Abstract The paper addresses the criteria ensuring a sustainable structure and efficiency of thermal insulation straw-boon slabs in full-scale conditions. Sorption humidity of heat insulator and conditions for fungus build-up on the surface of plant-based filler have been studied. Additives providing high water resistance of silicate glass used as the binder for thermal insulation material have been determined. Tests considering an array of technological parameters and fire behavior of straw-boon slabs confirmed a sustainable structure in the process of installation of thermal insulation material and in case of fire.
Abstract The article aims to present a research into the impact of dosage and effectiveness of commonly used plasticizing admixtures. More specifically, it focuses on rheological properties of the cement pastes (yield stresses and plastic viscosities) of different testing times (from 0 min to 90 min after mixing). The following materials were used in the study: Portland cement CEM I 42.5 R, plasticizer P (ligno-sulphonates based), superplasticizer SP1 (modified acrylic polymer based), superplasticizer SP2 (polycarboxylate esters based) and water. Experiments were carried out using rotational rheometer Rheotest RN4.1 with coaxial cylinders. It was observed that larger dosage of SP1 (0.6–1.2 %) results in slower increase in plasticizing effects until the 90 min margin. In conclusion, from the start of mixing until the 90 min margin, the best plasticizing effect and its retention are achieved by superplasticizer SP2. Recommended SP2 dosage varies within the range of 0.6 % to 0.8 %.
Abstract The research investigation was carried out to determine the effect of different modes of continuity of tension reinforcement bars on the flexural strength of reinforced concrete beams. Nine (9) full size beams (2150 mm × 250 mm × 180 mm) were cast with 2 numbers of 16 mm diameter high yield bars in tension and 10 mm diameter high yield stirrups at 100 mm centres at the shear spans. Three (3) beams each were cast with full length bars (reference), lap-spliced bars and butt-welded reinforcement bars in tension. Twenty-seven (27) 150 mm cubes were also cast to monitor concrete strength. The beams and cubes were cured for twenty-eight (28) days and tested in flexure under four points bending system and in compression respectively. The test results showed that full length bars, lap-spliced and butt-welded bars had an average moment capacity of 25.54 kN·m, 19.16 kN·m and 10.64 kN·m respectively. Lap-spliced beam gave a higher moment of resistance compared to the beams with butt welded steel reinforcing bars. The average midspan deflection of butt welded reinforcement was smaller than that of in the beam with lap spliced type of continuity. It was concluded that continuity using lap spliced bars in tension is more effective and efficient than butt welded continuity. 58.34 %, 25.00 % of the moment capacity of beams with full length reinforcement was lost by using butt weld, without a coupler, and lap spliced bars, respectively.
Abstract This paper reports the effect of transverse reinforcement on tensile reinforcement splice strength of epoxy coated reinforcing bars. Thirty six (36) full size beams of varying lengths and sectional dimensions with lap spliced bars in constant moment region were cast and tested in a four point bending system. The beams were cast with three high yield diameter bars, namely 16 mm, 20 mm and 28 mm. 8 mm and 10 mm diameter high yield stirrups were introduced over the lap in an attempt to study the effect of stirrups on bond performance of epoxy coated reinforcing bars. The ultimate moment from the tests were used to determine the stress developed in the steel rods. The ratios of the test bond stresses and bond stress values using the tensile reinforcement yield stress τt/τy were used for comparison of the parameter under investigation. Transverse reinforcement was found to increase the splice strength of epoxy coated reinforcing bars and the larger the diameter of stirrup the better the improvement of the bond efficiency.
Abstract Granite rubble is one of the most frequently used aggregates in concrete manufacturing. Granite rubble is considered to be a non-reactive aggregate, however, depending on the quarry, granite may have various impurities including harmful minerals containing active SiO2. The alkali – silica reaction is among the chemical reactions that have a significant effect on the durability of concrete. During the alkali – silica reaction certain forms of silica present in concrete aggregates react with high alkali content leading to formation of hygroscopic gel that expands in humid environment and slowly, although strongly enough degrades concrete structures. Concrete rubble of 3 different fractions was used for the test: 2/8 (Mix D); 11/16 (Mix E); 5/11 (Mix G). The tests revealed that granite rubble used for the tests contained few reactive rocks containing amorphous silica because after 14 days the expansion did not exceed 0.1 % ((D Mix expanded by 0.059 %, E Mix expanded by 0.066 %, G Mix expanded by 0.079 %) according to RILEM AAR-2 test method. After 56 days of testing none of the test specimens demonstrated significant micro-cracking and scaling specific to alkali corrosion; only gel deposits on the surface were observed.
Abstract Microalgae biomass production is recognized as a cost-effective and sustainable alternative to currently used approaches to tertiary wastewater treatment. However, such limitations, as algae biomass separation from water, process efficiency in cold climate and the algae biomass ability to reduce micropollutant content in wastewater hamper this method from full-scale use. This review discusses the identified drawbacks and offers possible improvements and modifications for wastewater phycobioremediation.
