Higher Compressive Strength Values Research Articles

Cement slurries with the addition of carbon nanotubes for sealing boreholes with high temperature and reservoir pressure (150°C, 90 MPa)

The article presents the results of the influence of carbon nanotubes on the mechanical parameters of cement stones under high temperature and pressure conditions (150°C, 90 MPa). The tests used multi-walled carbon nanotubes (MWCNTs) with an external diameter of 10–20 nm and a length of 10–30 μm. Cement slurries contained 0.1% of CNTs bwoc (by the weight of cement). Laboratory tests of cement slurries were carried out at the Oil and Gas Institute – National Research Institute. The tests were carried out under conditions of increased pressure and temperature at 150°C, 90 MPa. Cement slurries were prepared on the basis of class G drilling cement. Developing recipes were guided by the requirements to be met by cement slurry for the cementing of casing in the conditions of high temperature and reservoir pressures. The densities of tested slurries ranged from 1900 kg/m3 to 2250 kg/m3 (slurries with the addition of hematite). The cement slurries were tested for density, fluidity, rheological parameters, filtration and thickening time. Compressive strength tests and measuring adhesion were carried out after 2, 7, 14 and 28 days. Cement slurry recipes with very good technological parameters were developed and after curing (after 28 days of hydration) had very high values of compressive strength, reaching up to 45 MPa. Cements were characterized by high values of adhesion to pipes reaching up 7 MPa after 28 days. The research showed significant information about possible applications of carbon nanotubes to modify the cement slurry under conditions of high temperature and pressure. The conducted tests confirmed that the addition of even small amounts of CNTs improves the mechanical parameters of the cement stone compared to the base sample without such addition, and also reduces the thickening time of cement slurries and reduces filtration. It is investigated that CNTs addition increases the viscosity and yield point of cement slurry. As a result, slurries with the addition of MWCNTs will more effectively displace the mud from the borehole and significantly affect the quality of cementation.

Investigations on Improving the Compressive Strength of Sand Column with Cement Grout and Chemical Admixture

Grouting is one of the most commonly adopted technique for soil improvement and strengthening. Adding super plasticizers, accelerators, antifreezes, air entraining agent improves the performance of the cement grout. The performance of the grout while injecting in the sand column mainly depends on its fluidity property. Keeping it in mind about the water cement ratio, the strength of the sand column is studied in two sets of experiments one by sand column with cement grout only and another set by sand column with cement grout added with super plasticizers by varying the water cement ratios. Strength parameters like angle of internal friction and cohesion were obtained be direct shear test and unconfined compressive strength test on the specimens by varying the water content. An increase of 15.2kPa to 60.33 kPa was observed in the cohesion value for specimens with 10% water content and 13.8 kpa to 47.2kPa cohesion value observed in the specimens with 20% water content. The angle of internal friction was decreased from 360 to 160 for 10% water content whereas 300 to 100 for 20% water content. A series of experiments were conducted on the sand column grouted with cement and for different water cement ratios as 1.5, 2.0 and 2.5. Another set of experiments were repeated by adding 2%super plasticizer Sulphonated Melamine Formaldehyde (SMF). The experiment results revealed that at lower water cement ratio higher value of compressive strength was observed. It was also observed that the strength increases with curing period.

Study on the feasibility of using agricultural waste in the production of concrete blocks

