Replacement Level Research Articles

Strength and microstructural development in concrete pavements by blended copper tailings powder and copper tailings sand

This study investigated the effects of replacing cement with copper tailings powder on pavement concrete performance. Concrete pavements were prepared by substituting 5 %, 10 %, and 15 % of the cement with copper tailings powder. Additionally, 70 % of the river sand (0.6–0.15 mm) was replaced with copper tailings sand of a fixed particle size. The study aimed to understand how this combined replacement affected the mechanical and microstructural properties of the concrete. Tests revealed that two hours of mechanical milling was optimal for activating the copper tailings powder, resulting in a Pozzolanic activity index of 82 %. Concrete specimens with 5 % copper tailings powder achieved the highest flexural strength (6.21 MPa) and compressive strength (52.8 MPa). Furthermore, this replacement level resulted in the lowest porosity and highest resistivity. Scanning electron microscope images revealed that increasing the amount of tailing powder reduced the degree of hydration within the microstructures. However, the specimens with both tailings powder and sand exhibited better compactness and homogeneity in their internal pore structures compared to those with only tailings sand. It suggests a beneficial microfilling effect from the tailings powder.

Enhancing mortar performance: A comparative study on particle size of recycled concrete powder and metakaolin in binary and ternary blends

The construction industry generates substantial volumes of construction and demolition waste (CDW), including aggregates and fine particles classified as recycled concrete powder (RCP). This study investigates the sustainable reuse of RCP by evaluating its combined use with metakaolin (MK) as supplementary cementitious materials in both binary and ternary mixtures with Portland cement, aiming to reduce environmental impact without compromising mortar performance. The experimental program assessed two particle sizes of RCP, along with MK, and various replacement levels, which were pivotal parameters in the study. A series of binary and ternary mixtures were prepared with different proportions of RCP and MK, considering replacement levels ranging from 10 % to a maximum of 30 %, using RCP alone or in conjunction with MK. The mortars were analyzed in both fresh and hardened states, focusing on critical properties such as consistency index, compressive strength, splitting tensile strength, elastic modulus, water absorption, density, void index, and capillary water absorption. Furthermore, a microstructural analysis was conducted using scanning electron microscopy (SEM), and a cement consumption efficiency index, along with CO₂ emissions data, was calculated to provide a comprehensive evaluation of performance and sustainability. The findings demonstrate that RCP with a particle size comparable to that of cement (RCP1) significantly enhances both physical and mechanical performance, particularly in ternary mixtures with MK due to its pozzolanic activity, where the silica (SiO₂) and alumina (Al₂O₃) components react to form additional hydrated products, thereby improving the properties of mortars. For instance, the ternary mixture comprising 15 % RCP1 and 15 % MK attained compressive and splitting tensile strength of 29.26 MPa and 3.36 MPa at 28 days, respectively, compared to the reference mixture, which yielded 27.96 MPa and 3.33 MPa. Conversely, larger particle sizes (RCP2) and higher replacement levels led to a decline in performance across all evaluated parameters. Ternary mixtures containing RCP1 also exhibited a higher cement consumption efficiency index and lower CO₂ emissions per MPa. Notably, the mixture with 15 % RCP1 and 15 % MK showed the most favorable indicators overall, with cement consumption and CO₂ emissions measured at 12.08 kg/m³·MPa and 10.01 kgCO₂/m³·MPa, respectively. These results suggest that the synergy between RCP1 and MK enhances particle packing and matrix density, which in turn improves the structural properties of the mortar. The incorporation of MK compensates for the limited reactivity of RCP, especially at higher replacement levels, while the utilization of RCP1 offers significant sustainability benefits by reducing Portland cement consumption. This study demonstrates that the combination of RCP and MK in ternary mixtures presents a technically viable and sustainable alternative for mortar production, optimizing cement use and reducing CO₂ emissions. The innovative application of CDW-derived RCP in construction materials represents a practical approach to promoting more sustainable practices within the industry.

