scholarly journals Effect of alkali content and slag content on the fresh and hardened properties of air-cured alkali activated mortar containing fly ash

2021 ◽  
Author(s):  
Thushara Raju ◽  
Namitha S ◽  
Muhammed Nabil K ◽  
Mohammed Rafeeque N. V ◽  
Reshma Sundhar ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Construction Material ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Alkali Content ◽  
Hardened Properties ◽  
Alkali Activated ◽  
Slag Content

Alkali Activated Material (AAM) is introduced as a pioneering construction material in the construction diligence to trim down the utilization of Ordinary Portland Cement (OPC) and to curtail the amount of carbon dioxide released during the production of OPC. Modestly refined industrial by products or natural materials rich in alumino silicates are the binding agents used in AAM. Generally, heat curing is needed for the alkali activated mortar to achieve the required hardened properties and this difficulty can be overcome by adding slag to the mix. In this experimental analysis, the alkali activated mortar mixes with different proportions of glassy granulated slag and Class F fly ash were prepared without the usage of superplasticizers, with alkali to binder (a/b) ratios of 0.7, 0.8 and 0.9. The rheological characteristics of mortar were studied using flow table apparatus and hardened properties were studied using compressive strength test and ultrasonic pulse velocity (UPV) test by testing cylindrical specimens of size 25 mm diameter and 50 mm height. The mortar specimens were air-cured, and the compressive strength and UPV test were conducted after 3 and 7 days. The test results showed that due to the presence of higher alkali content and the decrease in slag content, the workability of alkali activated mortar was improved, but the measure of strength decreased. The mix with 100% slag and a/b ratio of 0.8 had the best UPV value, indicating its quality among the various mortar mixes studied. This study portrays the significance of optimising the alkali and slag content in tailor making an alkali activated mortar system with good hardened properties.

scholarly journals Characteristics of Preplaced Aggregate Concrete Fabricated with Alkali-Activated Slag/Fly Ash Cements

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 591
Author(s):  
Salman Siddique ◽  
Hyeju Kim ◽  
Hyemin Son ◽  
Jeong Gook Jang
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Water Absorption ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Cement Grout ◽  
Aggregate Concrete ◽  
Alkali Activated ◽  
Alkali Activated Cement

This study assesses the characteristics of preplaced aggregate concrete prepared with alkali-activated cement grout as an adhesive binder. Various binary blends of slag and fly ash without fine aggregate as a filler material were considered along with different solution-to-solid ratios. The properties of fresh and hardened grout along with the properties of hardened preplaced concrete were investigated, as were the compressive strength, ultrasonic pulse velocity, density, water absorption and total voids of the preplaced concrete. The results indicated that alkali-activated cement grout has better flowability characteristics and compressive strength than conventional cement grout. As a result, the mechanical performance of the preplaced aggregate concrete was significantly improved. The results pertaining to the water absorption and porosity revealed that the alkali-activated preplaced aggregate concrete is more resistant to water permeation. The filling capacity based on the ultrasonic pulse velocity value is discussed to comment on the wrapping ability of alkali-activated cement grout.

scholarly journals Empirical Investigation on Compressive Strength of Geopolymer and Conventional Concretes by Nondestructive Method

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
B. Ravali ◽  
K. Bala Gopi Krishna ◽  
D. Ravi Kanth ◽  
K. J. Brahma Chari ◽  
S. Venkatesa Prabhu ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Nondestructive Method ◽  
Geopolymer Concrete ◽  
River Sand ◽  
Rebound Hammer ◽  
Compressive Strength Of Concrete

Need of construction is increasing due to increase in population growth rate. The geopolymer concrete is eco-friendly than ordinary concrete. Current experimental investigation was conducted on ordinary and geopolymer concrete using nondestructive testing (NDT) tests like ultrasonic pulse velocity (UPV) test and rebound hammer (RH) test. Cube specimens of dimensions 150 mm × 150 mm × 150 mm are used to conduct these tests at 7, 14, and 28 days. Proportions considered for concrete are cement-fly ash-river sand (100-0-100% and 60-40-100%), cement-fly ash-robo sand (100-0-100% and 60-40-100%) whereas geopolymer concrete fly ash-metakaolin is taken in proportions of 100-0%, 60-40%, and 50-50%. Alkaline activators (sodium hydroxide and sodium silicate with molarity 12M) were used in preparing geopolymer concrete. The major objective of the current study is to obtain relation between compressive strength of concrete and UPV values.

