Civil Technology

10/05/2025

Sieve Analysis of Soil

Introduction

Sieve analysis is one of the most important tests in soil mechanics and highway engineering.
It is performed to determine the particle size distribution (gradation) of a soil sample.

👉 Why we do it:

To classify soil as gravel, sand, silt, or clay.

To know whether the soil is well-graded (good range of particle sizes) or poorly graded (uniform or gap-graded).

To determine the coefficients of uniformity () and curvature (), which help in soil classification under USCS (Unified Soil Classification System) or AASHTO.

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Step 1: Data from Sieve Analysis

From your test (total weight = 6977.0 g):

| Sieve | Size (mm) | Mass Retained (g) | % Retained (%) | % CUM Retained (%) | % Passing (%) |
|-----------|-----------|-------------------|----------------|--------------------|---------------|
| 2" | 50.00 | 1034.6 | 14.8 | 14.8 | 85.2 |
| 1 1/2" | 37.50 | 152.2 | 2.2 | 17.0 | 83.0 |
| 3/4" | 19.00 | 922.3 | 13.2 | 30.2 | 69.8 |
| 3/8" | 9.50 | 898.7 | 12.9 | 43.1 | 56.9 |
| No.4 | 4.75 | 862.2 | 12.4 | 55.5 | 44.5 |
| No.8 | 2.36 | 735.4 | 10.5 | 66.0 | 34.0 |
| No.40 | 0.425 | 1329.6 | 19.1 | 85.1 | 14.9 |
| No.200 | 0.075 | 601.8 | 8.6 | 93.7 | 6.3 |

% Retained = (Mass Retained ÷ Total Weight) × 100

% Passing = 100 − % Cumulative Retained

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Step 2: Read Key Particle Sizes from the Grain Size Distribution Curve

From the curve:

→ size at 10% passing

→ size at 30% passing

→ size at 60% passing
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Step 3: Calculate and

Formula 1:

C_u = \frac{D_{60}}{D_{10}}

Cu = D60 ÷ D10
Cu = 11.50 ÷ 0.18
Cu = 63.89 _

Formula 2:

C_c = \frac{(D_{30})^2}{D_{60} \times D_{10}}

Cc = (D30 × D30) ÷ (D60 × D10)
Cc = (1.75 × 1.75) ÷ (11.50 × 0.18)
Cc = 3.0625 ÷ 2.07
Cc = 1.48 _
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Step 4: Interpretation

→ much greater than 4 → indicates well-graded soil.

→ lies between 1 and 3 → also supports well-graded soil.

Therefore, this soil is Well-Graded Gravel/Sand (GW or SW) depending on fines content (here fines < 5%, so likely GW).

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Final Results

D10 = 0.18 mm
D30 = 1.75 mm
D60 = 11.50 mm

Cu = 63.89 _
Cc = 1.48 _
Soil Type = Well-Graded ـــــــــــــــــــــــــــــــــــــــــــ

08/25/2025

📊 What is FM in Sieve Analysis? 🤔
FM = Fineness Modulus – it’s an index number representing the average particle size of aggregate.
It’s calculated by adding the cumulative % retained on standard sieves and dividing by 100.

🔍 Effect of FM on Concrete:

Higher FM → Coarser aggregate → Less water demand, but may reduce workability.

Lower FM → Finer aggregate → Higher water demand, better workability but more shrinkage.

✅ Ideal FM Range for Sand: 2.3 – 3.1 (for good concrete mix)

⚠ Too high or too low FM can affect strength, durability, and finishing of concrete.

05/25/2025

Common Waterproofing Methods.

Cementitious Waterproofing.
This method uses a mixture of cement, sand, and polymers to create a waterproof coating, often used in basements, water tanks, and pool areas.

Liquid Waterproofing Membrane:
Applied in liquid form and cures into a seamless membrane, these methods use materials like polyurethane, acrylic, epoxy, or silicone.

Bituminous Waterproofing:
Utilizes bitumen, a form of petroleum, to create a protective layer, commonly used for roofs and foundations.

Sheet Membrane Waterproofing:
Involves applying pre-fabricated membranes, like those made from rubber or PVC, to create a waterproof barrier.

