28-day Compressive Strength Research Articles

A prospective approach for enhancing the performance of carbon-mixed concrete via retarder incorporation

The concrete that absorbs carbon dioxide during the mixing process, termed as carbon-mixed concrete, has become a hot research topic under the background of dual carbon goals. However, the workability of concrete significantly decreases even with the absorption of a minimal amount of carbon dioxide, indicating a potential challenge in its practical application. Therefore, this study investigated the effects of incorporating 0.5%, 1.0%, and 2.0% carbon dioxide (relative to the mass of cementitious materials) and retarder on the mechanical properties and microstructure of concrete through mercury intrusion, X-ray diffraction, and scanning electron microscopy, revealing the mechanism of retarder improving carbon-mixed concrete. The results indicated that the flowability and 28-day compressive strength of concrete mixed with 0.5% carbon dioxide decreased by 68.75% and 10.77%, respectively. However, after adding 0.25% retarder, these values for the carbon-mixed concrete only decreased by 18.75% and 3.52%. Meanwhile, the introduction of carbon dioxide can form carbonates and carboaluminates and refine the internal pores of the concrete matrix. This study proposes an effective method to improve the performance of carbon-mixed concrete, which can promote the efficient absorption of carbon dioxide in the concrete industry.

Investigation of anionic group characteristics of PCEs on the behaviour of fly ash cementitious systems

The compatibility of polycarboxylate-based water-reducing admixtures (PCEs) having different carboxylate, phosphate and sulfonate anionic groups with paste and mortar mixtures containing fly ash (FA) was investigated. It was found that, with an increase in the FA content of the mixtures, the PCE requirement for the target flow decreased and the consistency retention performance was improved due to the decrease in the amount of hydrated cement. An improvement in rheological parameters was observed with an increase in FA content from 15% to 30%. However, increasing the FA replacement level beyond 30% caused stability problems in the mixtures. This problem was eliminated with the addition of PCE. In the paste and mortar mixtures, regardless of the FA substitution ratio, the best performance was obtained with PCEs containing 7% and 5% phosphate and sulfonate, respectively. The most suitable FA replacement ratio in terms of rheological parameters and 28-day compressive strength was 30% and 15%, respectively. It was observed that the PCE anionic group content did not have any significant effect for all FA substitution ratios.

Feasibility study of replacing part of cement by igneous rock powder as cementitious material: based on mortar macroscopic properties and microstructure

To address the increasing demand for cement and promote sustainable development, the utilization of igneous rock powder as a supplementary material to partially replace cement has emerged as an effective strategy. In this study, the fluidity and mechanical properties of the igneous rock powder-cement (IRP-OPC) composite system were investigated, and the hydration product and microstructure of IRP-OPC were analyzed by using TG/DSC, N2 adsorption-desorption curve (BET) and SEM. The experimental findings demonstrate that the performance of the andesite powder-cement composite cementing system (AP-OPC) surpasses that of tuff powder-cement slurry (TP-OPC) and granite powder-cement slurry (GP-OPC). When the dosage of andesite powder (AP) is 5%–15%, the flowability, flexural strength and compressive strength of cement mortar are improved. When the dosage is 10%, the 28-day compressive strength is 48.3 MPa. Under the condition of low content (10%), part of Ca(OH)2 is fully consumed by active SiO2 in AP and reacts to form C-S-H. Hydration products and AP particles with small particle size are filled into the structural gap, which refines the pore structure of cement slurry, and the increase in compactness provides support for the development of strength in the later stage. The use of 5%–15% AP instead of OPC can improve fluidity and meet the strength requirements of P.O 42.5 Portland cement. This substitution not only reduces engineering costs but also enhances resource utilization.

