3.3 In-situ concrete measurement rules
The complete measurement rules for concrete works are outlined in Section 6 of the ANZSMM, providing standardised guidelines for quantifying concrete works in construction projects. The information to be included table within this standard includes both preamble notes and preamble items, which serve as key references for tenderers and quantity surveyors. The preamble notes direct tenderers to the Introduction, General Rules, and Recommendations section of the standard, as well as to relevant specification sections containing concrete details, such as material properties, concrete specimens, particulars of the concrete and the concrete placement conditions. The preamble items allow for an allowance to be made for sampling of the material, conducting tests, curing and protecting after the placement.
According to the standard, the measurement of the concrete is expected to provide the net dimension of the element. Following the items in the classification table, the reinforced and plain concrete for different strengths or mixes of concrete should be measured separately. Also, the separate classification applies to different floor levels unless the consecutive levels have similar floor plans and construction methods. In this case, the levels need to be identified in the description of the item.
The description of the concrete element plays an important role in the completion of the measurements stage of the concrete works to capture the condition of the process of concrete works. As such, the method of positioning the concrete works should be included within the description, such as whether it is compacted, placed in the position, or sprayed. The material or condition of the concrete placement also plays a part in description writing, especially when the concrete is placed into formwork, steelwork or between excavated faces in footings.
The units of measurement for the in-site concrete works can be “m2”, “m3”, “m” and “no” depending on the type of elements. The unit of measurement for common elements, such as footings, is m3. In case of measuring the volume for reinforced concrete, measurement rules outline no deduction of the reinforcement volume or structural steel unless the embedding steel element is a hollow element such as boxed, square hollow sections (SHS), rectangular hollow sections (RHS) or circular hollow sections (CHS).
As stated earlier, the measurement rules outline the net dimension of the element for the measurement of the concrete works, where the waste, making good after the removal of the formwork, joints, additional material for the tolerance of excavation and casting in all required material shall be considered within the pricing rate.
According to the standard, the measurement of concrete on different elements must follow their classification and the corresponding measurement process. This section introduces concrete elements separately and reviews their measurement and description considerations. For a more comprehensive understanding of the measurement procedures, pricing, and definitions, the authors encourage readers to refer Section 6 of the ANZSMM.
3.3.1 Blinding concrete
Blinding is a base layer of weak concrete for other foundation elements. It is usually 10 MPa or 15 MPa plain concrete, depending on the design specification. Blinding concrete can serve different purposes within the building structure, such as providing an accurate levelling surface for the foundation while sealing the underlying ground material. The drawings usually suggest a nominal thickness for blinding. Figure 3.3 demonstrates a blinding layer located below a pad footing in different views:
According to the standard, the unit of measurement for blinding is square metres (m²). The blinding needs to be classified as horizontal, sloping or vertical. It is required to state the thickness of the blinding within the description.
The horizontal blinding is commonly used in the project. When measuring the horizontal blinding, the area of the blinding on the plan can be measured.
3.3.2 Concrete for footings – pad footing and strip footing
Footings are the building elements that transfer the building load from other building elements, like columns or walls, to the ground. The size and shape of the footing depend on many factors such as the amount of the transferring load, the shape of the element above and the type of ground below (load bearing capacity of the soil), which will result in different types of footing such as pad footing, strip footing, raft footing, etc. The usual material of footings is reinforced concrete. Here are a few examples of various footings.
Pad footings are a type of footing that supports a concentrated element, such as a column. The pad footings are usually in a square or rectangular shape. They can be an isolated footing or interconnected with a linear structural element such as a ground beam, as shown in Figure 3.4.
Strip footings are a long, narrow type of footing that supports a linear element, such as walls, as illustrated in Figure 3.5.
Note that ground beams are very similar to strip footing but serve different purposes in buildings. Ground beams can be designed to connect other footings, such as pad footings.
According to the standard, the unit of measurement for concrete in a footing is m3. The measurement of the footings is classified separately based on their types, such as pad footing, strip footing and ground beams. Additionally, items such as pad footings are required to be further classified if they capture less than 1 m2 on the plan or more than 1 m2 on the plan. It is required to state the depth of the footing within the description or mention the diameter of the footing if relevant.
