Dry Density Research Articles

Recycling water treatment sludge into a novel eco-friendly core–shell lightweight aggregate and its application

Disposal of water treatment sludge (WTS) has become an important issue of global environmental concern due to problems and costs. This study explored the feasibility of cold-bond methodology to produce an eco-friendly core–shell lightweight aggregate (LWA) from WTS, expanded perlite (EP), and cement. The effect of cement and WTS content on the properties of the LWA was studied. The findings revealed that the crushing strength, loose bulk density, 24-h water absorption, and 28-d water absorption of produced LWA ranged from 0.45 to 3.1 MPa, 1.05 to 1.25 g/cm3, 12.4 to 22%, and 22 to 27%, respectively. In addition, increasing the WTS content in the shell has a positive impact on the pH of the produced LWA. Furthermore, the SEM microstructure graphs revealed the efficient interference in the LWA particles between the cement–WTS composite and the perlite. The results also prove the possibility of using the produced LWA to produce structural lightweight concrete, with compressive strength, splitting tensile strength, and dry density of 24 MPa, 2.98 MPa, and 1840 kg/m3, respectively, with a consistent thermal conductivity of 0.72 W/m K and good acoustic insulation.Graphical abstract

Optimization of Controlled Low-Strength Material from Multi-Component Coal-Based Solid Waste

Recently, controlled low-strength material (CLSM) has been considered an easy-to-mix material, and the raw material is usually derived from solid waste, suggesting lower production costs. Moreover, the resource utilization of waste fosters the sustainable advancement of both society and the environment. In the present work, a CLSM with excellent performance was developed by adopting fly ash, bottom ash, desulfuration gypsum, and cement as the main cementitious materials, as well as gasification coarse slag and coal gangue as aggregates. An orthogonal experiment with three factors and three levels was designed according to the ratio of cement to binder, the contents of water, and the water-reducing agent. Further, the macroscopic properties of flowability, dry density, bleeding, compressive strength, fresh density, porosity, and absorption rate of the CLSM mixtures were tested. To optimize the CLSM proportion, the ranges of three indicators of CLSM were calculated. Experimental results manifested that the fresh and dry densities of the mixtures were within the range recommended by ACI 229. The optimal levels of cement–binder ratio (i.e., the ratio of cement to binder), water content, and water-reducing agent content are 0.24, 248 kg·m−3, and 0.80 kg·m−3, respectively. Under this condition, the flowability was 251 mm, the bleeding was 3.96%, and the compressive strength for 3 d, 7 d, and 28 d was 1.50 MPa, 3.06 MPa, and 7.79 MPa, respectively. Furthermore, the leaching values of eight heavy metals in CLSM and raw materials were less than the standard requirements, indicative of no leaching risk.

Machine learning optimization of bio-sandcrete brick modelling using response surface methodology

In this study, raw grinded groundnut shell (RGGNS) was used as a fine aggregate in the brick industry to reuse agricultural waste in building materials. In this study, an experimental approach was used to examine a new cement brick with raw groundnut shells integrated with compressive strength, water absorption and dry density optimization utilizing response surface methodology (RSM). The raw ground-nut shell content improved the fine aggregate performance of the 40%, 50%, and 60% samples. The 28-day high compressive strength with the raw ground-nut shell was 6.1 N/mm2 maximum, as needed by the technical standard. Samples made from 40%, 50%, and 60% raw groundnut shells yielded densities of 1.7, 2.2, and 1.9 kg/cm3 for groundnut shell (GNS) brick, respectively. A product's mechanical properties meet the IS code standard’s minimum requirements. RSM was then utilized to develop a model for the addition of raw groundnut shell to concrete. R-square and Adeq precision values indicated that the results are highly significant, and equations for predicting compressive strength, water absorption, and dry density have been developed. In addition, optimization was performed on the RSM findings to determine the efficiency optimization of the model. Following the optimization results, experiments were conducted to determine the applicability of the optimized model.

