Interfacial Transition Zone Research Articles

Understanding the role of natural pozzolana in regulating the early hydration reaction process and microstructure of Portland cement

The present study examines the regulatory role of natural pozzolana (NP) on the early-age hydration process and microstructural development of Portland cement. Through a series of experiments, including low-field nuclear magnetic resonance (NMR), X-ray diffraction (XRD), thermogravimetric (TG) analysis and scanning electron microscopy (SEM), it was found that NP significantly influences the hydration kinetics and chemical shrinkage of cement paste. The addition of NP was shown to reduce the early-age chemical shrinkage and refine the microstructure by decreasing the quantity of harmful pores and increasing harmless pores, as evidenced by the bimodal distribution observed in pore size distribution (PSD) analysis. XRD and TG results indicate that NP reacts with calcium hydroxide to form additional calcium silicate hydrate (C-S-H) gel, thus improving the interfacial transition zone and resistance to carbonation. SEM micrographs further confirm the improved microstructure with fewer microcracks. The findings suggest that NP can be effectively utilized to optimize the early-age performance of concrete, offering a sustainable approach to improving its durability and long-term structural integrity.

Influence of geometric shape, pore structure and surface modification of recycled fine aggregate on the rheology behaviour and strength development of mortar

The complex physical properties of recycled fine aggregate affect the rheological and mechanical properties of mortar, thereby limiting its application in cement-based materials. This paper evaluated the geometric shape and pore structure of natural fine aggregate (NFA), recycled fine aggregate (RFA), and recycled fine aggregate modified by water glass (MRFA), and studied its water absorption and bulk density. The influence of complex physical properties of RFA before and after modification on the rheological behavior, strength development, and microscopic properties of mortar was analyzed. The rheological tests were carried out on the fresh mortar with 7 mixes, and the compressive strength and flexural strength of hardened mortar after curing for 3, 7 and 28 days were tested. The results shown that the modification of water glass has improved the water absorption and geometric shape of RFA to some extent, resulting in a small increase in the apparent viscosity and yield stress of recycled mortar compared to NFA mortar. When the replacement level of RFA was less than 30 %, the compressive strength of recycled mortar was 13 % higher than that of NFA mortar. As the replacement level increased to 40 %, the incorporation of water glass also helped to improve the mortar strength. The irregular geometric shape and high water absorption of RFA were conducive to achieving dense mechanical bonding and reducing the Ca/Si ratio in the interface transition zone.

Regulating sulfur migration and transformation in low water-binder ratio cementitious system incorporating phosphogypsum aggregate: Environmentally friendly clean materials

The paper aims to clarify the regulation mechanism of sulfur migration and transformation in a low water-binder ratio system incorporating phosphogypsum aggregate (LWC-PG). Firstly, the combination of S-containing adhesive material and phosphate gypsum aggregate can reduce the migration of sulfate ions (SO42−) in the phosphate gypsum aggregate. The reaction mechanism and macro and micro properties of LWC-PG are characterized by universal testing machine, low field nuclear magnetic field, isothermal calorimeter, XRD diffractometer, scanning electron microscope and nano-indentation. The results show that the calcium sulfoaluminate cementitious system (CSA) is compatible with PG. The results show that CSA is compatible with PG, and the 28d strength of 80 % phosphogypsum is 83.4 MPa, which can maintain the required strength for high-performance concrete. Secondly, the sulfides in PG react with C4A6S in CSA, resulting in the formation of ettringite that coats the surface of the C–S–H gel, thereby retarding the hydration rate of the slurry. However, due to the presence of phosphate gypsum aggregate, the reaction continues, enhancing the hydration of sulfate cement. Moreover, the interfacial transition zone between the PG and matrix exhibits a strong bond and shows no significant signs of deterioration. Lastly, when using 80 % phosphogypsum aggregate instead of natural sand and gravel to produce 100 m3 of concrete, 42 t of phosphogypsum aggregate can be used, which reduces the consumption of natural sand and gravel by 61.4 t, decreases energy consumption by 3070 MJ, reduces CO2 emissions by 178.06 kg, SO2 emissions by 0.37 kg, NOX emissions by 0.25 kg, and dust emissions by 0.087 kg. Life cycle evaluation demonstrates that the production of LWC-PG is associated with low carbon emissions and environmental friendliness, which significantly reduces environmental burden. This is of significant research importance for solid waste management and energy-saving and carbon reduction efforts.

