Effect of shale addition on properties of sintered coal fly ash

Shale can be used as a substitute for clay in sintered fly ash, due to the similar physical and chemical property to clay. In this paper, these characteristics of sintered fly ash with or without shale (binder) were investigated by physical property, X-ray diffraction and scanning electron microscopy. The results show that shale addition ranging from 30% to 50% (in weight) can be beneficial for properties of sintered products at temperature ranging from 950 to 1050 °C. However, a higher amount of shale easily caused significant bloating at 1100 °C. Considering energy saving and best performance, the sintering mix for shale and fly ash (50% in weight respectively, the same as below) fired at 1000 °C for 2 h was an optimal option. XRD results of the sintering mix show that intensity of hercynite increases with the increasing temperature, but intensity of quartz decreases on sintering. SEM confirms that addition of shale can improve microstructure and sintering of fly ash.     

Preparation and characterisation of fly ash based geopolymer mortars

Geopolymer mortars with varying levels of sand aggregate were prepared and their physical and mechanical properties studied. The geopolymer binder to sand aggregate weight ratio was varied from 9 to 1. Compressive strength and Young’s modulus of the fly ash based geopolymer paste were 60 MPa and 2.27 GPa and these values did not change significantly with addition of up to 50 wt.% sand aggregate. Geopolymer binder exhibited strong bonding to the sand aggregate. Increasing sand content without increasing the amount of alkaline activator resulted in a decreasing level of geopolymerisation within the binder system.     

Lightweight concretes of activated metakaolin-fly ash binders,with blast furnace slag aggregates

This work investigated geopolymeric lightweight concretes based on binders composed of metakaolin with 0% and 25% fly ash, activated with 15.2% of Na₂O using sodium silicate of modulus SiO₂/Na₂O = 1.2. Concretes of densities of 1200, 900 and 600 kg/m³ were obtained by aeration by adding aluminium powder, in some formulations lightweight aggregate of blast furnace slag was added at a ratio binder:aggregate 1:1; curing was carried out at 20 and 75 °C. The compressive and flexural strength development was monitored for up to 180 days. The strength diminished with the reduction of the density and high temperature curing accelerated strength development. The use of the slag had a positive effect on strength for 1200 kg/m³ concretes; reducing the amount of binder used. The thermal conductivity diminished from 1.65 to 0.47 W/mK for densities from 1800 to 600 kg/m³. The microstructures revealed dense cementitious matrices conformed of reaction products and unreacted metakaolin and fly ash. Energy dispersive spectroscopy and X-ray diffraction showed the formation of amorphous silicoaluminate reaction products.     

Use of power plant bottom ash as fine and coarse aggregates in high-strength concrete

In this study, experiments have been carried out to evaluate the utilization of bottom ash (by-product of power plant) as fine and coarse aggregates in high-strength concrete with compressive strength of 60–80 MPa. Firstly, the chemical and physical characteristics of bottom ash particles, such as chemical compositions, specific gravity and SEM images, were investigated. Further experiments were conducted by replacing fine and coarse bottom ash with normal sand and gravel varying in percentages (25%, 50%, 75%, and 100%). The effect of fine and coarse bottom ash on the flow characteristics and density of concrete mixture was investigated in the aspect of particle shapes and paste absorption of bottom ash. Mechanical properties, such as compressive strengths and modulus of elasticity and flexural strength of high-strength concrete with bottom ash were evaluated. It was found that the slump flow of fresh concrete was slightly decreased from 530 mm to 420 mm when coarse bottom ash was replaced 100% of normal coarse aggregates, while fine bottom ash did not affect the slump flow. Moreover, it also showed that both of fine and coarse bottom ash aggregates had more influence on the flexural strength than compressive strength.     

Interaction effects of crumb rubber modified asphalt binders

The application of crumb rubber in asphalt mixtures is intended to improve the binder properties by reducing the binder’s inherent temperature susceptibility. This research investigated the interaction effects of CRM binders as a function of various blending treatments in the laboratory. For this study, CRM binders were produced using seven blending times (5, 30, 60, 90, 120, 240, and 480 min), three blending temperatures (177, 200, and 223 °C), and four rubber contents (5%, 10%, 15%, and 20% by weight of asphalt binder). The results from this study showed that (1) The interaction time and interaction temperature for CRM binders were observed to have significant effect on the binder properties; (2) The longer time and higher temperature for interaction of CRM binders resulted in an increase in the high failure temperature and the viscosity. This is thought to be due to the increase in the rubber mass through binder absorption. However, this study found that the control binder of PG 64-22 had little change of the binder properties as a function of interaction conditions; (3) The CRM percentage influence is statistically significant on the viscosity and G^*/sin δ values. Also, the asphalt binder with higher CRM percentage showed a higher large molecular size (LMS) value, and the increase in CRM percentage is considered to result in the additional loss of the low molecular weight in the asphalt binder to the CRM.     

