Compressive Strength Of Specimens Research Articles

Effect of GBFS ratio and recycled steel tire wire on the mechanical and microstructural properties of geopolymer concrete under ambient and oven curing conditions

In this study, the effects of waste steel wire ratios, granulated blast furnace slag (GBFS) ratios, and different curing methods on geopolymer concrete (GPC) were investigated. For this purpose, 12 mixtures were produced and eight of them were cured under ambient conditions and the remaining four were cured in an oven. Steel wire ratios and GBFS ratios were added to GPC as 0–1–2–3 % and 0–10–20 % by volume and weight, respectively. As a result of the mixtures, cubes, cylinders, and beams were obtained and these elements were subjected to compression, tensile, and flexural tests. As a result of the tests, the compressive strengths of the specimens were obtained as 8.5 %, 19.7 %, and 24.9 % for ambient curing and 10.4 %, 23.2 %, and 32.2 % for oven curing, respectively, as the steel wire fiber increased from 0 % to 3 %. The maximum compressive strength of the oven-cured specimen with 3 % steel wire fiber was measured as 42.56 MPa. The tensile strength of GPC also increased as the steel wire increased. The highest tensile strength was obtained with 3 % steel wire. In addition, oven curing conditions increased the tensile strength more than ambient curing. The flexural strength (FS) increased by 21.3 %, 29.4 %, and 33.8 % with increasing steel wire ratios of 1 %, 2 %, and 3 %, respectively. The FS was further increased by oven curing conditions and the maximum FS was achieved with 3 % steel wire. In ambient curing conditions, a successful geopolymerization was achieved due to the high calcium content in the samples containing 20 % GBFS. This allowed to obtain similar strengths between ambient curing and oven curing. Although the oven curing values were higher, similar results were obtained for the samples cured in an ambient containing 20 % GBFS. As a result of the study, mixtures containing 3 % steel wire and 20 % GBFS provided sufficient strength without oven curing and increased the usability of GPC under ambient conditions.

Study on resistance of basalt fiber reinforced concrete to sulfate erosion after cryogenic freeze-thaw cycles

This study aims to investigate the mechanical properties of concrete structures, such as liquefied natural gas (LNG) storage tanks, subjected to the effects of cryogenic freeze-thaw cycles and erosive environmental conditions. Mechanical properties of basalt fiber reinforced concrete (BFRC) with normal temperature (25 °C) and different temperature gradients (25 °C ∼ -80 °C, 25 °C ∼ -160 °C), fiber content (0 %, 0.1 %, 0.2 %), and sulfate erosion days (0, 60, 120) were determined. The morphology of the eroded specimens was examined, and the microstructural characteristics were investigated by scanning electron microscope (SEM). The findings revealed that the introduction of basalt fiber (BF) in the concrete significantly changes the failure mode following sulfate erosion, causing specimens to fail by ductile failure rather than brittle failure. Moreover, the mechanical properties of concrete specimens decreased significantly with increasing temperature gradients of freeze-thaw cycles. Under non-erosive conditions, the compressive strength of plain concrete after undergoing freeze-thaw cycles from 25 °C to -160 °C decreased by 22.4 % compared to plain concrete that did not undergo freeze-thaw cycles, and the tensile strength decreased by 32.5 %. Adding fibers increased the mechanical properties of specimens. Specially, after undergoing freeze-thaw cycles from 25 °C to -160 °C and being subjected to 120 days of sulfate erosion, compared with plain concrete, the compressive strength of specimens with 0.2 % fiber content increased by 20.6 %, the tensile strength increased by 37.8 %, while also increasing flexural toughness. In addition, the sulfate erosion days also had a considerable impact on the deterioration of the mechanical properties of specimens. Specially, after undergoing freeze-thaw cycles from 25 °C to -80 °C and being subjected to 120 days of erosion, the eroded specimen with 0.1 % fiber content, the compressive strength decreased by 10.9 %, the tensile strength decreased by 11.6 % compared to specimens that were not eroded, while also decreasing flexural toughness. Combined with the experimental results, the strength deterioration models of BFRC related to the sulfate erosion days and BF content were proposed at 25 °C, after freeze-thaw cycles from 25 °C to -80 °C, and after freeze-thaw cycles from 25 °C to -160 °C. The aim is to provide some data reference for the development and application of BFRC in cryogenic environments.

