Soundless Chemical Demolition Agents Research Articles

Prediction of the Minimum Required Pressure of Soundless Chemical Demolition Agents for Plain Concrete Demolition

도심지나 문화재가 인접한 지역 등의 소음, 진동 등 기존 발파해체 공법이 제한적인 조건에서 사용할 수 있는 구조물 해체 공법으로 무소음화학팽창제(soundless chemical demolition agent, SCDA)를 이용한 공법이 있다. 그러나 SCDA의 사용에 대한 기준이나 가이드라인에 참고될 만한 연구는 미미한 실정이다. 이 연구에서는 실내실험을 수행하여 강관의 길이, 외부수분차단, 수화열 발산 등의 다양한 조건에 따른 SCDA의 팽창압 발현 특성을 확인하였다. 또한 SCDA의 최소요구팽창압 예측을 위한 해석모델(자유단 1면, 고정단 3면의 직사각형 모델)을 개발하고 주요변수해석(홀 간 거리, 콘크리트 압축강도)을 수행하였다. 이 연구의 해석결과를 활용하여 자유단으로부터 콘크리트 구조물의 박락을 효과적으로 유도할 수 있을 것으로 판단된다.

Impact of thermal transfer on hydration heat of a Soundless Chemical Demolition Agent

This paper explores thermal transfer effects in Soundless Chemical Demolition Agents (SCDA). In a 10 °C water bath, quadrupling the volume of SCDA in a pipe accelerated peak hydration onset and resulted in a 700% increase in expansive pressure and a 20% increase in volumetric expansion. An equivalent sample in a constant temperature chamber showed an almost 5 °C greater hydration heat than in the water bath, which resulted in a six-fold expansive pressure difference after 4 days of testing and an order of magnitude more pressure in the first 24 h, thereby demonstrating limitations of previous SCDA experimental work and providing a temperature-based reason for discrepancies between large-scale testing and manufacturers’ predictions. Since most construction projects have scheduling requirements, understanding how to achieve sufficiently high pressures within a single work shift is important for evaluating the field viability of SCDAs on a particular project.

Experimental study on fracturing coal seams using CaO demolition materials to improve permeability

Abstract Currently, methane gas disasters in underground coal mines are a major problem which seriously threatens safe mining. This study employed soundless chemical demolition for fracturing coal seams with low permeability. Additionally, the fracturing theory and failure mechanisms of soundless chemical demolition agents were investigated. Materials such as CaO, naphthalene-based water reducer, sodium gluconate and silicate cement were used to prepare the novel soundless chemical demolition agent, whose optimum proportion was discovered to be 90:3:5:7 by carrying out orthogonal experiments. The innovative demolition agent cracked briquettes and the maximum width of cracks reached 16.33 mm, showing significant potential for improving the permeability of coal seams.

Temperature-related performance factors for chemical demolition agents

Soundless chemical demolition agents (SCDAs) are percussion-free alternatives to blasting for selective demolition. Although known to be temperature sensitive, to date their performance has not been quantified in ambient environments below 20°C. This paper examines 6 large-scale specimens at 16.1-19.3°C. Substantially slower response than that reported by manufacturers was documented. Initial cracking required 25 + h and continued for 4-8 days. Cracks opened rapidly after minimum demolition time [(MDT)-cumulative cracking around the perimeter reaching ~25 mm], which was at 42 and 70 h, respectively in 16.8 and 33.1 MPa specimens. Post-MDT, crack width opening velocities were 0.35-0.96 mm/h, approximately one-third to two-thirds pre-MDT velocities. A 0.5°C ambient temperature drop delayed MDT by 6.5 h amongst equi-sized specimens of the same strength. Generally, MDT correlated with material strength (irrespective of ambient temperature or specimen size), whereas time to first crack was more influenced by temperature. Also, SCDA reapplication proved effective for incompletely cracked specimens.

Temperature-related performance factors for chemical demolition agents

Soundless chemical demolition agents (SCDAs) are percussion-free alternatives to blasting for selective demolition. Although known to be temperature sensitive, to date their performance has not been quantified in ambient environments below 20°C. This paper examines 6 large-scale specimens at 16.1-19.3°C. Substantially slower response than that reported by manufacturers was documented. Initial cracking required 25 + h and continued for 4-8 days. Cracks opened rapidly after minimum demolition time [(MDT)-cumulative cracking around the perimeter reaching ~25 mm], which was at 42 and 70 h, respectively in 16.8 and 33.1 MPa specimens. Post-MDT, crack width opening velocities were 0.35-0.96 mm/h, approximately one-third to two-thirds pre-MDT velocities. A 0.5°C ambient temperature drop delayed MDT by 6.5 h amongst equi-sized specimens of the same strength. Generally, MDT correlated with material strength (irrespective of ambient temperature or specimen size), whereas time to first crack was more influenced by temperature. Also, SCDA reapplication proved effective for incompletely cracked specimens.

