concrete VOLUME 61 ISSUE 3
CERTIFIED PASSIVE PUBLIC HOUSING FOR AUCKLAND USING PRECAST CONCRETE
FILTER AWAY YOUR STORMWATER PROBLEMS WITH PERVIOUS CONCRETE
THE MAGAZINE OF CONCRETE NZ
UPFRONT QUALITY SHOULD ALWAYS BE IN THE MIX ALTHOUGH OUR SECTOR IS BUSY MANAGING THE CONTINUED UNCERTAINTY CREATED BY COVID-19, BUILDING QUALITY MUST NEVER BE COMPROMISED. Concrete NZ’s Plant Audit and Precast Certification Schemes provide purchasers and specifiers with peace-of-mind that their ready mixed concrete and precast concrete products meet quality requirements. CONCRETE NZ QUALITY SCHEMES Within a wider construction environment dominated by worries around operating during the ongoing pandemic, there have been recent reports of building material supply issues, and in turn, potential quality concerns. The media recently picked-up on a Master Builders’ survey which reported building consent delays, increased costs, customer complaints, and product substitutions due to a lack of building materials. While the concrete industry is not immune to challenges such as the truck driver shortage, and is monitoring aggregate supply, there are no capacity issues that should force building contractors to replace the quality assured concrete and concrete products supplied by members of the Concrete NZ Plant Audit or Precast Certification Schemes with inferior alternatives. READYMIX PLANT AUDIT SCHEME The credentials of the Concrete NZ Readymix Plant Audit Scheme, formerly the NZ Ready Mixed Concrete Association (NZRMCA) Plant Audit Scheme, are well known and respected. Providing a thorough audit of a ready mixed concrete plant’s own quality system in line with NZS 3104:2021 Specification for Concrete Production, the Plant Audit Scheme’s operations are carried out under a quality assurance programme certified to ISO 9001 and audited by Bureau Veritas (NZ) Ltd. PRECAST CERTIFICATION SCHEME Meanwhile, the Concrete NZ Precast Plant Certification Scheme is gaining traction amongst Precast Sector Group members and their clients. The manufacture of precast concrete products requires considerable experience and skill, as it often forms the primary structural system resisting both vertical and horizontal loads in a completed building. Poor precast manufacturing practices have the potential to compromise a structures durability and the life safety of its occupants.
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concrete MAGAZINE
Editor/Advertising: Adam Leach +64 4 915 0383 adam@concretenz.org.nz Subscriptions: Angelique Van Schaik +64 4 499 8820 admin@concretenz.org.nz concrete is published quarterly by Concrete NZ PO Box 448 Level 4, 70 The Terrace Wellington NEW ZEALAND Tel: +64 4 499 8820 Email: admin@concretenz.org.nz Website: www.concretenz.org.nz ISSN: 1174-8540 ISSN: 1174-9374 (online) Disclaimer: The views expressed in concrete are not necessarily those of the Concrete NZ. While the information contained in the magazine is printed in good faith, its contents are not intended to replace the services of professional consultants on particular projects. The Association accepts no legal responsibility of any kind for the correctness of the contents of this magazine, including advertisements. © Copyright 2021 Concrete NZ Advertorial Cover image: Bader Ventura Passive House Pilot, Mangere, Auckland. Kāinga Ora Homes and Communities
In addition, safety considerations are paramount during the manufacturing, handling and installation of precast products, with any short cuts potentially resulting in unsafe outcomes with significant consequences. The Precast Plant Certification Scheme provides specifiers, contractors and their clients with confidence that products purchased from a Precast Certified Plant are backed by an established operator with appropriate facilities, experienced staff and quality assurance programs. Regardless of application - architectural, structural, cladding, civil or other - purchasing from a Concrete NZ Precast Certified Plant ensures that the product has been manufactured at a facility with systems audited by an independent, third-party body. Certified Plants invest heavily in modern equipment, oversight procedures and staff training with the intention of delivering quality. While cheaper alternatives may be available, cost should never be the only consideration.
Procurement decisions must factor in quality as a prerequisite, and in terms of precast, the stamp to look for is the Concrete NZ “Precast Certified Plant” logo. For more details on the Precast Certification Scheme and a link to the precast plants currently registered visit the Concrete NZ website www.concretenz.org.nz Ngā mihi, Rob Gaimster Concrete NZ Chief Executive
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Call 07 575 5410 or visit: www.demden.co.nz
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CONCRETE NZ 2021 CONFERENCE POSTPONED UNTIL FEBRUARY 2022 CONCRETE NZ’S CONFERENCE 2021 HAS BEEN POSTPONED FROM ITS ORIGINAL DATES IN MID-OCTOBER 2021 AND WILL NOW TAKE PLACE 17-19 FEBRUARY 2022. THE VENUE REMAINS THE ENERGY EVENTS CENTRE IN ROTORUA. “Uncertainty around when all of New Zealand will return to COVID-19 Alert Level 1 prompted the decision to postpone,” say Concrete NZ chief executive Rob Gaimster. “The Concrete NZ Board and Conference Organising Committee felt that rescheduling to February 2022 offered greater assurance that all those wishing to attend and/or support the event would have the opportunity to do so. “The Conference Secretary is currently reaching out to presenters as well as patrons, sponsors and trade exhibitors to make them aware of the new dates. “Concrete NZ hopes that the postponement is not a significant inconvenience, and remains confident that the rescheduled event will be an excellent opportunity for professional networking while remaining up-todate with developments across concrete design, construction, materials and technology,” concludes Rob.
Further updates will follow, but if you have any questions do not hesitate to contact the Conference Secretary - concrete@bluepacificevents.com or +64 9 536 5410.
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POSTPONED NEW DATE 17-19 FEBRUARY 2022
RESCHEDULED CONCRETE NZ CONFERENCE 2021 SET TO INFORM AND ENTERTAIN REGISTRATIONS REMAIN OPEN FOR CONCRETE NZ’S 2021 CONFERENCE WHICH HAS BEEN RESCHEDULED TO 17-19 FEBRUARY 2022 AT THE ENERGY EVENT CENTRE IN ROTORUA. The Conference is a definite highlight of each year for the construction industry, offering a combination of quality technical content, outstanding social functions, broad industry representation, and value for money that is unsurpassed by other conferences.
As always, the well-crafted conference social programme will provide plenty of chances to renew or create connections.
The Rotorua Energy Events Centre offers comfortable auditoria, along with great spaces that will provide ample opportunity to engage with trade exhibitors who form an integral part of the conference. Amongst these exhibitors will be the patrons and sponsors, who increase the value proposition of the conference and deserve particular acknowledgement. An exceptional response to the call for papers has allowed the organising committee to assemble a strong technical programme that will cater to the varying interests of attendees. The programme is headlined by Santiago Pujol, Professor of Civil Engineering at the University of Canterbury, whose experience includes earthquake engineering and the evaluation and strengthening of existing structures.
