Compressive Strength Of Samples Research Articles

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.

Influence of calcium sulfoaluminate cement on early-age properties and microstructure of Portland cement with hydroxypropyl methyl cellulose and superplasticizer

In order to improve the construction efficiency of thin layer masonry mortar (TLMM) even to realize mechanized construction, it is necessary to maintain suitable workability and at the same time get early-strength. To improve the workability of TLMM cellulose ether and superplasticizer were usually used. Calcium sulfoaluminate cement (CSA) was used as mineral accelerator in the paper to make the mortar get early-strength. Therefore, the effect of CSA on the early-age properties and microstructure of Portland cement (PC) with hydroxypropyl methyl cellulose (HPMC) and polycarboxylic acid superplasticizer (PA) was investigated. The X-ray diffraction (XRD), thermogravimetry (TG), isothermal calorimetry, mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) were used to clarify the impacts. Results showed that the setting time of the PC with HPMC-PA was accelerated with the increase of CSA replacement rate (CRR). CRR also had a significant impact on the development of compressive strength, especially when CRR was over 5.0% by weight, the compressive strength of samples were obtained after curing for 6 h. Moreover, the microstructure of the sample changed with CRR. With the increase of CRR, the content of ettringite (AFt) was increased and its morphology became shorter and thicker, the hydration of aluminate (C3A) and tricalcium silicate (C3S) in PC was delayed and the amount of portlandite was decreased, and the pores with diameter over 20 nm were increased. In addition, a new discovery was that C3A in PC and ye'elimite (C4A3S‾) in CSA were competitive with each other in reaction with gypsum to form AFt, and C4A3S‾ preferentially reacted.

Experimental investigation on mechanical strength and microstructure of cement paste by electric curing with different voltage and frequency

To understand the effects of direct electric curing condition on the mechanical strength and microstructure of cement paste, a series of experiments were carried out to investigate the effects of alternative current voltages and frequency on compressive strength of samples. And the corresponding microstructure of samples were also analyzed by several measurements including X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and mercury intrusion porometer. The results show that alternative current electric voltage and frequency can greatly influence the early compressive strength of a cement paste. And a suitable electric curing condition can make hardened cement paste keep a steady growth of compressive strength and excellent microstructure. The Joule heat of direct electric curing on cement paste is the main reason that accelerates the hydration and improve the early strength development of sample. This study will provide an important technical support for exploring low carbon rapid electric curing method to produce green high early strength cement concrete prefabricated element.

The Effect of Alkaline Activator Components on the Properties of Fly Ash Added Pumice Based Geopolymer

The effect of sodium hydroxide (SH) concentration and sodium silicate (SS) content in alkali activator on mechanical properties and wet-dry resistance of fly ash added pumice based geopolymer paste were investigated. In the study, the concentration of SH was used as 8, 10, 12 and 14 molar, while the weight ratio of SS to SH was used as 0, 1, 2 and 3. While the density of geopolymer paste samples increased significantly with the increase of SH molarity in mixtures with low SS content, it was less affected by SH molarity in mixtures with high SS content. For all SH molarity values, the compressive strength of the geopolymer paste samples increased with the increase of the SS/SH ratio, while a slight decrease was observed with the SS/SH ratio increasing from 2 to 3. However, with the increase of the SH molarity, the compressive strength of the samples was less affected by the SS content. As large cracks or splits occur in paste samples activated only with SH under the effect of wet-dry, their compressive strength could not be measured. The wet-dry performance of the paste samples activated with SS + SH was not affected much by the SH molarity and the SS/SH ratio and were close to each other. When looking at the microstructure studies, FTIR analyzes show that SS content provides a better geopolymerization, and SEM images show that micro-cracks relatively decrease with SS content.

