Workability Of Mixtures Research Articles

МЕТОДИ ВИПРОБУВАННЯ СУМІШЕЙ, УКРІПЛЕНИХ ГІДРАВЛІЧНИМ В’ЯЖУЧИМ, ВІДПОВІДНО ДО ВИМОГ ЄВРОПЕЙСЬКИХ СТАНДАРТІВ

Hydraulically bound mixtures have been widely used for road building industry in base layers of flexible and rigid pavements to enhance the bearing capacity and ensure the stability of base layers when built in complicated ground-hydrogeological conditions. This article continues the cycle of publications regarding hydraulically bound mixtures, deals with an analytical review of methods for its testing and represents possibilities to choice the strategy for construction a road pavement layer from bound material. The methods for testing hydraulically bound mixtures can be divided, in general, into methods for testing fresh mixed material (the mixture itself) and those for testing bound materials. The strategy for construction a road pavement layer from bound materialcan be correctly chosen applying methods for testing fresh mixtures for workability and immediate bearing index which are not implemented in the native practice of road building industry. A value of the mixture workability represents the period of time from its manufacturing to compaction in a layer during which that layer could be re-worked, if required. In comparison with the appropriate national requirements based only on the setting times of a hydraulic binder, the workability criterion is more precise and valuable and allows to widethe above mentioned time period. Immediate bearing index (IBI) sets the mechanical stability of a compacted mixture and shall be used to evaluate the ability of a mixture layer to withstand the traffic immediately after compaction. IBI criterion is valuable while constructing the road pavement layer using slow hardened hydraulic binder or when the rapid construction technology is a matter. After implementation, these standard methods for tests of fresh mixtures will permit the improved economical performance and quality of road pavements construction. The fundamental classification of hydraulically bound mixtures is based on their mechanical strength.The mechanical properties of hardened materials, in accordance with European Norms, shall be tested in unconfined compression or in tension – direct or indirect one. The indirect tensile strength shall be determined as splitting tensile strength only. One more criterion for fundamental classification is the modulus of elasticity of hardened materials that shall be determined when carrying out the compressive or tensile testing. Given these criteria, hardened materials can be classified by one of the two substantive methods: by classes relating the compressive strength or by classes relating the relationship “tensile strength/modulus of elasticity”. In the national system of standards, the materials bound by the mineral binders are classified by complex of their compressive and bending tensile strengths. Among these methods, the classification by the relationship “tensile strength/modulus of elasticity” is the most reliable one that ensures the modeling regime closest to the performance of bound material in the pavement layer. Together with that, the method approved in the national system of standards gives the correct classification of bound materials and considers all the requirements of national building codes relating road pavements designing. Keywords: hydraulically bound mixture; fresh mixture compacity; fresh mixture workability; immediate bearing index; compressive strength; tensile strength; modulus of elasticity.

Thermal resistance, water absorption and microstructure of high-strength self-compacting lightweight aggregate concrete (HSSC-LWAC) after exposure to elevated temperatures

An experimental investigation on the influence of elevated temperatures on the thermal resistance, water absorption and microstructure of high-strength self-compacting lightweight aggregate concrete (HSSC-LWAC) is presented. In total, 315 concrete specimens from 7 different mixtures with different replacement ratios (0, 30 %, 50 % and 100 % by weight) of two kinds of LWAs, namely cloud concrete stone (CCS) and fly ash ceramsite (FAC), were prepared. The workability of fresh concrete mixtures including slump, J-Ring and T500 tests was first conducted aiming at meeting the requirements of self-compacting performance. Hardened concrete specimens were then exposed to different elevated temperatures (i.e. 200 °C, 400 °C, 600 °C and 800 °C) increased with a heating rate of 10 °C/min. A series of tests including the apparent morphology, ultrasound pulse velocity (UPV), residual compressive strength and capillary water absorption were carried out on unheated control concrete and after air-cooling period of heated concrete. Finally, the thermal analysis and microstructural observation were further conducted through the thermogravimetry (TG), differential scanning calorimetry (DSC), mercury intrusion porosimetry (MIP), laser scanning microscopy (LSM) and scanning electron microscope (SEM) to characterize the evolution of high temperature damage. Generally, the high temperature resistance of HSSC-LWAC shows an increasing trend as the LWAs content increases, while the residual mechanical strength increases and then decreases with an increase of the temperature gradient. The microstructural observation indicates that the evolution behavior of thermal damage promotes the continuous development of micropores in the interfacial transition zones (ITZ) to form wider microcracks, resulting in the degradation of residual mechanical properties.

