Building Technology 3 Division 3 Concrete

The correct answer is Bait System. The objective of the system is to attract termite workers to forage on a slow-acting insect-growth regulator called hexaflumuron in order to eliminate the entire worker population and the entire colony. The system employs baits and monitoring devices installed where evidence of infestation is found. This suggests that the bait system is a method used to control termite infestations by strategically placing bait traps to attract and kill termites. The vertical and horizontal barriers mentioned are likely types of bait traps used in the system.

Concrete strengthened by having steel embedded in it is called reinforced concrete. This type of concrete is commonly used in construction due to its increased strength and durability. The steel reinforcement helps to provide additional tensile strength to the concrete, allowing it to withstand greater loads and resist cracking. Reinforced concrete is widely used in the construction of buildings, bridges, and other structures where strength and stability are crucial.

Accelerators are used to speed up the setting time and develop earlier strength in concrete, which helps to reduce the length of time needed for protection. The principal ingredient of accelerators is calcium chloride, and the maximum amount that can be added is 2 lbs. per bag of cement. However, accelerators have some disadvantages, such as increasing the expansion and contraction of concrete, reducing resistance to sulfate attack, and increasing efflorescence and corrosion of high tension steels.

An asphalt overlay is a process where one or more courses or layers of asphalt, known as an asphalt leveling course, are placed on top of an existing pavement to correct the contour of the surface. This overlay is made of an asphalt and aggregate mixture with a variable thickness. It is a commonly used method to improve the condition and smoothness of existing roads or pavements. The other options, hot mix asphalt or asphaltic concrete, and cold mix asphalt or asphaltic concrete, are types of asphalt materials used in the overlay process.

Good quality concrete is obtained through a combination of factors. Careful selection of materials ensures that the components used in the concrete are of high quality and suitable for the desired strength and durability. Correct proportioning involves accurately measuring and combining the materials in the right ratios to achieve the desired concrete mix. Thorough mixing ensures that all the components are evenly distributed, resulting in a uniform and homogenous mixture. Careful transporting and placing of the concrete ensures that it is not compromised during transportation and is properly positioned in the desired location. Finally, proper curing or protection of the concrete after it is placed allows it to gain strength and durability over time. Therefore, all of the above mentioned factors contribute to obtaining good quality concrete.

Asphaltic macadam is the correct answer because it is a type of road surface that is formed by grading and compacting layers of crushed stone or gravel, and then binding the top layer with asphalt. This process helps to stabilize the stone, provide a smoother surface, and seal against water penetration. Cold mix asphalt or asphaltic concrete and hot mix asphalt or asphaltic concrete are also types of road surfaces, but they do not specifically mention the use of crushed stone or gravel in their formation.

Termite Mesh is the correct answer because it is a steel mesh product that is fine enough to prevent even tiny termites from passing through it. It is commonly used in slab construction to create a barrier against termites and is also used to wrap pipes and other access areas to prevent termite infestation.

Fine aggregates are smaller than ¼” in size and consist of sand, stonescreenings, or other inert materials with similar characteristics. These aggregates are commonly used in construction projects to create a smooth and cohesive mixture. They help to fill the voids between larger coarse aggregates, providing stability and strength to the overall structure. Fine aggregates also improve the workability of concrete and mortar, making them easier to shape and mold. Additionally, they contribute to the durability and long-term performance of the construction materials.

Before placing concrete, several considerations must take place. The forms need to be cleaned and inspected to ensure they are in good condition and free from any debris or damage. Additionally, the surfaces need to be wetted or oiled to prevent the concrete from sticking to them. Lastly, the reinforcement needs to be properly secured to provide structural strength to the concrete. Therefore, all of the above options are correct and necessary steps to be taken before placing concrete.

Retarders are used during very hot weather to slow down the hydration of the cement. They contain principal ingredients such as zinc oxide, calcium lignosulfonate, and derivatives of adipic acid. While retarders can help in preventing the concrete from setting too quickly in hot temperatures, they may cause some loss of early strength. Therefore, careful control and more frequent slump tests are required. Additionally, retarders also reduce the expansion and contraction of concrete.

In mixing concrete, it is important for the water to be free from oil, acid, alkali, and vegetable matter. Oil can interfere with the bonding of the concrete, while acid and alkali can affect the chemical reactions and weaken the structure. Vegetable matter can introduce organic compounds that may decompose and lead to deterioration over time. Therefore, to ensure the quality and strength of the concrete, it is necessary to avoid using water contaminated with any of these substances.

Colored pigments are mainly used to give color to concrete floors. They are dusted on in two coats after all surface water has disappeared. The surface is then finished with a steel trowel. This suggests that colored pigments are the type of material used for surface coloring in concrete floors, as mentioned in the given information.

