Sulfate Attack Research Articles

Studies on partial replacement of waste high density polyethylene (HDPE) and polypropylene (PP) plastic with fine aggregate (FA) on mechanical, durability and thermal properties of M30 and M40 grade concrete

The aim of the present paper is to incorporate two different waste plastic materials that is High-Density Polyethylene (HDPE) and Poly-Propylene (PP), were replaced with Fine Aggregate (FA) at a 10% by 2.5% increment. The widespread formation of HDPE and PP waste plastics has become a major environmental issue, endangering ecosystems and human health. Traditional disposal techniques, such as landfills and incineration, lead to pollution and resource depletion. Incorporating these polymers into concrete provides a long-term solution that reduces environmental effect while improving material qualities. The Different tests conducted are compressive strength (3, 7, 28 and 60 days) (150 × 150x150 mm), flexural strength (3, 7, 28 and 60 days) (100 × 100x500 mm), acid attack (28, 56 and 90 days) (100 × 100x100 mm), sulphate attack (28, 56 and 90 days) (100 × 100x100 mm), and thermal conductivity (180 mm dia x 20 mm thick). The compressive strengths of 40.52 MPa and 38.41 MPa for PP and HDPE material were observed in M30-grade concrete, respectively. Similarly, for M40-grade concrete, 43.6 MPa and 41.8 MPa are for PP and HDPE material, respectively. The optimum percentages of 5% and 7.5 for PP and HDPE material, respectively, can be replaced in concrete for flexural strength in both M30 and M40 grades. The least percentage loss in acid attack was observed at 28 days for both HDPE and PP material, but for 56 days and 90 days, the percentage loss of weight was significantly less (< 5%). The sulphate attack for both M30 and M40 grade concrete showed less than 10% percentage loss in weight after 90 days. Thermal conductivity (k) was also reduced by 30–35% for both HDPE and PP material, with 10% replacement in concrete for M30 and M40 grades. The use of Waste HDPE and PP material can be used to improve the mechanical, durability & thermal property of M30 and M40 grade concrete under controlled conditions.

Mechanical Behavior and Durability of Perlite Based Mortar Exposed to Sodium Sulfate Attack

The objective of this study is to gather additional on the impact of perlite on both the mechanical properties and resistance to chemical attacks of materials. Various combinations ,incorporating perlite in the form of cement additions, were examined. Five different substitution rates of 10 %, 15 %, 20 %, 25 %,and 30 % of cement with powder perlite were utilized for comparison with plain cement. The findings indicate that the interaction between lime,silica,and alumina in powder perlite results in the formation of several hydrates, such as calcium silicate hydrate, hydrated calcium aluminates,and hydrated gelhenite.Our research focuses on the development of natural perlite from maghnia as a potentially pozzolanic supplementary cementing material. In evaluating the pozzolanicity of this material, it was observed that external aggressions, such as chlorides, CO2, and chemical attacks, can compromise the physical and mechanical properties of concrete,affecting its long-term durability. However,natural pozzolans like pelite exhibit a positive influence on the durability of mortars against sulphate attacks. Test results revealed specimens with no apparent degradation, indicating that sulphate ions in the solution did not adversely affect perlite-based mortars. There is a growing preference for mineral additives with lower production costs than cement. Consequently, the optimal mixture was determined to be one containing 25 % perlite. However, cement pastes and mortars incorporating up to 20 % perlite demonstrated satisfactory physical and mechanical properties, comparable to materials without perlite. The investigation into the perlite materials used in conjunction with cement suggests the potential for sustainable concrete. Experimental results indicate that natural perlite powder from Maghnia can be considered a good pozzolanic material, suitable as a mineral admixture in cement production.

