Decrease In Dry Density Research Articles

Assessment of the engineering properties of concrete prepared with aggregates developed from waste basalt mud

The development of high-performance aggregate is a key direction of sustainable concrete. One effective synthetic technology for producing artificial aggregates is hydrothermal synthesis. Using waste basalt mud from the construction of a low-carbon industrial park as a raw material further facilitates the utilization of solid waste resources. Therefore, this paper adopted the hydrothermal synthesis method to produce artificial aggregates developed from basalt mud (AABM). Subsequently, it was used to partially replace mechanical aggregate in the preparation of concrete with strength grad C30. The engineering properties of concrete prepared with AABM (C-AABM), including workability, densities, mechanical properties, and frost resistance, were investigated to assess the feasibility of using AABM as concrete aggregates. The results showed that the fluidity of C-AABM can be significantly improved by using AABM. The hardened C-AABM, prepared with 10 ∼ 30 vol% AABM instead of mechanized aggregate, exhibited a dry density decrease of less than 5 %, indicating the feasibility of using AABM for ordinary concrete. However, excessive AABM negatively affected the mechanical properties of the concrete. When the AABM substitution was no more than 15 vol%, the impact of AABM on the compressive strength and modulus of elasticity of C-AABM was less than 15 %. Nevertheless, the performance of the concrete deteriorated dramatically with the addition of AABM under freezing conditions. As described, the primary engineering advantage of preparing C30 concrete with AABM is to improve the workability of the fresh matrix without significantly reducing the mechanical properties of the hardened concrete. It proves the viability of AABM as an alternative aggregate for ordinary concrete production.

Influence of Particle Size on Compressed Earth Blocks Properties and Strategies for Enhanced Performance

In the context of sustainable building development, Compressed Earth Blocks (CEBs) have garnered increasing attention in recent years owing to their minimal environmental and economic impact. However, owing to the inherent diversity of raw soil and the production process’s reliance on expertise, the properties of these blocks are subjected to multifaceted influences. Among these, the significance of soil particle size variation often remains overlooked, leaving its impact ambiguous. This study endeavours to address this gap in existing research by delving into this aspect. Two distinct batches of CEBs were produced by adjusting the grain size curve of a single type of sieved soil with different maximum mesh openings: 2 mm for R1 CEBs and 12.5 mm for R2 CEBs. Experimental results reveal significant differences in thermophysical characteristics: on average, R1 blocks show superior thermal performance, boasting a 23% reduction in thermal conductivity compared to R2 blocks, and are lighter, with an 8% decrease in dry bulk density. Although no significant changes in mechanical parameters were observed, finer-structured R1 blocks showed a 25% greater tendency to absorb water due to changes in their porous structure. This study sheds light on the sensitivity of thermal parameters to changes in soil particle size and shows that blocks with finer particles exhibit poorer heat conduction and heat diffusion. Besides providing new insights into the literature, this research also provides a strategic approach to optimise the thermophysical properties of CEBs. By understanding the influence of particle size, researchers and practitioners can now develop strategies to enhance these properties and improve the overall performance of CEBs.

Laboratory Evaluation of the Hydraulic Conductivity as a Function of Changes in the Particle Size of a Cubitermes Sp Termite Mound Soil Treated with Lime

This work characterizes the geotechnical properties and microstructure that served as a fundamental and more practical basis for describing the hydraulic conductivity of the lime-treated cubitermes sp termite mound soil. The results show that changes in particle size lead to a decrease in dry density and linear swelling. Permeability is strongly correlated with particle size distribution and compaction. Permeability increases up to the lime fixation point obtained at 6% of the lime content. Compaction for micropore reduction in treated soil is higher than in raw soil. The treated soil has a denser internal structure with agglomerations of dispersed clay particles. The increase in compaction energy reduces macropores and permeability, and the soil microstructure becomes homogeneous. Natural soil is highly impermeable, and soil-lime mixes are among the least draining materials. Higher values of hydraulic conductivity were obtained as a function of time. Soil and mixtures can be used in civil engineering works (earthworks). Correlations between hydraulic conductivity and particle size fractions are polylinear fits with R2 (0.962-0.993) and the Slogistic1 model with χ²(2.06E-15) for the mean silt fraction. This study is decisive for predicting hydraulic conductivity from the geotechnical properties of the soil, by solving the mathematical expressions of the models used.