Development of Sustainable Slag-based Geopolymer Concrete Using Different Types of Chemical Admixtures

Geopolymer concrete (GPC) has achieved a wide popularity since innovating it as an alternative to conventional concrete because of its superior mechanical characteristics and durability, in addition to being a green concrete due to its low negative impact on the environment. However, GPC still suffers from the problem of its poor workability which suppresses its spread in construction applications. This study investigated the most effective parameters on the workability of GPC including GGBFS content, water to binder ratio, and dosage of different types of chemical admixtures, Naphthalene-Based Admixture (NPA) and Polycarboxylate-Based Admixture (PCA), using Taguchi approach and Analysis of Variance (ANOVA) analysis considering the compressive strength at the different concrete ages. It was observed that NPA, in the geopolymer concrete, improved the compressive strength compared to PCA. The NPA-based mixes achieved the highest 28-day compressive strength, 69 MPa, with about 27.8% more than the highest 28-day compressive strength achieved by the PCA-based mixes, 54 MPa. The obtained results revealed that the NPA has achieved the best improvement for both the workability, in terms of initial slump value and slump loss rate, and the compressive strength of GPC mixes compared to PCA.

Properties of road subbase materials manufactured with geopolymer solidified waste drilling mud

In this study, geopolymer was adopted as an eco-friendly binding material to solidify waste drilling mud to fabricate geopolymer solidified waste drilling mud (GSWDM) as a pavement material in the subbase. Using precursor dosage, Na2SiO3 solution dosage, and slag powder (SP) dosage as parameters of mix proportion, the optimal mix proportions of GSWDM were determined through compressive strength tests. Based on a series of tests of unconfined compressive strength, splitting tensile strength, elastic modulus, and compressive resilient modulus, the effects of the SP percentage in the precursor and curing age on the mechanical properties of GSWDM were analyzed. The results indicated that all the mechanical properties of GSWDM were improved with the increasing SP percentage in the precursor. The 28-day unconfined compressive strength, splitting tensile strength, elastic modulus, and compressive resilient modulus of GSWDM were improved by 80.8%, 56.3%, 65.3%, and 76.72%, respectively, when the SP percentage in the precursor increased from 60% to 100%. A nonlinear increase in the mechanical properties of GSWDM was observed as the curing age increased, with a significant increase in the curing age from 7 days to 14 days and a slight increase in the curing age from 14 days to 28 days. Moreover, the microstructure of GSWDM was denser as the curing age and the SP percentage in the precursor grew. The results of this study verified that GSWDM can be used as construction material for road subbase.

Exploring Olive Pit Powder as a Filler for Enhanced Thermal Insulation in Epoxy Mortars to Increase Sustainability in Building Construction

This article explores the use of olive pit powder (OPP) as a promising resource for enhancing the thermal insulation properties of epoxy mortars. A comprehensive analysis of the chemical and physical characteristics of OPP was conducted, employing analytical techniques including scanning electron microscopy (SEM), thermogravimetric analysis and emitted gas analysis (TG-MS-EGA), and proximal analysis. Experimental samples of epoxy grout were prepared by using different proportions of a conventional inorganic filler, quartz powder, and OPP within an epoxy mortar matrix. As the percentage of OPP in the formulation increased, the microstructure of the samples gradually became more porous and less compact. Consequently, there was a decrease in density with the increase in OPP content. The 28-day compressive strength decreased from 46 MPa to 12.8 MPa, respectively, in the samples containing only quartz (Sample E) and only OPP (Sample A) as a filler. Similarly, flexural strength decreased from 35.2 to 5.3 MPa. The thermal conductivity decreased from 0.3 W/mK in Sample E to 0.11 in Sample A. Therefore, increasing the %wt of OPP improved insulating properties while reducing the mechanical resistance values. This study highlights the potential of OPP as an environmentally friendly and thermally efficient filler for epoxy mortars, thereby promoting sustainable construction practices.

Compressive strength prediction of Portland cement clinker using machine learning by XRD data

Accurately predicting the 28-day compressive strength of Portland cement clinkers is challenging due to their complex multiphase nature, especially when production processes and environmental conditions vary. To address this issue, the TransXRD model was introduced, which is a novel deep learning approach that combines the Transformer architecture with CNN design. 214 clinker samples were collected from 6 cement plants. The diffraction peak sequence of samples ranging from 10° to 55° was used as required input for the model. A combination of one-dimensional convolution is incorporated to extract local features, and self-attention mechanisms are leveraged to perform global feature integration. XRD data were directly utilized, bypassing additional processing to minimize signal loss. Compared to other DNN (deep neural network) models, the TransXRD model demonstrates promising performance, achieving a root mean square error (RMSE) of 1.15, a mean squared error (MSE) of 1.33, a mean absolute error (MAE) of 0.93, and a mean absolute percentage error (MAPE) of 1.76 on the test set. Notably, in the training set, 100% of the data exhibit prediction errors within 2 MPa, while within the test set, 90% of the prediction errors are within 2 MPa. The application potential of XRD data in predicting the compressive strength of cement clinker also offers novel insights into predicting the performance of other materials.

