Compressive Strength Of Samples Research Articles

Effects of refined grains and doped nanoparticles on fabricating Al2O3 ceramics using binder jetting

Adding sintering additives to fabricate alumina ceramics via the binder jetting (BJ) technique effectively enhances material properties. However, it is still limited by the disadvantages of low relative density and poor mechanical properties. This study proposed reducing matrix particle size and adding nanoscale particles using binder jetting to address the poor densification and strength of printed alumina (Al2O3) samples. Additionally, their effects on the mechanical properties and manufacturability of the material were explored. Numerical simulations were carried out before the experiments to predict the impact of particle stacking on the powder bed using the discrete element method (DEM). Then, filler particles with an average 40 μm size replaced the original 106 μm-sized Al2O3 particles. Subsequently, Al2O3 nanoparticle content in the samples was gradually increased, and the relevant properties of the sintered samples with different compositions were tested. Consequently, the size of the Al2O3 particles and the addition of Al2O3 nanoparticles significantly affects the physical and mechanical properties of the samples. The sample with 106 μm-sized particles has a compressive strength of 58 MPa, while reducing the particle size to 40 μm increases its compressive strength by 26 %. Moreover, the sample's compressive strength could reach up to 330 MPa, an increase of 513 %, and the hardness reaches 1215 HV (11.91 GPa) by expanding the Al2O3 nanoparticles content to 30 %. Additionally, using Al2O3 nanoparticles further reduces the sintering temperature, significantly improving the practicality of Al2O3 printing using binder jetting.

Mechanical investigations of the durability performance of sustainable self-compacting and anti-spalling composite mortars

The durability of the mortar has recently been a critical concern, as it inherently contributes to the overall sustainability and resilience of the structure. This paper aims to address the growing demand for sustainable and durable infrastructure by investigating the effect of incorporating polypropylene, nylon, and jute fibers into self-compacting mortars. The performance of the mortar was tested under high temperatures, chemical attacks (Acid and sulfate attack), and freeze-thaw cycles. The mechanical properties were also examined through strength tests including compressive and flexural strength. Transport properties of mortars were investigated by water absorption, porosity, and sorptivity tests. Seven test mortar mixes were prepared, one of which was a control sample and six had polypropylene, nylon, jute fibers, and an entraining agent. Three of the six mortar mixes had 0.5 % polypropylene, nylon, and jute fibers while the other three had 1 % of these fibers. The effect of acid and sulfate was investigated by parameters of weight losses and reductions in compressive strength of mortar samples while the effect of freeze and thaw was investigated by comparing the drop in compressive strength of mortar specimens with and without fibers. The results revealed a drop in water absorption and porosity of mortar samples containing 0.5 % test fibers as than the control sample, while a slight increase was observed in water absorption and porosity for mortar samples incorporating 1 % of these fibers. The sorptivity of test samples was less than that of the control sample. The compressive strength of mortar samples having 0.5 % fibers was found to have increased, however, a slight reduction was observed in the compressive strength for samples having 1 % of these fibers. The addition of Polypropylene, Nylon, and Jute fibers significantly increased the flexural strength of mortar samples. There were lesser weight losses and compressive strength losses for mortar samples containing Polypropylene, Jute, and Nylon fibers as compared to the control mortar sample when subjected to 5 % HCL, 5 % sodium sulfate, and 28 freeze-thaw cycles. The addition of Polypropylene, Jute, and Nylon fibers has improved the durability performance of self-compacting concrete against different deteriorating phenomena, which eventually can result in durable and sustainable infrastructure.

Study on mechanical properties and microstructure of green ultra-high performance concrete prepared by recycling waste glass powder

Ultra-high performance concrete (UHPC) encounters hindrance in pursing carbon neutrality and extended applications due to the dosage of cementitious materials and high energy consumption. To address this problem, this study utilized WGP to replace placement in the production of UHPC-WGP and invested its impact on workability, mechanical properties, and microstructure. The research results showed that incorporating WGP improved the flowability of UHPC and reduced its early-age mechanical properties but significantly enhanced the later-age mechanical properties. When the WGP content is 20 %, the sample's compressive strength after 28 days increases by 8.6 %. The specimens with 28 days exhibited the highest flexural strength and ultimate deflection, reaching 24.8 MPa and 0.809 mm, respectively, and the UHPC specimens (90 d) demonstrated the lowest total porosity, reduced by 14.6 % compared to the reference group. Furthermore, scanning electron microscopy (SEM) observations revealed that WGP had a good micro-aggregate filling effect and pozzolanic effect improved the microstructure. Finally, low cost and energy consumption characteristics further promote the sustainable application of WGP-based UHPC.