Mesoscopic simulation of uniaxial compression fracture of concrete via the nonlocal macro–meso-scale consistent damage model

To capture the uniaxial compression fracture of concrete composite is still a great challenging problem. To this end, the newly proposed nonlocal macro–meso-scale consistent damage (NMMD) model is extended to simulate uniaxial compression fracture of concrete composites. In the NMMD model, a mesoscopic structure composed of material point pairs is attached to each material point. A decomposition scheme suitable for masonry-like materials is adopted to decompose the elongation quantity of point pairs. The topologic damage is defined as the weighted summation of mesoscopic damage in neighboring material point pairs driven by the decomposed elongation quantity. The physically-based energetic degradation function is employed to bridge the geometric discontinuity in solids and the energy dissipation, and thus the topologic damage is integrated into the framework of continuum damage mechanics. The Monte-Carlo method and two-phase random field model are employed to generate stochastic circular and irregular aggregates representing the meso structure of concrete, respectively. The interface transition zone is prescribed by reducing the critical value of interface point pairs. Numerical results indicate that both the crack patterns and stress–strain curves of the uniaxial compression experiments on concrete panels can be well captured by the proposed NMMD model without mesh size sensitivity. The influence of horizontal constraints on the top and bottom surfaces is investigated and shown to have an effect on the crack patterns, strength and deformation capability of the specimen. The necessity of decomposition is also illustrated.

The Influence of Slag Content on the Structure and Properties of the Interfacial Transition Zone of Ceramisite Lightweight Aggregate Concrete.

Ceramisite lightweight concrete has excellent performance and relatively light self-weight characteristics. At the same time, the recent development of green high-performance concrete and prefabricated components has also brought the abundant utilization of these mineral mixture. An interfacial transition zone exists between the hardened cement paste and the aggregate, which is the weakest part of the concrete, characterized by high porosity and low strength. In order to study the effect of slag content on the interfacial transition zone in lightweight high-strength concrete, experiments were designed to replace cement with slag at different contents (0%, 5%, 10%, 15%). A series of studies was conducted on its macro-strength, microstructure, and composition. The results indicated that the addition of slag improved the porosity and width of the interfacial transition zone. Adding slag did not reduce the thickness of the concrete interfacial transition zone significantly at 3 d, but it led to significant improvement in the thickness of the interfacial transition zone at 28 d, and the thickness of the interfacial zone at 28 d was reduced from 19 μm to 8.5 μm, a reduction of 55%. The minimum value of microhardness in the slurry region of the interfacial specimens also increased from 19 MPa to 26 MPa, an increase of 36%. In addition, the structural density of the interfacial region was further increased, resulting in varying degrees of improvement in the macroscopic anti-splitting strength. One of the important reasons for this phenomenon is that the addition of slag optimizes the chemical composition of the interface and promotes the continuation of the pozzolanic reactivity, which further enhances the hydration at the interface edge.

Ultra-high performance concrete with metal mine tailings and its properties: a review

Abstract Metal mine tailings (MMT) are a kind of industrial solid waste, with an increasing accumulation year by year, which has seriously damaged the ecological environment. Incorporating MMT in ultra-high performance concrete (UHPC) is an effective means to achieve green sustainable development, which can not only make wastes be resources and prevent pollution but also save raw material costs and reduce energy consumption. However, metal mine tailings contain complex and diverse metal oxides and other chemical substance and even contain certain radioactive elements and heavy metal ions. These factors can affect the corrosion resistance of UHPC, accelerate its aging and damage, and in addition may have serious impacts on the environment and human health. This paper summarizes the material properties of MMT and its application in UHPC; analyzes the effects of MMT as powder or fine aggregate on the workability, mechanical properties, durability, and leaching toxicity of UHPC; and elaborates the hydration products, interfacial transition zone, and pore structure of UHPC incorporating MMT (MMT-UHPC). Based on previous research results, the relationship between flowability, flexural strength, porosity, and compressive strength of MMT-UHPC is established.

