29Si NMR study of hydration and pozzolanic reactions in reactive powder concrete (RPC)

doi:10.1016/S0730-725X(96)00174-9

Magnetic Resonance Imaging

Volume 14, Issues 7–8, 1996, Pages 891-893

https://doi.org/10.1016/S0730-725X(96)00174-9 Get rights and content

Abstract

A careful analysis of the ²⁹Si NMR signal of reactive powder concretes, composed of siliceous cement, silica fume, and crushed quartz, has been done in order to determine the hydration conditons on the kinetics of hydration.

References (3)

S. Masse et al.
Rivereau, A. ²⁹Si solid state NMR study of tricalcium silicate and cement hydration at high temperature
Cem. Concr. Res.
(1993)

There are more references available in the full text version of this article.

Cited by (27)

Influence of different curing methods on the compressive strength of ultra-high-performance concrete: A comprehensive review
2022, Case Studies in Construction Materials
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Therefore, RPC samples should be cured by unconventional regimes, such as hot, steam or autoclave curing. The hot dry air is the most suitable temperature for RPC curing, which might reach up to 250 °C; however, exposure of the samples to temperatures higher than 250 °C can reduce the compressive strength rate, causing dangerous deteriorations in the microstructure owing to the presence of cracks and pores on the sample surface [53,56–59]. The highest benefits of high-temperature curing can be identified as follows:
Ultra-high-performance concrete (UHPC) is a distinguishing material used in new construction and conjunction with conventional concrete. However, some issues limit the wider application of UHPC, such as high autogenous shrinkage, low workability for large-volume production, high cost, and unpredictable peak curing method. This comprehensive study aims to clarify the different effects of curing methods on the strength development of normal concrete and UHPC. The present article reviews studies that used microwave curing, autoclave curing, carbon curing, steam curing, electric curing, ambient and air curing and water to determine their effect on compressive strength. All the curing methods achieved satisfactory values of compressive strength. However, it is not practical to specify the peak curing regimes for concrete or UHPC since the best results need critical monitoring of curing parameters. The time when the samples are demolded and subjected to hydrothermal and thermal treatments varies in the literature since it depends on the binder setting time. That time should be carefully selected to avoid adverse effects and to maximise output. A combination of these curing regimes could be used together or with pressure or heat to further improve the compressive strength. In addition to the type of materials used, the curing temperature and duration significantly affect the overall performance of concrete. This review is expected to guide future research and provide an overview of the research field.
Ultra-high-performance fiber-reinforced concrete. Part II: Hydration and microstructure
2022, Case Studies in Construction Materials
Ultra-high-performance concrete (UHPC) refers to cement-based materials exhibiting a compressive strength higher than 150 MPa, high ductility, and excellent durability. Besides, over the last twenty years, remarkable advances have taken place in the research and application of Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC). Therefore, a comprehensive investigation of the durability characteristics of UHPC is essential to provide fundamental information for material testing requirements and procedures and expand its practical applications. Part I reviewed the developments, principles, and raw materials of the UHPFRC. This Part II covers the hydration and microstructure of the UHPFRC. Part III covers the fresh and hardened properties of the UHPFRC. Part IV covers the durability properties, cost assessment, applications, and challenges of the UHPFRC. This review is expected to advance the fundamental knowledge of UHPC and promote further research and applications of UHPC.
The influence of ingredients on the properties of reactive powder concrete: A review
2021, Ain Shams Engineering Journal
Citation Excerpt :
The most convenient temperature for RPC curing by hot dry air may reach up to 250 °C, while exposure to temperature more than 250 °C may prompt a decrease in the compressive strength. This may also cause a serious microstructure deterioration due to the existence of both large numbers of pores and cracks in the surface of the specimen [53,64,117,192,195–199]. To determine the main advantages of thermal curing, it can be summarized as follows:
Reactive Powder Concrete is a type of ultra-high-performance concrete. Improvement of microstructure, elimination of coarse aggregate, particle packing, and toughness enhancement are the main principles of RPC development. To achieve these principles, RPC is characterized by the inclusion of high cement content and pozzolanic materials that make in the other hand its production highly cost and non-environmentally friendly. This work reviewed the principals of developing RPC, the constituent materials, curing techniques and the constituent percentages that affect the compressive strength. The improvement of concrete microstructure, particle packing and toughness properties of RPC are briefly outlined along with the incorporated constituent materials. Curing techniques and the mixture design of RPC are also clearly highlighted.
