Compressive Strength Requirements Research Articles

Optimizing mix design of concrete with manufactured sand for low embodied carbon and desired strength using machine learning

The aim of this paper is to propose a mix design methodology for concrete with manufactured sand (CMS), considering both the desired compressive strength and minimal embodied carbon, utilizing a machine learning approach. Initially, a compressive strength prediction model for CMS is developed using artificial neural network (ANN) based on a dataset containing 1810 measured strengths from real projects. The hold-out validation and 10-fold cross-validation are performed in addition to the validation from literature, indicating the high accuracy, robustness and generalization of the proposed model. Notably, the stone powder content of MS, a variable unique to CMS compared to river sand concrete, is found to have less importance in relation to compressive strength but should still be considered during mix design. Furthermore, the study reveals that the embodied carbon of CMS exhibits an increasing trend with the increase of compressive strength due to the enhanced cement content, while it varies significantly for a fixed compressive strength. However, cement may not be a carbon intensive constituent from the viewpoint of carbon intensity. Finally, mix optimization is achieved using ANN by setting the compressive strength requirement as the constraint condition and minimizing embodied carbon as the optimization objective. This paper not only provides an efficient solution for estimating the compressive strength of CMS without the need for experiments but also highlights the promising optimization capabilities of ANN for low-carbon CMS design.

An investigation of the physic-mechanical properties of the expanded perlite mortars with thermal-activated concrete waste and microencapsulated paraffin

In the transition to zero waste and sustainable development, it becomes essential to use phase change materials and recycled cement in construction projects to improve energy efficiency and encourage sustainable building practices. The primary goal of this study is to determine how the properties of expanded perlite mortars are affected when Portland cement is partially replaced with recycled cement, produced by thermally treating concrete waste at 550 °C. Recycled cement substituted Portland cement in various percentages (10 %, 30 %, and 50 %). Also, microencapsulated phase change material (m-PCM) was incorporated into the mortar in a proportion of 2 wt% and 5 wt%. Cement-based mortars with a 1:3 aggregate volume ratio have been developed for evaluation. The mortars were analyzed in terms of mechanical strength (flexural and compressive), water absorption, thermal properties, differential scanning calorimetry, and microstructure. The experimental results revealed a decrease in mechanical strength values when Portland cement is substituted by recycled cement, regardless of percentage. Recycled cement in proportion of 30 % positively influenced the water absorption. The thermal conductivity of reference mortar was higher than that of 30 % recycled cement. The reference mortar's specific thermal conductivity values were 0.466 W/(m·K) at 25 °C, 0.525 W/(m·K) at 30 °C, and 0.589 W/(m·K) at 35 °C. On the other hand, the mortar containing 30 % recycled cement exhibited much lower heat conductivity throughout these temperatures, suggesting superior insulating qualities. DSC analysis verified that adding m-PCM to the mortars increased their thermal storage capacity, which is essential for raising the energy efficiency of building materials. Nevertheless, the mechanical strength decreased as m-PCM was added. Despite decreases, all mortars satisfied the SR EN 998–1 standard's CS IV classification for interior plaster applications, which is based on compressive strength requirements. Overall, this study shows how using m-PCM and recycled materials can improve the performance of cement-based materials.

Valorization and investigation of volcanic ash as an aggregate building brick component

Abstract The devastating series of Taal volcanic eruptions from 2020 to 2022 covered several locations in the Philippines under a thick layer of ashes, destroying properties and halting business operations. In response, the Biñan City Government in Laguna, Philippines, proposed the development of eco-friendly bricks by leveraging the pervasive amounts of spewed volcanic ash as part of its solid waste management program. The materials recovery facility of the city produced several brick blends of combined Taal volcanic ash, cement mortar, and plastic waste materials. This study investigates the potential of Taal volcanic ash as an aggregate building brick component by measuring the compressive strength of the formulated bricks. With different blends of aggregate components, the bricks were tested for their durability based on the ASTM C67/C67M-20 standard after curing between 15 to 30 days. Per the ASTM C62-17 standard, all brick blends that were cured for 30 days including those with volcanic ash and plastic waste as aggregate components fall under the negligible weathering grade. This indicates that these bricks will be durable in building and structural applications where the average compressive strength requirement for bricks is at least 10.3 MPa. A regression model was also fitted with an adjusted r 2 value of 0.9413 and a p-value of < 2.2 × 10−16 using the experimental data.

