Name: REPAIR OF STONE MASONRY
Uploaded: 2023-10-10
Duration: 12 min 33 s
Description: Good evening everyone. Today, I am pleased to talk to you about an important technical discipline in the field of stone masonry, which is the repair of stone masonry. We will focus on two specific aspects: making "Through Bond" in random rubble masonry and connecting two existing stone walls. Let's look further into the specifics of this discipline..

[Audio] Good evening everyone. Today, I am pleased to talk to you about an important technical discipline in the field of stone masonry, which is the repair of stone masonry. We will focus on two specific aspects: making "Through Bond" in random rubble masonry and connecting two existing stone walls. Let's look further into the specifics of this discipline.. 

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Making ‘Through Bond’ in random rubble masonry Connection between existing stone walls Random Rubble Masonry Wall

[Audio] To construct a through bond in random rubble masonry, select a location in the wall with a one-meter horizontal and vertical distance. Remove the plaster from the area as well as the mortar around the stones, then carefully remove the stone from the wall to create a hole of around 75mm. Insert an 8mm diameter M S bar with hooks into the hole and fill it with 1:2:4 concrete. Finally, cure the surface by sprinkling it with water for 10 days.. 

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1. Making a through bond in random rubble masonry:

First of all select the location in the rubble wall for placing through bond. The location should be so selected that horizontal and vertical distance is 1 m.
 Remove the plaster at the selected location. Remove mortar around the stones  and open up the stones. Slowly remove the stone out of the wall. Create a hole of about 75 mm in the wall. Place 8 mm dia M.S. bar with hooks in the hole and fill the hole with around 1:2:4  concrete. Cure the surface for 10 days by sprinkling water.

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[Audio] Using the "Making Through Bond in Random Rubble Masonry Wall" technique, two existing stone walls can be strengthened by stitching together at the corners. To do so, two 20mm diameter holes must be drilled into the masonry at a 45° angle. The depth of the hole in the longitudinal wall should be up to two times the thickness of the cross wall. Following this, a 10mm diameter steel bar should be inserted into the hole and filled with cement grout.. 

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2. Connection between existing stone walls:

Two stone walls can be strengthened by sewing at the corners. At the junction of  two walls 20 mm diameter holes are drilled into the masonry at 45° angle. The  depth of hole in the longitudinal wall should be up to 2 times the thickness of the  cross wall. 10 mm diameter steel bar is placed in the hole and it is cement  grouted.

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[Audio] Repair of stone masonry walls is necessary, as these constructions are particularly vulnerable to delamination and complete collapse. In order to strengthen them, internal impregnation of a rich cement grout or covering with steel mesh and mortar is necessary. To begin, two to four holes are drilled per square meter area, then cleaned and cement-sand grout is injected at a pressure of 0.1 to 2.5 MPa from the bottom to the top. If the wall contains numerous cracks on both sides, wire mesh should be fixed to it with steel rods at a distance of 300 to 400 mm and a cement mortar is used to complete the surface. For thicker walls, ‘Through Stone’ or ‘Through Bond’ should be placed at 1/3 points in the length and height. Longer walls must be reinforced with a buttress.. 

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Random Rubble Masonry Walls are most vulnerable to a delamination and  complete collapse and must be strengthened by internal impregnation by rich  cement grout in the ratio of 1:1 or covered with steel mesh and mortar. In the method of grouting 2 to 4 holes are drilled per m² area. First of all holes are cleaned by water injection. Then after cement-sand grouted at low pressure of about 0.1 to 2.5 MPa into the holes. The grouting of holes is started from  bottom and proceeded towards up. 	When a wall contains many cracks and cracks are visible on both faces of walls, it  is strengthened by using wire mesh. Plaster is removed from the masonry surface.  Fix wire mesh 0f 50 mm x 50 mm size on both faces of wall and connect them  with steel rods at 300 mm to 400 mm distance. Apply cement mortar on the wire  mesh and finish the surface. In thick wall strengthening is done by placing ‘Through Stone’ or ‘Through Bond’ such through stone or through bond shall be placed at 1/3 points in the length  and height of the wall. Longer walls can be strengthened by buttress.

