Effect of the Mineral Admixtures on Pipe Flow of Pumped Concrete

Abstract

The objective of this study is to investigate the effect of the mineral admixtures on pipe flow of pumped concrete through analyzing the properties of lubrication layer playing a dominant role to facilitate concrete pumping. Concrete mixtures incorporating blast furnace slag (BFS), fly ash (FA) and silica fume (SF) were selected with three different replacement ratios for each case and pumped through 170 m circuit. The rheological properties were measured before pumping and the thickness of lubrication layer was also experimentally observed with a special sensor, ultrasonic velocity profiler (UVP). An analytical equation considering the effect of the layer was adopted to calculate the thickness of the layer and to compare with full scale pumping results. The lubrication layer of BFS and FA indicated almost constant value regardless of replacement ratios but varied with SF mixtures. The concrete incorporating BFS or 5% SF represented satisfactory improvement of pumping efficiency.

Comparative Study of Different Measurement Methods for Characterizing Rheological Properties of Lubrication Layer

“…The constitutive mortar was obtained by screening the fresh concrete. The measurement applied was improved following the method proposed in [ 24 , 27 ]. A Viskomat XL coaxial rheometer, which has a four-bladed vane of the height ( h 1 ) of 70 mm and radius ( R i ) of 35 mm, was utilized to carry out the rheological measurement of samples.…”

“…Therefore, the lubrication layer is usually considered to be the constitutive mortar of fresh concrete. Some researches indicated that the yield stress and viscosity of the lubrication layer are small compared with that of bulk concrete, but the rheological properties of the lubrication layer directly determined the pressure loss along the pumping process [ 27 ]. Some authors have found that the thickness of the lubrication layer was about 2 mm through the measurement with ultrasonic velocity profiler, which may depend on the volume fraction of aggregate and the diameter of the pump pipe [ 28 ].…”

“…Hence, the rheological properties of the mortar wet-screened from the fresh concrete can be used to represent the rheological properties of the lubrication layer. Some investigations have demonstrated the effectiveness of this method [ 27 ]. Moreover, the Sliding Pipe Rheometer (Sliper) developed based on the principle of the Kaplan model is the latest device used to evaluate the concrete pumpability, which is convenient to carry and operate [ 42 ].…”

Research on Pump Primers for Friction Reduction of Wet-Mix Shotcrete Based on Precreating Lubricating Layer

“…For example, the lower the water-binder ratio, the thinner the lubricating layer. An Ultrasonic Velocity Profiler (UVP) was used to monitor the thickness of lubricating layer and measure the velocity of concrete cross section in the full size pumping circuit with or without adding mineral admixtures [12][13][14][15]. Another technique reported in literature [16] with particle image velocimetry (PIV) was applied to estimate the velocity profile along the cross section of concrete flowing in a half open pipe test configuration.…”

“…The fiber extracted from Cocos nucifera (coconut), treated as drag-reducing agent in aqueous media flow, was used to reduce friction in pipe flow, which created a huge profit for the pipeline company [30]. Myoung investigated the effect of the mineral admixture on pipe flow of pumping concrete through analyzing the properties of lubricating layer and noted that the usage of blast furnace and silica fume having 5% replacement could increase efficiency of pumping concrete [12].…”