ASTM C1202 Research Articles

Preliminary investigation on spent garnet as a novel supplementary cementitious material

The escalating global demand for cement, a fundamental material in infrastructure development, has exacerbated environmental challenges, particularly through significant carbon dioxide (CO₂) emissions, which account for approximately 8.3 % of global anthropogenic CO₂ output. This research explores the potential of spent garnet powder, a byproduct of abrasive water jet machining, as a sustainable supplementary cementitious material (SCM) to mitigate these impacts. The spent garnet powder, characterized by a high concentration of silicon dioxide (SiO₂), aluminum oxide (Al₂O₃), and iron oxide (Fe₂O₃), was subjected to rigorous analysis. X-ray Fluorescence (XRF) confirmed its chemical suitability for pozzolanic applications, while laser particle size analysis revealed a finer granulometry relative to Ordinary Portland Cement (OPC), which is advantageous for enhancing pozzolanic reactivity. Scanning Electron Microscopy (SEM) demonstrated the angular and irregular morphology of the garnet particles, which is conducive to improved interfacial bonding within the cement matrix. X-ray Diffraction (XRD) identified active mineral phases that are critical for promoting pozzolanic reactions, and Thermogravimetric Analysis (TGA) demonstrated the material’s superior thermal stability, with minimal decomposition at elevated temperatures. Fourier Transform Infrared Spectroscopy (FTIR) identified strong silicon-oxygen (Si-O) and aluminum-oxygen (Al-O) bond structures, indicative of robust pozzolanic potential. The Strength Activity Index (SAI) and Frattini tests further substantiated the pozzolanic activity, revealing that a 10 % replacement of OPC with SGP not only enhances compressive strength but also meets the stringent requirements of ASTM C618. Additionally, the economic analysis underscores the cost-effectiveness of utilizing spent garnet powder, presenting a viable strategy for reducing both production costs and CO₂ emissions in the cement industry. This study conclusively positions spent garnet powder as a highly promising supplementary cementitious material, with significant implications for advancing sustainable construction practices and reducing the environmental footprint of cement production.

Characteristics of alkali-activated composites containing blast-furnace slag aggregate and ferronickel slag powder

The use of alkali-activated composites and alternative aggregates reduces the carbon dioxide emissions of the construction industry and mitigates the problem of aggregate depletion. However, published investigations into non-cement composites containing ferronickel slag powder (FSP) and blast-furnace slag fine aggregate (BSA) are limited. The aim of this study was thus to assess the mechanical properties and durability of non-cement composites containing FSP and BSA. The mix with 10% FSP and 25% BSA was found to have the highest 28-day compressive strength, of approximately 42.2 MPa. For the mixes with 5% FSP, the 28-day compressive strength increased with an increase in BSA content. Charge-passed tests revealed that, after 7 days, the sample with 5% FSP and 50% BSA exhibited a total charge of approximately 907 C, classifying it as ‘very low’ according to ASTM C1202. By 56 days, the total charge for this sample reached a value of approximately 120 C, close to ‘negligible’ as per ASTM C1202. It was thus concluded that an appropriate BSA content effectively enhances the mechanical properties and durability of non-cement composites.

Assessment of Various Mitigation Strategies of Alkali-Silica Reactions in Concrete Using Accelerated Mortar Test.

The widespread use of reinforced concrete continues to face challenges, particularly in mitigating alkali-silica reaction (ASR), due to its detrimental effects on concrete strength and durability. This paper investigates the effectiveness of using binary supplementary cementitious materials (SCMs) in mitigating ASR by incorporating metakaolin (MK) and waste glass powder (GP) as partial replacements for cement. Additionally, the potential of a new cement product, "NewCem Plus" (NCM), along with the use of basalt fibers and lithium, was evaluated through a 14-day accelerated mortar bar test following the ASTM C1260. This study also assessed concrete's properties such as its compressive strength and workability using the flow test. The results indicated that MK was effective, reducing expansion by 79%, 84%, and 88% with 10%, 20%, and 30% cement replacement, respectively, compared to the control mixture. On the other hand, GP showed a more modest reduction in expansion, with 10%, 20%, and 30% replacement levels reducing expansion by 20%, 43%, and 75%, respectively. Furthermore, the addition of lithium to MK significantly mitigated ASR, reducing expansion below the ASTM threshold. However, mixtures containing NewCem Plus, lithium, and basalt fibers showed minimal impact on ASR reduction. These findings underscore the viability of using binary or ternary blends of SCMs to mitigate ASR in concrete, encouraging their adoption in future concrete applications.

