Weight Of Binder Research Articles

Propiedades del concreto de nano-alúmina con arena de circón como finos bajo variadas temperaturas elevadas

Los materiales de construcción de hormigón ahora se juzgan no solo por sus características económicas sino también por su capacidad de servicio. Los avances en la producción de hormigón ahora también se centran en mejorar el comportamiento resistente al fuego del hormigón. La sustitución de los áridos finos es mucho más deseable cuando estos poseen adecuadas características de resistencia al fuego. El presente trabajo de investigación comprende la urgente necesidad de prestar atención al comportamiento resistente al fuego del concreto minimizando al mismo tiempo el uso del agregado Natural River. Además del reemplazo de agregados finos, la nanoalúmina se usa como aditivo de cemento para respaldar de manera beneficiosa la durabilidad del concreto a través de sus características nanométricas. La arena de circón se usa hasta en un 50 % del agregado de arena de río natural y la nanoalúmina se usa en un 2 % en peso del aglomerante de cemento. Este trabajo de investigación se enfoca en la utilización de arena de zircón como agregado fino para producir concreto.

Effect of Binder Content on Silicon Microparticle Anodes for Lithium-Ion Batteries

Formulation strongly influences the structure, properties, and electrochemical performance in composite electrodes. The role of polymeric binders is especially critical for electrodes containing high volume change active materials, such as silicon. In this study, we investigated the impact of polyimide binder in silicon microparticle electrodes. The impact of binder content on electrode adhesion to the current collector, cohesion, porosity, electrical resistivity, local electrical connectivity, and silicon utilization was characterized in pristine and cycled electrodes to elucidate the mechanisms driving the electrochemical performance during rate and cycle life tests of Si-NMC622 full cells. We observed that capacity retention improved with increasing binder content, but rate performance suffered with excess binder content, indicating that there is an optimal binder weight fraction to balance the trade-off between these two metrics. Our research reveals important design principles for the optimization of binder content in silicon electrode formulations and can be applied to the development of electrodes containing other active materials and conductive additives.

Experimental investigation of the rheological behaviors of bitumen and stone matrix asphalt mixtures using waste material

The mechanical performance characteristics of bitumens and mixtures can be improved by the utilization of various modifiers, such as liquid rubber and natural bitumen. In the current study, the effect of liquid rubber and natural bitumen on the rheological behaviors of natural bitumen and liquid rubber/natural bitumen modified samples and Stone Matrix Asphalt (SMA) mixtures was evaluated. In this regard, 0, 5, 15, 25 and 35% natural bitumen as well as 7, 9, 11, and 13% liquid rubber by weight of binder were used to modify virgin binder. Also, to evaluate asphalt binder characteristics, rotational viscosity (RV), dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), and linear amplitude sweep (LAS) tests were applied. Furthermore, modified natural bitumen and liquid rubber/natural bitumen mixtures were evaluated by four-point beam fatigue (FPBF), resilient modulus (Mr), indirect tensile strength (ITS), dynamic creep, and wheel track experiments. The results indicated that the use of natural bitumen reduces the low-temperature cracking resistance of bitumens, while adding liquid rubber into natural bitumen modified bitumens, the low-temperature cracking of modified bitumens enhances. Moreover, application of natural bitumen resulted in a reduction in the resistance of bitumens against fatigue cracking, while using liquid rubber in natural bitumen modified samples, the fatigue life of bitumens increases. Also, natural bitumen enhances the resistance of bitumens to permanent deformations, while liquid rubber decreases it. The mixtures’ test results indicated that natural bitumen increases Mr, permanent deformation resistance, tensile strength, fracture energy, and intermediate temperature performance of mixtures. Moreover, liquid rubber has a negative effect on performance of natural bitumen-modified specimens.