The construction industry demands a huge extraction of natural resources along with ample energy consumption; hence the search for new technologies is essential to minimize environmental impacts. The incorporation of natural by-products as reinforcement elements in cement matrix composites production has been studied as an alternative to reduce the use of non-renewable raw materials. The most common natural by-products in Brazil are coffee husk and sugarcane bagasse, which, despite their use by some industries, have yet large non-used amounts, needing adequate disposal of and new ways to add value to waste. This work aimed at evaluating the feasibility of producing concrete blocks partially replacing the crushed stones by sugarcane bagasse and coffee husk agricultural waste. For each residue, the replacement percentages of 2.5%, 5%, 7.5% and 10% (V/V) were evaluated (separately), in addition to a formulation without the use of agricultural residues. Agricultural waste was treated for extractive removal and later evaluated based on their morphological, chemical and physical characterization. The mass mix used was 20: 100: 170: 17.05 (cement: sand: crushed stone: water). The blocks were evaluated for their bulk density, water absorption, compressive strength, thermal and microstructure properties. Agricultural waste used as reinforcement improved physical, mechanical and thermal properties of concrete blocks. Sugarcane bagasse showed a greater potential for its use as reinforcement in concrete blocks than coffee husk. The formulation using 5% sugarcane bagasse offered the best results, which allowed the blocks to present the lowest water absorption values and the highest compressive strength values, as well as being one of the best treatments when evaluating thermal properties, meeting all the commercialization standards criteria.

Effect of Temperature on the Mechanical Properties of Unsaturated Polyester Reinforced with Fibers and Nanoparticles

A composite material is a material that consists of a matrix (base phase) and a stiffener (reinforcement) that combined together to build up a structural unit. Reinforcement material form may be fibers, flakes or as a particle. In the current paper, unsaturated polyester resin (UP) was used as a base material, Sisal fibers (SF), glass fibers (GF) and Silica dioxide (SiO2) particles were performed as a reinforcing material. Three composite types were prepared: (C1) UP only, (C2) UP reinforced with 15% SF and 15% GF, and (C3) UP reinforced with 15% SF and 15% SiO2 to investigate the effect of reinforcement type on some mechanical properties such as elastic modulus, compressive strength, hardness and impact toughness with various temperatures. The experimental results showed that the mechanical properties of composite materials were improved by using reinforcement with fibers and nanoparticles. The high values of elasticity, hardness and toughness were obtained with the specimen C2 composite. While the highest values of compressive strength were obtained with the specimen C3. On the other hand, the modulus of elasticity, compressive strength and hardness were decreased with increasing of temperature values with various percentages. Other clockwise, the toughness values were increased

Effect of Refuse Derived Fuel Ash on the Hydration Characteristics of Portland cement

The use of alternative fuels in Portland cement manufacturing reduces the amount of emissions such as CO2 and NOX gases. Also, it causes a considerable energy cost reduction. In addition, the use of alternative fuel has a positive impact on environment as a result of reduction of solid waste disposal. Therefore, the aim of this work is to investigate the effect of residual ashes produced from using RDF solid waste as biofuel in Portland cement manufacture on its properties. The solid waste used in this study is refuse derived fuel (RDF) mainly from municipal waste. The effect of adding different ratios of the ash, produced after burning such solid waste, to Portland cement on its hydration characteristics was investigated. This is done through the determination of standard water of consistency, initial and final setting times, compressive strength, chemically combined water content as well as the phase composition of the hydration products via the XRD examination. The ratios of ash used were: 0.0, 0.5, 1.0, 1.5 and 2.0% by weight of Portland cement. The samples with RDF ash showed relatively high values of compressive strength compared to blank sample at early ages of hydration up to 7 days.

Mechanical Behavior of Hydroxyapatite-Chitosan Composite: Effect of Processing Parameters

Three-dimensional hydroxyapatite-chitosan (HA-CS) composites were formulated via solid-liquid technic and freeze-drying. The prepared composites had an apatitic nature, which was demonstrated by X-ray diffraction and Infrared spectroscopy analyses. The impact of the solid/liquid (S/L) ratio and the content and the molecular weight of the polymer on the composite mechanical strength was investigated. An increase in the S/L ratio from 0.5 to 1 resulted in an increase in the compressive strength for HA-CSL (CS low molecular weight: CSL) from 0.08 ± 0.02 to 1.95 ± 0.39 MPa and from 0.3 ± 0.06 to 2.40 ± 0.51 MPa for the HA-CSM (CS medium molecular weight: CSM). Moreover, the increase in the amount (1 to 5 wt%) and the molecular weight of the polymer increased the mechanical strength of the composite. The highest compressive strength value (up to 2.40 ± 0.51 MPa) was obtained for HA-CSM (5 wt% of CS) formulated at an S/L of 1. The dissolution tests of the HA-CS composites confirmed their cohesion and mechanical stability in an aqueous solution. Both polymer and apatite are assumed to work together, giving the synergism needed to make effective cylindrical composites, and could serve as a promising candidate for bone repair in the orthopedic field.

