Ordinary Portland Cement Cement Research Articles

Study on the hydration characteristics, mechanical properties, and microstructure of thermally activated low-carbon recycled cement

Based on the thermal activation method, utilizing fine particles of waste concrete to prepare low-carbon recycled cement (RC) is currently one of the research hotspots. Based on existing literature research results, this paper identifies four calcination temperature conditions (120, 450, 750, 1000 ℃) and uses replacement rates of 10 %, 30 %, 50 %, 70 %, and 100 % of RC to replace ordinary Portland cement (OPC).The main physical properties, hydration characteristics, mechanical properties, and microstructure of RC are studied. The study elucidated the influence of RC thermal activation temperature, replacement rate, fineness, and age on its hydration characteristics, mechanical properties, and microstructure, establishing a macro-micro correlation for RC and revealing the mechanism of improvement in mechanical properties of thermal-activated RC. The research indicates that in the initial stage of hydration, RC exhibits a relatively fast hydration rate, with higher initial total heat release than OPC. Hydration products include internal hydration products (formation of C-(A)-S-H gel) and external hydration products (formation of plate-shaped AFm). Furthermore, RC exhibits a faster hydration rate at a hot activation temperature of 750°C, with CH and C-S-H gel transforming into the highly hydrated α´L-C2S, forming a denser microstructure at an early stage. Moreover, at a replacement rate of 30 %, the compressive strength of cement mortar reaches its optimum at 28 days, achieving 13.81 MPa, equivalent to 60.7 % of OPC cement mortar, with a 66.67 % reduction in carbon emissions. Microstructure analysis reveals that when the temperature reaches 1000°C, excessive combustion of RC leads to the formation of low-reactivity C2AS and β-C2S, resulting in a decrease in macroscopic mechanical properties. Additionally, increasing the fineness of RC significantly enhances its rehydration capability, especially as the age increases. This study is of great significance for the preparation of green cement-based composite cementitious materials.

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.

Strength Performance of Concrete Containing Rice Husk Ash as Cement Replacement in Presence of Polypropylene Fiber

This study focuses on the utilization of Rice Husk Ash (RHA) as partial replacement of Ordinary Portland Cement (OPC) in concrete in addition with Polypropylene (PP) fiber. The main goal of this study was to decrease dependence on OPC and address environmental waste generated through rice mills. This study considered concrete cubes prepared through 1:2:4 ration with 0.50 water-cement ratio with and without RHA and PP fibers. The water curing was done for 7 and 28 days, with three specimens for each proportion, and the average value was considered as the result. It was observed that the compressive strength of M2 concrete which containing 10% RHA was noticed 7% higher than the control mix concrete and declared as 10% RHA as optimum dosage. Next, the performance in terms of compressive strength of concrete containing optimum dosage of RHA in presence of PP fibers of three different lengths were also evaluated and found that the 0.1% of PP fiber of 0.5 inches length gives the 25% higher strength performance as compared to the control mix and 17% higher than the concrete containing 10% RHA only at the age of 28days. Hence, this study concluded that the replacing OPC cement with 10% RHA produces satisfactory strength performance and incorporation of PP fiber gives better strength performances.

Comparative study of the use of Ordinary Portland Cement (OPC), Portland Composite Cement (PCC) and Hydraulic Cement (HC) types in high quality concrete with an independent compaction system

One of the problems faced in the manufacture of high-strength concrete is the difficult workability, and the rising price of OPC and PCC cement. To overcome these problems, a self-compacting system is needed in concrete to make the workability easier to work with and the use of other types of cement besides OPC and PCC, such as the latest product HC, to reduce the cost of making high-strength concrete. The objective of this study was to compare the use of OPC, PCC and HC cement types in high strength concrete with self-compacting system, so as to overcome the high-quality problem more effectively. The manufacture and testing of test specimens were carried out at the PT Pionir Beton Industri Laboratory with the results of testing the compressive strength of OPC type cement at 955.93 kg/cm2, the compressive strength of PCC cement concrete at 866.22 kg/cm2, and the compressive strength of HC cement concrete at 885.83 kg/cm2. It can be concluded that the use of OPC cement in concrete mixes will produce the strongest concrete among the other two types of cement.