Abstract The article presents research results on a thermal insulation material made of low-moor peat. A model based on three components, including peat binder, frame component (wooden aggregate) and additives, was developed in the framework of this study. The conducted research showed that by grinding low-moor peat in water until the particle size is 2–5 mkm increased peat cohesion strength with wooden aggregate 2.5 to 2.7 times as well as increased the compressive strength of peat binder 5.0 to 5.5 times. Optimal parameters of strength and density in the wood peat composition with discontinuous granulometry wooden aggregate were achieved by using two fraction wood filler with fractions 2.5 mm ... 1.25 mm and 0.63 mm ... 0.315 mm in the proportion 50:50 and 60:40. Introducing anionic surfactants and foam forming non-ionic surfactants with neutral reaction against the surface of the peat and wood filler allows to reduce the average density up to 210–220 kg/m3, thus maintaining the required strength, and to reduce the coefficient of thermal conduction to 0.046 W/mK.
Abstract Materials used for the study: Portland cement CEM I 42.5 R, 4/16 gravel, 0/4 sand. The fine aggregate in four concrete mixtures was substituted with steel cord scrap added at 1.5 %, 3.0 % and 4.5 %. Water absorption and compressive strength was measured in concrete specimens after 7 and 28 days of curing. Total, closed and open porosity was measured in the modified concrete specimens. The tests of predicted freeze-thaw cycles were done. Test results showed that the substitution of fine aggregate with steel cord scrap results in lower water absorption and higher compressive strength in the modified concrete specimens. The porosity parameters have also changed: the closed porosity has increased and consequently the freeze-thaw resistance of modified concrete has improved.
Abstract Concrete is a composite material composed of a binder, aggregates, water and additives. Mixing of cement with water results in a number of chemical reactions known as cement hydration. Heating of concrete results in dehydration processes of cement minerals and new hydration products, which disintegrate the microstructure of concrete. This article reviews results of research conducted with Portland and alumina cement with conventional and refractory concrete aggregates. In civic buildings such common fillers as gravel, granite, dolomite or expanded clay are usually used. It is important to point out the differences between fillers because they constitute the majority of the concrete volume.
Abstract Crack formation during exploitation considerably decreases durability of concrete structures. Capillary hydro insulation is an integral crystalline waterproofing system ensuing filling of micro cracks, pores and capillaries with an insoluble crystalline formation. In order to evaluate self-healing effect of this system, fiber concrete beams were initially pre-cracked, then treated with capillary insulation and repeatedly tested under bending. Water permeability and frost resistance tests were also realized in order to evaluate long-term performance of the capillary insulation.
This research aims to investigate the effect of introducing different mineral admixtures on the mechanical properties of concrete. The research is focused on optimizing the properties of fresh and hardened concrete, looking in particular at how factors such as slump, unit weight, air entrancement, compressive strength, tensile strength, flexural strength and modulus of elasticity are affected by different mineral admixtures in a concrete mix. Different mineral admixtures are used, namely silica fume, limestone and ultra-fine gypsum, and for the tests each mineral admixture replaced 25 % of the cement. The paper also compares the performance of the fresh and hardened properties of concrete.
Abstract The aim of this study is to obtain high performance boron containing material with sufficient carrying capacity with increased porosity and lower density at the same time. The influence of the different concentrations of Al-W-B powder on the properties of the fresh and hardened HPC was investigated. In the concrete mix design, the allite containing White Portland cement CEM I 52,5 R, granite stone, sand, microsilica, on polycarboxylates based super plasticizer and Al-W-B powder were used. As a source of boron composite material (CM), previously grinded powder containing boron-tungsten fiber and aluminium matrix (CM Al-W-B) was used. Grinding was used for processing of CM Al-W-B powder.
Cement as the binding agent in the production of concrete can be replaced with active mineral admixtures. Biofuel combustion fly ash is one of such admixtures. Materials used for the study: Portland cement CEM I 42.5 R, sand of 0/4 fraction, gravel of 4/16 fraction, biofuel fly ash, superplasticizer, water. Six compositions of concrete were designed by replacing 0%, 5%, 10%, 15% 20%, and 25% of cement with biofuel fly ash. The article analyses the effect of biofuel fly ash content on the properties of concrete. The tests revealed that the increase of biofuel fly ash content up to 20% increases concrete density and compressive strength after 7 and 28 days of curing and decreases water absorption, with corrected water content by using plasticizing admixture. It was found that concrete where 20% of cement is replaced by biofuel ash has higher frost resistance.
Abstract This article analyzes trends of the total final energy consumption in sectors of building materials, residential, and transport industry in Algeria. The total final energy by sector and type of fuel is analyzed. The evolution of the total energy intensity and the impact of energy consumption on the environment are discussed. Consumption per capita in Algeria is 1,058.0 kg of oil equivalent per person, while in Morocco, the country with almost the same number of inhabitants it is 458 Kgoe and in Tunisia it is 843 Kgoe. The total emission of gases is equal to 46 million Tons of CO2, with an average of 3 TECO2 / TOE.