The effects of adding molybdenum tailings as cementitious paste replacement on the fluidity, mechanical properties and micro-structure of concrete

To reduce the land occupation and environmental pollution caused by the accumulation of molybdenum tailings (MT), MT has been used as cement or fine aggregate replacement to produce concrete. Molybdenum tailings concrete (MTC) was prepared by replacing cement paste with MT of equal mass in this study in order to offer one more option for the adding of MT into concrete. The workability of the concrete mixture and the mechanical properties of the hardened concrete were investigated. The internal pore structure characteristics and micro-morphology of MTC were analyzed by nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM), respectively. The results showed that, as the MT replacement rate increases, the slump of the concrete mixture decreases, the air content increases firstly and then decreases, the compressive strength and splitting tensile strength decreases firstly and then increase with the optimum MT replacement rate at 10%; the total porosity of concrete increases and then decreases, both the compressive strength and splitting tensile strength are inversely proportional to the porosity. When the MT replacement rate is 7.5% and 10%, the number of medium capillary pores (0–100 nm) decreases significantly, while the number of capillary pores (100–1000 nm) and air pores (>1000 nm) gradually increases.

Production of sustainable self-consolidating mortar with low environmental impact.

Reusing industrial by-products and agricultural waste as supplementary cementitious materials for producing sustainable concrete is one of the most promising ways to reduce cement production and the detrimental effects of concrete constructions on the environment. However, when it comes to preparing self-consolidating concrete (SCC) and mortar (SCMO) containing such materials in high volume, bleeding, and segregation of theirfresh mixture are the crucial factors hindering theirlarge-scale application. In this regard, the main aim of this study is to address such issues by designing sustainable SCMO using ground granulated blast furnace slag (GGBS) in high volume and rice husk ash (RHA) with comparatively lower environmental impact and high quality. To achieve this goal, the workability of fresh mixture and all its three main characteristics, including segregation resistance, passing ability, and filling ability, were evaluated with recently developed empirical apparatuses. For this purpose, 12 mixtures with different compositions were prepared to investigate the fresh properties, compressive strength, setting time, and environmental impact index. The results indicate that there are inextricable links between mixing proportions, strength, and carbon emissions of the mixture. Sustainable SCMO with an embodied-CO2 index lower than 4.5kg/MPa.m3, good workability, and compressive strength of 49.7MPa was designed by optimizing cementitious content, while the e-CO2 index of the control mixture was around 8kg/MPa.m3. The addition of GGBFS and RHA not only decreased the e-CO2 index but also increased the unit cement strength contribution index. The results also indicated that by increasing GGBFS, the fluidity and segregation of the mixture increased while adding RHA increased viscosity and modified bleeding and the segregation index. Moreover, the growth rate of the compressive strength in mixtures containing GGBFS was much higher than that of the control mix at the same age. The promising results of this experimental study indicate that utilization of GGBFS and RHA in SCMO mixture can provide a practical way to reduce the environmental effects of cement production and pave the way for friendly disposal of slag and waste products.