Professor Santiago Pujol, University of Canterbury
CONCRETE NZ CONFERENCE E concrete@bluepacificevents.com P 09 536 5410 W www.theconcreteconference.co.nz
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POSTPONED NEW DATE 17-19 FEBRUARY 2022
NEW CONCRETE AWARDS FRAMEWORK LAUNCHED TO ENHANCE OPPORTUNITIES FOR RECOGNISING ACHIEVEMENTS IN, AND RAISE THE PROFILE OF, THE CONCRETE INDUSTRY, CONCRETE NZ IS HAS ANNOUNCED IT WILL MOVE TO TWO ANNUAL AWARDS EVENTS. One of the events will remain part of the established annual Concrete NZ conference formal dinner. This event will be primarily inward facing, and appeal to Concrete NZ members across all the Sector Groups and the Learned Society. The second, new awards event will be outwards facing, appealing to clients and stakeholders not directly involved in the concrete industry, as well as Concrete NZ members. The inaugural event is scheduled for 2022 in Auckland. The revised awards framework (outlined below) acknowledges and respects the historical awards. 2021 CONCRETE NZ CONFERENCE AWARDS 1. Honorary Life Member 2. Outstanding Contribution 3. Producer - Extra Distance* 4. Producer - Technical Excellence* 5. Plant Audit Scheme 6. Health & Safety Achievement* 7. Carbon Reduction* 8. Inclusion & Diversity* 9. Concrete Industry Apprentice of the Year* 10. Learned Society Student Concrete Prizes 11. Best Conference Trade Exhibit 12. Sandy Cormack Best Paper Award 6 concrete
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2022 CONCRETE INDUSTRY AWARDS 1. Premier Concrete Award 2. Excellence in Architectural Concrete (Monte Craven Award) 3. Excellence in Infrastructure Concrete 4. Excellence in Commercial Concrete 5. Excellence in Residential Concrete 6. Excellence in Community Concrete 7. Excellence in Heritage Concrete 8. Excellence in Concrete Innovation 9. Best Graduate Engineer 10. Best Graduate Architect 11. Enduring Concrete Award The introduction of the new awards framework will see the Learned Society’s Concrete Awards, Concrete3 Sustainability Awards and Readymix Awards discontinued. As outlined on page 4, Concrete NZ’s Conference 2021 has been rescheduled to 17-19 February 2022, with the awards to be presented during the formal dinner on Friday 18 February. Entries for the 2021 Concrete NZ Conference Awards marked with an asterisk now close on Friday 26 November 2021. Visit the Concrete NZ website for entry detail – www.concretenz.org.nz
POSTPONED NEW DATE 17-19 FEBRUARY 2022
ENTRIES STILL OPEN FOR THE 2021 CONCRETE INDUSTRY APPRENTICE OF THE YEAR CONCRETE APPRENTICES FROM AROUND NEW ZEALAND ARE ENCOURAGED TO SHOWCASE THEIR TALENT AND COMMITMENT BY ENTERING THE 2021 CONCRETE INDUSTRY APPRENTICE OF THE YEAR AWARD. Entries remain open, with apprentices offered an opportunity to win a share of around $10,000 in prizes, as well as the sought-after title of 2021 Concrete Industry Apprentice of the Year. Concrete NZ chief executive Rob Gaimster believes the reasons for establishing the award in 2017 remain - primarily the need for skilled concrete workers, as well as making sure those considering a career in construction are aware of the opportunities that the concrete industry offers. “Within the construction sector, our industry has generally found it difficult to attract and retain qualified workers. Over recent years this has become accentuated by a buoyant market and therefore plenty of options for prospective workers. “The award is also an ideal way to recognise distinction and give impetus to an apprentice’s career – it’s a chance to demonstrate aptitude and set targets, as well as network with other concrete professionals,” says Rob. The Award is open to all people who are currently enrolled in, or have qualified in one of the following BCITO concrete-based apprenticeships since 1 October 2019.
NATIONAL CERTIFICATE • Precast Concrete (Level 3) • Concrete Production (Level 3) • Product Manufacture: Pipe (Level 3) • Product Manufacture: Masonry Product (Level 3) • Construction: Sawing & Drilling (Level 3) • Construction: Placing & Finishing (Level 3) • Concrete Construction (Level 4) NEW ZEALAND CERTIFICATES • Concrete Construction Skills (Level 3) • Concrete Construction: Commercial and Civil (Level 4) • Concrete Specialist (Level 4) • Concrete Production (Level 4) “The Concrete Industry Apprentice of the Year award is centred around the principle that perseverance and hard-work are rewarded by success. Those in trade training should be recognised as aspiring professionals, and choosing a career in the concrete industry offers a range of exciting opportunities for those interested in construction,” concludes Rob. As outlined on page 4, Concrete NZ’s Conference 2021 has been rescheduled to 17-19 February 2022, with the Concrete Industry Apprentice of the Year award new set to be presented during the formal dinner on Friday 18 February. Entries now close Friday 26 November 2021. Entry forms are available from the Concrete NZ website www.concretenz.org.nz
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CONFERENCE 2021
NEW DATES 17-19 FEBRUARY 2022 ENERGY EVENTS CENTRE ROTORUA 8 concrete
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NEW GUIDE TO MINIMISING THE RISK OF DELAMINATION CONCRETE NZ HAS PRODUCED A NEW TECHNICAL DOCUMENT - GUIDE TO MINIMISING THE RISK OF DELAMINATION IN CONCRETE - IN RESPONSE TO REQUESTS FROM MEMBERS. Delamination is defined as a zone of weakness or separation along a plane parallel to the concrete surface caused by either material, processing and/ or environmental factors. These surface defects vary in size, depth and timing depending on the cause and other related factors. The prevalence of delamination problems is mostly associated with floor slabs, which has increased in the last twenty years as larger industrial floors have given rise to modern finishing systems. Delamination of finished floor slabs represents a failure of the wearing surface such that the highly finished and hard layer is replaced by a rough and irregular indentation. These surface defects are a significant serviceability issue since they disrupt the otherwise hard and smooth surface of finished concrete.
Repairs to restore the aesthetics and resistance of the concrete surface have been undertaken successfully but these need to be thoroughly investigated beforehand. The Guide was written to provide the necessary awareness of risks and mitigations strategies for the delamination of concrete, with specific focus on finished floor slabs. The Guide to Minimising the Risk of Delamination in Concrete can be downloaded from the Concrete NZ website – www.concretenz.org.nz
CONCRETE NZ ACKNOWLEDGES THE SUPPORT OFFERED BY
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CONCRETE PRODUCTION STANDARD REVISED STANDARDS NEW ZEALAND WISH TO MAKE INDUSTRY AWARE THAT NZS 3104:2021 SPECIFICATION FOR CONCRETE PRODUCTION IS NOW AVAILABLE. Commissioned and developed under a new ‘partnership agreement’ by Concrete NZ, the Standard prescribes the minimum requirements for the production of fresh concrete, and supersedes the 2003 revision of the original 1983 standard. The principal changes incorporated into the revision are: • New provisions have been introduced for the evaluation of compressive strength results for concrete plants that can demonstrate excellent control of their concrete production. • Technical control of concrete production has been tightened by introducing mandatory requirements for 7-day strength testing and daily moisture content measurement of fine aggregate. • Yield testing has been increased for plants producing more than 9000 m3 per year. • Content has been updated to acknowledge the influence of new materials, technologies and practices such as supplementary cementitious materials, recycled materials and other Standards and technical guidelines.
The revision has been designed to meet an identified industry need and will allow users to follow up-to-date and recognised good practice methods, and provides a modern, safer compliance document to enable nationally consistent concrete production. The Concrete NZ Plant Audit Scheme Handbook has been updated to reflect the changes, and will be distributed to plant engineers and plant managers shortly. Copies of NZS 3104:2021 can be purchased from the Standards New Zealand website www.standards.govt.nz
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www.roadex.co.nz
SUMMARY OF SIGNIFICANT CHANGES IN NZS 3104:2021 No.