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[Audio] We have been discussing how to repair walls to prevent dampness. Firstly, we need to understand the concept of plinth, which is the portion of the wall immediately above the ground level to the ground floor level, typically ranging from 45 cm to 100 cm in height. A damp proof course (DPC) is often added to prevent dampness from the foundation reaching the walls through capillary action of ground water. It should be 40 mm to 50 mm thick, made with a 1:2:4 cement concrete mix and a waterproofing compound. In some cases, a 100 mm thick plinth beam reinforced with bars is provided at the plinth level. When repairing these walls, two approaches are used: providing a new DPC layer and pressure injection of resin mortar in holes.. 

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Plinth is the portion of the wall of a building immediately above ground level  to the ground floor level. This height is usually ranges from 45cm to 100cm. In all buildings, nowadays, DPC is provided to prevent dampness going up  the walls from foundation due to capillary action of ground water the  thickness of DPC shall be 40mm to 50mm of 1:2:4 cement concrete with the  waterproofing compound. In some buildings 100mm thick plinth beam with  reinforcement bars is provided at the plinth level.
 Providing new DPC layer Chemical injection in plinth Pressure injection of resin mortar in holes

[Audio] Without greetings, without beginning with Today, and without thanks: I'm going to explain how to repair stone masonry - specifically, how to create 'through bond' connections between existing rubble walls. For installing a new DPC layer in an older building, which was built without a DPC, we cut the mortar bed of the two brick courses above ground level. This is a slow process and may lead to structural settlements and crack formation, so it is rarely used. An alternative is to drill inclined holes in the plinth portions of the walls and inject water soluble silicon. Additionally, silicon paint can be used to waterproof the exterior walls, in order to prevent rainwater from entering the walls. These injections can be done either with pressure or gravity-fed methods.. 

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For providing new DPC layer in an old buildings, which has been built without  DPC, we cut the mortar bed of two brick courses above ground level in stages of  about one meter in length at a time. This method is very slow and may lead to structural settlement and cracking of  walls if the walls are weak. Therefore, this method is rarely used.
 2. Chemical Injection at Plinth In this method, inclined holes are drilled in the walls in plinth portion.  Water soluble silicon is injected in to these holes. Silicon paints are used  for waterproofing of exterior wall portions, to prevent entry of rainwater  into the wall. There are two methods: Pressure injection Gravity feed

[Audio] Removing the plaster up to three to four brick layers above ground level is the first step of the method of repair for stone masonry walls involving 'Through Bonds'. 12 mm diameter holes are bored into the walls up to 2/3t thickness and chemical solutions are injected. For the water-based solution, it is a low-pressure injection and for the solvent-based solution, it is a high-pressure injection. Holes are then finished with waterproof mortar. An alternative method of repair is also outlined in this slide which is the gravity feed method. 25mm diameter inclined holes are drilled into a wall up to 2/3t thickness. Tubes are inserted and chemicals are transfused from containers under gravity until the masonry is saturated.. 

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In this method, plaster of walls up to 3-4 brick layer above ground level is removed. Holes of 12mm diameter are bored into wall up to 2/3t, where = thickness of walls.  The c/c distance of holes is kept about 150mm. These holes should be slightly inclined  downwards. The chemical solution such as polyurethane injection resin or gel is  injected by a pressure pump until it extrudes from the masonry. We usually use high  pressure injection for solvent based solutions and low pressure injection for water  based solutions. The holes are finally finished with waterproof mortar.

 b. Pressure Injection Rising dampness can also be prevented by simple gravity feed method. In this method,  inclined holes of 25mm diameter are drilled into holes up to 2/3t thickness. Feed  tubes are inserted into these holes and chemicals such as dilute silicon are transfused  from the containers under gravity. Liquid is allowed to flow till masonry gets  saturated.

[Audio] We will be discussing the repair of stone masonry walls. To create a connection between existing stone walls, 20mm to 30mm diameter holes should be bored at a depth of 3/5t in a wall from both sides and the c/c spacing of the holes should be 30cm. The holes should be inclined downwards at an angle of 20° to 30°. After drilling, flush out the holes and inject a special mortar composed of cement, styrene butadiene resin or epoxy resin, mixed according to the instructions given by the manufactures. The resin hardens and creates an impervious layer that prevents the migration of moisture.. 

