees C for 1 h) properties. Nano alumina (nA) contributed positively to the consistency of SF blended mortar but negatively to that of OPC mortar. The presence of nA retarded the reactivity of calcium and the fluid absorption capacity of SF in the fresh mortar. The initial (180 min) and final (220 min) setting times in SF blended mortar were reduced by 18.4 and 21.8%, respectively, upon adding up to 3% nA. The optimum nA was 2% in the SF–nA ternary blended mortar with 3-d and 28-d compressive strengths of 28 and 43.2 MPa, respectively. These values were reduced by 14.3% and 29.4% in SF-OPC (binary) and 25.2% and 16.7% in OPC mortar, respectively. The nepheline and tobermorite in the SF–nA ternary blended binder provided a denser microstructural density than in SF-OPC and OPC mortars. Finally, SF–nA ternary mortar was more susceptible to carbonation due to the presence of aluminum and calcium carbonates, despite its superior performance in thermal resistance and strength compared to SF blended and OPC mortars.

Investigating the feasibility of producing sustainable and compatible binder using marble waste, fly ash, and rice husk ash: A comprehensive research for material characteristics and production

This research aims to develop a new marble-based binding material for evaluating its strength blended with rise husk ash and fly ash. Newly developed marble-based cement was prepared by burning waste marble powder and clay. The marble cement was then blended separately with varying amounts of fly ash (20, 30, and 40% by mass of marble cement) and rice husk ash (20, 30, and 40% by mass of marble cement) to find the most suitable combination for mortar in terms of strength gain. The mortar specimens were subjected to various load tests, including compressive and flexural strength, and also to various morphology and microstructural tests including X-Ray diffraction, thermo-gravimetric, and scanning electron microscopy analyses. According to the results, the compressive strength of the marble cement mortar was less than ordinary Portland cement mortar but greater than the M1 mortar (5 MPa, minimum compressive strength of mortar for brick masonry) as per the Building Code of Pakistan 2007 (BCP:2007) and Indian Standards (IS:1905). Blended marble cement mortars displayed improved strengths, yet the early strength of blended mortars was lower than Portland cement mortar due to higher di-calcium silicate content and slow pozzolanic activity, but the later-age strength of mortar prepared with the marble cement blended with 30% rice husk ash was found marginally higher than the ordinary Portland cement mortar. Moreover, incorporating marble waste, rice husk ash, and fly ash as binding materials to manufacture building materials will encourage sustainable growth by reducing environmental issues associated with their disposal.

Chloride penetration resistance and chloride binding capacity under different application environments of ferroaluminate cement

Free chloride is a crucial factor that threatens the long-term performance of marine concrete structures. The resistance of cement to chloride penetration and its capacity to bind chloride are important parameters for assessing the ability of cement-based materials to resist chloride invasion. Ferroaluminate cement (FAC) has considerable application potential in concrete used for marine structures; however, its resistance to chloride invasion and mechanism of chloride binding have not yet been revealed. In this study, the chloride diffusion coefficient and chloride binding capacity of FAC, for both internal and external chloride ions, are experimentally investigated and compared with that of ordinary Portland cement (OPC). The results show that the chloride diffusion coefficient of FAC mortar is approximately 2.5 times lower than that of OPC mortar. FAC exhibits finer overall pore distribution and the number of pores with sizes within 10–100 nm is reduced, which is responsible for its notably lower chloride diffusion coefficient. The chloride binding capacity of FAC to internal chloride ions is slightly lower than that of OPC, and a portion of the chloride ions are chemically bound by reacting with ye'elimite during hydration. The chlorides bound by physical adsorption constitute a dominant portion of the entire bound chloride content. In the case of external chloride ions, the bound chloride content of FAC is lower than that of OPC. The chemical chloride binding capacity of FAC is comparable to that of OPC and the lower physical adsorption capacity for chloride in FAC leads to a weaker chloride binding capacity compared to that of OPC.

Synthesis of a novel graphene oxide/belite cement composite and its effects on flexural strength and interfacial transition zone of ordinary portland cement mortars

In order to address the size mismatch between nanoscale graphene oxide and micron-scale ordinary portland cement (OPC), a novel graphene oxide/belite cement (GO/BC) composite hydrated for different periods was synthesized and applied to OPC-based mortar specimens. The morphology, surface area and pore size distributions of hydrated GO/BC composites were characterized. Thermogravimetric analyses and X-ray photoelectron spectroscopy (XPS) test were carried out to investigate the relative amount of different phase assemblages in the composite and possible chemical interactions between graphene oxide and belite cement, respectively. Moreover, the effects of GO/BC composite addition on the flexural strength, the porosity and thickness of ITZ in the OPC-based mortars were examined. Experimental results showed that the GO/BC composite after 14 and 21 days of curing exhibited some flower-like hydration products with ‘petals’ sizing around several microns and a large surface area. The hydrated GO/BC composite after 14 and 28 days, for 14-day in particular, is more effective in elevating the flexural strength and densifying the ITZ region of OPC-based binders, compared to the graphene oxide or belite cement alone. Thus, hydrated GO/BC composites could be served as a better nucleation seed for promoting the hydration of OPC due probably to their greater surface area, suitable sizes and chemical interactions between graphene oxide and belite cement.