Accelerated environmental conditions study on palm oil fuel ash-incorporated engineered cementitious composites: A durability assessment approach

This study investigated the durability performance of Engineered Cementitious Composites (ECC) containing varying amounts of palm oil fuel ash (POFA) under accelerated environmental conditions. The research employed three distinct water-binder (cement + POFA) ratios (w/b) of 0.33, 0.36, and 0.38, along with POFA proportions ranging from 0 % to 1.2 % by mass of cement (POFA/C). Furthermore, ECC bars were immersed in 1 M NaOH at 80°C, with expansion and alkali-silica reaction monitored for 30 days. To examine the NaCl effect, ECC coupon specimens were first preloaded under four-point bending at 1.5 mm displacement, then exposed to a 3 % NaCl solution for 30 and 60 days, and then reloaded up to failure. The RCPT was performed at 28, and 90 days, per ASTM C1202 standard, by measuring the electrical current through a 50 mm thick, 100 mm diameter sample over 6 hrs. The results show that higher w/b ratios increased ASR-induced expansion in ECC bars, but higher POFA content mitigated this. ECC with 1.2 POFA/C at 0.33 w/b had the highest 0.1 % expansion at 30 days, within ASTM limits. The POFA-ECC specimens also exhibited enhanced chloride penetration resistance as POFA content increased, with the 1.2 POFA/C and w/b 0.33 specimens showing 61–71 % reductions in total charge passed at 28–90 days. Mechanically pre-loaded POFA-ECC remained durable when exposed to chloride. Additionally, POFA-ECC demonstrated self-healing of micro-cracks, allowing them to sustain significant flexural load capacity. These findings highlight the potential of POFA as a supplementary cementitious material in ECC, providing improved chloride resistance while preserving structural integrity.

Utilization of waste glass as precursor material in one-part alkali-activated aggregates

The increasing demand for glass products has led to a rise in waste glass (WG), which is commonly disposed of in landfills, causing environmental degradation. Moreover, the direct adoption of a high volume of WG as aggregates in concrete can lead to unfavorable ASR expansion due to its high level of reactive silica. This study explores a one-part alkali activation method to produce WG-based aggregates, aiming to reduce the reactive silica content, mitigate ASR expansion and increase the recycling rate of WG. Waste glass powder (WGP) with a replacement ratio of 100% was combined with two different alkalis (sodium metasilicate pentahydrate (Na2SiO3.5H2O) and sodium aluminate (NaAlO2)) through the cold-bonded one-part alkali activation method to produce WG-based alkali-activated aggregates (WG-AAAs). The influence of various activator contents (0%, 6%, 9%, 12% and 15%) on the physical and mechanical properties of the WG-AAAs was investigated. The WG-AAAs had a bulk density ranging from 920 to 1010 kg/m3, which can be classified as lightweight aggregates. The WG-AAAs with 12% NaAlO2 showed the best performance, with a water absorption of 8.46% and single particle crushing strength of 3.19 MPa. SEM-EDS and XRD results indicated that WG-AAAs with the supply of alumina from NaAlO2 exhibited a lower Si/Al ratio, leading to the formation of C-(N)-A-S-H gel, which improved the strength and creating a denser microstructure. Furthermore, the WG-AAAs showed no ASR expansion concerns, conforming to the expansion limit specified in ASTM C1260.