Effect of activator concentration on setting time, workability and compressive strength of sustainable concrete with alkali-activated slag binder

The global need to reduce carbon dioxide (CO2) emissions prompted studies on sustainable alternatives to conventional concrete made with ordinary Portland cement (OPC) binders. Alkali-activated ground granulated blast furnace slag (GGBS) is a promising sustainable to OPC in terms of the impact on the environment and reduction of CO2 emissions. Concretes and mortars made with alkali-activated binders demonstrate promising fresh and mechanical properties. This article presents the findings of an experimental study investigating the fresh and mechanical properties of mortar using alkali-activated GGBS binder. The activators used were sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solution with 6 M, 8 M, 10 M, and 12 M molarities. The study assessed their initial setting time, workability, and 28-day compressive strength. The study evaluated the effect of partial replacement of GGBS with 5 % silica fume. The compressive strength was determined after 28 days of curing in three different environments: 1) ambient air temperature, 2) water submersion, and 3) water immersion for 7 days followed by 21 air curing in ambient temperature. The results showed an increase in compressive strength with higher NaOH concentration but a corresponding decrease in initial setting time and flowability. Depending on the curing method, efflorescence, and blue-green pigmentation were seen during the physical assessment of the samples. The highest 28-day compressive strength was 67.5 MPa when the NaOH activator molarity was 10 mol/L which represents an optimum concentration for strength development. Replacing 5 % of the GGBS binder with silica fume resulted in a decrease in the 28-day compressive strength and workability without affecting the initial setting time.

EVALUATION OF EARLY-AGE COMPRESSIVE STRENGTH OF GEOPOLYMER CONCRETE MASONRY UNITS

This paper presents the results of the experimental study on the early-age (1-day) compressive strength of geopolymer concrete masonry units (GCMU). The binder was a combination of ground granulated blast furnace slag (or simply slag) and fly ash with ratios of 3:1 and 1:1. It was activated using an alkaline solution consisting of sodium silicate and sodium hydroxide at a mass ratio of 1.5. Additional water was added to selected mixes to enhance the castability and compactability. The effect of the mix design parameters on the early-age compressive strength of GCMU was investigated. Results showed that an increase in the binder-to-aggregate ratio increased the compressive strength by up to 57%. Similarly, increasing the alkaline solution-to-binder and slag-to-fly ash ratios led to 4 and 3.5 times higher compressive strengths, respectively. Meanwhile, additional water had a negative impact on the compressive strength of GCMU, decreasing it by up to 74%. Still, it was possible to obtain a 1-day compressive strength of 36 MPa for a GCMU having a binder-to-aggregate ratio of 1:5, slag-to-fly ash ratio of 3:1, and solution-to-binder ratio of 0.4. Such results provide evidence of the ability to utilize geopolymer concrete in the field of masonry construction.

EVALUATION OF EARLY-AGE COMPRESSIVE STRENGTH OF GEOPOLYMER CONCRETE MASONRY UNITS

This paper presents the results of the experimental study on the early-age (1-day) compressive strength of geopolymer concrete masonry units (GCMU). The binder was a combination of ground granulated blast furnace slag (or simply slag) and fly ash with ratios of 3:1 and 1:1. It was activated using an alkaline solution consisting of sodium silicate and sodium hydroxide at a mass ratio of 1.5. Additional water was added to selected mixes to enhance the castability and compactability. The effect of the mix design parameters on the early-age compressive strength of GCMU was investigated. Results showed that an increase in the binder-to-aggregate ratio increased the compressive strength by up to 57%. Similarly, increasing the alkaline solution-to-binder and slag-to-fly ash ratios led to 4 and 3.5 times higher compressive strengths, respectively. Meanwhile, additional water had a negative impact on the compressive strength of GCMU, decreasing it by up to 74%. Still, it was possible to obtain a 1-day compressive strength of 36 MPa for a GCMU having a binder-to-aggregate ratio of 1:5, slag-to-fly ash ratio of 3:1, and solution-to-binder ratio of 0.4. Such results provide evidence of the ability to utilize geopolymer concrete in the field of masonry construction.