Exploring economic and environmental impacts of recycled aggregate concrete using particle swarm optimization algorithm

Recycled aggregate concrete (RAC) is a sustainable alternative that encounters challenges due to varying sources and processing methods. This study introduces a novel approach to optimize the mix proportions of RAC through machine learning and multi-objective optimization techniques. It identifies the key factors influencing the compressive strength of concrete, aiming to minimize costs and environmental impacts while meeting compressive strength requirements. Six machine learning models were developed based on a database of 522 samples to predict the cubic compressive strength of RAC. Among these, the XGBoost model demonstrated the highest accuracy, establishing a functional relationship between cubic compressive strength and mix proportions, achieving an R2 of 0.965 and a composite performance index of 0.081. Additionally, life cycle cost analysis and life cycle assessment were employed to evaluate both cost and environmental impacts. Using the particle swarm optimization algorithm, the optimization of strength, cost, and environmental impact was conducted, comparing RAC with conventional concrete. The significant factors affecting cubic compressive strength were identified as curing age, water-to-cement ratio, and sand content, contributing 28.6%, 20.6%, and 15.8% to the variation in strength, respectively. Cement content and the fly ash-to-cement ratio were found to significantly influence cost and environmental factors, respectively. Optimal reductions in cost and environmental impact were achieved with a recycled aggregate replacement ratio of 45%–60%, resulting in decreases of up to 18.94% and 41.72%, respectively.

Evaluating the sustainability of microwave pre-cured high-volume slag concrete: Mechanical properties, environmental impact and cost-benefit analysis

Microwave pre-curing, a novel method, offers numerous advantages including energy and time efficiency. The mechanical performance and durability of high-volume slag concrete (HVSC) subjected to microwave curing were experimentally investigated in this study. Additionally, the environmental impact and cost-effectiveness of microwave-cured HVSC were studied, and the ecological efficiency and cost efficiency were analyzed in conjunction with compressive strength and durability. Experimental results indicate that microwave curing significantly enhances the early-stage hydration reaction rate of concrete, increasing the yield of hydration products, especially AFm. Consequently, the early-stage porosity decreases, and the early compressive strength and electrical resistivity of the mortar increase significantly. Furthermore, microwave curing significantly improves the early-stage ecological efficiency and cost efficiency of HVSC. Although the ecological efficiency and cost efficiency of later-stage strength decrease slightly, the durability ecological efficiency and cost efficiency have increased by 12.41–24.6 % and 13.79–26.89 %, respectively, compared to the control group. Time-saving analysis indicates that microwave curing can significantly reduce the curing time for samples by quickly enhancing the early mechanical properties of the materials. Specifically, microwave curing can shorten the curing time by 2.09 days when the compressive strength requirement reaches 20 MPa, and by 2.62 days when the requirement is 30 MPa.

Attaining material circularity in recycled construction waste to produce sustainable concrete blocks for residential building applications

Construction waste poses a major environmental problem owing to traditional building methods, resulting in a huge global waste burden that ultimately ends up in landfills. The development of sustainable methods is necessary not only to reduce environmental problems but also to encourage material circularity and promote the effective recycling and reuse of construction waste. Yet, previous research has largely focused on using recycled construction waste as a single or double additive ingredient. However, this study aims to assess the development of sustainable concrete blocks for residential building applications with a novel blend of two or more waste ingredients, with each additive contributing to a specific characteristic. Physical properties (bulk density, porosity, water absorption, thermal conductivity, compressive strength, fire resistance, and mass loss), cost, and CO2 emissions were determined to evaluate the efficiency of the block. Subsequently, the energy savings were assessed using block samples as single-layer building envelopes within a full-scale room simulated using EnergyPlus. The results showed a reduction in density of up to 24.32 %, and thermal conductivity and heat transfer of up to 56.8 % compared to typical blocks, which satisfied the compressive strength requirements of load- and non-load-bearing walls. The sustainability assessment revealed that the developed concrete blocks could significantly lower production costs by up to 31.75 % and reduce carbon emissions by up to 27.15 % compared to typical concrete blocks. It was found that the best single-layer building envelope in a full-scale residential room improved energy efficiency by up to 9.17 % when the produced blocks were used. This enhancement could lower the cost of energy consumption from 88.34 to 80.24 kWh/m2/year. This research contributes to the utilization of circular building blocks, which reduce the need for typical raw materials while improving their functional properties and lowering the production cost, carbon emissions, and energy consumption in a single-layer residential building.