The Effect of Kevlar Fibers on the Mechanical Properties of Lightweight Perlite Concrete

Fiber-reinforced concrete contains a fibrous material that increases its structural cohesion. The use of separate short fibers distributed in a random direction improves the strength of Lightweight Concrete (LWC) without exceeding its upper-density limit, improving its high fragility and mechanical properties compared to Natural-Weight Concrete (NWC). This study investigated the effect of adding Kevlar 49 fibers with three percentages of cement weight, 0.5, 1, and 1.5%, on the workability, dry density, and tensile and compressive strength of LWC. The use of Kevlar fibers in different proportions improves mechanical properties, significantly increases durability, and reduces the workability of LWC. The increase in compressive strength when adding 0.5% fibers was 19 and 15% and when adding 1% was 10 and 6%, after 7 and 28 days, respectively. At 1.5%, after 7 and 28 days, there was a decrease in compressive strength due to fiber agglomeration. Additionally, increasing the fiber dose from the optimal value caused a sharp decrease in workability by 37-40%.

Belowground Response of a Bahiagrass Pasture to Long-Term Elevated [CO2] and Soil Fertility Management.

Effects of rising atmospheric CO2 concentration [CO2] on pastures and grazing lands are beginning to be researched, but these important systems remain understudied compared to other agronomic and forest ecosystems. Therefore, we conducted a long-term (2005-2015) study of bahiagrass (Paspalum notatum Flüggé) response to elevated [CO2] and fertility management. The study was conducted at the USDA-ARS, National Soil Dynamics Laboratory open-top field chamber facility, Auburn, AL. A newly established bahiagrass pasture was exposed to either ambient or elevated (ambient + 200 µmol mol-1) [CO2]. Following one year of pasture establishment, half the plots received a fertilizer treatment [N at 90 kg ha-1 three times yearly plus P, K, and lime as recommended by soil testing]; the remaining plots received no fertilization. These treatments were implemented to represent managed (M) and unmanaged (U) pastures; both are common in the southeastern US. Root cores (0-60 cm depth) were collected annually in October and processed using standard procedures. Fertility additions consistently increased both root length density (53.8%) and root dry weight density (68.2%) compared to unmanaged plots, but these root variables were generally unaffected by either [CO2] or its interaction with management. The results suggest that southern bahiagrass pastures could benefit greatly from fertilizer additions. However, bahiagrass pasture root growth is unlikely to be greatly affected by rising atmospheric [CO2], at least by those levels expected during this century.

Impacts of forestry drainage on surface peat stoichiometry and physical properties in boreal peatlands in Finland

Management of drained peatlands may pose a risk or a solution on the way towards climate change mitigation, which creates a need to evaluate the current state of forestry-drained peatlands, the magnitude of degradation processes and indicators for carbon (C) loss. Using a large dataset (778 profiles, 891 peat samples, collected between 1977 and 2017) from peatlands having different fertility classes across Finland, we investigate whether the surface peat profiles of undrained and forestry-drained peatlands differ in C:N, von Post and dry bulk density. The utility of element ratios (C:N:H stoichiometry) as site indicators for degradation were further analyzed from a subsample of 16 undrained and 30 drained peat profiles. This subsample of drained sites had carbon dioxide (CO2) and methane (CH4) fluxes measured allowing us to link peat element ratios to annual C gas effluxes. Element ratios H:C, O:C and C:N and degree of unsaturation (combining C, N, H changes) were found widely valid: they captured both differences in the botanical origin of peat as well as its potential decomposition pathway (C lost via a combination of dissolved organic C and C gas loss and/or the gaseous loss predominantly as CO2). Of the stoichiometric indexes, peat H:C ratio seemed to be the best proxy for degradation following drainage, it indicated not only long-term degradation but also explained 48% of the variation in annual CO2 emission. The O:C ratio positively correlated with annual CH4 flux, presumably because high O:C in peat reflected the availability of easily degradable substrate for methanogenesis. The differences in C:N ratio indicated notable decomposition processes for Sphagnum-dominated peatlands but not in Carex-dominated peatlands. Degree of unsaturation showed potential for an integrative proxy for drainage-induced lowering water table and post-drainage changes in peat substrate quality.

