·This study investigated the limestone powder LS particle size effect on the heat of hydration of Portland cement PC and high calcium fly ash FA systems The LS used has a maximum particle size of 5 and 20 μm respectively Isothermal calorimetry was used to measure the heat evolution during the hydration process of the cement and PC FA pastes The results
·Recently alkali activated high calcium fly ash FA has been investigated for use as a repair material due to its advantage of reasonable setting time and hardening [8] It has also been shown that alkali activated high calcium FA could be used as an alternative commercial repair material with relatively high 28 day compressive and shear bond strengths comparable
·The effects of sodium hydroxide NaOH concentration on setting time compressive strength and electrical properties at the frequencies of 100 Hz 10 MHz of high calcium fly ash geopolymer pastes were NaOH concentrations 8 10 12 15 and 18 molar were liquid to ash ratio of sodium silicate to sodium hydroxide ratio
·Replacement of Portland cement PC by fly ash FA is currently limited to 15 30% by mass mainly due to low early age strength development of concrete This research uses calcium formate Ca HCO2 2; CF as an admixture to high volume FA HVFA composites to improve its strength properties HVFA represents 60 70% of cement replaced by FA and
· Materials and Equipment The brown coal fly ash was supplied from Germany; it was treated with water homogenized and ground by the manufacturer The chemical composition of the ash as determined by Bruker Axs S4 Pioneer X ray fluorescence instrument is given in Table ash does not comply with either Class F or class C according to ASTM
·Sulfate attack is one of the major threats to concrete structures In this study strength degradation by magnesium sulfate MgSO 4 reaction of low calcium fly ash geopolymer hemp shiv concrete was carefully hemp shiv was pretreated with AlCl 3 KOH to prevent water and water curing were also performed to elucidate
·The effect of replacing cement with high calcium fly ash HCFA represented by 4 fractions Fr1 Fr4 from 4 electrostatic precipitators of the ash collectors at the Krasnoyarsk TPP 2 on the
·The fly ash pozzolanic properties render it beneficial for the replacement of cement in concrete Nonavinakere and Reed 1995 Yao et al 2015 The FA silica reacts with calcium hydroxide released by CaO hydration producing Ca 2
·Keywords Concrete; High calcium fly ash; Modeling; Reaction 1 Introduction High calcium fly ash FH is the combustion residue in electric power plants burning lignite or sub bituminous coal It essentially consists of aluminosilicate glass mod ified by the presence of large amounts of calcium and magnesium It can be categorized as
·Fly ash is an aluminosilicate material that is widely used for the preparation of geopolymer composites especially low calcium fly ash LCF Nath and Sarker 2017 In fact one of the most important benefits of using fly ash for geopolymer synthesis is its easy availability compared to other source materials Mehta and Siddique 2017 In Thailand most fly ash is
·There has been significant recent research into High Volume Fly Ash HVFA concrete to enable the utilization of fly ash and to reduce CO 2 emission by reducing cement demand This comprehensive review summarizes up to date literature on HVFA concrete with more than 50% of cement replacement using ASTM Class F low calcium fly ash
·It is worth noting that calcium nitrite presence in this concrete has positive effect on the compressive strength; with content of 5 L/m 3 and 10 L/m 3 of CNI the latter is approximately 25% in
·Replacement of Portland cement PC by fly ash FA is currently limited to 15 30% by mass mainly due to low early age strength development of concrete This research uses calcium formate Ca HCO2 2; CF as an admixture to high volume FA HVFA composites to improve its strength properties HVFA represents 60 70% of cement replaced by FA and
·Na2SiO3/KOH weight ratio o n the compressive strength of fly ash based geopolymer concrete were investigated T he obtained results showed that using NaOH provided greater 3 and 7 day
·Geopolymer concretes have emerged as an alternative to traditional Portland cement concretes with high strength good durability well corrosion performance and high temperature resistance and being a sustainable and environmentally friendly material In this study a comprehensive microstructural analysis of low calcium fly ash based geopolymer
·This article presents the effect of adding nano SiO2 and nano Al2O3 on the properties of high calcium fly ash geopolymer pastes Nano particles were added to fly ash at the dosages of 0% 1% 2%
·In this study bentonite a naturally occurring pozzolana was incorporated as a partial replacement up to 20% for high calcium fly ash HCFA based geopolymeric natural aggregate concrete GNAC
·Environmental considerations and technical benefits have directed research towards reducing cement clinker content in concrete and one of the best ways to do this is to replace cement with supplementary cementitious materials High calcium fly ash ladle furnace slag and limestone filler were investigated as supplementary cementitious materials in cement
·High volume fly ash concrete is covered in a general way in CHAPTER 4—EFFECTS OF FLY ASH ON CONCRETE p 18 —Effects on properties of fresh concrete p 18 modern concrete fly ash combines with calcium hydroxide Ca OH 2 also known as portlandite which predominately
·This study investigated the mechanical properties of alkali activated fly ash AAF mortars containing superabsorbent polymers SAPs and polypropylene PP fibers before and after exposure to elevated temperatures AAF mortars were synthesized using sodium silicate and high calcium fly ash as the solid activator and aluminosilicate source respectively
·To expand the application range of magnesium oxysulfate cement MOSC and the utilization of fly ash the water resistance of MOSC mixed with low calcium fly ash L FA or high calcium fly ash H FA was studied The softening coefficients and volume stability were tested to evaluate the water resistance of MOSC
·Effect of calcium formate on the compressive strength and hydration process of cement composite containing fly ash and slag Effects of calcium formate on early age strength and microstructure of high volume fly ash cement systems Mag Concr Res 2 2021 pp 1 31 Google Scholar [19]
·The total heat evolved after 48 hours of hydration was 145 kJ/kg for the cement paste containing high calcium fly ash and 69 kJ/kg for the cement paste containing low calcium fly ash As may be seen from the SEM results there are considerable differences in morphology of the hydration products in the high and low calcium fly ash pastes