Experimental design, mechanical performance and mechanism analysis of C30 phosphogypsum-based concrete

The present study aimed to increase the utilization of phosphogypsum and reduce cement consumption. Single-factor experiments were designed to the effects of water-cement ratio (0.45–0.30), silica fume (1 %∼7 %), cement dosage (0 %∼20 %), and the RPG/HPG (20/80–0/100) on mechanical properties of phosphogypsum-based concretes (PGBCs). A new phosphogypsum-based concrete was prepared to meet the compressive strength requirement of C30 grade. The maximum 28d compressive strength of this PGBC reached 45.1 MPa. Simultaneously, the effect mechanisms of above four factors on the mechanical properties of PGBCs were discussed by combining XRD and SEM results. Moreover, the volume stability, elastic parameters, and compressive constitutive model of this PGBC with compressive strength above 30 MPa were investigated. This PGBC used more than 80 % phosphogypsum and 10∼20 % cement, exhibiting well economy and environmental friendliness. Moreover, the constitutive model was established to well predict the compressive behavior of PGBC with different RPG/HPG relative ratios. This PGBC had better volume stability and weaker deformation resistance than cement-based concrete. The present results can provide more theoretical and technical supports for the large utilization of PG.

Assessing Roller Compacted Concrete using GGBS as Partial Cement Replacing Material for Application in Low Traffic Volume Road

This paper reports most optimized mix derived from the roller compacted concrete (RCC) using ground granulated blast furnace slag (GGBS) as the partial cement replacing materials in the context of possible utilization of RCC in the construction of rigid pavements in the rural part of the country, especially subjected to low vehicular traffic volume. In the current study, various RCC mix compositions were developed by substituting ground granulated blast furnace slag (GGBS) for ordinary Portland cement (OPC) in varied percentages (0%, 20%, 40%, and 50%) and assessed for mechanical (strength) properties. All the three GGBS blended mix compositions are found to give early age compressive strength more than 20 MPa and 28 days compressive strength more than 30 MPa. Further, they are found to have split tensile strength in the range of 2.8-4.1 MPa. Moreover, they are found to yield the flexural strength more than 3.8 MPa. All the three mixes are found to comply with the requirements of compressive strength, splitting tensile strength and the flexural strengths as prescribed by Indian Roads Congress Specification and American Concrete Institute Standards for possible utilization in the construction of rigid pavements in the rural parts of the developing country like India. Further, the strength values of the GGBS blended mixes increases from 20% to 40% and decreases thereafter, at the higher GGBS contents such as 50%. In view of this, the RCC mix composition with 40% GGBS contents can be regarded as the most optimal mix to be used in the construction of rigid pavements in rural part of the country.

Kajian Kuat Tarik Belah pada Beton Variasi Limbah Granit Sebagai Substitusi Parsial Agregat Kasar

The development of concrete making technology has developed rapidly nowdays, the innovations in terms of material use and workmanship. The implementation of construction work carried out today pays attention to aspects of strength, rigidity, and high durability, as well as sustainability. To support these two things, research can be carried out on making concrete using granite waste. The research method used in this study is an experimental method. The concrete mix design uses variations of granite waste with successive levels of 0%, 15%, 30%, and 45%. The test specimen used for tensile strength testing is cylindrical with a diameter of 15 cm and a height of 30 cm, the test uses 12 specimens where each variation uses 3 specimens. The test is performed when the specimen has reached the age of 28 days. The test specimen tested has met the planned compressive strength requirements at a concrete life of 28 days where the results are greater than 20 MPa. Results of testing the tensile strength of concrete variations of granite waste as a partial substitution of coarse aggregate with variations of granite waste of 0%, 15%, 30%, and 45% respectively; 2.43 MPa; 2.50 MPa; 2.97 MPa; and 2.78 MPa.

