San Jose has seen a great deal of new development over the years, in both the commercial and residential sectors. This growth has kept area construction professionals busy and weathering the challenges posed by San Jose’s unique Bay Area microclimates. Commercial concrete contractors – San Jose, in particular, have a difficult job, as not only do most of the new structures require concrete for many of their foundational structural elements, but also the city’s weather can require additional precautions and strategies be implemented on projects during the curing process of the concrete.
Importance of controlled curing
Concrete curing is the process by which concrete gains its strength, and contrary to intuition, this does not mean the concrete is hardening by drying. In order to achieve the designed characteristics of the concrete, which is engineered through the materials and their ratios in the concrete mixture, the placed concrete must be allowed to cure in specific conditions. Generally, concrete takes 7 to 14 days to cure and should maintain greater than 80% relative humidity within the concrete and temperatures greater than 50 degrees Fahrenheit. In short, the placed and finished concrete should be kept warm and wet until the curing process is complete. If these conditions are not met, the structural integrity of the concrete can be compromised and lead to cracked, weak, or chalky concrete.
Challenges posed by the climate
The Mediterranean climate of San Jose means the city’s weather is on average hot and dry. The high temperatures and low relative atmospheric humidity can inadvertently speed up the curing process if proper steps aren’t taken to mitigate the rapid evaporation of moisture from the curing concrete. There are several strategies concrete contractors employ to avoid this. First, it is recommended that aggregates and mixing water are cooled before adding them to the concrete mixture and that reinforcing material and formwork is moistened before placement. Additionally, admixtures that accelerate curing can be used, and the consistency and method of placement of the concrete can be designed to encourage rapid placement and consolidation, as with shotcrete. After the concrete is placed and finished it should be kept wet either by puddling water on the surface or covering the slab with burlap and continually moistening the covering. Concrete contractors can also enhance the logistics of their work by ensuring the project has adequate staff to place, finish, and aid the curing process in a timely manner, or by scheduling the work during a time of day that has more favorable weather conditions, such as early morning or at night.