Rheological property and extrudability performance assessment of construction and demolition waste-based geopolymer mortars with varied testing protocols

This study investigated fresh properties of 100% construction and demolition waste (CDW)-based geopolymer mortars providing innovative solutions for waste upcycling in favor of continuously transforming sustainable construction applications. Mortars were produced by utilizing hollow brick, red clay brick, roof tile, glass and concrete wastes as precursors and crushed concrete waste as aggregates. For activation, different combinations of NaOH-(molar concentrations of 7.5-10-12.5-15) and Ca(OH)2-(0-4-8%, by weight of binder) were used. For rheological assessments, different protocols including flow curve, constant shear rate, varied shear rate and three interval thixotropy testing (3ITT) were implemented. Ram extrusion was performed to investigate the extrudability performance of the mixtures. The study showed that the mortars’ rheological properties can be driven by arranging alkaline activator content. Although empirical approaches of flow curve, constant shear rate, and varied shear rate were able to verify the existence of thixotropy behavior, they were not capable of quantifying the viscosity recovery level of the mixtures, as opposed to 3ITT method. The 3ITT results showed that the viscosity recovery performances of geopolymers with varying activator content were between 65 and 82%. Ram extrusion demonstrated that mixtures were extruded without showing any types of failures, although some of them had different types of failures on the extruded specimen with the increased resting time beyond 60 min. However, except for 15M-activated mixtures, each mixture was extrudable even after 120 min. In general, this study presents a comprehensive investigation of assessing the rheological properties and extrudability performance of the CDW-based geopolymers via performing various testing methods.

Effect of silica fume on compressive strength of ultra-high-performance concrete made of calcium aluminate cement/fly ash based geopolymer

The study on geopolymers blended with silica fume is scant. This study investigates the effects of silica fume (SF) on the compressive strength of geopolymer-based ultra-high-performance concrete (G-UHPC) subject to ambient curing. Low-calcium fly ash (LCFA) and calcium aluminate cement (CAC) were activated by a combination of sodium hydroxide and sodium silicate solution to produce geopolymer binders. Effects of the CAC content, alkaline solution to binder (A/B) ratio, and sodium hydroxide (SH) concentration on the flowability and compressive strength of geopolymer binders were studied. The SF dosage varied from 5% to 30% of the total binder weight, and the Taguchi method was used to determine the optimum mix proportions. The incorporation of SF showed a complicated influence on the compressive strength, depending on the CAC content. For mixes with 20% CAC content, the compressive strength increased with increasing SF dosage. But for mixes with 10% CAC content, a high SF dosage (>10%) negatively influenced the compressive strength. The mechanisms for this contradictory behavior were discussed based on the X-ray diffraction and scanning electron microscopy analyses. The inclusion of steel fibers has a positive influence on the mechanical properties of G-UHPC. The G-UHPC mix with 1.5 vol% steel fibers achieved a compressive strength of 139.1 MPa and flexural strength of 13.5 MPa at 28 days. • Geopolymer-based UHPC was developed by incorporating calcium aluminate cement. • Taguchi analysis was used to optimise mixture compositions for geopolymer-based UHPC. • Effects of silica fume on the strength were explained via SEM and XRD analyses. • Effects of steel fiber on the mechanical properties were evaluated.

RETRACTED: Rheological behavior of asphalt binder and performances of asphalt mixtures modified by waste soybean oil and lignin

Effort has been made in this study to examine how the rheological behaviors of asphalt binder and performances of Stone Matrix Asphalt (SMA) mixture are affected using lignin and soybean oil. In current research lignin (3%, 5%, 7% by weight of asphalt binder) and soybean oil (5% by weight of asphalt binder) were added to modify-two types of virgin binders (AC 60–70 and AC 85/100). To assess different binders’ performance by checking their physical and rheological behavior, penetration grade, ductility, linear amplitude sweep, multiple stress creep recovery, Dynamic Shear Rheometer, rotational viscosity and softening point tests, and to evaluate asphalt mixtures’ performance, fatigue, rutting, indirect tensile strength and resilient modulus performances were evaluated. ANOVA is applied for statistically analyzing data. Rheological behaviors’ results showed the use of lignin additive increases the softening point and decrease the penetration grade. Using lignin decreases low temperature resistances of binder, whereas oil improves the bitumen’s low-temperature resistance. Multiple Stress Creep Recovery (MSCR) experiment result demonstrated an enhance in high performance temperature of the virgin binder at different stress levels by the addition of lignin. While, the utilization of oil decreases the rutting strength of sample. According to Linear Amplitude Sweep (LAS) outcomes, the use of lignin additive decreases fatigue property of the binders. While, soybean oil enhanced it. The mixtures experiment outcomes reveal the use of lignin increased the lasting deformation resistances, resilient modulus (MR), Indirect tensile strength (ITS), fracture energies. While, addition of oil has negative effect. Fatigue test results indicated that addition of lignin decreases the fatigue life of specimens, while soybean oil increases it. The Mr of the oil modified mixture is 7% lower than original mixture. While addition of 3%, 5%, and 7% lignin leads to increase the Mr by 3%, 18%, and 25%, respectively. Through the outcomes, addition of oil to 3% lignin modified mixture lead to decrease the FE by 1% which has the same value like original binder. Adding oil to mixtures comprising 3%, 5%, and 7% lignin leads to increase the rut depth amounts about 5%, 10%, 12%, respectively.