Performance of Self-Compacted Geopolymer Concrete Containing Fly Ash and Slag as Binders

Geopolymers can replace cement and help reduce the environmental impact of concrete construction, but research is needed to ensure their mechanical properties, durability and practicability. The aim of this investigation is to examine the influence of ground granulated blast furnace slag (slag) content on the performance, at the fresh and hardened states, of fly ash (FA) based self-compacted geopolymer concrete (SCGC). For this purpose, four SCGC mixtures containing 450 kg/m3 of total binder were examined. The alkaline-to-binder ratio was 0.5 for all mixes. FA was substituted with slag at 0%, 30%, 50%, and 100% of the total binder content. The fresh properties in terms of flowability, passing ability, viscosity, and segregation resistance, as well as the mechanical properties in terms of compressive strength and splitting tensile strength, were quantified. The durability behavior of SCGC was also studied to determine sorptivity and long-term free drying shrinkage. The results confirm that slag adversely affects the workability of SCGC mixtures except for the resistance to sieve segregation. Performance of SCGC in hardened states is in general enhanced with slag inclusion but at increased shrinkage strain. Predictions of splitting tensile strength were made using the ACI 318, ACI 363, Eurocode CEB-FIB, and Lee and Lee models. The ACI 363 and Eurocode CEB-FIB models were found to be inaccurate, except for the 30% slag mix. Predicted values obtained from the Lee and Lee model were very close to the actual values of the FA-based SCGC mix. The results of this work could lead to more sustainable concretes using geopolymers instead of OPC.

A Comparative Review of Hot and Warm Mix Asphalt Technologies from Environmental and Economic Perspectives: Towards a Sustainable Asphalt Pavement.

The environmental concerns of global warming and energy consumption are among the most severe issues and challenges facing human beings worldwide. Due to the relatively higher predicted temperatures (150-180 °C), the latest research on pavement energy consumption and carbon dioxide (CO2) emission assessment mentioned contributing to higher environmental burdens such as air pollution and global warming. However, warm-mix asphalt (WMA) was introduced by pavement researchers and the road construction industry instead of hot-mix asphalt (HMA) to reduce these environmental problems. This study aims to provide a comparative overview of WMA and HMA from environmental and economic perspectives in order to highlight the challenges, motivations, and research gaps in using WMA technology compared to HMA. It was discovered that the lower production temperature of WMA could significantly reduce the emissions of gases and fumes and thus reduce global warming. The lower production temperature also provides a healthy work environment and reduces exposure to fumes. Replacing HMA with WMA can reduce production costs because of the 20-75% lower energy consumption in WMA production. It was also released that the reduction in energy consumption is dependent on the fuel type, energy source, material heat capacity, moisture content, and production temperature. Other benefits of using WMA are enhanced asphalt mixture workability and compaction because the additives in WMA reduce asphalt binder viscosity. It also allows for the incorporation of more waste materials, such as reclaimed asphalt pavement (RAP). However, future studies are recommended on the possibility of using renewable, environmentally friendly, and cost-effective materials such as biomaterials as an alternative to conventional WMA-additives for more sustainable and green asphalt pavements.

Effect of warm mix asphalt additive on the workability of asphalt mixture: From particle perspective

Warm mix asphalt (WMA) technologies, in recent decades, have gained much popularity given their proven benefits of improved workability, reduced energy consumption, and improved sustainability. However, how to select a WMA technology and determine its effectiveness at a required condition is still a question. Most current works focus on the binder’s rheological properties. Very few have investigated the particles’ behaviors during compaction, which should have a direct correlation with the mixture’s workability. With the development of a particle-size Microelectromechanical System (MEMS) sensor, SmartRock, this paper aims to analyze the particle’s kinematic behavior during compaction and explore its relationship with the mixture’s workability. With this motivation, 5 asphalt mixtures varying in the production temperature and the dose rate of the chemical additive are prepared and compacted in this study. To focus on the methodology, only one chemical additive with several dosage levels is utilized. It is found that particle rotation is a crucial property for compaction and can be used to evaluate the workability of asphalt mixtures. Relative rotation capacity (RRC) and average residual rotation (ARR) are then proposed and used to evaluate the mixture’s workability. It is verified that the higher production temperature and dosage rate of chemical additives can both improve the particle rotation and the mixture’s workability. The effect of temperature and WMA additive on workability improvement is different for the base conditions (i.e., base production temperature and usage of the WMA additive). Overall, the method proposed in this study is promising for evaluating the workability of asphalt mixtures in compaction.

