ARC313 Building Code II

Review What is the minimum bearing pressure allowed for soils to support foundations? 75 kPa How can you tell by looking at the excavation of a project if you may have questionable soil conditions? garbage, discolouration, water

Review If all soil conditions are adequate what table in part 9 gives you the minimum footing sizes? Table What is the minimum thickness of a footing and what clause gives you that information? 4” / 100 mm (1)(a) Concrete with a high water to cement ratio is better than low water to cement ratio? false, because it dilutes the mix

Suitable Materials The materials used in making concrete will influence: workability, strength, durability, appearance and cost Materials that should not be used in the mix of concrete are: shale, chert type aggregate soft porous materials dirty water

Adequate Curing  Effect of Moisture on the Strength of concrete

Adequate Curing  Effect of Temperature on the Strength of concrete

Failures in Concrete Excessive Shrinkage causes improper mix design too much water in mix inadequate curing lack of protection low humidity high winds high concrete temperature low air temperature (freezing)

Failures in Concrete Excessive Shrinkage remedies using minimum amount of water additives  super plasticizers  lower water amounts, but allow good workability  air entrainment  lower water amounts, but allow good workability  reduce segregation avoid high concrete temperature use larger aggregate reduces amount of water protect from sun, wind and rain control joints in walls and slabs

Failures in Concrete Cracking causes overloading backfilling lack of lateral support heavy equipment too close to the wall shrinkage of the concrete bearing of soil freezing of fill material

Failures in Exterior Concrete Sidewalks, driveways, patios, garage slabs. Problems shrinkage, cracking, movement / tilting, spalding / surface popping

Failures in Exterior Concrete Possible remedies remedies from previous for shrinkage and cracking compaction of material below concrete saw cutting to allow concrete to crack at specific locations instead of randomly incorporate reinforcing steel reinforcing bars W.W.M. (welded wire mesh) adequate drainage to prevent frost heavage proper concrete strength with 6 to 8% air- entrainment avoid over finishing keep moisture in concrete by misting, wet burlap wetting granular fill before placement

Additives super plasticizers good for when pouring walls, using concrete pumps allows the concrete to be placed with little movement, vibration prevents excessive water bleeding and or segregation  CAUTION when using with other additives hot water used during cold weather to help prevent from freezing

Additives calcium chloride helps to evaporate water from concrete  which helps during cold weather to prevent freezing  CAUTION when using with steel reinforcing will cause corrosion and possible surface cranking cement types see appendix A in back of your manual