Split Tensile Strength Research Articles

Experimental Study On Strength of Concrete Using Nano silica

The test on hardened concrete were destructive test on cube for size (150×150×150 mm) at 7, 14, 28 days of curing as per IS: 516-1959, flexural strength test on beam (100×100×500 mm) at 7, 14, 28 days of curing as per IS: 516-1959 and split tensile strength test on cylinder (100mmφ×200mm) at7, 14, 28 days of curing as per IS: 5816-1999. The primary aim of this study is to assess the effectiveness of silica fume as a pozzolanic material for replacing cement in concrete. It is anticipated that incorporating silica fume into concrete will enhance its strength properties. In this study, the combination of 5% nanosilica and 10%metakaolin which replaced part of the cement had the best results in the Mechanical properties of concrete with a 15% increase in the compressive strength and a 40%increase in the flexural and tensile strength of concrete.

Assessment of fly ash and ceramic powder incorporated concrete with steam-treated recycled concrete aggregates prioritising nano-silica

Present research involves determining the effects of a proposed novel nano-silica prioritized-steam-treated recycled concrete aggregate (RCA) on microstructural, mechanical, and durability aspects of concrete incorporated with waste ceramic powder (WCP). The study on novel nano-silica prioritized-steam-treated recycled concrete aggregate revealed that 3% nano-silica induction with 3-h steam treatment for 50% adhered mortar bonded RCA performed optimally. The physical characterization of treated RCA showed improvement compared to untreated RCA, which was confirmed by microstructure study indicating the formation of additional calcium silicate hydrates in the bonded adhered mortar of treated RCA. Furthermore, as WCP has significant contents of alumina and silica, an optimum ternary binder mix was developed with cement, fly ash, and WCP. Later, a study was performed to analyse the performance of treated RCA incorporated in WCP prioritized concrete mix. The mechanical performance of WCP prioritized concrete with treated RCA was investigated through compressive strength, flexural strength, split tensile strength, and modulus of elasticity. The quality was ensured through ultrasonic pulse velocity, water absorption, and density characterization. The durability of concrete was studied with 5% concentrated hydrochloric acid attack and sea water (pH = 8.3 to 8.7) exposure conditions for a duration of 148 days (including 28 days of portable water curing period). Overall, 30% of the ternary mixture based on WCP prioritization, 50% adhere mortar-based RCA, and 3% of nano-silica prioritization steam treatment (3 h) demonstrated the best performance in terms of both mechanical and durability aspects. The study concluded that due to its improved performance, the innovative nano-silica priority steam treatment approach could replace 100% of RCA in concrete. Furthermore, treated RCA being advantageous because of easy adoptable technique for real-time practices as well as maintaining consistency regards RCA characteristics throughout concrete mixture be the challenge.

Utilization of wollastonite, jarosite, and their blends for the sustainable development of concrete paver block mixes containing reclaimed asphalt pavement aggregates.

While several research studies considered the utilization of reclaimed asphalt pavement (RAP) aggregates for asphalt and concrete pavements, very few attempted its possible utilization for precast concrete applications like concrete paver blocks (CPBs). Moreover, few attempts made in the recent past to improve the strength properties of RAP inclusive concrete mixes by incorporating certain supplementary cementitious materials (SCMs) have reported an insignificant or marginal effect. The present study attempts to comprehensively investigate the utilization potential of some locally and abundantly available materials having suitable physicochemical properties to improve the performance of a zero-slump CPB mix containing 50% RAP aggregates. The studied filler materials, namely, wollastonite (naturally occurring calcium metasilicate mineral) and jarosite (hazardous zinc industry waste), were used to replace 5-15% and 10-20% by volume of Portland cement in the 50% RAP CPB mix. Apart from their individual effects, the efficacy of wollastonite-jarosite blends was also investigated. Considering the lack of indoor storage facilities and economic aspects of CPBs, the influence of water spray curing regime on the performance of the RAP CPB mixes was studied and compared to that of continuous water curing regime. Inclusion of the considered fillers was found to statistically and significantly enhance the flexural strength, tensile splitting strength, and abrasion resistance of the 50% RAP CPB mix; however, the compressive strength (in most cases), permeable voids, water absorption, and water permeability properties showed an insignificant improvement. Results of thermogravimetric analysis confirmed the occurrence of pozzolanic reactivity, and microstructure analysis revealed improvements in packing of concrete matrix and ITZ with filler inclusion qualitatively substantiating the improvements in strength and durability characteristics. The toxicity characteristics of heavy metals that may leach from the hazardous jarosite-based RAP CPB mixes were found to be within permissible limits. Based on the performance requirements specified by IS, IRC, and ASTM standards, all the RAP CPB mixes with filler inclusions fulfilled the acceptance criteria for heavy traffic applications, and water spray curing can enact as an alternate method for curing these mixes. However, to avail maximum performance benefits, it is recommended to use 5% wollastonite, 15% jarosite, and a combination of 10% wollastonite and 10% jarosite as a Portland cement substitute to produce sustainable eco-friendly RAP CPB mixes.