Potential use of silane-modified oyster shell powder in hydrophobic concrete

This article describes the laboratory-scale manufacture of hydrophobically modified oyster shell powder (mOSP) via a silane coupling agent and used as cement substitutes at 0% to 2.5%. Hydrophobic chemicals have been used in concrete to minimise capillary action by researchers. Although hydrophobic fillers improve concrete’s water repellency, replacing fine particles with them in higher proportions has a negative effect. We can use hydrophobically modified fillers in smaller amounts to replace cement while maintaining its critical properties. When mOSP is added in various quantities to binary and ternary mixes with natural zeolite, concrete hydration, mechanical strength, and durability are examined. At a 1.5% replacement ratio, mOSP improved concrete characteristics and durability. With free water and the hydrophobic modified nOSP, concrete mixes were consistently more workable. A gliding effect on the cementitious matrix caused by the surface roughness and hydrophobicity of the developed silane-coated nOSP increases the slump value. The 28-day compressive strength of concrete containing modified nOSP ranged from 39 to 42 MPa without zeolite and 43 to 46 MPa with it. Compressive strength increased more when 10% natural zeolite (NZ) was added with different amounts of mOSP. The RCPT values of the concrete series without zeolite dropped until 1% mOSP replacement (mOSCII), while the 1.5% mix (mOSZIII) had the lowest value. The angularly modified nOSP aggregates interlocked, improving the migration coefficient of mOSP concrete.

Preparation and microstructure analysis of alkali-activated ground granulated blast furnace slag-steel slag grouting materials

To solve the problems of large storage requirements for iron and steel solid waste piles, environmental pollution, and low utilization, an alkali-activated ground granulated blast furnace slag (GGBFS)-steel slag (SS) grouting material (AAGM) was prepared, quicklime was used as an additive, and the activity of SS and GGBFS was activated by NaOH and water glass. Through a full factor analysis test, the effects of alkali content (AC), GGBFS/SS, and quicklime content (QC) on the fluidity, initial setting time (IST), and final setting time (FST) of AAGM were investigated. The strength formation mechanism of AAGM was analyzed using mechanical property testing, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). These studies showed that the fluidity of the slurry decreased with increasing QC, AC, and GGBFS/SS, and the IST and FST of the slurry continuously shorten with increasing QC, increasing AC, and decreasing GGBFS/SS. The 28-day unconfined compressive strength (UCS) of AAGM decreased with decreasing QC and increasing AC, and first increased and then decreased with increasing GGBFS/SS. As the age increased, the hydration reaction inside the specimen was sufficient and the compactness was stronger, reducing the porosity inside the specimen; the hydration products inside AAGM were mainly plate-like crystals (anhydrite, calcite), a small amount of columnar crystals (ettringite), and a large amount of gel-like substances (C-S-H/C-A-S-H) attached to its surface. When the GGBFS/SS ratio was 1:1.3, the QC was 3 %, the AC was 13 %, the water glass modulus was 1.6, and the water/cement ratio was 0.6; additionally, the fluidity, IST, FST, and 28-day UCS of AAGM were 137 mm, 255 min, 280 min, and 27.07 MPa, respectively, which can meet various performance indicators required for engineering grouting.