Influence of carbon nanotubes (CNTs) on the mechanical parameters of cement stones under HPHT conditions

The article presents the results of testing the influence of carbon nanotubes on the mechanical parameters of cement stones under HPHT conditions. Multi-walled carbon nanotubes (MWCNTs) with an external diameter of 10–20 nm and a length of 10–30 μm were used for testing. 0.1% of carbon nanotubes was added to the cement slurry. Laboratory tests of cement slurries were carried out at Oil and Gas Institute – National Research Institute. The tests were carried out under conditions of increased pressure and temperature in the temperature range of 60–130°C and the pressure range of 25–80 MPa. CEM I 42.5R Portland cement and Class G drilling cement were used to make the slurries at temperature of 60oC. Cement slurries for temperatures from 80oC to 130oC were prepared on the basis of class G drilling cement. The recipes were developed on the basis of the requirements to be met by cement slurry for the cementing of casing under conditions of very high temperatures and reservoir pressures. The densities of tested slurries ranged from 1,840 kg/m3 (slurries at a temperature of 60°C) to 2.250 kg/m3 (slurries with the addition of hematite).Compressive strength tests and adhesion measurements were carried out after 2, 7, 14 and 28 days. Cement slurry recipes with very good technological parameters were developed, which after curing (after 28 days of hydration) showed very high values of compressive strength, reaching up to 44 MPa. Cements were characterized by high values of adhesion to pipes reaching up 8 MPa after 28 days and flexural strength of about 11 MPa. The test results show that the addition of carbon nanotubes has a positive effect on the mechanical strength of cement stones with their addition. The stones modified in this way are characterized by high compressive strength and high adhesion to steel pipes. Further research is needed to determine the influence of carbon nanotubes on the microstructure of hardened cement slurries. It is also necessary to conduct further research on the determination of the optimal amounts of these agents and the selection of the most compatible additives for cement slurries that work optimally in combination with nanoparticles.

Pengaruh Penambahan Fly Ash dan Serbuk Kaca Terhadap Sifat Fisik dan Mekanik Komposit Batako

Composite is a new material engineered by two or more materials where the properties of the materials differ from one another both in chemical and physical properties. Composites are obtained from a combination of metal with ceramics, metal with plastics, and others. The purpose of this study was to determine the effect of adding fly ash and glass powder on the physical and mechanical properties of brick-based composites. The drying process is carried out for 28 days. The compressive strength and water absorption tests were carried out after the drying process. The results showed the highest compressive strength value is on the B sample is 74.17 kg / cm2 and water uptake is lowest in the sample A, namely 10.53%. The highest compressive strength test results exist in the sample B is 74.17 kg / cm2 and the compressive strength is lowest in the sample A which is 66.67 kg / cm2. While the highest water absorption test results were in sample C, namely 15.05% and the lowest water absorption value was in sample A, namely 10.53%. Keywords: Brick-Based, fly ash, glass powder, compressive strength, water absorption.