Combined effect of silica fume and fly ash as cementitious material on strength characteristics, embodied carbon, and cost of autoclave aerated concrete.

Aerated concrete (AAC) or lightweight concrete is primarily used for non-load bearing structures in construction work. Generally, it is produced with cement as a main binding ingredient, and the production of cement is blamed to contribute 7 to 8% of CO2 emission in the environment. In addition, the dumping of industrial wastes is also a great environmental concern. This research is an attempt to produce low-cost and sustainable aerated concrete utilizing silica fume and fly ash as partial substitution to cement without compromising the fundamental properties of aerated concrete. The current study was divided into two phases: in the first phase, the silica fume was substituted up to 20% with a variation of 5% in each mix. In the second phase, the fly ash was replaced with cement in three variations, i.e., 10%, 20%, and 30% containing an optimum proportion of silica fume obtained in phase 1. The aluminum powder was added at 0.4% by weight of binder to introduce aeration in concrete. Before testing, samples of aerated concrete were cured with steam in an autoclaving machine for 9h at a pressure and temperature of 1.5 bars and 127°C respectively and oven-dried at a temperature of 105°C for 24h after steam curing. From the experimental results, the highest compressive and split tensile strength of AAC was recorded when 15% of the cement was replaced with silica fume and 30% of the cement was replaced with fly ash combined. At this proportion the least density was also recorded which showed the lightweight of AAC without compromising the strength characteristics. In addition, the reduction of 42.64% and 32.4% of embodied carbon and cost was observed respectively.

Evaluating the Influence of Elevated Temperature on Compressive Strength of Date-Palm-Fiber-Reinforced Concrete Using Response Surface Methodology.

Due to its availability and affordable processing, date palm fiber (DPF) is among the natural and sustainable fibers used in cementitious composites. Furthermore, DPF is an agricultural, organic, and fibrous material that when subjected to higher temperature can easily degrade and cause reduction in strength. Therefore, the influence of elevated temperatures on the unit weight and strengths of DPF-reinforced concrete needs to be examined. Under this investigation, DPF is used in proportions of 0-3% weight of binder to produce a DPF-reinforced concrete. Silica fume was utilized as a supplemental cementitious material (SCM) in various amounts of 0%, 5%, 10%, and 15% by weight to enhance the heat resistance of the DPF-reinforced concrete. The concrete was then heated to various elevated temperatures for an hour at 200 °C, 400 °C, 600 °C, and 800 °C. After being exposed to high temperatures, the weight loss and the compressive and relative strengths were examined. The weight loss of DPF-reinforced concrete escalated with increments in temperature and DPF content. The compressive and relative strengths of the concrete improved when heated up to 400 °C, irrespective of the DPF and silica fume contents. The heat resistance of the concrete was enhanced with the replacement of up to 10% cement with silica fume when heated to a temperature up to 400 °C, where there were enhancements in compressive and relative strengths. However, at 800 °C, silica fume caused a significant decline in strength. The developed models for predicting the weight loss and the compressive and relative strengths of the DPF-reinforced concrete under high temperature using RSM have a very high degree of correlation and predictability. The models were said to have an average error of less than 6% when validated experimentally. The optimum DPF-reinforced concrete mix under high temperature was achieved by adding 1% DPF by weight of binder materials, replacing 12.14% of the cement using silica fume, and subjecting the concrete to a temperature of 317 °C. The optimization result has a very high desirability of 91.3%.

