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1 COMPARE AUTOCLAVED AERATED CONCRETE AAC WALLS WITH DINCEL DISCLAIMER The information contained in this document is intended for the use of suitably qualified and experienced building professionals. This information is not intended to replace design calculations or analysis normally associated with the design and specification of buildings and their components. Dincel Construction System Pty Ltd accepts no liability for any circumstances arising from the failure of a specifier or user of any part of Dincel Construction System to obtain appropriate professional advice about its use and installation or from failure to adhere to the requirements of appropriate Standards and Codes of Practice, and relevant Building Codes. Copyright Page 1 of 28 Telephone: (612) Quarry Road construction@dincel.com.au Facsimile: (612) Erskine Park, NSW 2759 Website: PO Box 104, St Clair, NSW 2759 A.B.N AUSTRALIA

2 INDEX (A) FOREWORD (B) COMPARISON BETWEEN DINCEL AND AAC SYSTEM 1. Energy Comparison 2. Joints 3. External Façade Walls and Finishes 4. Cost and Speed of Construction Comparison (C) CASE STUDY DINCEL vs AAC SYSTEM Cost calculation Dincel vs AAC System with conventional floors. Cost calculation Dincel vs AAC System with Ultrafloor. (D) CONCLUSION Copyright Page 2 of 28

3 (A) FOREWORD An experienced costing estimator considers the overall cost for each floor level, including the slabs, columns, walls used within the space under consideration. Any structural design engineer can verify that a structure consisting of concrete slabs, columns and infill walls between the sole occupancy units of an apartment type of building is required to have a thicker slab (AS3600 Concrete Code Fire Requirement) than the floor slabs that are being carried by loadbearing walls. WHEN APARTMENT FLOOR SLABS ARE SUPPORTED BY LOADBEARING DINCEL WALLS: The floor slabs thickness is reduced, mesh reinforcement is allowed to be used in lieu of reinforcement consisting of bars and post tensioning. The floor slabs and Dincel Walls are built simultaneously by one trade only. THIS ACHIEVES MINIMUM 28% COST AND UP TO 50% TIME SAVING. The conventional frame structure consisting of floor slabs and columns requires infill walls for tenancy or sole occupancy units. Infill walls can be AAC walls, brick (clay or concrete) and walls made out of plasterboard. These infill walls must have appropriate fire and acoustic ratings and they are non-load bearing walls. They are called infill walls because these walls are placed after construction of the columns and slabs. The infill walls are subject to structural requirements by the Australian Earthquake Code where the walls must be adequately restrained at least at the top and bottom of the walls to prevent these walls from falling like a pack of cards during an earthquake or heavy wind loading event. The infill walls must have gaps all around to accommodate building movements for thermal, slab deflection and wind/earthquake loadings. These gaps in turn must be sealed for weathering, fire and acoustic purposes. Autoclaved Aerated Concrete (AAC) is a lightweight precast concrete building material (in block or panel form) that is cured under elevated pressure inside special kilns called autoclaves. Dincel is a permanent polymer formwork which can be filled with any type of concrete, i.e. conventional concrete (with lightweight or normal density aggregates) or aerated concrete (i.e. lightweight concrete). Dincel-form as tested by CSIRO-Australia provides waterproof walls (Download Waterproof Walls), and as a result, because durability of concrete with Dincel is not a concern, significant reductions in cement usage can be achieved. Dincel also allows the use of untreated fly ash, corals, beach sand, coal, shale, volcanic rocks and mining mineral wastes in concrete making. (Download Dincel Solution for Concrete Problems and Cement Minimisation). The following comparison is between AAC walls and Dincel Wall. Please refer (download) Costing Analysis for the comparison of infill walls other than AAC walls. Copyright Page 3 of 28