Prediction of the compressive strength of lightweight concrete containing industrial and waste steel fibers using a multilayer synthetic neural network

The use of waste and industrial steel fibers as part of the materials used in concrete can increase resistance and reduce cost and air pollution. It also saves energy. One of the important measures for technical inspections and assessment of the existing condition of structures, especially bridges, which is the most important communication factor, is to check the compressive strength. Considering that the calculation of compressive strength in the laboratory is done with the intervention of human power and is undoubtedly affected by human error, we decided to use it through.Predicting the mechanical properties of concrete reinforced with steel fibers based on artificial neural network models without the need to conduct any laboratory studies will save money in construction projects. Unlike classical methods in statistical theories, neural networks do not require any specific model or function along with limiting assumptions to linearize problems.For this purpose, this research was done with the aim of compensating this problem and with the aim of building a neural network with high accuracy that can make the desired predictions with the least error. In this research, this modeling was done using artificial neural networks (ANN) and Levenberg algorithm. The data used to train the neural network was collected from 45 different mixing schemes. Then the compressive strength of the sample is determined experimentally. The parameters considered for the ANN inputs are the values of steel fiber, water, water-cement ratio, cement and superlubricant. The objective data of this study included the compressive strength of each of these mixing designs at the ages of 7, 28 and 60 days. Then, to design the neural network, 75% of the data were considered as training data, 15% as target data and 15% as validation data. The compressive strength of concrete samples made from waste steel fibers increases. One of the reasons for this result is the placement and uniform distribution of fibers in the cement matrix, or in other words, the optimal amount of desired fibers in concrete. For experimental information and data, results can be seen with the help of neural network in data analysis. It was observed that the validation is correlated with a correlation coefficient above 99% and the constructed neural network has sufficient accuracy and validity.

Investigation of effective replacement of sand by waste perlite in AAC production

AbstractAerated concrete is a lightweight building material with excellent thermal and technical properties, relative to strength, excellent workability, and is economically advantageous. The basic composition of raw materials includes lime, cement, silica sand, and aluminum powder. Currently, the usability of secondary raw materials is being investigated in many construction sectors. The usability of secondary raw materials becomes a necessity from an ecological and economic point of view. The elimination of CO2 emissions is currently a major global issue. Secondary raw materials used in the construction industry are most often waste materials produced during the combustion of solid substances. These substances are often accumulated in landfills, which have a negative impact on the surrounding environment. It is necessary to constantly look for new ways of using these waste materials not only in the construction industry. The use of these raw materials reduces the price of the final product. It is advantageous if it also brings about a positive change in the properties of aerated concrete. The article deals with the possibility of replacing part or all of the sand content in the recipe of autoclaved aerated concrete with waste perlite. As part of the experimental verification, the influence of waste perlite filler on physical‐mechanical properties (e.g., bulk density, strength) and changes in microstructure is investigated. Primary sand is replaced by perlite in the amount of 10%, 30%, 50%, and 100% by volume in the experiments. The formation of porous structure, its characteristics, and mineralogical composition, in particular the formation of tobermorite, is also evaluated. The study has brought an interesting finding. The results show that the maximum beneficial amount of waste perlite is 30%. Up to this limit, waste perlite has a positive effect on the even distribution of pores in the matrix, with a zero‐phase content of more than 65%. The compressive strength of the samples with waste perlite increases by up to 22% of the values of the compressive strength of the reference sample.

