[et_pb_section bb_built=”1″ admin_label=”section” _builder_version=”3.17″ custom_padding=”24px|0px|54px|0px|false|false”][et_pb_row admin_label=”row” _builder_version=”3.0.48″ background_size=”initial” background_position=”top_left” background_repeat=”repeat” custom_padding=”0|0px|50px|0px|false|false”][et_pb_column type=”4_4″][et_pb_text _builder_version=”3.21.1″ background_size=”initial” background_position=”top_left” background_repeat=”repeat” z_index_tablet=”500″]<\/p>\n
Pyrite (FeS2) is a very common mineral. Traces of it are found in the sedimentary rock used to make crushed stone. This stone has been used as backfill for house construction in some areas of Qu\u00e9bec.<\/p>\n
A chemical reaction can cause pyritic backfill to swell. This can cause heaving problems when the backfill is under the concrete slab of a basement or garage. In the presence of humidity and oxygen, pyrite oxidizes and produces sulfuric acid. This acid reacts with calcium carbonates found in the crushed stone. The chemical reaction results in the formation of sulphate and possibly gypsum. Gypsum crystallizes and causes the backfill to swell. This swelling may heave the slab and interior structural supports resting on it. Swelling is usually worse in garages, where the layer of backfill is thicker. On average, it will take about ten years before any perceptible damage is produced.<\/p>\n
Sulphation causes the concrete slab itself to swell and crumble. It can produce swelling up to 15 cm. The humidity under the slab tends to creep upward, transporting the sulfuric acid produced by oxidation. When sulfuric acid comes into contact with the bottom of the slab, the concrete swells from sulphation and starts flaking and disintegrating from the bottom. The swelling concrete expands. The foundation walls restrain horizontal expansion; so heaving usually occurs upwards from the centre of the slab, creating large bulges.<\/p>\n
In some cases, the lateral forces of the swelling backfill will produce cracks in the foundation walls around the garage. This does not usually occur in basement walls, since the pyritic backfill is found only at or below the footings.<\/p>\n
Pyritic backfill comes from quarries with rock containing pyrite or from excavations of public works. The majority of properties affected are located in the Mont\u00e9r\u00e9gie. Cases are also reported in some sites on the island of Montreal and on \u00cele J\u00e9sus. Most cases occur in buildings from 8 to 20 years old. A few older buildings (30 – 40 years old) have also been affected. For residential buildings constructed before 1970, the layer of crushed stone is either non-existent or quite thin. This explains why there are very few problems for buildings constructed before 1970.<\/p>\n
<\/p>\n
[\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row use_custom_gutter=”on” gutter_width=”1″ custom_padding=”0|0px|48px|0px|false|false” _builder_version=”3.3.1″][et_pb_column type=”1_2″][et_pb_image src=”https:\/\/www.montreal-realestate.ca\/english\/wp-content\/uploads\/2018\/09\/Jennifer-Lynn-Walker-Image.png” _builder_version=”3.17″ max_width=”66%” custom_margin=”15px||”]<\/p>\n
<\/p>\n
[\/et_pb_image][\/et_pb_column][et_pb_column type=”1_2″][et_pb_text _builder_version=”3.8″ text_font=”||||||||” text_text_color=”#000000″ header_font=”|600|||||||” header_text_color=”#000000″ header_font_size=”25px” header_4_font=”Alegreya||on||||||” header_4_text_color=”#aaaaaa” header_4_font_size=”25px” header_5_font=”||||||||” header_5_text_color=”#e02b20″ header_6_font=”||||||||” header_6_text_color=”#e02b20″ custom_margin=”45px|||” animation_style=”slide” animation_delay=”400ms” animation_starting_opacity=”100%”]<\/p>\n
Jennifer Lynn Walker has specialized in buying and selling both residential and multiplex properties since 2003. She’s built a strong network of specialist, to give her clients a seamless experience throughout the real estate journey. Founder of\u00a0Montreal Real Estate Investor\u2019s Group, and Jolly Green Homes.\u00a0\u00a0<\/em>How can I help you today?<\/a><\/strong><\/p>\n [\/et_pb_text][\/et_pb_column][\/et_pb_row][et_pb_row _builder_version=”3.17″][et_pb_column type=”4_4″][et_pb_text _builder_version=”3.21.1″ z_index_tablet=”500″]<\/p>\n Can the swelling of backfill have harmful effects on the health of the occupants of the house? In the opinion of the Mont\u00e9r\u00e9gie Public Health Department, the quantities of sulfuric acid are too minute to cause health problems.<\/p>\n Damage attributable to swelling caused by pyrite usually appears 10 or more years after construction. Some swelling may occur sooner if oxidation of the backfill has already started during construction. This may happen if the crushed stone has been exposed to a lot of moisture. Pyritic swelling of backfills will stop when all the sulfur has been oxidized. The speed of reaction will depend on several factors; it takes between ten to forty years to fully oxidize.