Spreadsheet for Concrete Tunnel Design and Calculations According to AASHTO and ACI Standards
In the realm of civil engineering, designing concrete tunnels involves intricate calculations and adherence to stringent standards. To streamline this complex process, we are excited to introduce a powerful and user-friendly spreadsheet designed for concrete tunnel design and calculations in compliance with AASHTO (American Association of State Highway and Transportation Officials) and ACI (American Concrete Institute) standards.
Why a Concrete Tunnel Design Spreadsheet?
Concrete tunnel design is a multifaceted task that requires meticulous attention to detail. Engineers must consider various factors such as load-bearing capacity, structural integrity, safety measures, and compliance with regulatory standards. Traditional methods of manual calculations can be time-consuming and prone to errors. Our spreadsheet solution addresses these challenges by providing an automated, reliable, and efficient tool that simplifies the design process while ensuring accuracy and compliance.
Key Features of the Spreadsheet
Compliance with AASHTO and ACI Standards
The spreadsheet is built to adhere to the latest guidelines and specifications set forth by AASHTO and ACI. This ensures that your tunnel designs meet the required safety and performance standards, providing peace of mind and regulatory compliance.
User-Friendly Interface
Designed with engineers in mind, the spreadsheet features an intuitive interface that allows for easy data entry and navigation. Even those with limited experience in tunnel design can quickly get up to speed and produce reliable results.
Comprehensive Design Calculations
The spreadsheet performs a wide range of calculations necessary for concrete tunnel design, including:
Load analysis: Evaluating the effects of various loads, such as live loads, dead loads, and environmental loads.
Structural analysis: Determining the stress distribution, bending moments, and shear forces within the tunnel structure.
Reinforcement design: Calculating the required reinforcement for both longitudinal and transverse directions.
Stability checks: Assessing the overall stability of the tunnel structure under different loading conditions.
Automated Reporting
Generate detailed reports that outline the design assumptions, calculation results, and compliance checks. These reports can be easily shared with stakeholders and regulatory bodies, facilitating transparent communication and documentation.
Customizable Templates
The spreadsheet comes with customizable templates that allow engineers to tailor the design parameters to specific project requirements. Whether you are working on a highway tunnel, a railway tunnel, or an underground passageway, the templates can be adjusted to fit your needs.
Real-Time Error Checking
Built-in error-checking mechanisms alert users to potential issues and inconsistencies in their input data. This proactive feature helps to identify and correct errors early in the design process, saving time and reducing the risk of costly mistakes.
The Best Collection Of Civil Engineering Spreadsheets
Civil engineering spreadsheets are powerful tools that can greatly enhance the efficiency, accuracy, and productivity of engineers. Here are several ways in which these spreadsheets can be useful:
1. Design and Analysis
Structural Calculations: Spreadsheets can be used to perform complex structural calculations such as load analysis, bending moments, shear force, and deflection. Pre-built templates and formulas can simplify these processes.
Geotechnical Analysis: They help in analyzing soil properties, bearing capacity, and slope stability, allowing for accurate foundation design.
Hydraulic and Hydrology: Spreadsheets can model water flow in rivers, design stormwater management systems, and calculate flood risks.
2. Project Management
Scheduling: Tools like Gantt charts can be created to manage project timelines, track progress, and allocate resources efficiently.
Cost Estimation: Spreadsheets can provide detailed cost breakdowns, material take-offs, and budget tracking to ensure projects stay within financial limits.
Resource Allocation: They help in managing labor, equipment, and material schedules, ensuring optimal use of resources.
3. Data Analysis and Visualization
Data Management: Spreadsheets allow for the storage, organization, and analysis of large datasets. Engineers can use them to process data from surveys, site investigations, and sensor readings.
Graphical Representation: Data can be easily visualized using charts, graphs, and tables, aiding in the interpretation and presentation of results.
4. Documentation and Reporting
Report Generation: Standardized templates can be used to generate consistent and professional reports for clients, stakeholders, and regulatory bodies.
Compliance and QA/QC: Spreadsheets can help track compliance with standards and regulations, and manage quality assurance/quality control processes.
5. Optimization and Simulation
Design Optimization: Engineers can run multiple scenarios and optimize designs for cost, performance, and sustainability using iterative calculations.