Macroscopic and microscopic analysis of the effects of moisture content and dry density on the strength of loess.

To clarify the impact of moisture content and dry density on the strength of loess, the remolded loess samples with different moisture content and dry density were prepared, and the influence of moisture content and dry density on loess strength was explored from the macro level by direct shear test without suction control. On this basis, the mechanism of the influence of moisture content and dry density on loess strength was explored from the micro level by nuclear magnetic resonance method. The research results indicate that: In the case of low water content, there are peak points in the stress-strain curve of remolded loess, exhibiting strain softening characteristics. In the case of high water content, there is no obvious peak in the stress-strain curve, exhibiting strain hardening characteristics. Moisture has a significant impact on the shear strength of remolded loess. As the moisture content of the soil sample increases, the cohesion decreases significantly, and the change in internal friction angle is not obvious. As the moisture content continues to increase, the free water content continues to increase. Free water will continuously soften the soil particle structure, reduce the bonding force between soil particles, and cause the cohesion to decrease with the increase of moisture content. The change in dry density also has a significant impact on the shear strength parameters of remolded loess. As the dry density of the soil sample increases, the cohesion increases. The smaller the dry density, the larger the pore ratio, and the looser the contact between soil particles, weakening the bonding effect. The larger the pore ratio, the more bound water is converted to free water, and the strong bonding force between the water film and soil particles disappears. Both of these microscopic factors can lead to a decrease in cohesion with a decrease in dry density.

Flexural behavior of glass fiber reinforced cement incorporating foam

Glass fiber reinforced cement (GRC) incorporating foam has good thermal insulation. Micro pores not only lowered the strength of the cement matrix but also changed the friction between the fiber and the matrix. It has an influence on modulus of rupture (MOR) and fracture energy of GRC. In this work, the effect of the glass fiber and foam contents of GRC on the MOR and fracture energy were evaluated using four-point flexural tests. The results show that glass fiber content has little influence on MOR of GRC. However, the MOR decreased significantly with increasing foam content. The empirical formula summarized by experiments can well characterize the relationship between the MOR and density of foamed GRC. The content of glass fiber and foam has a significant influence on the fracture energy of GRC. The fracture energy of foamed GRC decreased with the decrease of dry bulk density, and the decrease was fast and then slow.

Performance Assessment of Pile Models Chemically Grouted by Low-Pressure Injection Laboratory Device for Improving Loose Sand

The complexity and partially defined nature of jet grouting make it hard to predict the performance of grouted piles. So the trials of cement injection at a location with similar soil properties as the erecting site are necessary to assess the performance of the grouted piles. Nevertheless, instead of executing trial-injected piles at the pilot site, which wastes money, time, and effort, the laboratory cement injection devices are essential alternatives for evaluating soil injection ability. This study assesses the performance of a low-pressure laboratory grouting device by improving loose sandy soil injected using binders formed of Silica Fume (SF) as a chemical admixture (10% of Ordinary Portland Cement OPC mass) to different (W/C) water/cement ratios (by mass materials) mixes. Trial grouting processes were executed to optimize the practical ranges of the operating factors of the laboratory device to obtain consistent grouted model pile samples. The paper examined the relations of the binders' W/C ratios with the densities, elasticity modulus (E), and Uniaxial Compression Stress (UCS) of the grouted piles. The investigation results show that as the binder W/C ratio rises, the grouted pile samples' dry density, E, and UCS values decrease. For the binder injected with a W/C ratio of one and 10% SF additive by weight of cement mass, the highest values of the grouted pile for density, E, and UCS were about 2.32 g/cm3, 23 MPa, and 2000 MPa, respectively. The UCS of the grouted pile proved that the binders' W/C ratios and the SF addition have an evident effect on the investigated factors of the grouted piles.

