The Foundation and Slab Construction of a Dwelling under Construction - Coursework Example

Name Instructor Course Date Building and construction studies Table of Contents Table of Contents i Abstract 1 1. Introduction 1 1.1 Footings 1 1.2 Slab 3 2. Body of research 4 2.1 Construction of footing 4 2.2 Excavation 6 2.4 Construction of plinth wall 7 2.5 Termite treatment 8 2.6 Treatment of the edges of reinforcement 8 2.7 Design of reinforcement 8 2.8 Construction of the slab 9 2.9 Design of the slab reinforcement 9 2.10 Adverse effect of variance 10 Conclusion 11 Recommendations 11 Reference 12 Abstract Building and construction have been the principal activities in the field of civil engineering branch of civil engineering known as geotechnical engineering is especially concerned with foundation and retaining walls. In this report, significant emphasis was put on the foundation (pad footing) and slab construction of a dwelling under construction. A number of items were discussed among other are exaction of footing, termite treatment, reinforcement design, variance, etc. This investigation aimed at finding the code of practice by the builder, whether the builder has was using the right code of practice in Australia or any other applicable standard. A conclusion of the finding was made, and a recommendation was made basing on the results. Footing and slab construction 1. Introduction 1.1 Footings Foundation is one of the most critical geotechnical engineering studies that most designers and contractor are so keen of, and it takes most of the time for their study during design so that the safety of the building is attained. In geotechnical engineering, the foundation is the structural element that is in direct contact with the ground (soil) and transfers loads directly to the ground. Foundation part in the ground is called the footing. Foundation footing plays a great role in sustaining the structure and making it safe to use by the clients. In general, the foundation has the function of fully supporting the structure and its loads and safely transmitting all the loading to the soil (ground) that the structure permanently rests. Figure 1 shows transfer of load to the soil by pad footing the loads that foundations carry to the ground are imposed, dead, and wind loads and all the loads are taken to the soil the foundation in such that there is little or no settlement. A settlement that causes structural failure is referred to differential that is the cause because of soils having loose strata and due to overloading of the structure. For the structure to be safe, the settlement should be the uniform that allows the entire structural element to be in their safe position. Foundations are designed to resist loading from the structure and the seismic loading that occurs during the earthquake. During the construction of the building (in this case a dwelling house) the subsoil under the foundation undergoes compression, and the soil reacts to compression by exerting the vertically upward force against the loadings from the foundation. Whenever the foundation loading is more than the maximum safe bearing capacity, the foundation can easily move down, and this can lead to structural failure. Such a condition can be solved by increasing pad size of the foundation or using pile foundation. In this report, much emphasis was put on the construction process of the dwelling house under construction where a greater discussion was made on the type of material used in construction. The properties of the soil that support the suitability of the building for it to be safely used by the dwellers Foundations are of types namely; shallow and deep foundation. The Shallow foundation includes pad footing, strip, raft, mat foundation, etc. The Deep foundation includes pile foundation. 1.2 Slab The slab is the horizontal structural member that resists the imposed loads and dead loads and transfers them to the columns. The slab used in the construction of residential building is cast directly to the ground (foundation). The slab used in the construction of the dwelling house was reinforced concrete and has the thickness of 150 mm (solid slab) in reference to Australian standards. In the construction of the floor slab, there are a number of thermal considerations taken i.e. insulation of the floor slab. In the construction of the building to cater for insulation, the concrete floor is cast above the insulation layers for an example of expanded polystyrene to prevent the slab from being affected by heat from underground. The slab under construction is the solid slab that was reinforced with the steel mesh to prevent it from cracking. In structural drawing, the slab is abbreviated as r.c.s (reinforced concrete slab) and the specification for the class of concrete and the thickness of the slab are taken as the specification as according to the structural engineer. In the construction of the slab, emphasis was put on the aggregates used, type of cement, steel reinforcement, and water used to mix the concrete. The strength of concrete used was also analyzed and the method of placing and compaction of concrete to achieve a better concrete strength. 2. Body of research 2.1 Construction of footing Foundation type chosen is pad foundation (footing) Figure 2 Shows pad footing Movement of the subsoil; the movement of soil is common with the subsurface (topsoil), and this is true when the soil is saturated or shrinks on the topsoil surface. Clay soil has the tendency of moving when it is wet and shrinks when it is dry, and this movement causes failure in the foundation, as well as the structure. The volume change can also occur when the soil is waterlogged. This phenomenon was has handled using a well-compacted soil like gravel because compacted gravel has little or no movement. Constructing the foundation is loose soil need the engineer to be vigilant with pad area since for this case pad foundation was used. Increasing pad area increases the bearing area of the soil hence reducing the settlement of the foundations (footing). Tree stumps also contribute toward building foundations if it in direct contact with the roots. Much effect is on the moisture reduction or heavy especially in clay soils. Materials used are coarse aggregates and fine aggregates (sand), ordinary Portland cement, admixtures and piped water and reinforcement. All these materials were used to make concrete for the footing and steel reinforcements were used to provide tensile strength to concrete since steel is good in tension. Steel bars used were in line with the specifications of the structural engineer and conformed to the available grade in the market 2.2 Excavation The thing was to strip off the top silt soil and was done to a depth of 0.3 m to prepare a firm ground for foundation excavation. During the process of stripping all trees stumps were removed leaving only the roots that were removed during excavation. In the excavation of the foundation footing, all trees stumps and roots were removed and the disposed of from the construction site. Foundation depth for excavation ranges from 0.6 m to 1.5 m depending on the soil conditions and the loading on the structure. Foundation was excavated in reference to the specifications of the structural engineer and was excavated to the safe depth of about 1.5 m. The footing size was determined according the total loads on the building and was estimated basing the bearing capacity of the soil. A volume of excavation was determined using the architectural and the structural drawings because the quantity of excavation