Utilization of Crushed Waste Glass as a Partial Replacement for Sand in Cement Mortar for a Sustainable Environment

The disposal of non-biodegradable waste glass poses a serious environmental threat as it can cause soil, water, and air pollution when not properly discarded in landfills. The use of glass in construction has shown promising results in enhancing various properties of concrete and improving overall sustainability. This study investigated the mechanical properties of mixed colored glass, comprising green and brown hues, and clear glass in mortar, to explore the feasibility of using colored glass as a replacement for sand and to determine how the addition of color affects the mechanical properties of mortar. The incorporation of waste glass as a partial replacement for sand resulted in a 2.7% increase in flow table values when 5% of Mixed Colored Glass Sand (MCGS) was utilized in place of sand, as compared to the control mix (CM). Conversely, a 5.4% and 4.7% decrease in flow table values were observed when 15% of clear glass (CGS) and MCGS were used as a substitute for sand respectively. When 15% of MCGS and CGS were replaced with sand, compressive strength increased by 60% and 42.6% respectively, compared to the control mix, when 5% MCGS, 10% MCGS, 5 CGS, and 10% CGS were observed. After 28 days of curing, a 10.6% and 10% increase in strength was observed when 10% of MCGS and CGS were replaced. At 7 days, a 3.3% increase in flexural strength was found when 5% of MCGS was replaced with sand was observed. The fire resistance test showed reduced mass and compressive strength of specimens at different temperatures. No significant expansion of ASR was recorded throughout the test period. The use of waste glass as a substitute for sand has shown improvements in environmental sustainability and economics. When 10%WGS and 15%WGS were utilized, 20% and 30% of waste glass sand was replaced with sand, respectively. Incorporating waste glass into construction enhances the mechanical properties of concrete and promotes the conservation of natural resources and environmental sustainability. This study examined the economic advantages of replacing sand with waste glass and found that CM has the highest cost of 90.64 Tl. At replacement of 5%, 10%, and 15% MCGS showed 1.07%, 1.96%, and 2.95% savings compared to the control mix, respectively. Moreover, replacing 5%, and 10% of natural sand with clear glass sand could bring about savings of 1.91%%, and 3.63%, respectively. Replacing 15% CGS showed the highest savings of 5.45% compared to the control mix. The study compared the use of colored and clear glass as a partial replacement for sand and found that there were slight differences in the results, but overall they were similar.

Compression test and size effect study of defective wood

ABSTRACT Wood, as a natural material, inevitably contains initial defects such as knots, cracks, and decay, which are important factors affecting its mechanical properties and cannot be ignored. In order to investigate the influence of initial defects on the compressive mechanical properties of wood, Norway spruce was selected as the research object. Wood specimens without and with initial defects were prepared, and uniaxial compression tests were conducted. Combined with Digital Image Correlation (DIC) and finite element analysis, the compressive mechanical properties of defective wood were studied. The results showed that compared to defect-free specimens, specimens with defects exhibited a shortened elastic stage in the load-displacement curve, and the rate of decrease in load after reaching the peak was lower than that of defect-free specimens. For specimens of the same size, the compressive strength of specimens with defects was lower than that of defect-free specimens. The established finite element model could effectively simulate the compressive failure process of wood with initial defects, validating the effectiveness of numerical simulation. Bažant's size effect theory can be used for size effect analysis of the compressive strength of wood with initial defects in the longitudinal direction.