Influence of Palm Oil Fuel Ash on Mechanical Properties of Ultra-High-Performance Concrete

The cost of producing concrete has increased, and its effects on the natural environment have become apparent. The ideal solution is to use agro-waste material instead of cement in concrete. Palm oil fuel ash (POFA) is a by-product of the burning of waste material at the palm oil power plant. Looking at the utilization of POFA in concrete research, there has been study conducted on the behaviour of properties of normal strength concrete containing POFA in terms of compressive strength performance. However, the performance of ultra-high strengthconcrete produced using POFA is still lack. This research aims to determine how well POFA works as a cement substitute in ultra-high-performance concrete (UHPC).It also to determine the mechanical properties of ultra-high-performance concrete (UHPC) withPOFA addition. In this study, the percentage of POFA used as a cement replacement was 5%, 10% and 15% by binder weight. The results were collected from slump test and compressive strength test. Tabulation and graph illustration were the methods used to present the data. The workability test conducted showed that with the increase of POFA addition to the UHPC, the workability of fresh concrete was reduced. Meanwhile, the compressive strength at 28 days, UHPC with 5% of POFA addition showed the maximum valueof compressive strength at 84.12 N/mm2.

Effect of Cellulose Nanofibrils on the Physical Properties and Frost Resistance of Pervious Concrete.

Pervious concrete has good water permeability and, if used in construction, it can alleviate the heat island effect. However, its low strength and poor durability are major obstacles to its use. This study shows that nano-reinforced pervious concrete created by incorporating cellulose nanofibrils (CNFs) can improve the physical properties and increase the durability of pervious concrete. CNFs were added to the concrete mix in proportions ranging from 0.05% to 0.2% by weight of binder. The additions were found to alter matrix rheology. The hydration kinetics of matrix with differing CNF contents were compared and analyzed. The experimental results show the addition of CNFs delayed peak heat flow and maximum cumulative heat. The 28 d compressive strength of pervious concrete increased by up to 26.5% and 28 d flexural strength by up to 25.8% with the addition of 0.05-0.2% CNFs. Addition of 0.1% and 0.2% CNFs increased water permeability. Addition of 0.05-0.15% CNFs decreased mass loss by 73.2-83.7% after 150 freeze-thaw cycles, which corresponded to an increase in frost resistance. Denser matrices and stronger interfacial transition zones were observed using scanning electron microscopy when 0.05-0.2% CNFs were added.

Influence of Styrene-Butadiene-Styrene Polymer on Local Asphalt Characteristics

In this study the effect of Styrene-Butadiene-Styrene (SBS) polymer on local asphalts was investigated by comparing the performance of unmodified asphalt binder and hot mixture with binder and mixtures modified by SBS polymer modified asphalt (SBS-PMA) and its hot mixture. The comparison was made by evaluating the effectiveness of using different percentages (dosages) of this modifier to produce SBS-PMA. The penetration, ductility, elastic recovery, softening point, flash point, penetration and loss on heat tests for the asphalt binder was used. While, Marshall, indirect tensile strength (ITS), and index of retained strength (IRS) tests for the mixture was used in this study as they are the most available and economic. SBS polymer modifier was added to asphalt binders from Kirkuk governorate (KAT) and LANAZ refineries in Erbil governorate-Kurdistan region- Iraq in four percentages 3%, 5%, 7% and 9% by weight of the asphalt binder. The results showed that SBS polymer modifier significantly enhances the performance of asphalt binder and its hot mixture resulting in enhanced flexible pavements. However, adding 5% SBS leads to the best results of the Marshall test properties, and the moisture damage resistance, which increases the pavement performance against the environmental effects. Comparing the experimental results for both unmodified and 5% SBS polymer modified asphalts, showed that the replacement of the unmodified asphalt by 5% SBS polymer modified asphalt increased the stability by 26.00% for KAT asphalt and 21.34 % for LANAZ asphalt. Also, it increased the TSR by 15.63 % for KAT asphalt and 7.95 % for LANAZ asphalt and the IRS by 11.92% for KAT asphalt and 7.11 % for LANAZ asphalt. The regression analysis technique was applied to fit the mathematical relationship between the SBS polymer percentage and the Marshall stability of the hot mixture. Based on this investigation, the polymer modified asphalt is recommended to be used in new constructed roads to help reduce the amount of deterioration and maintenance cost in the region.