Elucidating the effects of silicon carbide sludge and waste glass fiber on the characteristics of porous eco‐fireproof materials

AbstractThis study used silicon carbide sludge (SCS) and waste glass fiber (WGF) to prepare SCS/WGF porous (SWP) eco‐fireproof materials by a hydrogen peroxide foaming agent. The results showed that the compressive strength of samples that were cured for 1 day and had an SCS replacement level of 10% and added amounts of WGF of 0.5% and 2.0% were 0.32 and 0.46 MPa, respectively. Additionally, it was observed that the stress–strain curves were relatively extended. WGF could improve the geopolymeric matrix of the composites in terms of formation and/or redistribution of cracks by bridging cracks and perforations within the matrix. When the added amounts of WGF were 0.5% and 2.0%, the reverse‐side temperatures of the samples were 238 and 262°C, respectively, which showed that adding an appropriate amount of WGF could effectively reduce the reverse‐side temperature of SWP eco‐fireproof materials. The results displayed the beneficial influence of SCS and WGF in improving bulking density, compressive strength, and flexural strength and in reducing porosity and thermal conductivity. Therefore, the results showed that SWP eco‐fireproof materials reinforced using SCS and WGF have potential as building materials.

Effect and mechanism of nano-Ca10(PO4)6(OH)2 additive on compressive strength of calcium aluminate cement at high temperature

Calcium aluminate cement (CAC) is widely used as a binder for refractory materials, and thus the improvement in compressive strength is of vital importance for CAC applied at high temperature. For this purpose, nano-Ca10(PO4)6(OH)2 additive with a ratio of 0.5–1.5 mass% was added with the water-cement ratio to be 0.4. X-ray diffraction and isothermal calorimetry analysis demonstrate that nano-Ca10(PO4)6(OH)2 additive can shorten the hydration process and promote the formation of main hydrates of CaAl2O4·10H2O (CAH10) and Ca2Al2O5·8H2O (C2AH8). In addition, scanning electron microscopy results suggest that nano-Ca10(PO4)6(OH)2 can protect CAH10 and C2AH8 from being destroyed during the calcination, guaranteeing that these thin lamellar crystals are intertwined to form the denser microstructure. Benefited from above effects, nano-Ca10(PO4)6(OH)2 can obviously improve the compressive strength of the CAC mortar samples cured for 7 d after calcination at 1100 °C, while the improving effect is dependent upon its contents. Especially, compared with the one without the additive, the compressive strength of the sample with 1.0% nano-Ca10(PO4)6(OH)2 is increased by 14%.

Production of autoclaved aerated concrete with silica raw materials of a higher solubility than quartz Part II: Influence of autoclaving temperature

This study examines the effects of autoclaving temperature on the mechanical and microstructural properties of autoclaved aerated concrete (AAC) containing calcined diatomaceous earth (C-DE) as the main silica source. The autoclaving process was conducted using an autoclave at various temperatures of T = 134–192 °C and a corresponding steam pressure of P = 2–12 bar for 6 hours. The resultant phases were characterized using quantitative and qualitative X-ray diffraction (XRD), differential thermal analysis (DTA) and thermogravimetric analysis (TGA). The compressive strength of samples containing C-DE as the main silica source increased by 30% when the autoclaving temperature decreased by around 60 °C. This is in complete opposition to samples containing quartz as the only SiO2 source. The compressive strength of the latter decreased by 85% when the autoclaving temperature decreased by approximately 60 °C. For all samples, changes in compressive strength corresponded with changes in tobermorite formation.

Effect of Mixed Foundry Sand and Rice Hull Ash on the Mechanical Properties of Concrete

Waste foundry sand is the by-product of metal casting industry. Rice hull which is often burned after it is removed from rice is also a by-product of the agriculture industry. Disposing of these wastes leads to the environmental pollution. To optimal use of these wastes and avoid the adverse effects of dumping them, regular sand has been partially replaced with the waste foundry sand and rice hull ash pozzolan has been also used as a partial replacement for cement in making concrete. XRF, XRD and SEM experiments, compressive strength, tensile strength (Brazilian), flexural strength, modulus of elasticity and water absorption tests have been conducted. The results showed a slight decrease in compressive strength of samples in which regular sand was replaced with waste foundry sand by 15 percent; however, adding the rice hull ash to this mixture led to make a concrete comparable with control one. Also, using foundry sand in mix designs affects their physical performance. Moreover, the use of waste foundry sand in concrete is both economically and environmentally suitable.