Effect of particle size and replacement ratio on mechanical performance of cementitious mortar containing ground recycled acrylonitrile butadiene styrene (GRABS) waste plastics

While waste plastics have been used as a natural sand aggregate replacement in cementitious mortar as a sustainable option to mitigate global accumulation of plastic waste in landfills, fundamental mechanical properties like compressive, tensile, and shear must be known to advance design and practical application of these cement-concrete composites as suitable building construction materials. Experimental testing is conducted to reveal to what extent the cementitious composite properties are altered, thereby influencing their overall mechanical performance, when both ungraded and graded ground recycled acrylonitrile butadiene styrene (GRABS) plastic are employed as substitutes for natural aggregates. The novelty of this research lies in its pioneering investigation to quantify the effects of varying particle sizes and volume fractions of waste plastics acquired through mechanical recycling and their influences on the mechanical properties of mortars containing plastics as a composite material. The results from fresh and hardened material properties are compared to conventional mortar properties to examine the impact of various GRABS particle sizes and volume fractions on the overall material strength. While replacing sand with waste plastic generally reduced mechanical properties, the resulting mixes still met the minimum compressive strength (4060 psi [28 MPa]) as per ASTM C150 standards for Portland cement. Notably, graded plastic particles with sizes less than 0.024 in [0.6 mm] demonstrated an overall improvement in mechanical properties compared to ungraded particles. Failure mechanisms responsible for compressive, tensile, and shear damage development are discussed by analyzing the fracture surfaces, which provide insight into the intricate relationship between waste plastic size and distribution on the mechanical behavior of mortar. The findings indicate that GRABS waste plastics, when combined with sand at appropriate particle sizes and volume fractions, have the potential to create tailored mixes to meet minimum mix design standards for construction applications.

Rapid Assessment of Sulfate Resistance in Mortar and Concrete.

Extensive research has been conducted on the sulfate attack of concrete structures; however, the need to adopt the use of more sustainable materials is driving a need for a quicker test method to assess sulfate resistance. This work presents accelerated methods that can reduce the time required for assessing the sulfate resistance of mixtures by 70%. Class F fly ash has historically been used in concrete mixtures to improve sulfate resistance. However, environmental considerations and the evolving energy industry have decreased its availability, requiring the identification of economically viable and environmentally friendly alternatives to fly ash. Another challenge in addressing sulfate attack durability issues in concrete is that the standard sulfate attack test (ASTM C1012) is time-consuming and designed for only standard mortars (not concrete mixtures). To expedite the testing process, accelerated testing methods for both mortar and concrete mixtures were adopted from previous work to further the development of the accelerated tests and to assess the feasibility of testing the sulfate resistance of mortar and concrete mixtures rapidly. This study also established criteria for interpreting sulfate resistance for each of the test methods used in this work. A total of 14 mortar mixtures and four concrete mixtures using two types of Portland cement (Type I and Type I/II) and various supplementary cementitious materials (SCMs) were evaluated in this study. The accelerated testing methods significantly reduced the evaluation time from 12 months to 21 days for mortar mixtures and from 6 months to 56 days for concrete mixtures. The proposed interpretation method for mortar accelerated test results showed acceptable consistency with the ACI 318-19 interpretations for ASTM C1012 results. The interpretation methods proposed for the two concrete sulfate attack tests demonstrated excellent consistency with the ASTM C1012 results from mortar mixtures with the same cementitious materials combinations. Metakaolin was shown to improve sulfate resistance for both mortar and concrete mixtures, while silica fume and natural pozzolan had a limited impact. Using 15% metakaolin in mortar or concrete mixtures with Type I/II cement provided the best sulfate resistance.

Investigation of Sugarcane Bagasse Ash (SBA)-Based Engineered Geopolymer Mortar Reinforced with Coconut Fibre for Engineered Geopolymer Composites

In recent years, there have been growing demand for fibre-reinforced cementitious composites using materials wastes to reduce cost and cement usage in concrete production. Therefore, this study aims to prepare sugarcane bagasse ash (SBA)-based geopolymer reinforced with coconut fibre as a material suitability evaluation for engineered geopolymer composites. The sugarcane baggase ash was characterised for its physical and chemical properties using scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD). The coconut fibres was added at 0%, 1%, 2%, and 3%, while the plain cement mortar was used as the control mix. Both destructive (compressive and tensile strength) and non- destructive test (water absorption, and ultrasonic pulse velocity test) were conducted on the resulting geopolymer mortar. The result of the SBA characterisation showed that the SBA met the ASTM C618 requirement for a pozzolanic material. The addition of 1% fibre to the geopolymer composite resulted in enhanced durability property than the plain cement mortar. The ultrasonic pulse velocity test demonstrated that bagasse ash-based geopolymer composites can be classified as a excellent cementitious material. The study also found the engineered cementitious composite showed better compressive and tensile strength than the plain concrete mortar, while the addition of fibre provided a denser microstructure for additional strength. The optimum fibre content was found at 1% for improved water absorption performance, UPV, and compressive strength. The study concludes that SBA composite reinforced with coconut fibre can provide better alternatives to achieve sustainability in engineered geopolymer concrete applications.