Assessment of waste eggshell powder as a limestone alternative in portland cement

The decarbonization of the concrete industry is an ongoing pursuit. One solution towards this goal is the use of limestone powder in portland cement. Waste eggshell has tremendous potential as an alternative calcite filler in cement due to its similarities with limestone. In this research, the feasibility of adding 15% and 35% ground eggshell in portland cement to make cement mortars was investigated. The hydration mechanism of eggshell and limestone blended cements was compared through the heat of hydration, phase assemblage, electrical resistivity, compressive strength, and shrinkage measurements. The experimental results showed that cement mortars with ground eggshell attained similar compressive strength as that with limestone. However, eggshell mixtures demand more mixing water to compensate the hydrophobicity of the eggshell membrane. The high calcite content in both eggshell and limestone accelerates the hydration of cement at 15% replacement, but ground eggshell retards cement hydration at 35% replacement due to the dominant influence of the membrane. Overall, eggshell waste is a feasible sustainable alternative to limestone powder at up to 15% portland cement replacement levels. Lifecycle assessment and cost analysis showed that adding 15% ground eggshell in cement concrete further reduces its embodied carbon and energy and cost compared to cement concrete containing limestone powder.

Optimizing sustainable concrete mixes with recycled aggregate and Portland slag cement for reducing environmental impact

Concrete is the world’s most extensively manufactured material, with the integration of recycled materials becoming crucial for sustainable construction. This study investigates the mechanical properties of concrete mixes containing Recycled Aggregates (RA) and Portland Slag Cement (PSC) to understand their suitability for sustainable construction applications. Utilizing normal-strength concrete with a compressive strength of 35 MPa and a 0.45 water-to-cement ratio, fifteen mix designs were tested, varying RA and PSC replacement levels from 0 to 100% and 0% to 50%, respectively. Comprehensive mechanical testing, including compressive and tensile strength assessments at 7 and 28 days, alongside modulus of elasticity and stress–strain curve evaluations, was conducted. The results reveal that full replacement of Natural Aggregate (NA) with RA decreased compressive strength by 10% and modulus of elasticity by 20%. However, a partial replacement of 25% of Ordinary Portland Cement (OPC) with PSC, in the presence of RA, moderated the reduction of compressive strength to 0.92% and increased the modulus of elasticity by 3.7%. The optimum mix, consisting of 75% OPC, 25% PSC, and 50% RA, significantly enhances concrete’s mechanical properties, recommending it for reinforced concrete applications due to its potential environmental and structural benefits.

Effects of fish meal replacement with composite proteins source on growth performance, antioxidant capacity and swim bladder quality of chu’s croaker (Nibea coibor)

Collagen, as a commercial functional protein, is widely applied in food, cosmetics, biomedicine and other industries, and swim bladder is regarded as an ideal source of raw materials due to its rich collagen content. Chu’s croaker (Nibea coibor), as an economical fish that can produce high-grade swim bladder, is popularly farmed, however, its high fishmeal demand limits the development of the feed industry. Therefore, it is worth thinking about how to reduce the use of fish meal without affecting the swim bladder quality. Given that, an 8-week feeding trial was conducted to investigate the effects of fish meal partially replaced (0.0%, 5.0%, 10.0%, 15.0%, 20.0%) with composite proteins (CPs, consisted of corn protein meal and hydrolyzed feather meal) on growth, antioxidant capacity and swim bladder quality (texture and collagen deposition) of chu’s croaker. Results showed that although growth performance decrease with the increase of CPs’ replacement level, it did not compromise the swim bladder quality. Specifically, 5% - 10% CPs did not affect the growth significantly, but can improve antioxidant capacity, protein content, collagen synthesis and texture quality of swim bladder. The enhancement of swim bladder texture, including hardness, chewiness, springiness, and adhesiveness may be caused by changes in the expression of related genes, such as colga1t1, col12a1, cyp27a1, etc. These results indicated that appropriate fish meal replaced by CPs could be applied during aquaculture practice after comprehensive consideration of feed cost, growth rate and quality of swim bladder. This study provides support for the development of cost-effective feed formulations that improve the sustainability and economic viability of chu’s croaker culture.

