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 ...

No abstract

For the purpose of fire safe construction it is necessary to develop and investigate effects of fillers to flammability of building materials, including composite materials with polymer matrix. In present work we demonstrate the results of such investigation. We have examined influence of chemical composition, amount of mineral fillers to flammability, smoke-forming ability and limiting oxygen index of building materials based on different polymer binders. The experimental data indicate that the main parameter which determines the influence of mineral fillers on the flammability of composites is a specific heat absorbed by the filler. The dependence between limiting oxygen index and specific heat of mineral fillers is revealed for composites with epoxy matrices. This dependence is simple and beneficial for practical use.

No abstract

No abstract

The equipment for plasma processing with specific area of application – production of building materials – is proposed. For the proposed equipment the examination of possibilities is carried out. It was shown that plasma processing significantly affects the components of concrete – portland cement, fine filler (silica) and water. The treatment of portland cement leads to crystalline hydrate shell destruction and removal of chemically bound water. This, in turn, leads to the increase of strength by 15-20%. Plasma processing significantly changes the state of the fine filler. The total surface area of such a filler decreases due to flash-off effects. In Raman spectra all strong peaks of crystalline quartz disappear, and amorphization of quartz takes place after processing. If both cement and fine filler are processed than strength can be increased by 30%. By means of plasma processing of water it is possible not only to enlarge the strength of mortar, but also to increase the rate of curing. The improvement of properties is probably due to changes of hydration completeness in case of activated water.