Construction World April 2021

CEMENT & CONCRETE

POLOKWANEWASTEWATER TREATMENT PLANT SUPPLIEDWITHHDPE PIPES

Waste water treatment plants play a crucial role in the removal of contaminants from wastewater and sewage in order for its conversion into an effluent that can be returned to the water cycle in an environmentally friendly way or to be reclaimed for other purposes. It is a critical process in the supply of safe water to local communities.

R ocla’s HDPE vertical cast pipes were specified for two phases of the Polokwane Waste Water Treatment Project due to the quality of the pipes and the technical support Rocla provides. The project commenced in 2018 and was completed at the end of December 2020. The project, which was subdivided into three phases, is based in the Seshego area in Polokwane. It was initiated to upgrade existing sewerage system, to meet the increased requirements of the Seshego local communities. Each phase of the project had a separate starting point with a common joining at a single point. Rocla, Regional Sales Manager, Andrew Kruger said, “The project was commissioned by the Polokwane Municipality to upgrade a now outdated sewerage system which no longer met the local community’s requirements in the Seshego area of Polokwane. We worked closely with site contractor Safcrete Construction so that the quality of the pipes would be to the standard required and delivery scheduling would be as seamless as possible”. “The pipes were 2,5 m Silica Rolling Joint Pipe, comprising a 3 mm sacrificial layer. Five sizes of pipe were required, namely 900 mm, 1 000 mm, 1 200 mm, 1 400 mm and 1 500 mm, which if placed end-to-end, the HDPE piping would be over 19 kms in length. The placement of each pipe required the insertion of a rubber ring and the welding of a ‘capping strip’ on the inside of each individual joint to ensure proper sealant,” said Kruger. Rocla’s HDPE lining offers water and sewer projects advantages such as a surface smoother than concrete, enabling smaller internal D on’t you just wish, when driving along a bumpy sand road, that there could be some form of tracking to make the journey easier? Or even when driving up your own driveway, that there is an attractive greened track that blends in with your already established landscaping? A simple yet highly engineered hardlawn paving from Technicrete, Amorflex HLP, is probably the best solution for a stable grounding. Easy to maintain by using traditional lawn maintenance techniques, Amorflex HLP paving blocks allow the natural greening of paved surfaces to form hard wearing grassed driveways, roadways, parking areas and embankments. They can also be used on embankments for light duty erosion protection as well as a light stormwater run-off. Once earthworks have been designed to suit the application

diameter piping to be utilised. The long-term pullout strength of the lining anchors is able to cope with a ground water pressure in excess of 10 m. Safcrete Construction commented that it had worked with Rocla and their engineers on many projects over the years and had always been impressed with the quality of the end product supplied. “The Rocla HDPE pipes were specified for this project because they offer the best solution to waste and stormwater plant and projects of this nature. Their attention to customer requirements, in this case, an exceptionally challenging delivery schedule, is also a feather in their cap”. Kruger added: “In order for our Polokwane factory to manufacture the various sizes of pipes and the required quantities, Rocla Polokwane underwent an overhaul in terms of the manufacturing sections needed to accommodate the upgraded equipment. We also made use of special Vertical Cast (VC) moulds which were required for use with the insertion of the sacrificial layer within the pipes. It was these changes that enabled us to meet the quantities of HDPE pipes required for the Polokwane Waste Water Treatment Plant projects as they enabled us to increase our production schedules and deliver to site timeously”. Concrete pipe with a cast in HDPE lining has all the advantages of a strong rigid pipe that keeps its shape as well as those of a plastic pipe that is inert to acid attack. It is the best pipe for large diameter gravity pipelines in almost any condition. Standard HDPE lining is light green and 3 mm thick. Different colours and thicknesses can be supplied. ▄ loading, the preparation for the laying of the Amorflex HLP blocks includes creating a surface of layer works to standard specifications 1200 MJ (max 10 mm in 3 m), and putting down a river sand bedding (with a recommended thickness of between 10 mm and 15 mm). The blocks are then hand-compacted into the bedding sand using a rubber mallet. The top openings in the Armorflex HLP blocks are filled with topsoil and grassed prior to trafficking. The blocks allow natural or planted vegetation to grow through their openings providing the natural aesthetically pleasing finish once installed. Keeping the soil intact is helped by the roots of the plant growth. The Amorflex HLP blocks are available in 340 mm x 294 mm with a 90 mm thickness, primarily in grey but other colours are available upon request. ▄

Greening hardwearing driveways with Armorflex HLP

CONSTRUCTION WORLD APRIL 2021 20