Compressive Strength Of Samples Research Articles

ACTIVATION OF HARDENING PROCESSES OF FLUOROGYPSUM COMPOSITIONS BY CHEMICAL ADDITIVES OF SODIUM SALTS

The article is devoted to modifications of fluorogypsum compositions by chemical additives of sodium salts in the form of sulfate, sulfite and sodium sulfide, as well as their combined effect on the kinetics of structure formation processes. Technological, ecological and technical aspects of utilization of fluorogypsum compositions activated by additives were investigated. Experiments have shown that an up to 3% increase in the amount of sodium sulfite additive leads to an increase in the compressive strength of samples at early stages of hardening (up to 14 days), whereas utilization of sodium sulfate additive forms a crystallization structure at later stages. Therefore, it is rational to combine sulfate and sodium sulfite additives in an amount not exceeding 3% of the binder’s weight. The binder hardening structure formation with sodium sulfide addition at early stages results in production of additional structure-forming substances such as calcium sulfide. The mechanism of differentiated application of individual sulfate and sodium sulfite additives allowed to suggest that combined sulfate and sulfite additives utilization seems to be the most rational decision, due to the fact that it is not a mere individual additives’ combination, but a buffer mixture, which means that the mechanism of such mixtures influence will be subject to the buffer action. The system will maintain a strictly defined pH range constancy, which determines stability of new growths, forming the hardening structure. However, using sodium sulfide as an additive and studying its impact on fluoroanhydrate compositions structure formation in both individual and combined with sodium sulfite and sodium sulfate forms appears to be as much reasonable. The combined Na2SO3-Na2SO4 additive activates hardening processes both at early and late stages. At the same time, columnar structures growing from the center to the periphery are formed, as indicated by electron-microscopic studies. Their growth stems from concentration gradient of SO42-- and SO32-- ions, which is in complete agreement with the other research data and is typical for both metal melts and cement systems solidification process.

Chemical activation of binary slag cement with low carbon footprint

The primary object of this fundamental research will be to reveal the effect of various chemical activators (Na2SO4, Na2CO3, Na2SiO3 and NaOH) on the mechanical and hydration properties of binary slag cement (50% OPC and 50% BFS). Setting time, compressive strength, hydration heat, phase assemble, and pore size structure were systemically explored and compared to the control sample (without any chemical activator). The experiment results shown that the reaction kinetics of cement hydration was influenced differently by various chemical activators. The addition of Na2SO4 increased the cumulative hydration heat and the compressive strength of samples at all curing ages. Furthermore, more ettringite formed in the presence of Na2SO4. While other chemical activators decreased the compressive of samples with significantly enhanced porosity at the same time.

Early activation of high volume fly ash by ternary activator and its activation mechanism

To solve the problems of low early strength and severe plastic cracking caused by high volume fly ash used in cement-based materials. Triethanolamine (TEA), calcium hydroxide (Ca(OH)2), and sodium silicate (Na2SiO3) or sodium sulfate (Na2SO4) were selected to conduct a ternary doping test. The compressive strength of samples was measured to determine the best ratio, content, and time effect of the activator, and its action mechanism was studied by various micro test. The quantitative calculation model of main hydration products was established in the fly ash-cement system. Based on the simulation of molecular dynamics, the structure of NASH gel was studied under alkali activation. The results show that the optimal mixing mass ratio of TEA:Ca(OH)2:Na2SiO3 is 2:75:25 and the optimal dosage is 1.02% of the cementitious material. There are a large number of needle-like ettringite, petaloid hydrated calcium aluminate and clusters of hydrated calcium silicate gel in the system, whereas the amount of plate-like CH decreased significantly at hydration for 14 days. The Si/Al is three and aluminium coordination is predominantly tetrahedral, and the order of bonds stability and atoms mobility are Si–O > Al–O > Na–O and Na > O > Al> in the NASH gel, respectively. Under the Na+ and alkali environment, the Si(OH)4 and Al(OH)4- formed polycondensation reaction to reform polymers Si–O–Si and Al–O–Si, forming a large amount of NASH gel.