Development of high strength light weight concrete for RC beams by using optimum replacement level of pumice aggregate

Development of high strength light weight concrete for RC beams by using optimum replacement level of pumice aggregate

Functionalizing heavy metal contained incinerated sewage sludge ash in recycled glass-based alkali-activated materials for sewer environment

This study evaluates the performance of alkali-activated cement (AAC) mortars in an artificial sewage environment. The mortars, initially prepared with waste glass powder (GP) and ground granulated blast furnace slag (GGBS) in a 50:50 mass ratio, were modified by replacing 10 wt% of GGBS with incinerated sewage sludge ash (ISSA) with the goal of offering a biocidal effect. Comparisons were made with calcium aluminate cement (CAC), metakaolin (MK), and MK combined with zinc ferrite nanoparticles, each at a similar GGBS replacement level. The results showed that only incorporating CAC improved the strength development, achieving compressive and flexural strengths of 62.7 MPa and 7.4 MPa, respectively, at 28 days, while introducing ISSA or MK reduced the compressive strength to 47 MPa and flexural strength to 4.5 MPa. Although heavy metal ions from ISSA or zinc ferrite nanoparticles minimized biofilm thickness, they could not compensate for the reduced strength and increased alkalis leaching. Among all the tested mixtures, the 50GP40GGBS10CAC mixture exhibited superior biogenic acid resistance, possibly due to its Al-rich C-N-A-S-H gel phases (Ca/Si = 0.4, Na/Al = 0.8, Si/Al = 3.4) and refined pore structure (porosity = 3.4 %), making it the most microbial acid-resistant option for sewer rehabilitation.

Durability and hardened characteristics of cement mortar incorporating waste plastic and Polypropylene exposed to MgSO4 attack

Annual waste plastic disposal has grown, harming nature. Utilising this waste in concrete production may help preserve building resources. This study tested cement mortar with polyvinyl chloride (PVC) and polypropylene (PP) substituted for sand aggregate at 0, 5, 10, 15, and 20%. The samples were nevertheless exposed to a 10% and 20% MgSO4 solution for a month. The properties of both fresh and hardened materials under these circumstances have been evaluated and contrasted with those evaluated under typical circumstances. For mixes including PP and PVC, the flow diameter increased. The rounded plastic particles provided fewer contact surfaces and less friction among mixtures, which reduced water consumption and improved workability, leading to an increase in slump flow. As the amount of plastic aggregate increases, the compressive strength decreased. Moreover, this pattern might be explained by the weakening of the bond between the surfaces of the plastic aggregate and cement paste. The hydration of cement may also be hampered by the hydrophobic properties of plastic aggregate. Like compressive strength, the splitting tensile strength decreased as the replacement level of plastic ratio increased regardless of its type under all conditions (normal and exposing to MgSO4). PP and PVC fine aggregate in mortar increases sorptivity under all situations. Following screening, those circumstances and PVC have the most impact on compressive strength. increasing PVC and PP at 10% for each of them leads to lower values of compressive and tensile strength. An optimization process was implemented to determine the optimum value of PVC, PP, and MgSO4. It shows that using PVC of 3.9%, PP of 10.1%, and MgSO4 of 19.59% leads to maximum compressive and tensile strength with the minimum cost and CO2 emissions.

Effect of Epoxy Resin on the Strength Propery of Portland Cement Concrete

In this study, the strength effect of partially substituting Portland Cement (PC) with epoxy-resin in making concrete was examined. A mix ratio of 1:1.87:2.67 (PC: sand: granite chippings) at water-cement ratio of 0.5 targeting a strength of 30N/mm2 was adopted. The epoxy resin was mixed with hardener at a proportion of 1:0.5 and this mixture was used to replace PC at 10% intervals starting from 0% to 40%. Six cubes were cast for each mix ratio and were cured in water at room temperature for 28 days. The first set of samples were treated by heating them in an oven to a temperature of 1000C for 1 hour before testing in compression while, the other set were not treated. Results showed that as the quantity of epoxy resin in the concrete enlarged the compressive strength values reduced. But a rise was observed at 30%. All concrete produced were structural in nature except for the heated 40% specimen. An optimal replacement strength of 32.10 N/mm2 at 30% inclusion (unheated) and lowest strength of 18.63 N/mm2 at 40% replacement (heated) were obtained. The heated samples experienced further reduction in their compressive strength values. An 8.94% drop in strength was observed between the maximum replacement values for the heated and unheated samples at 30%. In conclusion, epoxy resin concrete can be used for structural works at replacement levels up to 40%. However, if the concrete will be exposed to increased temperature of 1000C, then an optimal replacement level of 30% is recommended.

