Photocatalytic Mortars Research Articles

Photocatalytic NOx degradation and [formula omitted] adsorption by mortar modified with S-g-C3N4/MgAl-CLDH: Influence factors and stability

NOx is a harmful gas that causes respiratory diseases and acid rain. Commonly used photocatalysts for degrading NOx such as UV responsive TiO2 show weak photocatalytic degradation efficiency under visible light. Furthermore, the great concern is that the degradation product, nitrates (NO3-), from NOx could be washed away and increase the nitrogen deposition and eutrophication in the surrounding soil and aquatic environments, resulting in serious secondary pollution. To address these issues, this study proposes a novel solution by incorporating S-g-C3N4/MgAl-CLDH nanocomposites into a cementitious system which features high NOx degradation efficiency under visible light condition and the efficient capture and adsorption of NO3- in situ. The NOx degradation was comprehensively studied, encompassing the influencing factors and stability. The mechanism for NO3- adsorption process was expounded using the isothermal model. The results show that the amount of exposed S-g-C3N4/MgAl-CLDH and the contact area between S-g-C3N4/MgAl-CLDH and NOx are the essential reasons affecting the NOx degradation. The NOx degradation ability of photocatalytic mortar exhibits excellent stability with the NOx removal ratio decreasing by only 4.8 % and 14.5 % after ten consecutive tests and 120 min of ultrasonic washing, respectively. Furthermore, S-g-C3N4/MgAl-CLDH increases the NO3- adsorption capacity of photocatalytic mortar by about 1.5 times, and the adsorption process of NO3- follows the Freundlich isotherm. The study offers an alternate method for designing innovative nanocomposites in cement-based materials to control environmental pollution.

NOx degradation by cement mortar containing B-TiO2/MgAl-CLDH under visible light: Experimental and modeling

In this paper, an advanced photocatalyst, B-TiO2/MgAl-CLDH, was synthesized and applied in cement mortar. The photocatalytic NOx degradation ability of cement mortar containing B-TiO2/MgAl-CLDH under different initial NOx concentrations and flow rates was investigated. The results show that B-TiO2/MgAl-CLDH has stronger visible light absorption, lower recombination rate of electron-hole pairs and narrower optical band gap than commercial nano-TiO2 (P25), resulting in enhanced NOx removal efficiency. Specifically, the maximum NOx degradation ratio of B-TiO2/MgAl-CLDH is 23.4% within 30 min, which is about 5 times that of P25. For photocatalytic mortar, the initial NOx concentration (from 1.0 ppm to 2.0 ppm) and flow rate (from 1 L/min to 3 L/min) were positively correlated with NOx removal amount, while negatively correlated with NOx removal ratio. Based on the internal molecular diffusion properties of NOx, Langmuir-Hinshelwood and the power law kinetic models were used to predict the NOx degradation ability of photocatalytic mortar. The modeling of NOx degradation process presents a reliable prediction of the NOx removal ability of photocatalytic mortar, serving as a valuable tool for assessing the mortar’s NOx removal effectiveness for policymakers and engineers.

A comprehensive evaluation of the photo-catalytic performance of recycled glass aggregate incorporated permeable cement-based mortar with TiO2 as a photo-catalyst

This study aims to investigate the effectiveness of incorporating recycled glass aggregate (RGA) in TiO2-containing cement-based permeable mortars in terms of their photo-catalytic performance. To do this, standard and permeable mortars were produced with the RGA utilization rates of 15% and 30% (by weight of total aggregate content). Photo-catalytic activity of the mortars was evaluated through the determination of NOx and NO degradation capacities, NO2 transformation ratio and the selectivity, and their photo-catalytic activity performances were compared with each other and with reference specimens without any RGA to assess the efficiency of RGA utilization in terms of photo-catalytic degradation. Microstructural and mechanical properties of the mortars were also evaluated by performing scanning electron microscope (SEM) analysis and compressive strength test, respectively. According to the experimental results, regardless of curing age, utilization of RGA as aggregate caused decrements in the strength results because of the lower adherence capability with matrix. NOx degradation results indicated that permeable structure of the photo-catalytic mortars allows NOx species to diffuse to the inner part of the hardened specimen in favor of stimulation of photo-catalytic degradation reactions in deep along with the surface. RGA utilization was also allowed to penetration of UV lights throughout the matrix providing improved the photo-catalytic activity for the TiO2-containing specimens. The correlation between the selectivity results and the degradation rates of NOx demonstrates the reliability of selectivity as a parameter for evaluating the photo-catalytic performance.

