Development Of Ultra-high Performance Concrete Research Articles

A machine learning framework for intelligent development of Ultra-High performance concrete (UHPC): From dataset cleaning to performance predicting

This study proposes a new machine learning (ML) framework, which mainly includes dataset cleaning processing as well as performance predicting, for property prediction of ultra-high performance concrete (UHPC). Firstly, the missing data in original dataset is interpolated and discussed by visualization results. Then, the existing outliers in the completed dataset are found out to improve the quality of dataset. Meanwhile, by analyzing the influence of key parameter, it not only clarifies the influence of dataset quality on model prediction results, but also proves the necessity of anomaly detection, with R2 increasing 15 % and RMSE decreasing 37 %. Finally, the chosen model is trained and further optimized by hyperparameter optimization, in which the loss function is significantly reduced by 68.82 % for training data (R2 > 0.95) and 84.36 % for testing data (R2 > 0.94). Overall, this framework can effectively improve the accuracy and generalization of UHPC predictive models, which is also suitable for other types of concrete materials.

Study of the spent catalysts as internal curing agents on the hydration kinetics and microstructure development of ultra-high performance concrete (UHPC)

In this study, the effect of 5–30 % (by mass) of spent catalyst (SC) on the characteristics of ultra-high-performance concrete (UHPC) is investigated, including mechanical properties, volumetric stability, hydration kinetics, and microstructural development. Specifically, scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and low-field proton nuclear magnetic resonance spectroscopy (1H NMR) are employed to clarify the microstructures, while thermogravimetric analysis (TG), X-ray diffraction (XRD), and energy-dispersive spectroscopy (EDS) are carried out to understand the phase variation. The results obtained show that the samples containing SC and additional water exhibit good mechanical properties, such as a 1.0 %-2.9 % higher compressive strength of UHPC with SC (5–15 %) and additional water compared to SC1 at 60 days. Additionally, SC can also improve the volumetric stability of UHPC. Moreover, the Ca/Si ratio of the hydration products decreases and the Al/Ca ratio increases with the enhancement of SC and additional water content. Furthermore, the water release effect of SC promotes the hydration of cement and pozzolanic reactions, leading to the generation of more hydration products and optimization of the pore structure and interfacial transition zone (ITZ) of UHPC in this study.

Sustainable development of ultra high-performance concrete using basil plant waste: Investigation at normal and extreme conditions

This study highlights the potential of using Basil plant (BP) waste as a viable and sustainable alternative to partially replace cement in ultra-high-performance concrete (UHPC), which can contribute to developing more sustainable and eco-friendly building materials. It investigates the effect of BP waste powder as an alternative solution on the performance of UHPC under high temperatures and severe environmental conditions. The aim was to achieve environmentally friendly green UHPC by minimizing cement content. The effect of using BP as a cement replacement with different percentages of 10 %, 20 %, 30 %, and 40 % by weight, on compressive strength, splitting tensile strength, sorptivity, and microstructure was evaluated. In addition, investigation was performed at different conditions of ambient temperature, high temperatures of 300 °C and 600 °C and severe environments subjected to chlorides and sulfates. The results showed that premixing UHPC with 30 % BP waste could improve compressive strength, with a maximum increase of 10 % at 28 days, and with decreasing sorptivity by 28 %. Additionally, the microstructure analysis revealed that incorporating BP waste leads to a denser structure and a reduction in the average pore size of the UHPC, which can enhance the durability and longevity of UHPC in construction applications. The findings of this study have important implications for the construction and building materials industry, which is under increasing pressure to adopt sustainable construction practices.

Influence of red mud on the engineering and microstructural properties of sustainable ultra-high performance concrete

This paper introduces a new application of industrial solid waste red mud to use as a cementitious material in the development of ultra-high performance concrete (UHPC) performances. In addition, utilization of red mud can reduce the environmental impact of red mud landfill. For gaining this aims, UHPC specimens were prepared with different contents of red mud and analyzed the effects of different RM contents on the fluidity, setting time, mechanical properties, durability, drying shrinkage and microstructure of the red mud-based UHPC. The results indicated that fluidity was reduced to 310 mm at 20% red mud level, but it still belongs to enormous fluidity, which is convenient for construction. In addition, it is worth noting that using red mud instead of cement can significantly shorten the setting time, providing a new method for applying the UHPC rapid-repairing process. Red mud-based UHPC mortar prepared with appropriate red mud instead of cement exhibits higher mechanical properties, better durability and reduced drying shrinkage of UHPC during curing. After curing for 28d, the highest compressive strength of UHPC samples containing 20% red mud was 129.5 MPa, the compressive strength of the UHPC samples' sulfate resistance was 136.6 MPa, and the drying shrinkage value was around 414 µm. Moreover, observed information from scanning electron microscopy (SEM) noted that red mud can fill the micro-cracks between particles of cementitious materials, make the structure more compact and form new hydrates. Finally, the two characteristics of low cost and energy consumption further promote the sustainable application of red mud-based UHPC. Therefore, replacing OPC with 20% RM is meaningful to produce a sustainable UHPC mixture and field applications.