Effects of carbonation curing on chemical attack in cement paste incorporating liquid-crystal display glass powder as a partial binder replacement

This study investigates the chemical resistance of cement paste by incorporating liquid-crystal display (LCD) glass powder as a partial replacement for cement. The samples, cured under water and carbonation, were subjected to adverse chemical attacks over a period of up to 90 days, using MgSO4 and H2SO4 for the sulphate attack and acid attack, respectively. The results demonstrate a decrease in compressive strength by upto 14.63% and 32.32% for water- and carbonation-cured samples, respectively, and an increase in carbonation degree by upto 100% with the incorporation of glass powder at 28 days. Under sulphate attack, water curing and carbonation curing displayed strength increase of 21.24–36.13% and 7.56–8.06%, respectively, at 90 days. However, carbonation-cured samples experienced greater leaching of silica and calcium. The compressive strength decreased with acid attack duration, with glass powder incorporation mitigating strength loss in carbonation-cured samples. At 30 days, with an incorporation rate of 30% glass powder, the strength loss was reduced by 37.66% for the carbonation-cured samples. The enhanced resistance with incorporation of glass powder was also evident from mercury intrusion porosimetry results that indicated decreased intrusion levels. Visual inspection revealed a different consistency of white substance deposition, suggesting resistance mechanisms differed between curing methods.

Durability evaluation and lifetime prediction of recycled coarse aggregate self-compacting concrete after freeze-thaw and sulfate erosion coupling

This paper aims to study the durability of recycled coarse aggregate self-compacting concrete (RCASCC) after being subjected to freeze-thaw and sulfate coupling. The durability comprehensive evaluation index of RCASCC based on the entropy weight method was defined, and the variation law of the durability comprehensive evaluation index concerning RCA substitution rate, freeze-thaw environment, and coupling frequency was obtained. GM (1, 1) model based on grey system theory was used to evaluate the durability of RCASCC under the coupling effects of freeze-thaw and sulfate attack. The results show that there are some differences in the accuracy of the four GM (1, 1) models. It is recommended that the EGM model can be used to predict the durability of the RCASCC under the coupled effects of freeze-thaw and sulfate erosion. Moreover, the working life of RCASCC under the coupling effects in the outdoor environments of northeast, north, and northwest China was calculated, when the comprehensive evaluation index of durability decreases to 75% as the failure criterion. A multi-criteria analysis employing TOPSIS and VIKOR methods was conducted to evaluate the durability of RCASCC under these coupling effects. A multi criteria analysis was conducted on the durability of RCASCC under the coupling effects of freeze-thaw and sulfate erosion using TOPSIS and VIKOR methods. Under these two rankings, the splitting tensile strength is the index that changes the most after coupling effects, while the compressive strength changes relatively little. The importance of dynamic elastic modulus and weight is different due to different materials and evaluation methods. RC100-H typically exhibits the largest variation, while NC-H and RC50-NM typically exhibit smaller variations.

Coal-derived char for durability improvement of cement stabilized soil under freeze–thaw, wet–dry, and sulfate attack

Cement soil stabilization is widely used in civil engineering to improve the performance of soils subjected to freeze–thaw (F–T), wet–dry (W–D), and sulfate attack (SA). Due to the negative impacts associated with manufacturing cement, the development of eco-friendly and sustainable additives is highly desirable. Coal-derived char is a cost-effective byproduct of the coal pyrolysis process. In this study, the influence of coal char on mineralogical, microstructural, physical, and mechanical properties of cement stabilized soils (with cement contents of 0%–20% and char contents of 0%–30%) subjected to F–T cycles, W–D cycles, and SA is investigated. Compared to cement stabilized soils, char-cement stabilized soils exhibit up to 60.8% fewer volume changes during F–T cycles and 31.6% fewer during W–D cycles. The compressive strength of char-cement stabilized soils with cement contents of 5%, 10%, and 20% are on average 7.9%, 17.6%, and 11.0%, respectively, higher than that of cement stabilized soil subjected to F–T cycles, W–D cycles, or SA. The inclusion of char promotes cement hydration and results in the formation of more amorphous hydration products that fill voids or cover soil minerals. The findings indicate the promising potential of coal char in enhancing soil performance under a range of challenging environmental conditions.

