·This research aimed to present the improvement of the cementitious material in high volume fly ash using only one alkali activator Fly ash was used as a partial replacement for Portland cement type I varying from 0 to 60% by weight of the binder Concentrations of NaOH varying from to molar were used as alkali activator Paste properties and mortar
·1 Introduction Alkali activated materials AAMs or geopolymers are potential sustainable cementitious alternatives to ordinary Portland cement OPC [1] AAMs are produced with precursors such as fly ash FA ground granulated blast furnace slag GGBFS slag and metakaolin MK and are activated with alkaline activators at room temperature [3] [4] [5]
· Water Soluble and Available Alkalis The water soluble ASTM C114 and available ASTM C311 alkali results for cementing materials are presented in Fig data shown in Fig 2 are the percent of the total alkalis Na 2 O e = Na 2 O × K 2 O of cementing materials determined using x ray fluorescence In all cases less than 50% of the
·The use of a fly ash with a low or high calcium content will depend on the cement s service conditions Low calcium fly ash embodies a better response in durability while a high content is equivalent to a better mechanical performance [3]
·construction use of fly ash in the production of concrete products and specialty concretes and recommended procedures for quality control High volume fly ash concrete is covered in a general way in this report; readers can consult ACI for more information Keywords alkali aggregate reaction; controlled low strength material
·The high alkaline content of the fly ash samples does not allow the leaching agent used in the acetate buffer solution method to completely consume the alkaline material in the fly ash resulting in the strong alkalinity of the fly ash leachates but it is still necessary to control the risk of fly ash landfill at source Table 3
·In this paper an investigation related to the rheological behaviour of alkali activated fly ash pastes AAFA is described Those pastes were prepared by mixing the fly ash with an alkaline dissolution containing 85% of a M NaOH solution and 15% of waterglass and adding some commercial chemical admixtures usually used in the Portland cement concrete
·Quality assurance and quality control testing of ash at the source must ensure that the fly ash used maintains a uniform carbon content LOI to prevent unacceptable fluctuations in entrained air New technologies and procedures to address unburned carbon in fly ash are described in Chapter 10
·Identical set of tests were conducted on parallel HPCM specimens containing Class F fly ash as a cement replacement material and significant differences in results were observed when compared with pure Portland cement mixtures At low alkali content % Na 2 O eq the use of FA increased the amount of charge passed by 29% At high
·From the calorimetrical point of view the effects of solution 4 on the fly ash are almost identical to the effects produced by solution 3 The effect of the activator fly ash ratio is not significant the differences in the calorimetry curves are hardly perceptible when that ratio is or ; however calorimetry is very sensitive to the effect of temperature
·Quality assurance and quality control testing of ash at the source must ensure that the fly ash used maintains a uniform carbon content LOI to prevent unacceptable fluctuations in entrained air New technologies and procedures to address unburned carbon in fly ash are described in Chapter 10
·The utilization of fly ash as a waste product of coal combustion is currently limited to being a supplementary cementitious material Fly ash integrates well with cement demonstrating favorable qualities in concrete such as good workability high ultimate strength and durability However the use of fly ash in very high proportions has not been extensively
·The use of fly ash with or without alkali activation to replace cement cannot always guarantee the sustainability enhancement of construction LCA and CBA are often used to evaluate the recycling of fly ash in terms of economic benefits and environmental influences Hossain et al 2017; Wang et al 2016; Yang et al 2017
·The use of a fly ash with a low or high calcium content will depend on the cement s service conditions Low calcium fly ash embodies a better response in durability while a high content is equivalent to a better mechanical performance [3]
·The results of this study show that the efficacy of fly ash in controlling expansion due to ASR varies within a wide range For instance concrete containing 25% fly ash shows 2 year expansion values ranging from % to % Table 2 However all types of ash at all the RLs reduced expansion compared to the control concrete without fly ash
·Alkali activated mixtures of fly ash and slag and slag were prepared using 3 M NaOH activating solution The binder phase of the mixtures consisted of fly ash and slag A baseline mixture was prepared with fly ash and slag in a mass proportion equal to 72 28 and the activating solution to binder ratio by mass equal to
·In this paper an investigation related to the rheological behaviour of alkali activated fly ash pastes AAFA is described Those pastes were prepared by mixing the fly ash with an alkaline dissolution containing 85% of a M NaOH solution and 15% of waterglass and adding some commercial chemical admixtures usually used in the Portland cement concrete
·To accomplish environmental sustainability and reduce carbon emission the construction industry needs to adopt waste industrial by products as construction materials To resolve this issue this study investigated the strength and durability performance of alkali activated concrete AAC using industrial waste products such as ground granulated blast
·To examine the utilization of fly ash and GGBS as a cement substitute it is necessary to study the standard consistency and setting time of geopolymer paste and workability as well as compressive strength of alkali activated fly ash and slag based geopolymer concrete The method used to determine these tests was the same as used for cement
·Low calcium fly ash based geopolymer concrete is generally reported to be less vulnerable to alkali silica reaction ASR than conventional ordinary Portland cement concrete However the lack of understanding of pore solution composition of the low calcium fly ash based geopolymer limits the investigation of the underlying mechanisms for the low ASR
·The results of this research show that high alkali biofuel fly ash BFA had a significant influence on the mechanical characteristics microstructure porosity freezing thawing cycle resistance and ASR resistance of cementitious materials Different amounts of BFA varying from 0 to 30% were used as a substitute for cement in concrete mixes The impact of
·KEYWORDS alkali silica reaction alkali activated fly ash pore solution analysis 1 INTRODUCTION The objective of this research was to investigate the risks and early signs of alkali silica reaction ASR in class F alkali activated fly ash AAFA concretes ASR is a leading cause of deterioration in
·This paper reports the influence of activator type and concentration on the rheological properties of alkali activated fly ash suspensions A thorough investigation of the rheological influences yield stress and plastic viscosity of several activator parameters including i the cation type and concentration of alkali hydroxide and ii the alkali to binder
·All content in this area was uploaded by Mohammad Jamshidi Avanaki on Mar 27 2021 Keywords Geopolymer Concrete Fly Ash Alkaline Activator Compressive Strength NaOH