Evaluation of durability and compressive strength of concrete using polypropylene, E205 and polycarboxylate ether additives

Nowadays researchers are trying to simultaneously enhance the mechanical properties and durability of concrete using additives. In this study, the experimental results of the effect of admixture concrete with different percentages of polycarboxylate ether and E205 additives were investigated separately on fiber reinforced concrete with polypropylene fibers. In this regard, durability tests including electrical resistivity tests, water absorption, rapid choloride permeability test (RCPT) and compressive strength of concrete have been investigated. In addition, to study the microstructure of cement paste containing polypropylene fibers and polycarboxylate ether additives and E205 additives were used, X-ray diffraction spectroscopy (XRD) experiments, scanning electron microscopy (SEM) images and XRF chemical composition test. The results show that adding additives to the concrete admixture, reduced compared to the control sample 51% chlorine ion penetration in concrete with polycarboxylate ether and polypropylene fibers (sample A) and 36% chlorine ion penetration with E205 additive. Water absorption was reduced in samples A 27% and in samples B, 16% compared to the control sample, also the increase in specific electrical resistivity compared to the control sample was 525% in samples A and 619% in samples B. Also, the compressive strength of samples at 7 and 28 days of age increased by 134% and 56%, respectively, and the highest compressive strength in samples B at 7 and 28 days were 43% and 29%, respectively. Control sample increased. According to the results, it can be concluded that the durability and compressive strength of fibers reinforced with polypropylene fibers is increased by adding polycarboxylate ether and E205 additives.

Dynamic modulus of elasticity and compressive strength evaluations of modified reactive powder concrete (MRPC) by non-destructive ultrasonic pulse velocity method

ABSTRACT This study investigates the method of ultrasonic pulse velocity technique as a non-destructive test for concrete to estimate the mechanical properties of RPC, modified reactive powders concrete (MRPC). This study is based on data obtained from the experimental investigation done in this work and comparison with the data of previous works. After conducting pulse velocity tests on cubic samples, the relationship between pulse velocity, elastic modulus and compressive strength of samples was obtained with an acceptable approximation. Also, the validity of the proposed relation ACI 363.1 and four distinguished researchers regarding the calculation of RPC, MRPC elastic modulus and its comparison with the dynamic elasticity modulus (ASTM C 597) with respect to different materials and mix designs. The dynamic modulus of elasticity (Ed) increased on average by 19% over the modulus of elasticity (Ec). Given the lack of research on the relationship between the parameters mentioned in the MRPC, the present study is an exploratory research concerned with the relationship of these methods. Also, two new models are presented for relating these parameters.

The effect of lithium silicate impregnation on the compressive strength and pore structure of foam concrete

Foam concrete (FC) has been widely used to make slab structures, retaining walls, and backfill materials for highways, railways, plazas and other projects due to its high flowability, low cement content, cost reduction, and thermal insulation. However, the low compressive strength and durability of FC limit its further application in structural materials. This paper focuses on improving the compressive strength and freeze-thaw cycle (FTC) resistance by adjusting the pore structure. The method proposed in this paper utilizes calcium silicate hydrate gel (C-S-H) formed by the rehydration reaction between lithium silicate (LS) and calcium hydroxide (CH). In this paper, the FC samples were treated by LS solution impregnation for 6 h. LS's effects on the dry density, 7- and 28-day compressive strength, strength-to-weight ratio (S/W ratio), and FTC resistance were studied. The results show that LS enhances the properties of FC, including the S/W ratio, compressive strength, and FTC resistance. In particular, the growth rate of the sample's compressive strength varies between 4.8% and 59.5%. The growth rate of the compressive S/W ratio was between 27.0% and 52.0%. The FTC resistance is improved. Thermogravimetric (TG) analysis and pore structure analysis results show that a rehydration process to generate C-S-H was observed between CH and LS, which can optimize FC's pore structure.