An investigation of palm oil fuel ash and limestone powder for use in sustainable high strength concrete construction

This study deals with the production of concrete with low CO2 emissions. For this reason, two materials, namely palm oil fuel ash (POFA) and limestone powder (LP), were used as mineral additions to replace conventional cement as much as possible. The results showed that concrete containing 60 wt% POFA could achieve the high strength requirements of ACI 363R from an age of 28 days. At a replacement level of 70 wt% of admixtures, the use of 10 wt% LP + 60 wt% POFA was a good mixture as it had the highest concrete compressive strength, had a minor effect on shrinkage strain and reduced heat generation by approximately 50% compared to cement concrete. Additionally, the use of POFA and LP is a good choice to produce environmentally friendly concrete, which can reduce the CO2 emissions of concrete by about 44–62% compared to cement concrete at similar strength.

Optimum Use of Recycled Waste Materials as Partial Replacement of Fine Aggregate in Portland Cement Concrete Mixes

This study explored the independent utilization of five common waste materials - rubber, plastic, glass, slag, and sewage sludge ash (SSA) - as partial replacement of fine aggregate in Portland cement concrete (PCC) mixes. The main objective was to determine an optimum substitution range for each waste material that would offer well performing concrete in terms of workability, compressive strength, and durability. To this end, multiple concrete batches were prepared, incorporating each waste material at four different levels: 5%, 10%, 15%, and 20% by weight of fine aggregate. Then, concrete samples (100-mm diameter × 200-mm tall cylinders) were cast from each batch and were moisture-cured for 7, 14, and 28 days prior to testing. Also, the chemical composition of each waste material was identified using FTIR spectroscopy to understand its impact on the development of concrete strength. While most waste led to the diminished strength gains at all substitution rates, the addition of glass, slag, and SSA contributed positively to the strength development at specific replacement levels: 5% for glass, 10 - 15% for slag, and 5 – 15% for SSA. Furthermore, these additions of glass and slag exhibited comparable workability and durability although SSA did not exhibit comparable workability and durability. The findings of this study can hold significant implications for environmental sustainability and cost effectiveness in construction projects.

Utilization of Granulated Blast Furnace Slag in Cement Mortar: Performance Analysis Against M-Sand

This study aims to explore the feasibility of incorporating Granulated Blast Furnace Slag (GBFS) as a sustainable alternative to manufactured sand (M-Sand) in cement mortar, to enhance both environmental sustainability and mechanical performance. The research involves a systematic investigation where M-Sand is progressively replaced by GBFS at varying levels of 10%, 20%, 30%, 40%, and 50%. The effects of these replacements are evaluated through a series of tests that focus on the mortar's physical properties, as well as its compressive and tensile strengths. Experimental results reveal that replacing 30% of M-Sand with GBFS produces the most favorable outcomes, with the compressive strength of the mortar exceeding that of the control mix by 12% after 28 days. The tensile strength also showed marked improvements at this replacement level. However, when the replacement level exceeds 30%, both compressive and tensile strengths begin to diminish, indicating that excessive substitution may adversely affect the mortar's structural integrity. The findings of this study provide valuable insights into the optimal use of GBFS in cement mortar, demonstrating that a 30% substitution not only enhances strength characteristics but also contributes to more sustainable construction practices by reducing reliance on natural sand resources. This research supports the potential of GBFS as a viable material for improving the environmental profile and durability of cement-based materials.