Influence of fly ash on strength and sorption characteristics of cold-bonded fly ash aggregate concrete

Cold-bonded fly ash aggregate concrete with fly ash as part of binder or fine aggregate facilitates high volume utilization of fly ash in concrete with minimum energy consumption. This paper investigates the influence of fly ash on strength and sorption behaviour of cold-bonded fly ash aggregate concrete due to partial replacement of cement and also as replacement material for sand. While cement replacement must be restricted based on the compressive strength requirement at desired age, replacement of sand with fly ash appears to be advantageous from early days onwards with higher enhancement in strength and higher utilization of fly ash in mixes of lower cement content. Microstructure of concrete was examined under BSEI mode. Replacement of sand with fly ash is effective in reducing water absorption and sorptivity attributable to the densification of both matrix and matrix–aggregate interfacial bond. Cold-bonded fly ash aggregate concrete with a cement content of 250 kg/m³, results in compressive strength of about 45 MPa, with a total inclusion of around 0.6 m³ of fly ash in unit volume of concrete.     

Applications of sewage sludge ash and nano-SiO2 to manufacture tile as construction material

In this study, various portions of potter’s clay and porcelain clay were replaced with incinerated sewage sludge ash (ISSA) to manufacture sludge ash tile specimens. We used these tiles to investigate the effect of introducing nano-SiO₂ particles as strengthening additives in the clay–ISSA materials. Percentages of ISSA in the porcelain or potter’s clay-based materials ranged from 0% to 50%, and fractions of nano-SiO₂ additives range from 0% to 3%. Tile specimens were manufactured from the different clay–ISSA–additive mixtures and sintered at kiln temperatures of 1000 °C and 1100 °C. Mechanical tests were performed to measure shrinkage, water absorption, abrasion, and bending strength. The sample microstructure was investigated using scanning electron microscopy (SEM). Chemical compositions of the tile specimens were characterized with X-ray diffraction. Results indicate that water absorption of porcelain and potter’s clay-based tiles was reduced when samples were fired at the higher kiln temperature, dropping to less than 12% in porcelain tiles at a kiln temperature of 1100 °C. Kiln temperature appeared to have less influence on the tiles made from potter’s clay. With the addition of nano-SiO₂ additive, the bending strengths of both types of tiles were increased, with the strengthening effect more pronounced in potter’s clay tiles when compared to porcelain clay tiles.     

Effect of polyester resin additive on the properties of asphalt binders and mixtures

The properties of AC-5 control asphalt binder, mixture containing the same asphalt were compared with the properties of AC-10 asphalt binder modified by 0.75%, 1%, 2%, and 3% of polyester resin (PR), mixture containing pure AC-10 and AC-10 modified by 0.75% of PR, respectively.Initial research was done to determine the physical properties of unmodified and PR modified asphalt binders. The AC-10 asphalt binder modified by 0.75% of PR had good results compared to AC-5 control asphalt binder and all other modified binders, and hence this modified binder as well as unmodified binders were used to prepare Marshall samples for Marshall stability and flow, indirect tensile stiffness modulus (ITSM), indirect tensile strength (ITS) and creep stiffness tests.The results of investigation indicate that AC-10 + 0.75% PR binder has better physical properties than AC-5 control asphalt binder and, at the same time, PR improves mechanical properties of asphalt mixture.     

Durability of cementing binders based on fly ash and other wastes

The paper deals with the cementitious binders produced by blending 60–70% fly ash with fluorogypsum, hydrated lime sludge, with and without Portland cement and chemical activator in different proportions. Data show that strength development of cementitious binders takes place through formation of ettringite, C–S–H and wollastonite compounds. The durability of these binder has been studied by its performance in water and by accelerated aging i.e. alternate wetting and drying as well as by heating and cooling cycles at temperatures in the range 27–50 °C. The results indicate Lawrence of strength of binder with the increasing cyclic studies at different temperatures. The maximum fall in compressive strength was noticed at 50 °C.     