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3. Pressure injection of resin mortar in holes

In this method, 20mm to 30mm diameter holes are bored to a depth of 3/5t in a wall from  both the sides. The c/c spacing of holes is 30cm and inclined downwards at 20° to 30°.  Flush out the drill holes and inject the special mortar from base of hole to upwards using  hand operated caulking gun. This mortar is composed of special cement mortar containing  styrene butadiene resin or epoxy resin, mixed according to the instructions given by the  manufactures. This resin hardens to an impervious layer and prevents migration of moisture.

[Audio] Efflorescence is a common occurrence on stone masonry. It is characterised by a white crystalline substance which appears on the brick or stone's surface caused by the salts present in the construction materials or water used in the making process. This type of damage differs to rising dampness, as it occurs when a wall gets wet and then dries out; the dissolved salts come to the surface and draw water from the atmosphere, creating unsightly patches. To prevent this, the wall should be washed to remove all salt residue, and then repointed and sealed with a quality masonry sealer. Furthermore, the wall should be inspected for any visible signs of damage or deterioration and any necessary repairs should be made.. 

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Efflorescence is the formation of the white crystalline substances that appear on brick wall  surface due to salt in the brick or sand or the water used in its construction. Efflorescence is the  different from rising dampness. When the walls get wet and then dries out , the dissolved salts  come to the surface through the pores. The salts can also absorb water from atmosphere and  form ugly patches on the wall.

[Audio] To combat efflorescence on repairing stone masonry walls made with random rubble, measures must be taken to ensure construction materials such as bricks and sand do not contain salts. A damp-proof course should be installed at the plinth level to prevent the wall from getting moist, and rainwater should not be allowed to wet the wall. Repair begins by removing the plaster from the wall and scrubbing its surface with a brush to remove salts. Mildly hydrochloric acid should then be used to clean the surface entirely. After plastering and drying, the wall should not be exposed to further dampness.. 

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Construction materials such as bricks, water, sand etc. Should not contain salts. Provide DPC at plinth level. Rainwater should not be allowed to moisten the walls.
 For the repair of Efflorescence affected walls, first of all remove plaster from the wall.  Scrub the surface with a brush to clean the surface from salts. Now, clean the surface  with a solution of mild hydrochloric acid. The surface is then thoroughly cleaned with  wet brush and then, plastered and dried. No dampness due to rainwater or from storage  tank or drainage system should wet the wall again so that salts present inside are not  brought to the surface.

[Audio] In this slide we are looking at the repair of random rubble masonry and RCC slab. Patch repair is required on the top surface of the slab and RCC slab with bottom steel corroded may necessitate special repair. Furthermore, any falling off of bottom plaster of the new RC slab may be due to an absence of proper bonding. To guarantee satisfactory repair of such surfaces, it is essential to recognise the precise cause of the damage and take the suitable steps to rectify it.. 

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Patch repair on top surface of slab. Repair of RCC slab with bottom steel corroded. Falling off of bottom plaster of new RC slab due to lack of bonding.

[Audio] Identify and mark out the perimeter lines for the repair with a line at least 100mm outside the worn area. Use a concrete saw to cut a groove of 3mm wide and 6mm deep into the surface. Remove any rust on the reinforcement bar and clean off before the repair area is cleaned by compressed air. Thoroughly wet the area and remove all the water. The area is then ready to accept the filling material.. 

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1. Patch Repair on Top surface of slab Where there are localized depressions caused by wear, which may be either at the middle of a slab or at a joint, these can be repaired as under :
 Identify the patches to be repaired on the top surface of the slab. mark out perimeter  lines at least 100mm outside the worn area. the lines are then cut into the surface using  a concrete saw, making a groove 3mm wide and 6mm deep. Any rust on the surface of  the reinforcement cement bar is removed and cleaned off. Finally clean the repair area  by compressed air. The repair area is then thoroughly wetted and kept wet. All surplus  water must be removed from the area before attempting to place the filling material.