Study on the Behavior of Self-Cleaning Impregnated Photocatalyst (Tio2) with Cement Mortar

Cement-based materials are increasingly and widely employed in infrastructure development; however, they pollute our environment by generating carbon dioxide, which is detrimental to our civilization. In self-cleaning concrete, photocatalysts accelerate the decomposition of organic particles; thus, photocatalytic degradation of gaseous pollutants could reduce pollution. The incorporation of photocatalytic components enhanced the mechanical self-cleaning properties of cement mortar. In this study, 4–6 percent by weight of rutile TiO2 was added to mortar, and the results were compared to those of a control sample. On the proposed mortar cubes, both fresh mortar and hardening mortar experiments were conducted. Because the initial and final setting times of TiO2 differ from those of conventional cement mortar, the surplus TiO2water-cement ratio had to be modified. The adaptability of the sol-gel method enables the use of various process parameters to influence the properties of the produced TiO2 nanoparticles. The compressive strength was calculated for 7, 14, 21, and 28 days, and an ultrasonic velocity test was performed after 28 days. On mortar samples, acid and sulfate attack experiments were performed. The M-3 mortar mixture containing 5% rutile exhibited the highest level of strength compared to the other mixtures. The M-3 exhibits a strength that is 10.96% greater than that of the control mix. The impact of acid and sulfate attack on the strength of mix M-2 is relatively modest in comparison to other mixtures. Using RhB (rhodamine color) discoloration under UV light, such as sunlight, the photocatalytic mortar is concentrated; a typical test for self-cleaning cementitious materials reveals the presence of more photocatalytic material, which yields the best results.

NOx degradation ability of S-g-C3N4/MgAl-CLDH nanocomposite and its potential application in cement-based materials.

In this study a new photocatalytic nanocomposite, S-g-C3N4/MgAl-CLDH, was synthesized and implemented into cement mortar by internal mixing or coating. The photocatalytic NOx degradation efficiency of the S-g-C3N4/MgAl-CLDH and photocatalytic mortar was investigated. The NOx degradation efficiency and photoluminescence spectra of S-g-C3N4/MgAl-CLDH after being immersed in the simulated concrete pore solution were evaluated to assess its chemical stability. The results show that compared with S-g-C3N4, the S-g-C3N4/MgAl-CLDH exhibits a narrower bandgap (2.45 eV), a lower photogenerated electron-hole pair recombination rate and a higher specific surface area (36.86 m2 g-1). After 21 min of visible light irradiation, the NOx degradation rate of S-g-C3N4/MgAl-CLDH achieves 100% as compared to merely 81.5% of S-g-C3N4. After being submerged in simulated concrete pore solution, the S-g-C3N4/MgAl-CLDH exhibits only a slight decrease of 5% in degradation rate after 12 min of irradiation, confirming a good compatibility and stability in cement-based materials. The NOx degradation ability of the internally mixed mortar is enhanced with an increase in the dosage of S-g-C3N4/MgAl-CLDH. For coated mortar, in contrast, a decline in NOx degradation rate is observed after 5 layers of coating owing to the lower porosity of mortar after excessive coating.

Effects of process variables for NO conversion by double-layered photocatalytic mortar with TiO2 nanoparticles

In this study, we prepared the double-layered photocatalytic mortar, where the top-layer has the minimum thickness of 2 mm. We investigated systematically the effects of various process variables (initial NOX concentration, TiO2 addition amount, UV-A radiation, gas flow rate and relative humidity) on photocatalytic conversion of NOX and also the transient NOX conversions for changing ambient conditions of process variables with time. The higher the nano-TiO2 concentration in the mortar or UV-A radiation intensity is, or the lower the NOX gas flow rate or relative humidity is, the higher the NOX conversion efficiency is. As the initial concentration of NOX increases, NOX conversion efficiency decreases, but the amount of NOX conversion increases. It is confirmed that the prepared photocatalytic mortar could convert NOX in the air efficiently for various conditions of process variables. NOX conversion efficiencies in transient environmental conditions were equivalent to those in fixed conditions for the same process variables. This study provides strong basic data to apply the photocatalytic mortar to convert NOX efficiently using solar energy without the use of extra energy and can be easily extended to future applications to infrastructures such as buildings, tunnels, or roads.