Mechanical Properties of Permeable Concrete Reinforced with Polypropylene Fibers for Different Water–Cement Ratios

Permeable concrete is a material that allows water filtration, reduces surface runoff, and maintains the natural water cycle. Previous studies have shown that its mechanical properties, particularly its compressive and flexural tensile strengths, are generally lower than those of conventional concrete, with significant variability observed among similar tests. This study investigates the compressive strength, flexural strength, and permeability of polypropylene fiber-reinforced permeable concrete specimens at two water–cement ratios (0.30 and 0.35). The mix design was conducted using the ACI 522R-10 method. Forty-eight cylinders measuring 200 mm × 100 mm were fabricated for permeability and compression tests. Additionally, 12 beams measuring 100 mm × 100 mm × 350 mm were produced and subjected to simple flexural testing in accordance with ASTM C78 guidelines. Compressive strength versus permeability and load versus deflection graphs were plotted, and the fracture energy was calculated for various deflections. The results indicate that the addition of fibers increased permeability and tensile strength but decreased compressive strength. Furthermore, an increase in the water–cement ratio led to higher compressive and flexural tensile strengths.

Utilization Of Buton Asphalt Solid Waste (ASW) Waste Bitumen Extraction In Concrete

Indonesia has 650 million tons of Buton Rock Asphalt (Asbuton) deposits. �The mineral residue, known as Asphalt Solid Waste (ASW). The extraction left ASW by 65-90% of asbuton�s weight. However, 770 thousand tons/year of ASW remain underutilized, causing environmental pollution due to its hydrocarbon content. Based on XRD results, Asbuton minerals were dominated with 46% CaCO3, which are potential as a subtitute material in concrete. However, its hydrocarbon content at 68,911 ppm raises concerns. To prevent ASW hydrocarbons from contaminating concrete, solidification was attempted. This study investigates solidification by making Artificial Coarse Aggregate (ACA) products and using ASW as a subtitute for gravel in concrete. The ACAs were produced from a mixture of ASW and cement, molded into 50 x 100 mm cylinders, crushed after twenty eight-days moist curing, and tested according to ASTM C33 standard of gravel. ASW replaced 0-12.5% by volume of sand and ACA replaced 0-12.5% by volume of gravel in concrete with a target compressive strength of 45 MPa at twenty eight-days. Heat of hydration and shrinkage were tested to indentify the impact of CaCO3 from ASW on concrete. The results showed that ACA could reduce 9% of ASW hydrocarbons. However, the ACA produced did not meet the gravel standard in ASTM because ACA absorption reached 6.75% and abrasion test up to 57%. Neverthless, ASW�s high absorption reduced heat hydration by 10% and shrinkage by 83% compared to normal concrete.

Development and Properties of Recycled Biomass Fly Ashes Modified Mortars

The production of biomass fly ash has been increasing every year in Europe, reaching 5.5 million tons in 2020. Fly ash produced by burning biomass is not yet accepted in the standards as a substitute material for cement in mortar and concrete. In a first approach, the substitution limit of biomass ash is determined by comparing the mechanical strengths (among others, compressive strength), fresh state properties and hardened properties of mortars produced with fly ash with those of mortars produced with coal fly ash (EN 450-1 and ASTM C618). Masonry and rendering mortars have been designed with different substitution rates of fly ashes from wood combustion in thermal power plants. Although there is an overall decrease in performance, mortars made with biomass ash retain properties that make them suitable for use in masonry (loss of 13% compressive strength for masonry mortars with 10% substitution rate after 90 days) or rendering (loss of 20% compressive strength for rendering mortars with 10% substitution rate after 90 days). Water absorption and porosity (24.1 and 23.7% for masonry and rendering mortars, respectively) are, however, not significantly modified, which potentially contributes to good durability properties.