Mechanical properties and microscopic characterization of coal-based synthetic natural gas slag as supplementary cementitious materials

This study investigated the feasibility of using coal-based synthetic natural gas slag (CSNGS) as supplementary cementitious materials in cement-based binders. The effects of different CSNGS/Cement ratios on the slump flow and mechanical strengths of paste and mortar were first analyzed. Subsequently, the mineralogy, morphology, and chemical structure of CSNGS-Cement paste were examined by means of XRD, SEM/EDS, FT-IR, and TG/DTG. The results showed that an appropriate incorporation of CSNGS contributed to the improvement of flowability due to the micro-filling effect. As the CSNGS proportion increased, the compressive strength decreased, while an appropriate amount of CSNGS was conducive to improving the flexural strength of mortar. The 28-day compressive strength of composite mortar reached over 89 % than that of the reference mortar under CSNGS within 0–30 %, possibly due to the increased contents of needle-like ettringite and C-A-S-H. Additionally, a formula considering the effective water absorption rate and pozzolanic activity of CSNGS was developed for predicting the compressive strength of CSNGS-cement mortar, demonstrating a good correlation coefficient (R2 > 0.93) between predicted and measured values. Overall, CSNGS proves to be a feasible supplementary cementitious material, offering a promising way for the effective utilization of CSNGS as well as the clean production of concrete.

Study on the Properties and Hydration Mechanism of Calcium Carbide Residue-Based Low-Carbon Cementitious Materials

Alkali-activated cementitious materials, as an environmentally friendly cementitious material, can effectively reduce carbon emissions and improve the utilisation of solid wastes. However, traditional strong alkali activators have limitations such as high carbon emissions and poor safety. In order to overcome the defects of traditional strong alkaline activators and realise the high value-added use of calcium carbide residue (CCR), this paper adopts CCR as an alkaline activator to activate granulated blast furnace slag (GBFS)-steel slag (SS) cementitious systems for the preparation of alkaline-activated cementitious materials. The effects of CCR content and SS content on the compressive strength and working performance of CCR-GBFS-SS cementitious systems are analysed, along with the hydration process of CCR-GBFS-SS cementitious systems and the mechanism of action through the hydration products, their chemical structure and their microscopic morphology. The research results show that CCR-GBFS-SS cementitious systems have a 28-day compressive strength of 41.5 MPa and they can be controlled by the setting time; however, the flow performance is poor. The SS content can be increased to improve the flow performance; however, this will reduce the compressive strength. In CCR-GBFS-SS cementitious systems, CCR is the main driving force of hydration reactions, GBFS mainly provides active silica and aluminium and the amorphous C-(A)-S-H gel and ettringite formed by the synergistic action of multiple solid wastes are the main sources of compressive strength. With the extension of the curing time, the amount of hydration products in the cementitious systems gradually increases and the matrix of the cementitious systems gradually becomes denser. This study will provide a reference for the consumption of low-value solid waste such as CCR and the preparation of low-carbon cementitious materials from multi-component solid wastes.

ANOVA-guided assessment of waste glass and limestone powder influence on ultra-high-performance concrete properties

Ultra-high-performance concrete (UHPC) possesses remarkable structural and durability characteristics, yet its widespread acceptance is hindered by cost inefficiency and environmental concerns. To address these challenges, this study investigates the impact of waste glass and limestone powder as partial substitutes for silica fume and cement in UHPC. For this, three distinct formulations are studied (Control, Optimized-1, and Optimized-2), representing different dosages of waste glass and limestone powder. The research focuses on six critical properties (compressive strength, modulus of elasticity, ultrasonic pulse velocity, initial surface absorption, density absorption, voids, and chloride ion penetration) evaluated at different ages (1, 7, 28, and 90 days for compressive strength, and 7, 28, and 90 days for the remaining properties). So, a total of 171 test specimens were examined, with 3 samples for each age and formulation. Statistical analysis, using ANOVA, assessed and confirmed the significance of the factors in the experimental results. The findings provide comprehensive insights into the UHPC formulations, highlighting the influence of waste glass and limestone powder on specified properties over varying ages. The research reveals that, despite the optimized blends exhibiting lower compressive strength values, all mixes surpass the 150 MPa threshold for cylindrical samples at the 90-day mark. Moreover, the Control mix consistently outperforms the optimized blends in modulus of elasticity at all ages, meeting ACI 239 criteria. The void content analysis shows encouraging trends, with all formulations displaying voids of less than 5% on the seventh day, improving during the curing process. Notably, Optimized-2 demonstrates superior performance over the Control mix after 90 days. Chloride ion penetration is minimal for all blends after 90 days, confirming the effectiveness of mineral admixtures. ANOVA analysis confirms significant impacts of formulation and age on various UHPC characteristics, emphasizing the consistent reduction in performance with alternative mineral additions. The interaction between formulation and age implies variations in property evolution, suggesting potential convergence with alternative formulations.