Impacts of advanced metals recovery on municipal solid waste incineration bottom ash: aggregate characteristics and performance in portland limestone cement concrete

The optimization of alternative materials in concrete production continues to garner considerable attention in order to meet sustainability goals and supplement natural materials. Portland limestone cement (PLC) and municipal solid waste incineration (MSWI) bottom ash (BA) have been proposed separately as green cement and coarse aggregate supplement in low-strength concrete production, creating sustainable products and alternative disposal scenario for a waste material. This study discusses the impact of advanced ash processing techniques on aggregates and presents the performance of concrete incorporating both of these products with PLC for the first time. Two sources of MSWI BA were investigated, one as-produced (TMR) and one processed with novel advanced metals recovery (AMR). The AMR process reduced total Al content in ash compared to TMR (20,500 vs 17,000 mg/kg), though not aluminum oxide content, as the AMR process targets metallic aluminum. A composition study on both aggregates supports a reduction in ferrous and non-ferrous metals following the AMR process. All control and test mixes met 28-day compressive strength requirements (17 Mpa). Both AMR and TMR MSWI BA-amended concretes yielded compressive strengths below control specimens (no ash) ranging from 17 to 23 MPa, with little to no difference observed dependent on MSWI BA processing. The life-cycle discussion supports benefits deriving from supplementing naturally mined materials and recovering ferrous and nonferrous metals with the AMR process.

Evaluation of Early-Age Compressive Strength in Winter Prefabrication: A Comparative Study

In the field of prefabrication, the timely demolding of concrete elements is crucial to prevent structural failures during panel lifting. This study investigates the early-age compressive strength of different concrete mixtures by simulating various prefabrication plant scenarios. Special attention is given to winter conditions, where concrete hydration tends to be slower, potentially compromising the minimum compressive strength requirement of 10 MPa. The first scenario (reference), set at an ambient temperature of 20 °C with raw materials at room temperature, establishes the baseline for comparison. Two alternative dispositions are explored: Scenario 2, with an external temperature of 8 °C and the water for mixing at 35 °C, and Scenario 3, with the same external temperature but utilizing a heating hood to maintain the concrete at 35 °C. The experimental results shed light on the effectiveness of different strategies in achieving the desired early-age compressive strength under winter conditions. The use of warm mixing water and heating hoods are evaluated as potential measures to counteract the hydration slowdown. The findings contribute valuable insights for optimizing prefabrication processes in cold weather, ensuring the structural integrity of precast concrete elements.

Advancing Sustainable Construction Materials: Wood, Rubber, and Cenospheres Geopolymer Masonry Units Development

As the environmental impact of modern society continues to escalate, the construction industry actively pursues environmentally friendly materials to revolutionize its practices. Recycling, especially repurposing end-of-service materials and industrial wastes, emerges as a pivotal strategy offering a promising path towards sustainable construction. This study focuses on the innovative reuse of end-of-service wood, crumb rubber, and cenosphere with geopolymer binder to produce sustainable alternatives to masonry units. The study was conducted in two stages. In the first stage, cube samples were produced and tested to establish an optimal mix design. Results indicated that as the relative volume of waste increased, the compressive strength decreased. The compressive strength of the wood geopolymer composite decreased from 25 MPa to 4 MPa as the wood-to-binder ratio increased from 0.1 to 0.5. An increasing trend was observed for density with the increase of the rubber-to-wood ratio. The compressive strength also increased with the increase of the rubber-to-wood ratio for most of the investigated ranges. As fly ash is gradually replaced by cenospheres, a significant decrease in compressive strength was noted, about 70% and 80% for wood-to-binder (ratios of 0.2 and 0.3, respectively). In the second stage, three distinct types of masonry units were produced and tested based on the optimized mix design. The compressive strength results indicated promising performance, with wood-geopolymer masonry units exhibiting a strength of 8.39 MPa, wood-rubber-geopolymer masonry units achieving 8.32 MPa, and wood-cenosphere-geopolymer masonry units resulting in 7.33 MPa. While these values fell below the target 10 MPa, it is noteworthy that wood-geopolymer masonry units and wood-rubber-geopolymer masonry units met the minimum compressive strength requirements of some standards and demonstrated significantly better ductility compared to traditional masonry units. The results showcase significant promise in the viability and performance of these innovative masonry units.

