Cement Grouting for Cracks in Concrete and Masonry
Portland cement grout can be utilized to repair wide cracks found in mass concrete abutments, piers, and masonry substructures. While this technique is successful in sealing cracks within concrete, it does not form a structural bond between cracked sections.
This method’s primary purpose is to fill the gaps created by the cracks, ensuring that water and other harmful substances do not seep into the underlying structure. The injected grout travels through the crevices and fills the voids, creating a barrier that protects the underlying structure from further deterioration.
However, it is important to note that this technique does not restore the original strength of the structure before the crack occurred. It merely provides a temporary solution until a more extensive repair or replacement can be performed. The use of portland cement grout is therefore not suitable for cases where the structure’s integrity is compromised due to significant cracking.
In summary, portland cement grout is a reliable method for sealing wide cracks in mass concrete abutments, piers, and masonry substructures. It serves to prevent further damage by filling gaps and crevices with a strong, durable material. However, it should not be relied upon as a long-term solution for structural repairs, as it does not restore the structure’s full strength and may require additional interventions to ensure long-term stability.
Applications of Cement Grouting for Cracks
When cracks are dormant, it means that they are present in the structure but are not currently expanding or causing further damage. However, it is important to determine the cause of the cracking and take appropriate remedial action to prevent future expansion or worsening of the cracks. This can involve repairing the cracks and addressing any underlying issues, such as inadequate structural support or excessive loading.
Honeycombing refers to the presence of voids or gaps in concrete structures, which can compromise their strength and durability. When honeycombing is present, it is important to assess the extent of the damage and take remedial action to repair or reinforce the affected areas. This may involve filling the voids with suitable materials and reinforcing the structure to prevent further damage or collapse.
In masonry structures, hollow areas can compromise their stability and safety. These hollow areas can occur due to improper construction or deterioration over time. It is important to identify and address any hollow areas in masonry structures to prevent collapse or further damage. This can involve filling the hollow areas with suitable materials and reinforcing the structure as necessary.
Deep leached mortar joints refer to the erosion or loss of mortar between masonry units, which can compromise the strength and stability of the structure. It is important to identify and repair deep leached mortar joints to prevent further erosion and potential collapse. This can involve removing and replacing the damaged mortar, as well as reinforcing the structure to prevent future erosion.
Materials Proportion and Pressure of Grouting
To make grout using Ordinary Portland cement to IS:269, sand and water are required. Admixtures can be added to provide non-shrinkable properties and improve flowability, following the manufacturer’s recommendations. The water-cement ratio (by weight) should be between 0.4 to 0.5, with the lower ratio used for crack widths over 0.5mm.
For a typical mix, 20 liters of water should be combined with 50 kg of cement and 225 gms of non-shrink admixture, such as Conbex 100 (from M/s Fosroc). The grouting pressure should be between 2 to 4 kg/cm2.
Fig: Procedure for pressure grouting of concrete
Equipment for Cement Grouting in Cracks
Cement pressure grouting requires specific equipment to ensure the proper injection of cement grout into masonry. The necessary equipment includes an air compressor with a capacity of 3 to 4 cubic meters per minute and a pressure of 2 to 4 kilograms per square centimeter. Additionally, a grout injecting machine or grouting pump with inlet and outlet valves, pressure gauges, and the ability to inject cement grout up to 4 kilograms per square centimeter is necessary. Modern pumps can even inject grout up to 20 kilograms per square centimeter.
The equipment also includes an airtight pressure mixer chamber with a stirrer to ensure the grout remains in proper colloidal suspension during grouting. Flexible pressure hose pipes are needed to transmit the grout from the pressure chamber to ports embedded in the masonry. To drill holes up to 25 millimeters in diameter, pneumatic or electric drilling equipment is required. Finally, 12 to 20 millimeter diameter G.I. pipes with couplers or lockable PVC nozzles are necessary for injection.