Effect of Biochar from Oat Hulls on the Physical Properties of Asphalt Binder.

The purpose of this study was to verify the feasibility of using biochar from oat hulls (BO) as a potential bio-modifier to improve the physical properties of conventional asphalt binder. The BO and asphalt binder were characterized by confocal (fluorescence) laser microscopy, scanning electron microscopy and Fourier transform infrared spectroscopy. Then, an asphalt binder modification procedure was established and modifications with 2.5, 5.0 and 7.5% of BO on the weight of the asphalt binder were evaluated, using a particle size < 75 µm. The physical properties of the evaluated modified asphalt binder with BO were: rotational viscosity in original and aged state, aging index, Fraass breaking point, softening point, penetration, penetration rate and storage stability. The results indicated that the BO has a porous structure, able to interact with the asphalt binder by C=O and C=C bonds. In addition, modification of the asphalt binder with BO increases the rotational viscosity related to high-temperature rutting resistance. The results obtained from the Fraass breaking point and softening point indicated that the use of BO extends the viscoelastic range of the asphalt binder. In addition, the evaluated modifications present low susceptibility to aging and good storage stability.

Electrochemical/Microstructural Studies on the Corrosion of Prestressed Steel Strand in Concrete with Naturally Ingressing Chlorides

The occurrence of environmentally assisted cracking (EAC) is as dependent on the aggressiveness of the environment as the susceptibility of the material and the presence of static tensile stresses. However, the influence of the environment has not been adequately considered in past investigations on EAC mechanisms of prestressing strands. This study utilizes various characterization techniques to evaluate the surface/bulk deterioration of corroded pretensioned concrete (PTC) specimens after natural chloride exposure (by diffusion through cover concrete). Corroded strands in two PTC prism specimens (3,000 mm × 150 mm × 200 mm) were characterized using electrochemical impedance spectroscopy (EIS) and other microanalytical techniques. The EIS and scanning electron microscope (SEM) images obtained after 1 y and 2 y of exposure revealed a negligible residual protectiveness of the passivated surface (although the concretes possessed high resistivity). Raman spectra, SEM, and x-ray computed tomography images of extracted corroded strands also provided unique insights into the pattern of corrosion propagation in PTC systems subjected to realistic chloride exposure. Microcracks in the bulk metal beneath flat-bottomed corrosion pits revealed the possible EAC at low chloride levels expected in service (&amp;lt;0.6% by weight of binder). The findings serve as a basis to define chloride-induced passive-to-active transition as the end of risk-free service life of PTC structures, and for considering it as the limit state for both service life design and corrosion assessment to avoid the onset of EAC.

Effect of impurities of steel fibers extracted from shredded tires on the behavior of fiber-reinforced concrete

Production of ductile and environmentally-friendly concrete is a dream come true thanks to the combined usage of recycled fibers and pozzolanic materials in the concrete mixture. The raw recycled steel fibers (RSF) stemmed from shredding waste tires underwent a process of preparation. Secondary products of tire-shredding technique, including recycled steel cords, rubber-attached fibers, tiny steel fibers, and free form of rubber particles, were recognized and removed from raw RSF sample, changing its status from impure to pure. The primary target of this study was to evaluate the contribution of RSF purification to the engineering properties of concrete containing 30% slag powder by weight of the total binder. Based on the results, purifying RSF negatively affected the ultrasonic pulse velocity and led to a less workable mixture with inferior compressive strength (fc). Interestingly, the highest fc was attained at 1% impure RSF, indicating a 40% enhancement compared to the plain concrete. The positive effect of RSF purification became visible considering the imperviousness and flexural performance of the mixture. However, a similar impure and pure RSF-reinforced concrete flexural strength could be achieved by doubling the volume of the impure RSF.

