scholarly journals Monitoring the Self-healing of Concrete from the Ultrasonic Pulse Velocity

2019 ◽  
Vol 3 (1) ◽  
pp. 16 ◽  
Author(s):  
Letícia Camara ◽  
Mayara Wons ◽  
Ian Esteves ◽  
Ronaldo Medeiros-Junior
Keyword(s):  
Fly Ash ◽  
Healing Process ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Ultrasonic Waves ◽  
The Self ◽  
Self Healing ◽  
Wetting And Drying ◽  
Rate Characteristic

Concrete has the ability to naturally heal its cracks, in a process called self-healing. This article aimed to analyze the self-healing of concretes, evaluating the influence of fly ash and the age of occurrence of cracks. Concrete specimens were submitted to cracking at 7 and 28 days. Subsequently, the samples were exposed to 12 wetting and drying cycles in order to favor the self-healing process. The phenomenon was evaluated through the ultrasonic pulse velocity testing, performed weekly on the specimens from the molding stage until the end of all cycles. The concretes showed a decrease in ultrasonic pulse velocity at the time they were cracked. This is due to the greater difficulty in the propagation of ultrasonic waves in the voids formed during cracking. This drop was higher for concrete with fly ash. Also, the results show that the fly ash concretes presented a more expressive self-healing process when cracked at 28 days, which may be related to the presence of pozzolanic reactions and the presence of more anhydrous particles. The concretes without fly ash had self-healing when they were cracked at 7 days. This is explained by the high hydration rate characteristic of ordinary Portland cement.

An Application of Rice Husk Ash (RHA) and Calcium Carbonate (CaCo3) as Materal for Self-Healing Cement

2016 ◽  
Vol 673 ◽  
pp. 3-12
Author(s):  
Januarti Jaya Ekaputri ◽  
Fahmi Firdaus Alrizal ◽  
Iqbal Husein ◽  
Triwulan ◽  
Mohd Mustafa Al Bakri Abdullah
Keyword(s):  
Calcium Carbonate ◽  
Rice Husk ◽  
Rice Husk Ash ◽  
Healing Process ◽  
Crack Depth ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Self Healing ◽  
Concrete Technology

Self-healing cement is a novel topic in concrete technology. Concrete is created to have its own ability to heal cracks. Crack closure is due to the material deposition of the gap so causing the crack closed. Materials used in this paper is mortar composition with ordinary portland cement replaced by calcium carbonate (CaCO3) and rice husk ash. There are three testing presented in this paper. The first is compressive test to determine the compression applied to mortar for initial cracks. The second is an ultrasonic pulse velocity (UPV) test to observe the depth of cracks and density of each composition. The third is macroscopic investigation to observe cracks wide in each mixture. The maximum compressive strength of 22.46 MPa shown by specimens made with 10% rice husk ash and 10% calcium carbonate cement. By the end of healing process, it reached 23.18 MPa. It was also shown that in crack depth decreased from 38 mm to 16 mm. From this analysis, it can be concluded that rice husk ash (RHA) and calcium carbonate (CaCO3) can be utilized as self-healing concrete materials.

scholarly journals Effects of a Real Exposure Class XC4 Mediterranean Climate Environment in the Behavior of Mortars Made Using Ternary Binders with Addition of Slag, Fly Ash and Limestone

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5848
Author(s):  
Javier Ibáñez-Gosálvez ◽  
Teresa Real-Herraiz ◽  
José Marcos Ortega
Keyword(s):  
Fly Ash ◽  
Mediterranean Climate ◽  
Mechanical Performance ◽  
Ultrasonic Pulse Velocity ◽  
Pore Network ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Cement Industry ◽  
Granulated Blast Furnace Slag ◽  
Compressive And Flexural Strengths