Feasibility study on the use of tagouk ash as pozzolanic material in concrete

This paper reports an experimental study on the micro-structure as well as mechanical properties of concrete mixes with partial replacement of cement by Tagouk ash as a type of natural Pozzolan. Partial cement replacement by waste natural materials such as Tagouk ash would be a promising solution toward reducing greenhouse gases emissions as well as environmental pollutions. Typically found in rocky environments, Tagouk is a species of wild trees belonging to the Cannabaceae family of plants. Tagouk normally grows up to about 25 m in height and 40 cm in diameter and contains high amounts of minerals including silica and calcium, making it an ideal candidate to be used as a pozzolanic supplement in concrete. In this research, the effects of partial replacement of cement with Tagouk ash by the amounts of 5, 10, 15, and 20% of the cement weight in the mix were studied. In all mixes, the water-to-cement (W/C) ratio was considered to be constant and equals to 0.4. Also, the amount of aggregates was constant for all design mixes. The compressive strengths of all samples at the ages of 7, 28, and 90 days were recorded. Scanning of specimens was performed by using scanning electron microscope (SEM) to investigate the micro-structure, too. Energy-dispersive X-ray spectroscopy analysis (EDX), X–ray diffraction (XRD), thermo-gravimetric analysis (TGA), and Fourier transformed infrared spectroscopy (FTIR) of the samples were also studied. Results show significant enhancement in compressive strength of the concrete samples with 15% TA replacement by approximately 48% and 43% at 28 and 90 days, respectively. Moreover, the results of SEM as well as those of EDX spectroscopy demonstrate that Tagouk ash results in reducing the porosity of concrete and also forming secondary C–S–H products. It appears that Tagouk ash is an efficient natural Pozzolan for partial replacement with cement in concrete.

Study of Rock Pillar Failure Consisting of Non-Persistent Joint using Experimental Test and Fracture Analysis Code in Two Dimensions

The experimental and numerical methods were used to investigate the effects of joint number and joint angle on the failure behaviour of rock pillars under a uniaxial compressive test. The gypsum samples with dimensions of 200 mm × 200 mm × 50 mm were prepared. The compressive strength of the intact sample was 7.2 MPa. The imbeded joint was placed inside the specimen. The joint length was 6 cm in a constant joint length. There were several numbers of cracks including one, two, and three cracks. In the experimental tests, the angles of the diagonal plane with respect to the horizontal axis were 0, 30, 60, and 90 degrees. The axial load was applied to the model with a rate of 0.01 mm/s. In the fracture analysis code, the angles of the diagonal plane with respect to the horizontal axis were 0, 15, 30, 45, 60, 75, and 90 degrees. A constant axial load of 135 MPa was applied to the model. The results obtained showed that the failure process was mostly dependent on the angle and number of the non-persistent joint. The compressive strength of the samples was dependent on the fracture pattern and the failure mechanism of the discontinuities. It was shown that the tensile cracks were developed whithin the model. The strength of the specimens increased by increasing both the joint angle and joint number. The joint angle of 45° KI had the maximum quantity. The stress intensity factor was decreased by increasing the joint number. The failure pattern and failure strength were analogous in both methods, i.e. the experimental testing and the numerical simulation methods.