Effects of High-Volume bottom ash on Strength, Shrinkage, and creep of High-Strength recycled concrete aggregate

This research investigated the use of high-volume bottom ash in high-strength concrete containing recycled coarse aggregate (RCA). Bottom ash received directly from a power plant was sieved to separate it into two grades: 1) bottom ash that passed through a No. 50 sieve (FBA) and 2) bottom ash that passed through a No. 4 sieve and was retained on a No. 50 sieve (CBA). Then, FBA was ground to a fine powder (G-FBA) and used to replace Portland cement at 35 %–65 % by weight of binder. Also, CBA was used as a fine aggregate replacement at 50 and 100 % by volume. All high-strength concretes were tested to determine the compressive strength, elastic modulus, total shrinkage, and compression creep. The results showed that concrete containing 100 % RCA (RA concrete) had compressive strength reduced by about 10 % compared with conventional concrete (CT concrete). However, the use of high-volume G-FBA (35 to 65 % by binder weight) improved the compressive strength of concrete in the long term due to the influence of RCA. When G-FBA replaced 50 % of the ordinary Portland cement (OPC), the compressive strength of the resulting concrete was the same as that of CT concrete at 90 days, up to 94.5 MPa. For concrete incorporating G-FBA as a cement replacement and CBA as a fine aggregate replacement, the drying shrinkage was mitigated. The elastic modulus was decreased when RCA and CBA were used in concrete. Additionally, the creep strain of concrete was closely related to its compressive strength and elastic modulus; it decreased with increased compressive strength and elastic modulus. G-FBA, CBA, and RCA can be used as raw materials to make high-strength concrete more environmentally friendly and cost-effective.

Effects of copolymers on rheological and performance of binders and stone matrix asphalt mixtures

ABSTRACT This research examines the effect of Nano-high density polyethylene (NHDPE) and SBR (Styrene–Butadiene Rubber) additives on the binders and stone matrix asphalt (SMA) mixtures’ performance behaviours. AC-60/70 binder, NHDPE (0%, 2%, and 4% by weight of binder), and styrene butadiene rubber (SBR) (0%, 2%, and 4%, by weight of bitumen) are utilised. Besides, the impact of the combination of SBR (1% and 3%) with NHDPE (1% and 3%) on the rheological behaviour of bitumen and the mechanical properties of the mixture was assessed. The results of the experimental tests were statistically evaluated using a two-factor analysis of variance (ANOVA). According to the rheological behaviour test, using both SBR and NHDPE additives not only enhance binders’ rutting and fatigue resistance as well as phase separation but also decrease binders’ low-temperature resistance. Besides, adding SBR, NHDPE, and NHDPE/SBR enhances the fatigue and rutting resistance of binders. The utilisation of both SBR and NHDPE increases the permanent deformation resistance, MR, ITS, fracture energy, and fatigue properties of a specimen. It was also found that NHDPE in comparison with SBR has a better impact in enhancing the performance of the mixture.

Rutting-resistance investigation of amorphous carbon powder modified binder and asphalt mixture containing siliceous aggregates

ABSTRACT Amorphous carbon powder (ACP), an industrial waste material, is a potential asphalt binder modifier. In this study, the effect of ACP on the rutting performance of asphalt binders and mixtures was investigated. For this purpose, the frequency sweep, and multiple stress creep recovery tests of asphalt binders and resilient modulus, dynamic creep, and wheel tracking tests of asphalt mixtures were conducted on asphalt binders and mixtures containing 3, 5, and 10% of ACP by weight of total asphalt binder. The results showed that using 10% ACP caused a substantial improvement in the rutting parameter of asphalt binders, and the non-recoverable creep compliance values at both 0.1 and 3.2 kPa stress levels decrease by about 80% when modified with 10% ACP. The asphalt mixture results indicated that the indirect tensile strength, wheel tracking, and resilient modulus at 25°C enhanced by about 25%, 43%, and 40%, respectively when 10% ACP modified asphalt binder was used. Therefore, in addition to being a positive action in environmental protection, modifying asphalt binders with 10% ACP can improve the high-temperature performance of asphalt binders and mixtures.

