Cementitious Material Content Research Articles

Study on Static Mechanical Properties and Numerical Simulation of Coral Aggregate Seawater Shotcrete with Reasonable Mix Proportion

This study aims to explore the static mechanical characteristics of coral aggregate seawater shotcrete (CASS) using an appropriate mix proportion. The orthogonal experiments consisting of four-factor and three-level were conducted to explore an optimal mix proportion of CASS. On a macro-scale, quasi-static compression and splitting tests of CASS with optimal mix proportion at various curing ages employed a combination of acoustic emission (AE) and digital image correlation (DIC) techniques were carried out using an electro-hydraulic servo-controlled test machine. A comparative analysis of static mechanical properties at different curing ages was conducted between the CASS and ordinary aggregate seawater shotcrete (OASS). On a micro-scale, the numerical specimens based on particle flow code (PFC) were subjected to multi-level microcracks division for quantitive analysis of the failure mechanism of specimens. The results show that the optimal mix proportion of CASS consists of 700 kg/m3 of cementitious materials content, a water–binder ratio of 0.45, a sand ratio of 60%, and a dosage of 8% for the accelerator amount. The tensile failure is the primary failure mechanism under uniaxial compression and Brazilian splitting, and the specimens will be closer to the brittle material with increased curing age. The Brazilian splitting failure caused by the arc-shaped main crack initiates from the loading points and propagates along the loading line to the center. Compared with OASS, the CASS has an approximately equal early and low later strength mainly because of the minerals’ filling or unfilling effect on coral pores. The rate of increase in CASS is swifter during the initial strength phase and decelerates during the subsequent stages of strength development. The failure in CASS is experienced primarily within the cement mortar and bonding surface between the cement mortar and aggregate.

Design Method for Low-Carbon Fly Ash Concrete Considering Strength, Form Removal Time, and Carbonation Durability Life

Low-carbon fly ash concrete is one of the hottest research topics in the concrete industry. This study proposes a design method for low-carbon fly ash concrete that systematically considers strength, form removal time, and carbonation durability life. The basic steps of this method are as follows: First, based on the experimental results, the strength development formula of fly ash concrete using different mix ratios and different aging periods is obtained through regression. The adopted carbonation depth calculation formula can be used to consider the influence of the curing time and mix ratio on carbonation depth. Second, through the analysis of design cases, the dominant factors in the design of low-carbon fly ash concrete are clarified. For example, strength dominates, demolding time dominates, or carbonation durability dominates. If the concrete is removed from the formwork early, the carbonation resistance is very weak, and a large amount of cementitious material is required in order to meet the carbonation durability requirements. Appropriately extending the removal time of the concrete form can enhance the carbonation durability, reduce the content of cementitious materials, and achieve the goal of low-carbon design. In short, the method proposed in this study can be used as a general method for low-carbon fly ash concrete design, and this method can be extended for use in different countries and regions.

The improvement on calcium leaching resistance of high SCMs content cement in ammonium chloride solution using particle gradation technique

Particle gradations of Portland cement (PC), fly ash (FA), and blast furnace slag (BFS) were optimized to improve the calcium leaching resistance of blended cement with high contents (up to 70%)of supplementary cementitious materials (SCMs). The results showed that optimized blended cement showed refined initial pore volume distribution, reduced portlandite (CH) content, finer CH macrocrystals and enhanced stability of C-(A)-S-H gel. Consequently, it displayed exceptional calcium leaching resistance with reduced losses in mechanical performance, mass and pore degradation after calcium leaching. Blended cement with 30% PC (D50 = 14.46 μm), 30% FA (D50 = 10.94 μm), 20% BFS (D50 = 10.52 μm), 13% BFS (D50 = 5.31 μm) and 7% BFS (D50 = 4.71 μm), showing compressive strength retention rate of 79.05% and mass loss rate of 1.64%, was suggested as viable choice for calcium leaching resistant concrete.