A novel approach for the lifetime prediction and structural health monitoring of concrete sewer systems exposed to biogenic sulphide corrosion

A novel, combined experimental-modelling approach is presented for the estimation of the corrosion depth, load bearing capacity and lifetime of unreinforced concrete sewer pipes exposed to prolonged biogenic sulphide corrosion. The biogenic sulphide corrosion process is mimicked through two types of representative chemical experiments, namely: (i) long-term experiments performed under moderately controlled pH conditions, where dry-cast concrete cube samples are exposed to monthly refreshed sulphuric acid solutions with initial pH values of 3, 2 and 1 for a period of 12 months, and (ii) short-term experiments carried out under highly controlled pH conditions, in which dry-cast concrete disk samples are subjected to sulphuric acid solutions with almost constant pH values of 2, 1 and 0.5 for a period of two months. By applying X-ray diffraction, optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy analyses, insight into the micro-scale morphology and elemental composition of the corrosion profile is obtained. In addition, the corrosion front and depth characteristics are measured by conducting phenolphthalein tests and analyses of surface colour and texture of macro-scale samples. From the experimental results, the time course of the corrosion depth is calibrated with a model for sulphate attack under a constant pH level. The model formulation is combined with detailed finite element method results from the literature to predict the long-term load bearing capacity of a concrete sewer pipe. The model is subsequently generalised for sulphate corrosion under a varying pH level. When combined with the installation of pH measuring devices on the inside of sewer pipes, the current engineering model may serve as an excellent practical tool for continuously monitoring the structural health and predicting the lifetime of in-situ sewer systems subject to sulphate attack under random acidity fluctuations.

Strength degradation of foamed cement paste under sulfate attack

Foamed cement paste is increasingly being applied in the construction of road embankments, bridge abutments, slope treatments, and pipeline backfilling. Constructed foamed cement paste may suffer from sulfate attacks in certain environments, such as offshore regions and salty soil areas. However, the long-term performance of foamed cement paste under such circumstances remains unclear. In this study, laboratory tests are conducted to evaluate the strength deterioration of foamed cement paste after erosion by sulfate attack. Factors influencing the density of the foamed cement paste, concentration of the sulfate solution, and cation type (i.e., Na+ and Mg2+) are considered. The results indicate that the strength of the foamed cement paste decreases with increasing immersion time. The Na2SO4 solution has a more severe erosion effect than the MgSO4 solution when other conditions remain constant. Finally, X-ray diffraction is conducted to identify the phase of the crystalline material in the specimen. This study will be beneficial in the application of foamed cement paste in regions with salt-rich soils.

Fresh, hardened, durability and microstructure properties of seawater concrete: A systematic review

Seawater concrete (SWC) is an environmentally friendly construction material that addresses freshwater scarcity concerns by utilising seawater as a mixing water source. This review study comprehensively examines SWC by focusing on its fresh properties, hardened properties, seawater composition, microstructure and porosity, hydration process, durability, test methods and electrical resistivity. The study analyses the influence of additives and admixtures on SWC’s performance by considering constituents such as cement, aggregates and seawater. It also explores the impact of manufacturing techniques, including mix design. The potential of SWC is revealed and compared with that of conventional concrete by evaluating and comparing their mechanical properties, such as compressive strength, modulus of elasticity, stress-strain behaviours, tensile strength and flexural strength. This study primarily aims to thoroughly examine the characteristics of SWC in its fresh and hardened states. It also assesses the advantages and drawbacks of seawater as a mixing water source. Moreover, this study delves into the impact of seawater composition on crucial aspects, such as the hydration process, microstructure and porosity of concrete. It also used various test methods to explore SWC durability, including resistance to chloride ingress, sulphate attack and carbonation. Furthermore, the importance of electrical resistivity for corrosion prevention is discussed in this study. The carbon-negative cement production and carbonation curing of seawater concrete underscore groundbreaking advancements, emphasizing sustainability and climate mitigation in the construction industry. Overall, this study aims to enhance the comprehension of SWC and provide valuable insights for engineers, researchers and policymakers in concrete technology.