Pre-construction chemical barriers refer to the application of chemicals to the soil and foundation before construction begins. This is done to prevent termite infestations and protect the building from termite damage. These barriers act as a deterrent for termites, preventing them from accessing the structure. By treating the soil and foundation with termiticides, the risk of termite infestation is greatly reduced, ensuring the longevity and safety of the building.

The correct answer is 12. When storing cement bags in piles, it is important to limit the height to avoid any potential safety hazards or instability. By limiting the height to 12 sacks, the weight and pressure on the lower sacks can be evenly distributed, reducing the risk of collapse or damage to the bags. This ensures a stable and secure storage arrangement for the cement bags.

Chemical barriers are used to establish a continuous termiticide barrier between soil access routes and the structure. This barrier is meant to either kill or repel subterranean termites that try to reach the structure. Termiticides are a type of chemical specifically designed to control termites. Therefore, chemical barriers are an effective method for preventing termite infestations and protecting structures from termite damage.

The correct answer is Basements and Crawl Spaces. This answer is supported by the information given in the question, which mentions that chemicals may be injected into the soil in the crawl space/basement and around the foundation. This indicates that basements and crawl spaces are areas where termiticide treatment is commonly applied. Additionally, the mention of trenches being dug around the foundation suggests that termiticide may also be applied in this area, further supporting the answer choice.

Geocells are three-dimensional prefabricated polymeric systems that can range from 100mm to 200mm high. These systems are collapsed for delivery to the site and then spread open and filled to form a three-dimensional reinforced mattress. They were originally developed to quickly stabilize soft subgrades for the mobilization of large equipment. However, they are now commonly used for the protection and stabilization of steep slope surfaces and as protective linings for channels. Therefore, geocells are the correct answer in this context.

Addmixture refers to substances that are added to cements, mortars, and concrete to enhance or impart specific properties. These substances are used to improve the workability, durability, strength, or other characteristics of the material. Plasticizer is a type of addmixture that increases the plasticity or flowability of the concrete. Retarder is another type of addmixture that slows down the setting time of the concrete.

Cold mix asphalt or asphaltic concrete is the correct answer because it is prepared with a relatively light and slow-curing asphalt, placed over a prepared surface without heat. It hardens to a state that is less firm and durable than hot-mix asphaltic concrete. This type of asphalt is commonly used for temporary repairs, patching potholes, and low-volume roadways. It does not require heating during the mixing and laying process, making it more convenient and cost-effective for certain applications.

When cement is mixed with water and a fine aggregate or less than 6mm (¼“), it is known as mortar, stucco or cement plaster. Mortar is a mixture used in construction for binding bricks, stones, or other materials together. Stucco is a plastering material used for coating walls and ceilings. Cement plaster is a type of plaster made from cement, sand, and water, commonly used for finishing interior and exterior walls. All three terms refer to mixtures involving cement, water, and a fine aggregate, making them the correct answer choices.

Geosynthetics are construction materials made of synthetic components that are used with or within earth materials. They are designed to enhance the performance and durability of earth structures such as roads, slopes, and retaining walls. Geosynthetics can include materials like geotextiles, geogrids, and geomembranes, which are used to provide reinforcement, filtration, drainage, and erosion control. They are widely used in civil engineering and geotechnical applications to improve the strength and stability of soil and rock masses.

Course aggregates are larger than ¼" in size and are made up of crushed stones, gravel, or other inert materials with similar characteristics. This means that they are used for applications that require a stronger and more durable material, such as in the construction of roads, highways, and concrete structures. They provide stability and strength to the overall structure and are not easily affected by weathering or erosion. Therefore, course aggregates are the correct answer in this context.

The given answer of Class "A" 1 : 2 : 4 suggests that for slabs, beams, columns, arches, stairs, and walls of 100mm (4") thickness, the proportion of concrete should be 1 part cement, 2 parts sand, and 4 parts aggregate. This means that for every unit of cement, there should be 2 units of sand and 4 units of aggregate in the concrete mixture. This proportion is suitable for achieving the desired strength and durability of the concrete structure.

Air-entraining agents are added to concrete to introduce minute air bubbles throughout the mixture. This helps to increase the resistance of the concrete to freezing and thawing, improve plasticity, and reduce bleeding. The addition of these agents is typically done in a proportion of 3 to 6% of the volume of concrete. However, their use requires careful control and more frequent slump tests. It is important to note that while air-entraining agents offer these benefits, they may also cause some loss of strength in the concrete.