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[Audio] Stone masonry walls that are old can be repaired using random rubble and making 'through bond' connections between them. This is a common practice in modern stone masonry. In this slide, we will be discussing the repair of RCC slab with corroded bottom steel. Corrosion of steel and cracking of the bottom of older RCC roofs is usually caused due to leakage and seepage of water. If corrosion of slab bars occurs in other floor slabs, it is important to identify the cause, whether it be carbonation or chloride corrosion. If it is chloride corrosion, repair may need to be done again in the future.. 

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2. Repair of RCC Slab with bottom steel corroded
 The corrosion of steel and cracking of the bottom of old RC roofs are very  common. Usually in case of the roof slab and the slab under the bathroom,  corrosion of steel takes place due to leakage and seepage of water.
 	If corrosion of slab bars occurs in other intermediate floor slabs, find out the cause  of corrosion of steel whether it is due to carbonation or due to chloride corrosion .  if it is chloride corrosion, then it may happen again after repair.

[Audio] We will be discussing the repair of stone masonry, or random rubble masonry walls. This involves supporting the slab with props to take some of the load, then removing all defective concrete and exposing the corroded reinforcement to its full circumference. A clear gap of 15mm below the steel is recommended and a carbonation test may be conducted to find the depth of carbonation, with concrete removed up to this depth. The reinforcement should be cleaned thoroughly, and extra bars, if required, welded onto the old bars. Afterwards, a protective coating such as cement slurry or epoxy coating should be applied to the reinforcement. After this, a bonding coat should be applied on the surface of concrete, followed by the application of a polymer modified mortar, before the bonding coat dries. Finally, the surface should be cured for at least 7 days using water and painting with cement paint or carbonation resistant paint can be carried out after the surface has dried.. 

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Method: Support the slab by props to relieve some load from the slab. Remove all the defective concrete and expose the corroded reinforcement to its full  circumference. A clear gap of 15mm below the steel is recommended by CPWD. If possible conduct a carbonation test to find the depth of carbonation and remove concrete up to the depth. 	Clean the reinforcement thoroughly and add extra bars, if required, welded to the old  bars. Modern hot rolled high strength steel posses higher resistance to corrosion. Apply	anti	corrosive	protective	passivation	coat	to	all	the	reinforcement	.	The protective coating may be cement slurry or epoxy coating. Apply bonding coat on the  surface of concrete. Now, apply polymer modified mortar before drying of the bond coat. Cure the treated surface at least for 7 days using water. Painting with cement paint or carbonation resistant paint, can be carried out after the  surface gets dry.

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[Audio] When repairing stone masonry, it is important to create a 'Through Bond' in random rubble masonry walls and connections between existing stone walls. This ensures that the plaster at the bottom of a concrete slab does not fall off due to a lack of bonding. To achieve this, one can either use the traditional technique of hacking with a pointed tool so that the depression is at least 3mm deep and spaced no more than 50mm, or use modern construction chemicals for a smoother surface. Doing so ensures a strong bond between the slab and the masonry and is ultimately beneficial.. 

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3. Falling off of bottom plaster of new RC slab due to lack of bonding.
 The falling off of bottom plaster of new RC slab is mainly due to lack of bonding  between the concrete surface and the finishing plaster. Another main reason is the  lack of proper denting or hacking of the bottom of the slab, as per standard  practice. As the recent cements with large amount fly ash gives very smooth  surface on finishing, it is necessary to follow either the old practice of hacking or  use modern construction chemical for bonding concrete surface.
 The old specification is to hack with a pointed tool so that the depression should  not be less than 3mm deep and should be spaced not more than 50mm. The process  of hacking the concrete surface is difficult and time consuming.

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[Audio] I'm going to talk about the repair of stone masonry and the process of making ‘through bond’ in random rubble masonry, as well as the connection between existing stone walls. In addition, I’ll cover the strengthening of RCC slab with overlays and with underlays. The flexural performance of the slabs can be improved with overlays or underlays. The addition of these layers will also increase the stiffness and control the excessive deflection. Slabs with negative moment deficiency will be strengthened by an overlay, while those with positive moment deficiency will be strengthened by an underlay. Thank you very much for your attention.. 