Durability of clayey soil stabilized with calcium sulfoaluminate cement and polypropylene fiber under extreme environment

Calcium Sulfo-Aluminate Cement (CSAC) is gaining interest among researchers, consultants, engineers, and environmentalists as a prospective replacement of Ordinary Portland Cement (OPC) across many construction industries. The main reason is that the production of CSAC generates a lower carbon footprint as compared to OPC cement production. Other benefits of CSAC include quick bonding & strength development, and less shrinkage. Many studies are available and ongoing on the advantages and limitations of CSAC in concrete. However, only a few studies are available on its application in soil stabilization. Therefore, the efficiency of CSAC for soil stabilization is a topic of discussion in geotechnical engineering. In this research, a locally sourced highly compressible clayey soil was stabilized with different combinations of CSAC and polypropylene fiber (e.g., 5.0%, 7.5% & 10.0% of CSAC and 0.5% & 1.0% polypropylene fiber), and its effectiveness was observed and evaluated in terms of durability (Wetting-Drying and Freezing-Thawing tests) against extreme environments and also checked Unconfined Compressive Strength (UCS) as per American Society of Testing and Materials (ASTM) guidelines. The findings of this research are evaluated in terms of percentage of soil loss, change in moisture content and volume, and loss of strength after durability exposure. Moisture content and bulk unit weight were determined after each stage in the Freezing-Thawing durability cycles. Samples prepared with 10.0% of CSAC and 1.0% of fiber were able to survive all durability cycles of Wetting-Drying with PCA (Portland Cement Association) soil-loss percentage criteria. On the other hand, samples prepared with 10.0% cement with 0.5% as well as 1.0% fiber were able to survive all durability cycles of Freezing-Thawing with PCA soil-loss percentage criteria. These survived samples showed a significant amount of unconfined compressive strength even after being subjected to these durability cycles.

Strength and Microstructure Assessment of Partially Replaced Ordinary Portland Cement and Calcium Sulfoaluminate Cement with Pozzolans and Spent Coffee Grounds.

Supplementary cementitious materials are considered a viable and affordable way to reduce CO2 emissions from the cement industry's perspective since they can partially or nearly entirely replace ordinary Portland cement (OPC). This study compared the impact of adding spent coffee grounds (SCGs), fly ash (FA), and volcanic ash (VA) to two types of cement: OPC and calcium sulfoaluminate cement (CSA). Cement samples were characterized using compressive strength measurements (up to 210 days of curing), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), attenuated total reflection infrared spectroscopy, and hydration temperature measurements. In all the studied systems, the presence of SCGs reduced compressive strength and delayed the hydration process. CSA composite cement containing 3.5% SCGs, 30% FA, and 30% VA showed compressive strength values of 20.4 MPa and 20.3 MPa, respectively, meeting the minimum requirement for non-structural applications. Additionally, the results indicate a formation of cementitious gel, calcium silicate hydrate (C-S-H) in the OPC-based composite cements, and calcium alumino-silicate hydrate (C-A-S-H) as well as ettringite in the CSA-based composite cements.

Physical and Mechanical Behavior of New Ternary and Hybrid Eco-Cements Made from Construction and Demolition Waste.

Construction and demolition waste (CDW) currently constitutes a waste stream with growing potential use as a secondary raw material in the manufacture of eco-cements that offer smaller carbon footprints and less clinker content than conventional cements. This study analyzes the physical and mechanical properties of two different cement types, ordinary Portland cement (OPC) and calcium sulfoaluminate (CSA) cement, and the synergy between them. These cements are manufactured with different types of CDW (fine fractions of concrete, glass and gypsum) and are intended for new technological applications in the construction sector. This paper addresses the chemical, physical, and mineralogical characterization of the starting materials, as well as the physical (water demand, setting time, soundness, water absorption by capillary action, heat of hydration, and microporosity) and mechanical behavior of the 11 cements selected, including the two reference cements (OPC and commercial CSA). From the analyses obtained, it should be noted that the addition of CDW to the cement matrix does not modify the amount of water by capillarity with respect to OPC cement, except for Labo CSA cement which increases by 15.7%, the calorimetric behavior of the mortars is different depending on the type of ternary and hybrid cement, and the mechanical resistance of the analysed mortars decreases. The results obtained show the favorable behavior of the ternary and hybrid cements made with this CDW. Despite the variations observed in the different types of cement, they all comply with the current standards applicable to commercial cements and open up a new opportunity to improve sustainability in the construction sector.

