The Synergic Effects of Nano Additives on the Mechanical Properties of Green Lightweight Concrete

Concrete materials have been commonly used in building and construction industries. However, the process of cement manufacture has long been connected with high consumption of energy and adverse environmental impacts. In this study, in order to produce innovative green concrete material that consumes lower energy, resources and is more eco-friendly, industrial waste by-product fly ash cenosphere has been utilized as lightweight aggregate to replace cement by 73.3 %. In most conducted researches regarding lightweight concrete (LWC) with cenospheres, attempts have been made to improve its physicomechanical properties by the inclusion of fibre materials, while limited studies have been performed to investigate the effects of nano additives, especially the synergic influence of them. Therefore, carbon nanotubes (CNTs) with the dosage of 0.05 %, 0.15 %, 0.45 % and nano silica (NS) with the content of 0.2 %, 0.6 %, 1.0 % by cement weight were used in this study as reinforcing fillers on the LWC. Experiments including flexural strength test, compressive strength test, water absorption and thermogravimetric analysis were carried out to evaluate the mechanical behaviors and the hydration characteristics of the produced LWC. Based on the experimental outcomes, the incorporation of CNTs and NS can effectively enhance both the flexural and compressive strength and reduce the absorbed water weight. The results from the thermogravimetric analysis reveal that the binary presence of CNTs and NS exerts positive impacts on the cement hydration reaction

EXPERIENCE OF APPLICATION HIGH PERFORMANCE CEMENT COMPOSITES FOR CREATING DURABLE SCULPTURAL ELEMENTS

Traditionally, sculptural and decorative elements of building facades are created from mortar mixes based on lime, gypsum or Portland cement. Generally these materials have porous and permeable structure, which determines their accelerated degradation, especially in the aggressive environment of modern cities. High performance cement composites (HPCC) have been considered for production and restoration of sculptural elements in historical buildings. For this purpose, fine-graded, multi-component and highly workable mixes were elaborated. Mix compositions were modified with micro-fillers, plasticizing and stabilizing admixtures, as well as fibers to improve material ductility and control shrinkage cracking. Basic mechanical properties and durability (such as water absorption, frost resistance) were determined and two types of HPCC were compared (>50 MPa: HPCC and >120 MPa: UHPCC). It has been confirmed that cement composite mixes are characterized by self-consolidating effect, high compressive strength, extremely high resistance versus freezing and thawing cycles and low water absorption. Surface quality was evaluated and initial water absorption (tube tests) were performed for laboratory samples and real sculptural elements after 5 years of exploitation. The results confirmed good potential for using HPCC for creating more attractive and durable architectural shapes and façade elements compared to elements made using traditional cement and lime mortar

Creep Behaviour of Concrete With Glass Waste Microfiller

Every year there are several hundred tons of waste glass produced in Latvia. Glass can be re-used as a fine raw material and it presents a possibility to save natural, non-renewable materials. The use of glass powder in concrete production can make the construction industry more environmentally friendly. This paper examines the possibility of using glass powder as cement replacement in a new type of concrete. In the experiment, cement was partially (20% and 40%) replaced with glass powder. The long-term deformation (creep) of this new concrete was monitored. Three different concrete mixtures were batched. Specimens of 20% and 40% cement replacement were compared with the specimens made of standard concrete. The samples were tested in two extreme conditions: in one case they were kept in 100% humidity ensured by preventing the desiccation of the concrete, and in the other case samples were air-dried by preventing them from becoming wet. Compression strength and modulus of elasticity of 7 and 28 days old cubic samples was determined

PRODUCTION OF MAGNESIUM BINDER COMPOSITES USING LOCAL RAW MATERIALS AND TECHNOGENIC PRODUCTS

Building sector is known as one of the biggest polluters, causing environmental pollution and carbon dioxide emissions, most of which are generated during the production process of building materials. Therefore, researchers and manufacturers have become increasingly interested in environmentally friendly materials with low energy consumption. Magnesium based cements are being studied as an alternative to a widespread material as Portland cement, thus reducing the temperature required for calcination. During this research, magnesium binder-based composites using two types of magnesium (local dolomite waste material and caustic magnesia) were produced. Within the framework of this study, several regimes of thermal treatment were used to produce low carbon dioxide and environmentally friendly magnesium binder composites. Physical, mechanical and thermal properties of obtained specimens were tested.

Fabrication of porous ceramics as clay/glass composite

Nowadays porous ceramics are widely researched, becoming an increasingly marketable material in the world, mainly due to the wide possibilities of usage in different technical and technology industries. Porous ceramics are successfully used in the filtration and has a high potential of usage also in the production of heat insulation materials thus obtaining the material which combine high resistance that can compete with other heat insulation and constructive materials.Article reports a study of porous ceramics, which are produced using foamglass pellets as melting fillers, despite the fact that these additives are not frequently used as filler in traditional ceramic materials. The basis of this method is mixing fire resistant material with hard and melting substance.For the production of porous ceramics clay, hard filler, water and various sized foamglass pellets were used, thus allowing to determine optimal size of melting filler and thereby ensuring the necessary physical and mechanical properties of the obtained porous ceramic samples and required amount, size and division of pores.  Compressive strength tests were performed, as well as density and water absorption of the samples was determined.Obtained results of the study shows that ceramic materials, obtained within the research, have great potential of application for load-bearing constructions as constructive building materials, as well as insulation materials. Production of porous ceramics materials, where foamglass pellets are used as melting filler, allows to produce more effective ceramics, creating high added value for the final product.