Effects of natural zeolite addition on the properties of lime putty-based rendering mortars

The application of locally available component materials (lime putty and zeolitic rock as pozzolanic admixture) in two types of rendering mortars (designed for inner and outer render layer), was assessed through TG/DTA, XRD and MIP analysis and by testing the compressive strength, dynamic modulus of elasticity, water transport behavior and open porosity of mortars cured under two different regimes. Higher levels of lime replacement with fine natural zeolite (40% and 50% by mass), for both render layers, led to 1.5 to 2.5 times higher values of compressive strength when cured in humid conditions. The changes in zeolite content led to different pore size distributions of mortars and influenced their water transport behavior and open porosity. Overall, mortars with 40% and 20% of zeolite addition for the inner and outer layer (by mass), respectively, showed the best agreement of properties, when cured in humid conditions.

Characterization, hydration, durability of nano-Fe2O3-composite cements subjected to sulphates and chlorides media

The work aimed to study the impact of nano-Fe2O3 on the characteristics and durability resistance against SO42− or Cl− anions attack. Nano-Fe2O3 prepared from the heating of Fe(CH3COO)2OH at 300 °C (NFI) and 450 °C (NFII) at soaking time 2hrs. The prepared nano-Fe2O3 showed the accumulation of hematite and fine-ferrihydrite crystals having grain size of ≈10-20 nm. Physico-mechanical, chemical, microstructure, and durability were investigated. The compressive strength and chemically combined water contents increased upto 1.0 mass% nano-Fe2O3. The increase of nano-Fe2O3 upto 2%, the values of combined water contents decreased, however these values are larger than those of neat-OPC paste. The portlandite reduction of nano-Fe2O3-composite pastes prepared at 300 °C are higher than those of prepared at 450 °C. Mix having 1.0 mass% nano-Fe2O3 (NFI2) contributed the lower porosity values than specimens containing 1.5 and 2.0 mass% nano-Fe2O3 processed at 300 °C. Nano-Fe2O3 improves the durability of nano-Fe2O3-composite pastes towards SO42− or Cl− ions attack. Mixes containing 0.5–1.0% nano-Fe2O3 showed the lower values of total sulphate and total chloride contents, due to formation of a denser and finer-matrix with lower porosity, which blocked the empty pores for the diffusion of SO42− or Cl− ions, hence they showed the higher values of compressive strength and bulk density.

A regional supplementary cementitious material for the cement industry: Pistachio shell ash

The recycling of agricultural wastes in cementitious products has recently been a trendy approach for the sustainability goals of the world as it ensures economic and ecological advantages in addition to the safe disposal of these wastes. In this regard, the potentiality of a biomass ash obtained from the incineration of pistachio shell to serve as a supplementary cementitious material is documented in the present study. An increase of up to 30% in the amount of pistachio shell ash resulted in the proportional increase of both water requirement and setting time of the ordinary Portland cement by up to 54% and 300%, respectively. The incorporation of up to 20% pistachio shell ash into the cement yielded specimens of comparable or higher compressive strength values relatively varying between 98% and 117% at the 28 days and later curing ages. Beside the cementitious property, it was observed that a presence of graphitic structures in the pistachio shell ash remarkably improved the mechanical and the microstructural properties of cement mortars. In conclusion, at least 10% incorporation of this ash into the cement is highly recommended for the cement industry as it is beneficial in achieving the highest ultimate (400-day) compressive strength and promotes no loss on the early (2-day) compressive strength.

The Curing of Concrete Samples with Water - Experimental Verification of the Concrete Properties

The process of producing a monolithic concrete structure on site is constructed out under different climatic conditions, which can often be unsuitable for setting and hardening of concrete. The necessary conditions for setting and hardening of concrete are ensured by various ways of its curing. In practice, concrete curing is carried out in most cases by water spraying. It is used mostly in reinforced concrete ceiling slabs, which are further discussed in the work. A common procedure is to cure the upper surface of reinforced concrete ceiling slabs. This work therefore deals with the effect of curing of a reinforced concrete slab, on its strength properties. Long-term curing would yield higher values of compressive strength, but it is also necessary to consider how effective it is. As a pilot research in this work is investigating the properties of concrete cubes in various curing. It further develops theoretical possibilities for continuing research.