An Alternative to Conventional Rock Fragmentation Methods Using SCDA: A Review

Global energy and material consumption are expected to rise in exponential proportions during the next few decades, generating huge demands for deep earth energy (oil/gas) recovery and mineral processing. Under such circumstances, the continuation of existing methods in rock fragmentation in such applications is questionable due to the proven adverse environmental impacts associated with them. In this regard; the possibility of using more environmentally friendly options as Soundless Chemical Demolition Agents (SCDAs) play a vital role in replacing harmful conventional rock fragmentation techniques for gas; oil and mineral recovery. This study reviews up to date research on soundless cracking demolition agent (SCDA) application on rock fracturing including its limitations and strengths, possible applications in the petroleum industry and the possibility of using existing rock fragmentation models for SCDA-based rock fragmentation; also known as fracking. Though the expansive properties of SCDAs are currently used in some demolition works, the poor usage guidelines available reflect the insufficient research carried out on its material’s behavior. SCDA is a cementitious powdery substance with quicklime (CaO) as its primary ingredient that expands upon contact with water; which results in a huge expansive pressure if this CaO hydration reaction occurs in a confined condition. So, the mechanism can be used for rock fragmentation by injecting the SCDA into boreholes of a rock mass; where the resulting expansive pressure is sufficient to create an effective fracture network in the confined rock mass around the borehole. This expansive pressure development, however, dependent on many factors, where formation water content creates a negative influence on this due to required greater degree of hydration under greater water contents and temperature creates a positive influence by accelerating the reaction. Having a precise understanding of the fracture propagation mechanisms when using SCDA is important due to the formation of complex fracture networks in rocks. Several models can be found in the literature based on the tangential and radial stresses acting on a rock mass surrounding an SCDA charged borehole. Those fracture models with quasi-static fracturing mechanism that occurs in Mode I type tensile failure show compatibility with SCDA fracturing mechanisms. The effect of borehole diameter, spacing and the arrangement on expansive pressure generation and corresponding fracture network generation is important in the SCDA fracturing process and effective handling of them would pave the way to creating an optimum fracture network in a targeted rock formation. SCDA has many potential applications in unconventional gas and oil recovery and in-situ mining in mineral processing. However, effective utilization of SCDA in such application needs much extensive research on the performance of SCDA with respect to its potential applications, particularly when considering unique issues arising in using SCDA in different applications.

Cold and moderate ambient temperatures effects on expansive pressure development in soundless chemical demolition agents

This paper explores cool and moderate temperature (2–19°C) impacts on hydration heat and expansive pressure development in two commercial soundless chemical demolition agents (SCDAs). Experimental results showed (1) product-specific, linear relationships between the ambient temperature and time to peak hydration heat; (2) peak hydration heats to be consistently 1.5 times the ambient temperatures at 10–19°C; outside of this range the factor was greater; (3) a linear relationship between peak hydration heat time and the onset of expansive pressure development; (4) a largely proportional relationship between ambient temperature and volumetric expansion of 1.1–1.4 times the original volume.

Enhancing Performance of Soundless Chemical Demolition Agents

Soundless chemical demolition agents (SCDAs) have been used in a variety of circumstances where other more conventional means of demolition were not feasible. When compared with conventional explosives, SCDAs are not yet economically competitive. Research was conducted on SCDAs to examine the possibility of adding an inert material (sand) to the SCDA in order to extend the material. Results show that although the expansive pressure generated by the SCDA is reduced by adding sand, reduction is not commensurate with the amount of sand added. Research was also conducted in order to determine if the workability of the SCDA slurry could be improved by adding a superplasticizer. These tests were conducted at water contents below levels where conventional mixtures were too stiff to effectively deposit them in a borehole. Results show that a superplasticizer can effectively improve SCDA workability and that the resultant expansive pressure is greater than that which is possible without the superplasticizer.

Properties of soundless chemical demolition agents: J. Hinze & J. Brown, Journal of Construction Engineering & Management - ASCE, 120(4), 1994, pp 816–827

Properties of soundless chemical demolition agents: J. Hinze & J. Brown, Journal of Construction Engineering & Management - ASCE, 120(4), 1994, pp 816–827

Properties of Soundless Chemical Demolition Agents

The traditional approach to demolish concrete structures or to reduce the sizes of large rocks or boulders has typically included the use of explosives. The resulting explosions are associated with the obvious risks posed by shock waves and fly rock. These, along with other detrimental side effects of using explosives, have increased an interest in the use of alternative methods to demolish rock and concrete structures. Soundless chemical demolition agents (SCDAs) have proven to be viable substitutes for the use of explosives. SCDAs are powdery materials that will expand considerably when mixed with water. This expansion, when occurring under confinement, generates significant expansive pressures. These pressures are sufficient to break up rock and concrete when the SCDA is confined in a borehole or a series of boreholes. Experiments have been conducted with SCDAs to learn more about those variables that tend to hamper or enhance SCDA performance. Results show that the amount of mixing water and the ambient temperature are the most important variables in influencing the generation of SCDA expansive pressures.