Feasibility of using iron-rich phosphoaluminate cement to prepare anti-corrosive coatings for rebars

The anti-corrosive coating has been taken as an effective measure to keep rebars from corrosion. In this study, the iron-rich phosphoaluminate cement (IR-PAC) based anti-corrosive coating for rebar was prepared. The Cl- diffusion coefficient, strength against abrasion, and impact ductility of IR-PAC mortar were tested, with ordinary Portland cement (OPC) and sulphoaluminate cement (SAC) mortar as controls. The experimental results demonstrated that the chloride ion diffusion coefficient of IR-PAC was the lowest at any age. Compared with OPC and SAC, the strength against abrasion of IR-PAC at 90 d increased by 19.19 % and 14.32 %, respectively. The impact ductility of IR-PAC at 28 d increased by 28.21 % and 17.37 %, respectively. IR-PAC had good resistance to Cl- penetration, excellent strength against abrasion and impact ductility, which assisted the coating in blocking Cl- intrusion and resisting damage. The optimum SCMs based coating for rebar is as follows: 10.08 % Fly ash (FA), 0.1 % nano-silica (NS), and 0.65 % superplasticizer (SP). The coatings prepared with this formulation were used for electrochemical experiments. The rebars coated with IR- PAC had good corrosion resistance, which proved it is feasible to use IR-PAC to prepare anti-corrosive coatings for rebars.

Effects of curing regime, cement type, and water-to-cement ratio on the physicochemical, mechanical, and hydraulic properties of pervious mortar

This study investigated the influence of curing regime, type of cement, and water-to-cement ratio (W/C) on the physicochemical, mechanical, and hydraulic properties of pervious mortar. The carbonation degree of mortar produced using ordinary Portland cement (OPC) and belite-rich cement (BRC) increases with an increase in the W/C ratio. Mortar produced using calcium sulfoaluminate (CSA) cement was completely carbonated within the first three days. A greater degree of carbonation was observed for BRC mortar compared to that of OPC mortar at 28 days. The hydraulic properties of pervious mortar were dominated by the curing regime. Specimens subjected to carbonation curing displayed more open voids and higher permeability. Further, both OPC and BRC mortars displayed higher compressive and flexural strength levels when subjected to carbonation curing. However, mortar produced using CSA displayed significantly lower compressive strength than those of OPC and BRC.

Effect of microcapsules on the self-repairing ability of limestone calcined clay cement (LC3) mortar at different temperatures

The fundamental principle of sustainable civil engineering revolves around minimizing energy and resource consumption throughout the entire life cycle of a structure, including raw material production, construction, and maintenance. To achieve this, efficient utilization of raw materials is crucial. LC3, a novel low carbon cementitious material, offers sustainability advantages. In this paper, LC3 mortar was prepared by incorporating limestone, calcined clay and gypsum as supplementary cementitious materials, thereby replacing 50% of ordinary Portland cement (OPC). Additionally, microcapsules, comprising 4% of the total mass of cementitious materials, were introduced. This reduction in OPC content not only decreases energy consumption and CO2 emissions during cement preparation but also capitalizes on the self-repairing ability of microcapsules to mend microcracks that occur within the cement-based material during its service life. Consequently, the durability of cement-based materials is enhanced. To evaluate the effects of self-repairing on mechanical properties, permeability, and maximum amplitude at different temperatures, a comparison was made between OPC mortars and LC3 mortars. Furthermore, the self-repairing ability of surface cracks in microencapsulated mortar was assessed. The findings demonstrate that the mechanical and permeability properties of LC3 mortar (designated as CA2) exhibit no significant deviation from those of OPC mortar (designated as CA0). Moreover, under the same conditions, LC3 mortar containing microcapsules (designated as CA3) displays superior self-repairing ability compared to OPC mortar containing microcapsules (designated as CA1). Additionally, the self-repairing characteristics of microcapsules in LC3 mortar improve with increasing temperature. The self-repair process involving epoxy resin (repairing agent) and 2-ethyl-4-methylimidazole (curing agent) follows a quasi-second-order reaction kinetic model. Surface cracks with an initial width exceeding 0.4 mm in CA3 were entirely repaired within a 72-hour period.

Evaluation of Long-Term Properties of Products Containing Alkali-Activated Slag Exposed to Alkali-Silica Reaction by Mechanical Parameters

An examination was undertaken on the alkali-silica reaction (ASR) in alkali-activated slag (AAS) mixtures in comparison with ordinary portland cement (OPC) mortars and concretes. The ASR expansion in AAS mortars and concretes with different alkali contents (5%, 6%, 7%, and 8%) was examined. Changes in mechanical properties (compressive strength, tensile strength, and flexural strength) resulting from ASR expansion were evaluated. A correlation was sought between the changes in the mechanical properties of mixtures caused by ASR and ASR expansion. The test results revealed that the ASR expansion of all AAS mixtures was less than that of OPC mixtures. The expansion of AAS mixtures was below the threshold value established by the standard specifications. Additionally, it was possible to use mechanical properties to assess the occurrence of ASR due to the significant drop in these parameters caused by ASR.