Effect of nanosilica on characterization of Portland cement composite (original) (raw)
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The Effect of Nanosilica on the Mechanical Properties of polymer-Cement Composites (PCC)
Procedia Engineering, 2015
In the last decade nanomaterials due to their unique physical and chemical properties, have attracted the interest of researchers to fabricate new building materials with novel functions. One of the most referred to and used cementitious nanosized materials is nanosilica (nSiO 2). Although the number of publications devoted to the influence of nanosilica on the properties of cementitious composites has increased over the course of the last decade, the field of polymer-cement composites (PCC) has remained under-studied. Therefore, this paper will deal with the potential application and the influence of nanosilica (nSiO 2) on the mechanical properties of PCC. In this study the influence of diameter (100 nm and 250 nm) and quantity (1%, 3%, 5% by weight of cement) of nSiO 2 on the consistency and mechanical properties of polymer-cement mortars (PCC) have been examined. Moreover, the hydration of cement compounds was followed by X-ray diffraction (XRD). Studies have shown that the addition of nanosilica has great potential to accelerate the pozzolanic reaction, thus reacting more with the CH and increasing conversion of C-S-H, and having the potential to improve mechanical properties of PCC. The obstacle overcome is the high water demand of nanosilica particles, leading to significant deterioration of consistency. Finer particles of nSiO 2 seem to be more effective and cause fewer problems with the consistency of fresh mortars.
Strength and microstructure of colloidal nanosilica enhanced cement pastes
2014
The macrolevel properties of concrete; strength and durability are dependent on the hydration of cement. The main products of the chemical reactions of cement clinker with water, are calcium silicate hydrates (C-S-H), calcium aluminate hydrates and calcium hydroxide. C-S-H, the major binding and strengthening factor within the hydrating cement paste, is nanosized. Therefore, it is believed that the addition of nanoparticles can modify the characteristics of the C-S-H in nanoenhanced pastes, inducing subsequent alterations at larger scale phenomena. In this research the addition of nanoparticles of silica, referred to as nanosilica (nS) to blended cement formulations was investigated with the aim of enhancing durability and lowering environmental impact. The hydration products, microstructure and compressive strength of the early and later ages (from 1 day until half a year old) hardened cement paste were compared in a series of cement pastes. The reference paste contained Portland limestone cement and additional limestone (summing up to 60% Portland cement and 40% limestone by mass) and the nS enhanced pastes contained nanosilica at 0.1%, 0.5%, 1% and 1.5% by mass of solids. The water to binder ratio was kept constant at 0.3. The size of nanosilica was confirmed by transmission electron microscopy to be in the order of 8 nm to 50 nm, diameter. Performance evaluation of the pastes, indicated that nS exhibits a pozzolanic behaviour consuming calcium hydroxide to form additional C-S-H. Additionally, for pastes with 40% substitution of cement by limestone, low nS content (0.1% to 0.5%) is favouring strength gain even at later ages. Thermogravimetric analyses and scanning electron microscopy provided a further justification of the above hypothesis. The research reported was part of a much broader research project supported by the EU, and involving industrial and academic partners throughout Europe, to investigate nanotechnology enhanced cements.
The Open Construction and Building Technology Journal, 2022
The development of nanotechnology has made it possible to design new materials and improve existing ones. Regarding new supplementary admixtures for cement-based materials, nanosilica is more advantageous than any other nanomaterial. This is due to its high pozzolanic reactivity, besides its filling and seeding effects, which are a consequence of the higher and more reactive specific surface area of the nanosilica and its amorphous structure. Nonetheless, when used improperly or in an inadequate dosage, such a nanomaterial may negatively affect the cement admixture, compromising both fresh and hardened properties. Hence, it is fundamental to understand the nanosilica's behavior inside the cementitious medium. This review paper is based on recent literature about the incorporation of nanosilica in cementitious materials. The analyses showed that, once incorporated in the cement matrix, nanosilica tends to agglomerate. The behavior of such agglomerates influences both the pozzolanic filling and seeding effects. Therefore, a suitable dispersion of the nanoparticles must be achieved. In this sense, third-generation superplasticizers are used, usually up to 3% of cement mass. The mechanical properties of cement-based materials with nanosilica depend on the amount of nanomaterial and on its specific surface area. There is not an agreement on the optimum dosage of nanosilica, however, percentages up to 5% in cement mass seem to provide a better performance, when compared to greater ones. It is not worthy to use nanosilicas with excessive specific surface area values, because they tend to form large agglomerates, reducing fluidity and compressive strength. Particles with surface areas up to 300 m 2 /g usually present good performance. Nanosilica improves the early age strength and contributes to the pore refinement of cementbased materials. The combination of nanosilica with other nanomaterials or industrial by-products can improve the mixture's performance. Nonetheless, the use of silica nanoparticles with agricultural wastes negatively affects the mechanical properties at early ages.
Impact of Nanosilica in Ordinary Portland Cement over Its Durability and Properties
Cement Industry - Optimization, Characterization and Sustainable Application, 2021
The present examination illustrates the impact on the hardened and fresh cement mortar and cement with the inclusion of nanosilica of size 40 nm in various environmental conditions (UltraTech, India). It is quite notified that an elevation in compressive strength as well as flexural strength along with an improvisation in the performance and life span of cement mortar. The samples of M5 grade blended with a ninety percentage of concrete and remaining with nanosilica was identified to have a finer working elevation in as well as in standards when collated with the conventional cement mortar. The corollary of hardened and fresh cement, strength parameters were looked upon with the aid of XRD (X-ray Diffraction). Also, the SEM (Scanning Electron Microscope) test holds a predominant role in analysis.
