Asphalt rubber (AR), which is prepared by blending crumb rubber and bitumen, provides various advantages, including superior rutting resistance, lower road-tire noise and longer service life. However, contractors have expressed concerns regarding its poor storage stability, which in turn limits its wider application. This study aims to address the storage stability concern by incorporating nano-montmorillonite (nanoclay). Three types of nanoclay were dispersed into hot AR binder by high shear blending. The rheological properties of nanoclay-crumb rubber modifier (CRM)-modified bitumen were evaluated through Superpave performance grade (PG) tests and the storage stability was characterized by measuring the difference in softening points or complex moduli at the top and bottom portions of binders after lab-simulated storage. X-ray diffraction (XRD) evaluation was conducted to observe the variation of nanoclay layer gap distance for mechanism investigation. It was found that all selected nanoclays had insignificant effects on workability, rutting and fatigue properties. The layered nanoclay transformed to intercalated or exfoliated structures after interaction with bitumen fractions, providing superior storage stability. Among the three selected nanoclays, pure montmorillonite with Na+ inorganic group, which has an intermediate hydrophilic property and middle layer gap, showed the most obvious effect on enhancing the storage stability of AR.

Today, more and more studies are devoted to activation of primary components of building materials. This paper is concerned with the viability of activating mineral bonding materials, Portland cement in particular, in the Vortex Layer Machine (VLM) with a purpose of physical modification. By applying modern methods for studying the specific surface, pH change, X‐ray phase and differential‐thermal analysis, and IR spectroscopy, it was found that activation of Portland cement in the VLM constitutes an efficient method for enhancing physical and chemical activity. It was also found that, depending on the content of mineral additives in the VLM, activation of Portland cement leads to significant extension of its specific surface, decrease of particle size, and also to prevalence of processes related to activation of an agent in the surface layer. During activating Portland cement, mineral crystal structure is being destructed, with the most significant changes observed for C3S. Besides, processing Portland cement in the VLM results in polycondensation of SiO4‐tetrahedral units, which reduces the basicity of hydrated calcium silicates during hydration; in the cement stone, ettringite content increases, and so does content of low‐basic hydrated calcium silicates and aluminates, which reinforces strength and chemical resistance of concrete. The acquired results speak for benefits of activating mineral bonding materials in the VLM with the purpose of enhancing physical‐mechanical properties of building materials.

No abstract

Escalating the operational actions in construction demands the development of building materials with improved properties. Today, the nanomodified and nanostructured materials (also called nanocomposites) attract great attention of the scientists all over the world. The successful development of nanocomposites requires simultaneous application of theoretical examination, experimental investigations and numerical studies. In the present work we provide short review of the simulation methods involving particle systems as a materials model and also discuss several results obtained during numerical studies of building materials by means of using such methods. It is noted that neither the single mathematical model, nor the only one simulation method can be used for modeling of building material at all levels of scale (from macroscopic down to nanoscale). However, some models and numerical methods are still quite general. Thus, they can be utilized for modeling a very wide range of phenomena from compaction process at macroscopic level to reinforcement regularities at micro-and nanoscale. The obtained results both offers the insight into regularities of structure forming process and allow to reduce time and cost of the design.

The paper presents the results of a study of the physical-mechanical and operational properties of high-strength lightweight concrete and the influence of nanoscale modifier on these properties. The nano-modifier and its method of application to improve the properties of lightweight concrete with hollow microspheres at 10-25% are proposed. The method to control structure formation processes by the nano-modification is shown. The nanoscale modifier is grafted onto the surface of the hollow filler and interacts with cement and its hydration products (calcium hydroxide). This local activation of the hydration of Portland cement and the formation of an additional amount of calcium hydrosilicates at the phase boundary leads to the increasing of the strength of the concrete. This provides growth of operational properties. The high-strength lightweight concrete with an average density less than 1500 kg/m 3 is characterized by a strength more than 40 MPa (specific strength R sp > 30 MPa). The optimum range of concentrations of the precursor for preparation of nano-modifier is defined to be 1.25 ≤ [Na + ]/[Cl − ] ≤ 2.5. We can conclude that the developed composition has a dense and strong structure which can resist intense cracking. Application of nanoscale modifier enables an increase of the elastic modulus of 13-36% (equal to 6.2-8.5 GPa depending on the average density), a decrease of water absorption (to 1%) and an improvement of the water resistance (coefficient of water resistance is more than 0.95) and freeze-thaw resistance (up to F300). The nano-modified high-strength lightweight concrete has beneficial values of heat-conduction coefficient (0.48-0.70 W/(m Á C)), temperature conductivity coefficient ((3.43-4.04)Á 10 −7 m 2 /s) and specific heat capacity (1080-1175 J/(kg Á C)). It allows us to consider this concrete as a multifunctional material with both structural and thermal insulation properties. K E Y W O R D Snanotechnology, nanoscale modifier, high-strength lightweight concrete, structural lightweight concrete, strength, hollow microspheres | INTRODUCTIONThe application of nano-sized modifiers to improve the quality of building materials has spread in various directions. [1][2][3] The various carbon nanoparticles, nano-oxides, sols and gels have been studied by authors from different countries. [4][5][6][7][8][9] Use of these additives to modify the materials in the entire volume of the structure leads to achievement of desired operational properties in different areas of application. However, some unresolved problems 10,11 still complicate the use of such modifiers in practice (for example, there is an aggregation of powdered carbon nanoparticles). Colloidal solutions are most promising in this area because the particle distributions in volume will depend on the properties of the carrier media, stability of the system and physico-chemical properties of the substance. That is why the resolutions for the identified difficulties are achieved at the design stage of such modifiers when taking into account the ...