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.

The Combined Effect of CKD and Silica Fume on the Mechanical and Durability Performance of Cement Mortar

2021 ◽  
Vol 895 ◽  
pp. 59-67
Author(s):  
Mayadah W. Falah ◽  
Alaa Adnan Hafedh ◽  
Safa A. Hussein ◽  
Zainab S. Al-Khafaji ◽  
Ali A. Shubbar ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Silica Fume ◽  
High Performance ◽  
High Performance Concrete ◽  
High Strength ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Cement Kiln ◽  
Substitute Products

To manufacture high-strength and high-performance concrete, the incorporation of silica fume with concrete was becoming popular nowadays. When utilizing various amounts of cement substitute products, the design becomes even more complicated. The latest research has been dedicated to researching the applicability of cement substitute products for cement kiln dust (CKD) and silica fume (SF). In permeability and compressive strength terms, the effect of these components on the efficacy of the concrete would be studied. Also, the materials proposed might limit greenhouse gas emissions, which will mitigate climate change on other causes of global pollution. Casting a standard concrete cube (100 percent OPC) equivalent to (150 gm) would initiate the experiment, which was utilized later for comparative purposes. The industrial waste materials (SF and CKD) was be applied as cement substitution proportions (10 percent, 20 percent, and 30 percent) of the dry cement weight at varying percentages of each component (5 percent, 10 percent, and 15 percent). Eventually, after 7, 14, 28 days, the compressive strength shift would be calculated. The permeability of the latest concrete will be checked after (7, 14, and 28) days of healing utilizing ultrasonic pulse velocity (UPV) technology. The experimental findings indicate that with a specimen comprising 20 percent of (SF and CKD) relative to (100 percent OPC) specimen, there is an improvement in compressive intensity and pulse velocity values in various curing times and specimens of various (SF and CKD) specimen M3 have a decrease in pulse velocity value after 7 curing days.

The Effect of Different Sand Gradation with Ultra High Performance Concrete (UHPC)

2018 ◽  
Vol 280 ◽  
pp. 476-480 ◽  
Author(s):  
N.A. Hamiruddin ◽  
R. Abd Razak ◽  
K. Muhamad ◽  
M.Z.A. Mohd Zahid ◽  
C.N.S. Che Ab Aziz
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
High Performance Concrete ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Material Research ◽  
Ultra High Performance Concrete ◽  
New Class ◽  
Flow Test

Advances in concrete material research has introduced to development the new class of concrete which is known as Ultra High Performance Concrete (UHPC). Due to the most exceedingly awful on nature coarse aggregate quality, UHPC was delivered to success in concrete. This study investigated the effect of differentsand gradation (63-300μm, 300-600μm, 600-1180μm, and normal sand) on compressive strength and ultrasonic pulse velocity (UPV) of UHPC. The rheology of UHPC mixtures was determined by flow test conducted according to ASTM C1611 and the compression testwas performed to measure concrete compression strength at 7 and 28 days according to BS 1881-116 (1983). To determine the quality of concrete, UPV test were conducted according to BS 1881 part 201 (1986).From the experimental results, the results indicated that sand grading with 600-1180μm obtained the highest in compressive strength and UPV.The compressive strength at 28 days achieved 100 MPawith direct transmission of UPV 4.5% higher than semi direct.

Strength - Ultrasonic Pulse Velocity Relationship of Thermally Activated Alum Sludge Multiple Blended High Performance Concretes

2013 ◽  
Vol 594-595 ◽  
pp. 521-526 ◽  
Author(s):  
Haider Mohammed Owaid ◽  
Roszilah Hamid ◽  
Mohd Raihan Taha
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Ternary Blends ◽  
Exponential Relationship ◽  
Palm Oil Fuel Ash ◽  
Thermally Activated ◽  
Alum Sludge

In this research the performance of ultrasonic pulse velocity in concrete is examined as a nondestructive experiment, in order to estimate compressive strength of thermally activated alum sludge multiple blended high performance concretes (HPC) that contain AAS, silica fume (SF), ground granulated blast furnace slag (GGBS) and palm oil fuel ash (POFA) are determined in both binary and ternary blends of cement. The water/binder ratio and total binder content are fixed at 0.30 and 493 kg/m3 for all types of mixes. The ultrasonic pulse velocity (UPV) of each concrete mix was measured using 100mm cubes after a curing period of ages of 3, 7, 28, 56 and 90 days. The results indicate a very positive exponential relationship between compressive strength and UPV for both binary and ternary blends of HPC mixtures, with coefficient correlation (R2) of 0.889.

scholarly journals The relationship between the compressive strength and ultrasonic pulse velocity concrete with fibers exposed to high temperatures