Optimisation of mechanical properties and impact resistance of basalt fibre reinforced concrete containing silica fume: Experimental and response surface assessment

Although Basalt fibre reinforced concrete (BFRC) has a proven record of outstanding behaviour, concerns regarding the decline in its performance beyond certain content remains a major concern. To address this concern, a varying content of Silica Fume (SF) was introduced into the BFRC mix, and their combined influence on concrete's mechanical and impact resistance was investigated using experimental and Response Surface Analysis (RSA). Using regression models developed from experimental results, 13 responses of statistically designed experiments were predicted. The findings revealed significant improvement in the concrete performance with increases between 28% and 65% in compressive strength, 35%–107% in split tensile strength, 11%–46% in flexural strength and 117%–150% in the impact resistance. Therefore, appropriate proportions of BF and SF can be utilised as an eco-friendly sustainable material in concrete.

Study on the use of CO2 to strengthen recycled aggregates and pervious concrete

Recycled aggregates (RA) are crushed materials derived from waste concrete or construction debris that play a crucial role in the recycling of construction waste resources. However, RA's irregular particle shape and surface cement paste adhesions limit its potential in pervious concrete applications. To overcome this limitation, the use of carbonation treatment methods to process RA and produce recycled aggregate pervious concrete (RAPC) was investigated. RA was subjected to a pre-carbonation treatment, followed by the production of RAPC mixtures using three slurry-to-aggregate ratios, carbonation curing, and two-step carbonation strengthening, which enhanced the physical and mechanical properties of the specimens. Then, the measurements including permeability coefficient, connected pore fraction, splitting tensile strength, and CT microstructure analysis were performed. A carbon footprint accounting system from "cradle to gate" was conducted to assess the specimens. Our results highlight that an increase in the slurry-to-aggregate ratio in RAPC mixtures results in enhanced mechanical properties but negatively affects permeability performance. By pre-carbonating RA, we significantly increase the pervious concrete's splitting tensile strength, up to 100%, and maintain the compactability while ensuring permeability performance (maximum 3.91% reduction for specimens with slurry-to-aggregate ratio of 0.3). The carbonation treatment method used in our study has ideal environmental effects, as it theoretically sequesters up to 58.12% of the total carbon emissions produced during the production process.

Investigating the synergistic effects of carbon fiber and silica fume on concrete strength and eco-efficiency