Simulation Models: Spreadsheets can simulate real-world behaviors such as traffic flow, material strength under various conditions, and environmental impact assessments.
6. Standardization and Reusability
Templates and Libraries: Pre-designed templates and libraries of formulas and macros can standardize calculations and procedures, ensuring consistency across projects.
Custom Tools: Engineers can create custom tools and scripts within spreadsheets to automate repetitive tasks and complex calculations, saving time and reducing errors.
Pavement design, traffic flow analysis, intersection design, and route optimization.
Water Resources Engineering:
Pipe network design, open channel flow calculations, stormwater drainage design, and water balance calculations.
Environmental Engineering:
Contaminant transport modeling, environmental impact assessment, air quality analysis, and waste management planning.
Benefits of Using Spreadsheets
Accuracy: Reduces the risk of human error in complex calculations.
Efficiency: Automates repetitive tasks and speeds up the design process.
Flexibility: Easily adaptable to different types of projects and design requirements.
Accessibility: Spreadsheets are widely used and accessible, with many engineers already familiar with their operation.
Collaboration: Facilitates collaboration among team members through shared files and collaborative platforms.
Civil engineering spreadsheets are invaluable for streamlining workflows, enhancing precision, and facilitating better decision-making in various aspects of engineering projects. By leveraging the capabilities of spreadsheets, engineers can improve productivity and achieve more reliable outcomes in their work.
Bio-concrete, also known as self-healing concrete, is an innovative material designed to repair its own cracks and damages autonomously, extending the lifespan of concrete structures. The primary mechanism behind bio-concrete involves the incorporation of bacteria and nutrients within the concrete mix. These bacteria, when activated by the presence of water entering through cracks, produce limestone (calcium carbonate), which fills and seals the cracks.
How Bio-Concrete Works
Bacteria Incorporation: Specific types of bacteria (e.g., Bacillus species) are added to the concrete mix. These bacteria can survive in the harsh environment of concrete by forming spores that remain dormant until activated.
Nutrient Addition: A nutrient source, usually a form of calcium lactate, is mixed into the concrete. This serves as food for the bacteria when they become active.
Activation and Healing Process:
When cracks form and water penetrates the concrete, the dormant bacterial spores are activated.
The bacteria consume the calcium lactate and convert it into calcium carbonate (limestone).
The produced limestone fills the cracks and hardens, effectively sealing the gaps and preventing further ingress of water or harmful substances.
Applications of Bio-Concrete
Infrastructure: Used in the construction and maintenance of bridges, highways, tunnels, and other critical infrastructure where durability and longevity are paramount.
Buildings: Applied in residential, commercial, and industrial buildings to enhance the lifespan of structural components such as walls, floors, and foundations.
Marine Structures: Ideal for structures exposed to water and harsh marine environments, such as piers, docks, and seawalls, where it helps to combat the detrimental effects of constant moisture and salt.
Historical Preservation: Used in the restoration and preservation of historical buildings and monuments, where maintaining the original structure without frequent repairs is essential.
Advantages of Bio-Concrete
Extended Lifespan: Reduces the need for frequent repairs and maintenance, thereby extending the lifespan of concrete structures.
Cost-Effective: Although initially more expensive, the reduction in repair and maintenance costs over time can make bio-concrete a cost-effective solution.
Environmental Benefits: Decreases the environmental impact associated with concrete production and repairs by reducing the need for new concrete and repair materials.
Improved Durability: Enhances the overall durability and resilience of concrete structures, making them more resistant to cracking and damage.
Implementation in Construction
Mix Design: Bio-concrete requires a specialized mix design incorporating the bacterial spores and nutrients. The mix must ensure that these components remain viable until activation.
Quality Control: Careful quality control is necessary during the mixing and pouring processes to ensure the bacteria and nutrients are evenly distributed and remain effective.
Standard Construction Methods: Bio-concrete can be used with standard construction methods, making it easy to integrate into existing building practices without the need for specialized equipment or techniques.
Bio-concrete represents a significant advancement in construction materials, offering a smart solution to one of the most persistent problems in concrete structures: cracking and deterioration. By leveraging biological processes, bio-concrete not only enhances structural integrity but also promotes sustainability in the construction industry.