Investigation on the Engineering Properties of Peat Soil Stabilised Using Lime Stabilisation and Alkaline Activation

Peat soil is typically classified as a problematic soil due to its expansive behaviour that possesses geotechnical drawbacks. Thus, the condition of peat soil must be improved prior to any construction works. Stabilisation of peat soil can be done via chemical stabilisation and alkaline activation while incorporating industrial by-products or wastes as addictive. This study aims to investigate the effect of press mud as an additive in lime-stabilized and alkaline activator-stabilized peat soils. Press mud is a by-product of sugarcane juice filtering. The lime adopted is at 3 % and 5.5 % while the alkaline activator is used in cold and warm condition. A total of 5 percentages of press mud have been employed, namely 0%, 0.25%, 0.5%, 1% and 2%. The investigations revealed that regardless of the percentage of lime adopted, the optimum moisture content increases while the maximum dry density decreases when the percentage of press mud incorporated is increased. However, when the lime content is increased, the optimum moisture content increases significantly. The UCS of lime-stabilised peat soil sample achieved the greatest strength improvement when the lime and press mud is used at 5.5% and 0.25%, respectively. In contrast, the unconfined compressive strength (UCS) of 3% lime-stabilised peat soil samples with or without press mud shows comparable 28-day strength. On the other hand, the UCS of peat soil stabilised with alkaline activator shows significant improvement, while addition of press mud further improves the strength. Nonetheless, using warm alkaline activator improves the early strength development but cold alkaline activator results in higher 28-day UCS.

Enhancement of Gypseous Soil Engineering Properties Through High-Density Polyethylene Polymer Addition: A Comprehensive Experimental Assessment

An experimental investigation was conducted to scrutinize the influence of high-density polyethylene (HDPE) polymer on the engineering properties of gypseous soil. Soil samples, possessing 38% gypsum content, were extracted from the Tikrit region, Iraq, and were subsequently subjected to varying HDPE polymer concentrations of 1%, 3%, and 6%. An observed augmentation in the maximum dry density was noted when a minuscule quantity of 1% HDPE polymer was incorporated. However, a subsequent increase in polymer concentration resulted in a discernible decrease in dry density. Examination via the double oedometer test elucidated a significant reduction in collapse potential by 64%, 77.7%, and 83.2% upon addition of 1%, 3%, and 6% HDPE polymer, respectively. Direct shear test outcomes revealed a complex influence of HDPE polymer on soil cohesion. In the dry state, a 1% and 6% HDPE polymer addition led to a cohesion increase by 50% and 16.67%, respectively, whereas a 33.3% decrease was observed at a 3% polymer concentration. Conversely, in the soaked state, cohesion was found to decrease by 50% at 1% and 6% HDPE polymer concentrations, and entirely diminished with a 3% polymer addition. Interestingly, the internal friction angle (ϕ) exhibited an increase in both dry and soaked states with escalating HDPE polymer percentages. A contradictory behavior was noted in the California Bearing Ratio (CBR), which decreased in the dry state but increased in the soaked state with a rise in HDPE polymer ratios. In conclusion, the present study substantiates that the addition of HDPE polymer induces modifications in the engineering behavior of gypseous soil. Further research is encouraged to optimize the HDPE polymer concentration for ground enhancement applications.