Answers to Your Resistivity Questions and Helpful Findings to Develop a Robust Resistivity Specification

Many states are currently in the process of evaluating the use of surface resistivity (SR) or bulk resistivity (BR) tests to assess permeability of concrete in lieu of the standard test method for electrical indication of concrete’s ability to resist chloride ion penetration (AASHTO T 277 and ASTM C1202) which is commonly referred to as the rapid chloride permeability test (RCPT). A few states, such as Louisiana and Maine, implemented resistivity testing in their specifications many years ago. As with any test method implementation, it is important to learn from data generated and experience gained to further refine the specifications in respect of both testing protocols and the specification limits. In this paper, the Federal Highway Administration’s Mobile Concrete Technology Center SR and BR data from 30 field projects in 25 states is analyzed to provide information that could be helpful to agencies as they specify or improve their specifications with respect to resistivity testing. This paper attempts to answer questions related to 1) change in resistivity testing results with age, 2) range and variability of resistivity data from mainline paving mixtures, 3) comparison of test results between SR and BR data, 4) comparison of resistivity data gathered with equipment from various vendors, and 5) use of 28 versus 56 day data.

Geopolymer mortars having glassy materials considering mechanical and microstructural features

In comparison with ordinary Portland cements, geopolymer-based cements are now gaining prominence as an eco-friendly substitute to decline CO2 emissions in the course of OPC manufacturing. In this study, mechanical/microstructural features of geopolymers under different curing heats using 12 M NaOH as alkaline activator, obsidian and waste glass powder as binder at different dosages (0 %, 25 %, 50 %, 75 % and 100 %) were investigated. The mixture calculations of 5 different series of geopolymer mortars were produced, as stated by ASTM C109. Samples were cured for 4 different temperatures (75, 90, 105 and 120 °C) for 72 h and then kept in ziplock bags at room conditions until the mechanical tests after curing of up to 90-day. At 7-90-day, samples' flexural/compressive strengths were detected, as stated by ASTM C348/349 standards, respectively. Microstructural examinations of mortar samples were also made by ensuing practices: XRD, SEM-EDS and FTIR. Laboratory findings disclosed that an ideal compressive/flexural strength of 52.6/13.75 MPa was obtained from mortars with waste glass and obsidian binder subjected to a curing temperature of 75 and 90 °C. In addition, one can clearly observe that it exists a substantial link between microstructure images obtained from SEM analysis and compressive/flexural strength results. From existing investigation, one could conclude that substitution of obsidian joining high reactive content into waste glass rose mortars’ flexural/compressive strengths. Considering mechanical/microstructural features obtained from the present investigation, it is seen that obsidian, an inert material, and waste glass, a waste material, could be employed separately or together to create a new geopolymer product.

The Use of Ground Coal Bottom Ash/Slag as a Cement Replacement for Sustainable Concrete Infrastructure.

Cement production requires considerable energy and natural resources, severely impacting the environment due to harmful gas emissions. Coal bottom ash (CBA) and coal boiler slag (CBS), byproducts of coal-fired powerplants having pozzolanic properties, can be mechanically ground and replace cement in concrete, which reduces waste in landfills, preserves natural resources, and reduces health hazards. This study was performed to determine the optimum cement replacement amount of ground CBA (GCBA) and ground CBS (GCBS) in concrete, which was 10% for GCBA and 5% for GCBS. GCBA-based concrete exhibited superior tensile strength, modulus of elasticity, and durability compared to the control. In the Rapid Chloride Penetration Test, 10% GCBA concrete resulted in 2026 coulombs at 56 days, compared to 3405 coulombs for the control, indicating more resistance to chloride penetration. Incorporating 2.5% nanoclay in GCBA-based concrete increased the optimum GCBA content by 5%, and the compressive strength of 15% GCBA concrete increased by 4 MPa. The mortar consisting of the finest GCBA(L1) having Blaine fineness of 3072 g/cm2 yielded the highest compressive strength (32.7 MPa). The study discovered that the compressive strength of GCBA and GCBS-based mortars increases with fineness, and meeting the recommended fineness limit in ASTM C618 enhances concrete or mortar properties.

