Experts are sometimes left perplexed in instances where a “well-built” concrete structure fails despite all evidence indicating that the correct materials and procedures were used in its construction.
Closer investigation however, often reveals a different picture in which blind trust was placed in third-party suppliers’ and whose products were incorrectly classified and did not perform as they should have in the first place. Once delivered on site and accepted by the responsible person, the rest of the crew would have no reason to believe that a problem existed and would continue unaware that a serious breach had taken place.
According to Nico Pienaar, director of two central industry associations responsible for supplying concrete to construction sites, the Aggregate and Sand Producers Association (Aspasa) and the Southern Africa Readymix Association (Sarma), such failures are mostly as a result of the “missing critical link” between regulated and unregulated products or scrupulous or unscrupulous suppliers.
Digging for answers
“We refer to this as the missing link, in which the construction firm is unwittingly responsible for the failure. Even though in their opinion they dotted ever “I” and crossed every “T” they missed a step that led to the eventual failure of a structure. In order to prevent this you need to look at the overall integrity of the concrete that will be used to build a structure.
“One has to ask yourself if the integrity is in any way compromised or if you are unsure at any point along the way. For example, is the cement really from a trusted local supplier that has met every requirement of our cement regulations for quality etc. Is the sand and aggregate being used by the supplier traceable to a credible supplier (and source), is its composition adequate and sized correctly. Is the chemical composition of admixtures, extenders and other components of the concrete correct and are they being used correctly. Is the readymix supplier a member of Sarma and do they have Sarma accreditation?
“Only once this has been established ordering should commence, but, this is by no means a guarantee that the concrete won’t fail. The next step is equally critical and relies on procedurally correct sampling and testing to be conducted to see if it will indeed perform as expected,” says Nico.
Remedy at hand
He says controls and systems are simple to implement to ensure a high level of certainty can be built into our concrete structures. It begins with procuring materials from reputable suppliers that are audited and accredited by their own industry organizations, such Aspasa and Sarma. Next, materials should be correctly batched by well-trained staff that know the exact specification and intended usage of the concrete being prepared.
“Insist on quality cements products from local suppliers and where possible steer away from cheap imported cement and cheap inferior extenders. Concrete is a very sensitive product because its made out of aggregate, sand cement and water and extenders and if the ratios and timing is not right it is – simply put – wrong.
“If we are to build strong foundations for the next generation to build upon, then we need to leave a legacy of quality construction and infrastructure, as well as sustainable development and the creation of jobs in the local industry.
“By supporting local cement manufacturers and suppliers of aggregate and readymix that are accredited and from areas surrounding the construction site, we are guaranteeing quality and are directly contributing to a sustainable environment and the creation of jobs in the area in which the project is being undertaken,” Nico adds.
He concludes that management and leaders of construction firms are ultimately responsible for the quality of work carried out by their firm and therefore need to ensure that all critical links are checked and addressed to eliminate the chance of problems happening in future.
Aspasa, Nico Pienaar, Tel: (011) 791 3327, Fax: 086 647 8034, Email: email@example.com, Web: www.aspasa.co.za