Slope Stability Analysis of Xanthan Gum Biopolymer Treated Laterite Soil Using Plaxis Limit Equilibrium Method (PLAXIS LE)

The landslides or slope failures are responsible for many fatalities and significant delays in travel by blocking the roads. The soil properties such as cohesiveness, angle of internal friction, and bulk unit weight are the primary parameters responsible for land stability and should be considered for the analysis. In this paper, a Xanthan Gum (XG) biopolymer is applied to the laterite soil to improve its engineering properties. The Plaxis Limit Equilibrium (LE) 2D software is utilized to analyze the slope's stability. Four section/ paths of the Lote Parshuram Ghat in the Ratnagiri area of Maharashtra, India are taken for the analysis. It is observed that the application of the XG to the soil which is exposed to atmosphere (normal condition) and submerged conditions improves the strength of the soil and stability of slopes. When compared to conventional laterite soil in its natural state, the cohesiveness of soil treated with XG at concentrations ranging from 1 to 5% is greatly improved, increasing from 250.51% to 378.64%. XG-treated laterite soil has a maximum dry density of 1.72 gm/cc, 28.36% higher than untreated soil. Submerged XG-treated soil often shows a factor of safety (FOS) improvement of across 57.25%. The slope stability analysis revealed that the optimum percentage of xanthan gum as a stabilizer for the submerged slope condition is 2.7% that increase the factor of safety. In case of normal condition, the factor of safety (FOS) and strength of the laterite soil increases with the reinforced percentage of xanthan gum.

Modelling rapid non-destructive test using light weight deflectometer on granular soils across different degrees of saturation

This study introduces an advanced finite element model for the light weight deflectometer (LWD), which integrates contact mechanics with fully coupled models. By simulating LWD tests on granular soils at various saturation levels, the model accurately reflects the dependence of the LWD modulus on dry density, water content, and effective stress. This model addresses and overcomes the limitations of previous finite element models for this specific problem. Simultaneously, this research presents the first experimentally validated fully coupled contact impact model. Furthermore, the research provides a comparative assessment of elastoplastic and nonlinear elastic models and contrasts an enriched node-to-segment method (developed in this study) with the more precise mortar technique for contact mechanics. These comparisons reveal unique advantages and challenges for each method. Moreover, the study underscores the importance of careful application of the LWD modulus, emphasising the need for sophisticated tools to interpret soil behaviour accurately.

Impact of Rice Husk Ash on the Compaction Characteristics of Soil

Usually, the measurement of maximum dry density (MDD) and optimum moisture content (OMC) is important for assessing the quality control of the compacted fill or earthwork constructions as the compaction parameters. Rice husk ash (RHA), plentifully available in many rice-producing countries, can be used as a building material. This study mainly tries to investigate the effect of RHA on compaction features of sandy soil classified as A-2-4 or SM for soil stabilization. Nominal to a maximal dosage of RHA addition in the soil was considered for the experiments by the standard Proctor compaction tests. The result revealed that by increasing the amount of RHA in the soil, MDD was reduced and OMC increased significantly. It can be concluded that applying a soil-RHA combination is beneficial to soil improvement. Jagannath University Journal of Science, Volume 10, Number II, Dec. 2023, pp. 87-93

BEHAVIOR OF PHYSICAL AND DENSITY PROPERTIES OF SOFT SOIL STABILIZED WITH NICKEL SLAG

Soft soils have become a significant challenge in geotechnical engineering, due to their low bearing capacity and susceptibility to deformation. Chemical stabilization using nickel slag is an alternative solution and is considered more environmentally friendly. This article focuses on the utilization of nickel slag as a binder material aimed at behavior of physical and mechanical properties of soft soil stabilized with nickel slag soft soil. The nickel slag was carried out with variations of 3%, 6%, 9% and 12% by weight of soil. All the test using ASTM procedure in order to gain physical and mechanical value. The results of this study showed that plasticity index decrease with the increasing of slag nickel concentration, where it is an indication of a change in soil consistency, shifting from initially soft to now medium. Futher, the optimum dry density (d-opt) value of the original soil used was 1.09 gr/cm3, while the optimum dry density (d) values at 3%, 6%, 9% and 12% nickel slag addition were 1.12 gr/cm3; 1.15 gr/cm3; 1.19 gr/cm3 and 1.22 gr/cm3, respectively. These results show that the presence of nickel slag can increase influence the physical and density properties of soft soil, which indicates that nickel slag has the potential to be used as a stabilization material in soft soil.

