Modification Effects of Nano-SiO2 on Early Compressive Strength and Hydration Characteristics of High-Volume Fly Ash Concrete

2019 ◽  
Vol 31 (6) ◽  
pp. 04019057 ◽  
Author(s):  
Jinfeng Sun ◽  
Xiaodong Shen ◽  
Gang Tan ◽  
Jennifer E. Tanner
Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 243 ◽  
Author(s):  
Mohamed H. Mussa ◽  
Ahmed M. Abdulhadi ◽  
Imad Shakir Abbood ◽  
Azrul A. Mutalib ◽  
Zaher Mundher Yaseen

The dynamic behaviour of high-volume fly ash concrete with nano-silica (HVFANS) and polypropylene fibres at curing ages of 7 to 90 days was determined by using a split Hopkinson pressure bar (SHPB) machine. At each curing age, the concrete samples were laboratory tested at different temperatures conditions under strain rates reached up to 101.42 s−1. At room temperature, the results indicated that the dynamic compressive strength of plain concrete (PC) was slightly higher than HVFANS concrete at early curing ages of 7 and 28 days, however, a considerable improvement in the strength of HVFANS concrete was noted at a curing age of 90 days and recorded greater values than PC owing to the increase of fly ash reactivity. At elevated temperatures, the HVFANS concrete revealed a superior behaviour than PC even at early ages in terms of dynamic compressive strength, critical strain, damage and toughness due to increase of nano-silica (NS) activity during the heating process. Furthermore, equations were suggested to estimate the dynamic increase factor (DIF) of both concretes under the investigated factors.


2011 ◽  
Vol 261-263 ◽  
pp. 333-337
Author(s):  
Juan Hong Liu ◽  
Fang Fang Hou ◽  
Shao Min Song ◽  
Bo Ya Jia

In this article, the effects of compressive strength and carbonation depth of HCSA mixing amount on high volume fly ash concrete have been investigated. Besides, the effects of compressive strength and carbonation depth of the fly ash amount on HCSA expansive concrete have been also analyzed. The results show that proper HCSA mixing amount can improve the compressive strength and anti-carbonation resistance. On the condition of 55% mixing amount of fly ash and 6% HCSA, the compressive strength for 28 days enhanced 8MPa, the carbonation depth decreased by 0.7mm, at the age of 70, the strength increased by 12MPa and the depth reduced 1.7mm; when the mixing amount of HCSA reaches 10%, the internal structure of concrete would be destroyed; In the case of 6% HCSA amount, the compressive strength and anti-carbonation resistance decreases with the increase of fly ash mixing amount. While comparing to the concrete without HCSA, the compressive strength and anti-carbonation resistance increase obviously.


2018 ◽  
Vol 207 ◽  
pp. 01004
Author(s):  
Mu Li

Fly ash is a by-product of the combustion of the coal-fired electric power stations, and disposal of fly ash has been one of the environmental challenges. Much of the studies have been focused on the mechanical property of fly ash concrete. It is no doubt that the use of high-volume fly ash as a partial replacement of cement is also one of the effect way to utilize fly ash. It is known that the compressive strength of fly ash concrete is lower than that of ordinary concrete at early age, especially for high-volume fly ash concrete. It is urgent for engineers to consider the compressive strength of high-volume fly ash concrete at different curing age. In this review, the compressive strength of high-volume fly ash concrete in various literature was reported and then analyzed. Furthermore, the proposal of the utilization of high-volume fly ash concrete is provided.