Innovative use of agro-waste cane bagasse ash and waste glass as cement replacement for green concrete. Cost analysis and carbon dioxide emissions

The individual incorporation of cane bagasse ash (CBA) and waste glass (WG) as substitutes of cement changes the properties of concrete. The aim of this study was to investigate the effects of using CBA with WG as cement substitutes on concrete properties. Different mixtures with cane bagasse ash and waste glass were prepared. The workability of concrete mixtures was evaluated by slump test immediately after casting, density and compressive strength were tested at 28 days. Additionally, cost analysis, carbon dioxide emissions and alkali-silica reaction were evaluated. Using cane bagasse ash with waste glass to produce concrete achieved better results for physical and mechanical properties than the concrete mixture using CBA or WG individually as a partial substitute for cement. The experimental results show that the incorporation of cane bagasse ash decreased the slump related with the low water absorption of CBA. Additionally, the hardened density of concrete incorporating waste glass and cane bagasse ash was lower than traditional concrete, however a definite trend was not observed. The combined use of CBA and WG has a positive contribution in achieving the highest compressive strength. The results exhibited that the incorporation of cane bagasse improved the compressive strength. The CBA15:WG5 mixture can increase 20% compressive strength in comparison with CBA0:WG20 mixture (without CBA). Additionally, CBA15:WG5 mixture have 8% lower cost than the traditional concrete CBA0:WG0. With the partial substitution of 20% of cement by ashes from cane bagasse ash and waste glass, it is possible to reduce the emission of CO2 for each m3 of material produced. On the other hand, the introduction of cane bagasse ash reduces the alkali silica reaction effect.

Comprehensive performance evaluation of high polymer-modified asphalt binders beyond linear viscoelastic rheological surrogates

• High polymer-modified (HP) binders exhibit superior performance compared to PMA. • LVE surrogates fail to predict failure properties of complex and modified binders. • HP binders displayed higher strain tolerance in DENT compared to conventional PMA. • HP binders tend to have lower cracking temperature in ABCD compared to typical PMA. • FTIR I PTDB and I PVDB indices can be used to detect potential polymer degradation. Polymer modification of asphalt binders has progressively become more common over recent decades. Styrene-Butadiene-Styrene (SBS) is a well-recognized elastomer that has been commonly used in asphalt pavements. SBS polymer specifically exhibits a chemical morphology of hard polystyrene segment tethered by soft polybutadiene segment. Concerns related to binder pump clogging and reduced mixture workability have limited the SBS copolymer content in polymer-modified asphalt (PMA) to around 3 %. This motivated researchers to develop a new SBS polymer structure by modifying the midblock structure to have much higher vinyl content. High polymer-modified (HP) binder technology allowed the use of SBS at higher levels of 7–8 %. Although several studies have highlighted the positive impacts of HP on asphalt binders, they were mostly limited to the linear viscoelastic (LVE) domain. Therefore, there is still a need for a comprehensive evaluation of HP binders that considers failure properties, which constituted the main motivation of this research. In this study, Multiple Stress Creep Recovery (MSCR), Double Edge Notched Tension (DENT) and Asphalt Binder Cracking Device (ABCD) test results showed that HP binders exhibited superior performance compared to PMA in terms of higher strain recovery and lower non-recoverable creep compliance at high temperatures (52–70 °C), higher strain tolerance at intermediate temperature (25 °C), and lower (colder) cracking temperatures at sub-zero temperatures. Additionally, chemical analysis showed minimal HP degradation potential compared to PMA.

The effect of granite filler on the rheological properties of fresh mixture of cement composites

This paper describes the use of granite filler produced during cutting, grinding and polishing of decorative stone. It mainly focuses on the consistency and workability of the fresh mixture in case of the cement substitution by granite filler. The comparative tests are carried out according to European standards dealing with fresh mortars and fresh concrete. The substitution of cement by granite filler is in multiples of 5% and 10% of the cement weight respectively. All results are also compared with a reference sample without granite filler. The results of flow table confirmed that workability and consistency decreased as the amount of granite filler increased. Altough this phenomena was also confirmed by spread flow test, specimens with 5 and 10% cement substitution had a better rheological properties. This phenomena was probably caused by improve of grain size curve of fresh mortar.