Characterisation and Performance of Nigerian Kaolin and Metakaolin in Geopolymer Synthesis

This study is aimed at characterising and understanding the mechanical and microstructural behaviour of natural and calcined kaolin clay for geopolymer applications. The clay samples obtained from Kaduna State, Northern area of Nigeria, were calcined within the temperature range of 700 and 900oC and are represented by MK7, MK8 and MK9. The raw kaolin and metakaolin were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) and scanning electron microscopy (SEM). To produce geopolymer binders, the precursors were reacted with a 1:1 combination of sodium hydroxide and sodium silicate solution and a precursor to activator ratio of 1.2 was suitable for preparation. The compressive strength of the samples was determined at three testing age of 7, 14 and 28 days. From the results obtained, the kaolin-based geopolymer generally had a long setting time and testing was impossible at the 7-day testing age. The compressive strength of other samples however, increased with increase in the calcination temperature. The values obtained at the maximum testing age of 28 days for all samples fall between 5.1 -14.9 MPa. The scanning electron microscope morphology of the produced binder, show the presence of air trapped in the paste which may have reduced the strength value. Vibrating samples before setting can improve the performance of the geopolymer binders by removing most of the trapped air. Geopolymers produced from this study based on strength obtained, can be used in less critical areas of the construction industry.

Tensile properties of slag-based engineered cementitious composites with ground granulated blast-furnace slag

During the last decade, concrete technology has been undergoing rapid development, resulting in a new concept of engineered cementitious composite (ECC) to overcome the brittle behaviour of cement-based materials. ECC is one movement to fully incorporate waste material as an innovation in green material due to excellent toughness and energy absorption capacity, self-healing ability, fire performance, and remain durable under erosion environment. ECC exhibits a strain-hardening behaviour through the formation of micro cracking. This study is focusing on the tensile behaviour of the slag-based ECC. A total of five ECC mixes were designed with different cement to ground granulated blast-furnace slag (GGBS) ratio. Five samples of dog bone and three cylindrical for each mixture were prepared for direct tensile and compression tests. Compared to control samples, there are increments in compressive strength for samples contained 50-60% of GGBS and reductions in compressive strength for samples contained 70-80% of GGBS. The tensile strengths of ECC increase in the rate proportionally to the content of GGBS in ECC mixtures. The failure modes of the ECC cylinder samples including crushing under compressive load and few micro cracks are observed in ECC dog bones.

Sulfuric acid resistance of concrete containing coal waste as a partial substitute for fine and coarse aggregates

The vulnerability of concrete to sulfuric acid attack requires much attention in both design and maintenance. Taking the waste management approach into account, this study utilized coal waste (CW) as a partial replacement for fine and coarse aggregates. The use of CW as aggregate replacement materials in concrete is a novel topic. Regarding the literature, concrete mixtures with CW aggregates showed relatively similar strength properties to conventional concrete. However, the effects of aggressive environments on the concrete containing CW aggregate have not been addressed. Here, the effects of sulfuric acid attack on the key properties, such as split tensile strength (STS), compressive strength (CS), weight loss, and ultrasonic wave velocity (UWV), were thoroughly assessed. Moreover, scanning electron microscope (SEM) images have been captured to discern the morphology changes. Various CW dosages (0%, 5%, 10%, 15%, and 20% by weight of dry aggregates) were used. The results revealed that higher CW contents led to more water absorption and stiffer mixtures with lower workability. The weight loss of the samples showed an increasing trend with increasing CW contents. The split tensile strength and compressive strength of samples without sulfuric acid attack were enhanced by using 5% and 10% CW. After exposure to the sulfuric acid solution, the strength of CW-concrete samples was continuously decreased by increasing CW contents. The UWV values were decreased by increasing CW contents, which induce more porosity and lower integrity in concrete elements. SEM images show that the use of CW led to the formation of Ca (OH)2 crystals that were not wet, needles of ettringite, and gypsum, which severely hurt the properties of permeability, durability, and strength.