What is Pumped Concrete? Advantages of Pumped Concrete
What is Pumped Concrete:
The method in which the fresh concrete is pumped to the area where the concreting work to be done is called as pumped concrete. For small work, concreting can manually be done, but for large scale work, concreting is efficiently done by pumping.
Concrete pumps are generally mounted on a truck or on a trailer. Pumps can be operated by electric power or diesel. Pipeline pumping system has a diameter between 100mm to 180mm. Diameter size of 125mm is must probably adopted for pumping the concrete.
Modern and advanced handy or portable concrete pumps have more power, high capacity and absolutely reliable hydraulic system and these pumps can take the fresh concrete to a height near about 600 m and also can take the concrete in horizontal distance near about 200 m.
Pumps have fully hydraulic, compact and dirt resistance control system. Hydraulic pump is output regulated and hence require less power utilization at an ideal speed and pressure.
Taper and a clamping device is provided to the outlet portion of the pump so as to connect the pipeline. The outlet portion is easy to clean and also has a simple side swing. The agitator maintains the concrete in an agitated form in between two batches of concrete fed into the hopper.
The concrete pump unit is mounted one the chassis of a tuck and drive of the hydraulic pump is driven from the engine of truck directly. Water pump is joined to the water tank and it is driven hydraulically.
The pump capacity is in m3/hr and it depends on a distance of pumping the concrete, diameter of delivery line and the maximum line pressure.
Concrete pumping capacity depends upon the following factors:
Horizontal pipe length through which concrete can be pumped.
Vertical pipe length through which concrete can be pumped.
Number of bends in pipe line.
Diameter of delivery pipe line.
Length of flexible hose pipe.
Number of reducers in the pipe line.
Workability of concrete and its cohesiveness.
Type and size of aggregates used in the concrete.
Proportion of ingradients in the concrete.
Advantages of Pumped Concrete:
Following are the advantages of pumping the concrete for casting the various member of the structures:
Concrete can be moved horizontally as well as vertically at a time
It provides a good quality control.
Concreting by pumping is the most effective and sensitive method because any variation in concrete mix can be easily rectified at the pumping point by observing the pumping pressures and hence there is a proper control on consistency and workability of concrete.
It refuses to handle any concrete which is unduly harsh, non-cohesive, inadequately mixed, improper consistency.
No wastage of concrete if casting work done by pumping, but there is more wastage of concrete if casting work is done manually.
Pumped concrete has high workability and good cohesion which provides good finish and ultimate strength.
By pumping system, concrete can be placed in inaccessible areas.
Mass concreting work can be carried out in a limited time with high speed without cold joints.
For high rise building, pumped concrete method is best suitable, economical and faster.
Pipeline for delivery of the concrete require a very less space and can be easily extended to the desired height and can be easily removed.
The total unit of pumped concrete helps to complete the contacts within the prescribed time given in agreement. It also reduces the site-overheads.
What is Self-Leveling Concrete? Properties, Advantages and Disadvantages
1. Introduction
Self-leveling concrete is a polymer-modified high-performance concrete that has the ability to flow, compact, and provide a leveled surface when poured over an area. Self-leveling concrete does not require vibration as required for normal concrete.
It is poured in liquid form and goes down 1/4 to 1.5 inch thick in single pass. A gauging tool is used to spread it in place. Qualities include smoothness, flatness and a compressive strength over that of traditional concrete floors. After you apply it, you can add decorative overlays or concrete stains or dyes.
Self-leveling overlays are among the newest trends for architects and commercial property owners. It is quick to install and can be installed pre or post construction. It can cover plywood or tile floors as well, and is flood proof and hypoallergenic.
2. Properties of Self-Leveling Concrete (SLC)
Low Plastic Viscosity.
High Flow-ability.
Low segregation.
Low Bleeding.
Stability.
a- Low Plastic Viscosity
The low plastic property of SLC increases the flow ability properties which imparts the self-leveling property. The balance and proportion of the above-mentioned properties in mix design help to design the desired SLC concrete.
b- High Flow-ability
Providing low viscosity of the concrete mix can result in stability issues. This can result in high segregation and bleeding problems. This low viscosity or high flow-ability is introduced by the addition of super plasticizes or polymer agents that maintain stability without affecting the flow-ability characteristics.
c- Stability
High-homogeneity is received by self-leveling concrete with its self-leveling property. The flow-ability properties of SLC are greater as compared with (SCC) self-compacting concrete. This increase in flow-ability is one reason to obtain good finish in final hardened SLC
d- Low segregation / Low Bleeding
The viscosity agents added prevents the settling down of aggregates that cause segregation and keep the cohesiveness of the mix within the bond which in turn helps in avoiding bleeding. Maintain the viscosity throughout the layer without letting the aggregates to settle at the bottom.