The present study endeavors to quantitatively evaluate the performance of concrete by incorporating carbon fiber reinforcement and micro silica addition. A comprehensive experimental investigation is conducted to examine the effects of these two additives on the concrete properties. Additionally, an eco-efficiency analysis is performed to assess the environmental impact of the modified concrete. Furthermore, a response surface optimization technique is employed to optimize the concrete mix design based on desired performance criteria. The findings of this study provide valuable insights into enhancing the performance and eco-efficiency of concrete by utilizing carbon fiber reinforcement and micro silica addition. To accomplish this objective, varying percentages of CF (ranging from 0% to 0.80%) and different densities of micro silica (ranging from 0 kg/m3 to 50 kg/m3) were incorporated into the concrete mixtures. Subsequent tests were conducted to evaluate the mechanical properties, including compressive strength, split tensile strength, and flexural strength, at least 3 specimens for each mix were tested. Furthermore, the eco-strength efficiency of the concrete mixtures was assessed by determining the ratios of embodied carbon. The results demonstrate that the inclusion of 0.60% CF and 26.5 kg/m3 of micro silica in the concrete mixture yields the optimal proportion, leading to a significant enhancement in compressive strength (CS), split tensile strength (STS), and flexural strength (FS) by 54.11%, 80%, and 36.6%, respectively, compared to a control sample devoid of CF and micro silica. Through thorough experimentation, a response surface methodology (RSM) was employed to develop an optimized model. Consequently, the derived equations enable the calculation of the impact of adding carbon fiber to concrete.

Effect of Natural Pozzolana on Physical and Mechanical Properties of Concrete

Construction industries are rapidly growing, sacking high amounts of concrete which has a highly dense microstructure with excellent mechanical properties, more durable, and highly eco-friendly materials. Hence, many of the researchers are interested in solving this problem with replacing concrete by natural pozzolana (NP) which is a supplementary cementitious material mostly from volcanic sources having much active silica content that can improve the durability and mechanical properties of concrete. However, it is not well-known which common optimum replacement range can give the most desirable concrete properties. So, the present study sought to review the effects of replacing NP from volcanic sources on the durability, physical, mechanical, and microstructural properties of concrete, also, to identify the most common dose of a positive effect as a replacement in concrete. The review shows that many of NP used by different literature from different places satisfy ASTM replacement standard in concrete, especially, based on its chemical compositions. Also, the review observed that employing NP in concrete significantly improves concrete workability, lengthens setting time, and reduces bulk density, porosity, water absorption, and chloride ion migration by making denser concrete microstructure. In general, adding 5%–20% of NP in concrete significantly improves compressive strength, split tensile strength, and flexural strength. Specifically, most of the studies found 15% replacement of NP having volcanic sources can give optimum strength. Besides these, most of the studies indicated that the improvement of the strength was more visible at the concrete age of 7–28 days.

Effect of superplasticizer in geopolymer and alkali-activated cement mortar/concrete: A review

Abstract The cement and construction industry creates around 10% of the global carbon footprint. Geopolymer and alkali-activated concrete provide a sustainable solution to conventional concrete. Due to its disadvantages, the practical usage of geopolymer and alkali-activated concrete is limited. Workability is one of the issues faced in developing geopolymer and alkali-activated concretes. Plenty of research was conducted to provide a solution to enhance the ability to use different superplasticizers (SPs). The present article extensively reviews the effects of SPs on geopolymer and alkali-activated concretes. The research articles published in the last 5 years in high-quality journals are considered for the chemical composition of the different SPs and analyses of their exact impact on geopolymer and alkali-activated cement mortar and concrete. Later, the impact of SPs on the normal consistency and setting times of cement mortar, workability, compressive strength, flexural strength, split tensile strength, microstructure, and water absorption of geopolymer and alkali-activated concrete was determined. SPs improve the geopolymer and alkali-activated concretes upon their use in desired dosages; more dosage leads to negative effects. Therefore, selecting the optimal superplasticizer is essential since it impacts the performance of the geopolymer and alkali-activated concrete.

