Current Issue : January - March Volume : 2019 Issue Number : 1 Articles : 5 Articles
Self-cured concrete is a type of concrete with a special ability to reduce autogenous\nshrinkage responsible for early-stage cracking. It is useful generally for the construction of high\nrise buildings and bridges. The application and use of this technique of curing concrete, however,\ndepends on the level of awareness among stakeholders regarding the application of the technique\nand its benefits among other factors. This study, therefore, sets out to investigate the level of\nawareness of selected construction professionals regarding the self-curing concrete technique in\naddition to the benefits. A cross-sectional survey design method was embraced by giving out\n115 questionnaires to builders and engineers in Lagos who were purposely selected. The data was\nsubjected to descriptive statistics. The results indicate that about 21% of selected builders and civil\nengineers practicing in Lagos are not aware and familiar with the concept of self-curing technology\nwhile about 43.1% of the professionals who have the knowledge of SCT have never used it in their\nprofessional practice. In addition, lower permeability, reduced coefficients of thermal expansion,\nand improved microstructures of cementitious paste were perceived as the dominant benefits of the\nself-curing concrete method. The implication of this study to construction professionals in Nigeria\nis in developing capacities on innovation practices in high-strength concrete technologies that will\nmake them strike a balance with international counterparts....
This paper presents a nondestructive test method to evaluate the residual bending strength\nof corroded reinforced concrete beam by analyzing the self-magnetic flux leakage (SMFL) signals. The\nautomatic scanning device was equipped with a micromagnetic sensor and sensor-based experimental\ndetails were introduced. Next, the theoretical formula of the normal component HS(z) of the SMFL\nsignal that originated from the corroded region was derived based on the magnetic dipole model and\nthe experimental results were discussed. The results indicate that the experimental data of HS(z) are\nconsistent with the theoretical calculations, both location and extent of the steel bars corrosion can be\nqualitatively determined by using HS(z). The gradient K of HS(z) is approximately linearly related to\nthe loss rate, S, of the bending strength, which can be used to evaluate the residual bending strength\nof the corroded reinforced concrete beam. This work lays the foundation for evaluating the residual\nbending strength of corroded reinforced concrete beams using the SMFL signal; the micromagnetic\nsensor is further applied to the civil engineering...
This paper presents an experimental investigation of the fatigue properties of limestone subjected to triaxial compression with\naxial cyclic loading. Tests were conducted on intact limestone samples with a loading frequency of 0.5 Hz and a confining pressure\nof 10 MPa. The test results show the following five points. (1) Under triaxial conditions, the axial and circumferential deformations\nat the failure point induced by cyclic loading are slightly larger than the corresponding deformations at the peak stress achieved by\nconventional compression tests. (2) The first level cyclic loading process has a strong influence on rock deformation in the primary\nphase during subsequent level cyclic loading. A smaller difference in stress amplitude between the two loading stress levels leads to\nless deformation during the latter. (3) Circumferential and volumetric changes are more sensitive to fatigue failure in terms of\ndeformation and strain rate than axial changes. (4) The three phases of dissipated energy evolution are consistent with a sampleâ??s\ndeformation such that the energy dissipation characteristics reflect the fatigue damage evolution process. (5) A new damage\nformula is proposed that can concisely describe a rockâ??s zero-cycle damage and damage evolution....
The surface morphology of a discontinuous structural plane in a natural rock mass is irregular. In studies on the shear strength of\ndiscontinuous structural planes, Barton introduced the joint roughness coefficient (JRC) to describe and calibrate the morphological\ncharacteristics of a rough structural plane. To describe Bartonâ??s typical rough profile model, researchers commonly\nconduct a comparison based on a standard curve. This approach does not guarantee graphic precision. With subjective\ncomparison reference drawing, the size and angle of a structural plane cannot be quantitatively controlled, and small bumps\ncannot be described. When the influence of the roughness coefficient of a rock surface is discussed, errors are caused by comparing\nBartonâ??s typical roughness profile model and a general structural surface model. This paper proposed a new method to simulate\nBartonâ??s typical structural surface. A numerical model of a complex structural plane is built automatically. The effects of cohesion\nand internal friction angle on the shear strength of the structural plane are discussed by changing the value of the shear\nstrength parameters....
Nuclear magnetic resonance (NMR) and damage impact testing, using a split Hopkinson pressure bar (SHPB) technique, were\nconducted on weakly weathered granites of different porosities. Based on this, this study determined and analysed the pore\nstructure and distribution, propagation characteristics of stress waves, changes in initial tangent modulus, and energy dissipation\nin weakly weathered granites of different porosities. The research demonstrated that the nature of the internal porosity of weakly\nweathered granites changed with total porosity. Pore structure significantly influenced the amplitude of reflected waves and\ndistortion of transmitted waves. Under constant-damage impact loads, the initial tangent modulus decreased with increasing\nporosity, whereas the stress-strain curves, after reaching the peak stress, had similar shapes. Peak stress and average strain rate\nshowed a strong power-law correlation with porosity, and peak stress decreased in a power-law correlation with the increase of\naverage strain rate. In other words, the difference in average strain resulted from different porosities when the incident energy was\nsame, and the average strain was negatively correlated with porosity. Under damaging impact, the energy absorbed per unit\nvolume decreased with increasing porosity. The research results reveal dynamic characteristics of natural porous rocks under\ndamage impacts, which provide a reference for studying damage effects of porous rocks under the effects of stress waves...
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