Optimization and Characterization of Cementitious Composites Combining Maximum Amounts of Waste Glass Powder and Treated Glass Aggregates

This work investigates the combined use of waste glass aggregates (GA) and glass powder (GP) in cementitious mortars. For this reason, the optimized incorporation of GA by natural aggregates (NA) replacements was first studied after applying a surface roughening method with hydrofluoric acid. The compressive strength results were utilized to select the best mixture with GA. Then, different GP contents were added by cements substitutions to the optimized GA-based mortar. A control mortar without GA and GP amounts was also casted as a reference for comparison. The detailed mechanical, physical and durability properties of the resulted mixtures with combined GA and GP were assessed by considering the compressive and flexural strengths, ultra-sonic pulse velocity, alkali-silica reaction (ASR), rapid chloride permeability test (RCPT), magnesium sulphate attack and sulfuric acid resistance. The microstructure of different optimized (GA + GP)-combinations was characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS)in order to analyse the interfacial transition zone (ITZ) between glass materials and the surrounding matrix. The results showed that the optimized composition with 75% GA and 25% GP was shown with high compacity and durability characteristics due to the increased GA/matrix ITZ and the formation of C–(N,K)–S–H products with C–S–H.

Experimental Investigation on Partial Replacement of Cement by Granite Powder on Mortar

This paper intends to investigate the possibility of producing low costs enhanced mortar by Granite powder. By taking the enormous amount of cement, it affects the environment badly and demand for cement was increasing day by day. So, by partially replacing Granite powder with cement in construction field. It can fulfill the objectives of catering to the needs of the construction sector while simultaneously promoting an eco-friendly and pristine atmosphere. Partial replacement of cement by using granite powder in mortar gives sufficient strength. The conventional mortar mix consists of cement, fine aggregate, and water. In this experimental study granite powder was used with different percentage, such as 20% 25%, 30% 35%. The mixture was prepared and mortar cubes were made and allowed for curing. It is concluded that, he immersion of cement mortar in magnesium sulphate is better when compared to sodium sulphate and the sulphate attack is lesser in magnesium sulphate. The residual compression strength for the cement mortar in the proportion of granite content 30% is higher.

Sustainable reuse of waste ceramic tiles powder and waste brick powder as a replacement for cement on green high strength concrete properties

Nowadays, reducing construction waste has grabbed the attention. As bricks and ceramic tiles represent more than 50% of the ceramic waste in many European countries. Thus, the recycling of this waste type is one of the most significant challenges within the paradigm of the circular economy. This paper investigated the impact of substitution levels of cement by waste ceramic powder (WCP) and waste brick powder (WBP) at 0%, 5%, 10% and 15%, on the HSC characteristics. The WBP and WCP materials were characterized in detail by laser granulometry, XRF and XRD measurements, followed by standard mixing, production, and curing of concrete samples. The experiments on dry density, modulus of elasticity, flexural strength, splitting tensile strength, compressive strength, resistance to sulfate attack, water absorption and ultrasonic pulse velocity were conducted to evaluate the hardened properties of concrete. It was demonstrated that the durability and strength of concrete containing WBP and WCP as partial replacements for cement are marginally inferior to those of the control sample. On the other hand, samples containing WBP had a lesser negative effect on HSC properties in comparison with samples containing WCP. However, employing a 5% WBP with 10% WCP mixture enhanced the characteristics of the HSC in comparison to samples containing various percentages of WCP individually. In addition, the microstructure analyses revealed that the addition of 10% WCP and 5%WBP to HSC specimens resulted in higher hydration products and a slightly denser concrete matrix compared to samples containing various percentages of WCP individually. Research findings indicate that a 15% substitution of cement with WCP or WBP illustrated an environmental benefit in concrete production due to a 13.1% reduction in specific energy consumption.

The influence of nanosunflower ash and nanowalnut shell ash on sustainable lightweight self-compacting concrete characteristics

