Compressive Strength Research Articles

Research on strength characteristics and mechanism of cement stabilized phosphogypsum materials under dry and wet cycles

Phosphogypsum can be used for mine filling, ecological restoration materials, road construction materials, soil conditioning agent, cement retarder, etc., the comprehensive utilization rate of only about 40%, less than 10% for road construction materials, for the huge demand for raw materials road projects, obviously a drop in the bucket. In order to solve the accumulation problem of phosphogypsum, this paper closely combines the major needs of national highway construction, actively responds to the call of Guizhou Provincial People’s Government and Guiyang Municipal People’s Government on the comprehensive utilization of phosphogypsum resources, and researches the strength decay law of cement-stabilized phosphogypsum materials under dry–wet cycle, considering the complex climatic characteristics of dry–wet cycle with the prerequisite of high phosphogypsum mixing, and reveals the mechanism of strength decay, and establishes a strength regression model, and discusses the suitability as pavement base (sub-base) materials. The strength regression model was established, and the suitability of cement stabilized phosphogypsum as the base layer (sub-base layer) of pavement was discussed. The results show that the unconfined compressive strength of cement-stabilized phosphogypsum material decreases with the increase of the number of dry and wet cycles, and the decay is faster in the first four dry and wet cycles, and then gradually tends to level off. The unconfined compressive strength and the number of wet and dry cycles can be fitted with a negative exponential function, and the fitting parameters are all greater than 0.98 . Cement dosage had the most significant effect on unconfined compressive strength with F-value = 988.407, followed by the number of wet and dry cycles and compaction had the least effect. The maximum values of RMSE and MAE were 0.0862 and 0.0776 for the multifactorial regression equation of the unconfined compressive strength of cement-stabilized phosphogypsum materials, which indicated that the regression model had a high reliability. Through the research in this paper, cement stabilized phosphogypsum materials can be used as the base layer (sub-base layer) for highway pavements of various grades under different cement mixing amounts and different traffic volume conditions.

A posteriori constrained bio-inspired algorithm for enhancing strength and resilient modulus of soft subgrade soil

In this study, a hybridised bi-objective optimisation technique was proposed to optimise process parameters (additives) in pavement engineering. The two process parameters, rice husk ash (RHA) and quarry dust (QD), which were used for the treatment of the soft subgrade soil, were set as input parameters in the development of two regression functions with the RSM optimisation technique. Next, the developed regression functions were utilised as fitness functions in the MOGOA and Pareto optimal solutions that represent different optimum combinations of additives. Subsequently, a selected optimum combination of additives (14.5% RHA and 14.4% QD) was used to validate the proposed hybridised RSM-MOGOA technique. The predicted values by the RSM-MOGOA technique for the 28-day unconfined compressive strength (UCS) and the California bearing ratio (CBR) of the soft subgrade were 729.9 kN/m2 and 50.4%, respectively while those obtained from confirmatory experiment were 736.50 kN/m2 and 54.4%, respectively for the UCS and CBR.

Enhancing mechanical properties of low plasticity soil through coal and silica fume stabilization

Low-plasticity soils, characterized by low plasticity and high sand content, present challenges in engineering projects due to their inadequate strength and stability. This study evaluates the comparative effects of coal waste and silica fume as stabilizers to improve the mechanical properties of silty soils. Key parameters such as liquid limit (LL), plastic limit (PL), plasticity index (PI), maximum dry density (MDD), unconfined compressive strength (UCS), and shear strength were assessed through laboratory experiments with varying stabilizer proportions (3–12%). Results showed that silica fume increased the LL of Tarnol soil by 36% and reduced its PI, while coal waste improved the LL of Chaklala soil by 48%, also reducing its PI. Both stabilizers decreased MDD and increased optimum moisture content (OMC). Notably, UCS increased by 77% in Tarnol soil with 12% silica fume and by 83% in Chaklala soil with 12% coal waste after 28 days of curing. Coal waste improved the cohesion of Chaklala soil by a factor of 1.29 and its internal friction angle by 1.04, while silica fume enhanced Tarnol soil cohesion by 1.35 and its internal friction angle by 1.032. These findings demonstrate the potential of coal waste and silica fume as cost-effective, sustainable stabilizers for improving the geotechnical performance of low-plasticity soils. The study contributes valuable insights into using industrial by-products for soil stabilization, offering practical applications for enhancing soil strength and stability in construction and infrastructure projects.