4 (B) COMPARISON BETWEEN DINCEL AND AAC SYSTEM 1. ENERGY COMPARISON AAC walls claim energy efficiency because of the low cement quantity use. AAC walls are mainly used as non-load bearing walls in apartment type of buildings due to their low compressive strength. Dincel-Walls do not need to use more cement than AAC walls if the walls are utilised for non-load bearing purposes as well. Non-load bearing Dincel can be used as low as 3MPa compressive strength of lightweight concrete. On the other hand, Dincel can also use untreated fly-ash which represents significant assistance to the overall energy efficiency. (Download Dincel-Fly Ash Cement Concrete) However, readers must always consider the overall building system. AAC walls can only be used within a frame system incorporating column-slabs of an apartment building. As previously explained, an AAC System will always use more concrete and more steel in floor slabs and columns. Please refer to the following case study; 50mm reduction in concrete at each floor slabs, and 77kg/m 2 steel in lieu of 130 kg/m 2 represent substantial embodied energy and CO 2 reduction when an AAC system is compared to Dincel. Refer (download) Energy Efficiency in Building Construction Embodied Energy as an example. 2. JOINTS AAC panels have joints at random centres. These joints require special treatments. A wall made out of AAC panels also requires shrinkage, expansion and building movement joints due to thermal, building slab deflection and for earthquake purposes. These joints in between the AAC panels will open up due to building movements. Therefore, AAC walls will always require cavity construction as shown in Figure 1. This represents space loss in comparison to Dincel. Dincel is a monolithic wall system and does not require any wall joints. Dincel Walls of up to 140m long have been built without any joints and without any horizontal crack control reinforcements. (Download Common Engineering Questions Items No: 1, 2, 4 and 11) The Dincel-Wall, being monolithic, joint free and protected by the waterproof-polymer encapsulation provides additional resiliency and ductility to concrete. Dincel, being ductile and non-brittle, cannot crack because of thermal, building and earthquake movements (up to magnitude 9 as tested by UTS), and as a result, Dincel Wall s footings are eliminated or the footing size is significantly reduced. However, because of their joints, the AAC panels (or brittle materials such as masonry brick-clay/concrete and reinforced masonry block walls) will always be subject to cracking at the panel joints and require substantial footings, especially in reactive soil conditions. The difference in the cost and time of construction of the footings for houses or multi-level buildings can be significant. 3. EXTERNAL FAÇADE WALLS AND FINISHES (Download Finishes for Dincel External Finishes) AAC walls cannot be left exposed to environmental conditions, e.g. soil, water, etc. as it will damage the cellular structure of the walls. AAC is a porous material and like any other porous material is subject to capillary action, i.e. vapour transmission. Dincel can be a single skin façade wall which is a total vapour-proof and waterproof barrier which is not subjected to vapour transmission (as tested under 6m head of water pressure by CSIRO). All porous substrates, including AAC panels, fibre-cement sheets, masonry and even in-situ concrete absorb vapour within the façade walls. The conventional commercially available paints/renders are also porous, hence cannot stop the vapour penetration into the façade walls. (Refer Figure 1). Copyright Page 4 of 28

5 The vapour within the porous walls moves to the exterior atmosphere when the ambient condition changes. The paint/render finishes bubbles because vapour is trapped between the wall and the paint/render finishes. Therefore, to prevent the paint from bubbling with any material subjected to capillary action including AAC walls, fibre-cement sheets, concrete, masonry block, etc, the following must take place: Seal the face of the AAC panels, including joints, with an impervious membrane type of sealant to stop the ingress of vapour transmission before application of the paint/render. AAC panels are normally used as non-load bearing infill panels within the structures carried by a column-slab frame system which is always subject to shrinkage/temperature movements, structural settlements and earthquake movements. These movements can be anywhere between 5 mm to 100mm, depending on the structure s size and magnitude of earthquake forces. It is therefore unrealistic to assume that joints of AAC panels will not open up and let moisture in within the wall (for the same reason, façade walls with AAC panels must have cavity construction) and, consequently may result in paint bubbling. The owner must accept the fact that facades made out of AAC panels will require ongoing maintenance to protect the building from vapour transmission. For detailed information (download) Breathable Wall/FAQ/Sustainability/Question 11). 4. COST AND SPEED OF CONSTRUCTION COMPARISON It is important to understand why Dincel is a faster construction system (Download Why Dincel is Faster to Build). AAC panels have limited structural capacity only due to their low compressive strength capacity (approximately 4Mpa). As a result, most commonly AAC panels are not used as structural elements but used as infill walls in a multi-level apartment building. Building codes around the world, including Australia (AS which mainly follows the New Zealand Earthquake Code) requires that infill walls must be secured to the structure so that they do not fall over like a pack of cards during the event of an earthquake and kill people. In addition to this requirement, the building codes also require fire and acoustic seals to fill the gaps required for floor deflection and earthquake reasons. These gaps are normally a minimum of 20mm for structural movements; however they can be 50mm (this figure gets bigger with increasing building height) in a well-designed 12 storey building subject for a magnitude 7 earthquake. These required details illustrated in Figure 3 are time consuming and must be installed by skilled labour under strict supervision. This level of skilled labour is limited and only available in major urban centres of reasonably advanced economies around the world. The calculated gaps specified by earthquake design engineers must be adhered to otherwise the structure must be designed for exacerbated earthquake loads. (Download The Roles of Masonry Infill Walls in an Earthquake). The AAC panels are not classified as masonry walls (clay brick or concrete brick are masonry walls), however they will behave the same way as masonry walls in the event of an earthquake. The structure with Infill AAC walls shown in Figure 3: WILL BE SLOWER to build when compared with DINCEL because of the following reasons: The multi-level buildings utilising AAC panels require concrete columns as load bearing elements. The installation of Dincel-Wall will be completed before the completion of the formed columns. Refer (Download Dincel Installation Video) to judge the speed of Dincel s construction. Being structural and load bearing, Dincel-Wall does not require additional columns. This way, the structural walls, i.e. load bearing walls between sole occupancy units are completed at the same time as the floor slabs. Copyright Page 5 of 28