A Comparative Study of Energy Consumption, Global Warming Potential and Impact Categories of Four Different Blends of Concrete Using Cradle to Gate Life Cycle Assessment

The present study is a comparison of four different concrete mixes using ‘cradle to gate’ life cycle assessment. The aim is to obtain environmental impact, focusing mainly on criteria pollutants (CO, lead (Pb), PM10, NOx, SO2, and volatile organic compounds), global warming potential, energy consumption, and impact categories like human health, ecosystem quality, and resources. Each concrete mix design has different binder combination. CONOPC contains ordinary Portland cement (OPC) as a binder. CONPPC has 27% Fly ash + 73% OPC while CON PSC has 47% ground granulated blast furnace slag (GGBS) + 53% OPC as a binder. CONGP has 100% fly ash as a binder without the use of cement. The comparative results show that all three concrete mixes, i.e., CONPPC, CONPSC, and CONGP, performed better than CONOPC in terms of harmful gas emissions, energy use, and GWP. Further, with respect to three impact categories, CONOPC has the highest score with 11.06 pt and CONGP has the lowest score with 1.68 pt. CONPPC shows a reduction by almost 30% with a value of 7.77 pt whilst CONPSC shows an even further reduction by 46% with a value of 5.95 pt compared to CONOPC. It is recommended that OPC cement should be replaced by either Portland slag cement (PSC) or Portland pozzolana cement (PPC) in concrete production. Geopolymer concrete is also a good substitute for traditional concrete. Recommendations from this work would assist concrete producers to choose the best available options without compromising the performance of concrete while reducing the negative environmental impact during production.

Study and Review of Properties and Applications of Portland Pozzolana Cement

Portland Pozzolana Cement (PPC) is prepared by adding Pozzolanic materials to ordinary Portland Cement. The artificial pozzolana materials used in the manufacturing of PPC such as fly ash, silica fume, rice husk, blast furnace slag, are actually industrial waste, which is produced in large amounts. These artificial pozzolana materials when used in concrete can reduce consumption of natural resources, diminish the effect of pollutants in the environment and it is economical and reliable. The main objective of this paper is to focus on the properties and applications of Portland Pozzolana Cement and make effective use of different industrial by-products in the manufacturing of cement. We found that both PPC and ordinary portland cement (OPC) are commonly used types of cement in construction. Nowadays, PPC is used as a substitute for ordinary Portland cement (OPC cement). Since PPC contains pozzolanic materials, it helps to enhance the strength of concrete. The quantity of PPC required in making the concrete is less when compared to OPC. PPC is a green material that contributes towards sustainable development.

The Effects of Nanosized-Palm Oil Fuel Ash on Early Age Hydration of Hardened Cement Paste: The Microstructure Studies

Integration of cement-based products with nanosized-palm oil fuel ash as supplementary cementing material (SCM) amend its hydration’s degree at early age phase and the microstructural groundworks are relevant to explain the findings. Hence, the present work investigates the microstructure properties of the hardened cement paste (HCP) incorporating nPOFA to study on the effect of nPOFA in cement hydration at an early age phase. An Ordinary Portland Cement (OPC) paste as a set of HCP blended with microsized-palm oil fuel ash (mPOFA) (10-30%) and nPOFA (10-60%) were prepared and cured for 28 days. The microstructural examination of OPC, mPOFA and nPOFA cement pastes at 28 days curing age via Thermogravimetric (TG) analysis, X-Ray diffraction (XRD) analysis, morphology study and Fourier transform infrared (FTIR) spectroscopy analysis. In TG analysis, the relative weight loss of calcium hydroxide (CH) of nPOFA pastes is lower than OPC and mPOFA. Based on the CH peaks at 2?= 18.1°and 34.0° in the diffractogram, it shows that nPOFA pastes give the low CH peaks compare to OPC and mPOFA pastes. In addition, the nPOFA pastes form the dense and compact microstructure of HCP compare to other pastes. Observations from FTIR analysis, nPOFA pastes display a high frequency of Si-O band due to the high rate of pozzolanic reaction. Overall, the findings confirmed the contribution of nPOFA in accelerating the rate of cement hydration and pozzolanic reaction as it reduced the amount of CH in the cementitious matrix.