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The flexural performance of the slab can be improved by overlays or  underlays. The addition of overlays/underlays will also increase the  stiffness of the slabs and control the excessive deflection.
 In the case of negative moment deficiency slab is strengthened by overlay  while in case of positive moment deficiency slab is strengthened by  underlays.

REPAIR OF STONE MASONRY

Today, I am pleased to talk to you about an important technical discipline in the field of stone masonry, which is the repair of stone masonry

making "Through Bond" in random rubble masonry and connecting two existing stone walls

Let's look further into the specifics of this discipline.

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To construct a through bond in random rubble masonry, select a location in the wall with a one-meter horizontal and vertical distance

Remove the plaster from the area as well as the mortar around the stones, then carefully remove the stone from the wall to create a hole of around 75mm

Insert an 8mm diameter M S  bar with hooks into the hole and fill it with 1:2:4 concrete

Finally, cure the surface by sprinkling it with water for 10 days.

Using the "Making Through Bond in Random Rubble Masonry Wall" technique, two existing stone walls can be strengthened by stitching together at the corners

To do so, two 20mm diameter holes must be drilled into the masonry at a 45° angle

The depth of the hole in the longitudinal wall should be up to two times the thickness of the cross wall

Following this, a 10mm diameter steel bar should be inserted into the hole and filled with cement grout.

Repair of stone masonry walls is necessary, as these constructions are particularly vulnerable to delamination and complete collapse

In order to strengthen them, internal impregnation of a rich cement grout or covering with steel mesh and mortar is necessary

To begin, two to four holes are drilled per square meter area, then cleaned and cement-sand grout is injected at a pressure of 0.1 to 2.5 MPa from the bottom to the top

If the wall contains numerous cracks on both sides, wire mesh should be fixed to it with steel rods at a distance of 300 to 400 mm and a cement mortar is used to complete the surface

For thicker walls, ‘Through Stone’ or ‘Through Bond’ should be placed at 1/3 points in the length and height

Longer walls must be reinforced with a buttress.

We have been discussing how to repair walls to prevent dampness

Firstly, we need to understand the concept of plinth, which is the portion of the wall immediately above the ground level to the ground floor level, typically ranging from 45 cm to 100 cm in height

A damp proof course (DPC) is often added to prevent dampness from the foundation reaching the walls through capillary action of ground water

It should be 40 mm to 50 mm thick, made with a 1:2:4 cement concrete mix and a waterproofing compound

In some cases, a 100 mm thick plinth beam reinforced with bars is provided at the plinth level

When repairing these walls, two approaches are used

providing a new DPC layer and pressure injection of resin mortar in holes.

Without greetings, without beginning with Today, and without thanks

I'm going to explain how to repair stone masonry - specifically, how to create 'through bond' connections between existing rubble walls

For installing a new DPC layer in an older building, which was built without a DPC, we cut the mortar bed of the two brick courses above ground level

This is a slow process and may lead to structural settlements and crack formation, so it is rarely used

An alternative is to drill inclined holes in the plinth portions of the walls and inject water soluble silicon

Additionally, silicon paint can be used to waterproof the exterior walls, in order to prevent rainwater from entering the walls

These injections can be done either with pressure or gravity-fed methods.

Removing the plaster up to three to four brick layers above ground level is the first step of the method of repair for stone masonry walls involving 'Through Bonds'

12 mm diameter holes are bored into the walls up to 2/3t thickness and chemical solutions are injected

For the water-based solution, it is a low-pressure injection and for the solvent-based solution, it is a high-pressure injection

Holes are then finished with waterproof mortar

An alternative method of repair is also outlined in this slide which is the gravity feed method

25mm diameter inclined holes are drilled into a wall up to 2/3t thickness

Tubes are inserted and chemicals are transfused from containers under gravity until the masonry is saturated.

We will be discussing the repair of stone masonry walls

To create a connection between existing stone walls, 20mm to 30mm diameter holes should be bored at a depth of 3/5t in a wall from both sides and the c/c spacing of the holes should be 30cm

The holes should be inclined downwards at an angle of 20° to 30°

After drilling, flush out the holes and inject a special mortar composed of cement, styrene butadiene resin or epoxy resin, mixed according to the instructions given by the manufactures

The resin hardens and creates an impervious layer that prevents the migration of moisture.