2017 ◽  
Vol 79 (7-2) ◽  
Author(s):  
Antoni Antoni ◽  
Alvin Krisnanta Widianto ◽  
Jerry Lakshmana Wiranegara ◽  
Djwantoro Hardjito

Fly ash is a by-product of coal burning and is widely used as a substitute for cement material. The advantages of using fly ash in concrete include the improvement of workability and reduction of bleeding and segregation. The problem often encountered when using fly ash is the uncertainty of the fly ash quality. The quality is influenced by the coal origin, burning technique, mineral content, and capturing method. In this study, the consistency of fly ash from one power plant source was investigated for making a high-volume fly ash (HVFA) mortar. Variations in fly ash can be detected by applying rapid indicators as suggested in this paper; i.e., the pH of the fly ash in aqueous solution, the percentage of fly ash particles passing sieve #325 and the superplasticizer demand for the targeted slump flow. The fly ash replacement ratio was varied from 10–60% of cement, by mass. The results showed a large variation in the chemical content of the fly ash as shown by variation in pH, whereas only slight variation in the physical properties of the fly ash, i.e. particle size and shape. Superplasticizer demand for the same flow diameter was reduced with the increase of fly ash content, whereas the optimum fly ash replacement ratio for maximum strength varied among fly ash from different sampling periods. The compressive strength could reach that of control specimens at a replacement ratio of 20–30%, and mortar compressive strength of 42 MPa was still achievable at a replacement ratio of 50%.


2016 ◽  
Vol 872 ◽  
pp. 271-275 ◽  
Author(s):  
Mochamad Solikin

This paper presents a research to produce high strength concrete incorporated with fly ash as cement replacement up to 50% (high volume fly ash concrete) by using local material. The research is conducted by testing the strength development of high volume fly ash concrete at the age of 14 days, 28 days and 56 days. As a control mix, the compressive strength of Ordinary Portland Cement (OPC) concrete without fly ash is used. Both concrete mixtures use low w/c. consequently, they lead to the use of 1 % superplasticizer to reach sufficient workability in the process of casting. The specimens are concrete cubes with the dimension of 15 cm x15 cm x 15 cm. The totals of 24 cubes of HVFA concrete and OPC concrete are used as specimens of testing. The compressive strength design of concrete is 45 MPa and the slump design is ± 10 cm. The result shows that the compressive strengths of OPC concrete at the age of 14 days, 28 days, and 56 days are 38 MPa, 40 MPa, and 42 MPa. Whereas the compressive strength of HVFA concrete in the same age of immersing sequence are 29 MPa, 39 MPa, and 42 MPa. The result indicates that HVFA concrete can reach the similar compressive strength as that of normal concrete especially at the age of 56 days by deploying low water cement ratio.


2021 ◽  
Author(s):  
Aniruddha Baral ◽  
◽  
Jeffrey Roesler ◽  
M. Ley ◽  
Shinhyu Kang ◽  
...  

High-volume fly ash concrete (HVFAC) has improved durability and sustainability properties at a lower cost than conventional concrete, but its early-age properties like strength gain, setting time, and air entrainment can present challenges for application to concrete pavements. This research report helps with the implementation of HVFAC for pavement applications by providing guidelines for HVFAC mix design, testing protocols, and new tools for better quality control of HVFAC properties. Calorimeter tests were performed to evaluate the effects of fly ash sources, cement–fly ash interactions, chemical admixtures, and limestone replacement on the setting times and hydration reaction of HVFAC. To better target the initial air-entraining agent dosage for HVFAC, a calibration curve between air-entraining dosage for achieving 6% air content and fly ash foam index test has been developed. Further, a digital foam index test was developed to make this test more consistent across different labs and operators. For a more rapid prediction of hardened HVFAC properties, such as compressive strength, resistivity, and diffusion coefficient, an oxide-based particle model was developed. An HVFAC field test section was also constructed to demonstrate the implementation of a noncontact ultrasonic device for determining the final set time and ideal time to initiate saw cutting. Additionally, a maturity method was successfully implemented that estimates the in-place compressive strength of HVFAC through wireless thermal sensors. An HVFAC mix design procedure using the tools developed in this project such as the calorimeter test, foam index test, and particle-based model was proposed to assist engineers in implementing HVFAC pavements.


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