Effect of Micro-Cracks on Chloride Ion Diffusion in Concrete Based on Stochastic Aggregate Approach

For concrete structures in offshore areas, chloride ion erosion is one of the main factors affecting durability. It is crucial to evaluate the chloride ion permeability resistance of concrete structures. In this paper, a finite element simulation of the chloride ion diffusion process in concrete is conducted. A mass diffusion finite element model based on a random aggregate approach is established to investigate the influences of an aggregate, the interface transition zone, and micro-cracks on the chloride ion diffusion coefficients in concrete. The results show that the mass diffusion finite element analysis based on the exponential function model and the power function model can effectively simulate the chloride ion diffusion process in concrete. In addition, the data reveal that volume fraction and distribution aggregates considerably affect chloride ion diffusivity in concrete. Also, the interface transition zone significantly accelerates chloride ion diffusion in concrete. Moreover, this acceleration effect exceeds the barrier effect of an aggregate.

Macroscopic properties and microscopic characterisation of an optimally designed anti-cracking stone base course filled with cement stabilised macadam

Stone base course filled with cement stabilised macadam (SFC) is a promising solution for addressing reflection cracks in semi-rigid base asphalt pavement due to its satisfactory crack resistance. However, its limited strength and construction challenges have impeded its widespread application. To overcome these challenges, an optimised mix proportion design method of SFC was proposed. Natural crushed limestones with specific particle sizes were selected to serve as skeletal coarse aggregates; fine aggregates and their proportions were step-by-step determined using aggregate and unconfined compressive strength tests. The multi-scale analysis integrating the performance tests and the microscopic detections was performed to evaluate the effectiveness of the proposed SFC, and compared with common cement stabilised macadam (CSM). The results indicate that the material exhibits satisfactory mechanical strength through a tightly interlocked skeleton structure and excellent crack resistance by dissipating strain energy and retarding cracking of SFC through the weak interface transition zone (ITZ).

Eco-friendly, high-toughness gypsum prepared using hemihydrate phosphogypsum, fly ash, and glass fibers: Characterization and environmental impacts

Hemihydrate phosphogypsum (HPG), obtained as a cementitious material from the dewatering of phosphogypsum, can be widely used in the preparation of construction materials owing to its low cost and environmental friendliness. However, current reports on HPG mainly focus on hydration behavior, mechanical properties, and durability, and there are few studies focusing on the enhancement of HPG toughness. In this work, glass fibers (GF) and fly ash (FA), as composite reinforcement, were mixed with HPG during its preparation to obtain eco-friendly, high-toughness gypsum. The workability, mechanical, microstructural, financial and environmental properties of the HPG-based composites with different GF volume dosages (0, 0.5, 1.0, and 1.5 vol%) and FA weight percentages (0, 10, 20, and 30 wt%) were comparatively investigated. The results show that the addition of an appropriate amount of FA can improve the interface transition zone between GF and the matrix and effectively increase the flexural strength and toughness of the composites. For the optimal mixture containing 1.5 vol% GF and 20 wt% FA, the flexural strength and toughness were 50.7% and 82.2% higher, respectively, than those of the mixture without FA and 99.2% and 675.3% higher, respectively, than those of the control sample (without GF and FA). Cost-benefit and environmental impact analyses also indicated that this composite was the most economical and environmentally friendly. Thus, this work provides an effective approach to achieve the high-value utilization of two major industrial by-products.

Effects of medium-burnt quicklime on autogenous shrinkage of ultra-high performance concrete cured at room temperature

Ultra-High Performance Concrete (UHPC), with its excellent tensile properties, can be used as an alternative to decorative materials that are heavy in cross-section, enabling architectural decoration field to develop in the direction of light weight and changeable shape. However, the extremely low water-binder ratio of UHPC produces obvious autogenous shrinkage, which leads to the development of many micro-cracks. When the micro-cracks develop to a certain extent, they can have a very negative impact on the finishing of the architecture. This paper studies the influence of medium-burnt quicklime dosing on the hydration process and mechanical properties of UHPC cured at room temperature and elucidates the mechanism by which medium-burnt quicklime reduces autogenous shrinkage in UHPC. The results show that the crystal growth pressure generated by the hydration of f-CaO (free calcium oxide) can significantly compensate the autogenous shrinkage of UHPC. The dosage of 3 % medium-burnt quicklime can make the mechanical properties and shrinkage properties of UHPC reach the relative optimum, and the autogenous shrinkage of UHPC can be reduced to 181.36 με. Although the medium-burnt quicklime reduces the hydration products by delaying the hydration of UHPC, it also can reduce the porosity and the percentage of the multi-harmful pores, and refine the pore aperture. In addition, the interfacial transition zone between the UHPC matrix and the steel fibres can be reduced due to the extrusion of Ca(OH)2 crystal growth pressure on the surrounding crystals, resulting in a tighter lapping between the crystals.