Hydration kinetics and microstructure development of Ultra-High Performance Concrete (UHPC) by high volume of phosphorus slag powder

In this paper, the effect of phosphorus slag(PS)hydration kinetics and microstructural development of UHPC with different degree of substitute (20%, 40% and 60% by mass) were explored. Up to 60% substitution of cement by PS which still shown excellent mechanical property compared to without PS at the age of 60-days. The phase development is a qualitative discussion by thermal gravimetric analysis combined with XRD with Rietveld method, the pore structure is evaluated to MIP. The hydration products are characterized by SEM (scanning electron microscopy) with EDS (Energy-dispersive X-ray) analyses. The results shown that the utilization rate of cement has been significantly improved, for instance, the hydration rate of the cement is enhanced from 54.3% for PS0 to 87.0% for the UHPC with PS60; the Ca/Si ratio decreased with the enhance of PS content and the microstructure is become denser by SEM-EDS tests. The pozzolanic-reaction of PS cloud produce more hydrated products by thermodynamic calculation, which can optimize the pore structure of paste. And the growth trend of C–S–H gel is consistent with the compressive strength growth trend.

Development of an environmental Ultra-High Performance Concrete (UHPC) incorporating carbonated recycled coarse aggregate

This paper presents a new idea based on the efficient use of recycled Construction and Demolition Waste to produce advanced building materials, which focus on the development of Ultra-High Performance Concrete (UHPC) by carbonated recycled coarse aggregate (CRCA). Firstly, the accelerated carbonization is used to strengthen the recycled coarse aggregate. Secondly, the improved Andreasen&-Andersen (A&A) particle accumulation model is used to develop CRCA-UHPC with a maximum particle size of 4.75 mm. After that, the impact of the added CRCA on the performances of UHPC are evaluated, including flowability, setting time, compressive strength, volume stability, durability, microstructure, etc. The obtained results show that when the RCA is subjected to carbonation treatment, its drawbacks of physical and mechanical characteristics can be efficiently restricted, and the properties of UHPC incorporating CRCA could be improved, including compressive strength, volume stability, resistance to chloride ion penetration, microstructure and eco properties. Therefore, the CRCA-UHPC proposed in this study should be a promising sustainable new construction material, which can not only solve the environmental problems caused by construction waste and CO2 emission, but also provide an advanced building material.

A low-carbon alkali activated slag based ultra-high performance concrete (UHPC): Reaction kinetics and microstructure development

Ultra high performance concrete (UHPC) is a cement-based material with great development prospects. However, the production of cement will produce a large amount of CO 2 , which does not conform to the current global trend of energy conservation and emission reduction, and limits the further development of UHPC. One of the ways to further develop UHPC is to reduce the carbon emissions in the production process of UHPC. The aim of this study is to develop a low-carbon alkali activated slag based Ultra-High Performance Concrete (A-UHPC) with ultra-low moisture content. Firstly, based on the particle dense packing model, an optimized combination of low-carbon cementitious mixture and aggregates skeleton is designed. Then, the effects of moisture content on the macro-properties, hydration mechanism and micro-mechanism of the developed A-UHPC are studied. The experimental results show that the fresh performance and macroscopic mechanical properties of A-UHPC are advanced at low moisture content. When the water-binder ratio is 0.29, the compressive strength at 28 d is the highest, reaching 118 MPa. Besides, low moisture content A-UHPC also shows good microscopic properties: its hydration degree can reach 62.58% and the longest molecular chain length of the polymer is about 4.74. In general, the developed A-UHPC can meet the requirement of high performance and low CO 2 emission simultaneously, which could be one of the most suitable choices to achieve the goal of “Carbon peak and Carbon neutral” in the near future. • A novel method for designing a low carbon UHPC is presented. • The newly developed UHPC exhibits admirable ecological value. • Mineral powder and alkali-activator are adopted in UHPC. • Low moisture content A-UHPC is developed. • 5.The effect of water on the macro and micro properties of A-UHPC is studied.