Individual and Combined Effect of Nano- and Microsilica on Cement-Based Product
2020
In the cement concrete industry, everybody is concerned about high-strength and high-performance behavior of concrete. These properties were improved using micro- and nano-sized pozzolanic mineral admixtures as stated by various authors. In this paper, author has emphasized mostly on using micro- and nanosilica materials with cement. Literature survey revealed that the most suited mineral admixtures for getting highest behaviors are micro- and nanosilica. Nanotechnology is nowadays a buzzword in everyone’s tips. Nanotechnology in concrete means the addition of nano-sized materials in the range of 1 and 100 nm to improve the behavior of cement and concrete. Micro- and nano-sized silica particles improve the porous behavior of concrete and also produce more calcium silicate hydrate resulting from chemical reaction of nanoparticles and calcium hydroxide. On the other hand, it makes concrete more compact in microstructure point of view, which improves density, strength, and also durabil...
Effect of Partial Substitution of Highly Reactive Mineral Additions by Nanosilica in Cement Pastes
Journal of Materials in Civil Engineering, 2019
The phenomena involved in portland cement hydration and interactions with nanosilica are very complex and not yet fully understood. In addition, few papers have currently proposed to investigate the microstructure and mechanical properties of ternary mixtures using portland cement, colloidal nanosilica, and highly reactive mineral additions. This article investigates, for the first time, the behavior of different highly reactive mineral additions (silica fume and metakaolin) when partially replaced by colloidal nanosilica in the microstructure and hydration of cementitious materials. For the study of the cementitious material microstructures, a Langavant calorimeter, compressive strength, Xray diffraction, thermogravimetry, infrared spectroscopy, and mercury intrusion porosimetry were used. The pastes with a 1% substitution of highly reactive mineral additions by nanosilica showed higher compressive strength and more refined porosity than the pastes with only silica fume or metakaolin. The results show that nanosilica appears to have better synergism with metakaolin than with silica fume.
Research, Society and Development
The use of supplementary nano cementitious material (SNCM) to improve the mechanical properties and durability performances of cementitious composites (cement paste, mortar and concrete) has received remarkable attention in recent studies. The use of nanosilica as SNCM is a consolidated practice in the scientific community. However, recent developments in the synthesis of monodisperse and narrow-size distribution of nanoparticles by functionalization methods provide a significant improvement to the development of silica-group nano composites (among the functional groups: amine, carboxyls and glycol groups), the so-called functionalized nanosilica (FNS). This article aims to raise a literature review on the properties of FNS in cementitious materials and the advanced techniques of nano/micro structural analysis used to characterize cementitious composites containing FNS’s.
CHEMICAL AND PHYSICO-MECHANICAL PROPERTIES OF COMPOSITE CEMENTS CONTAINING MICRO- AND NANO-SILICA
Portland cement is one of the most used materials in the world. Due the environmental problems related to its use, such as CO 2 emission and use of non-renewable raw materials, new materials are being researched. In the recent years, there is a great interest in replacing a long time used materials in concrete structure by nanomaterials (NMs) to produce concrete with novel function and better performance at unprecedented levels. NMs are used either to replace part of cement, producing ecological profile concrete or as admixtures in cement pastes. The great reactivity of NMs is attributed to their high purity and specific surface area. A number of NMs been explored and among of them nanosilica has been used most extensively. This work aims to study, the chemical and physico-mechanical properties of composite cements containing silica fume (SF) and nanosilica (NS). Different cement blends were made from OPC, SF and NS. OPC was substituted with SF up to 15.0 mass, %, then the SF portion was partially replaced by NS (2.0, 4.0 and 6.0 mass, %). The hydration behavior was followed by determination of free lime (FL) and combined water (Wn) contents at different curing ages. The required water for standard consistency (W/C), setting times (IST&FST), bulk density (BD) and compressive strength were also estimated. The hydration products were analyzed using XRD, DTA and SEM techniques. The results showed that, both of SF and NS improve the hydration behavior and physico-mechanical properties of composite cements. But, NS possesses higher improvement level than SF. This is due to that, both of them behave not only as filler to improve the microstructure, but also as activator to promote pozzolanic reaction, which enhances the formation of excessive hydration products. The higher beneficial role of NS is mainly due to its higher surface area, filling effect and pozzolanic activity in comparison with SF. The composite cement containing 85.0 % OPC, 11.0 % SF and 4.0 % NS gave the optimum mechanical properties at all ages of hydration.
Advances in Applied Ceramics, 2010
This paper reports the effects of nanosilica (nS), microsilica (silica fume, SF) and their simultaneous use (nSzSF) on ''both'' the microstructure of cement pastes and the mechanical properties of mortars. After water curing at 21uC for 7, 28 and 90 days, samples with water/binder w/b ratio of 0?35 were characterised by thermogravimetric analysis, X-ray diffraction, scanning electron microscopy and compressive strength test. Single or mixed mineral additions did not generate ''any'' distinct hydration phases compared to the reference material without additives. A decrease in the calcium hydroxide contents in later curing ages indicated a pozzolanic effect of nS and SF. The chemical action promoted by nS together with the physical effect due to the small particle size distribution given by SF result in higher compressive strength and better hardened properties, suggesting the synergistic action of nSzSF compared with single additions.