2018 ◽  
Vol 3 (1) ◽  
pp. 31
Author(s):  
Belaribi Hassiba ◽  
Mellas Mekki ◽  
Rahmani Fraid
Keyword(s):  
Compressive Strength ◽  
Ultrasonic Velocity ◽  
High Temperatures ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Cement Ratio ◽  
Compressive Strength Of Concrete ◽  
The Relationship ◽  
The Waves

The paper analyses the effects of high temperatures on the concrete residual strength using ultrasonic velocity (UPV). An experimental investigation was conducted to study the relationship between UPV residual data and compressive strength of concrete with different mixture proportions, cubic specimens with water-cement ratio of 0.35. They were heated in an electric furnace at temperatures ranging from 200°C to 600°C. In this experiment a comparison was made between the four groups which include two types of fibers steel 0,19%, 0,25% and 0,5%, polypropylene: 0,05%, 0,11% 0,16 % by volume. Cube specimens were tested in order to determine ultrasonic velocity. The compressive strength was tested too. According to the results, relations were established between ultrasonic velocity in the specimens and the compressive strength at different temperature and the range of the velocity of the waves were also determined for this kind of concrete. Result of the test showed that UPV test can be successfully used in order to verify the consistency of structures damaged by fire.

scholarly journals Prediction of the compressive strength of high-performance self-compacting concrete by an ultrasonic-rebound method based on a GA-BP neural network

PLoS ONE ◽  
2021 ◽  
Vol 16 (5) ◽  
pp. e0250795
Author(s):  
Guoqiang Du ◽  
Liangtao Bu ◽  
Qi Hou ◽  
Jing Zhou ◽  
Beixin Lu
Keyword(s):  
Neural Network ◽  
Compressive Strength ◽  
Correlation Coefficient ◽  
High Performance ◽  
Ultrasonic Pulse Velocity ◽  
Test Sample ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Self Compacting Concrete ◽  
Bpnn Model

To address the problem of low accuracy and poor robustness of in situ testing of the compressive strength of high-performance self-compacting concrete (SCC), a genetic algorithm (GA)-optimized backpropagation neural network (BPNN) model was established to predict the compressive strength of SCC. Experiments based on two concrete nondestructive testing methods, i.e., ultrasonic pulse velocity and Schmidt rebound hammer, were designed and test sample data were obtained. A neural network topology with two input nodes, 19 hidden nodes, and one output node was constructed, and the initial weights and thresholds of the resulting traditional BPNN model were optimized using GA. The results showed a correlation coefficient of 0.967 between the values predicted by the established BPNN model and the test values, with an RMSE of 3.703, compared to a correlation coefficient of 0.979 between the values predicted by the GA-optimized BPNN model and the test values, with an RMSE of 2.972. The excellent agreement between the predicted and test values demonstrates the model can accurately predict the compressive strength of SCC and hence reduce the cost and time for SCC compressive strength testing.

scholarly journals Coconut Fiber Strengthen High Performance Concrete: Young’s Modulus, Ultrasonic Pulse Velocity and Ductility Properties

2018 ◽  
Vol 7 (2.23) ◽  
pp. 284 ◽  
Author(s):  
M A. Othuman Mydin ◽  
N Mohd Zamzani
Keyword(s):  
Young’S Modulus ◽  
High Performance ◽  
High Performance Concrete ◽  
Young's Modulus ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Engineering Properties ◽  
Axial Compressive Strength ◽  
Coconut Fibre

This paper emphasis on experimental investigation to govern the engineering properties such as young’s modulus, pundit ultrasonic pulse velocity (UPV) and ductility of High Performance Concrete (HPC) with grade M60 with addition of coconut fibre (CNF) together with silica fume (SF) and pulverised fuel ash (PFA). For this study, 3 mixes were prepared. First was the CNFRC without any additives, secondly the CNFRC made by 10% replacement of cement weight with PFA and thirdly composition of 10% of cement weight was exchanged with SF. It should be pointed out that for each mix; CNF was included in the mixture (0.5% of the mix volume). The investigational results had shown that the Young’s modulus of CNFRC, CNFR SFC and CNFR PFAC enhanced by about 6%, 3%, and 12% correspondingly. In terms of ductility, when control HPC specimens were subjected to axial compressive strength, slight preliminary cracks shaped on the surface of specimens. Among all HPC specimens tested, CNFR PFAC attained the utmost UPV at 28 day.    

scholarly journals Behavior of Biochar-Modified Cementitious Composites Exposed to High Temperatures

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5414
Author(s):  
Xu Yang ◽  
Run-Sheng Lin ◽  
Yi Han ◽  
Xiao-Yong Wang
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Compressive Strength ◽  
High Temperatures ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Temperature Resistance ◽  
Residual Compressive Strength ◽  
Scanning Electron