The given answer "Concrete" is the correct answer because the question is asking for the division of materials specification, and out of the options provided (Concrete, Masonry, General notes, Site works), "Concrete" is the only option that falls under the category of materials specification. The other options are either specific types of construction materials (Masonry) or general categories that may or may not include materials (General notes, Site works).

The Plasticity Index (PI) is the correct answer because it is defined as the difference between the Liquid Limit (LL) and the Plastic Limit (PL). The PI represents the range of water content over which sediment behaves. It is an important measure in geotechnical engineering as it indicates the plasticity and compressibility of soil. A higher PI value indicates a higher clay content and greater potential for settlement and deformation. Conversely, a lower PI value indicates a higher sand or silt content and less potential for deformation.

Slab treatment involves drilling through the slab floor and injecting termiticides into the soil at regular intervals. This method is commonly used in basements and crawl spaces to create vertical barriers against termites. By injecting termiticides into the soil, the treatment effectively creates a barrier that prevents termites from entering the structure through the slab. This method is considered effective in preventing termite infestations and protecting the structure from potential damage caused by termites.

Alumina cement is the correct answer because the passage states that it utilizes bauxite, the ore from which aluminum is made, as the major raw material. Additionally, it is referred to as a quick-setting cement and has the advantage of attaining a compressive strength equal to ordinary cement after only 24 hours, compared to the 28 days needed for ordinary cement. The quick hardening of alumina cement also produces heat, which is beneficial for construction in cold weather.

Division 2 in materials specification refers to Site works. This division includes all the activities and materials required for the preparation and development of the construction site. It involves tasks such as site clearing, excavation, grading, drainage, and landscaping. This division ensures that the site is properly prepared and ready for the construction process to begin.

In reinforced-concrete work or in structures exposed to the elements, Portland cement is invariably employed because of its uniform quality and the high strength which it rapidly acquires. Portland cement is a type of hydraulic cement that is widely used in construction due to its ability to harden under water and form a strong bond with other materials. It is known for its consistent quality and quick setting time, making it suitable for various applications where durability and strength are required.

Kaoline is a type of clay that is often used as an additive in various industries, including construction. It has water-repellent properties, which means it can help to make materials or surfaces more resistant to water penetration. This makes it a suitable choice for imparting water-repellent or waterproofing qualities to products such as paints, coatings, and sealants. Calcium chloride and Metali chrome, on the other hand, do not possess these water-repellent properties, making them incorrect choices for this question.

Horizontal barriers are recommended for termite treatments in slab construction because they are relatively easy to apply. These barriers involve applying one gallon of termiticide per 10 square feet, usually by coarse spray at low pressure. By creating a barrier at ground level, horizontal barriers help prevent termites from entering the structure through the slab. This method is effective in deterring termites and can be easily implemented during the construction process.

The correct answer is "slump test". The slump test is used to measure the consistency of a concrete mix by determining its fluidity. It assesses the "state of fluidity" of the mixture, ranging from the wettest to the driest possible mixtures. The slump test involves filling a slump cone with the concrete mix, compacting it, and then removing the cone to observe the slump or settlement of the concrete. This test helps ensure that the concrete mix has the desired workability and can be properly placed and compacted.

Mass concrete refers to concrete that is used in large structural elements where the heat generated during curing can cause thermal cracking. It is typically used in dams, bridges, and other massive structures. Unlike reinforced concrete, which contains steel reinforcement to provide tensile strength, mass concrete relies solely on its own compressive strength to withstand loads. Therefore, the correct answer is mass concrete.

The delivery from the mixer to the forms should be fairly continuous and uninterrupted. This means that there should not be any significant breaks or pauses in the delivery process. The maximum time allowed for the delivery should not exceed 30 minutes. This ensures that the concrete remains in a workable state and does not start to set before it is poured into the forms. Any delays beyond this time limit may result in poor quality concrete and compromised structural integrity.

Termite Resistant Sand is the correct answer because it forms a layer of sand with uniform-sized particles that acts as a barrier against termites. The sand particles are large enough to prevent termites from moving through it or using it for tunnel construction. This sand acts as a deterrent and helps protect against termite infestation.

Geotextiles are the most common type of geosynthetics, which are materials used in civil engineering projects to improve soil stability and prevent erosion. Geotextiles are typically made from polyester or polypropylene and can be either woven or nonwoven fabric. They are used for various applications such as filtration, drainage, separation, and reinforcement. Geocomposites and geomembranes are also types of geosynthetics, but they are not as commonly used as geotextiles.