Acidification in cement paste in which clinker is partially replaced with limestone or silica

This paper examines the acid resistance of cement pastes where a portion of the cement clinker is replaced with limestone (LS or calcium carbonate, CaCO3) or ground silica (GS). Specifically, the work is intended to better understand the acid resistance of ASTM C595 IL cement as compared with ASTM C150 cement. The performance of OPC, OPC + GS, and OPC + LS systems were tested in sulfuric acid baths where the pH was held constant at 2.0 and 3.0 using an automated setup that uses titration to add acid. The degradation of the cement paste was measured as a function of time. Thermogravimetric analysis (TGA) was used to quantify changes in the calcium hydroxide (Ca(OH)2) and calcium carbonate (CaCO3) contents of the paste. In addition, the flexural strength of the cement paste specimens was measured. Results indicate that the dissolved sulfate and calcium concentrations due to acidification were not noticeably different for the OPC + GS and OPC + LS mixtures exposed to the same pH. However, as expected, differences were observed between the samples immersed in the solution of pH∼2 and pH∼3 sulfuric acid with the lower pH corresponding to more severe deterioration. TGA results showed that Ca(OH)2 is more susceptible to acid attack than limestone as evidenced by the larger Ca(OH)2 and sulfuric acid consumption in samples immersed at pH∼2. The additional acid consumption that is beyond the consumption of Ca(OH)2 can be explained by the acid attack of other hydration products such as CSH and unreacted cement phases. This results in a significant B3B flexural strength loss for the samples immersed in a pH∼2 as compared to those in the pH∼3 solution. The results demonstrated that the performance of ASTM C595 IL cements was promising and comparable with ASTM C150 cements.

Experimental Investigation and Classification of Wastewater Treatment Sludge as Pozzolan for Cement

This paper presents an investigation conducted to evaluate wastewater treatment sludge for potential use as a cement extender or pozzolan. Two varieties comprising the digested wastewater sludge (DWWS) and activated wastewater sludge (AWWS) materials, were finely ground then calcined at 750 °C for 30 min. Subsequently, the calcined sludge waste materials were blended with ordinary Portland cement CEM I 52.5 N at 0, 10, 20, 30% DWWS or AWWS, and used to prepare mortar mixtures at proportions of 1:3:0.61 cement to sand to water. Various tests were conducted including workability, compressive strength, pozzolanic activity with lime, drying shrinkage and alkali-silica reaction. It was found that both varieties of the sludge waste materials, once blended with CEM I at 20% DWWS or 20% AWWS, satisfied the ASTM C618 criteria for Class C pozzolan, and may be classified as CEM II /A-P 32.5 N,R cement type of EN 197-1/SANS 50197-1. The overall performance of DWWS was relatively better than that of AWWS.

The Influence of e-glass epoxy composite laminate material application on the crack pattern of cylinder concrete column cross-section

In order to better understand the phenomenon of applying GEC reinforcement to RCC based on the percentage of surface crack pattern (PCP), this research will use e-glass epoxy composite laminate (GEC) to obtain the damage pattern of reinforced concrete column specimens (RCC) utilizing GEC. Additionally, it will compare the splitting tensile strength (STS) and SCP. In accordance with ASTM C496 guidelines, the RCC specimens used in this investigation had a cylindrical shape and measured 150 mm in length and 50 mm in diameter. GEC material, consisting of 0–4 layers of woven e-glass fiber sheets, was applied as an extra layer on top of the RCC. In compliance with ASTM C496 guidelines, a Universal Testing Machine (UTM) was used to perform the split tensile test. With the aid of Adobe Photoshop software, the Histogram approach was used to calculate the crack pattern's proportion. The study's findings demonstrated that the specimens reinforced with four layers of GEC exhibited the highest damage pattern. This suggests that the reinforced specimens must be subjected to a sizable load in order to be damaged. Hence, the damage that occurs in the specimens can be lessened by applying GEC layers on RCC. Further information about the performance of RCC reinforced with GEC is also provided by a comparison of the splitting tensile strength and the percentage of fracture pattern