In this study, the effect of biochar on the high temperature resistance of cementitious paste was investigated using multiple experimental methods. The weight loss, cracks, residual compressive strength, and ultrasonic pulse velocity (UPV) of biochar cementitious paste with 2% and 5% biochar exposed to 300, 550 and 900 °C were measured. The products and microstructures of biochar cementitious paste exposed to high temperatures were analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. The results showed that the cracks of specimens exposed to high temperatures decreased with increasing biochar content. The addition of 2% and 5% biochar increased the residual compressive strength of the specimens exposed to 300 °C and the relative residual compressive strength at 550 °C. As the exposure temperature increased, the addition of biochar compensated for the decreasing ultrasonic pulse velocity. The addition of biochar contributed to the release of free water and bound water, and reduced the vapor pressure of the specimen. The addition of biochar did not change the types of functional groups and crystalline phases of the products of cementitious materials exposed to high temperatures. Biochar particles were difficult to observe at 900 °C in scanning electron microscopy images. In summary, because biochar has internal pores, it can improve the high-temperature resistance of cement paste.

scholarly journals Use of Bacteria Externally for Repairing Cracks and Improving Properties of Concrete Exposed to High Temperatures

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1503
Author(s):  
Milad Nimafar ◽  
Bijan Samali ◽  
Saied Jalil Hosseini ◽  
Alireza Akhlaghi
Keyword(s):  
Electrical Conductivity ◽  
Compressive Strength ◽  
Calcium Carbonate ◽  
High Temperatures ◽  
Ultrasonic Pulse Velocity ◽  
Bacillus Sphaericus ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Calcium Carbonate Precipitation ◽  
Bacterial Remediation

The current paper presents the results of an experimental study on the application of calcium carbonate precipitation bacteria as a new approach to repairing damaged concrete when exposed to high temperatures. To do so, cylindrical and cubic concrete specimens were initially exposed to heat in a furnace for 1 h, after reaching two different temperatures of 600 and 800 °C. A heat rate of 5.5 °C per minute was used to achieve the target temperatures. Then, two types of bacteria, namely Sporosarcina pasteurii and Bacillus sphaericus, with cell concentration of 107 cells/mL, were utilized externally, to repair the thermal cracks, enhancing the mechanical properties and durability of the damaged concrete. The efficiency of the bacterial remediation technique was then evaluated through compressive strength, ultrasonic pulse velocity (UPV), and electrical conductivity tests on the control specimens (unexposed to heat), and those exposed to high temperature with or without bacterial healing. The experimental results demonstrate that the compressive strength of the test specimens exposed to temperatures of 600 and 800 °C decreased by about 31–44% compared with the control ones. However, compared to those damaged at 600 and 800 °C, the compressive strength of specimens repaired by the S. pasteurii and the B. sphaericus showed increases of 31–93%. This increase is associated with the precipitation of calcium carbonate in the deep and superficial cracks and pores of the damaged specimens. Furthermore, the ultrasonic pulse velocity of the specimens subjected to bacterial remediation had a significant increase of about 1.65–3.47 times compared with the damaged ones. In addition, the electrical conductivity of repaired specimens decreased by 22–36% compared with the damaged specimens.

PERFORMANCE OF EPOXY RESIN AS SELF-HEALING AGENT

2015 ◽  
Vol 77 (16) ◽  
Author(s):  
Abdul Rahman Mohd Sam ◽  
Nur Farhayu Ariffin ◽  
Mohd Warid Hussin ◽  
Han Seung Lee ◽  
Mohamed A. Ismail ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Epoxy Resin ◽  
Ultrasonic Pulse Velocity ◽  
Ultrasonic Pulse ◽  
Pulse Velocity ◽  
Self Healing ◽  
Fine Aggregates ◽  
Healing Agent ◽  
Initial Reading ◽  
External Intervention

Formation of cracks due to the shrinkage effects during curing and mechanical loading can deteriorate the concrete performance especially in terms of durability aspect. Chemical and harsh solutions will easily penetrate into the concrete and cause damage to the concrete. In order to solve this problem, researchers have introduced a self-healing concrete; the mechanism of automatically repairing concrete cracks without external intervention. Nowadays, the self-healing concrete by using bacteria as a healing agent had gained interest among researchers. In contrast, this paper presents the study on performance of epoxy resin without hardener as a self-healing agent in concrete. Mortar specimens were prepared with mass ratio of 1:3 (cement: fine aggregates), water-cement ratio of 0.48 and 5 to 20% epoxy resin of cement content. All tested specimens were subjected to wet-dry curing; where compressive strength, apparent porosity and self-healing evaluation were measured. Result shows that, the compressive strength of mortar with addition of epoxy resin by 10% increased significantly compared to normal mortar. Epoxy resin as a healing agent was found to be functioned well as the compressive strength and ultrasonic pulse velocity regain the initial reading with prolonged curing time. These results together with microstructure test indicate that epoxy resin can be used as a self-healing agent.

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