Определение прочностных характеристик битумоминеральных смесей

The paper presents the results of the development and testing of a laboratory method for determining the strength characteristics of bitumen-mineral mixtures on the Lintel PK-21-01 strength meter. The conditions for testing the strength of bitumen-mineral mixtures are selected. The dependence between the bitumen adhesion index and the compressive strength of samples of bitumen-mineral mixtures based on it, determined according to the developed method, is shown. A decrease in the strength and adhesive properties of the binder was found with an increase in the content of the DST-30-01 polymer in bitumen. It is proposed to evaluate the possibility of performing research for the development of new types of bitumen products, to develop various production technologies and to select the optimal parameters for its production on the basis of standardized methods of testing bitumen and the developed methodology for determining the strength characteristics of bitumen-mineral mixtures.

Characterization and reuse of spent foundry sand in the production of concrete for interlocking pavement

This paper presents the characterization of spent foundry sand mixtures (SFS-M) and a new use in the production of concrete blocks for interlocking pavement. Cylindrical and hexagonal concrete blocks were made with the total replacement of natural sand with SFS-M and their mechanical properties were evaluated. The fine aggregates were assessed by scanning electron microscopy, thermogravimetry, X-ray fluorescence and X-ray diffraction. The fresh and hardened concrete tests performed were slump, water absorption, void ratio and compressive strength. The compressive strength of samples with total replacement of natural sand with SFS-M was above 35 MPa. Water absorption was less than 6%, allowing its use as concrete pavement for light traffic. Thus, the results of this work indicated that the production of hexagonal concrete blocks with total replacement of natural sand with SFS-M is technically feasible and economically viable. The reuse of SFS reduces its disposal in landfills and also the use of natural resources resulting in less environmental impact.

Compounding and technological methods for increasing the efficiency of wood matrix mineralization

This paper presents the results of a study of the efficiency of mineralization of the plant matrix of pine wood samples by immersion of experimental samples in an organo-mineral water suspension (dispersion medium) and holding for 24 hours under natural conditions, as well as under autoclave impregnation at an excess pressure of up to 1.5 MPa. To create the necessary working pressure in the autoclave, an inert gas (argon) was used. As working fluids, we used an aqueous solution of arabinogalactan, aqueous suspension containing polymineral sand, pre-dispersed to a fine state and a soluble complex obtained by mechanical mixing of the above components. Prototypes were made from ordinary pine wood. The effectiveness of impregnation was evaluated by increasing the density of samples. In addition, data on changes in Brinell hardness, compressive strength of samples along the fibers, and water absorption of impregnated wood were obtained. It was found that autoclaving in the studied mode leads to an increase in the density of samples by more than two times, reduces their water absorption, and increases strength by 84%.

Research on the Hydration Properties of C4A3S-CSH2 Cement System at Different Temperatures.

Sulphoaluminate cement has the advantage of low-temperature application performance, but its hydration mechanism at low temperatures is not yet clear. Anhydrous calcium sulfoaluminate (C4A3S) is the main mineral in the composition of sulfoaluminate cement clinkers. In this paper, C4A3S mixed with gypsum (CaSO4∙2H2O) to form a C4A3S-CSH2 cement system; X-ray diffraction (XRD), thermogravimetric analysis (TG-DTG), scanning electron microscopy (SEM) and mercury intrusion analysis (MIP) to clarify the effect of temperatures on the hydration properties of C4A3S-CSH2 cement system. The results showed that hydration of the C4A3S-CSH2 cement system could carry on at low temperatures, even at −15 °C. The main hydration product was ettringite. Low temperatures did not change the types of the hydration products, but the low temperature of 0 °C was more favorable for the formation of ettringite. The early hydration of the C4A3S-CSH2 cement system was inhibited by the decrease in temperature. However, hydration of the cement at 0 °C continued at a high rate after one day. Morphologies of the ettringite for the C4A3S-CSH2 cement system at −15 °C were needle-like structures, while they were of columnar structure at 0 °C. The compressive strength of samples at 0 °C reached 82 MPa, which is significantly higher than that at 20 °C.