For improving the contribution of the cement industry to mitigate global warming, many strategies have been put into practice, such as the use of eco-friendly cements with the incorporation of additions substituting clinker. Nevertheless, the use of ternary binders for the production of commercial cements is still reduced, particularly in Spain. The purpose of this research is to characterize the long-term influence produced by the exposure to a real in situ inland Mediterranean climate condition in the pore network, parameters related to durability and mechanical performance of mortars made with ternary binders, which incorporated limestone, fly ash, and ground granulated blast-furnace slag, in comparison with mortars without additions and binary blended mortars. The site verified the specifications of exposure class XC4 of Eurocode 2. The ternary and binary binders accomplished the prescriptions of cement type CEM II/B. The pore network was studied with mercury intrusion porosimetry and electrical resistivity. Water absorption, diffusion coefficient, carbonation depth, ultrasonic pulse velocity, compressive and flexural strengths have been determined. The exposure to the environment produced after 250 days an increase in porosity, a loss of pore refinement, a rise of the carbonation depths, and a reduction in the mechanical strengths, highlighting the better overall performance of ternary mortar with both fly ash and slag.

Pulse Velocity Measurements in Fly Ash Blended Cementitious Systems Containing 43 Grade Cement

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
V. M. Sounthararajan ◽  
A. Sivakumar
Keyword(s):  
Fly Ash ◽  
Cost Savings ◽  
Ultrasonic Pulse Velocity ◽  
Cementitious Materials ◽  
Ultrasonic Pulse ◽  
Pozzolanic Reaction ◽  
Pulse Velocity ◽  
Supplementary Cementitious Materials ◽  
Pozzolanic Material ◽  
Cementitious Systems

Investigations on the different supplementary cementitious materials based on the hardening properties and the optimized dosage in cementitious systems find the right choice of pozzolanic material. It is essential to combine various additive/admixtures in concrete in proper proportions to maximize the benefits resulting in cost savings in construction. In the recent years, production technology and composition of hydraulic cements affect the setting and early age behavior of cementitious material. The addition of fly ash in cement is one viable technology to derive maximum benefits in terms of the economy and improved pozzolanic reaction. Ultrasonic pulse velocity testing is a feasible method for evaluating the hardening properties of cementitious materials. In this study, an attempt was made to derive the engineering basis for understanding the development of hardness during hydration of fly ash (FA) based cementitious systems. The tests conducted using pulse velocity technique proved to be an effective method for characterizing the early strength gain properties of different cementitious systems.

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.

scholarly journals Transport Properties and Resistance Improvement of Ultra-High Performance Concrete (UHPC) after Exposure to Elevated Temperatures

Buildings ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 416
Author(s):  
Yunfeng Qian ◽  
Dingyi Yang ◽  
Yanghao Xia ◽  
Han Gao ◽  
Zhiming Ma
Keyword(s):  
Compressive Strength ◽  
Transport Properties ◽  
High Temperatures ◽  
High Performance ◽  
High Performance Concrete ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Capillary Absorption ◽  
Self Healing

Ultra-high performance concrete (UHPC) has a high self-healing capacity and is prone to bursting after exposure to high temperatures due to its characteristics. This work evaluates the damage and improvement of UHPC with coarse aggregates through mechanical properties (compressive strength and ultrasonic pulse velocity), transport properties (water absorption and a chloride diffusion test), and micro-properties such as X-ray diffraction (XRD), Mercury intrusion porosimetry (MIP), and Scanning electronic microscopy (SEM). The result demonstrates that polypropylene (PP) fibers are more suitable for high temperature tests than polyacrylonitrile (PAN) fibers. The result shows that 400 °C is the critical temperature point. With the increase in temperature, the hydration becomes significant, and the internal material phase changes accordingly. Although the total pore volume increased, the percentage of various types of pores was optimized within 400 °C. The mass loss gradually increased and the ultrasonic pulse velocity gradually decreased. While the compressive strength first increased and then decreased, and the increase occurred within 25–400 °C. As for the transport properties, the chloride migration coefficient and capillary absorption coefficient both increased dramatically due to the higher sensitivity to temperature changes. The results of the property improvement test showed that at temperatures above 800 °C, the compressive strength recovered by more than 65% and the ultrasonic pulse velocity recovered by more than 75%. In terms of transport properties, compared to the results before self-healing, the chloride migration coefficient decreased by up to 59%, compared with 89% for the capillary absorption coefficient, after self-healing at 800 °C. With respect to the enhancement effect after exposure to high temperatures, the environment of a 5% Na2SO4 solution was not as good as the clean water environment. The corresponding changes in microstructure during the high temperatures and the self-healing process can explain the change in the pattern of macroscopic properties more precisely.