3. Advantages of Self-Leveling Concrete (SLC)
Labor required less.
Leveled and smooth surface.
Water Resistant surface.
SLC concrete gives a flat and smooth surface.
The best choice of heavily reinforced concrete construction.
The hardening of concrete is taking place in a homogeneous way.
The best option where form-work is arranged in unusual geometry.
Compressive strength is higher as compared to traditional concrete.
Self-leveling concrete gives cohesive concrete that resits bleeding and segregation issues.
Easy to use. Self-leveling concrete also levels the playing field. Now subfloor leveling is a DIY project.
Two options to choose. Acrylic-based concrete is more giving, has a slight flex and sturdiness. Water-based concrete dries fast and is harder than standard concrete.
Radiant heat capable. Most self-leveling concrete brands and styles are rated for using over around or under radiant floor heating systems.
Quick acting. The formula that makes up the concrete compound is strong, durable and fast acting. It can set up in as little as 10 minutes and be ready for most flooring types in just a few hours.
Hypoallergenic. Unlike standard concrete which has been known to cause work-induced asthma, self-leveling concrete doesn’t contain those chemicals and minerals.
Mold and mildew resistant. Even when installed in wet areas, self-leveling concrete is more resistant to mold and mildew growth than standard concrete.
4. Disadvantages of Self-Leveling Concrete (SLC)
Fast acting. Yes, this is also a pro item, but it dries fast. You shouldn’t mix until you are ready to pour, and when you pour you shouldn’t stop. Finding the right balance can be difficult.
Doesn’t repair subfloors. If there is damage, cracks, joints or weak spots in your subfloor, self-leveling concrete will not fix or patch them. If the spot worsens, it will disrupt the self-leveling concrete and the floor above it, too.
Difficult to remove. If you splash, get it on your clothing, tools or other surfaces and it is allowed to dry, you will have a difficult time getting it off. Any spills or splashes need to be cleaned up quickly.
Mixing is hard. You need to be precise in your measurements and you don’t get to make mistakes. If you add too much water or not enough, it will affect how the concrete pours and how viscous it becomes.
Column Load Take Down And Design For symmetrically Reinforced Rectangular Concrete Spreadsheet
COLUMN LOAD TAKE DOWN & DESIGN FOR SYMMETRICALLY REINFORCED RECT. COLUMNS BENT ABOUT TWO AXES TO BS 8110:1997
An engineer needs to carry this calculation out for every column and every floor, summing the results at the end to arrive at a cumulative load for a given column at the foundation.
Self-compacting concrete (SCC) – Advantages, Disadvantages and Applications
Introduction
Self-compacting concrete (SCC) is a concrete which flows under its own weight and doesn’t require any external vibration for compaction, it has revolutionized concrete placement.
Such concrete should have relatively low yield value to ensure high flow ability, a moderate viscosity to resists segregation and bleeding and must maintain its homogeneity during transportation, placing and curing to ensure adequate structural performance and long termdurability.
Self-compacting concrete (SCC) can be defined as a fresh concrete which possesses superior flow ability under maintained stability (i.e. no segregation) thus allowing self-compaction that is, material consolidation without addition of energy.
It is a fluid mixture suitable for placing in structures with Congested reinforcement without vibration and it helps in achieving higher quality of surface finishes.
The three properties that characterise a concrete as self-compacting Concrete are :
Flowing ability: the ability to completely fill all areas and corners of the formwork into which itis placed
Passing ability: the ability to pass through congested reinforcement withoutseparation of the constituents or blocking
Resistance to segregation: the ability to retain the coarse components of the mixin suspension in order to maintain a homogeneous
Applications of Self-Compacting Concrete
The main applications of this type of concrete are the following:
Construction of raft and pile foundations
Retrofitting and repairing constructions
Structures with complex reinforcement distributions
Construction of earth retaining systems
Drilled shafts
Columns
Advantages of (SCC) Self Compacting Concrete
Self-compacting concrete comes with several advantages compared with regular concrete. Some of these benefits include:
Reduces labor costs.