Estimating dynamic compressive strength of rock subjected to freeze-thaw weathering by data-driven models and non-destructive rock properties

ABSTRACT The dynamic compressive strength (DCS) of frozen-thawed rock influences the stability of rock mass in cold regions, especially when rock masses are possibly disturbed by dynamic loads. Laboratory freeze-thaw weathering treatment is usually time-consuming, and the dynamic strength test is destructive. Therefore, this paper attempts to quickly predict the DCS of frozen-thawed sandstones using data-driven methods, non-destructive rock properties, and basic environmental parameters. The sparrow search algorithm (SSA), gorilla troops optimiser, and dung beetle optimiser were chosen to develop two hyperparameters in the random forest (RF). The classic RF, back propagation neural network, and support vector regression models were taken as the control group. These six models were developed to predict the DCS. Their prediction results were compared. Finally, the sensitivity analysis was carried out to assess the significance of all input variables. The results indicate that the SSA – RF model yields the best prediction result, and three optimised models have better performance than single machine-learning models. Strain rate, dry density, and wave velocity are found to be the three most important parameters in DCS prediction, which further indicates that there is also a strong correlation between the characteristic impedance of the rock and the DCS.

Building MLR, ANN and FL models to predict the strength of problematic clayey soil stabilized with a combination of nano lime and nano pozzolan of natural sources for pavement construction

The current study aims at predicting the strength of the problematic clayey soils treated with combinations of pozzolan of natural sources and lime powder when added as soil additives at a nano scale. Multiple linear regression (MLR), artificial neural networks (ANN) and fuzzy logic (FL) tools were employed in the analytical study. The variables of the present study include the following: nano pozzoaln of natural source (NNP) content, nano lime content (NL), median particle size of NNP, active silica content of NNP (SiO2active), Initial liquid limit (ILL) and initial plastic limit (IPL) of the investigated soils. NNP was added at five percentages, i.e. 0%, 0.5%, 1%, 1.5% and 2%, while NL was added at five percentages, i.e. 0%, 0.3%, 0.6%, 0.9% and 1.2%. Three median particle sizes namely 50, 100 and 500 nm size were studied. Based on the different investigated soils and combinations, 120 soil mixtures were prepared and tested. California bearing ratio (CBR) and plasticity index (PI) were particularly examined. CBR tests were conducted at a soaked condition on specimens compacted to a maximum dry density (MDD) at the optimum moisture content (OMC). PI values were obtained following the Atterberg limits test. Based on the results of the performance criteria of the developed predictive models, it can be concluded that the CBR and PI of the expansive clayey soils can be effectively predicted using ANN and FL techniques. The results obtained by MLR were far from those obtained by both ANN & FL. In addition, ANN tool was slightly more accurate than FL as far as prediction of CBR and PI is concerned. The higher capability of ANN & FL models in predicting CBR & PI values, which generally obtained through time-consuming and expensive tests, could be useful for geotechnical engineers to assess or design a new pavement project. Further, it is recommended to do a re-evaluation of the current study in future, particularly when more data is available in the literature.

Non-destructive multi-sensor core logging allows for rapid imaging and estimation of frozen bulk density and volumetric ice content in permafrost cores

Abstract. Permafrost cores provide physical samples that can be used to measure the characteristics of frozen ground. Measurements of core physical properties, however, are typically destructive and time intensive. In this study, multi-sensor core logging (MSCL) is used to provide a rapid (∼2–3 cm core depth per minute), high-resolution, non-destructive method to image and collect the physical properties of permafrost cores, allowing for the visualization of cryostructures and estimation of frozen bulk density, magnetic susceptibility, and volumetric ice content. Six permafrost cores with differing properties were analyzed using MSCL and compared with established destructive analyses to assess the potential of this instrument both in terms of accuracy and relative rate of data acquisition. A calibration procedure is presented for gamma ray attenuation from a 137Cs source that is specific to frozen-core materials. This accurately estimates frozen bulk density over the wide range of material densities found in permafrost. MSCL frozen bulk density data show agreement with destructive analyses based on discrete-sample measurements, with an RMSE of 0.067 g cm−3. Frozen bulk density data from the gamma attenuation, along with soil dry bulk density measurements for different sediment types, are used to estimate volumetric ice content. This approach does require an estimation of the soil dry bulk density and assumption of air content. However, the averaged results for this method show good agreement with an RMSE of 6.7 %, illustrating MSCL can provide non-destructive estimates of volumetric ice contents and a digital archive of permafrost cores for future applications.

