Introduction

Non-Explosive Demolition Agents are the one which can be used to demolish rock and concrete structures in dust and noise sensitive areas and places close to inhabited areas, gas pipelines, roadways or other areas where the use of explosive would generate significant safety risk.

In India these are extensively being used in granite/marble/sand stone quarrying industry, and termed as ever best method techno-economically because of its unique characteristics of application results. It is also being in use for demolition of concrete structures in projects like Metro Rail Station, Power Plant Developments, Process Plants, and for rock demolition in land development, boulder demolitions in road constructions, etc.

Technical Information:

NON-HAZARDOUS CHEMICAL COMPOUNDS (% by weight)

We at Prudent Rock Demolition Solutions have actively engaged in developing Non-Explosive Chemical Demolition Technology in Infrastructure and Mining Industry across India. We with registered office in Chennai, Tamilnadu, supplying Expansive Mortar throughout the India under the brand name of ‘ECO-CRACK’, SPLIT-AG, SINO-CRACK. Our product has got great performance appreciation from various Mining and Infrastructure Companies Located in Andhrapradesh, Tamilnadu, Karnataka, Maharashtra, West Bengal, Assam, Orisaa, Himachal Pradesh and Rajasthan etc.

1. Base Material:

The base product in the compound is Calcium Oxide and is prepared from Over Burnt Lime. Calcium Oxide has a natural property of heat generation on Hydration (An Exothermic Chemical Reaction with H2O). All other remaining composites are naturally possessed with base material when extracted from earth crust.

2. Principle of Working:

When a material (dry) made to fine powdered form measuring certain volume, on through hydration (28-32% w/w of CaO) of powder its physical volume reduces than initially measured volume due to hydro bonding. At this min volume state chemical would be applied in drilled holes. Due to exothermic chemical reaction between Calcium Oxide and water significant internal heat energy will be liberated which leads to evaporation of H2O from the mixture and tries to attain dry state. During evaporation/dehydration process, it also tries to attain its original volume, which is termed as Expansion Process in a circumferentially constrained hole. This expansion energy developed from multi points together implies to create fractures on rock/concrete.

We pour the hydrated mix into drilled holes in minimum volume state. After filling the mix, within 10-15 min evaporation starts because of internal heat energy developed there by expansion of chemical happens in a constrained hole. It physically appears as blow shots (1-2 blows per Hole). That expansion stress is more enough to create fractures in the structure.

In the expansion stress, Major component is Hoop stress and Minor component is Normal stress. Hoop stress acting circumferentially will lead to create fractures, and normal stress will release in upward direction with some chemical spill out at top face nearby hole as shown in figure below.

We say again that it is not a molecular expansion; it is wholly a volumetric expansion all together due to dehydration. Moreover, it is nearly homogeneous medium with concrete. At work stations during concrete demolition with chemical application, we practically noticed that expansion process happening max of 12 inches in downward direction in a period of 12 hours after application.

3. Change in Mix ratio & its Implications:

As per practical analysis and purity of calcium oxide its min volume observed at 28-32% (w/w) water. When we add less than 30% water proper hydration does not happens and it will net get flow ability characteristics to full fill the aim of the Job. Improper hydrated mix in a very few minutes physically appears as blowing steam and powder solution. Proper eye protection must be wore during the mixing process.

If we add more water, the amount of heat energy that liberates during the reaction process may not be sufficient to evaporate the mixed water and remains in wet state with very less volumetric change or sometimes no change there by no expansion.

So, always mix 30% w/w to get better results and contact your supplier/manufacturer for any changes if needed. Usually it takes 10-15 min for reaction initiation, so the mix must be poured in drilled holes within 10-15 min. else it will create blow in container itself changing wet to dry state.

No Packing required for this product after filling. During dehydration it becomes self packing.

The whole process is internal chemical reaction with physical change; it does not react with work piece like either ROCK or CONCRETE. There is only Volumetric Change, Which is termed as expansion energy to create fractures.

Fracturing Time depends on tensile strength and compressive strength. Rock is easy to crack as it is less tensile and concrete takes time as it possesses high compressive strength.

4. Crack Propagation and Its Limiting for concrete structures:

Crack propagation mainly depends on drilling strategy and hole position from nearest free face. Maximum Crack Propagation is up to 15 times to diameter of the hole. In case of free boulders crack will take the nearest free face and ends, while in case of in-situ rock crack will form 80% of total drill depth only bottom 20% will not give result due to high shear stress limit.