Transition coefficients between compressive strengths of samples with different shape and size in mass concrete and use of weight maturity method in dam construction

AbstractMass concrete (MC) is widely used in dam concretes due to their large aggregate grain diameters, low cement dosage, and low hydration temperatures. Monitoring of the hydration temperature and compressive strength is an important consideration during the casting of MC in the field. The purpose of this study is to determine the relationship between the compressive strengths of cylindrical specimens with different maximum aggregate grain diameters (Dmax) and different dimensions in MCs used in dam construction and to investigate the usability of the weighted maturity method in determining the compressive strength of dam MC. In this study, the compressive strength transition coefficient (fck ø15 × 30/fck ø25 × 50) of the cylindrical samples with different dimensions in MC was found to be 1.135. It was found that the weight maturity method can be used to estimate concrete strength in dam MC with low hydration temperature.

Enhanced mechanical and biocompatible properties of strontium ions doped mesoporous bioactive glass

Very low (≤0.2%) strontium (Sr) ion doped mesoporous (45S5) bioactive glasses (BG) were synthesized by sol-gel technique and calcination without using polymers (porogens), mould or other additives. The phases and their functional groups were confirmed by the X-ray diffraction (XRD) and Fourier transform infrared (FTIR) and FT-Raman spectroscopy respectively. Sodium calcium phosphate silicate [(Na0.11Ca0.89) (P0.11Si0.89O3)] which is essential for assisting the self-repair process of enamel was formed along with sodium calcium silicate (Na2Ca2Si3O9) phase. Doping of Sr ions (0.2 wt %) enhances the pore volume (96%) and surface area (108%) compared to pristine. Further, interconnected network structures are created exhibiting controlled and sustained drug release (58% in 720 h). The mechanical strength of the Sr doped BG samples increased significantly. The compressive strength of sample (Sr = 0.2 and 0.5 wt %) were 8.1 ± 0.5 and 11.2 ± 0.5 MPa with respective percentage increase of 440 and 647% compared to BG. The thermal stability and zeta potential of the Sr doped BG samples increase with considerable variation in the particle size when compared to the pristine. The cell viability and proliferation were also significantly enhanced by the doping of Sr ions which tailor the surface properties as well. The overall results robustly demonstrate for the first time that the very low doping of Sr ions (≤0.2%) in BG, play a major role in engineering the properties viz., mechanical, surface, drug release and cell proliferation making them suitable for multifunctional biomedical applications.

Experimental investigation of self-healing concrete after crack using nano-capsules including polymeric shell and nanoparticles core

In this paper, we focused on the self-healing concrete using new nano-capsules. Three types of nano-capsules with respect to availability, high strength and temperature tolerance are used; type 1 is URF and polyethylene (PE) as shell and nano titanium oxide (TiO2) as core, type 2 is URF and PE as shell and nano silica oxide (SiO2) as core, type 3 is PE as shell and nano silica oxide (SiO2) as core. The concrete samples mixed by nano-capsules with three percents of 0.5, 1 and 1.5. Based on experimental tests and the compressive strength of samples, the URF-PE-SiO2 is selected for additional tests of compressive strength before and after recovery, ultrasonic test, ion chlorine and water penetration depths. After careful investigation, it is concluded that the optimum value of URF-PE-SiO2 nano-capsules is 0.5% since leads to higher compressive strength, ultrasonic test, ion chlorine and water penetration depths.