Compressive strength prediction for sandcrete blocks with metakaolin: experiment and multiple linear regression analysis

This paper investigates the effects of the partial replacement of cement with metakaolin (MK) on the strength of hollow sandcrete blocks. Hollow sandcrete blocks of size 150 mm × 225 mm × 450 mm were produced using a mix of ratio 1:6 (binder: sand) and cured for 7, 28, 45, and 60 days. For the actual test, the cement was partially replaced with 0–20% metakaolin at 2.5% intervals. Four (4) multiple linear regression (MLR) models were developed for the 7, 28, 45, and 60 days compressive strength of the produced sandcrete blocks. For verification of the MLR models, compressive strength tests were also carried out on samples produced with 4% and 16% metakaolin replacements. Results show that sandcrete block samples produced using 2.5 and 5% metakaolin replacements possess 28 days compressive strengths that are adequate for load-bearing walls in buildings not higher than three (3) storeys, while metakaolin replacements up to 12.5% are acceptable for non-load-bearing purposes. For the MLR models, the coefficient of determination (R2), Root Mean Square Error, Normalized Root Mean Square Error (NRMSE), and absolute prediction error were employed as model evaluation metrics. Although all four (4) MLR models investigated yielded good results, Model M4 has the highest performance (in terms of its maximum R2 value of 0.9907 and least NRMSE of 1.8168%) for the considered 0–20% MK replacement test samples. Model M4 also has the highest prediction accuracies for the compressive strengths of the 4 and 16% MK replacements verification test data. The best MLR model obtained in this study has great potential in predicting the strength of sandcrete blocks with MK replacement, thus reducing the need for multiple laboratory experiments and their associated costs. This study also buttresses the prospect of sustainable construction using waste.

Enhancing 3D printing with composite filaments incorporating electronic waste: a study on flexural and compression strength

Enhancing 3D printing with composite filaments incorporating electronic waste: a study on flexural and compression strength

The Effect of Al2(SO4)3 on Compressive Strength in SLU Based on Ternary Binder System.

The early flexural and compressive strengths of fast setting SLU formulations based on a ternary system can be severely affected by the selection of accelerator, its quantity and chemistry. Besides design complexity, it is predicted that the current lithium resources will not be sufficient to meet the increasing demands from other markets and lithium prices are expected to increase. It is necessary to search for a new raw material that gives the same performance to prevent the possibility of a supply shortage in the construction sector. In this study, ternary system accelerated with aluminum sulphate was comprehensively investigated in comparison with commonly used accelerators. Aim to achieve is to provide early strength by using aluminum sulphate in the OPC-rich SLU formulation based on the ternary systems instead of traditional accelerators while obtaining cost saving solutions. For this purpose, fresh mortar properties and strength test were carried out according to EN 13813 and results were verified by monitoring hydration reactions over time by XRD and FTIR.

Research on the performance of MXMCCC materials for gas leakage sealing

To address the issues of poor strength and low efficiency in traditional clay-cement composite gas-sealing materials (CCC), a method was proposed to prepare a new type of sealing material by utilizing multi-walled carbon nanotubes (MWCNTs) along with xanthan gum (XG) and magnesium oxide (MgO) to modify CCC. Through controlled experiments of water extraction rate testing, the optimal water-to-solid ratio for the multi-component system material has been determined to be 0.6. Mechanical performance testing reveals that when 1.5% xanthan gum, 5% magnesium oxide, and 1.39% multi-walled carbon nanotubes are added, the compressive strength of the multi-walled carbon nanotube-xanthan gum-magnesium oxide-clay-cement composite (MXM-CCC) reaches 18.60 MPa, with a flexural strength of 3.89 MPa. Pore integration analysis reveals that MXM-CCC has a porosity of 17.29%, with pore sizes ranging from 2.00 nm to 50 nm accounting for 71.46% of the total. The proportion of larger pores has decreased, resulting in a more optimal distribution of pore sizes. The formation mechanism and sealing mechanism of MXM-CCC were explored using characterization techniques such as XRD, FTIR, SEM, and thermogravimetric analysis. The hydroxyl and carboxyl groups in konjac gum undergo chelation with Ca²⁺ in CCC, forming a chelate structure. This causes the hydration products of the clay and cement to adhere together, improving the pore structure and mechanical properties of MXM-CCC. The addition of multi-walled carbon nanotubes accelerates the hydration reaction, increasing the content of substances such as C-(A)-S-H gel, ettringite, and Mg(OH)2 in the MXM-CCC. These chemicals act as a framework, providing support within the pores and inhibiting the shrinkage of MXM-CCC, and improving the adhesion between various hydration products. Additionally, multi-walled carbon nanotubes perform a nano-filling role, filling the pores and improving the density of the multi-component material, thereby enhancing its mechanical properties.