depends on the structural (footing) size. Foundation was put on the concrete blinding of 50 mm thick and was of grade 15 N/mm2 Pad foundation footing was used in construction. Pad foundation is suitable for the wide variety of soils except loose sand and fills soil. 2.3 Compaction Foundation structure was; hardcore put at the bottom, blending of hardcore using fine aggregates and the layer of well-compacted gravel. Compaction of foundation (gravel) was done using the foot roller since the building was small to achieve the maximum compaction limit (maximum dry density). The primary aim of compaction was to prepare the ground that is stable to accommodate the loading on the structure without failure or causing any differential settlement. Fixing the reinforcement of foundation footings and casting concrete on the footing. After placing of concrete compaction, was done using the vibrator in order to eliminate the voids in concrete that interfere with the strength of concrete. Voids create pores in the concrete, and these pores are the primary source of weakness in concrete and con not make the structure serve its purpose as intended by design. Stubs columns were cast to slightly above the damp membrane (d.p.c) level to permit construction continuation. 2.4 Construction of plinth wall After the plinth wall was built up to the level of putting the damp proof membrane and the materials used in plinth wall building was the bricks and mortar mixed of 1:3 (one part of cement to three parts of mortar) Filling under the slab; the fill materials used under the slab are gravel, fine aggregates, hardcore, and stable soil. The soil bases always are compacted in layers of about 200 mm thick to a stable density that cannot settle under the action of loadings. The hardcore used are of metamorphic rocks and crushed to the size of 200 mm, placed and compacted to uniform level then later fine aggregates was used finally as a blinder to fill up large air spaces between the hardcore. 2.5 Termite treatment To reduce the attacks due to termite on the structure, the concrete was mixed using the poly mite admixture to keep the concrete hard against termite attacks. 2.6 Treatment of the edges of reinforcement The reinforcement edges were reduced by 50 mm inside the concrete to cater for concrete cover, and this was done according to the specification of the structural engineer. All concrete cover to steel reinforcement of the footing was 50 mm as recommended by the British Standard. Reinforcement edges according BCA the reinforced concrete edges can be painted to secure it from resting the reinforcements. 2.7 Design of reinforcement Footing reinforcement design the design of the foundation is done in order to prevent failure due to loading on the structure exceeding the safe (permissible) bearing capacity of the soil. The design is also done to avoid foundation failures because of bending and shear at the base of the footing. In other words, the pressure inserted into the soil by the structure through footing should not be more the soil bearing capacity. The design was made in ultimate and serviceability limit state. Ultimate limit state handled moment, shear and loading while serviceability limit state deals with deflection and cracking. The design takes into consideration the safety and economy of the structure and its impact on the environment. In design of pad footing in reference to British Standard (BS 8110); Ultimate load for design is first calculated Plan area of the footing was calculated using the design loads Calculating the moment to be used in the design Area of reinforcement bars is then calculated Punching shear at the footing was checked if the footing was safe in punching shear 2.8 Construction of the slab The ground slab constructed was 150 mm thick. During the construction of the slab, the ground was levelled and compacted to a real dry density to avoid settlement due to loading. The slab has the series of different layers i.e. hardcore, blinding, and concrete. The formwork for the slab was erected to receive fresh concrete, lined using building line and plumbed to make it more upright and straight. Upon placing the fresh concrete, it was compacted to eliminated voids, levelled and left to set and hardened. 2.9 Design of the slab reinforcement The slab design was done primarily to prevent cracking on the concrete slab under tension. Proper sizing of reinforcements was done in order to make the slab serviceable and durable. Termite attack of the slab was prevented using poly mite admixture mixed with concrete during mixing and place together with concrete. Termite attack was handled with reference to AS 3660.1 Section 4.4 (Building Code of Australia, BCA) the edge of the slab was fixed to prevent edge movement due to loads imposed ion it. The damp proof membrane was used to prevent moisture from leaking into the slab. DPC was put on a well prepared concrete apron for it t stop moisture from encroaching into the slab. 2.10 Adverse effect of variance Variance has a negative impact on the performance of footing and slab especially when there is a time difference in their construction. Variance leads to variations in the design of the building especially area variance. Such a situation may lead to change in the building code, and regulation as other parts is denied access to the right materials In the case of foundation and slab area, the variance can make the design and implementation vary leading quality problem and as a result failure to meet the design requirement. Variance leads to accumulation of errors especially in construction like for the case of footing and slab, the degree of variability can easily lead to failure in the implementation of the structure. Conclusion The building (dwelling house) was designed according to Australian standards, and all the specifications were followed during construction the footing designed had sufficient strength to support the structural loads and transfer them safely to the ground. In the construction process, the depth of excavation was determined basing on the soil conditions at the site, and all excavations were done in reference to structural engineer’s specification. The fill materials used to backfill the footing and plinth wall was the excavated soil that was taken back as backfill of the footing and the plinth wall. The concrete used in construction was mixed using poly mite admixture to protect the structure from termites attack. Reviews of the design of reinforcement indicate that all reinforcement used corresponds to the standard specifications. The structure if completed can serve its intended design purpose provided variability is reduced. In general the builder has been following closely the standard code of practice for concrete structures (BCA) Recommendations In order to prevent dampness of the edges, strict adherence to the standard code of practice of building is highly recommended. The drainage facility in the cut bases or fill should be adequate to cater for water that may be generated from the building or may come because of rain. During concrete mixing, much emphasis should be put on the water cement ratio so that water does not undermine the concrete strength. Concrete should be properly compacted to eliminate voids that lower concrete strength and proper curing need to be done. In general strict adherence to the building code of practice is recommended for any building construction. Reference Allen, Edward, and Joseph Iano. Fundamentals of Building Construction: Materials and Methods. , 2013. Internet resource. Read More