Investigations on effect of different fibers on the properties of engineered cementitious composites

Engineered Cementitious Composite (ECC) or Strain Hardening Cement-based Composites (SHCC) or bendable concrete, is a special type of concrete which is reinforced with specially selected short random fibers. Strain capacity of ECC is in the range of 3–7%, compared to 0.01% for ordinary Portland cement (OPC) paste, mortar or concrete. Bendable concrete acts like a ductile metal when compared to brittle nature of OPC cement. Various studies show that ECC has superior properties compared to PCC mixes. Due to adverse effect on fiber dispersion and overall performance, the coarse aggregates are not used in ECC. Different type of fibers is added to impart the tensile strength in ECC. Some of fibers include Poly Vinyl Alcohol, Polypropylene fiber and also natural fibers. ECC shows ductility property in the hardened state and flexible property in fresh state makes ECC applicable to wide range of construction application Victor C. Li (2003) [15]. Even though the initial cost of ECC is more than normal concrete, long term benefits of former is better than latter which helps to potentially drive this technology. A review of ECC is done in this paper regarding its mechanical and chemical properties. Also the compressive strength and flexural strength of ECC with PVA and PP fibers are determined to find the effect of different fibers in ECC. An increase in flexural strength is observed with the usage of PVA and PP fibers.

Determination of sulfate content in OPC and CSA cement by sodium carbonate extraction method

The penetration of sulfate ions into the concrete often causes durability problems such as spalling, cracking, and strength loss. Traditional methods for sulfates content test in cement-based materials, a large number of toxic and high-risk chemical reagents such as hydrochloric acid, barium chloride, barium chromate are used. In this research, the sodium carbonate extraction (SCE) method was used to determine the sulfates content in Ordinary Portland cement (OPC) and Calcium sulphoaluminate (CSA) cement while the gravimetric method was used as standard method to evaluate the accuracy of SCE method. The optimum SCE method operation conditions were determined as 0.30 mol/L sodium carbonate solution, liquid–solid ratio at 100:1 and particle size smaller than 500 μm. The results indicated that the replacement of gravimetric method with SCE method for sulfates content test is acceptable in CSA cement but improper for Portland cement system. Through the FTIR, XRD, and TG-DSC analysis, it was found that the absorption of sulfate ions by C-S-H gels was responsible for the failure of SCE method in Portland cement system.

Investigating the properties of jet grouting columns with fine-grained cement and silica fume

In Jet Grouting (JG) applications, manufacturing of jet grouted columns which answer the purpose, is possible by designing proper injection fluid which is a cement grout in most cases. In this study, the impacts of three different binder types on the performance of JG columns was investigated. Fine-grained cement (DMFC-800), Ordinary Portland Cement (OPC) and the mixture of OPC cement including 10% silica fume (SF) by weight were used as binders. Grouting mixtures were prepared at various water/cement (W/C) ratios, then JG columns were manufactured. Whilst the maximum unconfined compressive strength (UCS) value was obtained from fine grained cement induced samples (max. UCS = 24.6 MPa for W/C = 1.0), very high strength values were detected for OPC + 10%SF induced samples as well. The maximum splitting tensile strength (STS) values for OPC + 10% SF induced samples were found to be (min. STS = 3.62 MPa for W/C = 1.25). Furthermore, after the permeability tests, it was observed that the columns with DMFC-800 and OPC + 10% SF induced mixtures exhibit the lowest permeability coefficients as compared to columns made from the other binders (min. k = 0.1124 × 10−8 m/s for DMFC-800). Scanning electron microscope (SEM) image analysis revealed that DMFC-800 cement and OPC + 10% SF induced mixture reduced the voids between particles and enhanced the binding ability of the grouting mixture.