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.

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.

Predicting resilient modulus: A data driven approach integrating physical and numerical techniques

Resilient modulus (MR) is an important parameter in the design of pavement that helps to characterize the quality of sub-grade materials. Generally, it is not determined experimentally due to time consuming, uneconomical, laborious and lack of advanced equipment in many laboratories. The aim of this research is to determine MR values using experimental (Ultrasonic pulse velocity (UPV) and Cyclic Triaxial) and Artificial neural network (ANN) techniques. For experimental study twenty-four soil samples comprising of coarse and fine-grained soils were collected from different locations. For ANN modelling, Input variables comprised of essential soil Atterberg limits (liquid limit, plastic limit, plasticity index) and compaction properties (maximum dry density, optimum moisture content). The validation of ANN model is done by comparing its results with the experimentally evaluated MR from UPV and Cyclic Triaxial test. Experimental results showed that Cyclic Triaxial test yielded resilient modulus value that was 5 % more than obtained from the UPV test. Moreover, results showed that modulus of resilience (MR) values determined by UPV, and artificial neural network (ANN) modelling have significant closeness with the cyclic triaxial results of resilient modulus; thus, making it a significant development in predicting resilient modulus efficiently.

Evaluation of citric acid-treated natural fibres as sustainable additives for improving expansive soil performance in highway construction

This study addresses the evaluation of citric acid-treated natural fibres as sustainable additives for improving soil performance in highway construction. A series of tests were conducted on the soil to assess its baseline properties. The natural soil exhibited a Plasticity Index (PI) of 30 and Linear Shrinkage of 12%, along with a Liquid Limit (LL) of 65 and Plastic Limit (PL) of 35. Additionally, the fines content (<0.075 mm) and sand content (0.075–4.7 mm) were determined to be 79.6% and 20.4%, respectively. The soil's mineral composition included Quartz (5%), Orthoclase (3–5%), Montmorillonite (2.6%), and Illite (18.2%), with key components identified through chemical analysis: SiO2 (52.721 wt%), Fe2O3 (16.132 wt%), and Al2O3 (15.202 wt%). Subsequently, a range of tests were performed with varying additives to assess their impact on the soil's engineering properties. The sample containing 6% Sawdust (SD) additive exhibited notable improvements in multiple aspects. This sample achieved a maximum dry density (MDD) of 1856 kg/m³, surpassing the control (1900 kg/m³) and the 10% Rice Husk Ash (RHF) sample (1698 kg/m³). Furthermore, the 6% SD sample demonstrated enhanced Unconfined Compressive Strength (UCS) of 320 kPa, as opposed to the control's 121 kPa. Triaxial shear strength followed a similar pattern, peaking at 41 kPa for the 6% SD sample. The California Bearing Ratio (CBR), the 6% SD sample showcased significant improvements, achieving 41% for Unsoaked CBR and 36% for Soaked CBR. These results outperformed the control (25%) and the 4% RHF sample (37%). Additionally, the hydraulic conductivity of the 6% SD sample was notably lower at 4.98 ×10–8 cm/s compared to the control (3.35 ×10–8 cm/s) and the 4% RHF sample (4.58 ×10–8 cm/s). The Coefficient of Volume Change (Mv) further supported the superior performance of the 6% SD sample with a value of 0.6, indicating reduced settlement potential compared to the 4% RHF sample (Mv: 0.7). Based on the results, the 6% Sawdust (SD) additive consistently demonstrated the most favourable engineering properties for the expansive clay soil. hence, it is recommended that the 6% SD sample be considered as an optimal choice for enhancing subgrade material, leading to improved performance and sustainability in highway construction.