Numerical Analysis of Hybrid Fibre-Reinforced Concrete Beam-Column Joint

Beam-column joint is the most vulnerable location of a moment-resisting reinforced concrete frame structure. The joint region experiences the maximum shear stress both in vertically and horizontally which is generated due to the shear transfer mechanism from the adjoining beams and columns. The shear capacity and bond stress capacity are the two major factors affecting the strength of a joint core in RC structure. An important discovery recently is the ductile behaviour of the whole structure under repeated loading. The behaviour of the concrete beyond elastic limit which is in the concrete hardening zone can drastically influence the ductility of the concrete. The non-linear stress-strain behaviour after the onset of the initial crack and up to ultimate compressive strength plays an important role in improving ductility. Beyond the ultimate compressive strength, concrete will undergo softening which is neglected in this study as once concrete reaches ultimate stress it is unsafe for service. This material ductility can be fulfilled with the application of high-strength fibres with ductile behaviour. However, the hybridization of two or more fibres can incorporate two different characteristics of the fibre used. The use of ordinary-grade of concrete moreover reduces the shear-resisting capacity of the joint. A hybrid mix of hooked-end steel fibre with basalt fibre and crimpled steel fibre with polypropylene fibre are used with a volume fraction of 1% to 1.4% of the concrete. In this study, ordinary M25 grade concrete and fibre mixed M25 grade concrete is employed under static and cyclic loading. The laboratory tests are also conducted to evaluate the compressive strength, split-tensile strength, and flexural strength of the hybrid mix fibre-reinforced concrete at the age of 28th days. Five full-scale models of the beam-column joint are designed as per the Bureau of Indian Standards. Numerical models of concrete and steel reinforcement are developed. Numerical analysis is carried out using finite element software ANSYS-v21. The behaviours of the beam-column joint are observed under static as well as cyclic loading. Crack patterns, first crack load, initial displacement, ultimate load, and ultimate displacement are observed under static conditions. And under cyclic loading, hysteresis load vs displacement, energy dissipation, and stiffness degradation are observed. The hybridization of hooked steel with basalt fibre gives better results in mechanical strengths and the hybrid effect of crimpled steel with polypropylene fibre gives better results in mechanical strengths. And also under numerical study, the above specimens show an improvement in energy dissipation capacity. Keywords beam-column joint, hybrid fibre reinforced concrete, numerical concrete model, ANSYS, static, reverse cyclic, energy dissipation, stiffness, crack

Development of ultra-lightweight foamed concrete modified with silicon dioxide (SiO2) nanoparticles: Appraisal of transport, mechanical, thermal, and microstructural properties

Over the last few decades, researchers have devoted significant consideration to the use of nanoscale elements in concrete. Silicon dioxide nanoparticles (SDNs) have been a popular subject of study among the several types of nanoparticles. This article describes the findings of a laboratory investigation that examined the properties of ultra-lightweight foamed concrete (ULFC) including different proportions of SDNs. Wide range of the properties was evaluated specifically the slump flow, density, consistency, flexural strength, modulus of elasticity, compressive strength, split tensile strength, thermal properties, porosity, water absorption, sorptivity, intrinsic air permeability, and chloride diffusion. Additionally, the scanning electron microscopy (SEM) and pore distributions analyses of different mixes were done. Results confirmed a noticeable increase in the mechanical properties of ULFC, with respective improvements in the 28-day compressive, split tensile, and flexural strengths of up to 70.49%, 76.19%, and 51.51%, respectively, at 1.5% of the SDNs inclusion. However, further increases in the SDNs percentage did not result in remarkable enhancements. As the SDN percentage increased from 1.5% to 2.5%, the ULFC's sorptivity, porosity, water absorption, intrinsic air permeability, and chloride diffusion showed substantial improvements. When compared to the control sample, ULFC with SDNs demonstrated higher thermal conductivity values. The reason for this occurrence was determined to be the smaller pore size observed in the ULFC specimens containing SDNs. A great adjustment in the distribution of pore diameters was witnessed in the ULFC mixes when the percentages of SDNs were adjusted. The ULFC specimens, which included SDNs at the percentages of 0.5%, 1.0%, and 1.5%, indicated a reduction in the total number of large voids measuring 500 nm or more, compared to the control ULFC specimen. The findings of this study highlight the potential benefits of incorporating SDNs into ULFC, which may improve its overall properties.

