Using Eccentrically Sample to Find the Relationship between Resistivity and Cracking Time in Cement Paste Vides Mechanical Strength and Electrical Resistivity

Abstract

Early-age cracking is often attributed as a major cause of reduction in the durability of concrete structures. The objective of this paper is to study the hydration behavior of various samples of different water-cement ratios, that's in order to assess crack potential, compressive strength and setting time of the cement paste. The behavior of hydration was monitored by using a non-contact electrical resistivity apparatus. While a new eccentrically steel cracking frame (ESCF), setting time and compressive strength standard test were considered to measure the restrained shrinkage cracks, compressive strength and setting time respectively. The objective of using the eccentrically sample is to provide a new method to assess the cracks at early age by presents a complicated and non-uniform circumferential stress in the eccentrically cement paste ring. The results show that the electrical resistivity measurement of all samples with different water cement ratios had similar trends. Whereas the lowest water-cement ratio paste indicates highest resistivity values, reaches an earlier inflection point, and obtained higher compressive strength than other cement pastes of higher water-cement ratio. The eccentrically restrained cracking test (ERCT) and setting time demonstrated that lower water-cement ratio paste set and cracked earliest, which is therefore, confirmed its highest cracking tendency. The cracks took place at the narrow regions of specimens, which can be an indicator for eccentrically restrained shrinkage test (ERST). The cracks were observed as growing at narrow areas and reach full-depth over time. A mathematical model for predicting the cracking age of cement is proposed. The equation showed the existence of a positive relationship between electrical resistivity represented by inflection points (Ti) and cracks time (Tc).

Comparative Analysis on Use of Polymer Fibres from Recycled Polyethylene Terephthalate into Reinforced Concrete Solutions

“…In this context, the use of concrete is somewhat restricted by specific phenomena such as cracking, shrinkage or durability. The concrete has numerous and significant technical and economic advantages, which have attracted the attention of specialists [1][2][3][4][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. For this reason, various studies and research have been made, which have led to improvements in its performance.…”

“…For this reason, various studies and research have been made, which have led to improvements in its performance. One of the ways of improvement can be achieved by adding in their mass of dispersed reinforcements, in the form of different type of fibers [1][2][3][4][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. The dispersed reinforced concrete results in the inclusion of a variable amount of discontinuous fibres in the concrete mass [1][2][3][4][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25].…”

“…A typically concrete mixture by volume is about 60 to 75% fines sand and coarse aggregates, 10 to 15% cement, and 15 to 20% water (Figure 1). Entrained air bubbles in many concrete mixtures may also take up another 5 to 8% by volume (Figure 2) [1][2][3][4][19][20][21]. Concrete can be moulded or formed into any shape when newly mixed, strong and durable when hardened [1][2][3][4].…”

“…Other types of fibres include, but are not limited to, natural (wood or plant), mineral (basalt), glass and carbon (Figure 4). Research into new fibre-reinforced concretes continues today [1][2][3][4][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Also, several studies concludes that hybrid reinforcements (steel and polypropylene fibres) showed improved characteristics and mechanical properties of concretes [12,17,18].…”

“…Polymer fibres are utilized in diverse applications, such as industrial floors, wind turbine blades, bridges or prefabricated products [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. The amount of polymer fibres added to concrete is expressed as a percentage of the total volume of the cement-based composite, typically ranges up to 3% (Figure 5) [7,8].…”