Influence of graphene nanoplatelets on the passivation and corrosion resistance of carbon steel bars in ordinary portland cement mortar

This study investigates the influence of adding graphene nanoplatelets (GNPs) to mortar mixtures on the corrosion behavior of embedded carbon steel rebars. Mortar mixtures were prepared with a water-to-cement ratio of 0.42 and GNP replacement levels of 0, 0.05, and 1 percent by weight of cement. After 28 days of curing in an environmental chamber, the passivity and kinetics of chloride induced corrosion initiation for the rebars were studied using a suite of electrochemical tests. The results suggest that incorporating GNPs at low concentrations may enhance the passivity and resistance to chloride-induced corrosion of carbon steel rebars; however, due to the large variability in the data, the findings are inconclusive. Potentiodynamic measurements revealed that the estimated average polarization resistance of steel rebars in 0 G (no GNP), 0.05 G, and 1 G specimens in the passive state was on average −182.3, −276.5, and −304.2 kΩ, respectively. Upon exposure to chloride solution, 0 G specimens, with an average corrosion potential of −600 mV vs. SCE, exhibited the lowest resistance, whereas 0.05 G specimens, with an average of −491 mV vs. SCE, showed the highest corrosion resistance. Results from electrical impedance spectroscopy were consistent with the potentiodynamic findings. Surface characterization also revealed that the inclusion of GNPs does not alter the surface roughness of the interface between steel rebar and paste. However, the interface between rebar ribs and mortar paste had higher surface roughness and porosity in all specimens regardless of GNPs replacement level. Visual inspections confirmed that the area around the rebar ribs at the interface is more conducive to the formation of crevice and pitting corrosion.

Mitigating autogenic shrinkage in high‐performance concrete using wollastonite: A structural enhancement approach

AbstractThis study investigates the influence of wollastonite fiber as a reinforcement in high‐performance concrete (HPC), focusing on its potential to mitigate autogenic shrinkage and enhance overall structural properties. HPC known for its superior strength and low permeability, often suffers from intensified autogenic shrinkage, leading to micro‐cracking and compromising durability. To address this challenge, wollastonite was incorporated at different substitutions (0%, 5%, 10%, and 15%) for both cement and aggregate. The experimental program involved a systematic evaluation of compressive strength, flexural strength, porosity, water absorption, and corrosion resistance with tests conducted at different curing periods. We found that the addition of 10% wollastonite significantly enhances compressive strength (up to 20% after 90 days) and flexural strength (maximum improvement of 21%). The water permeability was decreased by 29% and improved resistance to steel reinforcement corrosion, demonstrating enhanced durability compared to conventional HPC. However, diminishing returns were observed at higher wollastonite replacement levels (15%), indicating a threshold beyond which mechanical and durability benefits were reduced due to potential issues with fiber dispersion and workability. Our findings suggest that wollastonite is a promising, cost‐effective additive for improving HPC. The study contributes new understandings into optimizing HPC mixtures for greater durability and sustainability, while also reducing the environmental footprint through partial cement replacement. Future research is needed to explore the long‐term performance of wollastonite‐reinforced HPC under different environmental conditions and its combination with other supplementary cementitious materials for further enhancement.

Effect of Olive Waste Ash as a Partial Replacement of Cement on the Volume Stability of Cement Paste

Over the last decades, concrete has been excessively prone to cracks resulting from shrinkage. These dimensional changes can be affected by the incorporation of supplementary cementitious materials. This work used olive waste ash (OWA), which could substantially tackle this problem and achieve sustainability goals. For this issue, five cement paste mixes were prepared by replacing cement with OWA at different percentages varying from 0 to 20% by weight with a constant increment of 5%. The water-to-cement ratio was 0.45 for all mixes. Compressive strength and flexural strength were investigated at 7, 28, and 90 days. In addition, three shrinkage tests (drying, autogenous, and chemical) and expansion tests were also conducted for each mix and measured during 90 days of curing. The experimental findings indicated that there was a loss in compressive and flexural strength in the existence of OWA. Among all mixes containing OWA, the samples incorporating 10% OWA exhibited maximum strength values. Furthermore, the chemical and autogenous shrinkage decreased with the incorporation of OWA. However, the drying shrinkage decreased at lower levels of substitutions and increased at higher replacement levels. In addition, there was a growth in expansion rates for up to 10% of OWA content, followed by a decrease at higher levels (beyond 10%). Additionally, correlations between these volumetric stability tests were performed. It was shown that a positive linear correlation existed between chemical shrinkage and autogenous and drying shrinkage; however, there was a negative relationship between chemical shrinkage and expansion.