Determining the specific gravities of coarse aggregates utilizing vacuum saturation approach

The current method of specific gravity and absorption of coarse aggregate testing is based on the AASHTO T 85 and ASTM C-127 standards. This approach involves the soaking of the coarse aggregate samples for 15h (AASHTO T 85) and 24 ± 4 h (ASTM C-127), and drying the aggregate to its saturated-surface dry (SSD) state with the aid of a dry absorbent cloth. The attainment of the SSD condition of the coarse aggregate is very subjective, and the total test duration makes it inconvenient for use in construction quality control and quality assurance testing (QC/QA).The objective of this paper is to determine the specific gravity and absorption of coarse aggregates using a new proposed approach utilizing vacuum saturation. In lieu of the conventional soaking period of 24 ± 4 h, this proposed research approach employs the use of 10, 20 and 30 min of vacuum saturation at 30 mm Hg (4.0 kPa) pressure. In this paper, the soaking time is 24 ± 4 h for all the AASHTO method. It is also believed that the 24 ± 4 h shall give better soaking and therefore more accurate test results would be achieved. Vacuum saturating the coarse aggregates aims at removing all the entrapped air within the sample mass, in addition to forcing water into the effective pores of the coarse aggregates. This method is applied to a wide range of coarse aggregates including trap rock, limestone, gravel, steel slag, crushed concrete, and the results are compared statistically with those of AASHTO T 85. Results from the experiments indicate that the vacuum saturation method can replace the AASHTO T 85 for coarse aggregate specific gravity testing at 10, 20 or 30 min of vacuum saturation. A significant finding was that the AASHTO T 85 underestimates the full absorption potential of highly absorptive aggregates when compared to this proposed vacuum saturation approach.     

Development of alpha plaster from phosphogypsum for cementitious binders

Efforts have been made to make high strength alpha plaster from phosphogypsum, a by-product of phosphoric acid industry. Phosphogypsum was autoclaved in slurry form (phosphogypsum 50% + water 50%, by wt.) in the laboratory at different steam pressures for different durations in presence of chemical admixtures. It was found that with small quantity of chemical admixture (sodium succinate/potassium citrate/sodium sulphate), alpha plaster of high strength can be produced. The optimum pressure and duration of autoclaving was found to be as 35 psi and 2.0 h, respectively. The alpha plaster was examined for making cementitious binders by admixing hydrated lime, fly ash, granulated blast furnace slag, marble dust and chemical additives with alpha plaster. Data showed that cementitious binder of compressive strength of 22.0 and 30 MPa (at 28 days of curing at 40° and 50 °C) and low water absorption was produced. DTA and SEM studies of the binder showed formation of CSH, ettringite and C₄AH₁₃ as main cementitious products to give strength.     

Modeling viscosity behavior of crumb rubber modified binders

Accurately predicting the viscous properties of crumb rubber modified (CRM) binders has proven difficult, especially as these properties tend to vary with changing crumb rubber concentrations and temperatures. This study explores the utilization of the statistical regression and neural network (NN) approaches in predicting the viscosity values of CRM binder at various temperatures (135 °C and greater). A total of 53 CRM binder combinations were prepared from two different rubber types (ambient and cryogenic), three different binder sources, four rubber concentrations (0%, 5%, 10%, and 15%), and five crumb rubber gradations (ADOT, SCDOT, 0.18 mm, 0.425 mm, and 0.85 mm). The results indicated that the regression model is easy to use and can be used for viscosity prediction, similarly NN-based models also provided accurate for predictions for the viscosity values of CRM binders regardless of rubber type and can easily be implemented in a spreadsheet. In addition, the developed NN model can be used to predict viscosity values of other types of CRM binders efficiently. Furthermore, the sensitivity analysis of input variables indicated that the changes of viscosity are significant as the changes of asphalt binder grade, test temperature, and rubber content. The results also show that these three independent variables are the most important factors in the developed NN models in comparison with other variables.     

Improving hydraulic properties of lime–rice husk ash (RHA) binders with metakaolin (MK)

To improve long-term hydraulic properties of binders from RHA and lime, 25–75% MK was added to RHA. Binders were formulated and properties were compared to that containing RHA or MK as only pozzolans. The lime–pozzolan ratio was 1:3. The properties tested after 7, 28 and 56 days were: absolute density and fineness of the binders, initial setting time, chemical and mineralogical composition of hydrated binders, flexural and compressive strengths and water absorption of mortars. The micrographs of the hardened binder pastes at 56 days permitted to evaluate the densification of different matrixes and the development of pores. From the results obtained, it was concluded that, MK increased the density of mixtures and decreased their grindability. The presence of MK decreased the SiO₂ content of binders and increases their Al₂O₃ and Fe₂O₃ contents. Calcium-silicate hydrates (CSH) gel and gehlenite (C₂ASH₈) were the main phases formed during the pozzolanic reaction in the presence of MK. No reduction in flexural and compressive strengths was observed after 28 days for binders containing MK. The mixture of 25% MK and 75% RHA which is recommended gave flexural and compressive strengths higher than binder with RHA or MK as the only pozzolan. Water absorption of mortars was less than 20%.     