Enhancement in compressive strength of carbide slag activated ground granulated blast furnace slag by introducing CaCl2 and NaCl

Alkali-activated materials was the green and low carbon cementitious materials. In this study, the calcium chloride (CC) and sodium chloride (SC) were used as accelerator to promote the compressive strength of carbide slag (CS) activated ground granulated blast-furnace slag (GGBFS). The compressive strength of samples was investigated and the related mechanism was comprehensively characterized with hydration heat, XRD, TG-DTG, SEM, 29Si NMR and MIP in details. These results showed that 5% SC and CC significantly improved early strength with an increase of 58.8% and 127.1% at 3 days, respectively. Interestingly, the presence of CC also increased the 28-day and 90-day strength from 16.6 MPa and 30.4 MPa to 50.2 MPa and 70.5 MPa, respectively. These results citified that the addition of CC and SC accelerated the consumption of CS at early age. At late age, the enhancing effect of SC was lower than CC, reflecting the Ca2+ made a greater contribution to strength development than Na+. The addition of CC still accelerated the rapidly precipitation of aluminium phase in the form of hydrocalumite, which could improve further dissolution and hydration of GGBFS at late age. Therefore, the addition of CC produced more hydration products that would refine microstructure and enhance strength at late age. These findings suggested a novel way to improve the mechanical properties of alkali-activated GGBFS.

Drava river sediment in clay brick production: Characterization, properties, and environmental performance

The ever-growing worldwide demand for fired clay brick has resulted in the shortage of clay in many parts of the world. Therefore, there is a need to look for more sustainable alternative materials for the brick manufacturing. This study has investigated the potential use of the untreated Drava River sediment as a substitute material for clay in the production of fired bricks, with the research being conducted at both laboratory and industrial level. At the laboratory level, brick specimens were prepared by mixing clay with different river sediment proportions (ranging from 10 to 50 wt%) and were fired at 950 °C, with microstructural and various physical–mechanical properties being analyzed. Elevated carbonate content in Drava river sediment results in higher weight loss during firing at temperatures up to 950 °C, comparing to firing pure brick-making clay. Consequently, the addition of sediment increases porosity of fired bricks, which results in lowering of their mechanical properties. Results reveal that the compressive strength of the pure clay sample was 79.5 MPa, while the compressive strength of the sample with the addition of river sediment from 10 wt% to 50 wt% decreased from 73.9 MPa to 26.2 MPa, respectively. Despite the lower compressive strength, the 26.2 MPa is still above the limit value of 10 MPa specified in the standard EN 772–1 [1]. At the industrial level, hollow clay bricks were prepared with 20 wt% of the river sediment and fired in a tunnel kiln. Inclusion of the river sediment also decreased compressive strength from 38 MPa for pure mixture to 26 MPa for 20 wt% of the sediment addition, confirming usability of Drava sediment in brick production. In addition, LCA study has been conducted to evaluate the environmental impacts associated with the industrial production of classic bricks and bricks with the addition of the river sediment. The obtained results have shown that the bricks made with the addition of the Drava River sediment are sustainable and environmentally friendly and meet all the requirements specified in the relevant regulatory standard.

An experimental study on the mechanical properties of underground mining backfill materials obtained from recycling of construction and demolition waste

Environmental and safety factors have caused the mining industry to consider backfilling underground openings to prevent mine collapse in deeper and further extraction operations. This paper discusses the possibility of utilizing the construction and demolition waste (CDW) as cemented recycled aggregate backfill (CRAB) materials in the underground mining industry. In this regard, several samples were prepared by mixing the recycled aggregates of CDW components and Portland cement and various tests were performed to consider their physical and mechanical properties. Results indicate that by adding 8% cement content to the mixture, the uniaxial compressive strength (UCS), the most important property of backfill materials, reaches 4.95 MPa. Based on common compressive strength criteria of backfill materials, the obtained value of UCS satisfies the prerequisite for most underground mining applications. There are situations, such as the ground support, where higher UCS quantities are required for backfill materials. By removing the plaster and soil components of CDW from the mixtures, the compressive strength of samples has increased by 55.4% and 7.1% respectively. Therefore, by removing the plaster from the mixture, the prepared samples meet the requirements of ground support applications. Moreover, with the increase in cement dosage, the effects of cement content on the properties of the CRAB samples were investigated.