Quantitative effect of seawater on the hydration kinetics and microstructure development of Ultra High Performance Concrete (UHPC)

This paper aims at quantitatively investigating the effect of seawater on the hydration kinetics and microstructure development of Ultra-High Performance Concrete (UHPC). Specifically, the macroscopic properties of UHPC mixed with seawater are tested, including fresh behaviors, mechanical properties and autogenous shrinkage. In addition, hydration products, hydration heat and hydration degree of UHPC made with seawater are quantitatively evaluated. Finally, the influences of seawater on the surface morphology, nano-mechanical properties and pore structure of UHPC are analyzed. The obtained results uncover that the incorporation of seawater can dramatically decrease the flowability, enhance the flexural and compressive strengths, as well as deteriorate the autogenous shrinkage of UHPC. Moreover, with the addition of seawater, the hydration degree can be increased by 4.67%, not only by consuming more cementitious materials to generate more hydration products (about 12.25%), but also by enhancing the mean chain length of C-S-H gels from 3.5068 to 4.1595 and increasing Q2/Q1 from 0.7533 to 1.0796 to improve the polymerization of hydration products. Additionally, the incorporation of seawater can contribute to a dense microstructure of UHPC by enhancing indentation modulus and hardness of paste by approximately 25.25% and 29.10%, optimizing the ITZ by about 15 mm, as well as refining pore size and reducing the porosity by more than 8%.

Role of silica fume on hydration and strength development of ultra-high performance concrete

Silica fume (SF) is the most commonly used ingredient in ultra-high performance concrete (UHPC) due to its inherited properties, which can effectively improve the rheology and mechanical performance. However, investigations with regard to its filler effect and pozzolanic reaction on UHPC are limited. To assess the contribution from SF, a chemically inert filler of titanium dioxide (TD), with a comparable particle size distribution and specific surface area (per unit volume), was selected as a reference ingredient to eliminate the influence of packing effect. Results showed the addition of SF will accerate the early hydation of UHPC and it is controlled by the combined effect of seeding effect and preferential adsorption. Moreover, the SF’s surface characteristic controlling the concentration of adsorption sites provided for hydration product is the key factor influencing the early hydration rather than surface specific area. Furthermore, the enhancement of compressive strength of UHPC after 3 days is attributed to the pozzolanic reaction of SF and its promoting effect on cement hydration degree. The total contribution is less than 20%, and it will enhances with the decrease of W/C ratio.

Hydration kinetics and microstructure development of Ultra-High Performance Concrete (UHPC) subjected to microwave pre-curing

This research aims to clarify the intrinsic effect of microwave pre-curing on the hydration kinetics and microstructure development of Ultra-High Performance Concrete (UHPC). Six hours after casting, the UHPC samples are subjected to microwave pre-curing for 60–240 s. Then, the macro and micro characteristics of the cured UHPC are evaluated. The observed experimental results show that the microwave treatment can create a dense shell around the cured UHPC's periphery, which can resist the lateral deformation of the specimen and guarantee the excellent mechanical properties of the treated sample. Moreover, when steel fibres are included into UHPC, the reflection and shielding effect of the 3D fibres network can significantly block the promotion effect of microwave on the strength development of UHPFRC. Additionally, due to the high energy of microwave, high polymerization hydration products and advanced pore structure (micro and meso scales) can be observed in the pre-cured UHPC.

Ultra high performance concrete shear walls

The history of the development of Ultra-High Performance Concrete (UHPC) shear walls and the current status of today’s research as well as the future development prospects are comprehensively collated. The analysis process and conclusive results of the present-day domestic and international research on UHPC shear walls are highlighted. The load displacement curves, hysteresis curves and skeleton lines of ultra-high performance concrete shear walls under different experimental loads are collated and compared. Integrate the corresponding equations for shear bearing capacity and equations for the overall specimen load displacement curves. A finite element model of the ultra-high performance concrete shear wall is established to simulate and perform non-linear finite element analysis of its force process under unidirectional horizontal loading.