NZS 3104:2021 Clause
Clause Title and General Description Impact of the changes for plant or PE’s
NZS 3104:2003 Clause
1
Definitions
Plant supervisor and technician definitions Training requirements given and PE approval
Not covered before
2
2.5.4.2
Confirmation tests for sand moisture Requirement for daily measurement of moisture
Not covered before
3
2.5.4.2 & 2.5.4.1
Compliance testing for fine & coarse aggregate Frequency now from NZS 3121 – 2, 3 or 4 per month
2.4.3.2 & 2.4.4.1 100 m3 & 50 m3
4
2.7.5 & Table 2.2
Measurement tolerances for materials Allows greater tolerance for small batch sizes
Table 2.2 had no special provisions for size
5
2.14.1.2
Data for demonstrating compliance (normal concrete) Major series (30) requirements and recommendations
C2.13.1.2 & 2.13.1.2 Min. of one series of 30
6
2.14.1.3 & Tables 2.5 A-C
Criteria for plants with a minimum testing regime Allows 56-day testing for normal concrete
Table 2.5A & 2.5B No allowance for SCMs
7
2.14.1.5 Table 2.5C
Compliance requirements for series with low variance Allows lower TMS for individual mix series
Not covered before
8
2.14.1.7
Compliance requirements for initial audits a) 28-day strength COV analysed with Table 2.5A
Previously used Figure 2.1
9
2.15.3.3
Compliance criteria for spread 10% tolerance recommended for spread testing
Not covered before
10
2.15.4.3
Frequency of yield testing of concrete Will require more testing for mid to large plants
2.15.2.3 Once per week
11
2.15.6.2 Table 2.8
Performance requirements for uniformity Mean strength based on 3 specimens only
Table 2.7 - Used 2 or 5 with range limits
12
C2.15.7.1
Sampling of small loads of concrete Reliability suspect for less than one third of full load
Not covered before
13
2.15.7.2
Number of test samples Requirement for 7-day testing (mandatory now)
Not covered before
14
C.2.15.8.1
Test cylinders cast on site (commentary) Limitations and reliability of site testing of concrete
Not covered before
15
Appendix A
Checklist for auditing engineers (Informative) Provides a summary of audit records and checks
Not covered before
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SCM RESEARCH 2. CLASSIFICATION OF SCM REACTIVITY IN CONCRETE James Mackechnie, Education, Training & Research Manager, Concrete NZ BEFORE NEW SUPPLEMENTARY CEMENTITIOUS MATERIALS (SCMS) CAN BE USED IN CONCRETE THESE MATERIALS NEED TO BE ASSESSED. Classification of SCMs in New Zealand is based on the relative strength approach outlined in AS 3582.6 where prescribed mortar mixes made with SCM combinations are compared with control mortar mixes made using Portland cement. This article compares the results of a range of classification systems for SCMs with concrete strength results using the same materials (SCM replacement was constant at 30 percent). The following cementitious binder materials were used to investigate these classification systems: • S1 was GP cement either from Golden Bay or Holcim cement • S2 was fly ash from Huntly, NZ (ASTM Class C) • S3 was fly ash from Adani, India (ASTM Class F) • S4 was a natural pozzolana from NZ (Golden Bay Cement) • S5 was ground perlite powder from Tokoroa, NZ • S6 was calcined clay from kaolin in Geraldine, NZ (55 percent purity) Concrete mixes used in these trials had the following constituents and properties: • Total binder content of 350 kg/m3 and water/ binder ratio (w/b) of 0.45 • Fine and coarse aggregate used was greywacke from Christchurch • Chemical admixtures were high-range water reducer with the dose varied to main constant water demand in concrete mixes RELATIVE STRENGTH (W/B RATIO VARIES) NZS 3123 requires that relative water demand and strength methodology be used when assessing SCMs. Relative strength index is measured using AS 3583.6, which is similar with ASTM C311 and specifies 20 percent replacement level. The
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correlation between mortar strengths from this test and concrete strengths is relatively poor (see Figure 1) due to: • Differing water demands of industrial and natural pozzolans that affect water demand and therefore strength (since water/binder ratio varies). • Single replacement level of 20 percent, which is lower than those often used in concrete mixes (typically 25-30 percent replacement). • Variable plastic viscosity of mortar due to the absence of admixtures that can influence the quality of compaction and therefore entrapped air contents. The relative strength test is a basic screening test that is suitable for identifying poorly reactive pozzolanic materials or those materials that create excessive water demands. Research found the correlation between mortar and concrete strengths was poor when comparing a range of SCMs with no clear relationship, shown by a very low R2-value. This was found even when also using 56-day comparisons that are also included in the analysis shown in Figure 1. MODIFIED STRENGTH ACTIVITY INDEX TESTING (MORTAR W/B = 0.50) The modified strength activity index was done in accordance with EN 196-1 but using a water reducing admixture to achieve similar mortar consistence at a constant w/b ratio of 0.50. Mortar strengths with 30 percent replacement of SCMs at 7 and 28 days were then compared with compressive strengths for concrete mixes with similar replacement and water/binder ratios of 0.45. Figure 2 shows the relationship between mortar and concrete strengths at 7, 28 and 90 days. A better correlation between mortar and concrete strength was achieved by adjusting the dose of
80
GBC & Holcim GP cement blends
Compressive strength (MPa)
75 70 65
R2 = 0.0027
60 55 50 45 40 35 30
30
35
40
45
50
55
60
Glass Content (%) S1
S2
S3
S4
S5
S6
Linear
Figure 1: Concrete strength versus mortar strength at 28 and 56 days 90
80
Compressive strength (MPa)
R2 = 0.8702
GBC & Holcim GP cement blends
70
60
50
40
30
20
15
20
25
35
30
40
45
50
55
60
Modified strength activity index (MPa) S1
S2
S3
S4
S5
S6
Linear
Figure 2: Compressive strength versus modified strength activity index
water reducing admixtures to maintain a constant water content. This adjustment of the mortar mixes is easy to do and is typically the approached used with standard concrete mix design practice. Natural pozzolans have higher water demands than materials such as fly ash, and adjustment for this difference provides a fairer overall assessment of potential reactivity of pozzolans. ISOTHERMAL CALORIMETRY (PASTE W/B = 0.50) Testing using isothermal calorimetry was done in accordance with ASTM C1679 using small paste samples at 30 percent replacement levels. The isothermal calorimeter maintains constant temperature at 20oC and measures the net energy and heat flow associated with cementing reactions. Figure 3 shows the relationship between isothermal energy and compressive strength of concrete after three and seven days.
Using isothermal calorimetry on neat paste samples provides a reliable method of assessing the reactivity of pozzolans as shown by the excellent correlation between paste energy output and concrete strengths (e.g. R2-value of 0.89). The methodology does require sophisticated testing equipment not available outside of specialist laboratories. BOUND WATER FROM THERMOGRAVIMETRIC ANALYSIS (PASTE W/B = 0.50) Hydration studies were undertaken on paste samples that were cured in water for periods of 3, 7, 28 and 90 days before being subject to thermogravimetric analysis (TGA). The bound water of hydration was determined from the mass difference found between 110 and 400oC. Figure 4 shows the relationship between bound water and compressive strength at ages of 3, 7, 28 days (90 days still to be completed). A good correlation was found between bound
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water content of SCM pastes and concrete strengths measured after 3, 7 and 28 days. TGA does not require expensive equipment for testing and could be used to measure the potential performance of SCMs. This confirms that bound water is a useful measure of the quantity of hardened cement paste found in a sample.
that create excessive water demand or have extremely low reactivity). Alternative classification methods were found to have the following reliability in predicting compressive strength of SCM concretes. Modified strength activity test has the advantage that water demand variations are eliminated but differences in plastic viscosity still affect the compaction efficiency of mortars, nevertheless the test had a good correlation with concrete strength.
CONCLUSIONS Several SCMs were assessed using standard and alternative classification systems that are intended for use in assessing potential pozzolanic reactivity. These materials exhibited a range of potential pozzolanic reactivity that ranged from high to low.
Testing of paste samples using isothermal calorimetry can accurately measure pozzolanicity of SCMs but there are limited devices in New Zealand making this type of testing suitable only for research studies.
The current methodology for assessing SCM quality (relative strength) was found to have limited ability and appears to be suitable only as a rough screening test (i.e. test can only identify powders
Hydration studies using TGA are relatively cheap and showed a very good correlation with concrete strength performance.
60
Compressive strength (MPa)
R2 = 0.8892
GBC & Holcim GP cement blends
55 50 45 40 35 30 25 20 15 10 150
170
190
230
210
250
270
290
Energy (J/g of binder) S1
S2
S3
S4
S5
S6
Linear
Figure 3: Compressive strength at 3 and 7 days versus isothermal energy 80
GBC GP cement blends
R2 = 0.9364
Compressive strength (MPa)
70
60
50
40
30
20
10
10
12
14
18
16
20
22
Bound water (%) S1
S2
S3
S4
S5
S6
Linear
Figure 4: Compressive strength at 3, 7 and 28 days versus bound water percentage of paste
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Your building could be put to the ultimate test. So we do the same to our steel. At Pacific Steel, we put all our products through a rigorous testing regime. Our dedicated laboratory has full IANZ certification and we’re the only local manufacturer of reinforcing steel to have third party ACRS certification. So when we say our SEISMIC® reinforcing steel is tested to meet the AS/NZS 4671 standard, you can be sure it’s been put to the ultimate test.
A steel bar about to be tested in one of five testing machines at our laboratory in Otahuhu.