Investigation of the effects of different sulfate types found in seawater on concrete containing microfiber and silica fume

Sulfate salts which available in seawater with high concentrations cause the formation of ettringite in hydrated structures which formed as a result of the hydration of cement. On the other hand, ettringite causes excessive volume expansions and eventually leads to cracking of the concrete due to the internal stresses in concrete since it is a large volume mineral structure. In this study, ultrafine cement and silica fume as mineral additive were used together for binder design. Besides, microfiber has been added to the binder systems produced in different proportions. The produced specimens were kept separately in water, in solutions containing 2% Na2SO4 and 2% MgSO4 by weight for 90 days. The compressive strength test was performed at 28th and 90th days on cured specimens. In addition to the compressive strength test, the solution samples were taken from the curing solutions every 10 days and the change of sulfate concentrations was followed in the solutions. According to the results, in Na2SO4 solution higher compressive strength values were observed up to 66 MPa while strength loss was observed in the specimens cured in the MgSO4 solution. In parallel to this result, the remaining concentrations of SO42- ions in the MgSO4 solution were lower than those in the Na2SO4 solution. It was inferred that in Na2SO4 solution, the fibers could compensate for the internal stresses. This situation shows that especially the microfiber additive can compensate for the expansion that will occur as a result of ettringite formation, and thus it can help the mechanical stability of the concrete.

The Impact of Guinea Corn Husk Ash as an Admixture for Crack Control in Concrete

Guinea corn husk, a post-harvest agricultural waste common in Northern Nigeria is often heaped up constituting environmental nuisance. Guinea Corn Husk Ash (GCHA) is an incinerated by-product of it. In this experimental investigation, it was used to replace cement in concrete at levels of 0%, 5%, 10%, 20%, 30% and 40% by weight. The sample cubes were casted and cured for 3, 14, 28 and 56 days before crushing. Before then, the chemical constituents of the GCHA were determined from an X-Ray diffraction analyzer. The oxides found in the ash included SiO2 (85.4%), K2O (4.01%), Fe2O3 (0.64%), CaO (2.04%) and NaO2 (0.98%). SO3 and AI2O3 were not detected. The combined percent of SiO2, Al2O3 and Fe2O3 of 86.04% is above the 70% benchmark for a pozzolana material. Also, SO3 and NaO2 fell below the maximum allowable values of 4% and 1.5% respectively. The fresh concrete had slump values that ranged from 11mm for 0% cement replacement to 3.6mm for 40% replacement. The hard concrete had the highest compressive strength value of 23.67 N/mm2 for plain concrete and 49.3 N/mm2 at 5% GCHA replacement level. All were at 56 days of curing, satisfying quality for heavy load bearing. Beam samples cured for 3, 14, 28 and 56 days were subjected to flexural tests until they developed cracks. The cracks were measured for lengths (CRL) and width (CRW) for different replacement levels and curing days with a crack measuring microscope. The results show that, at 14days curing, there is a trend in the crack values’ reduction for the hardened GCHA concrete. This trend is also marginally seen for the 28 day cured samples, particularly at up to 20% replacement levels. The decrease in crack values were up to 17.2% and 2091% for CRL and CRW respectively. However, there were no significant crack controls with samples of higher replacement levels and those cured for 3 and 56 days. GCHA concrete can therefore be used to for heavy load bearing structures and for crack control at 5 – 20% replacement levels when cured for 14 days and 38 days.