Preparation and performance research of ecological concrete using waste wood

To mitigate environmental damage from mineral aggregate extraction, bio-based materials have garnered research interest as potential replacements for natural mineral aggregates. This work utilized waste wood as filler to prepare lightweight foam concrete with thermal insulation, low-temperature and corrosion resistance properties. The feasibility of using wood aggregate-based foam concrete (WFC) was explored in terms of dry density, softening coefficient, compressive strength, thermal conductivity, chloride ion permeability, freezing resistance, and sulfate attack resistance. Results showed that simultaneous addition of waste wood aggregate (WA) and foam effectively reduced WFC bulk weight and thermal conductivity while enhancing water resistance. However, the porous morphology of WA and foam caused the reduction of mechanical properties. In terms of durability, the addition of WA can increase the energy absorption capacity when WFC is subjected to expansion stress, reduce the damage to the structure, and have an inhibiting effect on the cracking of WFC caused by sulfate attack and freeze-thaw cycles. Nevertheless, WA's high water absorption loosened the matrix in WFC's interfacial transition zone (ITZ), increasing harmful pores and negatively affecting durability. In addition, in order to predict the mechanical properties of WFC and the resistance to sulfate attack, this study established a function model for the relationship between the compressive strength (Maintenance specimens of the same age and Specimen of sulfate attack) and the WA dosage. In conclusion, The use of waste wood for the preparation of WFC is more advantageous and sustainable than conventional foam concrete for the insulation of precast walls and coastal structures.

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.

A bibliometric review on research progress, interest evolution and future trend in the field of recycled concrete by using CiteSpace (2004–2023)

The popularization of recycled concrete (RC) is an important way to achieve efficient resource utilization of construction solid waste (CSW), which can coordinate the sustainable economic development with environmental protection. In this paper, CiteSpace software is used to quantitatively analyze the literatures on RC field, identifying its research hotspots and recent developments. Based on the Web of Science database, we screened published literatures in the field of RC from 2004 to 2023, and obtained 2011 articles. CiteSpace software and knowledge graph technology are adopted to visually analyze the literature information, including the collaborators, keywords and citation status. The results show that, Xiao JZ from Tongji University, Poon CS from Hong Kong Polytechnic University and Tam VWY from University of Western Sydney publish a large number of articles and are frequently cited. It indicates that their researches are widely recognized in academic circles. There is a research team with a large size formed in the Chinese mainland, and the core members include Xiao JZ, Li WG, Chen ZP. At present, the research interest gradually shifts from recycled coarse aggregate to recycled fine aggregate, mainly focusing on microscale research of pore structure and interfacial transition zone. In addition, 8 co-citation clusters of selected references and the potential development trends are detailly analyzed. This study is helpful for researchers to fully understand the current hotspots and future research trends in the field of RC.

Flexural fatigue performance of recycled sand concrete for high-speed railway track bed

To investigate the applicability of recycled sand concrete in high-speed railway ballastless track bed, in this study, the fatigue life, strain evolution curve and calculated stiffness of C40 concrete incorporating 0, 50 % and 100 % recycled sand were explored. Digital image correlation (DIC) and the nanoindentation test were used to explore the influence of recycled sand on the performance of concrete. The results show that the flexural fatigue life of recycled sand concrete conforms to a two-parameter Weibull distribution. The fatigue strain progression and calculated stiffness demonstrate a distinct three-stage trend. Compared to natural aggregate concrete, the first-stage strain contribution of recycled sand concrete decreases by approximately 10 %. With the increase of fatigue cycles, the calculated stiffness decreased significantly, the dissipated energy increases gradually. Compared with recycled sand-free concrete and full recycled sand concrete, the concrete containing 50 % recycled sand possesses the highest elastic modulus and lowest thickness of the interfacial transition zone (ITZ), thus the average fatigue life of recycled sand concrete increased by 4.9 and 10.2 times.