PAC0015CCT
INFILTRATING CONVENTIONAL PAVING SYSTEMS WITH PERVIOUS CONCRETE AN IMPRESSIVE RANGE OF ENVIRONMENTAL AND LIVEABILITY BENEFITS ARE ACHIEVABLE THROUGH THE USE OF PERVIOUS CONCRETE, WHICH CAN BE INSTALLED INSTEAD OF CONVENTIONAL PAVING IN MANY DIFFERENT APPLICATIONS. AquaPave Pervious Concrete managing director Adrianna Hess, who is a certified pervious concrete technician, says the system is both “friendly to the environment and great for urbanisation.” “Quoting the United States’ National Ready Mixed Concrete Association (NRMCA) – “It’s not just pavement – pervious concrete is part of a worldwide movement toward green infrastructure,” says Adrianna. “For example, our pervious concrete system can vastly reduce the flow rate and amount of water entering the stormwater system. 16 concrete
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“I take a double-ring infiltrometer on site to calculate what the infiltration rate is and then use software that designs how thick the basecourse should be to infiltrate all of that water. I can design the system so that you have basically zero runoff.” Adrianna says the system also performs a key bioremediation function. “Pervious concrete traps the ‘first flush’ of contaminants – which is the most polluted part of stormwater runoff – occurring at the beginning of a rainfall event.
“Particles and dirt will percolate through the system and be held in the basecourse, but heavy metals such as zinc and copper actually diffuse into the cement paste itself and become part of the installation. Polyaromatic hydrocarbons will get metabolised by bacteria and biomass that live in the slab too.” The system functions well even with poor infiltration rates as low as one millimetre to two millimetres per hour. In addition, pervious concrete reduces the need to apply salt to footpaths as the meltwater infiltrates rather than refreezes, and the system therefore recharges groundwater supplies. “In contrast, vast expanses of conventional paving in urban areas prevent infiltration of rainwater, which reduces groundwater tables and may cause water restrictions.” Providing water and air to urban tree root systems and preventing the cracking and lifting of footpaths, the system also helps reduce temperatures in urban areas and prevents heated water running back into waterways. “When you walk on pavement in the sun, we all notice how hot it gets. This is part of an urban environment’s ‘heat island effect’. A consequence of this is that rainwater, as it washes over that pavement, warms up considerably before running into the stormwater drain and then onto waterways, which is bad for aquatic life. “Neither of these factors occur with pervious concrete, as the open pore structure absorbs and
releases much less solar heat, and of course, you simply do not have the runoff.” DEVELOPER/LIVEABILITY BENEFITS In a key benefit for developers, the use of pervious concrete frees up land for their build. “Developers do not have to allocate 30 percent of otherwise usable area to a stormwater detention pond, as the parking area itself becomes the detention pond. This is a mindblowing aspect, which I spend a lot of time explaining to civil engineers. “For example, when it rains on say a 1,000 m2 standard parking lot, you can’t leave the water there as it is a hazard. It has to be moved to a metre-deep detention pond – but if you have poor infiltration and then get another storm event, it will overflow. “However, as we have that large expanse of drainage area incorporated within the pervious concrete system itself, the rainwater is trapped in the basecourse and slowly percolates back into the earth.” Furthermore, pervious concrete improves liveability by delivering a quieter pavement. “Engine and tyre noise is absorbed at the interface with the pavement – it deadens the sound because of the voids. You’ll definitely notice that cars driving at night won’t sound nearly as loud as on a regular street.”
Technical features of pervious concrete include: • No fines (sand) aggregate. • High porosity via an interconnected network of voids (typically 20 percent). • 20,000 mm per hour drainage. • 22 MPa strength achieved at 28 days. • Used primarily in pavement applications. SYSTEM CONSIDERATIONS One major consideration with designing a pervious concrete system is that it cannot receive runoff from asphalt, says Adrianna. “The sticky tar fines that shed from asphalt will get into the pervious voids and plug them – which can compromise ‘porosity’ and be detrimental to performance. As such, design expertise is required to prevent this from occurring. Another important issue is to ensure the correct water content is achieved in the mixture to enable appropriate installation. “With regular concrete, you place it, but can’t start finishing it until it starts to cure. With pervious concrete however, you have to get it down, and then finish and cover it before it starts to cure. If it is done incorrectly, the system could dry out too quickly and could fail. “We have developed and patented an admixture that allows us to get up to 42 percent water content, which makes it easier for installers to put the concrete down and keeps the mixture wetter for longer, without the paste running off. It also allows the mix to cure fully and, if installed correctly, prevents ravelling. 18 concrete
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“It is my goal to train as many people as possible to install pervious concrete correctly.” AQUAPAVE SERVICES Adrianna says AquaPave had considered assembling its own pervious concrete installation team, but subsequently decided to focus on offering training and design functions instead. “We have found that there are enough placers in New Zealand that want to learn how to work with pervious concrete correctly. So, we are available to assist, and in so doing help ‘spread the word’ a lot quicker than placing it ourselves. “We also work with stormwater engineers and landscape architects to design a pervious concrete system that will infiltrate stormwater based on actual infiltration rates and that are designed for specific storm events, such as a one-in-100-year storm in Dunedin.” AquaPave has partnered with Permacolour on the manufacture of its integrated oxide colour options and is also currently working with Allied Concrete to manufacture its pervious concrete mix. “We can, however, design a pervious concrete mix in any region for any batch plant.” Adrianna adds that she is hoping to develop a local pervious concrete technician certification. “We are looking to create something whereby, if a concrete placer wants to get certified or send their foreman, there is going to be a class and exam, and on-site visit to assess what they are doing and standardise their technique.”
INTRODUCING AQUAPAVE AND ADRIANNA HESS Established by a team of researchers and roadworks engineers in the San Francisco Valley 15 years ago, AquaPave today consists of managing director Adrianna Hess and one other director operating out of Christchurch. Understood to be the only National Ready Mixed Concrete Association (NRMCA) certified pervious concrete technician in either New Zealand or Australia, Adrianna is passionate about training local concrete placers in the techniques. “I would like New Zealand’s concrete installers to know that I want to support them in increasing their capability and competency in handling pervious concrete,” says Adrianna. “If they want to use pervious concrete – given it is so good for the environment – then I can help.” Adrianna says another key service provided by AquaPave in New Zealand is designing commercial installations – such as car parks for distribution centres. “We also work with developers to maximise built area in new subdivisions and provide homeowners with alternative drainage solutions – for example, avoiding digging drainpipes and connecting to municipal stormwater mains. “We have worked with design professionals at Powell Fenwick, Fluent Solutions, Kāinga Ora, Miles Construction and Davis Ogilvie to name a few.” Adrianna holds a Bachelor’s Degree in Business Administration, Management and Operations from the Western Michigan University’s Haworth College of Business and a Master of Urban Resilience and Renewal, Geography from the University of Canterbury.
Adrianna Hess
For more information visit the AquaPave Pervious Concrete website - www.aquapave.co.nz
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KĀINGA ORA DEVELOPMENT PROMISES TINY CARBON FOOTPRINT KĀINGA ORA HAS TAKEN ITS FIRST STEP TOWARDS A CERTIFIED PASSIVE PUBLIC HOUSING DEVELOPMENT WHICH WILL DELIVER A REDUCED OPERATIONAL CARBON FOOTPRINT, MEANING THE HOMES CAN BE HEATED FOR AS LITTLE AS $1 PER DAY. The three-storey, 18-home Bader Ventura development in Mangere has received design endorsement to build to Passive House standard. Design endorsement is the first major milestone to producing a certified Passive House. Kāinga Ora General Manager Construction and Innovation Patrick Dougherty, says the development, when complete, will be a win for both the environment and the homes’ new occupants. “For Kāinga Ora as a major property developer, Bader Ventura is a big step towards meeting MBIE’s Building for Climate Change 2035 proposed final thermal performance cap 12 years ahead of industry expectation. 20 concrete
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“For Kāinga Ora customers, it will mean a reduction of around 85 percent in heating costs and a year-round healthy home. “This means we expect the average annual energy bill for heating in these homes to be around $360, or $1 a day, compared with about $2,000 for a standard Kāinga Ora home built to 6 Homestar standard, and even more for an older home.” As the country’s largest client of new residential construction services, Patrick says Kāinga Ora is pleased to be leading lower carbon construction by example. In doing so, the organisation is also on track to deliver Australasia’s first Passive House public housing funded by central government.