The Impact of Guinea Corn Husk Ash as an Admixture for Crack Control in Concrete

Guinea corn husk, a post-harvest agricultural waste common in Northern Nigeria is often heaped up constituting environmental nuisance. Guinea Corn Husk Ash (GCHA) is an incinerated by-product of it. In this experimental investigation, it was used to replace cement in concrete at levels of 0%, 5%, 10%, 20%, 30% and 40% by weight. The sample cubes were casted and cured for 3, 14, 28 and 56 days before crushing. Before then, the chemical constituents of the GCHA were determined from an X-Ray diffraction analyzer. The oxides found in the ash included SiO2 (85.4%), K2O (4.01%), Fe2O3 (0.64%), CaO (2.04%) and NaO2 (0.98%). SO3 and AI2O3 were not detected. The combined percent of SiO2, Al2O3 and Fe2O3 of 86.04% is above the 70% benchmark for a pozzolana material. Also, SO3 and NaO2 fell below the maximum allowable values of 4% and 1.5% respectively. The fresh concrete had slump values that ranged from 11mm for 0% cement replacement to 3.6mm for 40% replacement. The hard concrete had the highest compressive strength value of 23.67 N/mm2 for plain concrete and 49.3 N/mm2 at 5% GCHA replacement level. All were at 56 days of curing, satisfying quality for heavy load bearing. Beam samples cured for 3, 14, 28 and 56 days were subjected to flexural tests until they developed cracks. The cracks were measured for lengths (CRL) and width (CRW) for different replacement levels and curing days with a crack measuring microscope. The results show that, at 14days curing, there is a trend in the crack values’ reduction for the hardened GCHA concrete. This trend is also marginally seen for the 28 day cured samples, particularly at up to 20% replacement levels. The decrease in crack values were up to 17.2% and 2091% for CRL and CRW respectively. However, there were no significant crack controls with samples of higher replacement levels and those cured for 3 and 56 days. GCHA concrete can therefore be used to for heavy load bearing structures and for crack control at 5 – 20% replacement levels when cured for 14 days and 38 days.

Mechanical behavior of in-situ alloyed Ti6Al4V(ELI)-3 at.% Cu lattice structures manufactured by laser powder bed fusion and designed for implant applications

In the present study, cellular lattice structures for implant applications are reported for the first-time incorporating copper directly by in-situ alloying in the laser powder bed fusion process. The aim to incorporate 3 at.% Cu into Ti6Al4V(ELI) is selected for improved antibacterial properties while maintaining appropriate mechanical properties. Previously, topologically optimized Ti6Al4V(ELI) lattice structures were successfully designed, manufactured and studied for implant applications. The development of a new alloy produced by in-situ alloying of elemental powder mixture of Ti6Al4V(ELI) and pure Cu powders was used here for the production of identical lattice structures with improved antibacterial properties. One of the same as-designed CAD models was used for the manufacturing of these lattices compared to previous work on pure Ti6Al4V(ELI) lattices, making direct comparison of mechanical properties possible. Similar manufacturability highlights the applicability of this alloying technique to other lattice designs. Microstructural characterization was performed by optical and electron microscopies, as well as microCT. Mechanical characterization was performed by means of compression tests and hardness measurements. Results showed that in-situ alloying with copper leads to the formation of localized Cu-rich regions, refinement of martensitic phase and the formation of CuTi2 intermetallic precipitates, which increased the hardness and strength of the material. Deviations in wall thickness between the as-designed and as-manufactured lattices led to anisotropy of the mechanical properties of the lattices. Higher compressive strength values were obtained when thicker walls were oriented along the loading direction. Nevertheless, alloying with Cu had a higher impact on the compressive strength of lattice structure than the wall thickness deviations. The direct in-situ alloying of copper in Ti6Al4V(ELI) is a promising route for direct manufacturing of antibacterial implants.