Machine learning-driven innovations in green eco-environmental rubberized concrete design towards sustainability

This research investigates the state-of-the-art developments in environmentally sustainable rubberized concrete (RC) design, with a significant focus on its eco-friendly characteristics. Novel methodologies for enhancing RC composition are currently under investigation, and machine learning, specifically CatBoost, plays a pivotal role in facilitating this exploration. The model is employed on a dataset comprising 590 RC samples. Importantly, an impressive coefficient of determination value of 0.991 is attained while using CatBoost to predict the compressive strength (CS) of RC, highlighting its exceptional predictive accuracy. Visual representations of variable interactions are generated using Partial Dependence Plots (PDPs). This study further presents design optimization results and key insights, paving the way for the development of sustainable RC materials. In addition, Pareto optimal solutions are presented, prioritizing the maximization of rubber and cementitious replacement material content while simultaneously striving for optimal CS. This approach embodies the study’s dedication to achieving a balanced and sustainable outcome where environmental benefits are maximized without compromising material performance.

Early-age inhomogeneous deformation of 3D printed concrete: Characteristics and influences of superplasticizer and water-binder ratio

3D printed concrete (3DPC) commonly experiences significant shrinkage along the printing direction (x-direction) at the early-age for its high cementitious material content, low water-binder ratio and formwork-free manufacturing process. This shrinkage with gradient along the vertical direction (z-direction) can cause interlayer slippage and further deformation within each filament. To investigate these early-age deformations and their dependence on materials, digital image correlation (DIC) was used to monitor the inhomogeneous deformation of 3DPC at the age of 0.5–6.5 h. It was found x-direction inhomogeneous shrinkage pattern is correlated with early-age hydration process and elastic modulus. After conducting mechanic analysis, it was found that an individual filament could be treated as a Winkler foundation beam with frictional moment, which can provide a semi-quantitative explanation of the phenomenon that the bottom filament shows significant downward deflection, while other layers show minimal upward deflection or almost no deflection. Additionally, the influence of superplasticizer and water-binder ratio on early-age inhomogeneous deformation was monitored. There exists an optimal dosage range for superplasticizer that ensures both better printing quality and lower x-direction shrinkage, shrinkage gradient as well as bottom layer deflection. With the same printing quality, early-age shrinkage, shrinkage gradient and the bottom layer deflection were reduced by adopting higher water-binder ratio. The influence of materials on the moisture evaporation rate and early-age strength was also measured and correlated with early-age x-direction shrinkage, shrinkage gradient of 3DPC and the extent of early-age bottom layer deflection.

Mechanical Properties and Durability of Sustainable UHPC Using Industrial Waste Residues and Sea/Manufactured Sand

Abstract Considering the continuous development of sustainable development, energy saving, and emission reduction concepts, it is very important to reduce concrete’s cement content in order to improve its environmental impact. Using a reactive admixture to replace part of the cement in ultra-high-performance concrete (UHPC) can effectively improve the overall performance of the concrete and reduce carbon dioxide emissions, which is an important aspect of environmental protection. Here, industrial waste residue (fly ash and slag), sea sand (SS), and manufactured sand (MS) were used to produce UHPC under standard curing conditions to reduce the material cost and make it more environmentally friendly and sustainable. The effects of water–binder ratio, contents of cementitious materials, types of sands, and content of steel fibers on the mechanical performance of UHPC under standard curing were investigated experimentally. In addition, evaluations of the impermeability, chloride, and freeze-thaw resistance of various UHPCs produced were conducted by investigating the effects of various factors on the depth under hydraulic pressure and electric flux of UHPC, as well as the mass loss, relative dynamic modulus of elasticity, flexural strength, and compressive strength of UHPC specimens after freeze-thaw cycles. The obtained experimental results show that the SS-UHPC and MS-UHPC prepared by standard curing exhibit high strength, excellent impermeability, and chloride resistance. The frost-resistant grade of all groups of UHPCs prepared by standard curing was greater than F500 and had excellent freeze–thaw resistance, including those produced with local tap water or artificial seawater. The investigation presented in this paper could contribute to the production of new low-cost and environmentally friendly UHPCs and accelerate the application of UHPC in engineering structures.