Machine learning-based hybrid regularization techniques for predicting unconfined compressive strength of soil reinforced with multiple additives

Machine learning-based hybrid regularization techniques for predicting unconfined compressive strength of soil reinforced with multiple additives

A comparative assessment of geotechnical performance, cost and carbon footprint of expansive soil treated with cement, lime and fly ash

ABSTRACT Chemical stabilisation enhances strength and reduces the swell characteristic of expansive soils, and cement, lime and fly ash (FA) have been used as stabilisers. Currently, there is a scarcity of studies addressing the mix optimisation of expansive soil stabilised with cement, lime, and FA, considering factors such as strength, swell characteristics, cost, and emissions. Thus, the objective of this research is to develop an optimal mix for stabilising expansive soil using cement, lime, and FA, based on these parameters. The samples were stabilised with 2%–12% cement, 1%–6% lime and 5%–30% FA, and testing including unconfined compressive strength (UCS), swell pressure and California bearing ratio (CBR) were conducted. Utility analysis was undertaken by using Multi-Attribute Utility Theory (MAUT) incorporating UCS, cost/UCS, swell pressure, swell percent, and emissions as key parameters. The findings revealed that UCS of the cement stabilised samples increases with the cement content, while the optimum lime and FA contents based on UCS were 3% and 15% respectively. The swell pressure values of cement, lime and FA stabilised soils reduced by 11.6%–35.9%, 11.6%–22.8% and 45.0%–65.6%, respectively. Overall utility analysis revealed that 15% FA stabilised mix is the optimum mix in terms of strength, swell, cost, and emission.

Graphene oxide and in-situ carbon reinforced hydroxyapatite scaffolds via ultraviolet-curing 3D printing technology with high osteoinductivity for bone regeneration

Ultraviolet photopolymerization additive manufacturing has been used to fabricate calcium phosphate (Ca-P) ceramic scaffolds for repairing bone defects, but it is still a challenge for 3D printed Ca-P scaffolds to simultaneously enhance the mechanical strength and osteoinductivity. Here, we successfully developed a high-performance hydroxyapatite (HA) scaffold containingin-situcarbon and graphene oxide (GO) by precisely regulating the degreasing and sintering atmosphere. The results indicated that the mechanical properties of HA scaffolds could be significantly improved by regulating the amount ofin-situcarbon. The HA scaffold containing 0.27 wt.% carbon achieved the maximum compressive strength of 12.5 MPa with a porosity of approximately 70%. The RNA transcriptome sequencing analysis revealed thatin-situcarbon could promote osteogenic differentiation by improving oxygen transport and promoting the expression of multiple angiogenic factors. More importantly, in the absence of osteoinductive agents, thein-situcarbon and GO synergistically promoted more effective bone mineralization, demonstrating enhanced osteoinductivityin vitro.In a rodent model, the bioceramic scaffolds also exhibited improved osteogenesis in critical bone defects. Therefore,in-situcarbon and GO could simultaneously enhance the mechanical strength and osteoinductivity of HA scaffolds, effectively achieving substantial endogenous bone regeneration. This strategy will provide a simple and energy-efficient approach for engineering osteoinductive ceramic scaffolds for repairing bone defects.

Optimizing the compressive strength prediction of geopolymer lime mortars using the PCA-ELM artificial intelligence model

Abstract This study proposes the use of geopolymer lime mortar, activated with NaOH and Na2SiO3 alkalis, and made from lime, fly ash, brick aggregate, and blast furnace slag (BFS), as an alternative to Portland cement-based concrete. The geopolymer lime mortar samples used in the experimental analysis were produced under controlled laboratory conditions. Compressive strength tests were conducted on the produced samples. The sample with the highest BFS content yielded the best compressive strength results. However, experimental studies are time-intensive. To shorten the experimental time and minimize the material and equipment costs associated with the experiments, a hybrid regression algorithm was proposed for the prediction of compressive strength. Instead of labratory tests the compressive strength of the produced samples was determined using a hybrid regression algorithm has never been used before for this purpose in the literature. This hybrid algorithm is the principal components analysis extreme learning machine algorithm obtained by integrating the PCA method, an effective feature selection method in machine learning, and the ELM method, a regression method that has increased its popularity in recent years. The performance of the proposed algorithm has been compared with other neural network models such as Artificial Neural Network and ELM algorithms and also compared with frequently used algorithms such as random forest regressor, ada boosting, gradient boosting, and extreme gradient boosting algorithms. The results obtained demonstrated the ability of the proposed PCA-ELM algorithm to capture complex relationships within the data by exhibiting superior performance compared to commonly used methods in compressive strength estimation of geopolymer lime mortar.