A review study on sustainable development of ultra high-performance concrete

<abstract> <p>A systematic literature review was undertaken in this report to illustrate the development concepts and properties of ultra-high performance concrete (UHPC). UHPC's affluent development relies on its compositional content, water–binder (w/b) ratio, and design mix approach, which contributes to denser and comparatively more homogeneous packaging of particles. Numerous research studies from around the world were used to compile a database on UHPC mechanical and durability properties. Moreover, the results of this study reveal that the curing conditions, aggregates, fibre dosage and characteristics, and curing time are the most important elements in determining the mechanical and durability qualities of UHPC. Furthermore, due to its ultra-high-strength features, superior fatigue behavior, and extremely low porosity, UHPC is considered a practical and long-term alternative for improved sustainable building, resulting in increased resilience to hostile environments. Besides that, attempts are being taken to resolve existing challenges (such as high initial costs, a lack of skills, and a lack of design code) and their solutions to their widespread economic use. This study aims to help architects, builders, and other construction stakeholders better grasp UHPC's basic features and capacities, which will help to understand this durable and long-lasting building material.</p> </abstract>

Sustainable use of red mud in ultra-high performance concrete (UHPC): Design and performance evaluation

This paper presents an efficient application for red mud, i.e., recycling red mud as a mineral additive in the development of ultra-high performance concrete (UHPC). Specifically, the modified Andreasen & Andersen particle packing model has been carried out to obtain a densely compacted UHPC matrix. After that, red mud is used to replace cement to reduce both the landfilling of red mud and the environmental burden of UHPC. Then, the fresh and hardened behavior of UHPC with and without red mud has been evaluated. It has been found that the addition of red mud enhanced early-age (7 d) durability due to the accelerated hydration process, while reduced the workability and the mechanical properties of UHPC. The degraded workability may affect the application in the building with complex shapes, but it can still be applied in general construction. An ultra-high strength (>150 MPa) of UHPC including 40% red mud can be generated after high-temperature curing, although the addition of red mud reduces the compressive strength. Besides, it is noteworthy that significantly shortened setting time can be obtained when replacing cement by red mud, providing ideas for the application in the UHPC rapid-repairing process. The pore structure analysis reveals a coarsening of micro-pore structure with an increase of red mud content. Finally, a low-energy consumption, as well as low radiation risk further promotes the environmental protection application of red mud based UHPC.

Performance evaluation of ultra-high performance concrete designed with alccofine

This paper presents a study on the development of ultra-high performance concrete (UHPC) by incorporating alccofine. Quartz powder and ground granulated blast furnace slag are used separately along with alccofine and silica fume to design UHPC mixtures. Coarse aggregates of 6 mm and 10 mm diameters are also introduced into UHPC in order to reduce the binder quantity. As part of the performance evaluation, mechanical strength properties of eight UHPC mixtures were investigated. The findings of the study indicate that UHPC containing alccofine produced improved mechanical performance relative to silica fume incorporated UHPC. The UHPC mixture containing alccofine and ground granulated blast furnace slag has produced cumulative values of 136.67 MPa, 15.2 MPa and 31.88 MPa for compressive strength, splitting tensile strength and flexural strength, respectively, at 28 days of normal curing. The use of coarse aggregates in UHPC culminated in a gradual decline in mechanical performance and an increase in slump values of the concrete. Mathematical modeling and statistical analysis were carried out using response surface model to predict the compressive strength values, compare them to experimental outcomes and check their validity. The results of this study indicate that UHPC developed by blending alccofine has yielded an overall better performance.

Micro-chemo-mechanical features of ultra-high performance glass concrete (UHPGC)

The development of Ultra-High Performance Concrete (UHPC) opened new research directions for enhancing the architectural design, sustainability and serviceability of concrete structures. However, the costs and resource intensiveness trigger the need for innovative UHPC mix design incorporating alternative materials, such as post-consumption Glass Powder (GP). This works aims at disclosing the microstructure features of UHPGC, in which the constituents can be partially replaced by different fineness of GP without impacting the long-term strengths. By using the latest NI-QEDS technique (coupling NanoIndentation and Quantitative Energy-Dispersive Spectroscopy), as well as image analysis applied to EDS chemical mappings, it was possible to investigate mechanical properties of the microstructure constituents and their volume fractions. A conventional UHPC microstructure was compared to a similar system with 30% replacement of cement by GP and to another system with 50% replacement of silica fume by Fine GP (FGP). The results showed the key role of GP anhydrous particles contributing to the rigid skeleton of anhydrous inclusions, as well as their bond quality with the surrounding cement paste. The reduction of cement and silica fume was thus possible without impairing the micromechanical properties of the hydrates, by improving the particle packing density in the hardened state. As major conclusion, replacing cement and silica fume with GP and FGP without impairing both micro-scale and macro-scale mechanical properties provides a promising means to reduce the environmental footprint of current UHPC mix design.