Effects of polycarboxylate superplasticizer and hydroxypropyl methylcellulose on the properties of ferric-rich sulfoaluminate cement

Ferric-rich sulfoaluminate cement (FR-SAC) is a promising low-carbon cement and is usually used to prepare precast products due to its short setting time. However, the fast setting of FR-SAC paste also leads to its poor fluidity and workability. Polycarboxylate superplasticizer (PCE) and hydroxypropyl methylcellulose (HPMC) can improve the fluidity and viscosity but may affect other properties of FR-SAC products. To get a suitable performance of FR-SAC by adding PCE or HPMC, the properties of FR-SAC paste with PCE and HPMC added and their influence mechanism were explored. The results indicate that PCE adsorbs on the surface of positively charged ettringite in the slurry under the electrostatic attraction, which makes the negatively charged or uncharged FR-SAC particles uniformly dispersed in the slurry, thus regulating the rheology and other properties of FR-SAC paste. The compressive strength of FR-SAC paste increases with the increase of PCE addition. PCE slightly retard the early hydration rate of FR-SAC but does not affect the formation of later hydration products. Adding HPMC to FR-SAC paste can decrease the fluidity and increase the viscosity of FR-SAC paste but has little effect on its hydration properties. Therefore, when PCE and HPMC are used to modulate the rheology of FR-SAC paste, it is necessary to combine the utilization process and compressive strength requirements to keep both the rheological parameters and compressive strength in the suitable condition.

Utilization of Quicklime and Limboto Lake Sediment as Basic Materials for Brick Walls

This study is based on knowing the compressive strength of bricks. The objectives that can be achieved are to analyze the characteristics of brick walls using lime, sedimentary soil and clay as well as conventional bricks and evaluate the comparative cost of making conventional bricks and lime-mixed bricks plus sedimentary soil. In this study, Data obtained from testing and analyzed quantitatively using appropriate statistical methods. This analysis will help in understanding the relationship between the composition of the mixture, the manufacturing process, and the characteristics of the resulting bricks. From the results of the analysis, the water absorption of bricks mixed with sedimentary materials, clay and lime. variation of sample 1, where the sample mixture (75% / 20% / 5%) water absorption is (29.72%) variation of sample 2, where the sample mixture (50% / 45% / 5%) water absorption is (9.45%) and Sample 3, (25% / 70% / 5%) water absorption is (9.22%). and clay bricks or without a mixture (100%) is (8.25%). This shows that the absorption capacity of mixed bricks of sediment, clay and lime materials which only have two variations 2 and 3. Meet the requirements of SNI 15-2094-2000 which requires a maximum water absorption capacity of 20% of bricks. While the average compressive strength comparison value of mixed bricks of sediment, clay and lime materials. sample variation 1, which sample mixture (75%/20%/5%) compressive strength value (13.6 kg/cm2) sample variation 2, (50%/45%/5%) which compressive strength value (19.8 kg/cm2) and sample 3, (25%/70%/5%) which compressive strength value (7.4 kg/cm2). and clay bricks without a mixture (100%) namely (36.4 kg/cm2). The compressive strength value of mixed bricks of sediment, clay and lime materials. Does not meet the minimum compressive strength requirements for building earthquake-safe houses (≥30).

The addition of silicon nitride to PMMA bone cements reduces bacterial attachment while supporting preosteoblast viability

Injectable poly (methyl methacrylate) (PMMA) bone cements are widely used in orthopaedics to stabilize fractures and for implant fixation. However, bacterial attachment to bone cements leads to significant complications that can create a need for implant revision. Common attempts at reducing bacterial attachment are through the addition of antibiotics or antibacterial nanometals to the bone cements. However, clinical data is inconclusive on the effectiveness of antibiotic-loaded bone cements and a negative osteoblastic response has been reported for certain additive concentrations. There is therefore a need for an additive that can positively affect osteoblastic behaviour while inhibiting bacterial attachment. Silicon nitride (Si3N4) could be such an additive, with initial studies showing promise in achieving antipathogenic properties. The aim of this study was hence to investigate the possibility of creating a bone cement that can support osteoblast growth while reducing bacterial attachment by introducing silicon nitride powders into an injectable PMMA cement. To this end, commercially available bone cements were doped with 5%, 10% and 20% weight/weight (w/w) of Si3N4. Their mechanical properties were examined through compression testing and their radiopacity was evaluated through fluoroscopy imaging. The samples that fulfilled compressive strength requirements had their biological properties tested using Staphylococcus epidermidis bacteria for antibacterial properties and MC3T3-E1 preosteoblasts for the examination of cytotoxicity. Bone cements that were doped with up to 20% w/w Si3N4 were radiopaque (only 13% reduction in optical density compared to radiopaque controls) and retained their compressive strength (85.35 ± 2.1 MPa compared to 83.4 ± 1.9 MPa for the commercial cements), while significantly reducing bacterial attachment by more than 90% compared to commercial cements and achieving a similar level of preosteoblast metabolic activity. This study supports further evaluation of Si3N4 as an additive to injectable bone cements as a way to create mechanically stable, radiopaque, bacteriostatic bone cements that could improve osteointegration.