Effect of the Curing Time and Combination of Corncob (Zea Mays L.) Ash With Swelling Clay on Mechanical Properties of Soil in Forest Road

ABSTRACT Swelling soil such as clay soil is known as unsuitable material for forest transportation due to the high volume change and mechanical defects. The aim of this study was to investigate the effects of corncob ash as a biologic additive on mechanical properties of clayey soil in forest roads of Bahramnia forestry plan in Golestan province. Different content of corncob ash and curing time were the treatments of study. Corn wastes were collected from farmlands and nodes of corncob with high silica content were used to produce ash. Soil samples were collected from the road construction area to conduct testing. First set of soil samples without additives and second set contained 5%, 10%, 15%, and 20% of corncob ash. Atterberg limits, standard proctor, and unconfined compressive strength were carried out on 7, 14, and 28 days curing times. Findings showed that the plastic index decreased by increasing corncob ash to 5%. Adding ash up to 5% can cause dramatic increase in plastic index. Addition of ash to the soil decreased dry bulk density and increased optimum moisture content. Maximum dry density (1.73 g cm−3) was recorded in optimum moisture of 28.5% and ash content of 5%. Unconfined compressive strength of samples increased until adding 5% of ash, and then the compressive strength decreased by increasing the ash content. There wasn’t significant difference between the curing times of 14 and 28 days in mechanical properties of soil samples. It was concluded that ash content of 5% and curing time of 14 days were the optimum values which maximum improvements in mechanical properties of swelling clay soil are occurred.

The relation between porosity, hydration degree and compressive strength of Portland cement pastes in the presence of aluminum chloride additive

In this work, the effect of aluminum chloride on the porosity, hydration and mechanical strength of Portland cement pastes was investigated. Four samples containing 0, 0.2, 0.4 and 0.8 wt% aluminum chloride were prepared. Different characterization techniques including X-ray diffraction, scanning electron microscopy and Fourier transform microscopy analyses were carried out on the samples in order to study crystallinity and phase formation, microstructure and morphology as well as functional groups and bond formations, respectively. The results obtained in this study showed promising effects of aluminum chloride on the hydration, microstructure and mechanical property of resultant Portland cement pastes. Also, it was found that an optimized amount of aluminum chloride is required to have optimized properties. Based on the results obtained, the addition of 0.4 wt% aluminum chloride led to 67% improvement in 28-day compressive strength. Also, there was a negative and a positive linear relationship between the compressive strength of the samples with their apparent porosity and hydration degree, respectively. A plane model with the R-squared of 0.9960 was presented which indicated the relationship between porosity, hydration degree and compressive strength of Portland cement samples.

Durability properties of concretes made with sand and cement size basalt

This study characterizes the durability and mechanical performance of the concrete produced with basalt in different sizes. The innovation of this research lies in the fact that cement is replaced by basalt powder. Different percentages of basalt in powder and sand form were added as a partial replacement of cement and fine aggregate, respectively. The replacement percentages range from 5% to 40% by mass of cement and sand. The influence of basalt replacement on the behavior of concrete was evaluated through strength and durability tests on samples at different ages. The experiments were carried out to determine the effect of the basalt replacement on the different age concrete samples' compressive strengths, abrasion resistances, water absorptions, and freezing-thawing strengths, as well as sulfate resistances. The study showed that partial replacement of different forms of basalt with cement and sand leads to a significant improvement in the concrete aspects mentioned above. The compressive strengths of samples at 28 and 60 days were found to be 15% higher, while the abrasion and the capillary water absorption rates at these ages were found to be 32% and 23% lower than those of the reference sample, respectively. In addition, the compressive strength after freeze-thaw and 180 days sulphate resistance values were found to be 45% and 47% higher than those of the reference sample, respectively.