<\/p>\n Absence of humidity can slow down the swelling of pyritic backfill. In practical terms, the process of oxidation cannot be totally stopped but oxidation over a long period of time could cause less damage than rapid oxidation. Ground level humidity can be reduced by better surface drainage as follows:<\/p>\n If the backfill is still in the process of swelling, the only sure solution to resolve the problem is to:<\/p>\n The repair should be done by professionals specializing in this type of work. It is the most expensive and disruptive option so is usually considered as last resort.<\/p>\n This article is thanks to: www.homeinspectionmontreal.com<\/u><\/a><\/p>\n [\/et_pb_text][\/et_pb_column][\/et_pb_row][\/et_pb_section]<\/p>\n","protected":false},"excerpt":{"rendered":" Pyrite (FeS2) is a very common mineral. Traces of it are found in the sedimentary rock used to make crushed stone. This stone has been used as backfill for house construction in some areas of Qu\u00e9bec.Swelling of the backfillA chemical reaction can cause pyritic backfill to swell. This can cause heaving problems when the backfill […]<\/p>\n","protected":false},"author":2,"featured_media":3408,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"on","_et_pb_old_content":"Pyrite (FeS2) is a very common mineral. Traces of it are found in the sedimentary rock used to make crushed stone. This stone has been used as backfill for house construction in some areas of Qu\u00e9bec.\r\n\r\nSwelling of the backfill<\/strong>\r\nA chemical reaction can cause pyritic backfill to swell. This can cause heaving problems when the backfill is under the concrete slab of a basement or garage. In the presence of humidity and oxygen, pyrite oxidizes and produces sulfuric acid. This acid reacts with calcium carbonates found in the crushed stone. The chemical reaction results in the formation of sulphate and possibly gypsum. Gypsum crystallizes and causes the backfill to swell. This swelling may heave the slab and interior structural supports resting on it. Swelling is usually worse in garages, where the layer of backfill is thicker. On average, it will take about ten years before any perceptible damage is produced.\r\n\r\nSulphation causes concrete to swell and crumble<\/strong>\r\nSulphation causes the concrete slab itself to swell and crumble. It can produce swelling up to 15 cm. The humidity under the slab tends to creep upward, transporting the sulfuric acid produced by oxidation. When sulfuric acid comes into contact with the bottom of the slab, the concrete swells from sulphation and starts flaking and disintegrating from the bottom. The swelling concrete expands. The foundation walls restrain horizontal expansion; so heaving usually occurs upwards from the centre of the slab, creating large bulges.\r\n\r\nDamage to foundation walls<\/strong>\r\nIn some cases, the lateral forces of the swelling backfill will produce cracks in the foundation walls around the garage. This does not usually occur in basement walls, since the pyritic backfill is found only at or below the footings.\r\n\r\nWhat areas are affected<\/strong>\r\nPyritic backfill comes from quarries with rock containing pyrite or from excavations of public works. The majority of properties affected are located in the Mont\u00e9r\u00e9gie. Cases are also reported in some sites on the island of Montreal and on \u00cele J\u00e9sus. Most cases occur in buildings from 8 to 20 years old. A few older buildings (30 - 40 years old) have also been affected. For residential buildings constructed before 1970, the layer of crushed stone is either non-existent or quite thin. This explains why there are very few problems for buildings constructed before 1970.\r\n\r\nPyrite and health<\/strong>\r\nCan the swelling of backfill have harmful effects on the health of the occupants of the house? In the opinion of the Mont\u00e9r\u00e9gie Public Health Department, the quantities of sulfuric acid are too minute to cause health problems.\r\n\r\nTracking progress of the swelling<\/strong>\r\nDamage attributable to swelling caused by pyrite usually appears 10 or more years after construction. Some swelling may occur sooner if oxidation of the backfill has already started during construction. This may happen if the crushed stone has been exposed to a lot of moisture. Pyritic swelling of backfills will stop when all the sulfur has been oxidized. The speed of reaction will depend on several factors; it takes between ten to forty years to fully oxidize.\r\n\r\nTIPS TO SLOW THE RATE OF SWELLING<\/u><\/strong>\r\nReduce ground level humidity<\/strong>\r\nAbsence of humidity can slow down the swelling of pyritic backfill. In practical terms, the process of oxidation cannot be totally stopped but oxidation over a long period of time could cause less damage than rapid oxidation. Ground level humidity can be reduced by better surface drainage as follows:\r\nPyrite and health<\/strong><\/h4>\n
Tracking progress of the swelling<\/strong><\/h4>\n
TIPS TO SLOW THE RATE OF SWELLING<\/u><\/strong><\/h3>\n
Reduce ground level humidity<\/strong><\/h4>\n
\n
Solution<\/strong><\/h4>\n
\n
\r\n\t
\r\n\t