Reducing Compaction Temperature of Asphalt Mixtures by GNP Modification and Aggregate Packing Optimization.

Compaction of hot mix asphalt (HMA) requires high temperatures in the range of 125 to 145 C to ensure the fluidity of asphalt binder and, therefore, the workability of asphalt mixtures. The high temperatures are associated with high energy consumption, and higher NOx emissions, and can also accelerate the aging of asphalt binders. In previous research, the authors have developed two approaches for improving the compactability of asphalt mixtures: (1) addition of Graphite Nanoplatelets (GNPs), and (2) optimizing aggregate packing. This research explores the effects of these two approaches, and the combination of them, on reducing compaction temperatures while the production temperature is kept at the traditional levels. A reduction in compaction temperatures is desired for prolonging the paving window, extending the hauling distance, reducing the energy consumption for reheating, and for reducing the number of repairs and their negative environmental and safety effects, by improving the durability of the mixtures. A Superpave asphalt mixture was chosen as the control mixture. Three modified mixtures were designed, respectively, by (1) adding 6% GNP by the weight of binder, (2) optimizing aggregate packing, and (3) combining the two previous approaches. Gyratory compaction tests were performed on the four mixtures at two compaction temperatures: 135 C (the compaction temperature of the control mixture) and 95 C. A method was proposed based on the gyratory compaction to estimate the compaction temperature of the mixtures. The results show that all the three methods increase the compactability of mixtures and thus significantly reduce the compaction temperatures. Method 3 (combining GNP modification and aggregate packing optimization) has the most significant effect, followed by method 1 (GNP modification), and method 2 (aggregate packing optimization).

A new approach for proportioning self-consolidating earth paste (SCEP) using the Taguchi method

Rammed earth (RE) construction is an ancient sustainable construction method, which offers various economic and environmental advantages such as the availability of local materials. However, RE construction is a very time-consuming and labor-intensive process due to the consolidation required to achieve the targeted performance. The use of self-consolidating earth concrete (SCEC) can facilitate casting and speed the construction process. However, developing SCEC is challenging due to the presence of clay in earth, which can significantly hinder flowability. Optimizing the paste matrix of SCEC, namely self-consolidating earth paste (SCEP), is essential for achieving targeted workability performance of SCEC. In this study, the Taguchi method was employed to evaluate the effect of various mixture parameters, including clay and admixture type, cement content, and water-to-powder (W/P) and cement-to-clay (Ce/Cl) ratios to proportion SCEP mixtures. These parameters form different binder compositions with various Atterberg limits and water contents to investigate the compatibility and efficiency of different admixture types on the workability and compressive strength of their corresponding SCEP mixtures. Adequate clay dispersion was achieved using sodium hexametaphosphate (NaHMP) whereas polycarboxylate ether (PCE) was only efficient on cement particles. Sodium silicate (NaSil) did not contribute to dispersion of single-powder systems, while sodium polynaphtalene (PNS) and non-esterified polycarboxylate (NE-PC) showed compatibility with both clay and cement particles. Signal-to-noise ratio (S/N) analyses revealed that lower cement content and higher W/P and Ce/Cl resulted in lower admixture demand for targeted workability and marsh cone test (MCT) values. Regarding 1-day compressive strength, to facilitate the demolding process, PNS, PCE and NaSil showed the highest efficiency. As concluded from the analysis of variance (ANOVA), clay and admixture type had the highest contribution on workability, while cement content and W/P were significant on compressive strength. Several theoretical models were also established to predict the workability of SCEP mixtures from Atterberg limits of the corresponding soil. Finally, a new SCEP proportioning approach was proposed based on the established models and compressive strength contours to be used for different earth types.