The absence of biodegradability exhibited by plastics is a matter of significant concern among environmentalists and scientists on a global scale. Therefore, it is essential to figure out potential pathways for the use of recycled plastics. The prospective applications of its utilisation in concrete are noteworthy. The use of recycled plastic into concrete, either as a partial or complete substitution for natural aggregates, addresses the issue of its proper disposal besides contributing to the preservation of natural aggregate resources. Furthermore, the use of agricultural wastes has been regarded as a very promising waste-based substance in the industry of concrete manufacturing, with the aim of fostering the creation of an environmentally sustainable construction material. This paper illustrates the impact of nano sunflower ash (NSFA) and nano walnut shells ash (NWSA) on durability (compressive strength and density after exposure to 800 °C and sulphate attack), mechanical properties (flexural, splitting tensile and compressive strength) and fresh characteristics (slump flow diameter, T50, V-funnel flow time, L-box height ratio, segregation resistance and density) of lightweight self-compacting concrete (LWSCC). The waste walnut shells and local Iraqi sunflower were calcinated at 700 ± 50 °C for 2 h and milled for 3 h using ball milling for producing NSFA and NWSA. The ball milling succeeded in reducing the particle size lower than 75 nm for NSFA and NWSA. The preparation of seven LWSCC concrete mixes was carried out to obtain a control mix, three mixtures were created using 10%, 20% and 30% NWSA, and the other three mixtures included 10%, 20% and 30% NSFA. The normal weight coarse aggregates were substituted by the plastic waste lightweight coarse aggregate with a ratio of 75%. The fresh LWSCC passing capacity, segregation resistance, and filling capability were evaluated. The hardened characteristics of LWSCC were evaluated by determining the flexural and splitting tensile strength at 7, 14 and 28 days and the compressive strength was measured at 7, 14, 28 and 60 days. Dry density and compressive strength were measured after exposing mixes to a temperature of 800 °C for 3 h and immersed in 10% magnesium sulphate attack. The results demonstrated that the LWSCC mechanical characteristics were reduced when the percentages of NWSA and NSFA increased, except for 10% NWSA substitution ratio which had an increase in splitting tensile strength test and similar flexural strength test to the control mixture. A minor change in mechanical characteristics was observed within the results of LWSCC dry density and compressive strength incorporating various NSFA and NWSA` contents after exposing to temperature 800 °C and immersed in 10% magnesium sulphate attack. Furthermore, according to the findings, it is possible to use a combination of materials consisting of 10–20% NSFA and 10–20% NWSA to produce LWSCC.

Pore structure, mechanical property and permeability of concrete under sulfate attack exposed to freeze–thaw cycles

Pore structure, mechanical property and permeability of concrete under sulfate attack exposed to freeze–thaw cycles

Performance assessment of blended self-compacting concrete with ferrochrome slag as fine aggregate using functional ANOVA

The current study explored the feasibility of re-use of ferrochrome slag (FS), a waste byproduct from the ferrochrome industry as a replacement to fine aggregate in self-compacting concrete (SCC) with cement and fly ash as binders. The study investigated the mechanical and durability characteristics of SCC of M25 grade, incorporating FS in lieu of fine aggregate, up to 60 % replacement levels. Albeit workability of fresh concrete decreased with the increase of FS content, they were within the recommended limits of EFNARC for SCC. Considerable decreases in compressive, tensile and flexural strengths were observed in the mixtures with FS contents above 40 %. Slightly better performances in terms of water absorption, sorptivity, chloride ion permeability and sulphate attack were found in the concretes partially blended with FS. Leaching of chromium (Cr) from FS-incorporated self-compacting concrete samples were within the Indian discharge limits. Microstructural studies were conducted to decipher the arrangement of components in the concrete as well as determine the elemental composition of ferrochrome slag. Functional analysis of variance (ANOVA) was conducted to determine the significance of functional components in explaining the variability of the mechanical properties expressed as continuous functions. The test findings indicate that there is no statistical difference in the compressive strength and split tensile strength as a result of substituting a portion of sand with FS. Nevertheless, a rise in flexural strength is noticed after surpassing a 5 % substitution.