Investigation of strength, durability, and microstructure properties of concrete with waste marble powder as a partial replacement of cement

Purpose Cement plays a significant part in concrete, and with the increasing demand for concrete, cement output varies day by day, allowing production to carbon dioxide emissions. As well as marble processing creates stone slurry and solid discards. These are often dumped irresponsibly on open land, polluting the soil. This improper disposal of marble waste is a major environmental concern. This study aims to propose a sustainable solution for reusing this waste material as a concrete additive. Design/methodology/approach A total of 135 concrete cubes of size 150 × 150 × 150 mm, 54 concrete cylinders of size 150 mm dia. and 300 mm height and 54 concrete beams of size 150 × 150 × 700 mm were cast. The replacement was 0%, 2.5%, 5%, 7.5%, 10%, 12.5%, 15%, 17.5% and 20% by weight of cement with marble dust to create M30 concrete with a water-cement ratio of 0.45. The test was performed to find the compressive strength (CS), flexural strength (FS) and split tensile strength. Also, durability tests like rapid chloride penetration test (RCPT), acid attack, ultrasonic pulse velocity (UPV) and water permeability test were performed. Findings After 7 and 28 days of curing, it was found that replacing 5% of cement with marble powder led to an initial strength improvement of up to 25% for both curing periods. However, further increases in marble dust resulted in an inconsistent decrease in strength for all the mixtures. Also, durability properties like acid attack test, water permeability test and RCPT, showed good performance at the optimum percentage of waste marble powder (WMP) as cement replacement. The microscopic analysis revealed a denser pore structure at lower WMP replacement levels, likely due to the powder filling in gaps. Originality/value This study reveals that by substituting 5% (optimum) of cement with WMP, there was CS improvement up to 8.4% and 17% for both 7 and 28 days of curing. WMP is typically finer than cement particles and fills the voids in the concrete more effectively, resulting best performance at optimum percentage against RCPT, UPV, acid attack and water permeability.

Assessing the Impact of Shredded Polyethylene Terephthalate (PET) Post-Consumer Plastic as a Partial Replacement for Coarse Aggregates in Unreinforced Concrete

This study investigates the feasibility of incorporating shredded polyethylene terephthalate (PET) post-consumer plastic waste as a partial replacement for coarse aggregates in unreinforced concrete such as masonry blocks. Standard concrete blocks were produced with varying PET content (0%, 5%, 25%, 35%, 50%) and tested for workability, air content, density, compressive strength, flexural strength, and thermal conductivity. Results indicated that replacing up to 25% of traditional aggregates with PET maintains adequate compressive strength for non-load-bearing applications and enhances thermal insulation by reducing the thermal conductivity from 0.7 W/m·°K to 0.27 W/m·°K at 25% replacement level, representing a significant improvement of approximately 61%. Higher PET content (35–50%) resulted in reduced structural integrity but improved insulation, suggesting its suitability for non-structural applications. This research highlights the potential of using PET plastic waste in unreinforced concrete, promoting sustainable construction practices by reducing plastic waste and conserving natural resources.

Assessment of Various Mitigation Strategies of Alkali-Silica Reactions in Concrete Using Accelerated Mortar Test.