Experimental Characterization and Multi-Factor Modelling to Achieve Desired Flow, Set and Strength of N-A-S-H Geopolymers.

The interaction between compositional ratios, namely, SiO2/Al2O3, Na2O/Al2O3, H2O/Na2O and the liquid-to-solid ratio, triggers mutual sacrifice between workability, setting time and strength for N-A-S-H geopolymers. The present study characterizes the mechanism underlying the effect of these compositional ratios and, in turn, develops guidelines for mixture design that requires a simultaneous and satisfactory delivery of these engineering properties. The experimental results show that an increase in either the SiO2/Al2O3, Na2O/Al2O3 or H2O/Na2O ratio raises the liquid-to-solid ratio, which in turn improves the workability of fresh mixtures. A continuous increase beyond 2.8 for the SiO2/Al2O3 ratio boosts its strength, but also significantly extends its final set. Lowering the Na2O/Al2O3 ratio from 1.3 to 0.75 raises the compressive strength significantly, while the shortest final set was seen at the median value, 1.0. A H2O/Na2O ratio of 9~10 yields the highest strength and the fastest final set simultaneously, due to the maximized degree of geopolymerization. Moreover, the accompanying sensitivity analysis indicates that the workability depends chiefly upon the H2O/Na2O ratio, the final setting time on the SiO2/Al2O3 ratio and, that the compressive strength relies on both of them. Also, this study proposes an optimal range of 2.8~3.6 for SiO2/Al2O3, 0.75~1.0 for Na2O/Al2O3 and 9~10 for H2O/Na2O to guarantee high strength, together with high flow and within the allowable final setting time. Furthermore, multi-factor predictive models are established with acceptable accuracy for practitioners to regulate oxide compositions in N-A-S-H geopolymers, which will guide future mixture design.

Investigation study of enhance the strength by using hybrid nano-composites on conventional cement concrete

Generally, incorporation of nano-particles with conventional concrete (CC) materials expands the bulk belongings of concrete by renovating molecular structures and permits the cement-based materials converted high-strength and durable products. The concentrated tensile possessions of the concrete confines its submissions where the flexural and tensile possessions of the concrete are major. In this steel and synthetic-fibres are expressively enhanced the tensile, toughness, impact resistance and energy-absorption capacity (EAC) of the concrete. Even yet the presence of fibre enhanced the tensile strength capacity (TSC) of the concrete, it hasn’t better the compressive strength capacity (CSC) of concrete suggestively. Therefore, it is very overbearing in growth of compressive strength of the concrete where the compressive tensile belongings to the concrete are major for its application. Investigation was carried to study the impact of nano-Al2O3, nano-Fe2O3, and their hybrid combinations on the setting time, microstructure, fresh, and strength properties of conventional cement concrete. Binding material of concrete mixtures was replaced by different nanoparticles, namely nano-Fe2O3 and nano-Al2O3, with four replacement rates (up to 4 %) that makes somewhat of change in building materials and gives energy to the building. The slump cone test was performed to assess the workability of concrete mixtures. Strength characteristics were evaluated, including the compressive, split tensile, and flexural strengths, for mixtures hardened after 7, 28, and 90 days. Moreover, the slump value of the mixture was decreased with an increase in the replacement rate of nanoparticles. However, slump values were within the acceptable workability and did not affect concrete compaction. However, the strength enhancement of the hybrid nano mixtures was relatively equal to that of the mixtures with only nano-Fe2O3 or nano-Al2O3. The test results revealed that nanoparticles can enhance the strength and microstructure properties of concrete.

Fresh, Mechanical, and Durability Behavior of Fly Ash-Based Self Compacted Geopolymer Concrete: Effect of Slag Content and Various Curing Conditions.

