Construction World December 2017

Category B: Specialist Contractors or Suppliers

HAZELMERE DAM EXPANSION

and on various applications and product used for the project (some of these were Sika applications). The local workers were contracted for the duration of the project. Realising the total inadequacy of the dam’s water storage capacity, the Department of Water and Sanitation contracted consulting engineering company, Ingerop South Africa, for an effective design solution. A decision was made to raise the dam wall by seven metres, thereby increasing the dam’s capacity from 23,9 million cubic metres to 43,7 million cubic metres. As the first project of its kind in Southern Africa, involving the installation of 83 ground anchors into the spillway and the dam wall itself, the ground-breaking task called for the Australian based company, SRG to be subcontracted to drill, install and post tension the anchors. With grouting of the anchors being a critical part of the installation, Sika products were specified as it was agreed that they would provide the optimal properties necessary to meet the high standards required by SRG. To demonstrate the installation process, SRG carried out first site trials by placing four test anchors 40 m deep below the dam wall. After commencement of the project proper in August 2015, 355 mm diameter holes were drilled at depths varying between 55 m and 95 m. Along the spillway the holes were spaced 1,5 m apart, while on the dam

wall, the holes were spaced 7,5 m apart. The stringent requirements for the water cement grout mix (exclusive of any aggregates or sands) included: initial flow time of 12 seconds, reaching 15 seconds after 60 minutes; a maximum of 2% bleed after two hours; 60 MPA @ 28 days; OPC Cement Cem I; and a grout density of 1900. Sikadur-AP was specified for use on the nose cones of the anchors. The 250 mm diameter anchors, each requiring an average of 80 steel cables for post tensioning, were inserted into the holes. The first of two admixtures specified was Sika ViscoFlow-25 ZA, especially designed for concrete and grout mixes with extended workability requirements as well as improved flow characteristics. Compared to conventional dispersants, Sika ViscoFlow-25 ZA provides higher stability and workability time. Since Sika ViscoFlow-25 ZA contains no chlorides or any other ingredients which promote corrosion of steel, the product is ideally suited for use in reinforced and prestressed concrete structures. Sika Stabiliser-229 ZA, the second specified admixture, increases the cohesion and plasticity of grout, reducing bleed and segregation. Sikadur-42 ZA was used at the top of the base plates. It has a fluid consistency, is self-levelling, suitable for dry or damp concrete surfaces and provides high initial and ultimate mechanical strength. As this was the first time a project such as this has been carried out in Southern Africa, Sika was proud to be selected as one of the foremost suppliers of product. Sika was awarded the contract to supply specialist products to this prestigious project based on evidence provided of Sika’s prior experience in the particular type of grout needed for this project. Unique requirements of the product included: flowability, workability and bleed. Stringent tests were carried out onsite prior to the actual applications and Sika products passed each test with flying colours. The product used was a water cement grout, so there was no need for aggregate allowing for flow through all rebar and other areas.

The severe drought experienced in recent years resulted in Sika products being specified

for a mammoth ongoing project in KwaZulu-Natal.

However in November 2016, volume could have exceeded 70% if it were not for critical construction work on the slipway. Once this stage of the project was completed, in January 2017, the dam was allowed to fill to its maximum 100%, where it stands to date. Group Five, as main contractors, were mindful of ensuring the local community was considered during the construction phase of this project. Although it was necessary to relocate 15 families to higher ground, the project benefitted the local community by creating 53 new jobs. Basic training was given to the unskilled local workers as well as more specialised training for a variety of jobs The site is Hazelmere Dam, a concrete gravity dam originally constructed in 1976, situated 40 km north of Durban. By July 2016, the dam volume had dropped to 23% due to the severe drought in KZN.

Special Mention

PROJECT INFORMATION

• Company entering: Sika SA • Client: Department of Water & Sanitation • Contract value: R498-million (total) • Start date: August 2015 • Project end date: January 2017 • Main contractor: Group Five • Consulting engineer: Ingerop SA

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