The liquid limit (LL) is the moisture content at which a soil transitions from a liquid state to a plastic state. This transition is measured by determining the point at which soil in a shallow dish flows to close a 12.5 mm groove after 25 drops from 1 cm. The liquid limit is an important property of soil that helps determine its behavior and engineering characteristics.

Concrete is a mixture of cement, aggregates, and water that, when properly proportioned, forms a plastic mass. This plastic mass can be cast or molded into a predetermined size or shape. Cement is the binding agent that holds the mixture together, while aggregates provide strength and stability. Water is added to the mixture to initiate the chemical reaction that causes the cement to harden and form a solid structure. Therefore, the correct answer is concrete.

The Atterberg limits are a set of tests used to determine the consistency and plasticity of soils. These tests include the Plastic Limit (PL) and Liquid Limit (LL), which are used to calculate the Plasticity Index (PI). The Plastic Limit (PL) is the moisture content at which a soil transitions from a plastic to a semi-solid state, while the Liquid Limit (LL) is the moisture content at which a soil transitions from a liquid to a plastic state. These tests are important in assessing the behavior and suitability of soils for various engineering applications.

The correct answer is "HOT MIX ASPHALT or ASPHALTIC CONCRETE" because it accurately describes the dark brown to black cementitious material made from bitumens obtained in petroleum refining. This material is mixed with graded aggregates and used for paving by placing, shaping, and compacting while hot over a prepared base.

When a large aggregate of more than 6mm (¼”) in size is added to cement, water, and fine aggregate, the resulting product is concrete. Concrete is a composite material made up of cement, water, and aggregates such as sand, gravel, or crushed stone. The addition of large aggregates gives concrete its strength and durability, making it suitable for various construction applications. Mortar, stucco, and cement plaster are also made with cement and water but do not contain large aggregates like concrete. Clay and grouts are different materials altogether and do not fit the given description.

Beach sand or lahar should be prohibited from being used in making concrete. This is likely because beach sand may contain salt, which can cause corrosion and weaken the concrete structure over time. Similarly, lahar, which is volcanic mudflow, may contain excessive amounts of silt and clay particles, affecting the strength and durability of the concrete. Therefore, it is recommended to avoid using these materials in concrete production to ensure the quality and longevity of the concrete.

Aggregates are the correct answer because they fulfill all the requirements mentioned in the question. They are durable, strong, clean, hard, and uncoated. They are also free from dust, lumps, soft and flaky particles, shale, alkali, organic matter, loam, or any other harmful substances. Aggregates are commonly used in concrete to provide strength and stability to the mixture.

Geomembranes are continuous polymeric sheets that are impermeable, making them suitable for applications such as ground lining and pond lining. They are commonly made from thermoplastic materials like HDPE and PVC. Geomembranes are different from geotextiles and geocomposites, which serve different purposes in geotechnical engineering.

Pozzolanic cement is a type of cement that is made by combining lime mortar with a pozzolanic material, such as volcanic ash, granulated slag, or pumice. These materials contain active silica, which reacts with lime to form cementitious compounds. Pozzolanic cement is commonly used in masonry applications due to its ability to improve workability and durability of mortar. It is different from other types of cement like masonry cements, alumina cements, and natural cements, which have different compositions and properties.

Geonets are a type of drainage material that consist of a continuous extrusion of polymeric ribs. These ribs create void spaces that allow for in-plane flow capacity. Geonets can be used with or without bonded geotextile filters. When geonets are combined with geotextile filters, they are referred to as composite drainage nets (CDNs). Geonets are commonly used in various applications such as drainage systems, landfill liners, and erosion control.

White cement is the correct answer because it is free of iron impurities that can stain porous marbles, granites, limestone, and other light-colored stones. This type of cement is commonly used in applications where aesthetics and color consistency are important, such as in architectural designs or decorative elements. Unlike brown, grey, or aluminum cement, white cement provides a clean and uniform appearance, making it suitable for projects that require a lighter color palette.

Geocomposites are a combination of geosynthetic components that consist of a prefabricated core bonded with a geotextile filter. The core allows water to flow through it, while the geotextile filter prevents soil from filling the voids created by the core. This combination of components makes geocomposites effective in drainage applications, as they allow water to pass through while keeping the soil in place. Geomembranes and geotextiles, on the other hand, do not have the same combination of components and characteristics as geocomposites.

Waterproofing compounds are used in concrete or mortar to reduce the capillary attraction of voids and decrease water absorption. However, they do not make the concrete or mortar completely waterproof. These compounds are typically manufactured from stearic acid orts compounds, such as calcium steareate, and can include asphalt emulsions. They are added in small amounts, usually ranging from 0.1 to 4.0% of the weight of cement, to provide some level of water resistance to the concrete or mortar.