Study on the cementation and engineering properties of ternary eco-binder mortar containing pulverized coal fly ash mixed with circulating fluidized bed co-fired fly ash

This study aimed to verify the role and feasibility of co-fired fly ash (CFA) as an alternative construction material. It also demonstrated the engineering properties of CFA mortar and compared them with those of pulverized coal fly ash (PCFA) mortar. Further, CFA-PCFA-cement mortar specimens were mixed to produce ternary eco-binder mortars and find the optimal application proportion. The results pointed out that the pozzolanic strength activity index of CFA was 76 %, with only a slight pozzolanic reaction. The sum of the chemical composition (SiO2+Al2O3+Fe2O3) of CFA was insufficient to meet ASTM C618 requirements, and it was deduced that a small amount of CFA should be used as the substitute for cement or fine aggregates. Specimens with CFA replacing fine aggregates contributed to lower water absorption, improved sulfate resistance, and increased compressive strength; Specimens with CFA replacing cement reduced shrinkage and improved sulfate resistance but decreased compressive strength and increased absorption. Blended CFA-cement mortars consisting of 5 % CFA as a replacement material for cement and fine aggregates had excellent engineering properties. Ternary blended CFA-PCFA-cement mortar exhibits superior engineering properties. The optimum proportion is an economy-friendly binder composed of 10 % CFA (5 % as cement and 5 % as fine aggregates) and 10% PCFA (as a replacement for cement).

Response Surface Optimization of Rice and Guinea Corn Husk Ash Blended Concrete

Concrete, a fundamental construction material, consists of aggregates, water, cement, and additives. Unfortunately, the large-scale production of cement is a major contributor to carbon dioxide (CO2) emissions, primarily from the manufacturing process and the consumption of fossil fuels. This not only incurs environmental costs associated with global warming but also depletes vital limestone deposits. To mitigate these issues, this study aims to explore the optimal utilization of Guinea Corn Husk Ash (GCHA) and Rice Husk Ash (RHA) in concrete. This research investigated the chemical properties of GCHA and RHA, and their impact on the compressive and split-tensile strengths of concrete when integrated in various proportions. The study reveals that both GCHA and RHA meet the minimum oxide content requirement of 70% set by ASTM C618, with silicon dioxide (SiO2) as the predominant oxide. Increasing the content of RHA and GCHA from 5% to 10% improves the concrete's compressive and split-tensile strengths after curing for 56 days. Optimization results indicate that the ideal mix consists of 10% GCHA, 8.5% RHA, and 82.5% cement, yielding a compressive and split tensile strength of 31.34 N/mm² and 3.07 N/mm² respectively. This study thus offers a promising solution for sustainable concrete production by reducing the environmental footprint of cement while enhancing material properties and promoting an eco-friendlier approach to construction. Keywords: Concrete, Guinea Corn Husk Ash, Rice Husk Ash, Compressive Strength, Split-Tensile Strength

Evaluation of Cherts in Gumushane Province in Terms of Alkali Silica Reaction

Alkali–silica reaction (ASR) occurs when alkali oxides coming from the cement composition in concrete come together with reactive silica and moisture coming from the aggregate. Additional maintenance and repair costs caused by the development of ASR in concrete cause the cost to increase. However, thanks to the measures taken against ASR in the early period, it contributes to the creation of sustainable and durable concrete structures. The article investigated the usability of cherts with eight different chemical compositions as aggregates in ready-mixed concrete plants in Gümüşhane. Cherts have been investigated for alkaline reactivity and are intended to be used largely as a source for concrete plants. ASR length changes of the samples prepared according to ASTM C1260 standard were determined after 3, 7, 14, and 28 days of the curing period. Microstructural examination, ultrasonic P-wave velocity, and bending and compressive strength experiments supporting ASR were carried out. The obtained test results were compared between the reference (limestone) sample and each other, as well as with the values specified in the standards. The compressive and bending strength values of the samples increase depending on their ASR. It was observed that the crack structures and types increased depending on the increase in the crack values.