Use of Mine Tailings as Precast Construction Materials through Alkali Activation

A study of the application of mine tailings as precast construction materials through alkali activation has been carried out, focusing on efficiently activating mine tailings, reducing alkali consumption, decreasing curing time and improving compressive strength. Firstly, the effect of temperature on the alkali activation of mine tailings was studied. Secondly, the impact of additives, i.e., calcium hydroxide and aluminum oxide, on the compressive strength of samples was investigated. Thirdly, the impact of forming pressure on sample strength was studied. Test results showed that unconfined compressive strength (UCS) of 40 MPa was achieved with the geopolymerization products through optimization. Finally, to elucidate the geopolymerization mechanism of mine tailings, microscopic and spectroscopic techniques including SEM/EDX, XRD, and FTIR spectroscopy were used to investigate the microstructure and the elemental and phase composition of the geopolymerization products. The findings of the present work provide a practical method for applying mine tailings as precast construction materials through alkali activation.

Methodological approaches to optimization of grain composition of heat-resistant concrete

Heat-resistant concrete of fine-grained structure attracts special attention of refractory applications manufacturers. The task of optimizing the grain size composition of heat-resistant concrete fillers on the basis of by-products and related products of silicon carbide (SiC) production and waste products of abrasive tools production on a ceramic bond of fine-grained structure is of research and practical interest. It is proposed to use grain size compositions of gapped grading for a fine-grained cement system of heat-resistant concrete. The analysis of methodological approaches in the calculation of the grain size composition of concrete fillers allowed us to determine the Fuller formula as an optimal one from a practical perspective. Due to the use of gapped grading of the grain component of the concrete composition, an optimal ratio between the size of the grains of quartz sand and the waste of abrasive production was achieved. Balanced distribution of the filler in concrete mix made it possible to obtain intimate contact between their grains, which resulted in dense, “well-packed” concrete structure, and will further enable 5-10% saving of the cement binder. The compressive strength of samples with gapped grading filler was 38.7 MPa, the thermal resistance (water, 800°C) amounted to 16 thermal cycles.

Investigation of the Effect of Larestan’s Pipeline Water on the Mechanical Properties of Concretes Containing Granite Aggregates

In this study, the compressive strength of the concretes made by the pipeline water of Larestan has been investigated. Although the used water for the concretes must be clean, standard, and generally drinkable water, in Larestan city, the pipeline water is nonpotable water; meanwhile, this type of water is still being used in the mixture of the concretes by companies and contractors. Since in the initial tests the compressive strength of the normal samples did not satisfy the standards, 50% of granite aggregate was replaced with the purpose of increasing strength of the samples. Then four types of samples were made, which are (1) normal concrete with pipeline water, (2) normal concrete with potable water, (3) granite concrete with pipeline water, and (4) granite concrete with potable water. The results showed that the compressive strength of normal samples is not standard in the case of using the pipeline water. This issue can be seen during the first four weeks of the samples, whereas these samples are placed in the standard zone by replacing 50% of granite aggregate instead of normal aggregates. This may be attributed to the compensating effect of granite aggregates in opposition to damaging effect of water. Also, by using the granite aggregates in the mixture, the compressive strengths of the samples were standard and almost identical in both cases of pipeline water and tap water. As a result, the concretes made in this city must include additives for increasing the strength, or the tap water should be used as a replacement for pipeline water.

Effects of Curing Temperature on Rheological Behaviour and Compressive Strength of Cement Containing GGBFS

The viscoplasticity and compressive strength of cement with high erosion performance were studied. The influences of curing temperature and content of ground granulated blast furnace slag (GGBFS) on these performances of the medium heat cement (including high iron and low calcium phase) were also investigated. The results indicate that the medium heat cement with high iron phase can maintain better fluidity and low temperature sensitivity than that of ordinary Portland cement at high temperature. GGBFS can play an important role in improving the fluidity and stability of the slurry, and avoid the cement setting and hardening prematurely at high temperatures. The microstructure analysis shows that a large amount of CH with layer shape appear in the slurry. The amount of this gel layer in the slurry increased as the curing temperature elevated. The layer can make the cement stone structure more denser, so that the compressive strength of samples are enhanced in the later stage. When the medium heat cement contains 40% GGBFS, the system has the best flow performance and stability under high temperature environment, and can be applied to mass concrete with excessive internal temperature.

