scholarly journals A Consideration on the Mechanism of Reducing Rock Pressure under the Artificial Roof Made of Reinforced Cement Mortar

1969 ◽  
Vol 85 (978) ◽  
pp. 857-861
Author(s):  
Koji KOJIMA
Keyword(s):  
Rock Pressure ◽  
Cement Mortar ◽  
Reinforced Cement

scholarly journals Preparation and piezoresistivity of carbon nanotube-coated sand reinforced cement mortar

2020 ◽  
Vol 9 (1) ◽  
pp. 1445-1455
Author(s):  
Song Gao ◽  
Jianlin Luo ◽  
Jigang Zhang ◽  
Fei Teng ◽  
Chao Liu ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Cement Mortar ◽  
Aqueous Suspension ◽  
Ac Impedance ◽  
Stress Sensitivity ◽  
Multiwall Carbon Nanotube ◽  
Impedance Technique ◽  
Reinforced Cement ◽  
Coated Sand ◽  
Mechanical Strengths

Abstract Water and sand were used as the medium of multiwall carbon nanotube (MCNT) and prepared MCNT aqueous suspension and MCNT suspension-coated sand, respectively; afterwards, they were introduced into cement mortar (MNT/CM, MNTSM), respectively. Next, mechanical strengths and piezoresistive properties (DC resistivities (ρ v), AC impedances (Z r)) under cyclic loadings (σ c) of two types of MNT/CM and MNTSM nanocomposites were investigated to explore the intrinsic and self-sensing behaviors. Results reveal that MCNT can be evenly and well-coated on sand, which favors to achieve its intrinsic self-sensing property. Although the fraction changes in ρ v and Z r under the same σ c of MNTSM are both lower than those of MNT/CM, the stress sensitivity of MNTSM is only −1.16%/MPa (DC resistivity), −1.55%/MPa (AC impedance); its sensing linearity and stability (2.53, 2.45%; 2.73, 2.67%) are superior to those of MNT/CM (4.94, 2.57%; 3.78, 2.96%). Piezoresistivity using AC impedance technique is helpful to acquire balanced sensing sensitivity and stability while applied as intrinsic sensors in infrastructure.

Research on Anti-Cracking Performance of Polypropylene Fiber Reinforced Cement Mortar

2011 ◽  
Vol 189-193 ◽  
pp. 983-987 ◽  
Author(s):  
Hong Shen Xu ◽  
Yong Min Cao ◽  
Hong Ming Sun
Keyword(s):  
Theoretical Analysis ◽  
Critical Stress ◽  
Cement Mortar ◽  
Polypropylene Fiber ◽  
Fiber Reinforced ◽  
Cracking Performance ◽  
Reinforced Cement

Adding suitable quantity of polypropylene fiber is very effective for controlling plastic crack of cement mortar. During the experience stage, adding quantity of polypropylene fiber is 1.5 kg/m3, and crack rate of mortar is only 7.7%. Theoretical analysis is made for plastic crack mechanism of cement mortar, the results indicate that adding polypropylene fiber improves critical stress of crack expansion in mortar and notably reduces crack of cement mortar.

Resistance to Underwater Abrasion of Fiber Reinforced Cement Mortar

2017 ◽  
Vol 728 ◽  
pp. 379-383 ◽  
Author(s):  
Warun Wongprachum ◽  
Manote Sappakittipakorn ◽  
Pijit Jiemvarangkul
Keyword(s):  
Weight Loss ◽  
Abrasion Resistance ◽  
Steel Fiber ◽  
Cement Mortar ◽  
Polypropylene Fiber ◽  
Fiber Reinforced ◽  
Hydraulic Concrete ◽  
Reinforced Cement

Surfaces of hydraulic concrete conduits where significant abrasion of waterborne sediment can occur often degrade and need a regular repair to maintain their serviceability. In this research, thin overlay made of fiber reinforced cement mortar was introduced as a repair measures. Its resistance to underwater abrasion was therefore experimentally evaluated following the procedures of ASTM C 1138. This research utilized three types of fiber: steel fiber, polypropylene fiber, and micro polypropylene fiber (the micro polypropylene fiber was used only in a combination with either the steel or the polypropylene fiber). The influence of these fibers on the abrasion resistance of fiber reinforced cement mortar was then determined in terms of weight loss. The weight loss results showed that the fibers added to mortar specimens can enhance the abrasion resistance. Between the steel and polypropylene fiber, the latter provided better abrasion resistance. In case of the combination mixes, the micro polypropylene fiber increased abrasion resistance when combined with the polypropylene fiber but had no benefit when combined with the steel fiber.

scholarly journals Use of Higher-Harmonic and Intermodulation Generation of Ultrasonic Waves to Detecting Cracks due to Steel Corrosion in Reinforced Cement Mortar

2020 ◽  
Vol 14 (1) ◽  
Author(s):  
Miguel Ángel Climent-Llorca ◽  
Marina Miró-Oca ◽  
Pedro Poveda-Martínez ◽  
Jaime Ramis-Soriano
Keyword(s):  
Cement Mortar ◽  
Harmonic Distortion ◽  
Steel Corrosion ◽  
Convective Transport ◽  
Ultrasonic Waves ◽  
Void Space ◽  
Critical Events ◽  
Linear Features ◽  
Non Linear ◽  
Reinforced Cement

Abstract The aim of this work was to provide further confirmation of the possible use of non-linear ultrasonic techniques for detecting the cracking due to corrosion of steel reinforcements in concrete. To this end accelerated steel corrosion tests have been conducted on model reinforced cement mortar specimens, while monitoring the appearance and width evolution of visible surface cracks, and performing non-linear ultrasonic measurements based on the phenomena of harmonic distortion and intermodulation. A new parameter, based on the difference between the amplitude of the fundamental frequency and the sum of the amplitudes of all the first-order and second-order intermodulation products, has been proposed in this work. The results confirm that the appearance of visible surface micro-cracks are preceded and accompanied by the observation of strong non-linear features in the received signal. Furthermore, the new parameter proposed in this work is as efficient as the relative non-linearity parameters, classically used in harmonic distortion non-linear ultrasonic studies, for detecting the non-linear features associated with the critical events of the cracking of cement mortar due to embedded steel corrosion. A hypothesis has been developed considering the possible effect of the filling of the void space by liquid containing rust products after the formation of new cracks or the enlargement of its width. This filling process, which might be particularly enhanced by net convective transport of liquid, would explain the evolution of the values of all the parameters used for putting in evidence the non-linear elastic features after the critical events of the cracking process.

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