Improved constructability.
High durability, strength, and reliability.
Minimizes voids in highly-reinforced areas.
Reduces permeability in concrete structures.
Fast placement without mechanical consolidation.
The SCC construction is faster than normal concrete.
SCC enables freedom in designing concrete structures
Creates smoother and more aesthetic surface finishes.
Eliminates problems associated with concrete vibration.
Creates high-quality structures with improved structural integrity.
Allows for easier pumping, and there are many placement techniques available.
Allows for innovative architectural features, since it can be used in complex forms.
Reduced noise during placement as no vibration is required
SCC requires a lower pumping pressure. Hence, concrete can be easily pumpedover longer distances and heights compared to traditional concrete
Disadvantages of (SCC) Self Compacting Concrete
As with any construction material, self-compacting concrete faces the following limitations:
Material selection is more strict.
Construction costs are much more higher, compared with regular concrete.
Higher precision is required when measuring and monitoring.
There is no globally accepted test standard to undergo an SCC mix design.
The cost of construction is costlier than conventional concrete construction.
Many trial batches and laboratory tests are required to use a designed mixture.
There is no internationally accepted test standard for self-compacting concrete mix.
The higher flow rate of SCC compared to traditional concrete can cause adynamic pressure, in addition to the hydrostatic pressure of placed concrete, and thismust be taken into consideration for formwork design
Material Use In (SCC) Self Compacting Concrete
Cement :
Ordinary Portland Cement, 43 or 53 grade can be used
Aggregates :
The maximum size of aggregate is generally limited to 20 mm. An aggregate of size 10 to 12mm is desirable for structures having congested reinforcement.
Wherever possible size of aggregate higher than 20mm could also be used. Well graded cubical or rounded aggregates are desirable.
Aggregates should be of uniform quality with respect to shape and grading. Fine aggregates can be natural or manufactured.
The grading must be uniform throughout the work. The moisture content or absorption characteristics must be closely monitored as the quality of SCC will be sensitive to such changes.
Particles smaller than 0.125 mm i.e. 125-micron size are considered as FINES which contribute to the powder content
Mixing Water :
Water quality must be established on the same line as that for using reinforced concrete or prestressed concrete.
Chemical Admixtures :
Super plaseizers are an essential component of SCC providing necessary workability. The new generation super plasticizers termed poly-carboxylated ethers (PCE) is particularly useful for SCC.
Other types may be considered as necessary, such as Viscosity Modifying Agents (VMA) for stability, air-entraining agents (AEA) to improve freeze-thaw resistance, and retarders for Control of Setting.
Mineral Admixtures:
This may vary according to the mix design and the properties required. Below is a list of the different mineral admixtures used, and the properties they provide to the concrete mixture:
Fly ash: Used to improve the filling of the internal concrete matrix, resulting in fewer pores. This reduces permeability and improves the quality of structures.
Ground granulated blast furnace slag (GGBS): GGBS helps improve the rheological properties of concrete.
Stone Powder: Incorporated to improve the powder content of the mixture.
Silica Fumes: Used to improve the mechanical properties of the structure.
Transport, pumping, placing and finishing
Transport
Self-compacting concrete has higher fluidity compared to traditional concrete. Hence,there is a higher chance of spillage during transport. Additional caution is advised by reducing the batch size on the back of a truck, as well as ensuring the water-tightnessof the drum.
Extreme weather conditions (very high or low temperature) can affect the self-compacting properties of concrete. Under such conditions, the transport duration must be minimized by choosing non-peak hours in congested areas and also by choo-ing the closest concrete production plant to the placement site.
Overall, the averagetime that an SCC mixture can spend on the back of a truck before placement needs to be considered and the mixture design needs to be optimized accordingly. Otherwise,flowability properties might not be achieved.
Pumping, placing and formwork
An advantage of SCC is its excellent flow properties, which results in easier pumping and placing of SCC compared to traditional concrete. After discharging, self-compacting concrete can flow up to 10m in horizontal directions.
The excellent flowability of SCC also results in a much higher filling capability compared to traditional concrete, i.e. it can quickly fill inaccessible voids between reinforcements and formwork.