6 The columns of a structure are normally placed within the infill walls which are required to have acoustic and fire rating (refer Figure 3). In lieu of columns and infill walls, Dincel-Walls are used as load bearing walls which necessitates the installation of Dincel-Wall prior to concrete pouring of each floor slab. The position of Dincel- Wall must therefore be located in a correct position as being the wall that separates the sole occupancy units from each other. However, as an alternative solution the position of columns must be located in a correct position as well. As Dincel-Walls are placed in the same alignment with the columns, the columns as well as Dincel-Walls must be erected in the correct position, and Dincel-Wall is installed much faster than the three columns shown. THEREFORE, THE INSTALLATION OF DINCEL-WALLS WILL NOT COMPROMISE THE CRITICAL PATH OF THE CONSTRUCTION IF DINCEL-WALLS ARE USED IN LIEU OF COLUMNS. The slab-column system requires additional time to implement the elaborate details shown in Figure 3 which is associated with infill panels such as AAC walls. WILL BE DEARER to build when compared with DINCEL because of the following reasons: Refer comments in FOOTINGS COST in previous JOINTS comparison. In addition to the floor slab, to stiffen the column-slab junction at each floor level, structures designed for significant earthquake forces must have beams. None of the earthquake countries that are subject to significant earthquake forces allow the column-slab junction without stiffening with beams. This issue is overlooked by many countries, including Australia, that are not located at the earthquake tectonic plate boundaries assuming that significant earthquake possibility occurring is low. The presence of Dincel-Wall eliminates the need for beams, as well as columns. This significantly affects the strength against earthquake forces, construction time and costs. The following case study clearly demonstrates that the structural solution with DINCEL is a 28% CHEAPER solution at each typical floor level of an apartment type of building. Dincel can further reduce the cost of transfer slabs by 75%. Copyright Page 6 of 28

7 FIGURE 1 Copyright Page 7 of 28

8 FIGURE 2 Copyright Page 8 of 28

9 (C) CASE STUDY DINCEL vs AAC SYSTEM Copyright Page 9 of 28

10 AAC WALL SYSTEM vs DINCEL CONSTRUCTION SYSTEM AAC SYSTEM DINCEL CONSTRUCTION SYSTEM AS CONCRETE STRUCTURES CODE REQUIRE AAC WALL SYSTEM Minimum 200mm thick slab. No mesh reinforcement allowed. Steel reinforcement rate is 130kg/m 3 RESULT: Including Time Saving EVERY 3 RD FLOOR COMES FREE OF CHARGE DINCELSYSTEM Minimum 150mm thick slab (for acoustic reasons) with SL92 mesh use allowed. Steel reinforcement rate is 77kg/m 3 Copyright Page 10 of 28

11 Copyright Page 11 of 28

12 BUILDING WITH DINCEL CONSTRUCTION SYSTEM Results in Less Concrete / Steel and Time Dincel System No columns, loadbearing Dincel Wall and one-way floor system. Floor Systems Timber floors, in-situ concrete or precast flooring (Ultrafloor, precast planks). Bondek, Condeck, Kingfloor, etc. WALL FLOOR SLAB DETAIL AT DINCEL WALL The steel bars shown are Earthquake / Wind Engineering requirement. Copyright Page 12 of 28

13 DINCEL LOADBEARING WALLS Copyright Page 13 of 28

14 BUILDING WITH AAC SYSTEM BUILDING CODES REQUIREMENT FOR THE DETAILS BETWEEN STRUCTURE AND AAC WALLS WALL-FLOOR DETAIL AT AAC WALL AAC System: Non-loadbearing party walls shown above are placed between the columns. FIGURE 3 WALL-COLUMN DETAIL AT AAC WALL Copyright Page 14 of 28