Study of Residual Soil Permeability Coefficient Post Addition of Coal Fly Ash

Residual soil is soil that is often used as barrier cover soil at the closure of B3 waste storage facilities. This is because the shear strength of the soil is quite good. The minimum value of the soil permeability coefficient (k) for barrier hoods at the closure of B3 waste storage facilities is 10-7 cm/sec. Many residual soils have a soil permeability coefficient (k) of less than 10-7 cm/sec. Because the dominant compound in coal fly ash is silica, mixing this fly ash with residual soil can reduce the value of the soil permeability coefficient (k) and is also expected to increase the shear strength value of the soil. In this study, residual soil samples were mixed with fly ash at 5%, 10%, 15%, 25% and 35% of the dry weight of the soil. This research aims to determine the effect of adding fly ash on the parameters of dry density, shear strength and soil permeability. The tests carried out were standard proctor testing, direct shear test, and Falling-Head permeability testing. The residual soil used in this research came from Hamlet I, Bintang Meriah Village, Pancur Batu District, Deli Serdang Regency. Based on standard proctor testing, the maximum density (gd max) of original soil is 1,410 gr/cm3. The largest maximum density (gd max) was obtained when adding 15% fly ash, namely 1.471 gr/cm3. In the direct shear test, the original soil cohesion value was 0.024 kg/cm² with an internal shear angle of 37.96º. In the variation of adding 15% fly ash, the cohesion value was 0.131 kg/cm² with an internal friction angle of 53.08º. Based on the Falling-Head permeability test, the original soil permeability coefficient value was 1.98 x 10-6 cm/s. The permeability coefficient value for variations in adding 15% fly ash was obtained at 8.02 x 10-8 cm/s.

Fractal Analysis on the Crushing Characteristics of Soil-Soft Rock Mixtures under Compaction

Soil-rock mixtures (SRM) are extensively utilized as filling materials in engineering slopes and roadbeds. A comprehensive understanding of the crushing characteristics of SRM during compaction is essential for precisely controlling its mechanical properties, particularly when dealing with SRM comprising soft rock blocks. This study conducted heavy compaction and screening tests to investigate the crushing and compaction behaviors of soil-soft rock mixture (SSRM) with varying coarse particle content (P5 content), the primary focus was primarily on analyzing the double fractal characteristics of coarse and fine particles. The research findings are as follows: with the increase of P5 content, the maximum dry density of SSRM initially rises and then declines, reaching its peak when P5 content is 70%. Soft rock blocks in SSRM exhibit extreme fragility during compaction, the crushing index of coarse particles exhibits a linear increase with the rise in P5 content, whereas the crushing index of fine particles displays a “double peak” characteristic. After compaction, a linear positive correlation is observed between the fractal dimension and the crushing index of coarse and fine particles. With the increase in P5 content, the slope of the relationship curve between the fractal dimension and the crushing index of coarse particles remains relatively constant, while the intercept gradually decreases. Moreover, the fractal dimension of fine particles effectively reflects the compaction characteristics of SSRM, and the relationship between the fractal dimension of fine particles and dry density aligns with the compaction curve of SSRM.

Experimental Investigation into Lightweight High Strength Concrete with Shale and Clay Ceramsite for Offshore Structures

To develop lightweight high-strength concrete (LWHSC) for offshore structures in a harsh seawater environment, LWHSC with shale and clay ceramsites was designed. LWHSC was experimentally investigated in terms of density, compressive strength, and durability in a coastal environment. Then, its feasibility for offshore structures was also assessed. The results show that the compressive strength and oven dry density of LWHSC appropriately improve with increases in cement content, while they are reduced by the replacement of shale ceramsite with clay ceramsite. The compressive strength of LWHSC also increases first and then decreases with an increase in the pre-wetting of shale and clay ceramsites. Their optional pre-wetting time is about 0.5 h. LWHSC exhibits a higher brittleness compared with conventional concrete. LWHSC has increases in the resistances of freeze–thaw, carbonization, water penetration, and chloride penetration when the shale and clay ceramsite light aggregates decrease in the concrete. The LWHSC prepared in this paper is suitable for the harsh seawater environment of offshore oil platforms but is limited to the southern region where there is no requirement for the freeze–thaw resistance of concrete. The results of this study can provide some reference for the application of LWHSC in offshore structures and other similar aspects of engineering.