SYNTHESIS AND CHARACTERIZATION OF SELF-HEALING MORTAR WITH MODIFIED STRENGTH

2015 ◽  
Vol 76 (1) ◽  
Author(s):  
Gassan Fahim Huseien ◽  
Jahangir Mirza ◽  
Nur Farhayu Ariffin ◽  
Mohd Warid Hussin
Keyword(s):  
Early Stage ◽  
Polymeric Materials ◽  
Building Blocks ◽  
Ultrasonic Pulse Velocity ◽  
Cementitious Materials ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Diglycidyl Ether ◽  
Self Healing ◽  
Research Initiative

Cementitious materials being the most prospective building blocks achieving their absolute strength to avoid the deterioration in the early stage of service life is ever-demanding. Minimizing the labor and capital-intensive maintenance and repair cost is a critical challenge. Thus, self-healing mortars with modified strength are proposed. Lately, self-healing of micro-cracks by introducing bacteria during the formation of mortar or concrete became attractive. Self-healing with polymeric admixtures is considered to be relatively more durable and faster process. Certainly, the self-healing of synthetic polymeric materials is inspired by biological systems, where the damage triggers an autonomic healing response. This emerging and fascinating research initiative may significantly improve the durability and the safety limit of the polymeric components potential for assorted applications. In this work, using epoxy resin (diglycidyl ether of bisphenol A) without any hardener as admixture polymeric-cementitious materials is prepared. These epoxy-modified mortars are synthesized with various polymer-cement ratios subjected to initial wet/dry curing (WDC) together with long term dry curing (DC). Their self-healing function and hardening effects are evaluated via preloading and drying of the specimens, chemical analysis, and ultrasonic pulse velocity testing. It is demonstrated that 10% of polymer is the best proportion for polymer-cement ratio. Furthermore, the wet/dry curing is established to be superior process for healing hairline cracks present in the mortar. The excellent features of the results suggest that our novel method may constitute a basis for improving the compressive strength and self-healing features of mortars.    

scholarly journals Comparative study on physical and mechanical properties of high slump and zero lump high volume fly ash concrete (HVFAC)

2013 ◽  
Vol 15 (4) ◽  
pp. 578-584 ◽  
Keyword(s):  
Experimental Investigation ◽  
Fly Ash ◽  
Physical And Mechanical Properties ◽  
High Volume ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Fly Ash Concrete ◽  
High Volume Fly Ash ◽  
Class F Fly Ash

<p>An experimental investigation was carried out to compare the compressive strength of zero slump and high slump concrete with high volume fly ash. 40% to 70% replacements of OPC (by weight) with class F fly ash have been incorporated. Superplasticizer was added at 1% of binder (cement + fly ash) to the zero slump mixture to get a slump in the range of 140 to 180mm and cubes were cast without compaction. The results showed that the apparent porosity and water absorption were higher for zero slump concrete than high slump concrete. Zero slump concrete showed better compressive strengths than superplasticized concrete with 40 to 60% fly ash addition for all curing times tested (3,7 and 28 days). Ultrasonic pulse velocity results categorized all mixes as of &lsquo;EXCELLENT&rsquo; concrete quality. Based on the present experimental investigation, it can be concluded that high volume fly ash concrete is suitable for general construction applications.</p>

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