The mechanical properties and toughening mechanism of basalt fiber reinforced concrete (BFRC) with different fibers proportion ranging from 0 to 2.5 kg/m3 were tested in the experiment. The results show that the basalt fiber has little effect on the compressive strength of BFRC, but it can improve the impact toughness of BFRC significantly. Taking impact toughness as criterion, BFRC with 0.36% basalt fiber would be the best choice. The energy absorption characteristic of BFRC with different fibers dosages increases by 1.4~3.1 times than that of plain concrete when it is ultimately destroyed. Basalt fiber provides a secondary micro-reinforced system to BFRC when added into cement matrix. BFRC specimens show multi-cracking characteristics in the failure process, and the vice crack near the main crack is clearly observed while the final destruction.
Electrical conductive carbon-modified cement-based composites are important multi-functional structural material. Double compounding carbon fiber and carbon black into cement-based material can improve the electrical conductive property of cement-based composites. In this paper, the influences of carbon fiber ratio and total volume fraction of carbon components on the resistivity of cement-based composites are investigated. The results show that both carbon fiber ratio and total volume fraction have great effect on the conductive behavior of carbon-modified cement-based material. At a fixed carbon fiber ratio, with the increase of total volume fraction, the resistivity of cement-based composites drops down dramatically and shows obvious percolation phenomenon. The reason is that with more and more conductive particles and fibers added into the cement material, the conductive components connect with each other gradually and at certain point reach the percolation threshold. At a fixed total volume fraction, the resistivity drops down with the increase of carbon fiber ratio. This is because that the carbon fiber has larger aspect ratio than carbon black, so carbon fiber could get lower resistivity with the same dosage according to the percolation theory. Finally, the results show that with 0.5 carbon fiber ratio and 2% total volume fraction the carbon-modified cement-based composites have relatively low resistivity, high workability and high compressive strength.
Combinning at home and abroad research results, a new method of ‘sinking ball’ was put forward to evaluate the workability of self-compacting mortar (SCM). The size of ‘sinking ball’ and the volume of mortar vessel have been optimized by experiments. The results show that: when the ball with 20mm in diameter, the mortar vessel with 60mm in diameter and 160mm in heigh, the results of sinking ball test are best; Meanwhile, results indicate that the time of curve reflects the flow ability of SCM, the slope changing of curve indicates the anti-segregate ability of SCM, the integral area of curve has great relation with self-compacting ability of SCM.
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