Construction World January 2015

CONSTRUCTION WORLD

JANUARY

2015

PROJECTS AND CONTRACTS

Most of the roads used by the local

people to access their homes are

constructed of gravel, often so

poorly maintained that no gravel is

evident. Following heavy rainfall, the in-situ

clay material is exposed, especially on the

steeper gradients, which are rendered inac-

cessible to most vehicles.

Innovation

Paving these roads was not economically

viable due to the steep gradients and the

prohibitive costs of asphalt paving. Engi-

neers from the KZN Department of Transport

(DOT) made the decision to resurface two

steep road sections using Kaytech’s Multi-

Cell 100 mm filled with ready-mix concrete.

This solution was possible because the

roads here are trafficked mostly by light

motor vehicles and pedestrians.

Since the Multi-Cell system had been

successfully installed on a section of a

District Road at Vulindlela (adjacent to

Edendale) in 2006 and at Unit H in Edendale

in 2007, the DOT engineers were confident in

specifying the system in this case. Although

Multi-Cell has been around for some time, it

has not been used extensively for road resur-

facing. Other more popular uses include

effective erosion protection treatment for

hydraulic structures, as well as slope protec-

tion and load support. However, it is proving

to be an innovative alternative to reinforced

concrete roads, negating the excessive cost

of steel reinforcing.

Working within tight budget constraints

and the limitations of an existing 20 m

fixed road reserve, the regrading of the

28% incline and widening of the sharp

horizontal curves was particularly chal-

lenging. After conducting a feasibility study

and having considered other options, a

600 m section at 19% design grade was

constructed using Multi-Cell geocells infilled

with 25 MPa concrete.

Multi-Cell is a honeycombed, cellular

structure manufactured from strips of

a coated slit film. This woven polypro-

pylene tape is stitched together to form

three-dimensional diamond shaped cells.

It is used as an in-situ shuttering to

cast continuous, interlocking concrete

paving for road or canal construction.

Multi-Cell provides a high cell wall/infill

interlock as well as high tensile strength

and seam strength. It is usually supplied in

standard 5 m x 10 m panels but, to accom-

modate the narrower, single-track roads

on this project, Kaytech specially manufac-

tured 4 m x 10 m panels. Livestock and stray

animals walking through the wet mix before

it was properly cured posed a problem for

the contractor, but this was rectified by

manually filling the footprints with concrete

once the concrete had set.

Environmental impact

This project and others like it in Unit H of

Edendale demonstrate the potential of using

concrete-filled geocells for upgrading and

improving road networks into previously

inaccessible steep environments. Multi-Cell

is rot-proof and resistant to most low-con-

centration chemicals and ultra violet light,

thus it is sustainable, requiring minimal

maintenance. It is lightweight and has low

packaged volume in relation to the installa-

tion area, posing a low transportation carbon

footprint in comparison to alternative solu-

tions. Being flexible, Multi-Cell conforms to

existing environmental surfaces, thereby

reducing many of the costs inherent in using

steel as concrete reinforcement.

Local impact

The Multi-Cell system proved to be the most

economical technical solution for this Eden-

dale roads project, providing an ideal oppor-

tunity for labour intensive construction (LIC)

techniques. It was the first Multi-Cell project

undertaken by the contractor, Okuhlekwethu

Developments, who installed the product

according to Kaytech’s installation guide-

lines. The patented Tension Frame makes

the Multi-cell quick and easy to install, thus

unskilled labour was employed by simply

following Kaytech’s installation guidelines

and receiving on-site training by a foreman.

24 members of the local community were

employed and trained to install the Multi-

Cell system in accordance with the Govern-

ment’s policy on the LIC and Extended Public

Works Program (EPWP) programme.

The local labourers employed were

MULTICELL ROADS

Edendale township, situated in the southwest outskirts of

Pietermaritzburg, KZN, is a large area dominated by steep hills

and valleys. It was here that Kaytech’s Multi-Cell was chosen

to solve a resurfacing problem for two of the township’s

dilapidated roads. Kaytech’s Paul Lombard was on site to offer

specialist supervision.

given DOT standards and kitted out in PPE

gumboots, gloves, and reflective vests in

compliance with Health & Safety standards.

No health and safety issues were reported on

this project.

The completed road ready for foot traffic and

small vehicles.

Application is simple: a section of geocell road

being filled with concrete.

Local labour was used to fill the Multi-Cell road