In this study, the impact of using different percentages of the constituent materials of RPC and their available alternatives on compressive strength under different curing regimes are presented. It was showed that curing of RPC considered to be very important aspect in its development as it significantly affects the reactivity of its constituent. It was noticed that applying autoclave curing and using low cement dosage can achieve higher compressive strength results than applying steam curing. It was concluded also that the enhancement percentage in compressive strength can reaches 33% when using fly ash with 40% cement replacement under autoclave curing. It was observed that the enhancement percentage in compressive strength can reaches 45% when using rice husk ash with 30% silica fume replacement under steam curing Volumetric changes are considered the main problematic properties that prevent the wide use of RPC. Verifications are required to clarify mixing different quartz powder to quartz sand and its impact on RPC compressive strength by studying its microstructure.
The effect of curing regimes on the mechanical properties, nano-mechanical properties and microstructure of ultra-high performance concrete
2019, Cement and Concrete Research
Citation Excerpt :
The development of dense microstructure with the formation of C-S-H gels contributes to the improvement of mechanical properties. In addition, the mechanical properties improvement of UHPC has indicated heat treatment at 250–300 °C to be the most beneficial curing conditions to achieve higher UHPC compressive strength followed by autoclave, steam, and standard curing [18,19]. But the effects may rely on the mix design of UHPC.To develop high strength UHPC, combined curing conditions have been utilized [4,20–22].
This study addresses the effect of curing regimes on the mechanical properties, hydration and microstructure of ultra-high performance concrete (UHPC). The results demonstrate that the mechanical properties are strengthened by increasing curing temperature, but the flexural/tensile to compressive strength ratio shows an unusual increasing tendency with increasing temperature and compressive strength, which is opposite to normal concrete. The nano-mechanical properties are also enhanced by heat treatment. The ultra-high density phase is dominated hydrates. Microstructure observation indicates that heat treatment promotes the formation of additional hydrates with high-packing density and stiffness such as tobermorite and xonotlite, enhancement of transition zone around steel fiber, quartz and clinker, average chain length of hydrates and pozzolanic reaction between quartz/silica fume and Ca(OH)₂. The evolution of hydrates and microstructure due to curing regimes and the presence of quartz play key roles in controlling the unusual behavior of the strength ratio and improvement of mechanical properties.
An analysis of the steam curing and autoclaving process parameters for reactive powder concretes
2017, Construction and Building Materials
Citation Excerpt :
In autoclaved cementitious materials tobermorite and xonotlite of very well investigated and described structures [10–12] occur as the most common phases. The occurrence of both phases in autoclaved RPC materials was confirmed by a number of researchers [15–18]. However, it should be noted that there are some unfavourable CaO/SiO2 proportions at which crystallization of hydrated calcium silicates leads to formation of such phases as α-C2SH or truscotite causing the deterioration of mechanical properties of cementitious materials [11].
The two different methods of thermal treatment were used when curing reactive powder concretes (RPC), namely low-pressure steam curing and autoclaving. The properties of obtained material were referred to those of materials cured in water at a temperature of 20 °C. The main aim of this study is to verify mechanical properties of RPC without fibres, at variable steaming and autoclaving parameters. The following factors were taken into account: preset time, target temperature and holding time. At the same time by using the techniques of SEM and MIP, changes in microstructure of composites cured at an increasing temperature and different time were observed. After establishing the most favourable heat treatment parameters, their effect on the efficiency of steel fibres of 6 mm long added at amount of 2% by volume was analysed. Compressive strength and three-point flexural strength were tested along with deformability evaluation. The factor having the strongest effect on mechanical properties of RPC under examination was the target temperature of steaming and autoclaving. RPC curing conditions had also a significant impact on post-critical strains in composites containing dispersed reinforcement.
Determination of optimized mix design and curing conditions of reactive powder concrete (RPC)
2016, Construction and Building Materials
Employing such microstructural modification approaches including elimination of coarse particles and utilization of fine silica powders and micro-scale particles such as silica fume (SF) introduce the reactive powder concrete (RPC) as new-arrival generation of cement based materials with superior mechanical properties due to their ultra-dense microstructure. The present study investigates the compressive strength of non-steel microfiber reinforced RPC by utilizing different mix designs under various curing conditions to determine the optimal practical conditions and parameters that would lead to maximum RPC compressive strength. Results revealed that the eight-step procedure employed in this study considerably enhanced the compressive strength of the specimens about 174% as evidenced by the rise in from 85 MPa (28 days) to 233 MPa (13 days). Furthermore, different cure treatment plans were applied and results showed the combined cure treatment, including 3 days of autoclave cure treatment at 125 °C followed by 7 days of heat cure treatment at 220 °C represented more effective performance due to resulted superior mechanical properties at a minimum curing time.

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Short communication29Si NMR study of hydration and pozzolanic reactions in reactive powder concrete (RPC)

Abstract

Cem. Concr. Res.

Short communication
²⁹Si NMR study of hydration and pozzolanic reactions in reactive powder concrete (RPC)