Polyurethane Liquid Membrane Waterproofing:
A liquid membrane that forms a flexible and durable barrier, often used for roofs and exterior walls.

Acrylic Coating:
A liquid coating made from acrylic resin, providing a waterproof barrier for roofs, walls, and concrete surfaces.

Integral Waterproofing:
This method adds chemicals to the concrete mix during construction to prevent water from entering through the pores in the concrete.

Factors Affecting Choice of Method:
The specific waterproofing method chosen depends on factors such as the type of structure, the severity of the water problem, the location, and the budget. For example, cementitious waterproofing is often used for basements and water tanks, while liquid membranes are preferred for roofs and exterior walls.

This image is an architectural or construction diagram illustrating a common method for waterproofing and drainage around a basement or foundation wall. It shows various layers and components designed to prevent moisture intrusion into the building's sub-grade areas.

Here's a detailed description of the elements depicted:

Top Section (Building Structure):
* The top of the diagram shows the beginning of the framed wall structure of a house (wooden studs, floor joists), indicating that this foundation supports a building.

Foundation Wall:
* A thick, poured concrete or concrete block "Foundation Wall" extends vertically downwards, forming the perimeter of the basement or crawl space.

Exterior Foundation Wall Treatment (Right Side - Exposed Earth):
This section shows the layers applied to the exterior of the foundation wall, facing the soil:

1. Foundation Wall Dampproofing or Waterproofing:
* This is shown as a black layer applied directly to the exterior surface of the concrete foundation wall.
* Dampproofing typically prevents moisture from migrating through the wall via capillary action, while waterproofing provides a barrier against liquid water under hydrostatic pressure. The label indicates it could be either, depending on the specific product and application.

2. Drainage Mat (or Gravel Backfill):
* Applied over the waterproofing/dampproofing layer, this is shown as a textured, tan-colored material.
* A drainage mat (also known as a dimple board or panel) creates an air gap or channel for water to flow downwards freely, rather than pressing against the foundation wall.
* Alternatively, "Gravel Backfill" could serve a similar purpose, providing a permeable layer for water drainage.

3. Filter Fabric:
* A blue, woven fabric is shown wrapping around the drainage mat and extending down to the perimeter drain.
* This filter fabric (also known as geotextile fabric) prevents fine soil particles from clogging the drainage mat or the perforated drain pipe below, while still allowing water to pass through.

4. Earth/Soil:
* The surrounding brown, textured area represents the excavated earth that will be backfilled against the foundation.

Bottom Section (Footing and Drainage System):

1. Wall Footing:
* A wider concrete base, the "Wall Footing," extends horizontally from the bottom of the foundation wall. This distributes the weight of the house over a larger area of soil, preventing differential settlement.

2. Perforated Perimeter Drain:
* A large, white, cylindrical pipe with visible holes is situated just outside the footing. This is the "Perforated Perimeter Drain" (also known as a French drain or weeping tile).
* Its purpose is to collect water that drains down the foundation wall and from the surrounding soil, directing it away from the foundation to a sump pit or daylighting outlet.

3. Gravel Backfill:
* A layer of "Gravel Backfill" surrounds the perforated drain pipe. This coarse material allows water to easily percolate down to the drain pipe and prevents the pipe from becoming clogged with fine soil.

Interior Section (Left Side - V***r Barrier and Slab):

* V***r Barrier:
* A white sheet is shown underneath the concrete slab, extending up the interior side of the foundation wall.
* A v***r barrier (or v***r retarder) prevents ground moisture from migrating upwards through the concrete slab into the living space, protecting flooring and improving indoor air quality.

* Concrete Slab:
* A horizontal concrete slab forms the basement floor, resting on the ground and the v***r barrier.

Purpose of the System:
This entire system works together to:
* Keep the basement dry: By diverting water away from the foundation.
* Prevent hydrostatic pressure: The drainage mat and gravel relieve pressure that groundwater might exert on the foundation wall.
* Protect the foundation: By reducing exposure to moisture, which can lead to degradation over time.
* Improve indoor air quality: By preventing moisture and radon gas from entering the basement.