In situ resource reutilization of earth pressure balance (EPB) shield muck for the generation of novel synchronous grouting materials

The utilization of large quantities of shield muck resources is a pressing issue that requires immediate attention and resolution. In this paper, an innovative approach that fully utilizes shield muck as an aggregate for synchronous grouting is introduced to realize the in situ resource utilization of this material. The newly formulated synchronous grouting grouts comprise shield muck and a solid waste-based cementitious material. The influences of components and compositions on the macroscopic performance of new grouts are investigated, and the formulation is optimized with a single-factor test and response surface methodology (RSM) analysis. The optimal formulation with a slurry specific gravity (SG) of 1.383 g/cm³ and a cementitious material (CM) content of 21.456% is determined. The microscopic characteristics of the grouts are revealed by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). Two main hydration products, namely AFt and C-S-H gel, are observed, exhibiting a crisscross growth pattern that contributes to the formation of a robust micronetwork structure. A full set of shield muck in situ pulping equipment is independently developed, thereby establishing an integrated grout production process. Considering the Suzhou Metro Line 6 as an engineering case, a field industrialization experiment is conducted, and the results demonstrate that the pulping system operates smoothly and can stably produce grouts. Compared with conventional cement-based finished grout, the newly developed synchronous grouting material with an optimal formulation exhibits significant superiorities in terms of surface deformation control (average reduction of 30∼40%), segment attitude control, and anti-seepage effect. The proposed approach effectively realizes in-situ resource utilization and source reduction of shield muck and can significantly reduce the cost of synchronous grouting. Aligned with the dual carbon strategy, the prospects for widespread adoption of this approach are promising, and the results of this study are highly significant.

Properties of fibre-reinforced self-compacting concrete subjected to prolonged mixing: an experimental and fuzzy logic investigation

This article investigates the effect of prolonged mixing on the rheological properties and compressive strength of fibre-reinforced self-compacting concretes (FRSCCs). Twenty FRSCC mixes with five cementitious material contents (300, 350, 400, 450 and 500 kg/m3) and three types of fibres and dosages (polypropylene at 0.1%, steel at 1.0%, or synthetic at 1.0%) were first produced. The mixes were then subjected to four mixing intervals of 20 min each (total mixing time = 80 min). The rheological properties of the fresh FRSCC mixes were examined, and the corresponding compressive strength of the hardened FRSCCs was subsequently obtained. Overall, the results from slump flow, T50, V-funnel and L-box tests on fresh mixes, as well as the 28-day compressive strength on the hardened FRSCCs, were in line with previous results reported in the literature. The results show that all mixes lost their self-compacting properties after 80 min of mixing. It was also found that mixes with high cementitious material contents (500 kg/m3) and highest polypropylene fibre dosage were most affected by prolonged mixing, with average losses of 30% and 35% in rheological properties and compressive strength, respectively. Based on the test results, this study proposes a novel fuzzy logic approach to predict the slump loss and at 28-day compressive strength loss of FRSCCs subjected to prolonged mixing. This article contributes towards a better understanding of FRSCCs after prolonged mixing, which can help make informed decisions about their use in new and repaired concrete structures.

The Sustainability of Using DuraCrete as Cement Additive to Estuarine Soft Soil Stabilization