Whenever the foundation loading is more than the maximum safe bearing capacity, the foundation can easily move down, and this can lead to structural failure. Such a condition can be solved by increasing pad size of the foundation or using pile foundation. In this report, much emphasis was put on the construction process of the dwelling house under construction where a greater discussion was made on the type of material used in construction. The properties of the soil that support the suitability of the building for it to be safely used by the dwellers Foundations are of types namely; shallow and deep foundation.

The Shallow foundation includes pad footing, strip, raft, mat foundation, etc. The Deep foundation includes pile foundation. 1.2 Slab The slab is the horizontal structural member that resists the imposed loads and dead loads and transfers them to the columns. The slab used in the construction of residential building is cast directly to the ground (foundation). The slab used in the construction of the dwelling house was reinforced concrete and has the thickness of 150 mm (solid slab) in reference to Australian standards.

In the construction of the floor slab, there are a number of thermal considerations taken i.e. insulation of the floor slab. In the construction of the building to cater for insulation, the concrete floor is cast above the insulation layers for an example of expanded polystyrene to prevent the slab from being affected by heat from underground. The slab under construction is the solid slab that was reinforced with the steel mesh to prevent it from cracking. In structural drawing, the slab is abbreviated as r.c.s (reinforced concrete slab) and the specification for the class of concrete and the thickness of the slab are taken as the specification as according to the structural engineer.

In the construction of the slab, emphasis was put on the aggregates used, type of cement, steel reinforcement, and water used to mix the concrete. The strength of concrete used was also analyzed and the method of placing and compaction of concrete to achieve a better concrete strength. 2. Body of research 2.1 Construction of footing Foundation type chosen is pad foundation (footing) Figure 2 Shows pad footing Movement of the subsoil; the movement of soil is common with the subsurface (topsoil), and this is true when the soil is saturated or shrinks on the topsoil surface.

Clay soil has the tendency of moving when it is wet and shrinks when it is dry, and this movement causes failure in the foundation, as well as the structure. The volume change can also occur when the soil is waterlogged. This phenomenon was has handled using a well-compacted soil like gravel because compacted gravel has little or no movement. Constructing the foundation is loose soil need the engineer to be vigilant with pad area since for this case pad foundation was used. Increasing pad area increases the bearing area of the soil hence reducing the settlement of the foundations (footing).

Tree stumps also contribute toward building foundations if it in direct contact with the roots. Much effect is on the moisture reduction or heavy especially in clay soils. Materials used are coarse aggregates and fine aggregates (sand), ordinary Portland cement, admixtures and piped water and reinforcement. All these materials were used to make concrete for the footing and steel reinforcements were used to provide tensile strength to concrete since steel is good in tension. Steel bars used were in line with the specifications of the structural engineer and conformed to the available grade in the market 2.

2 Excavation The thing was to strip off the top silt soil and was done to a depth of 0.3 m to prepare a firm ground for foundation excavation. During the process of stripping all trees stumps were removed leaving only the roots that were removed during excavation. In the excavation of the foundation footing, all trees stumps and roots were removed and the disposed of from the construction site.

Read More