Synthesis of geopolymer mortar from biomass ashes and forecasting its compressive strength behaviour

The global warming dilemma raised an exigency toward sustainability in the construction industry and compelled scientists to hunt for alternative binders in construction materials. The, geopolymerization as a spectacular technology has arisen as a looming solution to this dilemma. This work assesses the features of geopolymer mortar developed with both industrial and agricultural wastes at ambient temperature curing. The geopolymer mix proportion was evolved in this study using main precursor material as fly ash, ground granulated blast furnace slag (GGBFS), sugarcane bagasse ash (SCBA) or rice husk ash (RHA). Workability and mechanical properties, including compressive strength, flexural strength, and split tensile strength of different mortar mixes with various percentages of RHA and SCBA for 365 days, were evaluated. Geopolymer mortar with 10 % SCBA and 5 % RHA achieved improvements of 25 % and 13.91 % in compressive strength, 10.6 % and 3.5 % in flexural strength, and 35 % and 16.8 % in split tensile strength, respectively. Good geopolymer gel formation is clearly evident from the SEM images of SCBA mortar. The main polymeric bonds Si–O–Al and Si-O-Si are also identified using FTIR. To assess the efficacious use of biomass ashes, resistance to chemical attack using H2SO4, HCl, Na2SiO3, and NaCl solutions for 365 days was studied. It was revealed that SCBA incorporated geopolymer mortar specimens achieved good resistance compared with RHA geopolymer mortar. The relation between the ambient temperature cured geopolymer specimen compressive strength at 28 days and 365 days chemical solution curried geopolymer specimen compressive strength find out using python and obtained R2 values more than 95 %. Also, this research proposed various machine learning techniques such as long short-term memory, support vector regression, random forest regression, XGBOOST, and AdaBOOST algorithms for the prediction of compressive strength of geopolymer using 724 mixture proportions with diverse curing temperatures and varying ages. The XGBOOST algorithm achieved the highest R² value of 0.92, demonstrating its effectiveness for the strength prediction.

An Investigation of the Mechanical and Durability Properties of Hollow Concrete Blocks Made with Copper Mine Tailings as a Partial Cement Replacement

The increase in copper productivity in Zambia has resulted in the expansion of disposal areas occupied by mineral wastes and tailings. This not only consumes land but also, due to insufficient management, poses negative environmental impacts and health risks to people. Therefore, efficient and sustainable approaches for the proper management of these waste materials must be developed. In this study, the potential utilization of copper mine tailings was assessed. After analyzing the physical and chemical properties of copper mine tailings from Kitwe Tailings Dam (TD25), hollow concrete block specimens were prepared. Copper mine tailings were used as a partial replacement for cement in the mix design, with replacement ratios as follows: 0% for CBCMT O% (control specimen), 10% for CBCMT1O%, 20% for CBCMT2O%, 30% for CBCMT3O%, 40% for CBCMT4O%, and 50% for CBCMT5O%, all aimed at achieving a target strength of 5 MPa. Specimen compressive strength was evaluated, and it was found that CBCMT1O% and CBCMT2O% achieved the target compressive strength at 28 days of age. Water absorption rates and resistance to acid attack were also assessed. Findings revealed that all specimens outperformed the control specimen in terms of these properties. Furthermore, the environmental feasibility of the hollow concrete blocks specimens was examined, and the results showed limited leaching of heavy metals from the specimens, with concentrations within permissible thresholds. Additionally, a statistical analysis was conducted to study the influence cell shape has on the specimens’ compressive strength. Aimed at identifying the optimal specimen type for achieving compressive strength at an early age, results indicated that cell shape had a significant impact on the 28-day age of hollow concrete blocks. The study proposes a novel copper mine tailings (waste) management approach, by utilizing the potential it has to replace cement in the production of hollow concrete blocks, evident from the observed enhancement of the mechanical and durability properties.