Characterization, mechanical strength, rheological properties and life cycle assessment of fully recycled concrete through geopolymer technology

This study presents a sustainable method for recycling Ordinary Portland cement concrete (OPCC) using geopolymer technology, reducing the need for new cement and aggregates. By including geopolymerization, the process offers significant ecological and economic advantages over conventional methods. Crushed and pulverized waste concrete was used as recycled granulate (RA) and binder, using recycled clay brick powder (RBP) as an additive. Based on the results, the incorporation of RA into recycled geopolymer concrete (GRC) improved the compressive strength by 11.7%, with a maximum compressive strength of 44.3 MPa and a tensile strength of 4.77 MPa. Replacing recycled concrete powder (RCP) with 5% wt% resulted in a 21% reduction in compressive strength (35 MPa) and a 25.3% reduction in tensile strength (3.56 MPa). A further increase in the RBP content to 15 wt% reduced the compressive strength to 27.65 MPa (37.5% reduction). The RBP content directly effects on the flowability and improves the appearance of the GRC and reduces cracks. When comparing total eco-cost, GRC (128.9 €/m3) proved to be more environmentally friendly than OPCC (140.4 €/m3). The developed GRC meets construction standards and offers a promising alternative to conventional recycling and exceeds OPCC in terms of eco-cost and sustainability.

Optimization of durability characteristics of engineered cementitious composites combined with titanium dioxide as a nanomaterial applying RSM modelling

Currently, chemical attacks, including acid attacks and sulphate attacks, pose a significant problem for the long-term durability of concrete infrastructures that encounter many types of water, including swamp water, marine water, sewage water, drinkable water, and groundwater. Therefore, the intention of this work is to enhance the durability and resistance of concrete against chemical attack by blending titanium dioxide (TiO2) as nanoparticles into designed cementitious composites. The purpose of current study is to obtain an appropriate TiO2 based on the cement’s weight and polyvinyl alcohol (PVA) fiber in composites using multi-objective optimisation. Thirteen mixtures comprising diverse combinations of variables (TiO2: 1–2%, PVA: 1–2%) were formulated utilising RSM modelling. Seven responses were assessed for these mixtures, including weight loss, compressive strength, expansion, a rapid chloride permeability test (RCPT) and a pH test. Analysis of variance, on the other hand, was utilised to construct and assess eight response models (one linear and six quadratics in nature). The R2 values for models spanning from 88 to 99%. The multi-objective optimisation generated optimal response values and ideal variable values (1% PVA and 1.5% TiO2). Experimental verification revealed that the predicted values correlated exceedingly well with the experimental data, with an error rate of less than 5%. The outcomes indicate that a 30% rise in compressive strength was noted when 1.5% TiO2 nanomaterial was incorporated into ECC. Furthermore, the expansion caused by sulphate attack decreases when TiO2 used as a nanomaterial increases in composites. Besides, when the concentration of TiO2 in ECC increased, the pH value, and weight loss caused by acid attack reduced. In addition, the RCPT is recorded reducing when the content of TiO2 increases but it increases with addition of PVA fiber. It has been shown that including 1.5% TiO2 and 1% PVA fiber yields the optimal results for the building sector.

Effect of modified steel slag on properties of rigid polyurethane foam

Abstract The resource utilization of steel slag (SS) represents a critical strategy for integrating environmental protection with sustainable industrial development. In this study, SS was employed as an inorganic filler to investigate the effects of SS particle size and proportion on rigid polyurethane foam (RPUF). Optimal RPUF/SS composites were achieved with an 800-mesh particle size and a 50 % addition ratio. Additionally, the impact of modified SS on the performance of RPUF was examined. The findings indicated a 17.2 % enhancement in thermal insulation properties and a substantial improvement in flame retardancy, evidenced by a 5.7-fold increase in char yield. Despite a reduction in compressive strength, the practical applicability of the composites was not compromised. The performance of the composites was found to be independent of the specific surface area of SS but was significantly influenced by the type of modifier employed (phosphoric acid, formic acid, and silane coupling agents KH550, KH560, KH570). The modification of SS with appropriate agents is essential for enhancing the performance of RPUF/SS composites and for realizing high-value resource utilization of SS in the polyurethane industry.

