TECT B is a non-cementitious, clay based grout which cures to form a very dense and impermeable plastic clay. Since the TECT B grout does not “set” in the conventional sense, an unexpected delay in completion of the bottom cut would not be an issue. TECT B grouts are provide a highly effective hydraulic barrier from the moment the grout is introduced into the ground. When TECT B grout is first introduced into the excavated subterranean pathway, it coats the wall with millions of microscopic sheets which form a seal to plug off the permeability of the soil. The hydrostatic head of the dense liquid grout provides a positive pressure from the grout side of this barrier. This is like the filter cake which forms on the walls with the bentonite slurry during slurry trenching but faster and to a more impermeable. After the barrier if formed the grout does not remain liquid indefinitely. As time passes the grout will lose moisture to the environment until it reaches vapor pressure equilibrium with the environment. The barrier’s properties continue to improve over a curing period of months and years. Eventually the grout becomes a stiff but still plastic material somewhat like modeling clay mixed with gravel. TECT B grouts remain fully self healing as they cure and thus have no issues of thermal expansion or stress cracking. We believe that this makes it very attractive for construction of barriers which are 800 feet long. Due to the overburden force of the block pressing down on the grout, it will automatically seal any breach, gas pocket, rodent hole, ant hole, or ground shift. The high pH and irritating additives added to the grout will discourage living creatures from bacteria to animals from disturbing or burrowing into the material.
This grout can also be enhanced to further increase its ability to absorb and neutralize organic liquids and chlorinated solvents. TECT BZ contains zero valiant metals and other compounds which actually react with and treat many organic solvents. Unlike funnel and gate concepts which can fail as they become clogged and groundwater bypasses them, an EarthSaw applied TECT BZ surrounds the source on all sides and can not be bypassed.
A TECT B type grout will “cure” over a period of months or years. Laboratory tests of field cured TECT B grout excavated from previous field tests indicates that the permeability of the cured grout is less than 10-8 cm/sec. TECT HG grouts tested by Brookhaven National Laboratory in 1997 (BNL-64958) had permeability < 0.2 x10-10 cm/sec compared to Portland cement that had permeability of 1 x 10-7 cm/sec. Hardening TECT A grout material has a very low heat of hydration and is designed for massive placement with little shrinkage. TECT B grouts have no heat of hydration and are able to plastically deform even after they are fully cured.
Type C TECT grout is a lower cost grout intended only for small tests. It simulates many of the features of TECT A grouts but it’s performance properties are more limited. It lacks self healing properties, acid resistance and is not quite as strong or impermeable.
We propose to use the non-hardening TECT B grout in this demonstration. The TECT B grout is the most ideal for the 749 pit area since it is unlikely to be damaged by earth movements or future excavation work. Also the very long cure time and high lubricity of TECT B help facilitate cutting extra wide barriers in a single cut. TECT B grout has excellent sealing properties and is well adapted to avoid loss of the grout into a permeable formation which may be encountered at depth.
The EarthSaw technology includes a method for placement of a HDPE synthetic liner inside the barrier once the block of earth has been severed and is floating on the grout. The addition of such a liner in the grout would no doubt answer most critics worries about the perfection of the barrier material but is considered overkill by others since two feet of 10-8 cm/sec permeability grout is a substantial barrier. The mechanics of this method at present, require that the two opposite end sections of the isolated block taper gradually to the surface rather than being vertical. Due to the limited perimeter of 749 pit vertical wall barriers appear to be most suitable for this site. Therefore we are limiting the present proposal to demonstration of the buoyant barrier principal on a large scale rectangular block and we do not plan to place a liner under it. It should be noted that addition of a synthetic barrier to a vertical wall containment structure is believed to be feasible but would require us to design special hardware which would add needless complexity to this project. We would of course be glad to discuss adding the HPDE liner to future demonstrations.
Technology available for license.
Carter Technologies Co.
9702 Garden Row Drive
Sugar Land, TX 77498
Phone (281) 495-2603