SOME PECULIAR CHEMISTRY ASPECTS OF SHOTCRETE ACCELERATORS
Tunnelling and mining job sites rely on the quality of recently sprayed shotcrete to securefreshly excavated zones. Worker safety in particular is therefore greatly dependent on theability of this sprayed material not only to stick to the wall but also to reliably develop a trueload beating capacity. In this paper, we demonstrate by ultrasound spectrometry that accelerators can alter bothflocculation and hydration. By flocculation, we refer to the stage in which fast precipitation,mainly of ettringite, thickens the material enough for it to stick on the wall and remain there.Apart from this the accelerators affect diversely hydration. More specifically, we demonstrate in the case of alkali free accelerators that someadditives that increase accelerator shelf life can dramatically retard hydration and strengthdevelopment. These results explain that while as some shotcrete mixes may hold up perfectlywell they do not develop sufficient load bearing capacity and may fail due to having to sustainload over a too long period of time or due to build up of hydrostatic pressure in cases of waterinfiltration. In such cases sudden collapse of shotcrete may occur after some hours, a situationthat is clearly undesirable.
Didier Lootens Benedikt Lindlar Robert J.Flatt
Sika Technology,Corporate Research,Zurich,Switzerland Sika Technology,Construction Chemicals and Mortars,Zurich,Switzerland
国际会议
南京
英文
1255-1261
2008-10-13（万方平台首次上网日期，不代表论文的发表时间）