Fluid Micro-Concrete and My Romance

In Fluid Micro-Concrete and My Romance, Hamid Khan recounts, how in 1996, as a 24 years old graduate engineer, he started developing interest in Concrete that later turned into a true passion and romance.

During the early days after my graduation in Civil Engineering in 1996, I was always amused to watch large concrete pours. My amusement soon turned into romance when I first witnessed the placement of self-compacting concrete (SCC) back in 2002 at level 42 of Shangri-La Hotel on Dubai's Shaikh Zayed Road, at a height of 184 metres – one of the first SCC applications at such a height in the Middle East, Near East as well as Europe. SCC was pumped on four structural transfer beams totalling to 800 m3. The transfer beams on the top with heavily congested steel reinforcement (Figure 2), were meant to support the structure. The use of self-compacting concrete was not very common back in 2002 but it had started gaining tremendous interest and attention in the construction industry. Fosroc proposed a design mix with SSC admixtures to meet the project durability requirements that was approved by the designer.

Working as a Fosroc specification engineer in 2002 in Dubai this was my first encounter with the self-compacting concrete and I was utterly amazed by its ebullient and free flowing demeanour, all the concreters standing beside the pour watching it stunningly (Figure 1). SCC flows easily behind and around the reinforcement steel and into every corner and crevice of the formwork. It is poured in the same way as ordinary concrete but without the need for any vibration. 

Fig 1: SCC pour in progress for transfer beam, Shangri-La Hotel on Dubai - 2002

Fig 2: Congested steel reinforcement detail

Fig 3: After successful SCC pour of 800 m3 for transfer beams at 184 metres height-2002

After attending a number of self-compacting concrete applications in various construction projects, I discovered an element of romance in the SCC as it flows (and dances) with all the constituents in full cohesiveness. Despite the fluidity, the SCC does not have any segregation and grout bleed issues because of its cohesive nature. Flow (free, bound or continuous) is one of the four main factors that make up the dynamics of movement, according to the Effort’s theory by Rudolph Laban - one of the pioneers of modern dance who combined art and science together. I relate self –compacting concrete placement to the three forms of flow (free, bound and continuous).

When flow is free, the dancer would not have big control to stop movement immediately (like the arm of a technician, when spreading anti-slip grains on a primed resin floor or when a dancer makes a grand jete). When flow is bound, the dancer would have control to stop moving at any moment (common in pirouette where the amount of turns depend on the skills of dancer and that requires control). Flow is also generally called as being continuous, which would mean that the course or momentum of movement doesn’t stop.

Natalia Osipova Gissele - (Instagram (natalia_osipova_official)

By using high quality concrete such as SCC and an adequate depth of concrete cover, the risk of corrosion due to carbonation is greatly reduced. Low permeability concrete mix design may be achieved with the addition of supplementary cement materials such as fly ash, slag and micro silica. These similar standards of quality are important while using cementitious repair materials for the remediation of concrete. Repair mortars and engineered protective coatings such as Fosroc Renderoc and Dekguard provide an effective barrier against atmospheric carbon dioxide and other corrosive agents. Fosroc’s latest contribution to the ever changing needs and requirements of the construction industry is the high performance, high strength, environmental friendly fluid micro-concrete Renderoc LA55 Plus, suitable for extra deep pour structural concrete repairs, which flows silently and with less friction and can be placed within the most intricate formwork and heavily congested reinforcement without the aid of any vibration or compaction - with no bleed or segregation.

 A corroded concrete slab in a plant room (below) required a repair solution. Due to the large depth of the repair area and congested steel, conventional mortars were not suitable for the job, as they could have provided an ideal site to initiate corrosion due to poor compaction. For this project a repair mortar that is exceptionally fluid and able to be applied in thick sections to a depth outside normal functional range of repair mortars was required. Fosroc Renderoc LA55 Plus fluid micro-concrete repair mortar was ideal for this application, being an extra high build, free flowing micro concrete, that conforms to EN1504-3, Class R4.

In a building hierarchy, column is a vertical structural element that carries compressive loads and is one of the most critical structural element. Any defect in column during or after construction should be carried out with great attention and care. Fluid micro-concrete such as Renderoc LA55 Plus is most suitable for the reinstatement of concrete columns to restore the critical structural element to its original strength and integrity. Renderoc LA55 Plus obviates the need for compaction and vibration even where access to the repair zone is restricted or where reinforcement is congested.

Materials need to be practical to use in difficult locations and achieve good compaction around the reinforcing steel without any external aid such as vibration. The finished repair must provide protection against corrosive agents such as chlorides and carbon dioxide and must be shrinkage compensated to reduce the risk of cracking. Fluid micro-concrete such as Renderoc LA55 Plus is ideal choice for strengthening of columns, beams and retaining walls using reinforced concrete enlargement system when the project involves defect repairs, change of use and alteration to structure.

References:

1-    Al Gurg Fosroc reaches new highs, (2002), Gulf Construction, https://gulfconstructiononline.com/news/4106_Al-Gurg-Fosroc-reaches-new-highs.html#

2-     Khan, H., (2018), “The Corrosion Conundrum: Durability Risks and Protection to Bridge Structures”, Corrosion and Materials, asset management and coatings feature, vol.43, No.4

3-    Contemporary Dance Terms, https://www.contemporary-dance.org/dance-terms.html

4-    Khan, H., (2019), “Concrete rectification using micro-concrete form-and-pour technique”, Corrosion and Materials, concrete and cathodic protection feature, Vol.44, No.3

 Hamid Khan:

Hamid Khan is past President Australasian Concrete Repair Association (ACRA)-2017-19 and currently a board director.

Hamid is working presently as Product Segment Manager (Repairs and Grouts) – Fosroc ANZ in Parchem.

[email protected]