A comparative study on the thermal behaviour of PPC and OPC cement

Spectroscopy is the interaction between matter and electromagnetic radiation, which is useful in the determination and characterisation of various chemical composition existing in the material. Present paper, focuses on predicting the extent of thermal damage on hydrated Portland Cements ( PC ), using Fourier Transform Infrared Spectroscopy ( FTIR ). The hydrated specimens of Portland Pozzolana Cement ( PPC ) and Ordinary Portland Cement ( OPC ), were subjected to temperatures ranging from 27 °C − 800 °C, for an interval of every 100 °C was analysed. Variation in the absorbance peaks obtained from FTIR , is correlated with the Thermal analysis (TA). At temperatures beyond 400 °C, reduction in the absorbance values at wavenumbers of 3430 – 3440 cm −1 of Ettringite phase for PPC and OPC specimens was observed. However, in OPC specimens, an increase in the absorbance values of Portlandite phase at wavenumbers ranging from 3640 to 3645 cm −1 was observed. The phase changes taking place in the PC specimens observed using FTIR , are in good agreement with the mass loss and heat flow plots obtained from TA. Therefore, it can be concluded that FTIR analysis is suitable test method in predicting the thermal damage of concrete specimen.

Evaluation of time to shrinkage-induced crack initiation in OPC and slag cement matrices incorporating circulating fluidized bed combustion bottom ash

The effect of bottom ash produced from circulating fluidized bed combustion (CFBC) on the shrinkage-induced cracking potential of ordinary Portland cement (OPC) and slag cement mixtures were investigated by evaluating the time to crack initiation, predicted by comparing tensile strength obtained from direct tensile tests with shrinkage-induced stress obtained from shrinkage strain and elastic modulus results. Although replacing OPC and slag cement amounts with CFBC bottom ash delayed cracking times due to its shrinkage compensation, the effect varied with the drying condition. Therefore, for effective application of CFBC ash in cement mixtures, boundary conditions affecting drying rates need careful consideration.

Characteristics of geopolymer hybrid concrete in peat water

Geopolymer hybrid is a combination of geopolymer and Ordinary Portland Cement (OPC) or other binders to produce an alternative binder. This type of binder could be used to transform low-quality fly ash into multi-purpose concrete. Ordinary Portland Cement (OPC) concrete subjected to an acidic organic environment such as peatland, is more prone to deterioration in long-term than concrete using the supplementary cementitious material. In this research, the geopolymer was made by activating low-quality fly ash (contains more than 5% carbon) with the alkaline activator. The inclusion of OPC and Portland Cement Composite (PCC) as a fly ash replacement material is intended to promote curing at ambient temperature and immobilization of heavy metals in fly ash. The specimens were cast and cured at ambient temperature up to 28 days. OPC was used as a control mix. Subsequently, the concrete was immersed in fresh peat water in the laboratory up to 28 days. Characteristics of the geopolymer hybrid such as compressive strength, porosity, and leaching were determined. Microstructure analysis, such as SEM-EDX and FTIR, were conducted. Results show that the geopolymer hybrid has a good strength development at early days. At 28 days, there was a reduction of strength and increase of porosity, probably due to the attack of calcium from the OPC concrete. There was a transformation of aluminosilicate gel into C/N-A-S-H that is advantageous for the strength development at the early days. However, a weaker material has formed in the long term that cannot resist further acid attack. It can be concluded that the geopolymer hybrid is a promising binder, but it is essential to design the material appropriately to have better strength, durability and environmental properties in the long term.

Effect of SCMs on the freeze-thaw performance of iron-rich phosphoaluminate cement

Due to the low durability of ordinary Portland cement (OPC), the deterioration of OPC-based materials is very severe in marine structures exposed to cold weather. In contrast, iron-rich phosphoaluminate cement (iron-rich PAC) has good durability and is promising for applications in marine construction. In this context, in the present study, the freeze-thaw (F-T) performance of iron-rich PAC mortar was evaluated and compared with those of OPC and sulphoaluminate cement (SAC) mortars. In addition, the influences of supplementary cementitious materials (SCMs), such as fly ash (FA), limestone powder (LP) and gypsum (GP), on the F-T behaviour of the blended iron-rich PAC mortar were carefully investigated by testing the compressive and flexural strengths, analysing the pore structure using mercury intrusion porosimeter (MIP), and examining the microstructure using XRD and SEM-EDS analysis. The experimental results elucidated that the F-T performance of the iron-rich PAC mortar was far better than those of the OPC mortar and the SAC mortar. In the SCM blended iron-rich PAC systems, the most favourable modification results were obtained with replacement by LP at the optimum dosage of 3–9% (wt%). In this replacement range, the F-T resistances of the LP blended iron-rich PAC systems were better than that of the reference PAC (without SCMs). Further, the F-T performances of the FA and LP blended iron-rich PAC systems were superior to those of the OPC and SAC systems.