Experimental Investigation and Modeling of the Sulfur Dioxide Abatement of Photocatalytic Mortar Containing Construction Wastes Pre-Treated by Nano TiO2

A photocatalytic mortar containing recycled clay brick powder (RCBP), recycled fine aggregate (RFA), recycled glass (RG), and nanoscale titanium dioxide (NT) was fabricated to degrade low-concentration sulfur dioxide. Instead of intermixing or dip-coating, NT was firstly loaded onto the surface of carriers (RFA and RG) using a soaking method to prepare composite photocatalysts (CPs) denoted as NT@RFA and NT@RG. The prepared CPs can both take full advantage of the intrinsic characteristics of construction wastes, namely, the high porosity and alkalinity of RFA and the light-transmitting property of RG, and can significantly reduce the cost of using NT. RG in high dosage potentially triggers alkali–silica reaction (ASR) in cement-based materials, which affects the durability of the prepared mortar. RCBP, another typical construction waste sourced from crushed clay bricks, was proven to be a pozzolan similar to grade II fly ash. The combined use of RCBP and RG in photocatalytic mortar is expected to simultaneously improve durable performance and further raise the upper content limit of construction wastes. Results exhibit that 70% cement plus 30% RCBP as cementitious material can sufficiently control ASR to an acceptable level. The filling effect and the pozzolanic reaction caused by RCBP result in a decline in porosity and lessened alkalinity, which decreases sulfur dioxide removal. The paper uses both response surface methodology (RSM) and an artificial neural network (ANN) to model photocatalytic efficiency with various initial concentrations and flow rates and finds the ANN to have a better fitting and prediction performance.

Effect of physical properties of construction wastes based composite photocatalysts on the sulfur dioxide degradation: Experimental investigation and mechanism analysis

The reducing, reusing, and recycling of construction and demolition wastes (C&DWs) is an imperative aspect of sustainable development. Recycled aggregates (RAs) originated from C&DWs therefrom are applied to the field of building materials for preparing new constructions. The study herein aims to by the photocatalytic technology endow RAs with the photocatalysis and by that achieves the upcycling of RAs with high-added value. Three typical types of RAs were used, which are respectively recycled clay brick sands (RCBS), recycled glass sands (RGS), and recycled fine concrete aggregates (RFA). The sulfur dioxide was identified as the target pollutant; whilst the degradation of sulfur dioxide was the specific embodiment of the photocatalytic performance. RAs were used as carriers to load and absorb nanoscale titanium dioxide (NT), preparing composite photocatalysts (CPs). The CPs were subsequently used as fine aggregates in substituting natural fine aggregates, resulting in the photocatalytic mortar. The particle size of RCBS, the color of RGS, and the origin of RFA were identified as emblematic characteristics that affected the photocatalytic performance of produced photocatalytic mortar. Results unveiled that: (1) RCBS with a smaller particle size absorbs more NT and possesses a higher sulfur dioxide degradation; whilst the utility of per gram NT of 2.36–4.75 mm RCBS is c.a. 2 times than that of 0.6–1.18 mm RCBS. (2) RGS that is black has the lowest sulfur dioxide degradation; whilst the RGS that is transparent has the highest value. RGS with other colors at varying extents exhibited a reduced degradation, with no discernible rules to follow. (3) RFA derived from recycled concrete with normal strength has a better performance. The paper at the end also in an attempt probed into the enhancement mechanisms of photocatalytic efficiency triggered by RA-based CPs.

