Portland Cement Mortars Research Articles

Investigation of cementitious composites reinforced with metallic nanomaterials, boric acid, and lime for infrastructure enhancement

<abstract> <p>Nanomaterials integration within construction materials could promote the generation of more sophisticated structural materials, as it imbues reinforcement at the nanoscale. This research adopted experimental approaches to assess the influence of metallic nanomaterials on the performance of cementitious composites with various ratios of boric acid (1%, 3%, and 5% by sand's weight) and lime (0.5%, 1.5%, and 2.5% by sand's weight), respectively, for use in construction infrastructure facilities. This research provides valuable insight into the potential of using boric acid and lime as well as metallic nanomaterials to strengthen cement-based composites. Initial curing stages revealed a notable decrease in compressive strength attributed to the inhibitory effects of boric acid and lime on cement hydration. However, the introduction of TiO<sub>2</sub> nanoparticles demonstrated significant enhancements in compressive strength and durability. Statistical analysis emphasized the significance of nanomaterials in augmenting compressive strength, with implications for long-term performance. This study has shown that the addition of nano-titanium dioxide TiO<sub>2</sub> can significantly enhance the compressive strength of Portland cement mortars, particularly when used in conjunction with appropriate ratios of boric acid and lime. The results of the 7 days test indicated that the inclusion of boric acid and lime in the cement mortars significantly decreased the compressive strength. However, the addition of nano-TiO<sub>2</sub> to cement mortars containing 1% boric acid and 0.5% lime resulted in a 31-fold increase in compressive strength compared to cementitious composites without nano-TiO<sub>2</sub>. In contrast, the compressive strength significantly increased by 1.2 times, 85.3 times, and 65.1 times, respectively, after 56 days for the addition of boric acid (1%, 3%, and 5%) with lime (0.5%, 1.5%, and 2.5%), respectively, in the presence of nano-TiO<sub>2</sub>, compared to the 7 days strength. The results also illustrated that, in general, the incorporation of various types of nano-TiO<sub>2</sub> into cementitious composites containing boric acid and lime increases their compressive strength as the ratios of boric acid and lime increase, as long as sufficient curing time is allowed.</p> </abstract>

Enhancing Mechanical Properties and Antimicrobial Activity of Portland Cement through Titanium Oxide Incorporation

The impact of various factors such as microbes, allergens, inadequate environmental conditions, pollutants, and suboptimal building materials on human health within indoor environments is of utmost importance due to the significant amount of time people spend inside buildings. The objective of this study was to assess the combination of Portland cement (PC) with Titanium Oxide (TiO2) nano powder for antimicrobial properties with good physical and mechanical strength. TiO2 was added to PC at various percentages (0.5%, 1.0% and 1.5% by the weight of cement) and analysis of slump flow, compressive strength and flexural strength were determined. The antimicrobial activity was evaluated by agar diffusion test, utilizing 4 bacteria strains: Escherichia coli, Staphylococcus aureus, Enterococcus faecalis and Pseudomonas aeruginosa. Results showed that the addition of TiO2 increased the mechanical strength of the specimen with 1.0% TiO2 displaying the optimum result. For the antimicrobial activity, samples with 1.05% TiO2 had the highest efficiency in inhibiting bacteria growth. The findings showed that a lower percentage of TiO2 added to the PC mortar significantly enhances its mechanical properties and is efficient in inhibiting the growth of bacteria. Such mortar mixture with antibacterial properties should be utilized to enhance hygiene conditions in diverse environments, including hospitals, institutional kitchens, etc., where such properties are necessary.

Mechanical Properties and Lifecycle Assessment of a Green Alkali-Activated Mortar Based on Biomass Wood Ash

Abstract Portland cement (PC) is the most commonly used binder material for producing concrete. Nonetheless, increasing concerns have been attached to its manufacture which is highly energy-intensive and generates a large quantity of greenhouse gases. Developing alkali-activated materials as eco-binders is a sustainable replacement for PC and many investigations have been reported successfully utilizing industrial wastes as precursors. However, owing to the low reactivity, studies regarding biomass wood ashes (BWA) are still limited. To produce a green cementless alkali-activated mortar material, in this study, biomass fuel by-products – biomass wood bottom ash and biomass wood fly ash – were binarily used as precursors. Sodium hydroxide NaOH at 10 mol/L and calcium hydroxide Ca(OH)2 at 20 % by binder mass were applied as alkali activators. Recycled sand, substituting natural sand, was adopted as fine aggregate with an aggregate/binder ratio of 2 to reduce the consumption of non-renewable natural resources. Compressive and flexural strength were tested to evaluate the mechanical performance. A cradle-to-gate lifecycle assessment was conducted to analyse the environmental impacts. The results reveal that the alkali-activated mortar has less environmental impact compared to the traditional PC mortar. NaOH solution is the primary source of environmental influence and BWA only contributes to very limited impacts. The usage of Ca(OH)2 effectively improves the mechanical strength and compared to NaOH, it leads to decreased energy demand, requires fewer preparation steps and is less dangerous for operation.