Engineering properties on salt rock as subgrade filler in dry salt lake: Water retention characteristics and water migration patterns

As a special road material, salt rock has high strength and stability in arid areas, and has broad application prospects in highway engineering construction in dry salt lake areas. To investigate the water retention characteristics of salt rock and its water migration patterns under the covering effect, and to ensure the long-term durability of salt rock subgrade, this study presents a comprehensive analysis of the effect of initial dry density on the water retention characteristics of fine-grained salt rock fillers. The soil–water characteristic curve model of salt rock was recommended. The capillary water migration patterns of salt rock were proved. The water migration patterns of salt rock under freeze–thaw cycles were clarified. The hydrothermal state of salt rock subgrade under the influence of pavement overburden was evaluated based on the field monitoring. The results indicated that the water retention capacity of fine-grained salt rock filler increases with the decrease of initial dry density during the high suction stage. The Fredlund & Xing model is recommended to address the soil–water characteristic curve of fine-grained salt rock. The capillary action of salt rock filler decreases with increasing compaction. The temperature gradient from the upper boundary to the bottom of the soil column under the effect of freeze–thaw cycles is significant. After five freeze–thaw cycles, the water in the soil column continued to migrate upwards under the covering effect and temperature gradient. The relative humidity and temperature of the salt rock subgrade both show a sinusoidal cyclical variation. When the temperature range of salt rock subgrade is −6°C–30 °C, the relative humidity of subgrade is significantly correlated with temperature. This study can provide theoretical support for the disaster prevention and control of salt rock subgrade covering effect in the Lop Nor area.

IMPROVEMENT OF HIGH PLASTICITY CLAY BY USING FILTER SLUDGE

Filter sludge (FS) is a waste material that occurs during sugar production in the sugar industry, and since it is not used anywhere, it creates a problem due to storage costs and environmental damage. In the present study, high plasticity clay was stabilized with a filter sludge which has never been used for soil stabilization in field cases. The changes in the geotechnical properties of a high plasticity clay (CH) with the additive of filter sludge (FS) were investigated. The amount of FS mixed into CH soil is 3-6-9-12-15% by dry weight of the soil. Changes in geotechnical properties such as consistency limits, compaction parameters, strength, swelling potential, CBR value of improved soils were determined. The plastic limit and optimum water content increase as the FS content added to the soil increases; liquid limit, plasticity index, and maximum dry density decrease. Improved soil strength increases as the curing time and FS amount increase, and the highest strength was obtained with 15% of FS. At the optimum additive ratio, the unconfined compressive strength increases by 33%. The swelling percentage of CH clay decreases from 42.5% to 20%. According to the wet CBR test results, the bearing capacity of the improved soil increased from %1.1 to %4.4. As a result of this study, it was seen that the FS waste material improved the geotechnical properties of the soil.

Effects of Graphene on Soil Water-Retention Curve, van Genuchten Parameters, and Soil Pore Size Distribution—A Comparison with Traditional Soil Conditioners

Graphene waste has had enormous growth due to many industrial applications. Agriculture exploits waste through the circular economy, and graphene waste is thereby investigated in this study as a soil conditioner for improving the physical–hydraulic properties of soil. Experiments were performed on three differently textured soils amended with traditional soil conditioners (compost, biochar, and zeolites) and graphene. The conditioners were applied at two different doses of 10% and 5% dry weight (d.w.) for compost, biochar, and zeolites, and 1.0% and 0.5% d.w. for graphene. We compared (i) the major porosity classes related to water-retention characteristics (drainage, storage, and residual porosity), (ii) bulk density, and (iii) van Genuchten water-retention curve (WRC) characteristics. Graphene application caused the largest decrease in dry bulk density (ρb), lowering the soil bulk density by about 25%. In fact, graphene had ρb of 0.01 g/cm3. The effects of graphene were more intense in the finer soil. Compost and biochar showed similar effects, but of lower magnitude compared to those of graphene, with ρb of 0.7 and 0.28 g/cm3, respectively. Although zeolites had ρb of 0.62 g/cm3, they showed quite different behavior in increasing the mixtures’ ρb. Graphene and biochar showed the most pronounced effects in the clayey soil, where storage porosity showed a reduction of >30% compared to the control. For storage porosity, the graphene treatments did not show statistically significant differences compared to the control. The results show that, when the conditioner increased drainage porosity, there was a high probability of a concomitant reduction in storage porosity. This finding indicates that graphene use for improving soil aeration and drainage conditions is viable, especially in fine soils.