Large areas of estuarine deposits exist on the coastal plains of the southeast Queensland coast with a countered depth of up to 30 m. These deposits are categorized as sediments that originated during the Holocene Age. The sediments have not been consolidated or subjected to considerable pressure since the end of the Ice Age. The structure of these deposits consists of large ratios of porosity, causing high soil compressibility, which lowers the bearing capacity of the soils. Therefore, the soils of the region cannot maintain sufficient support for construction loads, and consequent malfunctions could occur in short-term and long-term periods. The objective of this paper is to investigate the suitability of new soil stabilization additives in the southeast Queensland region and the optimum additive content of cementitious materials and an advanced mixing modifier branded as DuraCrete. A combination of Portland cement and DuraCrete was used as a soil additive. Three DuraCrete-to-cement ratios were used: 2%, 3%, and 4% by weight. Soil collected from the Port of Brisbane region was treated by adding the additives as a percentage of its weight; four percentages were considered: 10%, 20%, 25%, and 30% for each combination of additives. The performance of the treated soils was examined under unconfined compression after 28 days of curing. The results revealed that increases in the unconfined compressive strength were detected as DuraCrete was added to the mixtures. For 30% additives, increases of about 15%, 34%, and 17% were detected when DuraCrete was added as 2%, 3%, and 4%, respectively. The results also revealed that 3% DuraCrete content provided significant stabilization compared to 2% and 4% for 25% and 30% additive-treated soils; such behavior was also observed for the specimens of 25% content of additives. Additionally, DuraCrete can be considered a promising material that can be combined with cement to obtain the desired stabilization of soft soils.

Use of cellulose nanomaterials in cementitious composites reinforced with basalt/polymer pellets for repair of concrete

Using cellulose nanomaterials (nano-crystalline [NC] and/or nano-fibrillated [NFC] cellulose) with a high content of supplementary cementitious materials and special class of basalt fiber/polymer (BFP) pellets could produce sustainable and resilient composites for a suite of infrastructure applications. Hence, this study investigated the development of cementitious composites comprising high content slag (50% as cement replacement), BFP (4.5% by volume), NFC ranging from 0 to 0.5% (addition to the mass of the binder) and NC (0 to 0.1% addition to the mass of the binder) to prepare multiple formulations without/with nano-silica (reference nanomaterial) for repair/overlay applications of concrete flatwork. An integrated experimental program including constructability, mechanical capacity, and durability properties as well as compatibility with substrate concrete was conducted. Findings of these tests were corroborated with thermal and microstructural tests to evaluate the hydration/pozzolanic development and pore structure features. The overall results indicated that the development of high-cementitious composites with cellulose nanomaterials is possible, as they achieved balanced behaviour in terms of workability, hardening rates, high early- and later-age compressive strengths, high ductility, improved durability, and superior thermal and elastic integrity/compatibility with the parent/normal concrete. Thus, they may present an attractive option for repair and overlay applications of concrete flatwork.

Investigation on crack resistance of full aeolian sand high-performance concrete synergistically modified by supplementary cementitious materials and superabsorbent polymer

The development of full aeolian sand high-performance concrete (FA-HPC) can alleviate the dilemma of river sand shortage. However, the high cracking potential appears due to the characteristic of low water-to-binder ratio and high cementitious materials content. Herein, supplementary cementitious materials (SCMs), i.e., fly ash and silica fume, and superabsorbent polymer (SAP) are used to optimize the crack resistance synergistically. The crack resistance in plasticity and hardening stages are investigated based on flat plate cracking and ring restrained cracking combined with chloride ions penetration, respectively. Meanwhile, capillary pressure, mechanical strength, and internal temperature field were also involved. Additionally, the modification mechanism of SCMs and SAP is analyzed from a microscopic perspective via hydration heat, phase analysis, and microstructure. The results showed that whether single use or binary mixing, fly ash and silica fume significantly improved the crack resistance of FA-HPC. Moreover, it was further enhanced by the SAP, presenting a 63.39% and 96.96% increase in crack resistance at plasticity stage and hardening stage respectively as well as a 78.31% reduction in chloride ions penetration. Contrary to silica fume, fly ash hindered early hydration leading to a decrease in capillary pressure, strength, and internal temperature field with content dependence. Besides, the most intense volcanic ash reaction was observed in binary mixing. Although SAP delayed the early hydration, the later hydration degree was improved obtaining more hydration products at 28d since the internal curing effect. Thereby, the more refined microstructure was achieved for more optimized crack resistance. This study provides an available strategy for reducing the cracking risk of FA-HPC to promote wide application in engineering.