Investigation of High Temperature Behaviors of Different Cure Applied Concretes

Concrete is produced cement-bonded system, which is a composite material formed by the combination of different components. The hydration process of the cement and the hydration products affect the mechanical and technological properties of the concrete. In this sense, the curing process is needed to achieve the targeted mechanical properties. In this study, concrete samples were produced by using additives with different origins called mineral additives. The samples were subjected to pressurized steam curing with the help of autoclave at different temperature and pressure values. After the curing process, the compressive strength of the test samples were investigated. In addition, the cured samples were kept in high temperature furnaces at 450 and 900 0C for 6 hours and the compressive strength of the samples were examined. As a result of the study, it was found that the autoclave cure caused an increase in the compressive strength of the concrete at 400 0C. The best high temperature resistance values were determined in the blast furnace slag addition series.

Application of sea sand for 3D concrete printing

The paper shows the promising use of sea sand for additive technologies in construction. The use of sea sand reduces the setting time of the concrete mix and increases the initial strength compared to conventional quarry construction sand. A comparative analysis of the characteristics of sea and quarry sands was performed. It has been experimentally proven that the use of sea sand instead of quarry sand in fine-grained concrete mix leads to a decrease in the setting time of the fresh mix and an increase in the strength of concrete samples. The flexural strength and compressive strength of samples containing sea sand at the age of 28 days increases by 35.7% and 16.7%, respectively, comparing to samples containing quarry sand.

Influence of barium and lithium compounds on silica autoclaved materials properties and on the microstructure

Abstract: The silicates materials are autoclaved material, which leads to its substantial fire resistance (class A). This kind of material sometimes is underestimated, despite their beneficial qualities (compressive strength 15–20 MPa, bulk density 1,73 kg/dm3, little water absorbability), have recently returned on the market with stronger position. The study focused on compressive strength, bulk density, impregnability and water absorbability and microstructural qualities of the modified silicates autoclaved materials. For the purposes of the experiments laboratory samples of traditional and modified products were prepared. Under laboratory conditions samples with dimensions of 40 × 40 × 160 mm were made. After the laboratory tests solid silicate bricks with dimensions 180 × 220 × 250 mm were prepared. The study aimed at determination of optimal ingredients of silicate mass with addition of barium aggregate graining 0–2 mm and liquid lithium silicate in form of solution. Physical and mechanical features of silicates were marked, using compressive strength of samples. To perform experiments, orthogonal compositional plan type 3k (with k = 2) was established, thus full experiment with two factors. For every correlation of factors, six parallel experiments were carried out. Analysis and tests of volumetric density were carried out in similar way. Modified silicate mass was precisely mixed, then pressed, and in the last stage placed in autoclaves. Inoculants were: barium aggregate with graining 0–2 mm in amount up to 20% (favorably 20%) and liquid lithium silicate in amount of up to 5% (favorably 4%). The article presents the effect of modification of autoclaved calcium-sand materials with barite aggregate (BaSO4) and lithium silicate on their application parameters. Production process of the modified silicate products has been left without change. Modification proves beneficial impact on silicate's porosity (limits its free space) and value of compressive strength, which was established on the level of 43,1 MPa with 5% of lithium silicate and 30% of barium aggregate in silicate mass (traditional samples have around 20 MPa). Favorably improved the phase microstructure of silicate products. In the microstructure of modified products, large clusters of xonotlite appeared with C–S–H phase and tobermorite.

Lightweight thermal insulation composites with redispersible polymer powder addition

Lightweight thermal insulation composites with different mass percentages of redispersible polymer powder (RPP) addition were prepared and the effects of RPP addition on mechanical properties, water resistance, thermal conductivity and interfacial bonding of lightweight thermal insulation composites were studied and analysed. The results showed that flexural and compressive strength of samples were improved by the addition of RPP due to improvement of pore structure and enhancement of interfacial bonding. Besides, RPP had a positive effect on thermal conductivity and interfacial bonding of lightweight thermal insulation composites.