Transforming the operational efficiency of buildings is a key part of the long-term Building for Climate Change programme run by the Ministry of Business, Innovation and Employment (MBIE). Bader Ventura is the first Passive House pilot development for Kāinga Ora and the first project in its Carbon Neutral Housing programme. The organisation will undertake continuous reporting of performance and learnings throughout construction and post occupancy, sharing its findings with the wider industry. PROJECT DETAILS • 6 x 2-bedroom and 12 x 3-bedroom homes in a 3-level walk-up typology. • Homes will regulate their own temperature through smart design, the use of high performing construction materials and a ventilation system with heat recovery.
• Due for completion mid-2023. • Targeting an 8 Homestar Version 4.1 rating and will deliver an accepted alternative to the Healthy Homes Standard for heating. PROJECT PARTNERS It has taken a true team effort to achieve this milestone, and our key project partners have gone above and beyond to help us get to this point: • Precision Construction – Build Partner • Peddlethorp – Architects • Oculus Architectural Engineering Ltd - Passive House Lead and Façade Engineers • Kirk Roberts - Structural Engineers • 2PiR Consulting – Building Services Engineers • Sustainable Engineering – Passive House Certifiers • Concretec – Precast Concrete Manufacturer
MBIE is developing proposals to set required levels of energy efficiency and indoor environmental qualities for new buildings to reduce carbon emissions from New Zealand homes and buildings whilst also making them healthier, warmer, drier and more adapted to a changing climate, which would make developments like the Bader Ventura more common. The Passive House Standard originated in Germany. It is recognised internationally as a best practice benchmark for low energy use, indoor environmental quality and health performance, especially when applied to social housing. New Zealand currently has approximately 61 certified Passive Houses and more on the way. The Passive House Institute NZ, Te Tōpūtanga o te Whare Korou ki Aotearoa has a list of certified Passive Houses on its website - www.passivehouse.nz
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INNOVATIVE PRECAST CONCRETE SEAWALL PROVEN IN PRACTICE FEATURED IN THE PREVIOUS ISSUE OF CONCRETE MAGAZINE, WESTLOCK CONCRETE SOLUTIONS’ (WCS) INTERLOCKING PRECAST CONCRETE SEAWALL HAS BEEN MAKING A SPLASH BY DEFENDING THE SMALL WEST COAST COMMUNITY OF HECTOR FROM RECENT STORM SURGES. Developed in partnership with Busck Prestressed Concrete, WCS’s seawall consists of three different block types (base, standard and top), is five blocks high and 40 blocks long, totalling around 200, 2-tonne concrete blocks.
During July the seawall ‘weathered the storm’, deflecting all that the raging Tasman Sea could throw at it, proving to be an effective solution in protecting New Zealand’s vulnerable coastline against rising sea levels.
WIN A SET OF WESTLOCK CONCRETE SOLUTION (WCS) MINI-BLOCKS Go in the draw to win your own miniature WCS seawall by answering the simple question below: Tide gauge measurements show that global sea level rise began at the start of the 20th century. Between 1900 and 2017, the globally averaged sea level rose by: A. 10-15 cm
B. 16–21 cm
C. 22-27 cm
Hint: Everyone’s favourite online encyclopaedia will help. Email your answer to library@concretenz.org.nz. Entries close Friday 29 October 2021.
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AWARD WINNING CONCRETE HOME DESIGNED AND BUILT TO ENDURE
Image: Simon Devitt
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BLACK QUAIL HOUSE IN BANNOCKBURN, CENTRAL OTAGO, BY BARCELONA-BASED NEW ZEALANDER BERGENDY COOKE OF BC+A, HAS BEEN NAMED HOME OF THE YEAR 2021. Beneath a Pinot Noir vineyard on the Kawarau River, the house is located in an environment of climatic extremes on land scarred by the region’s gold mining history. Upturned schist, lichen and wild thyme are the hallmarks of the undoubtedly unique site. “It’s not a house that wants to show off. It’s one that wants to be quiet, subtle and calm. It was completely informed by its location, from the architectural language to the selection of materials,” explains Bergendy Cooke. Constructed in concrete, Black Quail House is an exploration of protection and permanence. “I have always loved concrete but it’s not a common residential material in New Zealand; we have an affinity with timber – it’s firmly entrenched in our vernacular. This project called for something different, materials that were durable, had integrity and aged well. It necessitated a substantial material not only to create a protective solid mass but also one that reflected the site’s materiality. The concrete precast panels are, in a way, poured stone; an updated version of the stone used for basic shelter by the miners.” Four architecturally designed houses from around the country were named as category winners.
“Each of these homes is a considered and thoughtful response to site and brief, and a marker of the immense skill that exists in the New Zealand architectural industry. It is with pride that we celebrate and document these beautifully crafted buildings as a record of our time and place,” says HOME’s editor in chief Clare Chapman. HOME’s commercial director Nat Davis says: “This year marks the 26th anniversary of the prestigious Home of the Year awards programme. With the support of our partners BMW, Dulux, Fisher & Paykel, and Studio Italia, we are proud to celebrate and showcase some of New Zealand’s best residential architecture.” This year’s programme saw a record number of entries received from around the country, with the winners selected following a national tour that took the judging panel from Coromandel to Bluff. “Versatility and resourcefulness were dominant in this competition,” says awards’ convenor Federico Monsalve. “Materials, design intent, responses to context and to client briefs were all approached with a mastery of many palettes, a level of maturity and intelligence that bodes well for the future of our built environment.”
Video: Paul Brandon Films
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New Foodstuff’s distribution centre, Auckland. BBR UT CONA CMF flat PT.
NEW ZEALAND’S LARGEST SINGLE-PROJECT FLOOR SLAB AS BBR CONTECH APPROACH THEIR THREE MILLIONTH SQUARE METRE OF POST-TENSIONED FLOOR SLABS, MIKE LAWSON, MANAGER - TECHNICAL, QUALITY AND HEALTH & SAFETY, SHARES DETAILS OF A RECORD-BREAKING FLOOR SLAB RECENTLY COMPLETED BY THE TEAM AND SOME FURTHER BACKGROUND TO THE STORY - WHICH IS ALL ABOUT FOOD! The BBR Contech team has recently completed the largest floor slab ever produced in New Zealand in a single project. In terms of the scale of this amazing post-tensioning project, the adjacent statistics say it all. The floor was installed as the foundation of a brand-new distribution centre for Foodstuffs a 100 percent New Zealand-owned company established in 1922 that’s now the country’s leading grocery distributor and one of its largest organizations. STATE-OF-THE-ART DISTRIBUTION Foodstuffs operates through regional co operatives that together run more than 700 owner-operated businesses. These include fullservice supermarkets, retail food warehouses, neighbourhood grocery stores, small convenience stores, large- and small-format liquor stores, fuel 26 concrete
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sites and specialist supermarkets that source goods from local growers and farmers. Each regional cooperative supports and services its local stores through integrated warehouse and transport centres. These centres use a state-ofthe-art ‘voice picking’ warehouse management system, which has enabled them to increase production, reduce repairs and maintenance, and improve their health and safety records. In February 2018, the company announced its intention to consolidate three of its North Island distribution centres into a single, purpose-built, temperature-controlled distribution centre. Its chosen location was Auckland Airport’s ‘The Landing’ - a world-class business park that comprises more than 100 hectares of development land catering for the logistics, technology and light industrial sectors.
PROJECT STATISTICS 74,000 m2 FLOOR SLAB 14,000 STRESSING OPERATIONS 13,000 m3 CONCRETE 340,000 m STEEL PRESTRESSTING STAND 84,000 m DUCTING
View during construction of the floor slap for Foodstuff’s new distribution centre.