On the low-velocity impact properties of CFRP/HAFRP interlayer hybrid fibre composite laminates

Hybrid fibre-reinforced polymer composites have been increasingly utilised in key engineering fields, such as the manufacture of aerospace structures, due to their high specific strength, stiffness, and design flexibility. This paper attempts to investigate the low-velocity impact performance and residual strength after impact of hybrid composites consisting of carbon fibre-reinforced polymer (CFRP) and heterocyclic aramid fibre-reinforced polymer (HAFRP). Since carbon fibres are brittle and vulnerable to impact loading despite their ultra-high strength, the aim of this study was to enhance the impact resistance of CFRP by hybridising it with high-toughness heterocyclic aramid fibres. The influence of hybrid layup configuration on the performance of both low-velocity impact and compression after impact (CAI) was explored. Four types of specimens, including pure CFRP and hybrid CFRP/HAFRP laminates with different layups, were manufactured and tested. Drop-weight impact tests were conducted on the specimens under impact energies of 25 J, 30 J and 40 J to measure the impact response, such as force-displacement and energy absorption curves. The internal impact damage was then assessed by ultrasonic C-scan method. The compressive strengths of specimens were measured both before and after low-velocity impact. The results indicated that hybrid laminates had better impact resistance than pure CFRP specimens, and the reduction in the compressive strength after impact for pure CFRP specimens was 2–4 times that of hybrid specimens. Therefore, hybridisation of heterocyclic aramid fibre with carbon fibre in composite laminates can retain high strength of carbon fibre while benefiting from the excellent fracture toughness of heterocyclic aramid fibre.

Mechanical Properties of Lightweight EPS Self-compacting Concrete Reinforced with Steel Fibers

This study aims to evaluate experimentally the mechanical characteristics of Self-Compacting Concrete (SCC) comprising expanded polystyrene beads (EPS) to produce flowable lightweight concrete reinforced with steel fibers. In this paper, the effect of steel fibers and EPS content on the fresh and hardened mechanical properties of SCC specimens, using two percentages for Polystyrene aggregate replacement (25% and 50%) and three values for volume fraction of steel fiber content (0%, 0.75%, and 1.5%), were examined. Fresh mixture properties were determined using slump flow, L-box, and V-funnel tests. Mechanical properties for hardened samples were obtained using standard specimens for compressive strength, density, split, and flexural strength. The study showed that EPS content has no adverse effect on the rheological features of the SCC. However, workability falls below specification limits when adding steel fibers to SCC. Results revealed that using 25% of EPS content resulted in lightweight structural concrete, while lightweight moderate-strength concrete was produced using 50% of EPS content. Furthermore, the study has shown that the split and flexural tensile strength were reduced substantially by 53% and 60% due to EPS addition. However, adding steel fibers remarkably improved the indirect tensile strength and Modulus of rupture by 46% and 80%, respectively. The mode of failure of the concrete specimens containing EPS beads and steel fibers did not show brittle failure behavior generally encountered in normal-weight concrete, indicating a more ductile behavior.

Impact of basic oxygen furnace slag on the hydration microstructure, mechanical properties, and carbon emissions of supersulfated cement

Supersulfated cement (SSC) is recognized as a cementitious material with low CO2 emissions, consisting predominantly of ground granulated blast-furnace slag (GGBS) and a minor activator content. The production of GGBS production constitutes the primary source of CO2 emissions in SSC. In contrast, carbon emissions from the production of basic oxygen furnace slag (BOFS) are lower, and BOFS inherently exhibits substantial carbonization potential. Therefore, in this study, BOFS is employed as a replacement for GGBS in formulating an innovative low-emissions binder denoted as BOFS-modified supersulfated cement (BMSC). This study investigates the influence patterns of BOFS substitution for GGBS on the strength properties of BMSC. Furthermore, a series of experiments involving QXRD, TGA, SEM, and MIP were conducted to systematically investigate the mechanistic impact of BOFS on the hydration microstructure of BMSC. The findings reveal that substituting 10 % of GGBS with BOFS contributes to an enhancement in both flexural and compressive strength of specimens at 7 and 28 days. BOFS exerts a positive influence on the formation of ettringite in BMSC. The C2S and C4AF within BOFS also demonstrate distinct hydration activity. Additionally, BOFS can reduce large pores in the early hydration paste and contribute to narrowing the average pore size. Moreover, the evaluation of the Global Warming Potential (GWP) demonstrates that the replacement of slag with BOFS can lead to a further reduction of up to 30 % in the carbon emissions of SSC.