Characterizing the behavior of blended concrete incorporating metakaolin and quarry dust: an experimental investigation

Purpose This study aims to characterize the behavior of blended concrete, including metakaolin (MK) and quarry dust (QD), as supplementary cementing materials. The study focuses on evaluating the effects of these materials on the fresh and hardened properties of concrete. Design/methodology/approach MK, a pozzolanic material, and QD, a fine aggregate by-product, are potentially sustainable alternatives for enhancing concrete performance and reducing environmental impact. The addition of different percentages of MK enhances the pozzolanic reaction, resulting in improved strength development. Furthermore, the optimum dosage of MK, mixed with QD, and mechanical properties like compressive, flexural and split tensile strength of concrete were evaluated to investigate the synergetic effect of MK and quarry dust for M20-grade concrete. Findings The results reveal the influence of metakaolin and QD on the overall performance of blended concrete. Cost analysis showed that the optimum mix can reduce the 7%–8% overall cost of the materials for M20-grade concrete. Energy analysis showed that the optimum mix can reduce 7%–8% energy consumption. Originality/value The effective utilization is determined with the help of the analytical hierarchy process method to find an optimal solution among the selected criteria. According to the AHP analysis, the optimum content of MK and quarry dust is 12% and 16%, respectively, performing best among all other trial mixes.

Effect of mixed basalt fibers and nano-silica on mechanical properties and microstructure of recycled aggregate concrete

In this study, basalt fibers (BFs) and nano-silica (NS) were innovatively combined to reinforce recycled aggregate concrete (RAC) to prepare recycled aggregate concrete (named NBRAC) with better mechanical and microstructural properties as an alternative to ordinary concrete. Different NBRAC specimens were prepared by adjusting the contents of NS and BF; the damage mechanism and mechanical properties of NBRAC were investigated; and the compressive, split tensile, and flexural strengths of NBRAC were evaluated. The microstructure of NBRAC was analyzed by scanning electron microscopy observation. The results showed that the densification of NBRAC was improved under the condition of 50% RA substitution rate and that its compressive, split tensile, and flexural strengths were increased by 6.8%, 16.3%, and 32.7%, respectively, compared with that of natural concrete, which proved that the method was feasible for the preparation of high-performance RAC. Scanning electron microscope image analysis confirmed the improvement effects of NS and BF on RAC, and combined with the experimental data, a composite explanation for the improvement effects of NS and BF on RAC was proposed for the first time.

Review on Application of Lightweight Cenosphere in Construction Material

AbstractThere are many industrial waste products used in the construction industry like rice husk ash, fly ash phosphogypsum, marble powder, cenosphere, silica fume, copper slag, granulated blast furnace slag, etc. It is observed that the use of all waste materials is beneficial for improving the properties of cement concrete and also making a hunk of lightweight cement concrete. In that material, the cenosphere is the most economical material in the construction industry, so both waste materials are used in most of the experimental works. This review focuses on the concrete prepared by replacing cement and fine aggregate with the cenosphere at various percentages for the preparation of lightweight cement concrete. The usual way to use cenosphere is up to 30% replacement as fine aggregate or 20% replacement of cement gives good results. These reviews discuss the usability and extraction of cenosphere from fly ash, its properties, and applications. Also observed are the final optimum percentages for compressive strength, split tensile strength, and flexural strength for 7, 14, and 28 days.

Enhanced fresh and hardened properties of foamed concrete modified with nano-silica

Nowadays, the application of nanotechnology has gained increased attention in the concrete technology field. Several applications of concrete require light weight; one such concrete used is foamed concrete (FC), which has more voids in the microstructure. In this study, nano-silica (NS) was utilized, which exhibits a pozzolanic nature, and it reacts with other pozzolanic compositions (like lime, alumina, etc.) to form hydrated compounds in concrete. Apart from these hydrated compounds, NS acts as a filler material and enhances properties of concrete such as the fresh and hardened properties. This research examines the fresh, hardened, and microstructural properties of FC blended with NS. The ratio of binder and filler used in this research is 1:1.5, with a water-to-binder ratio of 0.45 and a density of 880 kg/m3. A total of six different weight fractions of NS were added to FC mixes, namely 0%, 1%, 2%, 3%, 4%, and 5%. Properties assessed for FC blended with NS were the slump, bulk density, strength parameters (flexural, splitting tensile, and compressive strengths), morphological analysis, water absorption, and porosity. It was concluded from this study that the optimum NS utilized to improve the properties was 3%. Apart from this, the relationship between the mechanical properties and NS dosages was developed. The correlations between the compressive strength and other properties were analyzed, and relationships were developed based on the best statistical approach. This study helps academicians, researchers, and industrialists enhance the properties of FC blended with NS and their relationships to predict concrete properties from other properties.