Determination of the optimum conditions for tire rubber in asphalt concrete

The Taguchi method was used to determine optimum conditions for tire rubber in asphalt concrete with Marshall Test. The tire rubber in asphalt concrete was explored under different experimental parameters including tire rubber gradation (sieve #10–40), mixing temperature (155–175 °C), aggregate gradation (grad. 1–3), tire rubber ratio (0–10% by weight of asphalt), binder ratio (4–7% by weight of asphalt), compaction temperature (110–135 °C), and mixing time (5–30 min). The optimum conditions were obtained for tire rubber gradation (sieve #40), mixing temperature (155 °C), aggregate gradation (grad. 1), tire rubber ratio (10%), binder ratio (5.5%), compaction temperature (135 °C), mixing time (15 min).     

Laboratory investigation of the properties of asphalt concrete mixtures modified with TOP–SBS

Benefits of adding Tall oil pitch (TOP), Styrene-butadiene-styrene (SBS) and TOP + SBS to AC-10 in variant quantities to AC-10 were investigated. Initial research was done to determine the physical properties of asphalt cement and modifiers.Seven asphalt binder formulations were prepared with 8% of TOP; 8 + 3, 8 + 6 and 8 + 9% of TOP + SBS, respectively; 3, 6 and 9% of SBS by total weight of binder. After that, Marshall samples were prepared by using the modified and unmodified asphalt binders.Additionally, compression strength test were done in different conditions to determine water, heat and frost resistance of all Marshall samples.Fatigue life and plastic deformation tests for Marshall samples (for different asphalt mixtures: modified and unmodified) were carried out using PC controlled repeated load indirect tensile test equipment developed at Suleyman Demirel University by Tigdemir (SDU-Asphalt Tester).The results of investigation indicate that asphalt mixture modified by 8% TOP + 6% SBS gives the best results in the tests that were carried out in this study, so that, this modification increases physical and mechanical properties of asphalt binder.     

Properties of Portland cement-modified asphalt binder using Superpave tests

This study investigates the effect of cement additive on some properties of asphalt binder using Superpave testing methods. Six cement-to-asphalt (C/A) ratios were considered in the study: 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30 by volume of asphalt binder. The experimental tests that were conducted in the study included the Superpave rotational viscosity (RV) test and the dynamic shear rheometer (DSR) test. The RV test was conducted at the Superpave-specified high temperature of 135 °C that represents the average mixing and laydown temperature, and at seven different rotational speeds of 5, 10, 20, 30, 50, 60, and 100 rpm. On the other hand, the DSR test was conducted at four test temperatures of 58, 64, 70, and 76 °C; one lower and two higher than the Superpave high performance grade (PG) temperature of the asphalt binder used in the study (PG 64). The loading frequency used in the DSR test was 10 rad/s (1.59 Hz) as specified by the Superpave system. Results of the study showed that the addition of Portland cement to asphalt binders increased the rotational viscosity (RV) of asphalt binders at 135 °C and different rotational speeds. The C/A ratio of 0.15 was found to be the optimum ratio that achieved a balanced increase in the rotational viscosity and the value of the DSR G^*/sin δ rutting parameter of asphalt binders. The C/A ratio had insignificant effects on the Newtonian behavior, the phase angle (δ), and the elastic behavior of asphalt binders. The increase in C/A ratio increased the stiffness of asphalt binders represented by the complex shear modulus (G^*) value. The increase in the C/A ratio improved the rutting parameter, G^*/sin δ value, at all temperatures. The increase in C/A ratio improved the Superpave high PG temperature (the high temperature at which the asphalt binder passed the Superpave criteria for G^*/sin δ value). It was also shown that the best function that described the relationship between each of RV, G^*, and G^*/sin δ and the C/A ratio was the exponential function with high coefficient of determination (R²).     