Effect of construction wastes on the rheo-physical behavior of photocatalytic mortar

Herein, the rheological and mechanical performance generated by the incorporation of construction wastes on the photocatalytic mortar were investigated. Construction wastes referred to recycled clay brick sands (RCBS) and recycled clay brick powder (RCBP). First, the RCBP was used as supplementary cementitious material to replace cement by weight percentages of 0, 10, 20, and 30 at fixed water to cement ratio of 0.6. Then, an optimal combination (20% RCBP and 80% cement) considering the yield stress, plastic viscosity, and mechanical performance was used to bind three types of fine aggregates, viz. 100% silica sands, 80% silica sands plus 20% RCBS, and 80% silica sands plus 20% RCBS based composite photocatalysts (RCBS/TiO2). The recycled glass cullet (RGC) and the RGC based composite photocatalyst (RGC/TiO2) were also used as the fine aggregate. Results revealed that the yield stress and the plastic viscosity of RCBS/TiO2 were higher than silica sands and pure RCBSs. Besides, compared with pure RCBS/TiO2, the combination of RCBS/TiO2 and RGC/TiO2 reduced both the yield stress and the plastic viscosity of the mortar. In addition, either RCBS or RCBS/TiO2 with a blending ratio no higher than 20% caused a little effect on the mechanical performance of the mortar.

Investigational work on self-cleaning cement mortar with titanium dioxide in partial replacement of cement

Environmental degradation is the world's most pressing issue nowadays. Photocatalytic mortar, often referred to as self-cleaning cement mortar, is a recent trend in concrete technology. Titanium dioxide (TiO2) is added to cement mortar mixtures as part of the technology. This speeds up the natural oxidation process and pollutant breakdown. Titanium dioxide, a naturally occurring photocatalyst, may degrade gaseous contaminants when exposed to sunshine. The hygiene of the exterior surfaces can be preserved, and air pollution in the surrounding neighbourhood can be decreased. For self-cleaning qualities, titanium dioxide is utilized in the mortar as a partial replacement for cement at 5%, 10%, and 15% by weight of cement in this experimental investigation. The results of a concrete compression strength test and a Rhodamin Dye Decolorization test were compared to those of a typical cement mortar.

PHOTOCATALYTIC MORTAR WITH TIO2 FOR THE REDUCTION OF AIR POLLUTANTS PRODUCED BY VEHICULAR EMISSIONS

Photocatalytic mortar with TiO2 leads to a reduction in air pollution due to vehicle emissions. For this purpose, the experimental method was used, which consisted of the preparation of mortars with the same proportion of 1: 4, a strength of 145 kg / cm2 and with different percentages of titanium dioxide (0% and 10%), which were evaluated under the same conditions through the following tests: Quantity of polluting gases, compressive strength and photocatalytic capacity. The results obtained—reduction of carbon dioxide by 97.9%, hydrogen sulfide by 72.9%, sulfur dioxide by 67.2%, nitrogen monoxide by 63.4%, carbon monoxide by 40.5% and oxygen recovery by 7.7%—confirmed the performance of the photocatalytic process through titanium dioxide (TiO2) in terms of an improvement in air quality, and the reduction of colorants, rhodamine by 89.10% and methylene blue 53.06% confirmed its self-cleaning capacity, thus improving the reduction of air pollution.

Photocatalytic Recycled Mortars: Circular Economy as a Solution for Decontamination

The circular economy is an economic model of production and consumption that involves reusing, repairing, refurbishing, and recycling materials after their service life. The use of waste as secondary raw materials is one of the actions to establish this model. Construction and demolition waste (CDW) constitute one of the most important waste streams in Europe due to its high production rate per capita. Aggregates from these recycling operations are usually used in products with low mechanical requirements in the construction sector. In addition, the incorporation of photocatalytic materials in construction has emerged as a promising technology to develop products with special properties such as air decontamination. This research aims to study the decontaminating behavior of mortars manufactured with the maximum amount of mixed recycled sand without affecting their mechanical properties or durability. For this, two families of mortars were produced, one consisting of traditional Portland cement and the other of photocatalytic cement, each with four replacement rates of natural sand by mixed recycled sand from CDW. Mechanical and durability properties, as well as decontaminating capacity, were evaluated for these mortars. The results show adequate mechanical behavior, despite the incorporation of mixed recycled sand, and improved decontaminating capacity by means of NOx reduction capacity.