Effects of different kinds of carbon black nanoparticles on the piezoresistive and mechanical properties of cement-based composites

Carbon black nanoparticles (CBN) of different sizes, morphologies, microstructures and surface areas can be used to develop cement-based materials for strain monitoring and damage detection of concrete structures. There is a lack of systematic comparisons between mechanical and electrical properties of smart mortars fabricated with CBN of different characteristics. In this study, (4 × 4 x 7.5) cm prismatic composites containing CBN of distinct dibutyl phthalate (DBP) absorption number, conductivity and surface area were produced and subjected to direct current (DC), biphasic DC, piezoresistive and compression tests. Results show that CBN aggregates with the lowest structure (DBP of 125 cm³/100 g) and the highest resistivity provided high values of gauge factor, stress sensitivity and compressive strength, while CBN aggregates with very high structure (174 cm³/100 g) and low resistivity provided low internal capacitance and high electrical conductivity. The experimental data indicated that increases in structure and surface area improved the conductive network and reduced the internal capacitance, but decreased both compressive strength and piezoresistive response, due to reductions of variations of tunneling resistance between nanofillers.

Use of Recycled Aggregates Made from Construction and Demolition Waste in Sustainable Road Base Layers

Research has been carried out on recycled aggregates from the exclusive crushing of structural concrete waste (CDWRCon) and mixed ceramic materials (CDWRCer) in selective demolitions. This study analyses the use of these recycled aggregates as wet mix macadam (GARCon, GARCer) and in cement soil (CSRCon, CSRCer). The materials comply with the requirements of a road base; although, due to the low values of resistance to fragmentation, these materials are adequate for use in sensitive road systems and other places, such as urban roads and car parks, that have a low intensity of heavy traffic. As soluble salt contents were detected, additional waterproofing or drainage measures must be adopted to prevent water infiltration into the layers made up of CDWRCon or CDWRCer. Finally, the high initial values of unconfined compressive strength (UCS) allow the temporary passage of light vehicles over CSRCon or CSRCer after three days.

Manufacturing of silicon – Bioactive glass scaffolds by selective laser melting for bone tissue engineering

The irruption of additive manufacturing techniques opens the possibility to develop three-dimensional structures with complex geometries and high precision. In the current investigation a newly designed composite combining silicon (30, 40 and 50 wt%) with a bioactive glass and printed into scaffolds was obtained, using a direct selective laser melting (SLM) approach for the first time. Samples were computer-aided designed (CAD) to have cylindrical pores of 400 μm in diameter in order to be used as biomaterials for bone replacement. X – Ray diffraction was used to characterize the appearance of a new phase of pseudowollastonite precipitated by the partial devitrification of the glassy phase after the incidence of laser radiation. The mechanical behaviour of each composition was studied trough stress-strain curves, obtaining higher values of compressive strength as the silicon content increases. Scanning electron microscopy coupled to energy dispersive X – Ray spectroscopy (SEM-EDS) and Raman spectroscopy were used to study the bioactivity of each composite after soaking in the simulated body fluid (SBF) for 7 days, confirming this behaviour.

Properties of high-strength lightweight concrete using manufactured aggregate

The physical and mechanical properties of high-strength lightweight concrete were investigated considering various parameters including mixture design proportions, dosages and types of superplasticiser and silica fume and cement content aiming at a design strength of 45 MPa. The experimental results of density, tensile strength, modulus of elasticity and efficiency factor (ratio of compressive strength to density) were compared with empirical equations previously proposed in the literature. In earlier studies, using expanded clay coarse aggregate of maximum size 25 mm, the lightweight concrete presented a maximum strength of 30 MPa and an efficiency factor of 18·9 MPa.dm3/kg. By reducing the maximum size to 9·5 mm, a higher compressive strength of approximately 46·9 MPa and an efficiency factor of 28·3 MPa.dm3/kg were obtained. However, using expanded shale coarse aggregate yielded higher values of compressive strength and efficiency factor at 64·3 MPa and 36·3 MPa.dm3/kg, respectively. The replacement of coarse expanded clay aggregate with expanded shale resulted in a high-strength lightweight aggregate concrete with the best properties in this study: fc28 = 64·3 MPa, a density of 1·77 kg/dm3 and an efficiency factor of 36·3 MPa.dm3/kg.