Internally welded steel bars enhance the bonding between steel pipes and concrete and prevent disengagement and debonding

In this work, the bonding properties of steel pipes and concrete enhanced by internally welded steel bars are investigated, and a method to prevent debonding is proposed. A series of experiments and ultrasonic tests revealed that the internal welding of steel bars effectively improved the bond strength of the interface between the steel pipe and the concrete. A Q420qD steel pipe and C60 self-compacting compensating concrete were used in the experiment, and the filling was uniformly ensured by pumping and vacuum-assisted perfusion. The experimental results show that the concrete-filled steel tube structure has good compactness and stability, but the local voiding phenomenon indicates that the material may have voids or defects. The performance of HPB300 grade steel bars under dynamic loading is also evaluated through cube compressive strength tests and rollout tests. The tests revealed that with an increasing number of internally welded steel rings, the push-out length decreases, indicating better bonding performance. In addition, the finite element simulation and the comparison of experimental data further reveal the bond-slip characteristics of the internally welded reinforcement components of different internal forms of concrete-filled steel tubes, which provides not only important data support for the optimal design and dynamic calculation of concrete-filled steel tube structures but also a reference for subsequent material repair and reinforcement work.

Biomechanical Evaluation of a Novel Non-Engaging Abutment and Screw in Internal Implant Systems: Comparative Fatigue and Load Testing

Dental implants rely on precise prosthetic design and biomechanical stability to ensure long-term success. This study evaluates the mechanical performance of non-engaging abutments in multi-unit combined screw- and cement-retained prostheses (CSCRP) using two internal implant systems: the BlueDiamond (BD) and AnyOne (AO) systems. Unlike conventional implant systems that utilize the same type of screw for both engaging and non-engaging abutments, the BD system employs a distinct screw design for non-engaging abutments. A total of 80 implants were tested, with 40 in each group. Mechanical testing included static compressive load and fatigue tests following ISO 14801 standards. The BD system demonstrated significantly higher compressive strength (326.32 kgf vs. 231.82 kgf, p < 0.001) and 23.4% greater fatigue strength compared to the AO system. Precision fit analysis confirmed no significant deformation, microcracks, or fractures after 5 million loading cycles. These findings suggest that the BD system’s unique screw design for non-engaging abutments contributes to improved mechanical performance and durability. Further clinical studies are needed to assess the long-term implications of this design on prosthetic stability and implant longevity.

Study and Simulation Analysis of Microwave Heating Performance of Magnetite Concrete Based on Random Aggregate Modeling

Radiation-shielding concrete, widely used in protective structures because of its effective shielding properties, employs magnetite aggregates to achieve higher compressive strength than conventional concrete. However, prolonged exposure to high temperatures leads to mechanical degradation. This study investigates the thermal evolution of magnetite concrete under microwave heating across varying temperatures (38–800 °C). A microwave oven was utilized for heating, and COMSOL Multiphysics was employed to establish an electromagnetic-thermal-mechanical coupled model, analyzing surface characteristics, temperature distribution, stress-strain behavior, and residual compressive strength. Results indicate that internal temperatures exceed surface temperatures during microwave heating, with a maximum temperature difference surpassing 150 °C at 800 °C. Compressive stresses predominantly arise in the mortar, while tensile stresses concentrate in aggregates and the interface transition zone, causing stress concentration. Mortar exhibits greater deformation than aggregates as temperatures increase. Simulated and experimental residual compressive strengths show strong agreement, with a maximum deviation of 7.58%. The most rapid mechanical deterioration occurs at 450–600 °C, marked by a residual compressive strength decline of 0.07 MPa/°C and the formation of penetrating cracks.

Machine learning based prediction of compressive strength in roller compacted concrete: a comparative study with PDP analysis

Machine learning based prediction of compressive strength in roller compacted concrete: a comparative study with PDP analysis

Enhancing the water resistance and dimensional stability of wood through microwave treatment and impregnation with oxidised paraffin emulsion

ABSTRACT Wood is a high-performance renewable material, but its hydrophilicity seriously affects its durability and economic value. To address these issues, a new method to enhance the water resistance of wood by impregnating microwave-treated wood with the oxidised paraffin emulsion is proposed. This study investigated the effects of the pre-microwave moisture content of wood and the surfactant content in the oxidised paraffin emulsion on the weight percent gain, penetration degree, contact angle, water absorption, as well as the dimensional stability and mechanical property of the treated wood. After modification, the hydrophobicity and dimensional stability of the wood were improved, with the maximum initial contact angle of the impregnated specimens reaching 135°, and the anti-swelling efficiency for 360 h being 17%. The lowest water absorption of the impregnated specimens at 960 h was achieved at a pre-microwave moisture content of 15% and a surfactant content of 60%, resulting in a reduction of 55% compared to the control. In addition, the impregnation treatment had little effect on the compressive strength parallel to the grain of the wood. This study provided a new theoretical basis for waterproof protection of wood.

Different machine learning approaches to predict the compressive strength of composite cement concrete

Different machine learning approaches to predict the compressive strength of composite cement concrete