Eco-cement production with alternative resources: recycling solution for shells ashes, organic husk ashes, organic waste ashes, and industrial sludge waste

This study aimed to determine the ratio of samples A, B, C, and D containing the combination from shells ashes, rice husk ashes, organic waste ashes, Lapindo mud, and industrial sludge waste as the chosen ecocement according to the closest value of compressive strength to SNI 15 2049 2004 on Portland Cement. Semen Gresik type OPC was used for blank sample. Data analysis was divided into two parts. Raw material analysis was done to determine CaO contained in shells ashes and SiO2 and Al2O3 contained in rice husk ashes, organic waste ashes, Lapindo mud, and industrial sludge waste using AAS. Product analysis was done to determine the powder density and compressive strength value in 3 days cubical mortar sample with the length of each side of 50 mm. The result of CaO contained in shell ashes was 81.57%. The highest, SiO2 and Al2O3, were 68.06% in rice husk ashes and 39.01% in industrial sludge waste. Sample A was chosen as ecocement according to the density and compressive strength values of 2.2 g/mL and 28.20 kg/cm2, respectively. Based on SNI 15 2049 2004 on Portland Cement, the compressive strength of Sample A complies with the compressive strength of Portland Cement type IV.

Pengaruh suhu penyimpanan terhadap kedalaman pengerasan dan kekuatan resin komposit

Introduction: Temperature plays a role in polymerization process of composite resin. Depth of cure is often used as a marker of polymerization adequacy in composite resins. Adequate polymerization will increase the mechanical properties of composite resin. The aim of this study was to evaluate the effect of storage temperature on depth of cure and compressive strength of composite resin. Method: Samples were made from nanofiller composite resin (Filtek Z350 XT,3M,ESPE,USA) after the materials were stored at 4°C and 24°C for two weeks. Twenty samples of nanofiller composite resins for each test group were prepared using metal mould with 6 mm in diameter and 4 mm thick. Samples were cured under visible blue light for 20 second. The polymerized composite resin was measured for determining the depth of cure. Compressive strength of samples was tested by using Universal Testing Machine. Result: The results showed that depth of cure value of 24°C (3.90 ± 0.07 mm) was higher than 4°C (3.83 ± 0.17 mm) and compressive strength of 24°C (35.20 ± 4.63 MPa) was higher than 4°C (26.47 ± 3.13 MPa). Statistical analysis showed that depth of cure were no siginificant differences (p > 0.05) but in compressive strength were significant differences between test groups (p < 0.05). Conclusion: Storage temperature can affect the depth of cure and compressive strength of composite resin, although no significant difference on the depth of cure.

Effects of EAF-Slag on alkali-activation of tungsten mining waste: mechanical properties

The mechanical properties of alkali-activated binders based on blends of tungsten mining waste mud (TMWM) and electric arc furnace slag (EAF-S) were investigated. The synthesis of alkali-activated binders was conducted at 60°C for 24 h with different TMWM/EAF-Slag ratios (90:10, 80:20, 70:30, 60:40, and 50:50 vt.%). Using sodium hydroxide (SH) and sodium silicate (SS) solutions as alkaline activators with ratio solid/liquid 4 by unit of volume, and the sodium silicate to NaOH (SS:SH) ratio of 2:1. The X-ray Diffraction (XRD), mercury intrusion porosimetry (MIP) were determined. The different percentages of the precursors and the alkaline activators were optimised to produce paste samples. The compressive strength of samples with 10 vt.% EAF-Slag was close to 20.7 MPa after 90 curing days. The mechanical properties were further increased up to 30 MPa by increasing the percentage of EAF-Slag to 50 vt.%. This demonstrates a new potential for re-using waste material for various constructional applications.