Ion transport mechanism and diffusion model establishment in recycled aggregate concrete subjected to magnesium, sulfate, and chloride attack

Recycled aggregate concrete (RAC), which is used in Northwest China, is inevitably subjected to various aggressive environments. However, the aggressive ions of chloride, sulfate, and magnesium and the original ions of calcium and hydroxide in RAC under the combined action of magnesium-sulfate-chloride attack and dry–wet (D&W) cycles have received little attention in previous studies. Therefore, in this study, the content of aggressive and original ions in exposed RAC was quantified, and the influence of the replacement ratio of supplementary cementitious materials (SCMs) on diffusion was investigated. Results showed that the contents of chloride, sulfate, and magnesium in exposed RAC increased with an increase in the replacement ratio of silica fume (SF) and metakaolin (MK). In contrast, the contents decreased with the increase in the replacement ratio of granulated blast furnace slag (GBFS). At the same exposure time and depth, the content of RAC with ternary cementitious materials from the highest to the lowest was in the order of cement–fly ash –SF, cement–fly ash–MK, and cement–fly ash–GBFS. Visual appearance, relative compressive strength, and the diffusion coefficient exhibited a similar change law. An exponential relationship was observed between the diffusion and time delay coefficients and the replacement ratio of SCMs, and the content of aggressive ions on the exposed surface decreased linearly with increasing exposure time. Diffusion models of aggressive ions were established to consider the multiple effects. Aggressive ion–original ion interaction influenced the mineral phases’ composition in the corrosive zone and led to a difference in the diffusion process and depth.

Utilisation of Waste Shea Nutshell Fine-Grained Particles to Enhanced Strength and Durability Behaviour of Concrete

Shea nutshells possess properties that stabilise soil enough to resist water penetration. It is a waste material and incorporating it as an additive material in concrete will be a means by which it can be recycled. With this projection, the study incorporated shea nutshell particles (SSP) as fine aggregates in concrete. The aim was to determine their influence on strength and durability properties. Fine aggregates were partially replaced with 0%, 10%, 20%, 30%, and 40% SSP based on the weight of the aggregate, and labelled as A0, S10, S20, S30 and S40 respectively. Concrete cubes of size 150 mm and cylinders of diameter 150 mm and height of 300 mm were prepared and cured for 7, 14, 28, and 90 days. The concrete was tested for density, compressive strength, split tensile strength, water absorption, and sulphate attack. The inclusion of the SSP did not improve the compressive and split tensile strengths. However, water absorption and sulphate attack decreased with further addition. Though, strength properties did not appreciate, values at 10%, 20% and 30% additions in 28 and 90 days satisfied the 28 days minimum requirement of 25 N/mm2. Hence, the study recommends the use of SSP in concrete production up to 30%.

Influence of pozzolanic addition on strength and microstructure of metakaolin-based concrete.

The intent of this study is to explore the physical properties and long-term performance of concrete made with metakaolin (MK) as a binder, using microsilica (MS) and nanosilica (NS) as substitutes for a portion of the ordinary Portland cement (OPC) content. The dosage of MS was varied from 5% to 15% for OPC-MK-MS blends, and the dosage of NS was varied from 0.5% to 1.5% for OPC-MK-NS blends. Incorporation of these pozzolans accelerated the hardening process and reduced the flowability, consistency, and setting time of the cement paste. In addition, it produced a denser matrix, improving the strength of the concrete matrix, as confirmed by scanning electron microscopy and X-ray diffraction analysis. The use of MS enhanced the strength by 10.37%, and the utilization of NS increased the strength by 11.48% at 28 days. It also reduced the penetrability of the matrix with a maximum reduction in the water absorption (35.82%) and improved the resistance to the sulfate attack for specimens containing 1% NS in the presence of 10% MK. Based on these results, NS in the presence of MK can be used to obtain cementitious structures with the enhanced strength and durability.

Sulphate resistance of low-clinker engineered cementitious composites examined by MicroXRF imaging.