Micro-structural and mechanical properties of PVA fiber reinforced engineered cementitious composite incorporating natural and artificial pozzolanic materials under different temperatures

• The pozzolans' contents significantly affect the tensile strain capacity of the ECC. • Using fly ash, GGBS and zeolite can improve tensile behavior of the ECC. • The GGBS based ECC has better tensile stress–strain behavior. • At the temperatures above 50 °C, the mechanical properties of the ECC decrease. • ANN and MLR can predict the mechanical properties of the ECC with high accuracy. Engineered cementitious composites (ECC), which have high toughness and tensile ductility, as well as multiple fine cracking, satisfy the high safety and durability criteria in the development of sustainable infrastructures. The effect of different temperatures on the mechanical characteristics of polyvinyl alcohol (PVA) reinforced ECC (PVA-ECC) was examined in this work. A study was conducted to compare the modulus of elasticity, tensile strength, and compressive strength of samples containing various dosages of three available pozzolans: zeolites (ZE), fly ash (FA), and ground granulated blast furnace slag (GGBS), as well as silica fume (SF). Scanning electron microscopy was used to examine the microstructure of PVA-ECC samples subjected to various high temperatures (SEM). For 1 h, all specimens were exposed to temperatures of 150, 100, 50, and 20 °C. The experimental findings revealed that when the temperature rises to 50°, all three mechanical parameters, modulus of elasticity, tensile strength, and compressive strength, increase, then drop. The study of the microstructure of PVA-ECC reveals a basic explanation for the loss of macro mechanical characteristics. Finally, using ANOVA analysis, the relationship between independent parameters such as the age of the sample (AS), temperature (T), and water to pozzolan materials (W/P), and dependent parameters (i.e., compressive strength, tensile strength, and modulus of elasticity) was evaluated, and the multivariate linear regression (MLR) and the artificial neural network (ANN) were shown to be useful for modeling.

The effect of dosage nanosilica and the particle size of porcelanite aggregate concrete on mechanical and microstructure properties

Abstract Several research studies have been conducted on the usage of nanoscale silica particles in concrete, based on the success of employing silica fume as an active pozzolan in concrete. The impact of several doses of nanosilicas (NpSs) in powder having a certain surface area of 160 m2/g and two particle sizes of porcelanite rock on the mechanical characteristics of lightweight porcelanite aggregate concrete was investigated. The addition of NpS particles significantly improved the workability of mixes, according to the results. The compressive strength of samples was influenced by NpS, with higher doses of NpS resulting in greater improvement. Porcelanite aggregate concrete’s compressive strength was unaffected by a modest percentage of different NpSs. NpS had an effect on the samples. Flexural strength also improved at all NpS dosages. The flexural strength of porcelanite aggregate concrete increased by a low percentage of various NpS.

Properties of poly(lactic acid)/walnut shell/hydroxyapatite composites prepared with fused deposition modeling

In this work, fused deposition modeling (FDM) technology was used to prepare poly(lactic acid)/walnut shell/hydroxyapatite (PLA/WS/HA) composite filaments. HA was treated with silane and characterized by Fourier transform infrared spectroscopy (FTIR). The composites were investigated by using simultaneous thermal analyzer, scanning electron microscopy (SEM) and a universal mechanical testing machine. The results showed that incorporating either HA or WS improved the thermal stability and water absorption of PLA, but lowered the tensile and compression strength. Fillers toughened the PLA matrix, resulting in higher tensile elongation and compressive strain. The tensile and compressive strengths of samples significantly dropped after water-immersion for 6 weeks. Finally, scaffolds were manufactured by using FDM. The compression modulus and structural feature of scaffolds indicated that the PLA/WS/HA composites have the potential to be applied in structural parts, such as bone implants.