Concrete Structures, being a porous medium with significant compressive strength, in case of free structures fracture happens up to drilled depth only and then Crack propagates/weakens towards free face. However we consider crack propagates in a sector region sub tending a max angle of 45 Degrees to Horizontal Plane as shown in Figure. We keep 6-8 inches mean hole distance and Line-Line distance for RCC Structures and similarly 10-12 inches for PCC Structures. It eases for chipping with breakers with high productivity at the same time It is essential to limit the cracks to safeguard the structure also.

In case of RCC Wall demolition to a certain level there are two different drilling strategies being used for safe demolition.

Drilling Strategy:

  • Inclined downward directional drilling with less than 45 Deg with H.P and it is on vertical face. (OR)
  • Vertically downward drilling with 90 Deg with H.P and It is on Horizontal Face.
  • In case of vertically down drilling to arrest the crack propagation, blank hole drilling will be done at the bottom most required level horizontally. No chemical would be charged in these holes. While in case of inclined drilling crack propagation will happen horizontally so no need of any blank holes as chemical strength is not more than 150mm radius.

Application Procedure and Requirements

Chemical demolition technique involves a). Drilling b). Mixing c). Filling.

a) Drilling

Among available drilling techniques pneumatic drilling setup and mechanized hydraulic drilling setup are in practice for productive results.

b)Mixing:

Expansive Mortar is a powder that must be mixed thoroughly with clear water in a ratio of 30 % (w/w) say 1.5-to-1.7 Lit for 5 Kg bag. We insist users to carry out a test in practical with various proportions from 1.5 to 1.7 Lit per 5 kgs (Most using proportion is 1.6 Lit/5Kg) to decide the correct proportion for better results. Gradually add the powder to water and stir all the time to obtain a smooth and LUMP-FREE mortar. Excessive water may delay the cracking process and less water may lead to starvation during reaction. Users are requested to follow the instructions mentioned on the bag.

c) Filling

After mix has been prepared it should be poured into the holes. as reaction starts quickly, pour the Expansive Mortar within 5-10 min after mixing. During filling do not maintain any delay in any particular hole Otherwise it may lead to non-homogeneous reaction resulting throw out of chemical. No Capping required. Do not keep any obstruction on Hole. For further information feel free to discuss with us.

Free Surface

It is one of the significant factors that play an important role in cracking process. As expansive pressure acts towards free surface, it is necessary to ensure free surface at least at one edge (Other than Top face and Front Face) for a bottom free rock/boulder. If the rock/boulder is routed into the earth surface please email us photograph for the suitable Hole Drilling pattern to demolish the big boulder/rock rooted inside the earth. We have dedicated geologists and rock engineers to serve you the best.

Cracking Mechanism

After the mortar has poured into holes drilled on rock or concrete, the expansive stress gradually increases with time, the material to be cracked undergoes a process of:

 Crack initiation

 Crack propagation

 The increase of crack width

The mechanism by the expansive stress of “Expansive Mortar” is shown in Fig. 1. Cracks initiate from an inner surface of the hole due to circumferential stress that develops during expansion process while hardening. The expansive stress continues even after the appearance of cracks, the cracks propagate and also new cracks initiate during the process. Usually, For a single hole, 2-4 cracks initiate and propagate either towards nearest free surface or nearest hole. When a free surface exists, the crack, as shown in Fig. 2, is pushed apart mainly by the shear stress, and a secondary crack also arises from the bottom of the hole, running toward the free surface. Please note during the initial reaction process (i.e., 30-60mis) there are chances for blow-shot releasing gases evolved in the hydration reaction. So, during that period we insists workers to stay away at least 10 mts from Job place. Peeping onto the hole strictly prohibited.

Fig. 1 Fracture mechanism of Expansive Mortar Application

Safety Precautions

Even though it is safe demolition technique, as the product is chemically highly base in nature with pH-13++ it is necessary to take proper care while handling and applying. Being safe is prime important to do a safe demolition. Always wear hand gloves while handling and wash hands thoroughly after use. Ingestion this product causes severe damage to digestion system of human body. If it comes in contact with eyes do not rub your eyes and rinse with clear water several times and contact an eye doctor at the earliest to avoid major damage to eye. Also avoid contact with skin as it will react with skin rinse all affected parts thoroughly.

  • Always wear nose mask to avoid inhalation into breathing system.
  • Wear safety Goggles, Rubber Gloves, Long sleeve clothing and Helmet while handling, mixing and pouring Expansive Mortar and be a safe applicant.
  • Do not peep into hole till at least one Hour as there is chance of blow shots releasing the evolved gases. So please maintain some distance from job site for at least 1 hour
  • Ensure that portion that to be cracked should not comedown/roll down/slide down into active work place after got cracked.
  • Do not park equipments besides structure/rock on which chemical demolition.
  • Keep away from children.