Effect of super absorbent polymer (SAP) on volume stability and application performance of cement mortar with accelerator

Shotcrete has high cementitious material content, small aggregate particle size, high setting accelerator content, and is prone to shrinkage and deformation, and there are few studies on the volume stability of shotcrete at present. Super absorbent polymer (SAP) is widely used as an internal curing agent, it has low cost and small dosage usage, but it has not been applied to shotcrete to improve volume stability. In this study, super absorbent polymers with different dosages, particle sizes, and extra water were used. The application performance, volume stability and moisture change of different cement mortars were studied under the condition of 4 % of alkali accelerator or 7 % of alkali-free accelerator. The results show that with the increase of super absorbent polymer dosage, the setting time of cement mortar mixed with accelerator is shortened, the 1-day compressive strength is reduced, and the 28-days compressive strength is on average increased. Among them, 0.4SAPAS (addition of 0.4 % SAP) can reduce the initial and final setting time by 101 s and 154 s. Further, the autogenous and drying shrinkage are reduced, and the internal humidity change and mass loss are slowed down. At the age of 180 days, the autogenous and drying shrinkage of 0.4SAPAS were 51 % and 47 % lower than those of AS-7. The XRD, SEM and hydration temperature test showed that the use of super absorbent polymer slightly delayed the hydration process at early age, the hydration temperature peaks of AS-7,0.2SAPAS and 0.6SAPAS are 38.5 °C, 36.7 °C, and 35.1 °C. But at 28 days, the surrounding cement particles were further hydrated due to the release of water from super absorbent polymer.

Cementitious materials limitations for concrete exposed to deicing salt plus repeated cycles of freezing and thawing

AbstractReducing the carbon footprint of concrete generally involves reducing the amount of calcium oxide in the cementitous materials by blending flyash and/or ground limestone into the cement or by replacing some of the cement with supplementary cementitious materials. This increases the ratio of SiO2+Al2O3+Fe2O3 to CaO+MgO in the cementitious material. While reducing the CaO content of cementitious materials is good for the environment, it may not be good for concrete exposed to deicing salts plus repeated cycles of freezing and thawing due to the effect of carbonation. Though carbonation can refine the pore structure when using only portland cement, it coarsens the pore structure when using high levels of cement replacement. This leads to increased scaling potential. A review of the effects of different cementitious materials combinations on carbonation along with an examination of field performance of concrete exposed to deicing salt plus repeated cycles of freezing and thawing is used to develop a relationship based on the ratio of SiO2+Al2O3+Fe2O3 to CaO+MgO in order to determine when limitations on cement replacement, or additional protective measures may be needed when scaling is a concern.

Performance-based alkali-activated seawater sea-sand concrete: Mixture optimization for mechanical, environmental, and economical objectives

This study aims to explore the viability of employing alkali-activated materials (AAMs) as alternatives for ordinary Portland cements (OPCs) in seawater sea-sand concretes, thereby promoting the sustainable utilization of marine resources in island-based constructions. Artificial seawater, sea-sand, coral coarse aggregate (CCA), normal limestone aggregate (NLA) and slag-based AAMs incorporating with 15 wt% fly ash and 5 wt% silica fume were mixed to prepare performance-based alkali-activated seawater sea-sand concrete (ASSC). The L9 (33) Taguchi orthogonal method was employed to analyze the influences of the replacement ratio of CCA for NLA, cementitious material content and water-to-binder ratio on the workability, compressive strength, splitting tensile strength, carbon dioxide equivalent (CO2-e) emission, energy consumption and cost of ASSC. Three standardized evaluation indexes and the Gray-Technique of Ordering Preferences by Similarity to Ideal Solution (TOPSIS) model were proposed to estimate the influence degree of each factor, and the suggested optimal mixture for ASSC was determined to be a replacement ratio of CCA for NLA of 50%, a cementitious material content of 440 kg/m3 and a water-to-binder ratio of 0.45. Then, the microstructure characteristics of the interfacial transition zone (ITZ) between the matrix and aggregate of ASSC for the optimal mixture were observed by scanning electron microscopy (SEM). It can be concluded that the main hydration products of ASSC had dense surface pores and internal pores of CCA, reducing the length, width and number of micro-cracks in ITZ. The substrate effect and micro-pump of CCA generate a high dense ITZ between the aggregate and matrix, which can inhibit the crack development of ASSC.