Experimental study and multi-objective optimization of the shear mechanical properties of recycled aggregate concrete with hybrid fibers and nano SiO2

Structural imperfections (microcracks, micropores, and weak interfacial transition zones) impact the shear mechanical properties of recycled aggregate concrete (RAC). Fibers and nanoparticles can mitigate these issues, enhancing the overall quality of recycled aggregates (RAs). Various hybrid systems, including basalt fiber (BF), polypropylene fiber (PPF), and nano-SiO2 (NS), were added to the RAC for double shear testing. Regression models were developed using the response surface method to optimize the hybrid systems. The study showed that the NS-BF-PPF hybrid system achieved the optimal shear strength, shear strain, shear toughness index, and shear fracture energy (6.99 MPa, 9.58 × 10−4, 0.716, and 34.603 J, respectively). These values were superior to those of the BF-PPF hybrid system and single system. The three-dimensional reticulated supporting structure devised by the BF-PPF effectively remedied the structural defects in the RA at various levels. Furthermore, the fibers integrated into the hybrid system act as bridges, absorbing shear energy during the pullout process. The incorporation of nanoscale NS stimulated the hydration response of the cement, resulting in a more compact pore structure within the RAC. Nonlinear multivariate regression models were fabricated utilizing the response surface method to maximize strength. The optimal contents of BF and PFF in the BF-PPF hybrid system were 0.344 % and 0.3 %, respectively. The optimal contents of NS, BF, and PPF in the NS-BF-PPF hybrid system were determined to be 3.5 %, 0.5 %, and 0.1 %, respectively. The combination of fibers and nanoparticles elicits a synergistic effect, significantly augmenting the shear performance of RAC.

Study on the rheology, mechanical properties and microstructure of polypropylene fibers in different binder systems

To explore the effects of polypropylene fiber (PPF) on the properties of different binder materials, the effects of PPF on the rheology, shrinkage, mechanical properties and microstructure of alkali-activated mortar (AAM) and ordinary Portland cement mortar (PCM) were studied. The results showed that the addition of PPF reduced the fluidity of the mortar, and the lower the initial yield stress and plastic viscosity of the paste were, the more obvious the increase. PPF reduced the drying shrinkage of both the AAMs and PCMs by 7.63–12.85 %. The inclusion of PPF to the mortar had a limited effect on enhancing the mortar compressive and flexural strength, but it notably improved the mortar toughness. At a fiber content of 0.5 %, the samples from the cement and slag-steel slag systems exhibited a more compact of the interfacial transition zone (ITZ) between the fiber and paste. Conversely, the slag-steel slag-fly ash and slag-fly ash systems showed poorer compact of the ITZ, which was attributed to increased unreacted precursors and shrinkage cracks. This phenomenon primarily accounted for the superior residual stresses observed in the cement and slag-steel slag systems. This study provides an avenue for analysis the effect of the same fiber on different binder systems.

Potassium citrate-activated pure BOF slag-based mortars utilizing carbonated and autoclaved BOF slag aggregates

This study proposes novel basic oxygen furnace (BOF) slag mortars formulated with tri-potassium citrate (TPC) activated BOF slag as binder and treated BOF slag (carbonated (CB) and autoclaved (AB)) as aggregates, aiming to maximize the utilization of BOF slag in the construction industry. Untreated BOF slag (UB) and natural sand (NS) were employed as reference aggregates. The effects of carbonation and autoclaving were investigated, focusing on the interfacial transition zone (ITZ) properties through SEM-BSE greyscale thresholding and constituent segmentation analysis. Results indicate that both treatments reduce the free CaO, promote CaCO3 formation, and modify the aggregate surface. The 28 d compressive strength of pure BOF slag-based mortars with UB, CB, and AB aggregates are 25.8, 29.4, and 34.8 MPa (average at varying TPC dosages), significantly higher than that with NS (19.6 MPa). Pure BOF slag-based mortars also show narrower ITZ thicknesses and the absence of bond cracks. Mortars with CB and AB aggregates exhibit fewer unreacted particles and more hydration products within the integral binder region compared to those with UB. Overall, pure BOF slag-based mortars present a more robust aggregate/binder interface that is further enhanced by the aggregate treatments. Leaching values of all mortars are well below the Dutch legal limits. The findings suggest promising application prospects for pure BOF slag-based mortars in substituting cement mortars and valorizing BOF slag.