A novel magnetic approach to improve compressive strength and magnetization of concrete containing nano silica and steel fibers

Novel exploratory research was conducted on the utilization of a new method to optimize the magnetic effect on the compressive strength of concrete specimens containing nano silica and steel fibers. According to the results of previous experiments, this research investigated the compressive strength of 7- and 28-day concrete with different amounts of nano silica and steel fiber in the non-magnetized mode and also after applying the innovative Pre-Post technique (applying both pre- and post-magnetization modes to a specimen), on the other hand, the magnetic susceptibility of this type of concrete was also investigated by increasing the magnetic flux density by 1 T, which was not investigated in previous studies. Based on this, it was proved that adding nano silica of up to 10 % as a substitute for cement and 1 % of steel fiber, increases the compressive strength by 88.79 % and 59.69 % in 7- and 28-day specimens respectively, as well as increasing the magnetic flux density is positively related to the compressive strength of specimens, meaning that with the increasing of this parameter up to 1 T, the compressive strength also enhanced by 152.26 % and 114.03 % for specimens containing 10 % nano silica and 1 % steel fibers in 7- and 28-day specimens respectively, in addition of this, it was evaluated that the rate of increment of the compressive strength in the 7-day specimens was higher than the 28-day ones. Using the results of this experiment, it is noteworthy that adopting the presented pre-post technique in addition to improving the performance of pre-magnetized concrete containing fiber in smart structures equipped with electromagnetic systems, can compensate for the negative effects of using large amounts of additives such as nano silica substituted with cement on compressive strength.

Evaluating the Structural Performance of Concrete Beams Made of Waste Plastic Aggregates

Abstract: This study investigates the potential of using plastic waste as a partial replacement for aggregates in concrete production, aiming to address the dual challenges of unsustainable construction practices and the global accumulation of plastic waste. With an emphasis on sustainability and waste management, the research explores the effects of incorporating different percentages of plastic waste (0%, 5%, 10%, 15%, and 20%) on the mechanical properties, durability, workability, and thermal behavior of concrete. The methodology encompasses the collection and preparation of plastic waste, formulation of concrete mixes with varying levels of plastic waste replacement, and comprehensive testing of the prepared specimens for compressive strength, flexural strength, split tensile strength, workability (slump test), durability (freeze-thaw cycles), impact resistance, and thermal conductivity. The analysis of results reveals that while the inclusion of plastic waste in concrete leads to a reduction in mechanical strengths, it simultaneously improves workability, durability against freeze-thaw cycles, impact resistance, and thermal insulation properties

The Mechanical Properties and Mechanisms in Contact-Hardening Behavior of Silica-Alumina Mine Solid Waste

There are some limitations in the application of tuff powder as a supplementary cementitious material (SCM). Exploring its feasibility in new fields will consume a large amount of silica-alumina mine solid wastes. This study has investigated the mechanical properties and mechanism in contact-hardening of tuff powder with a method of compression molding. The compressive strength of specimens was tested, and the X-ray diffraction (XRD), thermogravimetric analysis (TG), scanning electron microscopy (SEM), and Mercury intrusion porosimetry (MIP) methods were used to reveal the mechanism of contact-hardening of tuff powder from a micro-perspective. The results indicated that the compressive strength of specimens was higher when activated by sodium hydroxide compared to calcium hydroxide. Compared to calcium hydroxide, the compressive strength of TFS20 and TFF20 activated by sodium hydroxide was improved by 20% and 23%, respectively. The hydration degree of tuff powder was very low, with a water–cement ratio (w/c) of 0.15, while the hydration degree of coal gangue powder was higher. The results of TGA and SEM indicated that the sodium hydroxide had a better activating effect on slag and fly ash. Therefore, more C-S-H gels were generated in those samples activated by sodium hydroxide. Furthermore, the structure of samples was more compacted, and there was a reduction of porosity by 10% and 11% for TFS20 and TFF20, respectively, especially the proportion of harmful pores.