THERMAL CONDUCTIVITY AND FROST RESISTANCE OF FOAMED CONCRETE WITH POROUS AGGREGATE

The paper reports a study, which was carried out to examine thermal and frost resistance properties of foamed concrete (FC) with porous aggregate (expanded glass (EG) granules and cenospheres). By adding lightweight and porous aggregate to the FC mixture, it is possible to improve important physical, mechanical, and thermal properties of the prepared FC specimens. In the framework of this study the coefficient of thermal conductivity and frost resistance of hardened FC samples were determined. The structure of FC matrix and used aggregates were characterised by using a method of optical microscopy

Influence of the carbonate-free clay calcination temperature and curing conditions on the properties of alkali-activated mortar

Alkali-activated materials (AAMs) are one of the most perspective alternatives to the traditional Portland cement based materials. AAMs could reduce the environmental pollution and greenhouse gas emission due to the lower heat consumption in production (up to 80% compared to the ordinary Portland cement). In the current research alkali-activated mortar was developed from the locally available low-carbonate Illite clay. Experimental work consisted of Illite clay calcination at different temperatures and regimes (from 500-800°C) and incorporation of the obtained material into the mixture of alkali-activated mortar. Four curing regimes were applied to alkali-activated mortar. The results indicate that hardened mortar properties are mainly affected by curing temperature and regime and the compressive strength up to 28.8MPa could be achieved for the mortar samples aged 2 months

RESEARCH ON PROPERTIES OF COMPOSITES BASED ON MAGNESIUM BINDERS

The research is devoted to composites based on magnesium binders, which is very perspective building material in the modern construction industry. Magnesium based binders have better compatibility with organic fillers comparing to traditionally lime binder cement [1]. In this investigation two magnesium-based binders are used, such as magnesium chloride and magnesium sulphate. The aim of this study is to investigate the physical, mechanical and durability properties of composites based on magnesium binders, such as density, compressive strength, thermal conductivity and capillary water absorption, and to obtain magnesium binder that could be used to produce foamed concrete. This can be done by improving the composition of the mixture. In this framework properties of magnesium binders are analysed and how these binders can affect to the properties of magnesium based composites

The Effect of Heat Treatment on the Properties of Ultra High Strength Concrete

The influence of heat treatment during curing process of ultra high strength concrete (UHSC) was researched. Four different heat treatment temperatures ranging from 50 to 200 °C were studied and compared to the reference temperature regime (20 °C).  Two series of heat treatment were applied: (a) at the early age of UHSC (3 days) and (b) after 27 days of standard curing regime in water at 20 °C. Concrete compressive strength was tested at the early age (4 days) and at the age of 28 days. The water absorption and water penetration under pressure were tested for heat treated and untreated UHSC specimens. SEM and XRD investigations of the studied samples were performed. UHSC with the strength of 123 MPa at the age of 28 days was tested at the standard curing conditions. Results indicate that early age curing at elevated temperature increases early compressive strength from 123 to 189% while at the age of 28 days the compressive strength was only 95 to 117% from reference and depends on the heat treatment regime. The heat treatment of UHSC at the age of 27 days was beneficial with regard to the strength development. Heat-treated UHSC provided compressive strength gain from 112 to 124% from reference. The water absorption for all UHSC specimens was from 2.6 to 3.2 wt.% and it was not affected by the heat treatment. The calcite was detected with XRD in heat treated UHSC samples which indicates the carbonization of Portlandite. This could explain the strength gain of heat-treated samples and the reason for slow compressive strength increase in the case of early heat treatment application. SEM images reveal dense structure and unreacted silica fume particles. The early heat treatment initiated high early strength but the strength of concrete reduced at the age of 28 days comparing to the early strength; therefore late heat application was beneficial for strength gain of the UHSC

Sand Partial and Full Replacement in Concrete Composite with Rubber Crumbs

The objective of the research on rubberized concrete that substitutes sand fillers with rubber crumbs by volume or weight is to identify ways to utilize discarded rubber tires and improve the building industry’s sustainability. The research indicates that substituting sand fillers with rubber crumbs can have a substantial effect on the concrete’s physical and mechanical qualities. Significant decreases in flexural strength and compressive strength are observed when 100 % of the sand is replaced with rubber crumbs, showing that the attributes of rubber concrete are weaker than those of conventional concrete. Note that the precise mix design and proportion of rubber crumb replacement will alter the qualities of rubber concrete. Therefore, it is essential to conduct proper laboratory testing and trial mixing in order to optimize the mix design and determine the replacement % that would deliver the needed qualities and match the standards. The flexural strength of the reference sample was 2.7 MPa and its compressive strength was 57.7 MPa, compared to the compressive strength of the sample in which 100 % of the sand was replaced with rubber crumbs. The flexural strength of sr100 was 0.39 MPa and its compressive strength was 4.4 MPa. It is also important to note that rubberized concrete may still have some advantages over ordinary concrete, such as enhanced sound insulation, thermal insulation, and chloride ion penetration resistance. These characteristics may make it useful for applications including sound barriers, underground constructions, and marine structures