A Study on the Reduced Rebound Method of Surface Finishing Spray Photocatalytic Mortar

A Study on the Reduced Rebound Method of Surface Finishing Spray Photocatalytic Mortar

Impact of incorporating recycled glass on the photocatalytic capacity of paving concrete blocks

This paper presents the results of the development of translucent photocatalytic mortar produced with incorporation of recycled glass, applied on the superficial layer of concrete blocks intended for urban paving. The main aim of developing the translucent mortar was to enhance the photocatalytic capacity in double-cap concrete blocks. The incorporation of glass in the mortar was performed by replacing the mineral aggregate at percentages ranging from 20 to 61%. The recycled glass used in the research was submitted to decontamination process, being then crushed and sieved into the desired fractions. The effects on the simple compression strength due to the incorporation of recycled glass were evaluated, as well as the translucency of the photocatalytic layer. Based on the strength and translucency results obtained, the highest percentage of glass incorporation to the mortar was defined. As final criterion for the validation of this optimized percentage, the alkali-silica reactivity test (ASR) was performed. Lastly a laboratorial comparison was performed to evaluate the NOx degradation efficiency of blocks with and without recycled glass incorporation to the mortar surface under different environmental conditions. The results show that the incorporation of glass in an optimized percentage is feasible for mortar production, since satisfactory compression strength and translucency were obtained, without alkali-silica reactivity, providing increase in photocatalytic efficiency.

Exposure Assessment During the Industrial Formulation and Application of Photocatalytic Mortars Based on Safer n-TiO2 Additives

Titanium dioxide nanoparticles (n-TiO2) are added to photocatalytic mortars to improve urban air quality. Their activity can be increased by dispersing and binding them on natural sepiolite surface. Workers handling photocatalytic additives can be exposed to n-TiO2. However, the release of nanoparticles to the workplace can be different if the material used is raw n-TiO2 powders or if the nanoparticles are supported on sepiolite. In this work, we compare occupational exposure to n-TiO2 for raw n-TiO2 and a hybrid additive n-TiO2/sepiolite obtained by a proprietary process. Measurements were performed in two industrial sites that process 1 ton batches of mortars, formulated with the same quantity of n-TiO2, followed by their application outdoors. Direct reading instruments were used to monitor particle number concentration and size distribution. Simultaneously, filter-based samples were collected for mass concentration and microscopy analysis. Two tasks produced a significant release of particles, the addition of fillers during the mortar formulation, in site 1, and the mixing of mortar with water for its application in the second site. For the first task, particle concentration was significantly lower when the n-TiO2/sepiolite was added compared to the raw n-TiO2. For the second task, once the mortar is fully formulated, this metric does not identify differences among the batches. Titanium mass concentration was 3–10 times lower when handling the mortar formulated with the hybrid additive. These results suggest that supporting the n-TiO2 on the sepiolite network not only increases the photocatalytic activity, but is also a safer design that reduces exposure to nanoparticles.

Rheological behaviour, mechanical performance, and NOx removal of photocatalytic mortar with combined clay brick sands-based and recycled glass-based nano-TiO2 composite photocatalysts

Herein, we prepared composite photocatalysts (CP) by loading nano-TiO2 (NT) on recycled clay brick sands (RCBS) and recycled glass (RG). CPs are denoted as NT@RCBS and NT@RG, respectively. The NT@RG was used to partially replace NT@RCBS and the combined CPs were then used to replace common river sand (RS) in photocatalytic mortar. Micrographs coupled EDS exhibit both NT@RCBS and NT@RG successfully carry NT on their surfaces; whilst the amount of carrying is measured by analytical balance as 0.0048 g per gram of RCBS and 0.0013 g per gram of RG. Once some NT@RCBS is replaced by NT@RG, the rheological behaviour is improved due to the smooth surface of the latter. However, compressive strength is not evidently lifted by NT@RG because the weak bonding between NT@RG and surrounding cementitious materials even though NT@RG relative to NT@RCBS has a higher hardness. However, the NT@RG by 25% weight replacement over NT@RCBS contributes to an enhanced NOx removal since a mutual promotion effect that NT@RCBS receives enough refracted light to activate photocatalysts in deep pores while NT@RG obtains enough room to accommodate final products caused by photocatalysis and enhances the anti-abrasion capacity. Finally, the combined use of NT@RCBS and NT@RG increases NOx removal by ~18.8%; and at the same saves NT usage by ~80% relative to the traditional NT (5% NT by wt. of cement) intermixing approach. Thereby, this study provides a cost saving approach to by construction wastes prepare environmentally friendly photocatalytic mortar with higher photocatalytic efficiency.

Sulfur Dioxide Degradation by Composite Photocatalysts Prepared by Recycled Fine Aggregates and Nanoscale Titanium Dioxide.