Physical and mechanical properties of foamed concrete with recycled concrete aggregates

A large amount of waste concrete is produced during old city reconstruction. In order to realize the lightweight reuse of recycled concrete aggregate, a new preparation scheme of foamed concrete is proposed. Through single-factor tests, the effects of recycled coarse aggregate (RCA) gradation, RCA volume ratio, water-cement ratio and foam content on the preparation process and performance of RCA foamed concrete (RCAFC) were explored. The results showed that RCA grade has significant influence on the performance of RCAFC. Grading level Ⅲ (i.e., the mass ratio of five-type aggregates sized, respectively, 9.5–16 mm, 16–19 mm, 19–26.5 mm, 26.5–31.5 mm and 31.5–37.5 mm is 2:4:8:3:3) can reduce the water absorption by 4.6%, increase the compressive strength by 6.0%, and decrease the difficulty of sample preparation compared with the natural grading. The increase of RCA volume fraction is directly proportional to the compressive strength and inversely proportional to the water absorption. With the raising of water-cement ratio, the fluidity of foamed concrete paste increases linearly, the dry density decreases, the water absorption decreases first and then increases, and the compressive strength increases first and then decreases. The increase of foam content is inversely proportional to fluidity, dry density and compressive strength, and it is directly proportional to water absorption. Among the above four factors, the grade of RCA has the greatest impact on the early strength of the sample, whilst the content of foam is the smallest.

Development of lightweight aggregate geopolymer concrete with shale ceramsite

This paper developed a lightweight aggregate geopolymer concrete (LAGC) with shale ceramsite. 18 groups of LAGC specimens with 3 sand ratios (30%, 40% and 50%) and 6 aggregate contents (10%, 20%, 30%, 40%, 50% and 60%) were prepared. A series of static tests (dry density test and uniaxial compression test) and dynamic tests (ultrasonic pulse velocity test) were performed to achieve the dry density, compression strength and P-wave velocity. The effects of sand ratio and aggregate content on the dry density, compression strength and P-wave velocity were discussed. Two optimal mix proportions for the LAGC were proposed. The results show that the dry density and P-wave velocity increase as sand ratio increases. The compressive strength increases then decreases as sand ratio increases. In addition, the dry density and compressive strength decrease as aggregate content increases. The P-wave velocity increases as aggregate content increases. The LAGC with the sand ratio of 30% and aggregate contents of 30% reaches the dry density of 1378.0 kg/m3 and compressive strength of 18.5 MPa. The LAGC with the sand ratio of 30% and aggregate contents of 40% reaches the dry density of 1348.0 kg/m3 and compressive strength of 16.8 MPa. Both of the proportions satisfied the engineering requirements, which are recommended for the potential application in the construction.

Investigate the Fresh and Hardened Properties of Shotcrete Concrete Contains Different Types of Plastic Fibers

Adding fibers to the shotcrete concrete mixes is very important to increase the load carrying capacity, toughness, and reducing crack propagations by bridging the cracks. On the other hand, this fiber has an effect on the fresh and hardened properties of shotcrete. In this study, fresh properties evaluated by using slump flow, , and segregation resistance tests. Hardened properties included testing of air voids, dry density, water absorption, ultrasonic pulse velocity (UPV), compressive strength, and flexural strength. This works including two types of fibers in three forms (waste plastic (PET)fibers only, polypropylene fibers (PP) only, and hybrid fiber (PET and PP)), each form added by three percentages (0.35%, 0.7%, and 1%) by volume.The results showed that the addition of 1% of all types of fiber has a negative impact on fresh properties. Especially in shotcrete containing waste plastic fiber. Also, all specimens containing fibers showed a decrease in the ultrasonic pulse velocity (UPV) and an increase in air voids and water absorption compared to the reference specimens. Also, the results clarify that the addition of waste plastic fiber to shotcrete led to a slight decrease in dry density. The highest increasing in compressive strength of shotcrete recorded by about 8.2% with using 0.35% PP fiber and highest decreasing was 20.9% with using 1% waste plastic fiber. the highest increasing in flexural strength was 62 with using 1% PP fibers.