Efflorescence is a common occurrence on stone masonry

It is characterised by a white crystalline substance which appears on the brick or stone's surface caused by the salts present in the construction materials or water used in the making process

This type of damage differs to rising dampness, as it occurs when a wall gets wet and then dries out

the dissolved salts come to the surface and draw water from the atmosphere, creating unsightly patches

To prevent this, the wall should be washed to remove all salt residue, and then repointed and sealed with a quality masonry sealer

Furthermore, the wall should be inspected for any visible signs of damage or deterioration and any necessary repairs should be made.

To combat efflorescence on repairing stone masonry walls made with random rubble, measures must be taken to ensure construction materials such as bricks and sand do not contain salts

A damp-proof course should be installed at the plinth level to prevent the wall from getting moist, and rainwater should not be allowed to wet the wall

Repair begins by removing the plaster from the wall and scrubbing its surface with a brush to remove salts

Mildly hydrochloric acid should then be used to clean the surface entirely

After plastering and drying, the wall should not be exposed to further dampness.

In this slide we are looking at the repair of random rubble masonry and RCC slab

Patch repair is required on the top surface of the slab and RCC slab with bottom steel corroded may necessitate special repair

Furthermore, any falling off of bottom plaster of the new RC slab may be due to an absence of proper bonding

To guarantee satisfactory repair of such surfaces, it is essential to recognise the precise cause of the damage and take the suitable steps to rectify it.

Identify and mark out the perimeter lines for the repair with a line at least 100mm outside the worn area

Use a concrete saw to cut a groove of 3mm wide and 6mm deep into the surface

Remove any rust on the reinforcement bar and clean off before the repair area is cleaned by compressed air

Thoroughly wet the area and remove all the water

The area is then ready to accept the filling material.

Stone masonry walls that are old can be repaired using random rubble and making 'through bond' connections between them

This is a common practice in modern stone masonry

In this slide, we will be discussing the repair of RCC slab with corroded bottom steel

Corrosion of steel and cracking of the bottom of older RCC roofs is usually caused due to leakage and seepage of water

If corrosion of slab bars occurs in other floor slabs, it is important to identify the cause, whether it be carbonation or chloride corrosion

If it is chloride corrosion, repair may need to be done again in the future.

We will be discussing the repair of stone masonry, or random rubble masonry walls

This involves supporting the slab with props to take some of the load, then removing all defective concrete and exposing the corroded reinforcement to its full circumference

A clear gap of 15mm below the steel is recommended and a carbonation test may be conducted to find the depth of carbonation, with concrete removed up to this depth

The reinforcement should be cleaned thoroughly, and extra bars, if required, welded onto the old bars

Afterwards, a protective coating such as cement slurry or epoxy coating should be applied to the reinforcement

After this, a bonding coat should be applied on the surface of concrete, followed by the application of a polymer modified mortar, before the bonding coat dries

Finally, the surface should be cured for at least 7 days using water and painting with cement paint or carbonation resistant paint can be carried out after the surface has dried.

When repairing stone masonry, it is important to create a 'Through Bond' in random rubble masonry walls and connections between existing stone walls

This ensures that the plaster at the bottom of a concrete slab does not fall off due to a lack of bonding

To achieve this, one can either use the traditional technique of hacking with a pointed tool so that the depression is at least 3mm deep and spaced no more than 50mm, or use modern construction chemicals for a smoother surface

Doing so ensures a strong bond between the slab and the masonry and is ultimately beneficial.

I'm going to talk about the repair of stone masonry and the process of making ‘through bond’ in random rubble masonry, as well as the connection between existing stone walls

In addition, I’ll cover the strengthening of RCC slab with overlays and with underlays

The flexural performance of the slabs can be improved with overlays or underlays

The addition of these layers will also increase the stiffness and control the excessive deflection

Slabs with negative moment deficiency will be strengthened by an overlay, while those with positive moment deficiency will be strengthened by an underlay