This investigation evaluates the influence of various curing conditions and slag inclusion on the fresh, mechanical, and durability properties of self-compacting geopolymer concrete (SCGC) based on fly ash (FA). Curing temperature and curing time have a vital role in the strength and microstructure of geopolymer concrete. Therefore, to begin the research, the impacts of different curing conditions (curing temperature and curing time) and slag content on the compressive strength of FA-based SCGC were examined to determine the optimum curing method. A series of four SCGC mixes with a fixed binder content (450 kg/m3) and an alkaline/binder ratio of 0.5 was designated to conduct a parametric study. FA was replaced with slag at four different substitution percentages, including 0%, 30%, 50%, and 100% of the total weight of the binder. The fresh properties of the produced SCGC specimens were investigated in terms of slump flow diameter, T50 flow time, and L-box height ratio. Additionally, the following mechanical properties of SCGC specimens were investigated: modulus of elasticity and fracture parameters. The water permeability and freezing–thawing resistance were studied to determine the durability behavior of SCGC. In this study, the optimum curing temperature was 85 °C for the duration of 24 h, which provided the maximum compressive strength. The results confirmed that adding slag affected the workability of SCGC mixtures. However, the mechanical characteristics, fracture parameters, and durability performance of SCGC were improved for slag-rich mixtures. When using 50% slag instead of FA, the percentage increase in compressive, flexural, elastic module, and fracture energy test values were about 100%, 43%, 58%, and 55%, respectively, whilst the percentage decrease in water permeability was 65% and the resistance to freeze–thaw test in terms of surface scaling was enhanced by 79%.

Variable speed mixing test and mixing flowability of asphalt mixtures

ABSTRACT To know the mixing flowability in theory and quantitatively evaluate the mixing workability of the asphalt mixture, a variable speed mixing (VSM) test device was developed in our laboratory. Different asphalt mixtures are tested by recording the mixing power under different mixing speeds (20∼50 r·min-1) and different mixing temperatures (130∼180 °C) to analyze the mixing flowability. Afterwards, the mixing workability index was defined from rheological parameters by establishing the mixing flow model. The experimental results indicate that the mixing flowability of asphalt mixtures obeys the linear Bingham’s visco-plastic model, which conducts two mixing rheological parameters including the mixing plastic limit and the mixing viscosity by the intercept and slope of the flow straight respectively. When the mixing temperature increases, the mixing viscosity decreases and the workability index increases, but the mixing plastic limit is not affected. With the increase of the nominal maximum particle size of asphalt mixtures, the mixing plastic limit increases and the workability index decreases, but the mixing viscosity is not affected. The asphalt becomes more viscous as the asphalt content increase, which leads to worse workability. The composition of aggregate determines the mixing plastic limit, and the viscosity of asphalt mortar determines the mixing viscosity.

Appraising bitumen coverage, workability, and production temperatures of warm asphalt-aggregate blends

ABSTRACT In this study, temperature-dependent high and low shear-rate workability indices (WIs) proposed from a developed workability tester, were employed respectively to determine suitable mixing and compaction temperatures for 12 warm mix blends. An automated procedure was also developed to determine the percentage of coated aggregates using a computer analysis code and set additional possible mixing temperatures for the blends. Two base binders, three representative warm asphalt technologies, and two gradations of basaltic aggregate were involved in the experimental work. Additionally, a framework of WI was introduced. The warm mixed blends were coated at lower temperatures compared to hot mixes. The workability of mixture is not controlled by binder viscosity only; rather it is dominated by the interwoven characteristics of asphalt-aggregate components. The proposed methodology helped in determination of reduced production temperatures for warm mix blends, and the reduction degree is affected by technology type and rate, and binder grade.

Experimental Investigation on the Effects of Coffee Husk Ash as Partial Replacement of Cement on Concrete Properties