EFFECTS OF WOOD ASH ON GEOTECHNICAL PROPERTIES OF LATERITIC SOILS

Biochar can be derived from pyrolysis of agricultural waste, wood waste (saw dust), logging residues and other biological waste. Biochar can be use to improve the quality of construction and engineering materials. The study deals with the effect of biochar (wood ash) on geotechnical properties of lateritic soils, and it is to investigate the effect of wood ash on the geotechnical properties of lateritic soils. For these purpose, soil samples that were gotten from borrow pit were made use of and blended with available biochar which is used as a stabilizing agent. This was done at different percentages which include (0%, 3%,5%, 10%,15% and 20%,). The biochar was sieved with 125 micrometer sieve and were after blended with the soil samples. The compaction test, consistency limit test, the unconfined compressive strength test were carried out on the samples. It was discovered that the OMC of the blended samples increases as the percentages of the biochar that was used to blend the samples increases, also the MDD on the contrary decreases. The unconfined compressive strength test were conducted on all the samples (0%,3%,5%,10%,15% and 20%). It was also discovered that the compressive strength of soil samples increases with increase in the addition of biochar of the samples having its peak at 10%. Then reduction in compressive strength was experienced in between 11% to 20% addition of biochar to the soil sample. Conclusively, the results show that biochar can be use as stabilizing material when added to lateritic soil samples. But more addition of it at a particular stage may lead to the reduction in the compressive strength of the sample in which the sample may be weak and brittle. The size of the biochar if not properly crushed and sieved may not yield a desired result.

Effects of sodium chloride on the mechanical strength of alkali activated volcanic ash and slag pastes under room and elevated temperatures

This study investigated effects of the sodium chloride on the microstructural and mechanical properties of alkali activated volcanic ash (VA) and ground granulated blast furnace slag as well as Portland cement pastes. To this end, unconfined compressive strength (UCS), scanning electron microscopy (SEM)-EDS-Mapping, FTIR, and XRD tests were conducted. Furthermore, effects of curing temperature on the binding capacity of chloride in alkali activated cements were examined in both elevated (HT) and room (RT) temperature conditions. The VA was replaced by slag at 0, 50, and 100 wt%. Based on the results, samples containing 100 wt% slag showed the highest mechanical strength in both curing conditions. Besides, addition of sodium chloride from 0 to 10 wt% did not significantly affect the strength of samples containing 100 wt% volcanic ash in both curing conditions. On the other hand, in HT condition, mechanical strength of samples containing 50 and 100 wt% slag, as well as Portland cement pastes increased with increasing sodium chloride from 0 to 2.5 wt%, and further addition of sodium chloride by up to 10 wt% led to a reduction in their strength. However, compressive strength of samples containing 50 and 100 wt% slag, as well as Portland cement samples, decreased with the addition of sodium chloride from 0 to 10 wt% in RT condition. Microstructural investigations were conducted, aiming to find the mechanism controlling the reactions. It was found that (N,C)-A-S-H and C-S-H gels were the dominant factor in the solidification and encapsulation of chloride ions in slag-based samples.

Upcycling of air pollution control residue waste into cementitious product through geopolymerization technology

This study explores the possibility of using geopolymerization technology (GT) to immobilize the potentially toxic elements (PTEs, e.g., Zn, Cu, Cr, As) in the APCr and convert it into useful cementitious product. To maximize its recycling, the amount of APCr in the designed product was increased gradually from 20% to 80% by the total solid mass. Leaching test showed that GT can effectively immobilize the PTEs in the APCr solidified samples without any health and environmental concerns. The compressive strength of samples can exceed 18 MPa at 28 days at a highest amount of 80% APCr through GT. Thermogravimetric analysis (TGA) results showed that solidified samples underwent mass loss due to evaporation of free and physically bound water at low temperatures (<200°C) and melting and evaporation of soluble salts in APCr at high temperatures (>800°C). Characterization of solidified samples conducted through the X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Scanning electron microscopy-Energy dispersive analysis (SEM) revealed the formation of C-A-S-H and N-A-S-H gels in solidified bodies and verified that APCr was successfully solidified and embedded into the geopolymer network structure

Development of peat-containing mixtures for thermal insulation of steel castings tops using glyceroborates