Study on properties and soil solidification mechanism of alkali - activated cementitious materials

Due to the low strength and poor durability of soil, it is limited in engineering application. To improve its strength and durability, the alkali-activated (AA) cementitious materials were prepared using industrial wastes, and experiments were performed on AA cementitious materials and solidified soil, including mechanical properties tests, water stability tests, and microscopic properties tests. The results indicate that the content ratio of fly ash and slag can significantly affect the properties of AA cementitious materials, and the maximum 28d compressive strength reaches 36.1 MPa. With increasing AA cementitious materials content (up to 50%) and age, both the compressive strength and tensile strength of AA solidified soil enhance. The microstructure evolution process of soil after solidification includes four stages, including mineral material dissolution, silicon aluminum diffusion, polymerization of low polymer silicon aluminum salts, and polymer soil particle cementation and hardening. The mineral raw material particles and soil particles are effectively bonded due to the adhesion between the reaction products and the mineral material, which improves the performance of the AA solidified soil. The maximum 28d compressive strength of AA solidified soil was 3.6 MPa, the maximum tensile strength was 1.05 MPa, and the maximum water stability coefficient was 0.89.

Designing sustainable high-strength self-compacting concrete with high content of supplementary cementitious materials

A sustainable and green approach to concrete mix design is fundamental for the construction sector in terms of reducing carbon dioxide ( CO 2 ) emissions and conserving non-renewable natural resources. This article proposes a novel mix design method for sustainable high-strength self-compacting concrete (HSSCC) based on rheological and mechanical properties with the aim of reducing cement content in such mixes. HSSCC mixes were designed using ground granulated blast furnace slag (GGBS) and fly ash to replace up to 40% of the cement content and tested for target compressive strengths ranging between 70 and 100 MPa. The proposed design method was numerically programmed to provide straightforward and realistic guidance in the form of design charts and verified through the design and production of sixteen HSSCC mixes consisting of varying sand-to-aggregate ratios (S/A). All mixes satisfied the self-compacting concrete criteria in the fresh state and achieved the targeted viscosity and compressive strength values. The effects of S/A and paste-to-solid (P/S) ratios on the rheological properties were evaluated. The experimental results demonstrated that the proposed mix design method could produce HSSCC with excellent fresh and mechanical characteristics while being eco-efficient with respect to CO 2 emissions and cement consumption.

Carbonation curing of modified magnesium-coal based solid waste backfill material for CO2 sequestration

CO2 sequestration is an effective method for dealing with the global climate crisis, and carbonation curing is considered an effective method of sequestering CO2 and improving the mechanical properties of cement-based materials (CBM). Regarding modified magnesium-coal based solid waste backfill material (MB), to explore its carbonation curing performance and CO2 sequestration capacity, its uniaxial compression strength (UCS), carbonation depth, microstructure, CO2 transport performance, CO2 uptake capacity, and carbonation efficiency are analyzed and characterized using UCS tests, thermogravimetric analysis (TGA), X-ray diffraction (XRD), and nuclear magnetic resonance (NMR) analysis. The results show that the early UCS of the MB is significantly improved by carbonation curing. The UCS at 7 days is 10.91 times higher than that of the MB without carbonation curing, and the UCS increases as the concentration and modified magnesium slag-based cementitious material (MC) content increase. Carbonation curing makes the microstructure of the MB significantly denser and reduces the porosity, pore diameter, and permeability. The formation of carbonated products such as calcium carbonate and hydration products makes the microstructure more compact, which is the main reason for the rapid increase in the early UCS of the MB. The maximum CO2 uptake capacity of the MB through carbonation curing is 14.3%, and the carbonation efficiency is up to 92.2%. Therefore, carbonation curing of MB has broad application potential in improving the UCS and sequestering CO2.