In essence, the diagram provides a clear visual explanation of best practices for exterior foundation waterproofing and drainage, crucial for the longevity and health of a building.

11/23/2024

What is Fibre-reinforced concrete

Fibre-reinforced concrete (FRC) is concrete that has fibrous materials mixed in to increase the concrete's durability and structural integrity. FRC has small, short, and discreet fibres that are randomly oriented yet uniformly distributed throughout the concrete. The fibres can be circular or flat, and often makeup one to three per cent of the concrete mix's total volume. Common fibres used in reinforced concrete include steel, glass, synthetic, and natural fibres.

Why fibres are used?

On its own, concrete lacks tensile strength and is prone to cracking. But fibre-reinforced concrete can improve tensile strength and control cracking in concrete structures that are often caused by plastic shrinkage and drying shrinkage. Fibres in concrete can also reduce the permeability of concrete, which limits the amount of water that bleeds out, further reducing shrinkage cracking during curing.

The necessity of Fiber Reinforced Concrete
1- It increases the tensile strength of the concrete.
2- It reduces the air voids and water voids the inherent porosity of gel.
3- It increases the durability of the concrete.
4- Fibers such as graphite and glass have excellent resistance to creep, while the same is not true for most resins. Therefore, the orientation and volume of fibres have a significant influence on the creep performance of rebars/tendons.
5- Reinforced concrete itself is a composite material, where the reinforcement acts as the strengthening fibre and the concrete as the matrix. It is therefore imperative that the behaviour under thermal stresses for the two materials be similar so that the differential deformations of concrete and the reinforcement are minimized.
6- It has been recognized that the addition of small, closely spaced and uniformly dispersed fibres to concrete would act as crack arrester and would substantially improve its static and dynamic properties.

Types of Fibers :
1- Steel fibres
2- Glass fibres
3- Carbon Fibers
4- Cellulose Fibers
5- Synthetic Fibers
6- Natural Fibers

Advantages Of Fibre Reinforced Concrete :

1- High modulus of elasticity for effective long-term reinforcement, even in the hardened concrete. Does not rust nor corrode and requires no minimum cover.
2- Ideal aspect ratio (i.e. the relationship between Fiber diameter and length) which makes them excellent for early-age performance.
3- Easily placed, Cast, Sprayed and less labour intensive than placing rebar.
4- Greater retained toughness in conventional concrete mixes.
5- Higher flexural strength, depending on the addition rate.
6- Can be made into thin sheets or irregular shapes.
7- FRC possesses enough plasticity to go under large deformation once the peak load has been reached.
8- Increased durability and high flexural rigidity. 9- Reduced permeability, bleeding, and formation of microcracks. 10- Minimum weathering effect. 11. Reduces deflection. 12. Minimum corrosion.

Disadvantages Of Fibre Reinforced Concrete:

1- Fibres are costly.
2- The fibres should be uniformly distributed in concrete because they may not mix well and form lumps.
3- The size of the coarse aggregate is restricted to 10 mm.
4- Mixing of fibres in large volume could be tedious.
5- Construction with FRC skilled labours.

11/12/2024

Flakiness and Elongation Index Test

Flakiness and Elongation Index Test are very important tests to be performed on aggregate in the laboratory. This test gives the percentage of flaky and elongate aggregate present in the total aggregate sample.

Aggregate shape, size, and surface texture majorly affect the properties of freshly mixed concrete more than the properties of hardened concrete.

Angular, flaky, rough-textured, and elongated aggregate particles require more water to produce workable concrete than the smooth, rounded compact aggregate. Also, such irregular-shaped aggregate cement content must also be increased to maintain the water-cement ratio.

Elongated and flaky aggregate, when used in the construction of pavement may result in failure of the pavement due to their random position under repeated loading and vibration.

It is important to keep the amount of flaky and elongated aggregate within permissible levels. Generally, flaky and elongated aggregate are avoided or are limited to about 15 % by the weight of the total aggregate.

Flakiness Index
The flakiness index of aggregate is the % by weight of the particles (aggregates) whose thickness is less than 3/5th(0.6 times) of their mean dimension.”