The Effect of Acid Treatment Time, Particle Size, and Synthesis Method on the Physical and Mechanical Properties of Dental Materials Produced from Flue Gas Desulfurization (FGD) Gypsum

FGD gypsum, a byproduct of coal-fired power plants, is readily available and relatively inexpensive, which makes it an ideal material for a variety of applications. This study considered the use of FGD gypsum as a substitute for natural gypsum in dental materials. The goal of this research was to investigate how acid treatment time, particle size, and the synthesis method impact the physical and mechanical properties of dental materials to be used in a dental study model for training in dental sciences, and for casting a gypsum model after the removal of the impression material from the patient's mouth. The study used various sulfuric acid treatment times (15, 30, and 60 min), particle sizes (less than 0.1 mm, 0.1-0.35 mm, and 0.4-0.45 mm), and synthesis methods (Method A for dental plaster and Method B for dental stone). From the results, an acid treatment time of 15 min was sufficient for removing impurities from the FGD gypsum while enhancing the compressive strength. The smaller particles provided higher compressive strength than the larger particles. FGD gypsum became lighter in color when treated with sulfuric acid, and the crystal structure had a rough and porous surface. The synthesis methods had a significant influence on the physical properties of dental gypsum. The increased alpha calcium sulfate hemihydrate (α-HH) phase content resulted in improved compressive strength. The gypsum synthesized using Method B exhibited the highest compressive strength due to the presence of the α-HH phase of 65.9%. While gypsum synthesized using Method A contained a α-HH phase of 58.9%. For further study, once the suitable conditions for synthesizing gypsum that meet the compressive strength requirements of the ISO standard for dental materials are achieved, there will be ongoing research and development to improve various properties. Additionally, practical applications will be considered, such as using it in conjunction with modern techniques such as 3D printing instead of traditional die-casting methods.

Utilization of geopolymer in wood wool insulation boards: Design optimization, development and performance characteristics

This study investigates the substitution of ordinary Portland cement (OPC) with geopolymer in the production of wood wool geopolymer boards (WWGB), offering insights into manufacturing methods, design parameters, and performance characteristics. The composite formulation involves fibre pre-treatment, adjustment of precursor components, and control of activator compositions. The optimized formulation results in a lightweight composite with a density of 392 kg m−3 and porosity of 76 %, meeting prescribed minimum compressive (20 kPa) and bending strength (1700 kPa) requirements. The inclusion of natural fibres influences the optimal Na2O concentration and modulus for strength, with treated fibres recommended for higher modulus applications and improved strengths. Furthermore, it exhibits low thermal conductivity at 77 mW m−1 K−1, minimal moisture sorption, and low vapour resistance, offering a sustainable alternative in the field of insulation materials.

The potential of copper slag as a precursor for partially substituting blast furnace slag to prepare alkali-activated materials

The safe and efficient treatment of copper slag (CS) is an important aspect of the circular economy and green development. In order to reduce the negative environmental impact, CS is used as a precursor to substitute different contents of ground granulated blast furnace slag (GGBS) in the manufacturing of alkali-activated materials (AAM)) in this study. The feasibility of AAM incorporated with CS as a precursor is evaluated through the macroscopic performances including setting time, water requirement of normal consistency (WRNC), fluidity, compressive strength and flexural strength. Additionally, the microstructure is characterized using nuclear magnetic resonance (NMR), X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), scanning electron microscope (SEM) and thermogravimetric analysis (TGA), respectively. The results show that the optimal substitution rate of CS for GGBS in AAM mortar is 30 wt%. The compressive strength and flexural strength of AAM incorporated with 30 wt% CS at 28 days reach 71.7 MPa and 9.3 MPa, respectively, which are equivalent to the control group. The microstructure analyses reveal that the substitution of GGBS with CS reduces the formation of C-A-S-H due to the relatively low pozzolanic activity of CS. However, the micro-aggregates effect of CS and the filling effect of its hydration products (ferric hydroxide/ferrous hydroxide, and ferrosialate gels) can enhance the compactness of hardened paste and improve its mechanical performance.