The widespread use of reinforced concrete continues to face challenges, particularly in mitigating alkali-silica reaction (ASR), due to its detrimental effects on concrete strength and durability. This paper investigates the effectiveness of using binary supplementary cementitious materials (SCMs) in mitigating ASR by incorporating metakaolin (MK) and waste glass powder (GP) as partial replacements for cement. Additionally, the potential of a new cement product, "NewCem Plus" (NCM), along with the use of basalt fibers and lithium, was evaluated through a 14-day accelerated mortar bar test following the ASTM C1260. This study also assessed concrete's properties such as its compressive strength and workability using the flow test. The results indicated that MK was effective, reducing expansion by 79%, 84%, and 88% with 10%, 20%, and 30% cement replacement, respectively, compared to the control mixture. On the other hand, GP showed a more modest reduction in expansion, with 10%, 20%, and 30% replacement levels reducing expansion by 20%, 43%, and 75%, respectively. Furthermore, the addition of lithium to MK significantly mitigated ASR, reducing expansion below the ASTM threshold. However, mixtures containing NewCem Plus, lithium, and basalt fibers showed minimal impact on ASR reduction. These findings underscore the viability of using binary or ternary blends of SCMs to mitigate ASR in concrete, encouraging their adoption in future concrete applications.

Strength and Durability Studies on Concrete Utilizing Sewage Sludge Ash and Treated Sewage Water

The effects of incorporating sewage sludge ash and treated sewage water on the strength and durability of concrete, with the goal of evaluating their viability as sustainable alternatives in construction materials. The sewage sludge ash was used as a replacement material to cement after burning of sewage sludge with high temperature of 800oC. So obtained sewage sludge ash was analysed for chemical, physical and morphological properties. Burning sewage sludge at high temperatures imparts pozzolanic properties to the resulting ash, which, when used as a cement replacement, improves concrete's compressive and tensile strengths. Various SSA replacement levels (5%, 10%, 15%, 20%, and 25%) were tested, with 15% SSA showing the highest strength gains. SSA affects setting time and workability, but treated sewage water does not significantly impact concrete properties. Concrete with SSA showed superior strength compared to conventional mixes with both fresh and treated water. Durability tests revealed that while SSA concrete experienced minor efflorescence in saltwater, it resisted acid attacks better than conventional concrete, indicating its good durability.

Growth, Evapotranspiration, Gas Exchange and Chl a Fluorescence of Ipê-Rosa Seedlings at Different Levels of Water Replacement.

In general, young plants in the establishment phase demonstrate sensitivity to changes in environmental conditions, especially regarding water availability. The effects of the seasonality of biophysical processes on plant physiology can trigger differential responses, even within the same region, making it necessary to conduct studies that characterize the physiological performance of the species at different spatial and temporal scales, making it possible to understand their needs and growth limits under water stress conditions. This paper aimed to evaluate the growth, gas exchange and Chl a fluorescence in ipê-rosa seedlings subjected to levels of water replacement (LWRs) of 100, 75, 50 and 25% in a greenhouse. The morphometric variables of plant height, diameter at stem height, numbers of leaves and leaflets, root length and volume, plant dry mass and leaf area were evaluated. The potential evapotranspiration of seedlings (ETc) was obtained using direct weighing, considering the water replacement of 100% of the mass variation between subsequent days as a reference; the cultivation coefficients (kc) were obtained using the ratio between ETc and the reference evapotranspiration (ETo) obtained by the Penman-Monteith FAO-56 method. Biomass and evapotranspiration data were combined to determine water sensitivity. Diurnal fluxes of gas exchange (net photosynthesis rate, transpiration rate, stomatal conductance, internal and atmospheric carbon ratio, water use efficiency and leaf temperature) and Chl a fluorescence (Fv/Fm, ΦPSII, ETR, Fv'/Fm', NPQ and qL) were evaluated. Water restriction caused reductions of 90.9 and 84.7% in the increase in height and diameter of seedlings subjected to 25% water replacement when compared to seedlings with 100% water replacement. In comparison, biomass accumulation was reduced by 96.9%. The kc values increased throughout the seedling production cycle, ranging from 0.59 to 2.86. Maximum water sensitivity occurred at 50% water replacement, with Ky = 1.62. Maximum carbon assimilation rates occurred in the morning, ranging from 6.11 to 12.50 µmol m-2 s-1. Ipê-rosa seedlings regulate the physiology of growth, gas exchange and Chl a fluorescence depending on the amount of water available, and only 25% of the water replacement in the substrate allows the seedlings to survive.