The effect of materials and curing system on the behavior of self-compacting geopolymer concrete

Abstract The aim of the present work was to investigate and achieve the optimum compressive strength of self-compacting geopolymer concrete (SCGC). Fly ash (FA) and ground granulated blast furnace slag (GGBFS) are used at different ratios as binder materials to produce the SCGC mixes. Alkaline solution was a mix of sodium silicate and sodium hydroxide. Three different ratios of binder materials were used to produce SCGC (0FA-100GGBFS; 50FA-50GGBFS; and 100FA-0GGBFS). The total binder weight was 500 kg/m3 within a constant alkali–binder proportion (0.5). Two curing conditions were used, at ambient environment and heat curing at 110°C for 24 h. The compressive strength and fresh properties of SCGC are evaluated. The compressive strength is utilized to demonstrate the mechanical properties of SCGC. The compressive strength is investigated at two ages (7 and 28 days). The results showed that the use of GGBFS had a negative effect on the fresh properties of SCGC. However, it has a significant impact on the mechanical behavior of the SCGC. SCGC’s early strength is heavily involved in heat curing. The compressive strength of 100% GGBFS in the ambient environment after 28 days was more than that of GGBFS cured at 110°C. The optimum eco-friendly mix is 50FA-50GGBFS.

ÇİMENTO YERİNE KISMİ AHŞAP TABAN KÜLÜ İÇEREN HARÇLARIN MEKANİK ÖZELLİKLERİ

Carbon dioxide (CO2) released into the atmosphere during the production of Portland cement (PC) is one of the important factors causing global warming. Therefore, studies are carried out on different materials to reduce PC consumption. The effect levels of the wood bottom ash (WBA) ratio and specimen age on the response variables (compressive strength, flexural strength, and ultrasonic pulse velocity) were investigated in this study. Mortar specimens were produced using PC, WBA, CEN standard sand, and distilled water. The produced specimens were cured in water until the test day. WBA ratios are 0%, 5%, 10%, 20%, 35% and 50% by weight of binder. As a result, it was determined that the optimum WBA ratio was 5%. In addition, R2 values of response variables were found to be high (ultrasonic pulsed wave velocity; 0.8925, flexural strength; 0.9356, compressive strength; 0.9404) by analysis of variance (ANOVA). This shows that the models have a high correlation. Moreover, the terms added to the models have a significant effect on the responses.

Mechanical properties and key intrinsic factors of sprayed ultra-high performance concrete (SUHPC) with alkali-free accelerator

• Sprayed thickness and hydration mechanism of SUHPC with accelerator were analyzed. • Mechanical properties of SUHPC and poured UHPC were compared quantitatively. • Pores caused by instantaneous reaction and spraying are well investigated. • Reaction degree of silica fume with accelerator was characterized quantitatively. • Al-products and C S H gel of SUHPC and poured UHPC were compared and analyzed. A sprayed ultra-high performance concrete (SUHPC) with suitable sprayed thickness due to the addition of an alkali-free Al 2 (SO 4 ) 3 accelerator based on the designed UHPC has been developed in this research, which can be used as repair material for old concrete. The results reveal that the field sprayed thickness of SUHPC could be up to 45 mm due to the instantaneous reaction caused by the Al 2 (SO 4 ) 3 accelerator, and the accelerator dosage was only 2 % by weight of binder. Meanwhile, the compressive strength of SUHPC was 113.6 MPa, decreased 20.8 % compared with UHPC at cured for 28 days, the continuous hydration of cement and gradually activated pozzolanic of silica fume both are the guarantee of strength increase slowly in later hydration stage. Instantaneous reaction and spraying process both causes air bubbles will be easily trapped into fresh SUHPC and lately transfer to macro-pores in hardened SUHPC matrix. Due to the presence of the Al 2 (SO 4 ) 3 accelerator the hydration reactions of SUHPC dramatically differ from those of UHPC, such as the synthetic C S H doping by Al (from accelerator) increases the coefficient of Al[4]/Si and mean chain length may directly weaken matrix strength.