The production of cement results in the depletion of natural resources and consumption of huge energy and CO2 emissions to the environment that cause global warming and climate change. To alleviate the problem, there is a growing interest of researchers to find an alternative material to partially cement by industrial and agricultural wastes. This research was therefore aimed to examine the potential of using coffee husk ash (CHA) as partial replacement for ordinary Portland cement (OPC) in C-25 concrete production. Concrete mixtures were prepared by partially replacing cement with CHA in different proportions (0%, 5%, 10%, and 20%) by weight with a constant w/c of 0.5. The consistency, setting time, workability, compressive strength, water absorption, sulphate attack, Fourier transform infrared (FTIR), and thermo gravimetric (TGA) tests were conducted on concrete samples. The test results revealed that the workability of mixtures showed a decreasing trend with an increase in the share of the CHA content in which the measured slump flow values ranged between 15 and 35 mm. Contrarily, the setting time of concrete mixtures showed an increasing trend with an increase in CHA content. The initial and final setting times were in the range of 67–126 minutes and 310–524 minutes, respectively, which is in the range of the standards. The compressive strength of concrete decreased with an increase in the share of the CHA, in which the results were measured in the range of 35.1–22.7 MPa for the 28th day sample with 5% and 20% of CHA, respectively. However, it increases as the curing days increase, whereas the water absorption of the concrete increases as the CHA increases but decreases as the curing days increase due to the porous nature of the CHA. From the study microstructure of concrete using Fourier transform infrared spectroscopy and thermogravimetric analysis, differential thermal analysis results show that the C-S-H gel would be from 950–1100 cm−1 wavenumber and at 500oC, and the CHA sample was decomposed and mass loss was observed at 500oC. In general, it was also observed that, from the compressive strength, the concrete satisfies its design strength up to 10% replacement level without compromising the performance of concrete.

Optimization of Self-Compacting Concrete Containing Blast-Furnace Slag Compositions

The paper deals with composition design of self-compacting concrete containing blast furnace granulated slag and polycarboxylate type superplasticizer in a wide range of concrete strength classes. Optimal superplasticizer content, cement, and blast furnace slag consumptions are obtained from the viewpoint of minimum water demand and water-cement ratio, maximum self-compacting concrete mixture workability retention, and concrete strength. A significant effect of joint influence of superplasticizer and blast furnace slag is demonstrated. The possibility of minimizing the cement consumption at optimal superplasticizer content and slag consumption of 100–120 kg/m3 is shown. Dependences for calculating SCC strength at 1, 7, and 28 days vs. the water-cement ratio are obtained. It is found that the nature of correlation dependences for SCC splitting and compression strengths when using the blast furnace slag and the superplasticizer is linear. Optimization of SCC compositions using mathematical programming enables to obtain compositions with a lowest possible cost while providing a set of specified parameters.

Comparative study on fresh, mechanical, microstructures properties and corrosion resistance of self compacted concrete incorporating nanoparticles extracted from industrial wastes under various curing conditions

Natural pozzolans or industrial wastes are commonly utilized in eco-friendly concrete as a partial replacement for ordinary Portland cement to eliminate carbon emissions and improve mechanical and durability characteristics. Although many experiments have been carried out to investigate the effects of natural pozzolans in concrete, there has been little research into the effects of nano waste glass (NWG) and nano waste ceramics (NWC) as cement replacement materials on the properties of self-compacted concrete (SCC). firstly, this study presents the effects of using NWG and NWC as cement replacement materials on the properties of SCC. This is to overcome the increased need of SCC for a larger amount of cement content, which leads to crack appearance. Secondly, this study aims to analyze the effect of self-curing (SC) using polyethylene glycol (PEG400) on SCC modified using various nanomaterials as a cement replacement (CRM) and compare the obtained results of this type of curing with air curing (AC) and normal curing (NC) to show the positive effect of SC on SCC properties. Several SCC mixes were created and tested utilizing nanoparticles with replacement percentages of cement ranging from 1–5%. SCC mixtures' fresh characteristics, mechanical properties, microstructure, and corrosion rates were investigated. Results show that the workability of SCC mixtures decreases in the case of SC compared to NC, but it remains within the acceptable limits of EFNARC-2005. By contrast, mechanical properties, microstructure, and corrosion resistance are improved as the percentages of NWC and NWG are increased, except for the 5% replacement ratio. Under SC, there was a significant improvement in SCC mixtures where compressive strength rose by 36% and 32% in NWG and NWC, respectively, and the corrosion rate decreased by 87% and 82% in NWG and NWC, respectively.