Dolomitic Limestone Powder: Cement Substitute in the Production of Structural Concrete Paving Blocks

Manufacturers are replacing or combining cement with mineral additives such as slags, natural pozzolans, sand, diatomaceous earth and limestone to reduce carbon dioxide emissions and energy usage. Due to its high magnesium content, dolomitic limestone has long been utilized in concrete production to reduce costs and environmental risks associated with making cement. This study aimed to produce a reliable and appropriate concrete mixture for concrete paving blocks using dolomitic limestone powder that passed the no. 24 sieve as cement replacement at replacement levels of 0 (control mix), 8, 12, 16, 20, 24, 28 and 32%, satisfying the minimum compressive strength requirement for structural concrete of 20.7 MPa (3,000 psi). The ASTM E877-13 was used to sample the dolomitic limestone, and the 1:1.5:3 concrete class combination was utilized to proportion the quantities of cement, sand and aggregates (3/8”). After 28 days, the specimens were cured and the compressive strength, through the varying water-cement ratios in the concrete mixture, was determined. Results showed that dolomitic limestone powder can substitute cement by 16% by weight, using a concrete mix of 523-g cement, 936-g sand, 1,868-g gravel, 100-g dolomitic limestone powder, and 166-g water with a water-cement ratio of 0.318, exceeding the minimum necessary compressive strength of concrete of 20.7 MPa by 24.9% or 5.16 MPa. Therefore, it is advised to utilize this proven concrete mixture as a basis for a potential business venture in the production of concrete paving blocks for structural concrete applications such as walkways, sidewalks, parking lots and commercial areas, as well as in places where loads are very high, like airports, courtyards, docks and freight yards.

Synergistic impacts of high-volume fly ash and sugarcane bagasse ash on performance of cementitious composites reinforced with polyvinyl alcohol fibers

Disposal of waste materials in fertile land is one of the pressing environmental issues, disrupting human, animal, and plant life. This has led the researchers to process and use such waste in ecofriendly construction products like mortar and concrete. Their usage as supplementary cementitious materials (SCMs) would reduce the quantity of cement used in the manufacturing of cement-based materials, lowering CO2 emissions related with cement production. In this regard, this study examines the feasibility of replacing high-volume of ordinary Portland cement (OPC) in engineered cementitious composites (ECC) with two widely used waste materials, sugarcane bagasse ash (SCBA) and fly ash (FA) as SCMs. Five different mixes were produced, each containing a fixed amount of polyvinyl alcohol (PVA) fibers at a dosage of 1.5 % by volume of the mix and a constant cement content of 50 % by weight of the binder (OPC + FA + SCBA). However, FA was replaced with SCBA in these mixes up to 100 % by the combined weight of the waste materials (FA + SCBA) in increments of 25 % (i.e., FA100-SCBA0, FA75-SCBA25, FA50-SCBA50, FA25-SCBA75, and FA0-SCBA100). The results showed that the compressive strength and flexural strength of the composites with the increasing levels of SCBA were reduced. Interestingly, the 28-day compressive strength of composite incorporating 50 % FA and 50 % SCBA was still as high as 25.58 MPa, which satisfied the minimum compressive strength requirement of ASTM C270, making the newly produced ECC suitable for use in normal construction works and repairs. The same optimum mix (FA50-SCBA50) produced an average density of 1867.96 kg/m3 as a result of substituting a significant amount of binder with SCBA, demonstrating that it has evolved into a lightweight engineered cementitious composite. Furthermore, the ultrasonic pulse velocity of the mixes decreased whereas water absorption increased as the proportion of SCBA to FA increased. According to microstructural analysis, unreacted SCBA particles were mostly responsible for the detrimental effects of rising SCBA levels on properties of ECC. Based on the aforementioned results, this research concludes that sugarcane bagasse ash, when combined with fly ash, could be a viable alternative for replacing regular cement up to 50 % by weight in the production of cost-effective and environmentally friendly cementitious composites.