Practical Tribometer to Estimate Pumpability of Fresh Concrete

Abstract

The friction at the steel-concrete interface on the boundary layer that occurs during the flow of a fluid concrete in a drain plays an important part in its pumpability. These frictions are directly related to the composition of the formed boundary layer which depends on the concrete composition parameters. In order to highlight the relationship between concrete composition and friction interface, the authors initially developed and validated an apparatus called tribometer allowing them to make steel-concrete interface friction measurements and deduce interface parameters. Its' simple use at building sites enabled the authors to study the influence of the concrete composition on the resulting interface friction and its parameters, namely, viscous constant and interface yield stress. The results show that the increase in the cement paste volume, the water per cement ratio and the proportioning in superplasticizer support the concrete pumpability. The increase of the fine sand quantity in concrete induces negative effects on the interface frictions and on pumpability.

A Review on the Pumping Behavior of Modern Concrete

“…The pumping resistance is in essence determined by the friction between the pipe and the lubrication layer (Kwon et al 2013;Jo et al 2012). The friction at the pipe-concrete interface occurs when fresh concrete flows (Ngo et al 2010a(Ngo et al , 2010b. The pumping can be operated only when the pump pressure is larger than the friction (Eda 1957; Browne and Bamforth 1977;Le et al 2015).…”

“…However, significant progress has been made in the composition of lubrication layer. As noted by Ngo et al (2010aNgo et al ( , 2010b, the lubrication layer is normally composed of water, cementitious materials and fine sand. The diameter of the fine sand is smaller than 0.25 mm.…”

“…Kaplan et al (2005b) found the lubrication layer has a thickness of approximately 1 to 5 mm. Ngo et al (2010b) stated that the thickness of lubrication layer for different concrete mixtures varied between 1 to 9 mm, and it was increased with the increase in water-cement ratio, superplasticizer content and the volume of cement paste but was decreased with the increase of the volume fraction of fine sand. From the viewpoint of rheology, it can reduce the apparent plastic viscosity and increase the thickness of the lubrication layer in a desirable range by reducing the content of fine sand, increasing water-cement ratio and increasing superplasticizer content.…”

Estimation of the Pumping Pressure from Concrete Composition Based on the Identified Tribological Parameters

“…In this study, the authors are interested in the pumping pressure of ordinary concrete whose rheological behavior can be described as Binghamian fluids as discussed elsewhere [4,7,8,14,15,19,[21][22][23][24][25]. It is given by…”

“…The used viscous constant ( ) model is proposed by Ngo et al [15,18,25]. The model is given by = 10 (3.7(Φ/Φ * )+0.37) boundary layer , (2) exp.…”