Effective Utilization of Quarry Residues and Mineral Admixtures in High Strength Concrete

The various requesting utilization of cement is not promptly met with Ordinary Portland cement (OPC) alone. To satisfy up the need and just as guaranteed the green concrete durability, it has ends up important to add mineral increments with the best blend of others by-product as substitution to improve the performance without risking the quality of the concrete. In the construction industry, OPC cement and stream sand are utilized as significant material making it rare and restricted. While, with respect to the cement is notable as the greatest guilty parties for discharging carbon dioxide (CO2). Consequently, incomplete substitution of cement turns into a need just as common sand in concrete by waste material or by-product without bargaining the nature of the finished result. Fractional supplanting with Ground Granulated Blast furnace Slag (GGBS), Silica Fume (SF) fuses with 100% of quarry dust (QD) as sand substitution has been utilized. The utilization of 100% QD with OPC+SF delivered increasingly durable concrete with low chloride ingress and preferred outfitting over with 100% stream sand. Notwithstanding the cost impact advantage, the decrease in exhaustion of stream sand, tending to condition and manageability issues, it is a significant commitment in making green concrete.

Steel rebar corrosion in artificial reef concrete with sulphoaluminate cement, sea water and marine sand

To reduce the surface alkalinity of artificial reef concrete (ARC) and save fresh water and natural aggregate resources, a new artificial reef concrete (NARC) made with sulphoaluminate cement (SAC), sea water and marine sand was proposed in our previous work. However, the steel corrosion as a major concern associated with NARC has not been explored. In this paper, the effects of cement type (SAC, ordinary Portland cement (OPC), mixed cement of OPC and SAC) on the chloride permeability and capillary water absorption of sea water and marine sand-based ARCs were studied. The anodic polarization and loss of steel rebar weight were used to evaluate the effects of the cement type and corrosion inhibitor on the corrosion of steel rebars in ARCs. The results of the present work show that for sea water and marine sand-based ARC, SAC significantly improves the microstructure and decreases the chloride penetration and the water absorption rate. Meanwhile, due to the high chloride binding rate of SAC, the corrosion degree of rebars in NARC is less than that of sea water and marine sand-based ARC with OPC and mix cement of OPC and SAC. Compared with ordinary ARC (ARC made OPC, fresh water and river sand), the steel rebar corrosion in NARC is more serious. Nevertheless, a 2% dosage of corrosion inhibitor (TEA) can significantly decrease the steel rebar corrosion in NARC to a similar corrosion degree of ordinary ARC. The feasibility of using marine sand and seawater in SAC-based ARC is verified.

Self-Cleaning of Photocatalytic Mortar with Glass Aggregate and Calcium Sulfoaluminate-Belite Cement

The self-cleaning performance and mechanism of photocatalytic mortars with different cementitious materials and aggregates was evaluated through a rhodamine B (RhB) degradation test. The self-cleaning property of photocatalytic concrete helps to preserve its aesthetics, NOx removal potential, and surface reflectance. In this study, the addition of TiO2 to calcium sulfoaluminate-belite cement (CSAB) demonstrated a self-cleaning potential like ordinary Portland cement (OPC). Photocatalytic mortar mixes with OPC demonstrated increased self-cleaning efficiency with glass fine aggregate and with higher TiO2 content. However, glass addition was not effective in improving the self-cleaning efficiency of CSAB mortar with TiO2. Replacement of OPC with class F fly ash significantly decreased self-cleaning efficiency. The decrease in pore solution pH with fly ash replacement of OPC or CSAB cement instead of OPC was hypothesized as the cause for the decline in self-cleaning efficiency. An experiment to study the photocatalytic degradation rate of RhB revealed that it increased with higher pH. RhB photocatalytically degrades through N-de-ethylation and cleavage of the chromophore structure depending on the reaction surface characteristics with the first path investigated in this paper. It was shown that some of the RhB on the photocatalytic mortar surface was degraded by the N-de-ethylation path regardless of the cement and aggregate constituents and increasing TiO2 (anatase) content increased RhB degradation through N-de-ethylation.