Evaluation of coconut shell biochar on recycled aggregate concrete through petrographic studies

Recycled Concrete Aggregate (RCA), derived from discarded concrete, substitutes or stabilizes Natural Concrete Aggregate (NCA) in constructing Recycled Aggregate Concrete (RAC). This study investigates Coconut Shell Biochar (CSB) as a potential mitigator of Alkali-Silica Reaction (ASR) in RAC, particularly in tropical regions like Sri Lanka. CSB, noted for its cost-effectiveness, undergoes assessment for its impact on concrete properties. Petrographic analyses, encompassing optical microscopy and SEM, conducted on CSB-modified RAC in Sri Lanka, reveal favorable mechanical outcomes. Grade 25 RAC, supplemented with CSB, demonstrates 28-day compressive, split-tensile, and flexural strengths of 25.4, 2.5, and 4.1 MPa, respectively. Results indicate CSB effectively alleviates ASR-induced alterations and chemical reactions in RAC, prompting further exploration of CSB's role in controlling specific precipitates and chemical reactions associated with ASR.

Design and Preparation Technology of Green Multiple Solid Waste Cementitious Materials.

For solid waste-based cementitious materials, most scholars focus their research on the hydration reaction of cementitious materials, but there is still a lack of solid waste design that comprehensively considers mechanical properties and durability. Therefore, this article focuses on exploring the mix of design and the microscopic and macroscopic properties of multi solid waste cementitious materials (MSWCMs), namely steel slag (SS), slag powder (SP), desulfurization gypsum (DG), fly ash (FA), and ordinary Portland cement (OPC). According to the orthogonal experimental results, the compressive strength of MSWCMs is optimal when the OPC content is 50% and the SS, SP, DG, and FA contents are 10%, 20%, 5%, and 15%, respectively. The MSWCMs group with an OPC content of 50% and SS, SP, DG, and FA contents of 5%, 15%, 5%, and 25% was selected as the control group. The pure OPC group was used as the blank group, and the optimal MSWCMs ratio group had a 28-day compressive strength of 50.7 megapascals, which was 14% and 7.6% higher than the control group and blank group, respectively. The drying shrinkage rate and resistance to chloride ions were also significantly improved, with maximum increases of 22.9%, 22.6%, and 8.9%, 9.8%, respectively. According to XRD, TG-DTG, and NMR testing, the improvement in macroscopic performance can be attributed to the synergistic effect between various solid wastes. This synergistic effect produces more ettringite (AFt) and C-(A)-S-H gel. This study provides a good theoretical basis for improving the comprehensive performance of MSWCMs and is conducive to reducing the use of cement, with significant economic and environmental benefits.

Performance experiment of ultra high temperature cementing slurry system

Introduction: The escalating pursuit of oil and gas reserves in China has led to increasingly deep and ultra-deep well drilling, encountering extreme temperatures that challenge the heat resistance capabilities of cement slurries. This study addresses the critical need for high-performance cement slurries capable of withstanding ultra-high temperatures during drilling and completion operations.Methods: A novel ultrahigh temperature conventional density (UHTE) cement slurry was formulated by incorporating high-temperature-resistant additives, namely DRF-1S and DRH-2L. An indoor testing framework was established to assess the slurry’s performance across various parameters: Evaluating the slurry’s ability to maintain uniform consistency over time. Measuring the amount of free water separated from the slurry under simulated downhole conditions. Assessing the slurry’s transition from fluid to solid state over time. Determining the compressive strength and other mechanical attributes after curing at elevated temperatures.Results: The experimental findings revealed the following: An optimal silica sand dosage of 50% was found to enhance the overall performance of the UHTE cement slurry. The developed UHTE cement system, fortified with DRF-1S and DRH-2L, demonstrated effective functionality within a temperature range of 180°C to 210°C, representing a significant advancement in high-temperature resistance. The slurry maintained API water loss below 100 mL, ensuring minimal fluid loss during placement. Adjusted thickening time allowed for adequate pumping and placement without premature setting. Settlement stability was maintained below 0.04 g/cm3, indicating excellent homogeneity and stability. Incorporation of the anti-decay material DRB-3S ensured a 28-day compressive strength exceeding 50 MPa at 210°C, signifying robust structural integrity under extreme thermal conditions.Discussion: This research provides a robust foundation for the practical application of UHTE cementing technology in ultra-high temperature environments. The successful development of the UHTE cement slurry system, characterized by its superior temperature resistance, controlled water loss, optimized thickening behavior, and exceptional mechanical properties, paves the way for field trials and further enhancements. Future work will involve testing the effectiveness of the new additive combination under actual downhole conditions and refining the formulation to develop an even more advanced UHTE cementing additive. These advancements will contribute to enhanced wellbore integrity, improved drilling efficiency, and increased safety in deep and ultra-deep oil and gas exploration endeavors in China.