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.

Evaluation of the Thermomechanical Response of Geopolymeric Mortars Manufactured from Peruvian Mining Residues and its Comparison with Portland Cement Mortars

Geopolymeric mortars made from a mixture of waste from the Peruvian informal mining industry, sodium hydroxide activating solution, and fine sand were studied, comparing them physically and mechanically with conventional Portland cement mortars. Both conventional and geopolymeric mortars were prepared in parallel and then subjected to uniaxial compression tests at various temperatures (ambient, 200 °C and 500 °C). The mechanical results found revealed maximum average resistance values of 63, 84 and 79 MPa for conventional mortars, and 12, 32 and 36 MPa for geopolymeric mortars, when they were tested at room temperature, 200 °C and 500 °C, respectively. The best mechanical results in geopolymeric mortars were found when considering a binder: fine sand ratio of 1:2, molarity of the hardening solution of 12 M and a hardening solution: binder ratio of 0.6. It was possible to demonstrate a good agreement between the distribution of particle sizes observed microstructurally and those found by granulometry studies by laser light diffraction.

Investigation of the Diffusion of Chloride Ions in Blended Cement Pastes

AbstractWhen exposed to aggressive environments containing chlorides, the chlorine ion partially binds to the usual Portland cement mortar and changes its mineralogy. Chlorine ions entering the system displace sulfate from the monosulfoaluminate. Such systems form Kusel's salt at low chloride concentrations and Friedel's salt at higher concentrations. Unbound chloride ions remain dangerous for reinforcing steel, which diffuse deep into the concrete and destroy the passivating layer on the reinforcement. To assess the protective properties of concrete in relation to metal reinforcement, it is proposed to investigate the process of displacement of the diffusion front in cement composites of various compositions. It is also important to study changes in such characteristics as porosity and filtration properties, which significantly affect the penetration depth of an aggressive medium. The study of the structure, mineral and chemical composition is carried out in layers.

The influence of polymer powder on the ion transportation and antierosion mechanism of cement mortar: From experiments to molecular dynamics simulation

As the main product of hydration reaction of common Portland cement, calcium silicate hydrate (C-S-H) gel is a porous gel system containing capillary and gel pores. These channels act as transport channels for water molecules and ions in the cement system. The diffusion of water molecules and ions through C-S-H gel channels has significant effects on the strength, shrinkage, creep, chemical and physical reactions of the cement system. Polymer can modify cement-based materials and improve their ionic permeability resistance. In this study, emulsified asphalt powder (EAP) and vinyl acetate ethylene copolymer (VAE) redispersible polymer powder was added into the Portland cement mortar as admixtures, respectively. The influence of redispersible polymer powder on the transportation and erosion mechanism of ions in cement mortar was investigated by analyzing the pore structure, compressive strength ratio, chloride ion permeability depth and micromorphological of cement mortar. The adsorption and diffusion behaviors of ions with different concentrations and water molecules were explored by molecular dynamics simulation, and the physiochemical reactions between ions and hydration products during the transport process in cement-based materials were comprehended.

Exploring the Detection of Cl- Penetration in Portland Cement Mortars via Surface Electrical Resistivity.

Surface electrical resistivity is a non-destructive technique that is sensitive to the microstructure of hydrated cement paste and the chemical composition of the pore solution in cement-based materials. In this study, a Wenner array was used to measure changes in mortar resistivity due to chloride ion diffusion as a function of electrode separation. Specimens were made from four mortar mixtures: 100% Ordinary Portland cement and 60% cement + 40% fly ash at two water/binder ratios of 0.55 and 0.40. The specimens were subjected to unidirectional chloride ion diffusion in a 2.8 M NaCl solution for 175 days. To determine the chloride penetration depth, three methods were used: silver nitrate spraying, chloride concentration profiles via potentiometric titration, and chloride concentration profiles via inversion of the resistivity data using the RES1D software (version 1.00.09 Beta). The results showed a linear relationship between the chloride ion penetration depth obtained via inversion of the surface electrical resistivity data versus the penetration depth from colorimetry and from chloride concentration profiling (both with R2 = 0.8612). Chloride penetration changed the conductivity of the pore solution; therefore, the resistivity decreased when increasing both the chloride concentration and the penetration depth. Inversion of surface resistivity data obtained with a Wenner array permitted non-destructive determination of chloride penetration. However, these results were obtained under laboratory environmental conditions and other scenarios must be addressed for wider applications.

