Specification and Proposal For Cement grouting & PU grouting work at Railway Underpasses,

System for cementious grouting:

Application of cement based Nozzle Grouting : Supplying & applying of cementitious nozzle grouting with high strength cebex 100 inside nozzle fixed 300 mm centre to centre inside the retaining wall,slab & raft foundation.

Advantages of cement grouting Grouting

Cementitious grout possesses the Following advantages:

Gaseous expansion system compensates for plastic shrinkage and settlement in properly designed cementitious grout.

Reduced water/cement ratio mixes in the grout mix ensures low permeability and long term durability in service.

Gives grout high fluidity with low water/cement ratio, thus making placement or injection of the grout easy.

No metallic iron content to corrode and cause staining or deterioration due to rust expansion in the grout.

Composition allows high early strength development in grouts, without the use of chlorides.

System for PU grouting:

Introduction of the Product: -

Nitofill WS60 and Nitofill UR63 are polyurethane grouts are designed to react with water and expand in- place, forming a tight, impermeable, elastomeric seal that immediately stops the flow of water. Polyurethane seals in three ways:

First, it forms a chemical bond to the concrete surface area;

Second, it forms a mechanical anchor by entering the pores and voids; and

Third, by expanding, it forms a compression seal within the crack, joint, or void to act as a waterstop.

Step by Step methodology for Application:-

Preparation:-Prior to the injection procedure, the nature of the structure, cracks, the hydraulic and hydrostatic conditions, the water quality, etc, must be examined. Special attention should be paid crack (wherever developed) characteristics such as their course, width, state, crack edge and the crack accessibility.

Drill injection holes:- Before drilling the injection holes, locate rebar and conduit and plan the hole pattern to minimize damaging the bit during drilling. Determine.

• Hole diameter

• Hole depth

• Angle of drilling

Drill hole spacing

Injection holes for most jobs are 1/2 to 5/8 inch in diameter, the angle of drilling is 45 degrees to the concrete surface, and the depth of the hole where it intersects the crack is a minimum of one-half the concrete thickness. For very thin and thick concrete sections, the angle of drilling and hole depth change. For concrete sections less than 6 inches thick, drill the injection hole perpendicular to the concrete surface and directly into the crack. This minimizes spalling created by drilling inclined holes in thin sections. For concrete sections greater than 36 inches thick, the hole depth can be held constant at about 18 inches. However, the pump must supply sufficient pressure to force the grout to the far side of the crack

install packers:- Insert the packer into the drill hole. If the packer can't be pushed into the hole, tap it in. Tighten the packer with a deep-set socket wrench or open-end wrench. Occasionally, it may be necessary to secure the packer with a quick-set cement or moisture resistant adhesive .

Flush the crack/Joint with water:- Sometimes it's necessary to flush the crack with water to remove debris or drill dust. Some manufacturers recommend flushing dry cracks with water to help provide enough water to fully react the grout. Connect a water hose and pump to the packer. A grout pump will work. Typical pump pressures needed to flush water .

Inject grout:- Before injecting grout, make sure the grout pump is ready. If the grout pump was used to flush the crack with water, make sure all the water is completely removed. Also, make sure that washing agent used to clean the pump before grouting has been purged from the hoses and pump. Some contractors use a low pressure pump for flushing and a high-pressure pump for grout injection. Begin grouting at the lowest packer on a vertical crack or at the first packer flushed for a horizontal crack. Once grouting has begun, it may take several minutes for the grout to appear at the crack face. Start pumping at a low injection pressure, about 500 psi. If grout does not appear at the crack face or another injection port, raise the pressure slowly in 100 psi increments. Continue increasing the pressure until the grout appears or safe operating pressures are reached. Never exceed safe operating pressure because this can cause the crack to widen or another crack to form. If the grout flows freely from the crack, stop injection and wait a few minutes for the grout to set. This serves as a surface seal and the injection continues until the grout appears from a packer. If grout continues to flow from the crack, even after waiting 5 to 10 minutes, the crack will have to be surface-sealed. Use a quick-set cement, allow it to cure for a couple of minutes, then resume pumping. When pumping the grout properly, the operator will notice:

• Water flowing from the crack, then

• Water and grout flowing from the crack as a foam mixture, then

• Pure grout flowing from the crack

Continue pumping until the grout reaches the next packer. Then move to that packer and resume injection. If no grout appears but the safe operating pressure has been reached, stop pumping and move to the next packer to resume injection. After injecting a couple of packers , return to the first packer and inject again. Some of the packers will take more grout, filling up more of the crack and creating a higher density crack filler. Some contractors reinject the packers up to three times.