Additive manufacturing (AM), also referred as 3D printing, is a technology that enables building automated three-dimensional objects in a layer-by-layer manner. AM of cement-based and alkali-activated composites has gathered attention over the last decade and is one of the most rapidly developing civil engineering fields. Development of proper mixture compositions which are suitable in fresh and hardened state is one of the key challenges of AM technology in construction. As the behaviour of cement-based materials (CBM) and alkali-activated materials (AAM) is determined by chemical and physical processes at the nano-level, incorporation of nano- and micro-sized admixtures has great influence on the performance of printable composites. These modifications are attributed to the unique reactivity of nanoparticles associated with their small size and large surface area. This review paper summarizes recent developments in the application of nano- and micro-particles on 3D printable cementitious composites and how they influence the performance of 3D-printed construction materials. The research progress on nano-engineered CBM and AAM is reviewed from the view of fresh and hardened properties. Moreover, comparison between nano- and micro-sized admixtures including nanosilica, graphene-based materials, and clay nanoparticles as well as chemical admixtures such as viscosity-modifying admixtures and superplasticizers is presented. Finally, the existing problems in current research and future perspectives are summarized. This review provides useful recommendations toward the significant influence of nano- and micro-sized admixtures on the performance of 3D printable CBMs.

Sustainable development depends on a consistency of interests, social, ecological and economic, and that the interests are evaluated in a balanced manner. In order to reduce CO₂ emissions, the conception of decreasing clinker factor and increasing the role of supplementary cementitious materials (SCMs) in the cementitious materials has high economical and environmental efficiency. The performance of clinkerefficient blended cements with supplementary cementitious materials were examined. The influence of superfine zeolite with increased surface energy on the physical and chemical properties of low-carbon blended cements is shown. Increasing the dispersion of cementitious materials contributes to the growth of their strength activity index due to compaction of cement matrix and pozzolanic reactions in unclincker part. In consequence of the early structure formation and the directed formation of the microstructure of the cement matrix is solving the problem of obtaining clinker-efficient concretes. Shown that low-carbon blended cements with high volume of SCMs are suitable, in principle, for producing structural concretes.

Research of nanomodified portland cement compositions with high early age strength

It is shown that high operational reliability of structural materials, in particular at high temperatures, is achieved through the use of ultra-high strength cement composites. Studies of various types of Portland cements with mineral additives of the CEM II/A type have established that a stone based on Portland cement with superzeolite is the most resistant to high temperatures. It has been proven that due to the "self-autoclaving" effect, the strength of a stone based on CEM II/A-P 42.5 R is 1.2–1.3 times higher than a stone based on other types of CEM II/A. To obtain fast-hardening cement composites, a nanotechnological approach based on the use of sol-gel technology has been implemented. Using the methods of IR spectroscopy, electron microscopy, the fact of obtaining, by the chemical method of synthesis, an alkaline nanomodifier N-C-S-H-PCE, which is a nano–liquid based on nano-core seeds of sodium/calcium hydrosilicates, has been proved. It has been confirmed that the introduction of the alkaline nanomodifier N-C-S-H-PCE provides a significant intensification of the early structure formation processes in the paste based on Portland cement with superzeolite (after 12 hours, 24 hours and 28 days, the strength is 16.9; 30.5 and 104.1 MPa). It has been established that the complex combination of Portland cement with superzeolite, corundum aggregate, basalt fiber and alkaline nanomodifier provides rapid-hardening of ultra-high strength cement composites (T=400 °C) with improved operational properties. Thus, there is reason to assert the feasibility of developing rapid-hardening ultra-high strength cementitious composites. This solves the problems associated with the need to increase their early strength and performance. As a result, it is possible to carry out repair work to protect equipment from abrasive wear at elevated temperatures

The use of lightweight concrete (LWC) for structural and non-structural applications has attracted great interest in recent years. The main benefits include reduced deadload of structural elements and generally lower production and transportation costs. However, a decrease in concrete density often leads to a decrease in strength and durability. Typically, concretes are mostly modified with mineral additives such as silica fume or fly ash. Because of the recent developments in nanotechnology, research attention has turned to the possibility of improving concrete properties with nanomaterials, i.e., nano-SiO₂. However, there are still certain issues with the dosage and efficiency of nanomaterials. Therefore, in order to establish the current state of knowledge in this field, this review gathers most recent results about the performance of LWC modified with nanomaterials. The review is divided into sections about the influence of nanoparticles on the fresh properties of concrete and their influence on the mechanical and durability characteristics. The paper studies in depth the most common approach to nanomaterials in concrete technology and proposes areas for further development.