Genadijs Sahmenko

Bore-Silicate Glass Waste of Lamp as a Micro-Filler for Concrete

Bore-silicate glass waste of lamp as a micro-filler for concrete Lamp glass rational utilization problem is actually over the world. The possibilities for use lamp bore-silicate glass as concrete micro-filler have been investigated in this work. Tree experimental series was carried out. Experimental standard concrete samples was prepared and tested after the 7, 28, 84 (112) day ageing period in standard condition. The first part of experiments provides using ground glass as cement replacement. Experimental results indicate decreasing in compressive strength when part of cement was replaced by ground glass filler. The second experimental series presents adding glass filler additionally to cement as sand replacement. Experimental results indicate nonessential strength increasing after 7 and 28 days hardening for mix containing 5 … 20 % ground glass by cement. The next stage of investigations provides to compare behavior of glass filler and other traditionally used fine materials, effect of glass additional grinding also was investigated. The experimental results indicate that glass powder additional grinding gives positive effect on strength characteristics. The best compressive strength results (approx. 67 MPa in 28 days and 80 MPa in 112 days) were achieved by using silica fume as micro filler and silica fume combination with additionally ground glass as complex admixture. Concrete mixes containing microsilica and ground bore-silicate glass perform long-term hardening effect, which may be explained by puzzolanic reactions with cement components. Summarizing results of investigation it may be concluded that ground bore-silicate lamp glass succesfully may be applied as microfiller for concrete. In the same time additional investigations on micro filler grading and grinding conditions must be made in future. Obtained concrete durability characteristics also must be investigated.

The Formation of Microstructure in High Strength Concrete Containing Micro and Nanosilica

This article presents the results of microstructural investigation of high strength concrete containing microsilica and nanosilica (amorphous SiO2) as an active pozzolanic admixture. Micro and nanosilica react with calcium hydroxide producing calcium silicate hydrates (C-S-H), thus the voids and pores within concrete are filled and new minerals are formed in the gaps between cement grains and aggregate particles. Unreacted round microsilica and nanosilica particles were registered using SEM even in 6 month old samples. The compressive strength results indicate that concrete still continues to harden after the 28-days of curing.

Properties of High Performance Concrete Containing Waste Glass Micro-Filler

The article discusses possibilities for use fine ground glass obtained from fluorescent lamp utilisation as micro filler in High Performance Concrete (HPC). Investigated mix compositions are based on silica fume (SF) and SF combination with glass powder. Testing results indicates that replacing silica fume by additionally ground fluorescent glass (up to 50%) slightly increasing consumption of water and delaying setting time of cement paste. All HPC mixes with glass powder showing decreased early-age strength and considerable strength gain after long-term hardening. It is concluded, that the best way of glass application in HPC is use fine ground glass powder together with silica fume as complex admixture.

Investigation of influence of nano-reinforcement on the mechanical properties of composite materials

AbstractThe present work studies the possibility to decrease the formation of micro and nano cracks around short fibres in fibre-reinforced concrete (FRC) composite with the help of nano-reinforcement, which is carbon nanotubes, or micro reinforcement, which is carbon short fibres and nano-fillers. Tensile and bending strength of FRC depends on the spatial distribution of fibres inside a material, type of fibre and cement matrix, as well as an effective micromechanical work of each fibre while pulling out of the concrete matrix. Shrinkage stresses, acting in the matrix in the vicinity of a fibre, lead to the formation of micro-cracks. Such micro-cracks were observed experimentally and were investigated numerically performing broad modelling based on the finite element method (FEM). The investigation was focused on the micromechanical behaviour of a single steel fibre in a cement matrix. Numerical modelling results demonstrated a high level of shrinkage overstresses around steel fibres in concrete. The rol...

Effect of Various Additives and Aeration on the Properties of Lightweight Concrete

In the present study the effect of various additives (silica sand, silica fume, zeolite and cenospheres) as well as the aeration on the properties (consistency, density, compressive and bending strength) of lightweight concrete was studied. Density, compressive and bending strength of the lightweight concrete were substantially reduced by replacing silica sand with censopheres or by adding air entraining agent to the grout used for the preparation of the samples. Silica fume and zeolite admixture improved mechanical properties of the samples. Specific compressive strength of the cenospheres containing samples is comparable or even higher than the ones made of the mixes without the cenospheres.

The effect of various pozzolanic additives on the concrete strength index

The concrete industry is searching continuously for new effective mineral additives to improve the concrete properties. Replacing cement with the pozzolanic additives in most cases has resulted not only in positive impact on the environment but also has improved strength and durability of the concrete. Effective pozzolanic additives can be obtained from natural resources such as volcanic ashes, kaolin and other sediments as well as from different production industries that create various by-products with high pozzolanic reactivity. Current research deals with effectiveness evaluation of various mineral additives/wastes, such as coal combustion bottom ash, barley bottom ash, waste glass and metakaolin containing waste as well as calcined illite clays as supplementary cementitious materials, to be used in concrete production as partial cement replacement. Most of the examined materials are used as waste stream materials with potential reactive effect on the concrete. Milling time and fineness of the tested supplementary material has been evaluated and effectiveness was detected. Results indicate that fineness of the tested materials has crucial effect on the concrete compressive strength index. Not in all cases the prolonged milling time can increase fineness and reactivity of the supplementary materials; however the optimal milling time and fineness of the pozolanic additives increased the strength index of concrete up to 1.16 comparing to reference, even in cases when cement was substituted by 20 w%.

Reduction of the capillary water absorption of foamed concrete by using the porous aggregate

The article reports on the research of reduction of the capillary water absorption of foamed concrete (FC) by using the porous aggregate such as the granules of expanded glass (EG) and the cenospheres (CS). The EG granular aggregate is produced by using recycled glass and blowing agents, melted down in high temperature. The unique structure of the EG granules is obtained where the air is kept closed inside the pellet. The use of the porous aggregate in the preparation process of the FC samples provides an opportunity to improve some physical and mechanical properties of the FC, classifying it as a product of high-performance. In this research the FC samples were produced by adding the EG granules and the CS. The capillary water absorption of hardened samples has been verified. The pore size distribution has been determined by microscope. It is a very important characteristic, specifically in the cold climate territories–where temperature often falls below zero degrees. It is necessary to prevent forming of the micro sized pores in the final structure of the material as it reduces its water absorption capacity. In addition, at a below zero temperature water inside these micro sized pores can increase them by expanding the stress on their walls during the freezing process. Research of the capillary water absorption kinetics can be practical for prevision of the FC durability.

Composite bulk Heat Insulation Made of loose Mineral and Organic Aggregate

Abstract The task of building energy-efficiency is getting more important. Every house owner wishes to save up exploitation costs of heating, cooling, hot water production, ventilation, etc. and find cost-effective investments. One of the ways to reduce greenhouse gas emissions (GHGE) is to minimize the heat transfer through the building by insulating it. Loose heat insulation is a good alternative to traditional board insulation, it is simple in use and cost-effective. Main drawback of this insulation is tendency to compact during exploitation. In the frame of this research composite loose heat insulation is elaborated, consisting on porous mineral foamed glass aggregate and local organic fiber materials (hemp and flaxen shives). Composite bulk insulation is an alternative solution which combines heat insulating properties and mechanical stability.