To alleviate the heavy burden on landfilling, construction and demolition wastes (C&DWs) are recycled and reused as aggregates in cementitious materials. However, the inherent characteristics of recycled fine aggregates (RFA), such as the high crushing index and high-water absorption, magnify the reusing difficulty. Nevertheless, attributing to the high porosity and high level of calcium hydroxides existing in the old mortar, RFA is featured with a high specific surface area and a high alkalinity. These features are useful to augment the total photo-degradation of SO2 by nano-TiO2 (NT) intermixed mortar, leading RFA to be an excellent potential carrier to load nano-TiO2 and prepare the composite photocatalyst. Hence, this study proposed to load NT onto the surface of RFAs and river sands (RSs) (the control) by the soaking method, preparing composite photocatalysts denoted as NT@RFA and NT@RS, respectively. The prepared composite photocatalysts were then utilized as sands in photocatalytic mortar to evaluate for SO2 degradation. Experiments identified a 50% higher amount of NT was loaded onto the surface of FRA relative to the control. This higher loading amount plus higher alkalinity ultimately translated into a higher photocatalytic activity. In addition, the mortar containing NT@RFA exhibited 46.3% higher physiochemical absorption and 23.9% higher photocatalytic activity than that containing NT@RS. In addition, the durability, embodied by the reuse and anti-abrasive properties, of NT@RFA exceeded that of NT@RS. The overall findings reveal that the NT@RFA not only garners beneficial effect from the high porosity but also generates positive effect from the high alkalinity. Though a number of studies deal with building materials with NT, this study is the first to load NT onto RFA and prepare composite photocatalysts which were then used as fine aggregates in building materials. Consequently, this study proves the potential high-added-value reusability of RFA in green construction materials and provides a low-cost, high-efficiency approach to degrade atmospheric SO2.

NOx degradation by photocatalytic mortars: The underlying role of the CH and C-S-H carbonation

This study aims to understand the impact of carbonation mechanism of C-S-H and CH in photocatalytic mortars on NOx removal efficiency. Changes in surface chemistry and microstructure induced by the carbonation of portlandite and C-S-H (AFm/AFt) were correlated with the photocatalytic efficiency of the mortars doped with three types of titania-based photocatalysts. Furthermore, the influence of cementitious matrix on the photocatalytic selectivity was evaluated by studying the capacity of hydration/carbonation products to adsorb NO2. The study revealed that in terms of both photocatalytic efficiency and selectivity, mortars with microsilica addition exhibit superior properties over the pure cement-based mortars upon carbonation. Carbonation of C-S-H (AFm/AFt) gel results in the formation of capillary pores between10–50 nm, which outbalances the shielding effects of carbonates formed, leading to the enhanced photocatalytic properties. Moreover, C-S-H gel maintains its high NO2 adsorption capacity even after carbonation, resulting in the high selectivity of the photocatalysis.

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.

Influence of Nano-silica on the Leaching Attack upon Photocatalytic Cement Mortars

Photocatalytic cementitious materials are used in the exterior of the buildings and infrastructure for self-cleaning and air-purifying purposes. These materials are exposed to the aggressive exposure conditions like acid rain, runoff water and are subjected to the deterioration due to the leaching of calcium. The knowledge of leaching attack upon photocatalytic cementitious materials after the addition of nano-materials is necessary. In the current study, the influence of nano-silica addition on the leaching attack upon photocatalytic cement mortars was thoroughly investigated. For this purpose, photocatalytic mortars were made by adding 3% TiO2 and variable amount (0–2%) of nano-silica. Accelerated leaching environment was created by immersing mortars in 6 M ammonium nitrate (NH4NO3) solution. The progressive development of the leaching depth in mortars was measured. The loss of hardened properties was monitored by evaluating the compressive strength, flexural strength, porosity, and dynamic modulus of elasticity. X-ray diffraction, thermogravimetry, Fourier transform infrared spectroscopy, scanning electron microscopy tests were conducted to know the microstructural deteriorations. Results indicated that the leaching attack induced mechanical and microstructural damages in the mortars, but the addition of nano-silica decreased mechanical and microstructural damages in the photocatalytic mortars and increased the resistance of photocatalytic mortars to leaching attack.