EARLY-STAGE INVOLVEMENT BBR Contech became involved with the Foodstuffs project in the early stages of its development, mainly in relation to the suitability and layout of the floor slab. However, the warehouse’s design and layout later changed, making the original joint layout less than ideal. Working with Conslab - the concrete flooring contractor and an industry partner - BBR Contech redesigned the slab to minimize the number of armoured floor movement joints and maximize the size of the floor pours. The originally specified floor joints were replaced with a patented joint system developed by Conslab in New Zealand that offers superior performance and durability. For Foodstuffs. this meant a robust and highly usable floor, low whole-of-life maintenance costs and enhanced operational efficiency. The 74,000 m2 warehouse is approximately 360 m by 230 m at its most extreme dimensions - and overall the space equates to around the size of seven rugby football pitches. It uses two slab
designs as one area has a taller racking system than elsewhere and the floor is required to handle the heavier loads. FLOOR SLAB SPECIFICS The floor comprises nine separate post-tensioned slabs of 6,000 m2 to 10,000 m2 in area, with heavyduty movement joints around the perimeter. Each of the nine slabs comprises three or four smaller, continuous slabs with coupled tendons or stopend joints. Each slab was poured over two consecutive days. In all there were 31 pours ranging from 300 m3 to 530 m3, with most slabs being 180 mm thick. Given the size of the job, and working closely with Auckland Airport and main contractor Macrennie Commercial Construction, the BBR Contech team leapt into action to source materials and manpower. The latter was a particular challenge, as the project required a full-time crew of four to six members with the skills and experience to deliver a perfect result. The whole thing went like clockwork.
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The team was delighted to be working on this massive project, and we were very proud to emerge with an immaculate safety and quality record. LATEST BBR POST-TENSIONING The project signalled a new ‘first’ for BBR Contech with the use of the BBR VT CONA CMF S2 flat post-tensioning system. The system leads the market in offering all the benefits of a wide anchorage and coupler size range, with very thin slab depths and low reinforcement requirements, plus a very small minimum centre spacing and slab thickness at low concrete strength. It all adds up to smaller, lighter and stronger tendons for post-tensioning flat slabs - and at lower cost than previously. We had the confidence of knowing it had been rigorously tested - and were really pleased with the result. Given the scale of the Foodstuffs post-tensioned floor, not to mention its place as one of the largest in the world and the requirement for it to withstand extremely heavy loads, the new CONA CMF S2 system is a welcome addition to the BBR range. The team is looking forward to using it for other projects - and perhaps adding to the tally of post-tensioned flooring undertaken for Foodstuffs, which now stands at a whopping 190,000 m2. Article originally appeared in Connaect, the magazine of the global BBR Network of Experts.
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TEAM & TECHNOLOGY Developer - Auckland International Airport Architect - Eclipse Architecture Engineer - Day Consultants Main contractor - Macrennie Commercial Construction Technology - BBR VT CONA CMF flat BBR Network Members - BBR Contech (New Zealand)
ADDING UP THE NUMBERS Since 1983, BBR Contech has delivered many square meters of post-tensioned floor slabs. The breakdown below shows the area of slabs they have constructed by industry sector. SECTOR m2 Logistics 874,867 Retail 637,664 Manufacturing 474.239 Dairy 446,700 Ports 123,600 Multi-use 55,300 Other 49,085 Transport 47,200 Residential 42,000 Healthcare 27,000 Agriculture 15,000 Civil 12,500 Accommodation 6,500 Office 5,000 Fisheries 3,760 Energy 3,500 TOTAL 2,823,915
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Engineering PhD student Sabina Piras and Professor Alessandro Palermo. Image University of Canterbury.
HOW TO BUILD QUAKE-PROOF BRIDGES ON UNCERTAIN GROUND AFTER THE CANTERBURY AND KAIKŌURA EARTHQUAKES, THERE HAS BEEN INCREASED INTEREST IN CREATING MORE EARTHQUAKE-RESILIENT BRIDGE INFRASTRUCTURE IN AOTEAROA NEW ZEALAND. IN RESPONSE, RESEARCHERS AT THE UNIVERSITY OF CANTERBURY (UC) HAVE DEVELOPED A LOW-DAMAGE SOLUTION FOR BRIDGES THAT WOULD YIELD LITTLE TO NO DAMAGE IF HIT BY A STRONG EARTHQUAKE. 30 concrete
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The research is being led by UC Civil Engineering PhD student and chartered bridge engineer Sabina Piras originally from the United States, under the supervision of Professor Alessandro Palermo and Associate Professor Gabriele Chiaro at UC’s College of Engineering. The team has developed an alternative earthquake-resilient solution, also referred to as “low-damage”, for designing and building bridge infrastructure. Current earthquake design philosophy prevents the collapse of bridge infrastructure as a result of a large-magnitude earthquake, but that does not mean that bridges won’t be significantly damaged, says Professor Palermo. Road closures and repairs can have a significant social and economic impact as seen in the Canterbury and Kaikōura quakes, which brought the affected regions to a standstill and cost the economy millions. The researchers have developed a solution which, through the combination of selfcentring rocking bridge columns, can achieve large displacements with little to no damage compared to conventional bridge columns. A rocking column is comprised of two main structural components: one or multiple high strength bars that act like rubber bands to recentre the column, and several conventional steel bars that are detailed to dissipate energy and can be easily replaced if heavily damaged. “When an earthquake occurs, the column rocks over the foundation. The joint where the rocking motion happens is designed and detailed such that it can be easily repaired in a very short time,” says Piras. The repair work on the joint could be done over one night closure, preventing major traffic disruption, she says, in comparison to current construction methods that can take months or even years to fix or rebuild. The 2016 Kaikōura earthquake had a major impact on the transport network with damage, landslides and liquefaction affecting over 900 bridges. After visiting Kaikōura, the researchers
understood the need to know how lowdamage rocking solutions perform in various soil conditions. “It’s like driving a Ferrari on the road or rough terrain; its performance will not be the same,” says Professor Palermo. The researchers investigated the influence of different soil types on the low-damage rocking column system and developed a novel and simplified testing technique to simulate this complex problem. “The soil we build our infrastructure on varies so much throughout New Zealand, and we must understand how additional soil movements in an earthquake influence the rocking behaviour of our columns,” says Piras. “The majority of New Zealand bridges are built on single, large-diameter piles that, although big and stiff, are still susceptible to movements in an earthquake. Structural bridge researchers have validated the performance of low-damage rocking bridge columns through experimental testing assuming that the foundations are fixed. However, we have recognised that this incorrectly predicts the behaviour of the system, and we are the first to study the influence of soil-foundationstructure interaction on low-damage rocking bridge columns,” she says. The novelty of the solution stands on its simplicity to build. “I have worked on several different, lowdamage bridge systems and it seems the main barrier to implementation has been the slightly higher cost and risk associated with this novel design. I consider the Wigram-Magdala Link Bridge in Christchurch the Tesla of bridges, and would like to see more of these seismic solutions being implemented,” Professor Palermo says. The researchers have expanded on past research and application of post-tensioned rocking bridge columns and have developed a cost-effective solution aimed at engineers and constructors to start adopting sooner.
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Structural Engineering Laboratory Manager John Maley, Engineering PhD student Tom Francis and Engineering Professor Tim Sullivan are part of a University of Canterbury research team testing a new base isolation system that they hope will make New Zealand houses safer in an earthquake. Image University of Canterbury.