Preparation of concrete from vitrified slag: process parameter optimization and characterization

ABSTRACT Vitrification is the safest and most effective method for treating solid waste incineration residues, and the utilization of vitrified slag can promote recovery of waste resources. By using the response surface methodology to comprehensively consider the impact of three factors – cement substitution ratio, water-binder ratio, and sand rate – on the strength of concrete, the optimal process parameters for predicting the maximum 28-day compressive strength of concrete specimens are determined as follows: 5% cement substitution ratio, 0.69 water-binder ratio, and 40% sand rate. The experiments demonstrate that concrete specimens prepared by partially replacing cement with molten glass slag exhibit excellent mechanical and physicochemical properties. As the curing age increases, the compressive strength of the specimens also enhances. Leaching test results showed that the concrete test block met groundwater Class III quality standards, and the addition of vitrified slag powder reduced the content of calcium hydroxide and improved concrete performance.

A Comparative In Vitro Analysis of Antimicrobial Effectiveness and Compressive Strength of Ginger and Clove-Modified Glass Ionomer Cement.

Background Glass ionomer cement (GIC) is widely recognized for its self-adhesive characteristicsand biocompatibility, making it commonly used as a restorative material. However, challenges related to limited antibacterial effectiveness and relatively low mechanical properties have hindered its widespread clinical use. Cloveand ginger are recognized for their potent antimicrobial activity against numerous pathogenic microorganisms. The present study aims to enhance the clinical applicability of GIC by modifying it with clove and ginger extract. Aim The objective of the study is to assess the antimicrobial effectiveness and compressive strength of GIC modified with ginger and clove extract. Materials and methods Ginger and clove extracts were prepared and incorporated into conventional GIC at three concentrations for each, creating ginger-modified GIC groups (Group A, Group B, and Group C) and clove-modified GIC groups (Group D, Group E, and Group F), with Group G as the control (conventional GIC without modification). The antimicrobial assessment was conducted on disc-shaped GIC specimens (3.0 mm height x 6.0 mm diameter) prepared using molds. Bacterial strains were used to evaluate antimicrobial properties, with minimum inhibitory concentration (MIC) assays conducted at intervals of one to four hours for both modified and unmodified groups. Compressive strength specimens were prepared using cylindrical molds (6.0 mm height × 4.0 mm diameter), according to the ISO (International Organization for Standardization) guidelines. The evaluation was conducted using a Zwick universal testing machine (ElectroPuls®E3000, Instron, Bangalore, India), with the highest force at the point of specimen fracture recorded to determine compressive strength. Statistical analysis was conducted utilizing a one-way analysis of variance (ANOVA) alongside Tukey's post hoc test, with a significance threshold set at p < 0.01. Results The antimicrobial effectiveness of clove and ginger-modified GIC was assessed through a MIC assay, revealing a statistically significant improvement in antimicrobial potency against Streptococcus mutans and Lactobacillus within the modified groups compared to the control group (p < 0.01). Increased extract concentration correlated with enhanced antimicrobial activity. Clove-modified GIC exhibited superior antimicrobial efficacy compared to ginger extract. Compressive strength was higher in clove-modified GIC groups (p < 0.01), with Group F showing a maximum value of 175.88 MPa, while other modified groups demonstrated similar results to the control, with a value of 166.81 MPa (p > 0.01). Conclusion The study concludes that both clove-modified GIC and ginger-modified GIC exhibited antimicrobial activity against Streptococcus mutans and Lactobacillus species. The antimicrobial activity was notably higher in clove-modified GIC compared to ginger-modified GIC. Additionally, the compressive strength of clove-modified GIC surpassed all other groups. Thus, clove-modified GIC emerges as a promising restorative material for addressing recurrent caries. Future investigation is necessary to assess the long-term durability of the material.

