According to the author, the modified concrete is less susceptible to cracks as waterproof substances were pre-mixed into the structure during the initial production stage achieving a strong foundation. In addition, the author explains that minor defects such as cracks can be easily identified and rectified by adopting the polyurethane grout injection from the bottom of the structure without disrupting the plants on the roof. In comparison with the installation of the original concrete, the thin layer of membrane being applied on the surface of the concrete is more prone to wear and tear due to the prolonged exposure of the weather. Hence, additional complicated repair works are required after the completion stage.
The author also highlights that the installation of the modified concrete will cause reduction in the design time as the application of the membrane has been omitted. Thus, shortening the construction process with the earlier commencement of the building works. Moreover, subcontractor specialise in membrane works is no longer needed that resulted in both labour and material costs saving.
I agree with the author that the installation of the waterproof concretes results in construction cost and time saving to a certain extent as the review states that the waiting time for the concrete to cure has been cancelled prior to the application of the membrane. However, there are other factors that the architect and building contractor have to take into consideration such as planning in advance regards to purchasing order for the production of the materials and the installation process.
In a supporting article written by Ken Hooker (2012), the water resistance performance of the structure can be improved significantly with the placement of the concrete with admixtures of waterproof substances that reduced its permeability. Ken Hooker provides reference in a case study project at Eastern Michigan University in Ypsilanti where waterproof concrete was installed on the green roof slab of the building. Furthermore, Ken Hooker states that the effort of making the concrete itself water resistance results in labour and material costs saving as other waterproofing method such as application of membrane was not required. It supports the feature that the implementation of the new concrete technology is cost and time efficient to some extent.
On the other hand, based on my working experience as a construction project coordinator in 2013, the production period of the waterproof concrete may be longer compared to production of the original concrete as additional step of premixing the waterproofing substances is included in the manufacturing process. Therefore, contractor need to allocate additional time to prevent lateness in the delivery of the new materials to site so as to meet the project timeline. During the installation process, additional time is required for detailed planning of hoisting and placing the modified concrete as the material has extra loads due to its waterproofing mixtures. As such, both pre-installation and installation period may require more time in project management and planning process which incur additional man-hour costs.
In conclusion, the review (“The Concrete Advantage,” n.d.) is more reliable when the author describes its simplification of the maintenance process than the cost and time efficiency of the new concrete methodology. Nonetheless, waterproof concrete can be relatively cost and time efficient with detailed planning and strict coordination during the initial stage of the construction.
References:
[1] The Concrete Advantage: Waterproof
concrete makes green rooftops an even better investment for society and owners.
(n.d.). Retrieved from http://www.greenrooftops.org/advantage.html
[2] Ken Hooker. (2012,
August 13). Waterproofing Admixtures For Concrete. Retrieved from http://www.concreteconstruction.net/howto/materials/waterproofing-admixtures-for-concrete_o
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