NEW BUILDING SYSTEM AIMS TO MAKE KIWI HOMES ‘SAFE AS HOUSES’ IN A QUAKE A NEW, AFFORDABLE BUILDING SYSTEM TO MAKE NEW ZEALAND HOMES MUCH SAFER IN AN EARTHQUAKE, AVOIDING COSTLY REPAIRS AND STRESSFUL INSURANCE CLAIMS, IS BEING TESTED AT THE UNIVERSITY OF CANTERBURY (UC). A prototype base isolation system for residential houses has been developed by Professor of Structural Engineering Tim Sullivan and his team, and is currently being put through its paces on a ‘shake table’ in UC’s Structural Engineering Laboratory. A room has been specially built for the trial with timber framing and GIB-lined walls on a concrete slab foundation. The structure is positioned on top of the newly developed, steel base isolation units. Underneath this, a shake table – one of the largest in New Zealand – is being used to recreate ground movements recorded at various locations during the damaging Canterbury earthquakes, as well as other strong historical earthquakes and a simulated Alpine Fault quake. 32 concrete
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The research is part of a broader UC and QuakeCoRE project that is developing a range of solutions for low-damage housing in New Zealand. Results so far show the base isolation units are effective and would have withstood the 20102011 Canterbury quakes and 2016 Kaikoura earthquakes (7.1 and 7.8 magnitude respectively), as well as an Alpine Fault scenario, without the room needing any repairs. Professor Sullivan’s goal is to keep the seismic system as low-cost as possible so it can be widely adopted by homeowners around the country, making their houses significantly safer during future earthquakes. “What’s been motivating me on this project is the idea of developing something that would avoid damage to housing in a major earthquake, or at
least make the likelihood of damage very low. “We think what we’ve come up with will prevent damage, and it doesn’t cost an arm and a leg. It also promises to reduce the disruption caused by a major quake, helping communities recover more quickly,” he says. Base isolation systems, developed to prevent or minimise damage during an earthquake, are primarily used in commercial or civic buildings in New Zealand because they are usually expensive and require specialised engineering. But the UC research team - which includes Engineering PhD student Tom Francis and Structural Engineering Laboratory Manager John Maley, with international support provided by Professor Andre Filiatrault, based in Italy - has created a new type of base isolation system that’s designed for residential houses. Their aim is to keep the total cost of manufacturing and installing the base isolation system to about $15,000 for a typical threebedroom house. A key to achieving this is the simple nature of the devices, which are expected to cost about 10 percent of the cost of base isolation devices currently used in commercial building projects. Professor Sullivan says houses in New Zealand currently perform well in terms of saving people’s lives, but there is room for improvement in terms of preventing damage to the structure and its contents. “Very few people die in houses during an earthquake, but $16 billion of the $40 billion paid out by the Earthquake Commission following the Canterbury earthquakes was for damage in the
residential housing sector. While around half of these losses were linked to ground damage [liquefaction and lateral spreading], the damage to houses caused by ground shaking was significant and needs to be reduced. “Research has shown that the most upsetting thing for a lot of people wasn’t the earthquake itself, it was dealing with insurance claims, the potential loss of value for their houses, and the damage to their belongings. If we can avoid that, then I think there will be psychosocial benefits.” So far, testing has shown the system is able to limit building deformations, preventing damage to walls and cladding, and keeping floor and roof accelerations low. This reduces the likelihood of damage to homes and their contents. “We think it will also reduce problems caused by torsion, or twisting, that can occur with some house designs during a quake,” Professor Sullivan says. “Once we get a few building companies doing this it will become more competitive and more affordable. We’re also hoping it could lend itself to faster construction and modular housing, which could be useful in combating the current housing shortages.” He is applying for more research funding so the system can be further developed and improved. Tom Francis says the current testing phase using an actual structure allows the team to model residential buildings more accurately. “It means we are able to understand how much money can be saved over the lifetime of a residential building by limiting earthquake damage using the base isolation system.”
HOW DOES THE NEW BASE ISOLATION SYSTEM WORK? The main hurdle to overcome during the design stage for the innovative system was balancing the need for a house to be stable in high winds but also able to flex and absorb shock from an earthquake. The system is created by installing several steel base isolation units under the concrete foundation of a house, which work in a similar way to traditional piles. The concrete slab includes steel plates that float and slide on small round discs in the units, which Professor Sullivan calls ‘pucks’, allowing the house to move around in a quake and absorb the displacements and accelerations imposed by ground shaking. The system is compatible with common building techniques for New Zealand houses and can be used under steel and timber-framed buildings or other typical structures. It is designed to be easy to repair after an earthquake and as sustainable as possible, with recycled, biodegradable cardboard used to create a cavity under the foundation.
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STRIATUS - THE FIRST OF ITS KIND 3D CONCRETE PRINTED ARCHED BRIDGE GRABBING HEADLINES, THE STRIATUS PROJECT INVOLVED THE BLOCK RESEARCH GROUP (BRG) AT ETH ZURICH AND ZAHA HADID ARCHITECTS COMPUTATION AND DESIGN GROUP (ZHACODE), IN COLLABORATION WITH INCREMENTAL3D (IN3D), MADE POSSIBLE BY HOLCIM. Striatus is an arched, unreinforced masonry footbridge composed of 3D-printed concrete blocks assembled without mortar. Exhibited at the Giardini della Marinaressa during the Venice Architecture Biennale until November 2021, the 16x12 m footbridge is the first of its kind, combining traditional techniques of master builders with advanced computational design, engineering and robotic manufacturing technologies.
A NEW LANGUAGE FOR CONCRETE
The name “Striatus” reflects its structural logic and fabrication process. Concrete is printed in layers orthogonal to the main structural forces to create a “striated” compression-only funicular structure that requires no reinforcement.
STRENGTH THROUGH GEOMETRY
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Proposing a new language for concrete that is structurally informed, fabrication aware, ecologically responsible and precisely placed to build more with less, Striatus optimises the interrelated properties of masonry structures, 3D concrete printing (3DCP) and contemporary design; presenting an alternative to traditional concrete construction.
Striatus is an unreinforced concrete structure that achieves strength through geometry. Concrete can be considered an artificial stone that performs best in compression. In arched and vaulted structures,
material can be placed precisely so that forces can travel to the supports in pure compression. Strength is created through geometry, rather than an inefficient accumulation of materials. This presents opportunities to significantly reduce the amount of material needed to span space.
balustrades) to the supports in pure compression. Advanced discrete element modelling (DEM) was used to refine and optimise the blocks’ stereotomy and to check the stability of the entire assembly under extreme loading cases or differential settlements of the supports.
Striatus’ bifurcating deck geometry responds to its site conditions. The funicular shape of its structural arches has been defined by limit analysis techniques and equilibrium methods, such as thrust network analysis, originally developed for the structural assessment of historic masonry vaults. Its crescent profile encompasses the thrust lines that trace compressive forces through the structure for all loading cases.
The bridge’s 53 3DCP voussoirs have been produced using non-parallel print layers that are orthogonal to the dominant flow of forces. This avoids delamination between the print layers as they are held together in compression. The additive manufacturing process ensures the structural depth of the components can be achieved without producing blocks with a solid section, hence reducing the amount of material needed compared to subtractive fabrication methods or casting.
Steel tension ties absorb the horizontal thrust of the arches. Neoprene pads placed in between the dry-assembled blocks avoid stress concentrations and control the friction properties of the interfaces, echoing the use of lead sheets or soft mortar in historical masonry construction. In plan, the boundaries of the structure form deep arches that transfer horizontal loads (for example, from visitors leaning against the
Striatus follows masonry structural logic on two levels. As a whole, the bridge behaves as a series of leaning unreinforced voussoir arches, following the same structural principles as arched Roman bridges in stone. Locally, on the level of the voussoir, the 3DCP layers behave as traditional brick masonry evident in the inclined rows of bricks within Nubian or Mexican vaulting.
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SUSTAINABLE DIGITAL CONCRETE Circular by design, Striatus places material only where needed, significantly reducing its environmental footprint. Built without reinforcement and using dry assembly without binders, Striatus can be installed, dismantled, reassembled and repurposed repeatedly; demonstrating how the three R’s of sustainability (Reduce, Reuse, Recycle) can be applied to concrete structures. Reduce: Lowering embodied emissions through structural geometry and additive manufacturing that minimises the consumption of resources and eliminates construction waste.
Placing concrete only where needed, 3DCP minimises the amount of material required, while the low-stress, compression-only funicular geometry of Striatus proposes the further development of 3DCP that will enable the use of much lower-strength printable materials. Compared to embedded reinforcement in concrete, Striatus uses external ties to absorb the thrust of its arched shape.
Reuse:
Improving circularity and longevity. Unlike conventional reinforced concrete structures, Striatus is designed to be dry assembled without any binder or glue, enabling the bridge to be dismantled and reused in other locations. Its funicular design ensures the 3DCP blocks experience low stresses throughout their use, resulting in no loss of structural integrity. Striatus separates components in compression and tension, ensuring external ties can be easily accessed and maintained, resulting in a longer lifespan for the entire structure.