15 AS CONCRETE STRUCTURES CODE Mandatory from May 2011 Frame Structures with AS Minimum slab thickness is 200mm. Mesh reinforcement cannot be used. DINCEL load bearing system allows 150 mm thick slabs and mesh reinforcement. Copyright Page 15 of 28

16 BS EN : 2004 EUROCODE Flat Plates : a 90 minute fire requires 200mm thick slab (Table 5.9). One/two way slabs by beams or loadbearing Dincel Wall : a 90 minute fire requires 100mm thick slab (Table 5.8). COLUMN-SLAB SYSTEM Copyright Page 16 of 28

17 150mm THICK SLAB ACOUSTIC QUESTIONS If a 150mm thick wall for airborne sound complies with the BCA s deemed to satisfy condition. Why a 150mm thick slab would not comply for airborne sound purposes? The following SLR Acoustic Certificate is based on the Canadian s acoustic floor testing for 150mm slabs. There is no reason why your Acoustic Engineer would not agree with SLR s certification. Acoustic improvements to Australian buildings were originally introduced because of inadequate wall construction (e.g. brick walls with excessive wall chasing); not necessarily the poor performance of minimum 125mm thick slabs used then. Why would you waste extra concrete and steel resulting in an increase in the structural cost by a minimum of 20% if there is no evidence that a 150mm thick slab would not comply. IF YOU DON T ASK YOU WILL NOT ACHIEVE MONEY AND TIME SAVING Copyright Page 17 of 28

18 Copyright Page 18 of 28

19 Note: Floor finishes, internal partition walls, plasterboard, insulation, metal studs, finishes at party and façade walls are not included in the above cost analysis as they are common to both Dincel and AAC Wall System. Cost of finishing at the junction of the AAC Wall System and column not included. Copyright Page 19 of 28

20 Note: Floor finishes, internal partition walls, plasterboard, insulation, metal studs, finishes at party and façade walls are not included in the above cost analysis as they are common to both Dincel and AAC Wall systems. Copyright Page 20 of 28

21 Note: Floor finishes, internal partition walls, plasterboard, insulation, metal studs, finishes at party and façade walls are not included in the above cost analysis as they are common to both Dincel and AAC Systems. Copyright Page 21 of 28

22 TRANSFER SLAB DINCEL SYSTEM DINCEL CAN ELIMINATE COSTLY TRANSFER SLABS Transfer slabs are eliminated if party walls are placed in a right angle direction to the car parking aisle way below. Result: 150mm thick slabs Steel Rate is 77kg/m 3 instead of conventional 450mm to 600mm thick slabs with posttensioning or very heavy steel bars. Copyright Page 22 of 28

23 TRANSFER SLAB AAC WALL SYSTEM AAC WALL SYSTEM WILL ALWAYS RESULT IN VERY COSTLY AND TIME CONSUMING TRANSFER SLABS WHEN CAR PARKING COLUMNS AND SUPERSTRUCTURE COLUMNS ARE NOT ALIGNED. Result: To carry 8 storeys above: 450mm to 600mm thick slabs with post-tensioning and/or very heavy steel bars. More bulk excavation/more columns. Copyright Page 23 of 28

24 STRUCTURAL EFFICIENCY TYPICAL BUILDING CROSS SECTION Copyright Page 24 of 28

25 200 APARTMENTS, BRUCE, ACT 77 WEEKS CONSTRUCTION TIME REDUCED BY 26 WEEKS = 30% TIME SAVING GREEN CONCRETE = 50% CEMENT REDUCTION ACHIEVED Copyright Page 25 of 28

26 133 APARTMENTS : 5 11 PYRMONT BRIDGE ROAD, CAMPERDOWN 52 WEEKS CONSTRUCTION TIME REDUCED BY 26 WEEKS = 50% TIME SAVING Copyright Page 26 of 28

27 CEEROSE, 5 11 PYRMONT BRIDGE ROAD, CAMPERDOWN Copyright Page 27 of 28

28 (D) DINCEL SYSTEM vs AAC SYSTEM DCS IS CLEARLY A FASTER Construction. Slabs with mesh reinforcement will take significantly less time than slabs with bars / post-tensioning. Dincel Walls and floor slabs can be installed simultaneously. The AAC System requires columns to be installed first, then the floor slabs and then the AAC walls are installed between the columns. Column forming and steel reinforcement placement for 3 columns of the Case Study will take more time than installing Dincel Wall. (AAC walls yet to be installed). Minimum 28% COST EFFICIENCY at typical floor levels. Minimum 75% COST EFFICIENCY at the transfer slab level. Copyright Page 28 of 28