Evaluation of high performance cementitious grouts for connecting precast concrete bridge deck panels

The use of full-depth precast concrete panels for rehabilitation of bridge decks allows fast installation and all-weather construction. Typically, precast panels are prefabricated in a well-controlled environment, resulting in strong and durable products. Undoubtedly, they will perform well under the traffic loading and weathering. However, the panel joints that are closed later with grout pour may degrade prematurely, leading to a less desirable composite action. Obviously, the lack of overall system performance causes concerns that limit the wider application of this innovative construction method. Conventionally, cementitious grouts, epoxy mortars or polymer concretes are used for the closure pour. In general, epoxy mortars or polymer concretes have extremely low permeability and dry shrinkage, as well as good adhesion with the substrate; but they are difficult to mix and clean, very sensitive to moisture variations, and incompatible with the substrate under thermal and mechanical loads. As a result, deficient bonding may occur, particularly when longitudinal post-tensioning is not provided, causing leaking and rusting. Oppositely, cementitious grouts are easier to mix and more compatible with the concrete substrate; however, they are more prone to shrinkage. More recently, advances in cementitious materials resulted in the development of Ultra-High Performance Concrete (UHPC). While this material has demonstrated exceptional performance when used for the closure pour; it requires special mixing to well disperse the particles and careful attention must be paid to the construction and curing practices to achieve enhanced mechanical and durability properties. As a result, testing of various types of grout materials is essential to establish the quality and serviceability of these materials. It is the intention of this paper to evaluate the performance of different cement-based grouting materials and to provide bridge engineers with useful database as to what materials are preferred for a specific project.

Development of ultra-high performance concrete with high fire resistance

Fire or high temperature is a big challenge to ultra-high performance concrete (UHPC). Strength loss of UHPCs can reach up to 80% after exposure to 800 °C. In this study, a total of six UHPC mixtures were designed and tested after subjected to elevated temperatures up to 1000 °C. The effects of aggregate type, fibre type and heating rate were investigated. Residual compressive strengths and stress-strain relationships were studied. Besides, attention was paid to explosive spalling since UHPCs are usually of compact structure and thus more vulnerable to explosive spalling than other concretes. Scanning electron microscope (SEM) analysis was conducted to help understand the mechanism of variation of internal structure under different temperatures. It was found the mixture containing steel slag and hybrid fibre had excellent fire resistance. After being subjected to 1000 °C, this mixture retained a residual compressive strength of 112.8 MPa or a relative value of 69%.

Effect of cement substitution by limestone on the hydration and microstructural development of ultra-high performance concrete (UHPC)

The effect of limestone on the hydration and microstructural development of ultra high performance concrete (UHPC) with different levels of replacement (34%, 54% and 74% by volume) was investigated. Up to 54% replacement of cement by limestone the mixes showed better workability and higher compressive strength (170 MPa at 56 days for 54% addition) compared to a classical mix (155 MPa) with no limestone replacement. The kinetics of hydration were compared for different replacement levels using isothermal calorimetry. The phase development was quantified by X-ray diffraction with Rietveld method combined with thermal gravimetric analysis. The pore structure was examined by mercury intrusion porosimetry. The composition of hydration products was determined by scanning electron microscopy with energy dispersive X-ray analysis. The results showed that the hydration degree of the cement is increased from 39% for classical UHPC to 66% for the UHPC with 54% of limestone.

Development of ultra-high performance concrete with locally available materials

Ultra-High Performance Concrete (UHPC) is an advanced type of concrete that can enhance the durability and resilience of concrete structures. The use of local materials is a fundamental step to save materials and energy and reduce the cost of concrete. In this study, the effect of sand gradation, binder type and content, and curing regimes on concrete’s compressive strength was examined. Results indicated a 90-day strength of 155MPa was achieved with a silica fume content of 5% and without heat curing. A curing regime of 2days at 60°C followed by 3days at 90°C resulted in the highest strength.

Materials Specification Needs for Future Development of Ultra High Performance Concrete

Abstract Over the next several years, new mixtures for ultra high performance concrete (UHPC) products are expected to move from prepackaged mixtures toward the use of locally available materials to make UHPC economically viable for future projects. Because a wider variety of materials will be used in UHPC, it will be necessary to develop or modify material specifications to ensure high quality UHPC mixtures are produced that provide strength and durability properties consistent with designers’ expectations. New or modified specifications will be needed for chemical requirements on the cement and supplementary cementitious materials considered for use in UHPC as well as to guide producers in the selection of aggregates for use in UHPC. This paper discusses these material issues along with issues related to admixture and fiber selection that are important to the future development of UHPC. Suggestions for development or modification of specifications that will ensure selection of high quality materials and potential performance based specifications that may evolve in the future are also provided.