ABSTRACT
Experimental methods were chosen accounting for the key factors affecting tamping effect, namely, fast hardening, tamping workability and pushout resistance force. From the beginning, the water absorbing tests of paper-wrapped tamping materials were performed because hydration of cement materials is affected by water/cement ratio. To examine hardening time, temperature and elastic wave velocity with curing time were measured. The hardening time is very important to decide tamping timing before blast ignition. Uniaxial compressive strength and shear strength of the tamping materials are associated with pull-out resistance for retaining explosion gases in a blast hole. Assuming a blast case which has short tamping length and
1 INTRODUCTION
The explosive blasting technique has been used in the field of building demolition engineering. More accurate, controlled collapse behavior of building structures has been demanded in order to reduce blast operation-induced environmental hazards, such as flyrocks, blowout, dust, etc (Little, 2007). In explosive demolition of building structures, complete removal of columns and shear walls which have to be blasted through blast scenarios is very important to ensure the entire collapse of the building. In recent years, some tamping materials have been suggested in order to reduce the tamping work time and cost in blasting demolition operations (Suk et al., 2010). Recent research projects have revealed that non-shrinking grout mortar and mixtures of natural sand and crushed rocks are effective as tamping materials for short tamping length through blast experiments (Cho et al., 2010). However the tamping work with the suggested tamping materials was time consuming. It is necessary to select tamping materials considering fast hardening, tamping workability and push-out resistance force, especially in case of shorter tamping length and small diameter.