The Unconfined Compressive Strength of Hy-drated Lime Stabilized Clayey Soil at Different Water Contents and Different Curing Times

This research was done to find out how adding hydrated lime and extra water content to clayey soil samples affecting their unconfined compressive strength (UCS). The clayey soil is a locally available soil from the clayey soil area in Cyrene, northeastern of Libya. In the soil samples, hydrated lime (HL) was added at a rate of 5% of the dry weight of the soil. The standard compaction test was conducted on the untreated natural soil sample “NS” so that the optimum water content at the maximum dry density can be determined wop1. Because of the addition of hydrated lime to the soil will affect the dry density-water content relationship, the standard compaction test was conducted again on the treated soil sample “NS+5%HL” to determine another optimum water content wop2. These optimum water values {wop1 =17.8 &amp; wop2=19.5} will be used to prepare unconfined compressive strength specimens. In the experimental work two soil mixtures will be used beside the natural soil mixture. The first mixture "NS+5%HL+wop1" and the second mixture "NS+5%HL+wop2" were prepared in addition to the natural soil mixture "NS+wop1". All unconfined compressive strength specimens for the first and second mixtures were extracted and tested at 7 and 14 days of curing, then comparison were made. The first mixture, "NS+5%HL+wop1" will be compared with the natural soil mixture, "NS+ wop1" in order to understand the impact of HL addition. The effect of the water content changing can be seen when the second mixture, "NS+5%HL+wop2" is compared with the first mixture, NS+5%HL+wop1. According to the findings, Although the first mixture’s specimens have the least dry density value, the UCS values increased by 218.5 and 386.5% at 7 and 14 days of curing, respectively, when compared to the natural soil mixture. This illustrates the result of the added hydrated lime. At curing times of 7 and 14 days, respectively, the UCS values for the second mixture fell by 8.61 and 14.11% when compared to the first mixture. And this illustrates the impact of variations in water content.

Valorization of glass waste as partial substitution of sand in concrete – Investigation of the physical and mechanical properties for a sustainable construction

Over the past few years, the valorization of industrial waste and by-products has become an essential issue due to the increasingly stringent regulations regarding the environmental protection and sustainable development. For the purpose of reducing our dependence on virgin raw materials, it was deemed interesting to consider the recycling and valorization of glass, which has high silica content, to develop new construction materials. Its use as a substitute raw material in the field of construction materials has attracted research attention, particularly the concrete industry adopts a number of methods to achieve this goal. In this context, a purely experimental study was conducted to investigate the physical and mechanical properties of fresh and hardened concrete at different curing times (3, 7 and 28 days) using different dosages of glass sand as a partial substitute for natural sand at 10%, 20%, and 30% and to determine the optimal composition of glass powder as a partial replacement for sand against the compressive strength of concrete. while maintaining a constant water-to-cement (W/C) ratio. An overall quantity of 9.5 kg of crushed waste glass was used with 264 kg of concrete mixes. The workability, density, slump, content air tests and strength properties were analyzed in terms of waste glass content in terms of waste glass content. This substitution results in concrete with favorable workability. Despite the absence of air-entraining agent, the concrete mixtures have air content between 2.3% and 1.9% and the density, is still comparable to the control mixes. The compressive strength of specimens with 20% waste glass content and the flexural strength of specimens with 10% waste glass content represented respectively 96% and 86% than of the control specimen at 28 days. The results proved a pozzolanic strength activity given by waste glass after 28 days for 10% and 20% of replacement of natural sand (0/1 mm). The results obtained indicate that glass can serve as a quality substitute for sand in concrete. These original achievements pave the way for more sustainable and environmentally friendly concrete mixes while addressing the inherent challenges of using glass waste in construction and infrastructure works

Synergistic effect of CO2-mineralized steel slag and carbonation curing on cement paste

Cement-based materials have favorable capacity of solid waste and CO2 disposal. In this study, a synergistic CO2 treatment, including CO2 mineralization of steel slag admixture and carbonation curing of cement paste, was proposed. The influence of synergistic CO2 treatment on pozzolanic activity of steel slag, CO2 sequestration, and compressive strength of specimens were investigated. Results show that synergistic CO2 treatment cannot significantly increase the compressive strength but can improve the CO2 sequestration efficiently (up to 10.76 %), while a single CO2 treatment could only improve CO2 sequestration by 6.75 %. MIP, 29Si NMR, XRD-rietveld, and Raman spectroscopy were used to determine the effect of synergistc CO2 treatment on microstructure and mineral composition of samples. A barrier layer generated on the surface of steel slag particle was observed in SEM images. This barrier layer composed of carbonates reduces the early activity of CO2 mineralized steel slag.