Dynamic Splitting Tensile Strength of Precast Concrete Samples with Varying Moisture Contents

Dynamic Splitting Tensile Strength of Precast Concrete Samples with Varying Moisture Contents

Revolutionizing Construction - Harnessing the Power of Brick Kiln Dust as a Sustainable Cement Alternative

Abstract: The concrete industry stands as the preeminent colossus within the realm of industrial domains. The building and construction industry, a primary contributor to environmental issues, is constantly seeking innovative approaches to enhance sustainability. Bricks forming the building block of the building structures are being manufactured worldwide. A substantial volume of fine particle dust is produced during the production step in the form of leftovers. This dust is the by-product of firing clay bricks at high temperature and the residual ash of the induced fuel. Brick Kiln dust poses environmental challenge due to disposal complexities. Commonly, the only established method of disposal is through land-filling, which can contribute to environmental concerns. This experimental investigation explores the transformative potential of utilizing Brick Kiln Dust as sustainable alternative to convention cement. BKD, obtained from a kiln situated in District Budgam, Jammu and Kashmir, was incorporated into concrete mixes at varying proportions (5%, 10%, 15%, 20%, and 25%) as a replacement for cement. Through the use of rigorous testing on mix samples, this study examined the effect of BKD on concrete workability as well as compressive and split tensile strength. The results were compared to identify the optimal dosage for achieving a balance between reduced cement consumption and maintaining structural integrity. The results showed that adding BKD not only significantly decreased the amount of cement used, but also demonstrated that it was a workable and sustainable substitute. This research not only addresses the environmental concern associated with BKD but also contributes to the ongoing efforts to develop sustainable construction practices.

A Comparative Study Investigating the Feasibility and Potential of Utilising Polymer, Demolition & Glass Waste as a Partial Replacement for Fine and Coarse Aggregate in Concrete

The construction industry is a key CO2 contributor. Contemporary research focuses on formulating cement replacement composites; however, less attention is deliberated to formulating fine/coarse aggregate replacement composites. The waste from different fields contributes enormously to adverse environmental effects, thus necessitating reuse/recycling. The demolition/reconstruction of old buildings/infrastructure is adding further to the waste contribution by the construction industry. The total quantum of fine/coarse aggregate in the construction industry is estimated to be around 20 billion tons, contributing around a billion tons of CO2 . Therefore, even partial replacement of virgin sand/coarse aggregates with various waste materials like glass, rubber, plastic, tyres, recycled concrete and others will economise the cost of manufacturing the concrete with reduced CO2 footprints as eco-friendly materials. This study conducted a comparative analysis for investigation of the characteristic compressive and split tensile strength of concrete composites with partial replacement of virgin sand/coarse aggregate by 10-30% of Crushed Glass (CG), Crumb Rubber (CR), Recycled PET Bottles (RPB), Recycled Concrete Aggregate (RCA) and 5-10% of Shredded Tyres (ST). Generally, all the composites demonstrated par/ better strength with the control mix, achieving the target strength of C55/67 concrete. The composites with CG, RPB and RCA exhibited an improvement in compressive strength, attaining more than 70 MPa (high-performance concrete strength) and up to 10% improvement in split tensile, attaining 4.3 MPa. CR and 5-10% ST exhibited a slight decrease in compressive strengths. All the composites formulated in this study explicate their diverse uses for multipurpose infrastructural applications in the construction industry as improved, economical, eco-friendly waste absorbent composites.