Recycle: By ensuring different materials are separated and separable, each component of Striatus can easily be recycled with minimal energy and cost. 3D printing also avoids the waste and costs associated with single-use moulds. Additionally, the component materials within Striatus remain separate and separable with the use of mechanical connections such as simple dry contacts between the voussoirs rather than chemical glues or binders, ensuring a simple, low-energy recycling process at the end of the elements’ life.
3.5m Top of Balustrade
2.5m Top of Deck
G 0m
Masonry Bridge
2.0
A 2.0
B
N
IO AT EV EL A
2.0
2.0
A
NB
ATIO ELEV
2.5m 3.5m
G 0.0m
B
ELE
.7
VA TIO
11
NC
16
.6
2.0
Masonry Bridge
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ROBOTIC 3D CONCRETE PRINTING Unlike typical extrusion 3D printing in simple horizontal layers, Striatus uses a two-component (2K) concrete ink with corresponding printing head and pumping arrangement to precisely print non-uniform and non-parallel layers via a 6-axis, multi-DOF robotic arm. This new generation of 3D concrete printing in combination with the arched masonry design allows the resulting components to be used structurally without any reinforcement or post-tensioning. To prevent misalignment between the direction of structural forces and the orientation of material layers that arises from typical shape-agnostic slicing of explicitly modelled geometry, a customdeveloped design pipeline was formulated for Striatus to ensure that its printed layers are wholly aligned with the direction of compression forces throughout the entire bridge and also locally through each 3D-printed block. To address issues and challenges that could prevent in-between stability during printing, the coherence and feasibility of the gradually evolving print paths have been modelled using a Functional Representation (FRep) process.
vaulted, rib-stiffened, unreinforced concrete floors being developed by the Block Research Group in partnership with Holcim, Striatus proposes an alternative to the standard inefficient floor slabs within any building. Compared to typical reinforced concrete flat floor slabs, this new floor system uses only 30 percent of the volume of concrete and just 10 percent of the amount of steel. The very low stresses within the funicular structure also enable the use of low-embodied-carbon concrete that incorporates high percentages of recycled construction waste. Prefabricated and dry-assembled, and therefore fully demountable and reusable, this floor system is easily and cleanly recyclable at end-of-life.
This process encodes and continuously checks rules of minimum overlap, maximum cantilever between print layers and print length, print speed and the volume of wet concrete extruded. These measures, typically used in horizontally layered 3DCP, have been advanced and refined to work on an inclined-plane setting. COMPUTATIONAL DESIGN-TOCONSTRUCTION INTEGRATION Integrating design, engineering, fabrication and construction, Striatus redefines conventional interdisciplinary relations. The precise manufacturing of the blocks was enabled by well-defined data exchange between the various domain-specific software toolchains involved in the process. This co-development approach was facilitated through the use of COMPAS, an opensource computational framework for collaboration and research in the AEC industry, which enabled interaction among the key players of the project, working together in five different countries, under a very tight schedule and budget, at a time when travelling was not possible. DISRUPTIVE OUTLOOK Striatus offers a blueprint for building more with less. Created with the same structural principles and a similar fully-integrated computational designto-fabrication approach that form the basis of the
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CONCRETE NZ LIBRARY LISTED BELOW IS A SELECTION OF RECENTLY ACQUIRED MATERIAL BY THE CONCRETE NZ LIBRARY. MEMBERS CAN EMAIL LIBRARY@CONCRETENZ.ORG.NZ TO BORROW. EMBODIED ENERGY AND DESIGN: MAKING ARCHITECTURE BETWEEN METRICS AND NARRATIVES BY DAVID BENJAMIN (EDITOR) Architecture accounts for one third of global carbon emissions, energy consumption and waste. Buildings are increasingly understood to impact broader ecologies. Yet embodied energy – the various forms of energy required to extract raw matter, to produce and transport building materials and to assemble a given building – remains largely underexplored. This book reconsiders the act of making a building as energy expenditure and asks questions about related scales, methods of analysis and design opportunities. How might new technologies and materials challenge default positions on sustainability? Should we think of buildings as dynamic systems connecting multiple sites rather than as static and isolated objects? Does the duration of architecture extend beyond the life of a built structure? By addressing these questions, architects may discover not only new ways of building, but also new forms of creativity. Essays and studies by various established contributors are accompanied by graphics, plans, drawings and photographs. RECENT ADVANCES ON GREEN CONCRETE FOR STRUCTURAL PURPOSES BY JOAQUIM A.O. BARROS, LIBERATO FERRARA & ENZO MARTINELLI (EDITORS) This book is mainly based on the results of the EU-funded UEFP7 Project EnCoRe, which aimed to characterize the key physical and mechanical properties of a novel class of advanced cementbased materials incorporating recycled powders and aggregates and/or natural ingredients in order to allow partial or even total replacement of conventional constituents. The project objectives were to predict the physical and mechanical performance of concrete with recycled aggregates; to understand the potential contribution of recycled fibres as a dispersed reinforcement in concrete matrices; and to demonstrate the feasibility and possible applications of natural fibres as a reinforcement in cementitious composites. The opening chapters explain the material concept and design and discuss the experimental characterization of the physical, chemical, and mechanical properties of the recycled raw constituents, as well as of the cementitious composite incorporating them. The numerical models with potentialities for describing the behaviour at material and structural level of constructions systems made by these composites are also presented. Finally, engineering applications and guidelines for production and design are proposed.
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CONTACTS
Concrete NZ Readymix Sector Group Ph (04) 499 0041 Convenor: Rob Gaimster Chair: Richard Sands
THE NEW NET ZERO: LEADING-EDGE DESIGN AND CONSTRUCTION OF HOMES AND BUILDINGS FOR A RENEWABLE ENERGY FUTURE BY BILL MACLAY The new threshold for green building is not just low energy, it’s net-zero energy. Architect Bill Maclay charts the path for designers and builders interested in exploring green design’s new frontier - net-zero-energy structures that produce as much energy as they consume and are carbon neutral. In a nation where buildings use 40 percent of the total fossil energy, the interest in net-zero building is growing among both designers interested in addressing climate change and consumers interested in energy efficiency and long-term savings. Maclay makes the case for a net-zero future; explains net-zero building metrics, integrated design practices, and renewable energy options; and shares his lessons learned on net-zero teambuilding. Designers and builders will find a wealth of state-of-the-art information on such considerations as air, water, and vapor barriers, embodied energy, residential and commercial net-zero standards, monitoring and commissioning, insulation options, costs and more.
LIBRARY QUIZ To go in the draw to win a copy of The New Net Zero: Leading-Edge Design and Construction of Homes and Buildings for a Renewable Energy Future by Bill Maclay answer the following question: The 2016 Kaikōura earthquake had a major impact on the transport network. How many bridges were damaged or affected by landslides and liquefaction? See page 31. Email your answer to library@concretenz.org.nz. Entries close Friday 26 November 2021.
Concrete NZ Masonry Sector Group Ph (04) 499 8820 Convenor: Ralf Kessel Chair: Dene Cook
Concrete NZ Precast Sector Group Ph (04) 499 8820 Convenor: Dave McGuigan Chair: John Marshall
Concrete NZ Learned Society Ph (09) 536 5410 Convenor: Adam Leach Events Manager: Allan Bluett President: Nic Brooke
Concrete NZ Reinforcing Stakeholder Group Ph (04) 499 8820 Convenor: Dave McGuigan Chair: Kelvin Busbridge
Congratulations to Colin Wood of Precast Systems Ltd, who correctly answered the Vol. 61 Iss. 02 Library Quiz to receive a copy of Flying Panels: How Concrete Panels Changed the World Pedro Ignacio Alonso and Hugo Palmarola.
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Almost two decades ago, we created the world first flooring system and constructed Australasia’s largest steel fibre reinforced Jointless slab.
After more than 20 years, BOSFA are still the market leaders in innovation and engineering, constantly looking for ways to provide value to every project we are involved in.
2021
Our innovative Dramix 4D flooring solution for Jointless slabs is another example of how we continue to lead the market.
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