Influence of Utilization of Fly Ash as Sand Replacement Agent in Sustainable Flexible Pavement

The current investigation work has investigated the utilization of Fly Ash (FA) in soil improvement and to assess the impacts of addition of various rates of FA on the sample of unsaturated soil. Effect of fly ash addition has been investigated on moisture content, degree of compaction and densities of unsaturated soil by directing different experiments. In the primary phase samples have been prepared with included FA in the percentages of 12%, 17%, 22%, and 27% respectively. Moisture content and densities experiments have been conducted without addition of FA for reference value. Each experiment was carried out with the mixtures having their optimal moisture content (OMC) and their maximum dry density (MDD). With the increase in percentage of water the degree of compaction, Dry density as well as bulk density has been increased up to a certain limit beyond this shows reverse result. Decrease in dry density was higher as compared to bulk density of the sample while increase in moisture content has been observed with the addition of FA in the sample. Addition of fly ash up to a certain limit shows good agreement for utilization as sand replacement or additives in civil application for sustainable applications.

Improvement of Gypsiferous Soils Properties by Hydrated Lime in the Najaf City, Middle of Iraq

This study includes the effect of lime addition on the engineering properties of gypseous soil taken from a part of the Najaf- Karbla plateau (52, 48, 72% gypsum). Also this study shows increase in the proportion of gypsum in the soil in the northwest direction of the study area. Maximum dry density and optimum moisture content (2.065, 2.025 and 2.003) at 15%, 14% and 15% respectively for the three samples. The maximum dry density decrease while optimum moisture content increases with increasing ratio of hydrate lime. The results show that the gypscous soil becomes non - plastic when treated by > 3 % of hydrated lime. Cohesion Force, with the increase in the percentage of lime from 3% to 6%, after which it decreases as the percentage addition of lime to reach zero when the addition became 9%. The reason for this is that the lime increases the cohesion strength between molecules to the limit of adding 6%, then the cohesion decreases to zero when 9% is added lime. The results of a liquid limits are changed and the soil becomes more liquidity limit when it's treated due to the hydrated lime increases liquid limits significantly, and it becomes clear that the limit of liquidity. After which the lime molecules work to separate the molecules from each other, and the cohesion force decreases. It is also noted that the internal friction angle decreases with the increase in the percentage of lime.

Development and characterization of sustainable concrete incorporating a high volume of industrial waste materials

Recycling waste materials instead of using traditional construction materials in civil infrastructure and buildings is a significant step toward reducing greenhouse gas emissions and the consumption of natural resources. The scope of this research is to identify the properties of sustainable concrete where waste materials such as rubber tires, crushed clay bricks, and crushed glass can be utilized to replace the fine or coarse natural aggregate with substitution percentages of 25, 50, and 100 % by volume. Slump, compressive strength, elastic modulus, impact resistance, density, and sorptivity tests were performed. In addition, scanning electron microscopy (SEM) and X–ray diffraction (XRD) were studied to determine the microstructure properties of concrete. The rubberized concrete mixes showed worse workability, while crushed clay brick and crushed glass concrete showed good workability. The decrease in dry density was 55 % less than the control mix when rubber aggregate was used, while it reached 17 % and 4 % when crushed clay brick and crushed glass aggregate were used, respectively. The compression strength and elastic modulus decreased as waste content increased, except for the fine glass mix. The compression strength of the fine glass mixture was 5.58 % greater than that of the control mixture. The sorptivity of sustainable concrete increased when the amount of waste increased, and its value ranged from 2.7 × 10–3 to 16.5 × 10–3 mm/s½ compared to the control mix, whose value was 2 × 10–3 mm/s½. The findings of this investigation demonstrated that the studied waste materials can be used to produce either sustainable lightweight concrete without severe deterioration of mechanical properties or conventional concrete with better mechanical performance.