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.

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.

Doping engineering for controlled hydration and mechanical properties in Portland cement mortar with ultra-low ZnO concentration

The incorporation of ZnO into cementitious matrices elicits notable alterations in the hydration process, consequently influencing the setting time. Nonetheless, comprehensive investigations exploring the impact of ZnO particle morphology on cement hydration remain limited. In this study, we present a comprehensive exploration of how the morphology of ZnO dopants can be harnessed to modulate the hydration process, concomitantly resulting in significant improvements in mechanical properties. Specifically, we have identified that ZnO nanoparticles (ZnO-Nps) exhibit a unique capacity to delay cement hydration by instigating the formation of a continuous zinc hydroxide coating. This coating remarkably inhibits the progression of cement hydration. Notably, this delay in the hydration process amounts to an approximately 76% compared to the reference material. However, a distinctive transformation occurs with ZnO microparticles (ZnO-Mps) exhibiting a flower-like morphology. In this case, the continuous coating becomes discontinuous, leading to a marked enhancement in mechanical properties. These enhancements manifest as an increase ranging between 13 and 10% in comparison to the reference material. Our results underscore the pivotal role of ZnO particle morphology in tailoring the hydration process and concurrently elevating mechanical properties. This study contributes to elucidating the intricate interplay between morphology, hydration kinetics, and mechanical behavior within cementitious systems. The ability to harness these morphology-dependent effects offers a promising avenue for optimizing material properties and advancing our understanding of cementitious systems.

Effect of multi-walled carbon nanotube/Porous Carbon/SiO2 on reinforcing of cement mortar matrix: Modeling studies of effective parameters

The enhancement of the mechanical properties of cement composites by various nanomaterials is now a trendy subject. This study assessed the impact of three nanomaterials on the compressive and tensile strength of Portland cement mortar: biomass-derived porous carbon, MWCNT, and SiO2. These nanoparticles were developed using environmentally friendly, inexpensive technologies, and they underwent material characterization analyses using FESEM, N2 adsorption-desorption, contact angle, FTIR, XRD, and TEM. After 7 and 28 days, the compressive and tensile strength was assessed. According to the findings, among the samples, cement-SiO2 had the maximum compressive strength (19.32 MPa). The FESEM micrographs amply support the creation of the C-H-S gel and the presence of the bridge. The outcomes further showed that the nanoparticle's presence in the matrix does not significantly impact the tensile strength. SiO2-cement had the highest tensile strength, 1.45 MPa, matching the conclusions drawn from the compressive strength. Moreover, the compressive strength of cement was unaffected by the total pore volume of nanomaterials or the pore-filling mechanism of cement. Modeling (Linear regression-least square method) made it possible to predict the compressive strength for a period of 92 days and examine the influence of effective ingredients on it. Ultimately, the results indicate that porous carbon and silica can be viable alternatives for MWCNT.

Durability Performance of One-Part Geopolymer Versus Two-Part Geopolymer and Portland Cement Mortar

Durability Performance of One-Part Geopolymer Versus Two-Part Geopolymer and Portland Cement Mortar

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.

Effects of incorporating silica glass powder as a supplementary cementitious material on selected properties of portland cement mortar

The use of waste glass powder as a partial replacement for cement is an emerging practice for sustainable cement-based construction. Several studies have demonstrated that finely ground-powdered glass could be an interesting supplementary cementitious material (SCM). However, the performance of such material is influenced by the chemical composition of glass and its pozzolanic reactivity. In this context, the goal of this study is to investigate the use of silica-glass powder (SGP), which is characterized by a high content of silica (>96%), as a partial replacement of Portland cement in mortar. In this research work, mortars containing 7.5%, 10, 12.5, 15 and 20% SGP in replacement of an amount of cement, with three different water-to-binder ratios of 0.55, 0.60 and 0.65 are studied. Selected properties have been investigated at both fresh and hardened stages, which include workability, air content, flexural and compressive strengths estimated by destructive and non-destructive methods, water absorption by capillarity, permeability to chlorides and chloride ions diffusion. The experimental results confirm that incorporating SGP improves the mechanical strength of the mortar, notably in the long-term, and can considerably enhance its durability properties, especially by a decrease in sorptivity of the mortar and by an increase of its resistance to chloride ions diffusion. Correlations between selected physical and mechanical properties and certain durability indices are also established and discussed in this study.