Physico-mechanical and thermal properties of vibrating and self-compacting sand concrete based on recycled aggregate from concrete

This study explores the use of recycled aggregates (RA) from concrete, replacing 100% of Cruched Sand (CS) by volume. It focuses on their processing methods and their performance compared to Self-Compacting Sand Concrete (SCSC) and Vibrated Concrete (VC). Fresh properties, including workability, are affected by RA, but RA-based SCSC meets standards. While RA-based SCSC initially had lower strength than CS-based SCSC, it improved after 28 days, yielding similar mechanical properties. RA use led to lower density compared to CS in concrete. Thermal conductivity was insulating, slightly lower in RA-based SCSC. Porosity decreased with age in all mixtures, with RA-based concrete having initial higher porosity and capillary absorption. Microstructure showed finer crystal growth in RA-based concrete. RA in SCSC exhibit a superior Interfacial Transition Zone (ITZ) compared to CS concrete, enhancing homogeneity and durability. This research supports sustainable RA use in concrete, that contingent on precise mix design and method processing of waste concretes, as well-designed SCSC. RA in construction provide scalable and economic benefits, including cost savings, infrastructure investment, sustainability, and market expansion. This contributes to the provision of environmentally friendly building materials and the sustainability of the industry.

ITZ volume fraction and thermal conductivity of concrete: A unified random packing model for gravels and crushed rocks

This work proposes a mesostructure-guided computational framework to evaluate the effective thermal conductivity (ETC) of concrete affected by aggregate and interfacial transition zone (ITZ) configurations at a mesoscopic scale. An unified aggregate shape descriptor for gravels and crushed rocks is characterized by superellipsoid covering from convexity to non-convexity, as well as random static and dynamic packings of superellipsoidal aggregates (SAs) are carried out to generate tri-phase concrete mesostructures consisting of homogeneous mortar, densely packed aggregates and their surrounding ITZs. A closed-form expression for the ITZ volume fraction is theoretically developed in the present concrete mesostructure, which is also validated using the one-point probability function simulation. Moreover, an optimized Browanian motion numerical strategy is developed to estimate the ETC of tri-phase concrete. This strategy is confirmed to be an accurate numerical technique by comparing against the Mori-Tanaka model. The present framework reveals the quantitative responses of various configurations on the ETC, which manifest rigorous “constituent-mesostructure-ETC” relations. The results are available for tailoring components to optimize ITZ structures for the improvement of thermal efficiency and durability of buildings.

Effect of nanosilica and fiber on mechanical properties and microstructure of recycled coarse aggregates road concrete

Recycled coarse aggregate has its own characteristics of large porosity, high water absorption and high crushing index, which adversely affects the mechanical strength and durability of recycled aggregate concrete. In this study, the mechanical properties, durability and microstructure of recycled aggregate concrete (RAC) modified with nano-SiO2 (NS) and fibres were investigated to prepare road RAC, using NS polypropylene fibres (PPF) and basalt fibres (BF) as test variables. Compared with RAC only incorporating NS, NS and fibre synergism can significantly enhance the mechanical properties of recycled concrete, compressive strength increased by 27–51 %, flexural strength increased by 12 %, and abrasion resistance increased by 25–72 %. The synergistic effect of NS and PPF significantly improves the frost resistance of recycled concrete. NS has a volcanic ash effect which can react with calcium hydroxide to produce a large number of C-S-H in the secondary hydration reaction, making the internal structure of the cement matrix denser. Interfacial transition zone microstructure is more compact, thus interfacial transition zone porosity is effectively reduced. The hydration products are attached to the fibre surface, which enhances the bonding ability between the fibers and matrix. Therefore, the fibres effectively inhibit the generation and development of internal micro-cracks. NS optimises the internal pore structure of recycled aggregate concrete and enhances the interfacial transition zone, and NS synergistically with PPF can improve the strength and durability of various mechanical properties of recycled concrete. The research results provide the scientific basis for the application of road RAC.