AI-guided design of low-carbon high-packing-density self-compacting concrete

Self-compacting concrete (SCC) has gained substantial traction in modern engineering due to its exceptional fresh and hardened properties. However, traditional SCC design methods encounter significant challenges. Conventional experimental design approaches often necessitate a considerable number of trial mixes to fulfill diverse performance objectives, incurring escalated material, time, and labor costs. Additionally, conventional SCC designs tend to use high cementitious material content, leading to elevated carbon emissions and energy consumption compared to ordinary concrete. To address these issues, this study proposes a novel approach that combines the compressible packing model (CPM) with machine learning (ML) techniques. This approach innovatively utilizes particle packing theory to guide ML in optimizing SCC aggregate grading and mix proportions. By integrating physical principles into artificial intelligence, this approach facilitates the intelligent design of low-carbon, high-packing-density SCC. Compared to the conventional method, SCC designed using the innovative AI approach demonstrates a 57.2% reduction in embodied carbon emissions.

Impact of cementitious materials on the resilient modulus and damping ratio of weak subgrade

Pavement structures are constantly subjected to cyclic loadings. The resilient modulus and damping ratio are frequently used to evaluate the stress–strain relationships and energy dissipation for pavement subbase and subgrade. This paper presents an experimental study on the resilient modulus characterization, and damping ratio calculation for hydraulic road binder (HRB) treated weak subgrade soils. Results indicated that similar to General Use (GU) cement, HRB significantly enhanced the soil’s resilient modulus by increasing internal structural stability in cementitious treated soils. Using current stress-dominated constitutive models, a fair prediction can be achieved for GU- and HRB-treated soils, especially for lower MR values (<500 MPa). In addition, there is a concave downwards relationship between the damping ratio, total axial stress, and resilient modulus, respectively. Under repeated loading, higher energy dissipation for treated soils is anticipated within a certain range of axial stress levels.Furthermore, the mean resilient modulus of GU- and HRB-treated soils highly correlated with moisture content and with the actual content of cementitious materials: cement clinker and ground-granulated blast-furnace slag (GGBFS) in the treated soils. Their contributions could be further quantified by efficiency factors. Overall, the outcomes of this study could be a reference for the future investigation and development of hydraulic road binders and contribute to the future substitute of conventional Portland cement in pavement engineering.

Evolution and mechanism on shrinkage of high-performance concrete with full aeolian sand cured by superabsorbent polymer

Preparing high-performance concrete with full aeolian sand (FA-HPC) can address the shortage of high-quality aggregates. Its low water-binder ratio (w/b) and high content of cementitious material content endow this concrete with great strength and durability but a high risk of shrinkage cracking. Herein, the effect of superabsorbent polymer (SAP) on the separate shrinkage of FA-HPC, and the mechanism of internal curing (IC) were investigated from various macro–micro perspectives. IC water migration was monitored via nuclear magnetic resonance (1H NMR). The results showed that autogenous shrinkage dominated the total shrinkage of the FA-HPC, accounting for 70%–80%. The SAP with medium particles effectively reduced the total shrinkage in the plastic and hardening stages, with nearly zero autogenous shrinkage at 0.3% content. From the characterization of mechanism, capillary pressure build-up of FA-HPC containing SAP was delayed with significant suppression in internal relative humidity (IRH) drop and moisture loss especially due to self-desiccation. The coupling effect of self-desiccation and evaporation triggered the nonlinear correlation between moisture loss and total shrinkage, whereas SAP amplified the proportion of drying shrinkage. Microscopically, the incorporation of SAP with IC water hindered the early hydration process but resulted in a higher final hydration degree within 72 h bringing a refined pore structure. Moreover, the adaptive release of IC water was used for hydration mainly within 72 h, and it continuously compensated for IRH drop over 28 d based on the supply–demand mechanism in FA-HPC. This study proposes a promising strategy for shrinkage resistance of FA-HPC and promotes the application of aeolian sand-based concrete.