Is the diffuse ultrasound method reliable for evaluating autonomous self-healing in cementitious materials with expansive agent pellets?

This study applied the diffuse ultrasonic method as a technique to assess the autonomous self-healing of Portland cement mortars with the incorporation of pellets with different sizes (0.6–1.18 mm, 1.18–2.34 mm, and 2.34–4.75 mm) composed of expansive agents, namely as calcium aluminate cement (CAC) and flue gas desulfurization gypsum (FGD). Surface cracks of 200–300 µm were induced in mortar specimens through a three-point bending test. The self-healing of cracks after 28 days was evaluated from the observed variations on three diffuse ultrasonic parameters: diffusivity, the arrival time of the maximum energy (ATME), and dissipation rate. The results indicated that the incorporation of pellets produced self-healing properties, which could be identified by the observed increased diffusivity (almost comparable to the reference non-cracked mortar), corroborating with the strength regain results. Therefore, the diffuse ultrasonic technique (especially the diffusivity parameter) is a promising alternative for evaluating the self-healing of cementitious materials by incorporating pellets with expansive agents.

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.

High-ferrite Portland cement with glass–ceramic aggregates: Mechanical properties, durability, and interfacial transition zone

This study aimed to improve the durability of concrete in the marine environment through the utilization of waste glass-ceramics as aggregates. The investigation focused on their effects on the mechanical strength, chloride attack resistance, and abrasion resistance of high-ferrite Portland cement mortar (HFCM). Inductively coupled plasma, X-ray diffraction, scanning electron microscopy-backscattered electronic, and microhardness techniques analyzed the impacts of glass-ceramics on the interfacial transition zone’s (ITZ) composition, structure, and strength. Results demonstrated that glass–ceramic fine aggregates possessed low alkali activity, posing no potential risk of alkali silicate reaction. The partial substitution of natural sand with glass-ceramics improved HFCM’s mechanical strength and resistance to chloride attack and abrasion. The dissolution of trace amounts of Si4+ and Al3+ from the glass-ceramics contributed to the hydration reaction and facilitated the development of a compact and robust ITZ. Overall, HFCM with glass-ceramics effectively resisted the harsh marine environment, specifically against chloride ion erosion and wave erosion.

Beyond time: Enhancing corrosion resistance of geopolymer concrete and BFRP bars in seawater

To improve the durability of Basalt fiber reinforced polymer (BFRP) bars reinforced geopolymer concrete (GPC), it is important to study the time-dependent variation of the corrosion resistance ability of GPC and BFRP in a seawater environment. This paper presents an experimental investigation to study the time-dependent mechanical properties and durability of BFRP bars and geopolymer materials synthesized by granulated blast furnace slag (GGBFS), fly ash, and silica fume. The resulting GPC and Portland cement (PC) concrete were exposed to artificial seawater. The mechanical properties of GPC were evaluated by analyzing and comparing the volume expansion and strength loss rates of GPC and PC concrete in an artificial seawater environment. The corrosion resistance of geopolymer (GP) mortar and PC mortar was evaluated by studying the migration ability and pore structure in corrosive ions attack (Cl−, SO42−, Mg2+) in artificial seawater. Moreover, the time-dependent tensile strength of BFRP was comparatively investigated by immersing in different solutions (tap water, artificial seawater, and alkaline simulated seawater). In addition, the dual interface transition zones (ITZs) characteristics of BFRP reinforced GPC under artificial seawater were also investigated by SEM and BSE tests. The results showed that the volume expansion rate and strength loss rate of GPC decreased by 77.6% and 8.7%, respectively, after 360 days of seawater corrosion compared with PC concrete. This enabled the development of a time-dependent strength model of GPC in marine environments. The coefficient of ions diffusion in GP mortar is much lower than that of PC mortar, and GP mortar shows excellent resistance to ion migration. In addition, the effect of seawater corrosion on the tensile strength of BFRP bars increases with the increase of bars' diameter, and the ultimate strengths of BFRP bars with diameters of 6 mm and 8 mm were 695 MPa and 663 MPa, respectively. The tensile strength degradation model of BFRP bars in geopolymer concrete under seawater corrosion was established. After 360 days of seawater immersion, the average porosity of the ITZ between geopolymer and aggregates, and the average porosity of the ITZ between geopolymer and BFRP bars increased insignificantly compared to that of PC concrete. This research can provide a theoretical basis for the service life prediction of BFRP reinforced geopolymer concrete within marine environments.

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.