To insulate the castings tops, heat-insulating shells are made from peat-containing mixtures, which are characterized as inexpensive, non-scarce and environmentally friendly substances. However, due to their low strength characteristics and a high degree of fire hazard, their widespread use in foundry is limited. The article presents the results of research on the development of effective mixtures for insulating the steel castings tops using peat and borate compounds. The development of an effective heat-insulating mixture for heat insulation of castings on the basis of peat mass using glyceroborate of the general formula (СН2О)3ВОН, glyceroborate of oleic acid of the general formula С17Н33СООСН(СН2О)2ВОН and glyceroborate of stearic acid of the general formula С17Н35СООСН(СН2О)2ВОН. To achieve this goal, the following tasks were solved: determination of the tripoli content in the peat mass, at which the value of the thermal conductivity coefficient is 0.42 W/(m ∙ K) and the indicator of the mixture crumbling at this value; study of the influence of glyceroborates on binding properties of technical lignosulfonates; creation of a heat-insulating mixture from peat, tripoli, lignosulfonate and glyceroborates; study of crumbling, formability, ultimate compressive strength in a wet state and ultimate tensile strength in a dry state of an insulating mixture in dependence on the content of glyceroborates. Studies of the influence of glyceroborates on the binding properties of technical lignosulfonate have established an increase in its binding properties in relation to fillers by 35&ndash;39 %, which helps to reduce crumbling, improve formability and increase the strength properties of heatinsulating mixtures. Tests of mixtures consisting of peat, tripoli, lignosulfonate and glyceroborates for crumbling, formability, compressive strength of samples in a wet state and tensile strength of dry mixtures under tension showed that the addition of glyceroborate compounds improves the technological performance of the mixture. An effective heat-insulating mixture has been developed for the steel castings tops of the following composition, wt.%: peat mass &mdash; 60; tripoli &mdash; 20; technical lignosulfonate &mdash; 10&ndash;12; glyceroborate (oleic acid glyceroborate, stearic acid glyceroborate) &mdash; 8&ndash;10.

Procedure of determination of the cold compressive strength of samples of refractory inserts for composite plates of shuttles

The slide gate is the most advanced type of casting device. The design of this gate is based on the action of two refractory plates, which are in close contact with each other, one of which slides on the other, fixed motionlessly. Sliding gates can be of two types: with a lower movable plate, which carries out a back-and-forth movement in the horizontal direction using a hydraulic cylinder, and with a lower movable plate, which rotates around an axis. The shutter of first type is called a slide gate; the second is a rotary shutter.&#x0D; Monitoring of properties in particular strength of refractory inserts facilitates increase in operation reliability of constituent plates of sliding shutters in steel casting ladles. However, it is not possible to apply the existing standards for the compressive strength determination of these refractory products, because these standards do not provide for test samples with dimensions less than 20 mm. That's why the procedure MB 322-39-2021 was developed and implemented by JSC “URIR named after A. S. Berezhnoy” with the purpose of monitoring of cold compressive strength of refractory inserts for constituent plates of sliding shutters. According to this procedure, a method for measuring the compressive strength is used: the cross-sectional area of the test sample is determined, the maximum compressive load that leads to the test sample failure is measured, and the compressive strength is calculated.

Effect of Curing Temperature on the Mechanical Strength of Alkali Activated Laterite Geopolymeric Samples

A huge amount of carbon dioxide is released in the Portland cement production process. A large quantity of greenhouse gases is produced because of the significant amount of energy consumption via making bricks through firing. Using the pozzolanic sources containing the aluminosilicate and alkaline reagents, a new type of green materials called geopolymeric materials are produced with quite lower environmental hazards. The use of laterite as an iron-rich aluminosilicate material has a high potential for building materials. In this study, the effect of the curing temperature and characteristics of the alkaline reagent including the concentration of sodium hydroxide solution and the water-glass to sodium hydroxide mass mixing ratio on the mechanical strength of the laterite-based, oven-cured geopolymer samples was investigated. The results showed that the curing temperature had a significant effect on the compressive strength of the laterite-based geopolymer samples so that with a 15°C change at the curing temperature, the compressive strength of the samples could be multiplied and a sharp increase in the mechanical strength could occur. Also, according to the results of this study, the 6 M sodium hydroxide is recommended for the construction of the laterite-based geopolymer materials with low cost and relatively high strength, and for the construction of higher-strength building materials, the 14 M sodium hydroxide is recommended.