An Ultrasonic Pulse Velocity Test on Fly-Ash Based Geopolymer Concrete in Frequency Domains

2014 ◽  
Vol 700 ◽  
pp. 310-313 ◽  
Author(s):  
Jee Sang Kim ◽  
Tae Hong Kim
Keyword(s):  
Compressive Strength ◽  
Construction Material ◽  
High Strength ◽  
Ultrasonic Pulse Velocity ◽  
Peak Frequency ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
P Wave ◽  
Geopolymer Concrete ◽  
Existing Structures

The Non-Destructive Test techniques on concrete, which can assess the properties of materials without damages, have been developed as the deteriorations of existing structures increase. Among them, the ultrasonic pulse velocity (USPV) method is widely used because it can investigate the states of one material for a long time and repeatedly. However, there have been few researches on the NDT application to geopolymer concrete which is environment friendly construction material without any cement. This paper investigates the variations of ultrasonic pulse velocity and peak frequency of geopolymer concrete under monotonically increasing loads to assess the material conditions with various compressive strength levels by measuring P-wave signals. The pulse velocities and peak frequencies were higher in high strength geopolymer concrete specimens. There are not explicit relations between strength levels and peak frequencies but the peak frequencies are strongly influenced by the applied stress levels. In addition, a predicting equation for compressive strength of geopolymer concrete is derived based on experimental data in similar form for normal concrete.

scholarly journals Performance of Fly Ash Geopolymer Concrete Incorporating Bamboo Ash at Elevated Temperature

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3404 ◽  
Author(s):  
Ishak ◽  
Lee ◽  
Singh ◽  
Ariffin ◽  
Lim ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Control Sample ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Air Cooling ◽  
Geopolymer Concrete ◽  
Water Cooling ◽  
Control Samples

This paper presents the experimental results on the behavior of fly ash geopolymer concrete incorporating bamboo ash on the desired temperature (200 °C to 800 °C). Different amounts of bamboo ash were investigated and fly ash geopolymer concrete was considered as the control sample. The geopolymer was synthesized with sodium hydroxide and sodium silicate solutions. Ultrasonic pulse velocity, weight loss, and residual compressive strength were determined, and all samples were tested with two different cooling approaches i.e., an air-cooling (AC) and water-cooling (WC) regime. Results from these tests show that with the addition of 5% bamboo ash in fly ash, geopolymer exhibited a 5 MPa (53%) and 5.65 MPa (66%) improvement in residual strength, as well as 940 m/s (76%) and 727 m/s (53%) greater ultrasonic pulse velocity in AC and WC, respectively, at 800 °C when compared with control samples. Thus, bamboo ash can be one of the alternatives to geopolymer concrete when it faces exposure to high temperatures.

scholarly journals Effect of the Sodium Silicate Modulus and Slag Content on Fresh and Hardened Properties of Alkali-Activated Fly Ash/Slag

Minerals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 15 ◽  
Author(s):  
Xiaowei Ouyang ◽  
Yuwei Ma ◽  
Ziyang Liu ◽  
Jianjun Liang ◽  
Guang Ye
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Pore Structure ◽  
Heat Release ◽  
Setting Time ◽  
Heat Evolution ◽  
Reaction Products ◽  
Hardened Properties ◽  
Alkali Activated ◽  
Slag Content