The placement rate of SCC can occur over ashort amount of time. Therefore, it is essential that all formwork, linings, reinforcing steel and any other embedded objects are secured and tightened before placement.
SCC can be placed with chutes, buckets and pumps. Pumping is the most common method of SCC placement because of excellent flowability without segregation.
Pumping of SCC from a truck using a crane pump at a building site
Surface finish of SCC
SCC is generally used for architectural concrete because the surface finish of SCC is of high quality, often more appealing with sharp edges compared to traditional concrete. The improved surface finish is attributed to the self-levelling and filling capabilities of SCC, which allows concrete to flow smoothly, and thereby fill holes.
The surface finish of traditional concrete often has discolouration because of hydrationby-products and segregation.
Other imperfections such as sand textured areas, honeycombing (aggregate bridging), and some problems caused by mortar loss canal so occur. Using SCC can increase the chance of eliminating these surface imperfections. However, a well-balanced concrete mixture with optimized rheological properties is required to achieve a high-quality surface finish for SCC, i.e. aesthetic appeal for exposed architectural use.
Mixtures with a lower viscosity, i.e. higher slump flow allow for entrained air to escape more efficiently and thereby provide a better surface finish.
The quality of formwork surfaces, type and amount of releasing agent, as well as production and placement methods also affect the surface finish of SCC.
What is Polymer Concrete? Advantages and disadvantages – Applications
Introduction
Polymer concrete is the composite material made by fully replacing the cement hydrate binders of conventional cement concrete with polymer binders or liquid resins, and is a kind of concrete-polymer composite.
For hardening of polymer concrete, most liquid resins such as thermosetting resins, methacrylic resins and tar-modified resins are polymerized at ambient or room temperature. The binder phase for polymer concrete consists only of polymers, and does not contain any cement hydrates. The aggregates are strongly bound to each other by polymeric binders.
The different ways in which the polymer is introduced into the concrete (hardened concrete) will vary widely based on the commercial objective. The polymers can be employed in concrete in different ways.
They are:
Polymer Impregnated Concrete (PIC)
Polymer-Modified Concrete (PMC)
Polymer Concrete (PC)
Polymer as Protective Coating
Polymer as Bonding Agent
Advantages and disadvantages:
The advantages and disadvantages of polymeric binders are directly given to the polymer concrete. Accordingly, in comparison with ordinary cement concrete, its properties such as strength, adhesion, watertightness, chemical resistance, freeze-thaw durability and abrasion resistance are generally improved to a great extent by polymer replacement. Since the bond between polymeric binders and aggregates is very strong, its strength properties depend on those of the aggregates.
On the other hand, its poor thermal and fi re resistance and its large temperature dependence of mechanical properties are disadvantages due to the undesirable properties of the polymer matrix phases. Therefore, the glass transition point (or temperature) of the polymer matrix phases should be noted from the viewpoint of such thermal properties.
Thermoplastic resins generally retain their practical properties at temperatures below the glass transition point and lose them at temperatures exceeding the point, beginning to thermally decompose at somewhat higher temperatures.
The practical temperature range of the thermoplastic resins may be improved by the addition of suitable cross-linking monomers or comonomers having higher glass transition points.
Thermosetting resins do not commonly show a glass transition point, and retain their mechanical properties up to the thermal decomposition temperature. Such essential disadvantages of the polymer concrete can be considerably improved by controlling the necessary polymeric binder content by volume to a minimum.
Practical applications
Structural precast products:
Manholes and handholes for telecommunication cable lines,
electric power cable lines and gas pipelines,
prefabricated cellars or stockrooms,
tunnel liner segments for telecommunication cable lines and sewerage,
pipes for sewage,
hot spring water and seawater,
piles for port or hot spring construction,
FRP-reinforced frames or panels for buildings,
machine tool structures, e.g.
beds and saddles, etc.
Non structural precast products :
Gutter covers,
U-shaped gutters,
footpath panels,
permanent forms for checkdams with acidic water and offshore or marine structures,
terrazzo tiles and panels, and large-sized or curved decorative panels for buildings,
partition wall panels, sinks, counters, washstands, bathtubs, septic tanks, electrolytic tanks, works of art, e.g. carved statues and objets d’art, tombs for Buddhists, etc.