Effect of crumb rubber characteristics on crumb rubber modified (CRM) binder viscosity

Asphalt binder viscosity is of great importance during the production process of hot mix asphalt mixture as typically asphalt plants will store binders between 149 °C and 177 °C. SHRP guidelines state that asphalt binder viscosity must not exceed 3 Pa s. Therefore, given the documented increases in asphalt viscosity when modified with crumb rubber modifier (CRM) it is necessary to produce asphalt binder that fulfills the SHRP criteria while not exceeding plant mixing and storing requirements. This paper reports the results of an investigation of the importance of CRM properties on viscosity of CRM binder. Two binder sources were modified at four concentration levels using four different crumb rubber sources; the viscosities of the produced binders were evaluated by AASHTO T 316. Crumb rubber properties were evaluated by elemental analysis using a scanning electron microscope (SEM) and by determination of glass transition temperature (T_g) using a differential scanning calorimeter (DSC). In general, results indicate that processing procedure and tire type plays an important role in the determination of CRM binder viscosity.     

Properties of compressed lateritic soil stabilized with a burnt clay–lime binder: Effect of mixture components

In this study, a pozzolanic binder containing lime and a common thermally activated kaolinitic clay, at 750 °C, was formulated. The chemical, mineralogical and pozzolanic properties of raw materials were determined. The percentage of lime in the binder varies between 20% and 30%. The binder was used as a stabilizer in compressed lateritic soil in which water–solid (laterite and binder) and laterite–binder ratios vary, respectively, from 0.12 to 0.20 and 4 to 9. Sodium hydroxide (NaOH) was added as a chemical activator in the mixture. The NaOH–binder ratio varies from 0.02 to 0.04. The average effect of each component of the mixture on compressive strength, water absorption and apparent density of compressed laterite after 7 or 28 days of conservation at 40 ± 1 °C in an atmosphere saturated with water vapour was evaluated in a screening design of the “design in graeco – latin squares” type. It was observed that water–solid and laterite–binder ratios are the factors that influence more the properties of the products. Compressive strength increases up to a water–solid ratio of 0.16 then decreases for higher ratios. Compressive strength decreases with the increase of laterite–binder ratio. Water absorption decreases with the increase of water–solid ratio up to 0.16 then sharply increases for higher ratios. However, water absorption decreases slightly with the increase in the lime content of the binder and sodium hydroxide–binder ratio. The maximum apparent density is observed at water–solid ratio of 0.16. It increases when sodium hydroxide–binder and laterite–binder ratios increase.     

Aging analysis of rubberized asphalt binders and mixes using gel permeation chromatography

This study was initiated to investigate the aging characteristics of binders due to the reaction with the crumb rubber. For this laboratory study, the crumb rubber modified (CRM) and control binders were aged using an oven aging method. Also, asphalt mixtures with CRM or control binders were made and subjected to short-term and long-term aging treatments. The properties of these aged binders were evaluated using gel permeation chromatography (GPC) test procedures. The results from this study showed that: (1) the higher CRM percentage resulted in the higher large molecular size (LMS) value of asphalt binder under the binder aging conditions, and the rate of increase in the LMS value was found to have a relation to the CRM percentage. The asphalt binders with higher CRM percentages (15% and 20%) had a trend the LMS values decrease after a certain level. This finding is thought to be related to the required time for the rubber to be fully digested; (2) after subjecting to the long-term oven aging, the asphalt mixtures with the control and CRM modified binders were found to have statistically insignificant differences in aging level, measured using the LMS values. The very thin film thickness of binder in asphalt mixture and the aging temperature of 100 °C insufficient to enable a reaction were considered to be the main reasons that no differences were observed from the standpoint of the aging effect.     

Influence of mineral additions on the performance of 100% recycled aggregate concrete

A judicious use of resources, by using by-products and waste materials, and a lower environmental impact, by reducing carbon dioxide emission and virgin aggregate extraction, allow to approach sustainable building development. Recycled aggregate concrete (RAC) containing supplementary cementitious materials (SCM), if satisfactory concrete properties are achieved, can be an example of such sustainable construction materials.In this work concrete specimens were manufactured by completely replacing fine and coarse aggregates with recycled aggregates from a rubble recycling plant. Also RAC with fly ash (RA + FA) or silica fume (RA + SF) were studied.Concrete properties were evaluated by means of compressive strength and modulus of elasticity in the first experimental part. In the second experimental part, compressive and tensile splitting strength, dynamic modulus of elasticity, drying shrinkage, reinforcing bond strength, carbonation, chloride penetration were studied. Satisfactory concrete properties can be developed with recycled fine and coarse aggregates with proper selection and proportioning of the concrete materials.