3.3.3 Concrete for beam
Beams are horizontal structural elements in a building that support other structural elements, such as slabs, walls, columns, and footing elements. Also, beams may transfer loads from slabs and walls to columns or footing elements. One of the usual materials for beams is reinforced concrete. Beams can be designed to be positioned on the ground or on the upper levels. Represented in Figure 3.6, beams are usually located below a slab to support the slab loads, while upstand beams are located above the slab.
Figure 3.6 also illustrates the types of beams in reference to the slab, namely the upstand beam, the attached beam and the isolated beam. The cyan-coloured area denotes the measurement of concrete for the beams.
According to the standard, the unit of measurement for concrete in beams is in m3. The concrete measurement of beams needs to be classified separately based on their types, such as isolated beam, attached beams and upstand beams. The concrete for the attached beams should be measured from the bottom of the slab. The concrete for the upstand beams should be measured from the top of the slab.
Ground beams are the linear structural elements that support slabs on ground, footings or walls. Ground beams are usually exposed to the soil and lie on the ground. The ground beams should be measured separately, where they are classified as a subcategory of the “footing” classification.
3.3.4 Concrete for slabs – raft slab, ground slab (slab on grade), suspended slab
The slabs are considered a flat, horizontal, or sometimes sloped layer of structural elements, usually made of reinforced concrete. The slabs are a common element used to form the floors, roofs, and foundations in buildings. Illustrated in Figure 3.7, the concrete slabs above the ground, known as suspended slabs, transfer the floor or roof load to other structural elements like beams and columns. In contrast, the slabs, which are directly on the ground, transfer the loads to the ground and can be considered structurally as a floor or foundation. The slab on ground (also known as a slab on grade) is a floor element that supports the loads directly to the ground.
As illustrated in Figure 3.8, a raft slab is a foundation element that supports loads from other structural elements, such as columns, and transfers these loads to the ground.
The unit of measurement for concrete in slabs is m³. The slabs are considered horizontal unless otherwise noted. The volume measurement of concrete slabs is classified and presented in 100 mm slab thickness intervals. The area measured for each slab classification shall be stated within the description of the item. The calculation of volume is commonly achieved by multiplying the surface area of the element by the thickness of the element. For example, the floor area of the slab multiplied by the thickness of the slab. The measurement of slabs is precise over the joining walls, beam thickenings and other concrete elements. In other words, there is no need to deduct any joining elements for the measurement of the slab area. Any slab projection, such as thickening similar items, needs to be included within the concrete slab measurement. Waffle slabs are a type of slab where waffle ribs and similar features attached to the slab need to be included in the measurement.
The sloped slabs less than 15 degrees, sloped slabs more than 15 degrees and cambered slabs are measured and categorised separately.
3.3.5 Concrete for columns
Columns are the structural elements that transfer the loads of structural elements above, such as beams and slabs, to the structure below, such as the footing system. Reinforced concrete is a common material used for columns. Columns can be designed as an isolated item or can be attached to a wall.
According to the standard, the unit of measurement for concrete in columns is m3. The columns are classified to be measured separately based on their types, such as isolated columns and attached columns. The attached column is classified to be included within the wall take-off item to which the element is attached. For example, if a concrete column is attached to a concrete wall and the specifications of the concrete for both elements are the same, the concrete measurement of the column should be considered and presented within the concrete measurement of the wall.
3.3.6 Concrete for walls
Concrete walls are strong, durable structures made of reinforced concrete. They are commonly used as sheer walls to sustain lateral forces such as wind and earthquakes or retaining walls to keep the soil and water in the sloped landscape.
Concrete walls are constructed either cast in place (in-situ) or made precast in a factory. These two types of concrete are classified differently. The structural drawing features the detail of in-situ concrete walls and indicates the “precast” if it is expected to be one. For example, the notes or the legend of the drawing may refer to the precast nature of the walls, or the detailed section may indicate “precast panel” as the material of the wall.
The concrete in a wall is measured in m3. The walls are classified into separate thickness stages of 50 mm. Also, the area of the wall should be expressed in the description. The attached columns or piers to the wall are classified within the concrete walls to be included within the concrete wall take-off.