This paper presents the results of an experimental study performed to investigate the effect of activator modulus (SiO2/Na2O) and slag addition on the fresh and hardened properties of alkali-activated fly ash/slag (AAFS) pastes. Four activator moduli (SiO2/Na2O), i.e., 0.0, 1.0, 1.5, and 2.0, and five slag-to-binder ratios, i.e., 0, 0.3, 0.5, 0.7, 1.0, were used to prepare AAFS mixtures. The setting time, flowability, heat evolution, compressive strength, microstructure, and reaction products of AAFS pastes were studied. The results showed that the activator modulus and slag content had a combined effect on the setting behavior and workability of AAFS mixtures. Both the activator modulus and slag content affected the types of reaction products formed in AAFS. The coexistence of N–A–S–H gel and C–A–S–H gel was identified in AAFS activated with high pH but low SiO2 content (low modulus). C–A–S–H gel had a higher space-filling ability than N–A–S–H gel. Thus, AAFS with higher slag content had a finer pore structure and higher heat release (degree of reaction), corresponding to a higher compressive strength. The dissolution of slag was more pronounced when NaOH (modulus of 0.0) was applied as the activator. The use of Na2SiO3 as activator significantly refined the pores in AAFS by incorporating soluble Si in the activator, while further increasing the modulus from 1.5 to 2.0 prohibited the reaction process of AAFS, resulting in a lower heat release, coarser pore structure, and reduced compressive strength. Therefore, in view of the strength and microstructure, the optimum modulus is 1.5.

Effect of Treated Sago Pith Waste Ash and Silica Fume to the Mechanical Properties of Fly Ash-Based Geopolymer Brick

2021 ◽  
Vol 879 ◽  
pp. 100-114
Author(s):  
Izwan B. Johari ◽  
Md Azlin Md Said ◽  
Mohd Amirul B. Mohd Snin ◽  
Nur Farah Aqilah Bt. Ayob ◽  
Nur Syafiqah Bt. Jamaluddin ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Silica Fume ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Partial Replacement ◽  
Rebound Hammer ◽  
Compressive Strength Test ◽  
Sago Pith Waste

This paper investigates the effect of partial replacement of fly ash with sago pith waste ash and silica fume in fabricating the geopolymer mortar concrete. The mixtures of geopolymer mortar concrete were prepared by replacing sago pith waste ash and silica fume at 5% of total weight of fly ash. There were six specimens of geopolymer mortar cubes and bricks fabricated in this study. The specimens are tested with compressive strength test, rebound hammer test and ultrasonic pulse velocity test. The results from the tests are compared with some existing published works as to clarify the effect of replacing the fly ash with sago waste and silica fume on the strength of concrete. Comparisons had been made and concluded that the molarity of alkaline solution, Al3O2 and CaO influenced the development of compressive strength along the curing time of fly ash based geopolymer concrete.

The Effect of Chloride Environment on Mechanical Properties Geopolymer Binder with Fly Ash

2013 ◽  
Vol 594-595 ◽  
pp. 648-655 ◽  
Author(s):  
Muhammad Sigit Darmawan ◽  
Ridho Bayuaji ◽  
Boedi Wibowo ◽  
Nur Ahmad Husin ◽  
Srie Subekti
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Fly Ash ◽  
Design Method ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
National Standard ◽  
Vacuum Saturation ◽  
Chloride Environment

This study is conducted to determine the effect of five variables on mechanical properties of geopolymer binders. These five variables are chloride environment, NaOH molarity, Na2SiO3/NaOH ratio, fly ash/alkaline activator (FA/AA) ratio and superplasticizer (SP) addition. The mechanical properties considered are compressive strength, porosity and density. Taguchi experimental design method is used to compile the binder composition of geopolymer to achieve the maximum compressive strength. Specimens binder used is a cylinder with 25 mm diameter and 50 mm height. Compressive strength test is performed at 28 days using SNI 03-6825-2002 (Indonesian National Standard) and porosity of the binder is determined using vacuum saturation apparatus similar to that developed by RILEM. The density of the binder is measured using Ultrasonic Pulse Velocity (UPV). This study concludes that the chloride environment has a beneficial effect on the compressive strength of the binder. In addition, the FA/AA ratio and NaOH molarity give a significant effect on the compressive strength of geopolymer binders.

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