Cast-in-place applications :
Spillway coverings in dams,
protective linings of stilling basins in hydroelectric power stations,
coverings of checkdams,
foundations of buildings in hot spring areas,
acid-proof linings for erosion control dams with acidic water,
patch materials for damaged concrete structures,
overlays for pavement repairs,
overlay strengthening for bridge decks,
drainage pavements using porous polymer concrete, etc.
Precast applications :
Transportation applications such as railroad crossings,
railroad ties, median barriers, etc.
Structural and building panels
Sewer pipes, equipment vaults, drainage channels, etc.
Corrosion-resistant tiles, bricks and linings
Small water-flow control structures
Stair treads and nosings
Non conductive, non magnetic support structures for electrical equipment
Manhole structures and shims
Components for the animal-feeding industry
Large-scale pre-insulated wall panels for segmental building construction
Electrical insulators
Machine tool bases
Cast-in-place applications :
Patching materials for reinforced concrete structures
Overlays for reinforced concrete structures in the transportation industry
Segregation and Bleeding of concrete – Causes and Mitigation
1. Segregation of Concrete:
Segregation is the separation of constituent materials in concrete. There are three common types of segregation:
Separation of coarse aggregate from the concrete mixture
Separation of cement paste from the concrete during its plastic stage
Separation of water from the concrete mix (Bleeding in concrete)
Segregation of concrete affects strength and durability in structures. When this is detected, elements affected should be demolished.
The segregation includes undesirable properties in the hardened concrete; therefore, it can cause honeycombing and may leads to the development of cavities in the concrete surface.
a – Causes of concrete segregation:
The main causes are:
Use of high water-cement ratio in concrete. This general happens in case of concrete mixed at site by unskilled workers
Excessive vibration of concrete with mechanical needle vibrators makes heavier particles settle at bottom and lighter cement sand paste comes on top.
When concreting is done from height in case of underground foundations and rafts, which causes concrete to segregate.
b – Mitigation:
Segregation can be controlled by maintaining proper proportioning the mix.
By peculiar handling, placing, transporting, compacting and finishing of concrete.
Adding air entraining agents, admixtures and pozzolanic materials in the mix segregation controlled to some extent.
Wherever depth of concreting is more than 1.5 meters, it should be placed through temporary inclined chutes.
The delivery end of chute should be as close as possible to the point of deposit.
Handling, placing and compaction of freshly mixed concrete should be done carefully. A proper vibration also reduces the chances of segregation.
2. Concrete Bleeding:
Bleeding is a form of segregation in which water present in the concrete mix is pushed upwards due to the settlement of cement and aggregate. The specific gravity of water is low, due to this water tends to move upwards.
Some bleeding is normal but excessive bleeding can be problematic.
Not all bleed water will reach the surface of the concrete but some water may rise and remain trapped under aggregates and reinforcing. This results in the weakening of the bond between the paste and those elements.
a – Bleeding Causes:
The principal causes of bleeding are:
High water-cement ratio to highly wet mix
Badly proportioned and insufficiently mixed concrete
b – Bleeding Effects:
Due to the formation of Laitance, structures may lose its wearing capacity and decreases its life.
Water while moving from bottom to the top, forms continuous channels. Due to these channels, concrete becomes permeable and allow water to move, which forms water voids in the matrix and reduces the bond between aggregate and the cement paste.
Forming of water at the top surface of concrete results in delaying the surface finishing and so concrete becomes permeable and loses its homogeneity.
Excessive bleeding breaks the bond between the reinforcement and concrete.
The word plum means large stones which are termed as boulders or coarse aggregates if technically speaking.
The use of plum concrete is preferred if the required thickness of PCC is excessive or large. This is mainly done below the foundations where due to sleep slope of the strata, the quantity of leveling course could be excessive.
The plum concrete is actually an economical variation of mass concrete.
Plumbs above 160 mm and up to any reasonable size may be used in plain concrete work up to a maximum limit of 20 percent by volume of concrete when specifically permitted by the engineer-in-charge. The plums shall be distributed evenly and shall be not closer than 150 mm from the surface.
Uses of plum concrete:
Plum concrete is used at the water channel beds. It is used mostly in mass concrete works like concrete gravity dams or bridge piers in such cases of rocks about 150 mm in size are used as coarse aggregates to mix a plum concrete.
It is used at side slopes of the embankment to provide a protective laver to earthen foundations and bases.