Influence of hygiene tissue paper used as an additive on the physicochemical and mechanical properties of CO2-cured belite-rich cement paste

The present study investigated the fresh, hardened, and physicochemical properties of CO2-cured belite-rich cement (BRC) paste incorporating hygiene tissue paper (HTP) as an additive. HTP was added at 0.5% and 1.0% by wt. of BRC paste. The BRC paste was prepared at a water-to-cement ratio of 0.4 and cured under water and carbonation. The results demonstrated that upon carbonation, the incorporation of HTP at 1.0% increases the CO2 uptake and compressive strength of specimens by 18.60% and 22.29%, respectively. A pore structure analysis shows a decrease in the threshold pore size diameter with an increase in the HTP content for CO2-cured samples. An SEM analysis revealed precipitation and impregnation of calcites in and around the HTP microfiber particles. The incorporation of HTP under water curing on the other hand did not significantly influence the strength or the physicochemical properties. It was observed that HTP contributes to improving the properties of CO2-cured BRC paste in two ways; the porous structure of HTP provides pathways for the deep permeation of CO2 into the matrix, and the surface of HTP offers an additional area for calcite precipitation.

Efficient healing of existed cracks in cement via synergistic effects of cement matrix activation and monomer polymerization

The effective repair of existing cracks can prolong the service life of infrastructures, which is of great significance for energy saving and emission reduction. A great deal of research on self-healing cement has been undertaken to efficiently prevent possible future cracking problems in buildings, but these methods do not deal with existing cracks. Herein, the efficient healing of existing cracks is achieved by the synergistic reaction of cement matrix activation and organic polymerization of sodium acrylate (ANa). ANa polymerization was systematically investigated for its effect on stimulated calcium silicate hydrate (C-S-H) and true healing systems in this study. The interconnected porous structure of sodium polyacrylate (PANa) observed during study suggested that ANa had been polymerized successfully under room temperature and the denser short rod-like C-S-H was also formed during the polymerization process. The formation of this organic-inorganic hybrid structure facilitates the rapid healing of existing cracks. When applied to cement, results showed that the compressive strength of specimens with the healing agent SS/PANa recovered 119.99% of its original strength and the micro-cracks of approximately 50 μm were completely sealed after 7-day curing. The ANa in the cracks helps enhance the reactivity of matrix and the polymerization improves the binding ability, forming an organic-inorganic composite network of the PANa and C-S-H. The composition and microstructure of the healed area revealed that the healing products were mainly composed of calcite (CaCO3), calcium hydroxide (CH), C-S-H and PANa.

Size effect and lateral pressure effect on the mechanical resistance of columnar jointed basalt

To reveal the size effect and lateral pressure effect of columnar jointed basalts (CJBs), the meso-damage mechanics, statistical strength theory, continuum mechanics and digital image correlation are combined, and a series of heterogeneous numerical models of CJBs orthogonal and parallel to column axis are established. The elastic modulus, Poisson's ratio, uniaxial compressive strength, friction angle, residual strength coefficient, heterogeneity index of basalts 60 GPa, 0.2, 120 MPa, 56.15°, 0.1 and 5, respectively. The gradual fracture processes and acoustic emission characteristics of CJBs suffering various lateral pressures are numerically simulated under the axial loading rate of 0.05 mm/min, and the influence of model size on the anisotropy and lateral pressure effect of CJBs is analyzed. The results show that: for the direction I/Ⅱ orthogonal to column axis, when the lateral pressure is 2 MPa and 6 MPa, the critical value of size effect is 4 m and 6 m, respectively; for the direction parallel to column axis, the compressive strength of specimen can be obviously improved by increasing lateral pressure for the certain sizes; when the lateral pressure is 6 MPa and the distance ratio of the secondary joint set is 0% or 50%, the compression strengths of the 3 m and 6 m specimens change in a U-shape and a V-shape with the column dip angle increasing, respectively. The results can contribute to understanding the non-linear deformation and failure behaviors of CJBs.