Elucidating the reaction of seashell powder within fly ash cement: A focus on hydration products

The use of shellfish waste as a raw material in cement and concrete production is recognized as a feasible approach. Similar to limestone, seashell powder (SP), which is primarily made up of calcium carbonate, has been identified as a promising supplementary cementitious material (SCM). However, the current understanding of SP's chemical interactions within aluminum-rich cement systems remains limited, often resulting in its classification as simply an inert filler. Therefore, this research seeks to clarify the contribution of SP to fly ash (FA) cement by investigating the hydration products. The investigation reveals that SP facilitated hydration albeit to a lesser extent compared to limestone. In cements incorporating SP, the AFm phases, characterized by carboaluminate formations, became predominant, and the calcium carbonate content diminished over time, indicating reactive engagement of SP. The addition of 5 % SP enhanced the polymerization of the C-(A)-S-H structure in FA cement. Moreover, the substitution of cement with SP elevated the effective water to cement ratio, leading to a reduction in the Ca/Si ratio of C-(A)-S-H, while the Al/Si ratio remained virtually unchanged. Analysis identified the presence of monocarboaluminate (Ca/Al/C atomic ratio of 4: 1.97: 4.39) and hemicarboaluminate (Ca/Al/C atomic ratio of 4: 2.25: 2.40) in FA cements with 5 % and 10 % SP additions, respectively. Nonetheless, incorporating SP negatively impacted the compressive strength of FA cement, underscoring the importance of using SP in moderation. Specifically, the 28-day compressive strengths of FA cements with 5 % and 10 % SP additions measured at 42.9 MPa and 40.2 MPa, respectively. Moreover, SP-FA cement offers significant environmental advantages. This research innovatively elucidates the reaction mechanism of SP within fly ash cement, offering vital insights into SP's impact on the hydration process and advancing the recycling of shellfish waste.

Abrams’ Law Formulation for Blended Cement Paste Incorporated with Ground Ferronickel Slag

Ground ferronickel slag (GFS) is a form of an industrial waste by-product generated during the smelting process of nickel ore that has been crushed and ground into fine powder. GFS is a pozzolanic substance that may be employed as an environmentally beneficial binding agent when blended with Portland cement. This research aims to apply the Abrams Law formulation to blended cement combined with GFS. GFS was utilized as a Portland cement composite (PCC) replacement at varying percentages of 0, 10, 20, 30, 40, and 50 wt.%. The blended cement paste incorporated with GFS was tested at three water to cementitious material ratio (w/cm) levels of 0.4, 0.5, and 0.6. After samples have been made, a compressive strength test is carried out. The research results showed that at 28 days, the optimum amount of GFS was found in the percentage of 20 wt.% induced the compressive strength by 40.41 MPa with a w/cm of 0.4. The equations based on Abrams’ Law have been proposed for estimating the correlation of 28-day compressive strength with w/cm in the range from 0.4 to 0.6. In addition, the hardened densities of binary blended cement paste were investigated. It was found that the density decreased with an increase of w/cm. The proposed equations provide the beneficial interpretation for estimating the compressive strength of blended cement paste based on the w/cm..