Mechanical and environmental evaluation of PET plastic-graphene nano platelets concrete mixes for sustainable construction

In recent times, there has been a substantial increase in the annual use of plastics, resulting in a major upward trend. As a result, recycling plastic waste has become a major global issue. The present research aims to explore the feasibility of utilizing Polyethylene terephthalate (PET) as a possible substitute for coarse aggregate in concrete. In addition, the integration of Graphene Nano-platelets (GNPs) into the concrete mixture was conducted using different quantities, aiming to improve its structural integrity. The study employed an experimental research design to carry out its examination. PET was included into concrete at varied ratios, namely 0 %, 5 %, 15 %, 20 %, and 25 %, serving as an additional ingredient alongside coarse aggregate. Additionally, GNPs were introduced into the mixture at various weight percentages, namely 0 %, 0.03 %, 0.05 %, 0.08 %, and 0.1 %. A series of mechanical tests were performed to evaluate various properties of the concrete, including compressive strength (CS), split tensile strength (STS), flexural strength (FS), modulus of elasticity (MoE), ultrasonic pulse velocity (UPV). In addition, an assessment of the concrete's environmental impact was conducted by analysing the carbon content and evaluating its eco-efficiency (ESE). The research study revealed that the incorporation of 5 % PET as a replacement for coarse aggregate, together with the inclusion of 0.1 % GNPs, resulted in the optimal enhancement of CS, STS, FS, MOE, UPV by 9 %, 12.21 %, 4.40 %, 4.40 % and 0.070 % respectively. The Response Surface Methodology (RSM) models were developed, and mathematical equations were generated in order to predict the expected results. The optimization process for all the models was carried out using a multi-objective optimization technique, followed by a subsequent validation process.

Surface treatment with nano-silica and magnesium potassium phosphate cement co-action for enhancing recycled aggregate concrete

Abstract In this study, surface treatment, using blended materials of nano-silica (NS) and magnesium potassium phosphate cement (MKPC) slurries containing four dosages of NS, was applied to recycled aggregate (RA) with distinct RA maintenance schemes to enhance the RA concrete (RAC) performance and control NS dosage for economy. The results imply that the NS + MKPC slurry can efficiently bolster the bonding with RA and the new interfacial transition zone (ITZ), contributing to a distinct enhancement of RAC’s macro-properties. Besides, the optimal NS dosage and RA maintenance scheme revealed by the simplified linear weighted sum optimization method were 3% and no pre-curing procedure, respectively. On the basis of the aforementioned optimal conditions, the modified RAC (C-3-N) achieved enhanced compressive strength by 40.75%, split tensile strength by 46.26%, and chloride ion penetration resistance by 65.93% in comparison with the untreated RAC0. Moreover, the advantages observed in C-3-N were attributed to the exceptional microstructural characteristics in both the NS + MKPC slurry and the new ITZ. This study establishes the potential to augment the efficacy of nanomaterials in reinforcing RAC and enhance the economic viability and practicability of RAC applications. Simultaneously, these advancements contribute to fostering sustainable development within the construction industry and yielding environmental benefits.

Deterioration of interfacial bonding performance between metal mortar and concrete under the coupling effect of freeze-thaw cycle and abrasion

In cold regions, hydraulic concrete structures are often severely damaged by the combined effects of freeze-thaw cycle and hydraulic abrasion, and it is critical for safe operation of the structure to repair the damage. The actions of freeze-thaw cycles (0, 25, 50, 75, 100, 125, and 150 cycles), abrasion (24, 48, 72, 96, 120, and 144 h), and the coupled action of freeze-thaw cycles and abrasion on the metal mortar-concrete interface were investigated. The apparent damage, mass loss, abrasion resistance, and interfacial splitting tensile and shear strengths of metal mortar-concrete are discussed. The changes in the bond properties of metal mortar-concrete interface were also investigated from a microscopic point of view. The results showed that the alternating action of freeze-thaw cycles and abrasion resulted in more apparent damage and mass loss, and the coupling damage became more pronounced as the number of alternations increased. The interfacial bond strength was reduced by 33.7 %–50.06 % under a single freeze-thaw or abrasion action. And interfacial bond strength decreases by 54.94 %–66.33 % under coupled freeze-thaw and abrasion. The interfacial splitting tensile and shear strengths have a good linear relationship under various actions (the correlation coefficients are higher than 0.97). The microscopic tests showed that the maximum width of the interface under the coupled action of freeze-thaw cycles and abrasion reaches 80–110 μm, which is significantly higher than the single action (30–45 μm).