Engineered cementitious composites (ECC) are a class of high-performing fibre-reinforced cementitious materials recognised for their increased ductility and durability compared to conventional cement-based materials, owing to their autogenously controlled tight crack widths, even when subjected to high strains. To reduce ECC's environmental impact, this research examines the use of a low-clinker binder - limestone-calcined clay cement (LC3) - as an alternative to portland cement (PC), along with fly ash to further reduce the clinker proportion and the embodied CO2 of the formulations. In conventional concrete, LC3 hydrates to a denser microstructure resulting from the synergistic reaction between limestone and calcined clay. At the lower water contents typical of ECC and with the presence of fly ash, the influence of the binder composition on the microstructure is difficult to anticipate. To examine the influence of these compositional variables on microstructure, permeability and durability, the sulphate resistance of LC3-based ECC is explored. Specifically, the ECC-LC3 blends are designed with high clinker replacement rate of 75% by mass of binder and contain either conventional fly ash or reclaimed fly ash at 50% by mass of binder. Expansion of ECC-LC3 samples subjected to standard sodium sulphate test conditions was measured up to 12 months and the depth of penetration of sulphates into the ECC-LC3 of varying compositions was quantified using micro-X-Ray Fluorescence (microXRF) imaging and modelling. The expansion results show that the ECC-LC3 formulations performed better than the PC samples and can provide adequate resistance to external sulphate attack, even when reclaimed fly ashes are used in place of the conventional ash. In addition, the shallow penetration of sulphate into these cementitious composites demonstrates the low diffusion coefficients values that were determined using the quantitative data from MicroXRF imaging.

Investigation of tensile strength performance of green concrete incorporating steel slag

This study examined the compressive and tensile strength performance of steel slag-containing concrete composites in a sulphate environment. Steel slag sourced locally was mechanically crushed and sieved into aggregates ranging in size from 20 to 1 mm. The control concrete of grade 20 and other five (5) batches of concrete with 10 to 50% steel slag at a step of 10% as replacement for natural coarse aggregate were produced. The physical properties of the aggregate specimens (steel slag and granite) were evaluated in the laboratory, as well as the concrete workability and the 7- and 28-day compressive and tensile strengths after exposure to 50 g/l of magnesium and sodium for 7 and 28 days. According to the results, the concrete workability decreased as the steel slag content increases. The 20 N/mm2 desire strength with rise in compressive and split tensile strengths as the steel slag contents increased from 0 to 50% after curing in water for 28 days. The concrete compressive and tensile strengths improved with steel slag content ranging from 0 to 40% but decreased with increase in steel slag content from 30 to 50% after exposure to Na2SO4 for 28 days. For the concrete exposed to MgSO4, the compressive and split tensile strengths increased when the steel slag content increased from 0 to 40% before it decreased with further increase in steel slag from 40 to 50% after 28 days. The experimental findings revealed that up to 40% steel slag is sufficient as replacement for natural coarse aggregate in concrete work exposed to aggressive sulphate climate. Thus, for improved compressive and tensile performance, the optimum of 40% steel slag is suggested as replacement for natural coarse aggregate substitution for healthier sulphate attack resistance.

Reliability of using secondary and tertiary treated wastewater in concrete mixing and curing

AbstractWater scarcity is a problem that faces many regions. In a developing and arid countries, the need for fresh water is exponentially increasing. One of the most water consuming industries is the construction industry, especially in concrete manufacturing. This research is an evaluation of the Reliability of recycled wastewater to be used in concrete manufacturing. Two different wastewater treatment regimens are implemented: secondary and tertiary treated wastewater. The treated wastewater, either secondary or tertiary, replaces potable water with percentages of 25%, 50%, and 100%. The mixture of the two types of water is used in concrete mixing and curing. Control specimens with pure potable water are cast for the comparison. The experimental program investigated the cement setting, and for fresh concrete slump test is performed on all concrete mixtures. The hardened concrete is tested in compression and flexural strengths at ages of 7 days, 28 days, and 90 days. To investigate concrete durability, permeability test is conducted in addition to sulfate attack resistance. The concrete chemical composition is compared using the X-Ray Defragmentation (XRD) test. The results show that the treated wastewater may delay both the initial and final setting. The phenomenon is more pronounced in secondary treated wastewater. No significant effect on concrete performance in the fresh state is detected. For the compressive strength, both treatment regimens can be safely used. However, the flexural strength is reduced at the late ages. Using treated wastewater affects the permeability of concrete to be more durable and protect the reinforcement steel from rusting. For the XRD test, the results show different intensities and positions of the peaks of the different compounds encountered in the treated wastewater. Under sulfate attach, the treated wastewater specimens give higher expansion compared with potable water. In conclusion secondary and tertiary treated wastewater can be used in concrete mixing and curing. However, the manufactured concrete should be protected from sulfate attack to avoid excessive expansion.