EFFECT OF WASTE GLASS ADDITION AS A REPLACEMENT OF SAND ON PROPERTIES OF ECO-FRIENDLY POLYMER MORTAR

Polymer concrete is a fine aggregate bound with a polymer binder instead of cement as in conventional concrete. The main aim of this research is investigation some properties (compressive strength, direct tensile strength, dry density) of epoxy polymer mortar with recycled glass as partial replacements of normal sand. According to the findings of this study, waste glass was substituted for 5%, 10%, 15%, and 20% of the sand in polymer mortar, respectively. When using waste glass as an alternative to natural sand, a decrease in dry density is observed when compared to the reference mixture by 2.14%, 2.23%, 2.32% at 7 days, 14 days and 28 days, respectively. Addition of 5%, 10%, 15% and 20% of waste glass as a partial substitute for natural sand leads to improvement the mechanical properties (direct tensile and compressive strength) of eco friendly polymer mortar. The results showed that recycled glass with 20% replacement ratio has given best results when compared with reference mix and other ratios. Finally, a regression analysis is used to establish the link between tensile strength and compressive strength.

Correlation assessment between degradation ratios of UCS and non-destructive properties of rock under freezing-thawing cycles

Bedrocks of engineering projects are commonly affected by freezing-thawing (F-T) process in mountainous areas. Consequently, determining the degradation rate of rocks due to F-T cycles in cold areas has a key role in project design and its safety level. In this research, influence of F-T process on some physico-mechanical characteristics of three main rocks of Angouran mine (limestone, amphibolite-schist, and mica-schist) was investigated. For this purpose, unconfined compressive strength (UCS), Schmidt hardness, dry density, water absorption and porosity were firstly determined at five different F-T cycle numbers between 0 and 75 cycles. Increasing of the F-T number led to decrease of UCS, Schmidt hardness and dry density, whereas water absorption and porosity parameters were increased. It is also proved that the UCS loss of rock samples due to the F-T process was related to the losses of other physic-mechanical properties. Therefore, the changes of UCS losses were determined at 0, 7, 15, 40, and 75F-T cycles to establish their relationships. According to the results, after 75 cycles, there is a good relationship between UCS degradation ratio with those of the water absorption and Schmidt hardness (R2 = 0.99).

Eco-friendly concrete with chemically treated end-of-life tires: Mechanical strength, shrinkage, and flexural performance of RC beams

The disposal of waste end-of-life vehicle tires has become a major environmental issue around the globe, as it is not completely biodegradable and can be a massive threat to the environment. Several researchers have attempted to use tires as aggregate with and without chemical treatment. However, to the best of the authors' knowledge, no research has investigated the performance of clay brick aggregate (CBA) concrete by replacing the CBA with bleached powder-treated waste rubber tire aggregate (WRTA) at different treatment times. Within this context, this study examines the mechanical strength, shrinkage, and flexural performance of reinforced concrete (RC) beams made with seven replacement percentages (0, 5, 10, 15, 20, 30, and 50 % by volume) of CBA by WRTA treated with H2O, NaOH, and bleaching powder (BP) for 2 h and 72 h. The experimental outcomes reveal that as the percentage of untreated WRTA increases, the slump, dry density, and mechanical strength decrease. Furthermore, concrete shrinkage increases with the increasing content of untreated WRTA in the mix. Likewise, the flexural load of RC beams declines with an increased percentage of untreated WRTA. It has been observed that the concrete made with WRTA treated with NaOH and BP has significantly higher mechanical strength, a flexural load carrying capacity of RC beams, and lower shrinkage compared to the untreated WRTA. The improvement in all properties was more remarkable for the treatment with BP than NaOH and treatment of 72 h than 2 h. The findings reveal that 15 % WRTA treated with BP solution for 72 h can be used as a CBA replacement whose design strength is not significantly high (fcat28days ≈ 20 MPa).