The demolition of concrete or rocks was carried out with the two kind of static demolition agents
consisting of CaO as the main ingredient.
The first type of the agent, the delay type cracked concrete or rocks after 12 hours, and it was
guessed that the expansion pressure was needed to be over 300 kg / cm2. Split lines were observed in
the cracks.
The second type, the rapid type cracked concrete of rocks after 30 to 60 minutes, and the expansion
pressure was needed to be over 600 kg / cm2 and the occurrence velocity had to be over 300 kg / min. For
the rapid type, it was recognized that water vapor with the vapor pressure of 10 kg / cm2 and the
temperature of 150 ℃ played an important role.
It is suggested for the cracking mechanism by the rapid type that the pulsating motion of high
pressure water vapor produced in a hole acts on concrete or rocks to migrate them.
生石灰(Ca0)から水を付加することによって生じる消石灰(Ca(OH)2)の体積膨脹をその主応力とする静的破砕剤の膨脹圧発生挙動は, (イ)充填後12時間以上経過して所定の膨脹圧に到達し岩盤へ亀裂発生させる遅効性タイプと, (ロ)充填後30 - 60分で所定の膨張圧に到達し岩盤破砕を行う速効性タイプの二種類に大別される｡
前者は膨脹圧の上昇と共に岩盤が持つ潜在的亀裂が顕在化し目視可能な亀裂線が発生するのに対し, 後者は亀裂発生と共にその線に沿って若干の岩盤移動があり亀裂巾が大きくなる特長を持ち, いわゆる破砕現象が観察される｡
具体的に亀裂が発生する条件として, (イ)遅効性破砕剤は最大膨脹圧が300 kg / cm2以上であり, (ロ)速効性破砕剤は最大膨脹圧は600 kg / cm2以上が必要であり, かつ膨脹圧力発生速度が300 kg / min を越える場合に, 破砕効果が現われることが判明した。