Elongation Index
The Elongation index of aggregate is the % by weight of the particles (aggregates) whose length is greater than 1 and 4/5th (1.8 times) of their mean dimension.

10/20/2024

lightweight concrete using styro beads.

10/17/2024

https://youtu.be/EqnGVSbKcps?si=IlX17Z3q7N3W7C_l

10/17/2024

Soil Nailing Procedure

What is Soil Nailing?

Soil nailing is an economical technique used to stabilize existing slopes and construct retaining walls from the top down.

This soil reinforcement process uses steel tendons which are drilled and grouted into the soil to create a composite mass similar to a gravity wall. Shotcrete facing is typically applied, though many architectural options such as precast panels or “green” vegetated cells are available for permanent wall facings.

What Are the Advantages of Soil Nailing?
The process is very versatile. It is easy to shore along irregular curves and surfaces and installation methods can be modified according to constrained access. For shoring walls higher than about 10 feet, soil nailing is more feasible and more economical than driven piles. It is also quieter than driving piles. When space for shoring is limited, especially for tall retaining structures, soil nailing produces a much smaller footprint than laying back a slope.

What Are the Alternatives to Soil Nailing?
Driven piles
Laying back a slope
Pre-excavation compaction grouting
Cut retaining walls

How is a Soil Wall Installed?
This stabilization method reinforces existing soil or weathered rock by First, excavating a pit to a depth of four to five feet and creating a vertical face along the edge of the cut. Second, drill a series of horizontal or near horizontal holes along the face of the cut. Next, insert a threaded steel bar with centralizers into each hole. Fourth, flushing and filling each hole with cementitious grout. And finally, after the grout is cured, a bearing plate and nut are installed onto each of the nails and tightened against the face of the cut. When this sequence or “lift” is finished, the pit is excavated another five feet – extending the vertical face of the wall downwards. The process of drilling, inserting bar, grouting, and installing plates are then repeated until the desired wall height is attained. In this way, a stabilizing wall is constructed from the top down in five-foot increments.

A constructed face is usually applied for shoring. Typically, reinforcing wire is secured to nail heads before applying three to four inches of sprayed-on shotcrete. Permanent walls can be made more pleasing to the eye by imprinting a texture or pattern, by facing the wall with stacked stone or block, or by applying aesthetic landscaping.

10/13/2024

Cracks on a concrete slab can occur due to various reasons. Here are some common causes:

1. Shrinkage: Concrete shrinks as it cures, leading to cracks.
2. Settlement: Soil settlement or uneven foundation can cause cracks.
3. Thermal expansion: Concrete expands and contracts with temperature changes, causing cracks.
4. Poor construction: Inadequate preparation, mixing, or finishing can lead to cracks.
5. Weak subbase: A weak or unstable subbase can cause cracks.
6. Overloading: Excessive weight or pressure can cause cracks.
7. Weathering: Exposure to weather, especially freeze-thaw cycles, can cause cracks.
8. Chemical damage: Exposure to chemicals, like salt or acid, can damage concrete.
9. Poor drainage: Water accumulation can cause erosion and cracks.
10. Soil movement: Soil movement or erosion beneath the slab can cause cracks.
11. Tree roots: Tree roots growing beneath the slab can cause cracks.
12. Poor curing: Inadequate curing can lead to weak concrete and cracks.

It's important to address the underlying cause to prevent further damage and ensure effective repair

08/30/2024

Core Cutting Test

The Core Cutting Test is a laboratory test used to determine the density and air voids of bituminous pavement layers. It involves extracting a cylindrical core sample from the pavement and measuring its weight, diameter, and height.

Calculation:

1. Calculate the bulk density (ρ) using the formula:

ρ = (Weight of core) / (Volume of core)

1. Calculate the air voids (%) using the formula:

Air voids (%) = ((Theoretical density - Bulk density) / Theoretical density) x 100

Factors Affecting Results:
1. Sampling location and depth
2. Core extraction method
3. Sample handling and storage
4. Laboratory testing conditions
Importance:
The Core Cutting Test helps evaluate the quality and performance of bituminous pavement layers, ensuring they meet design specifications and are resistant to deformation and cracking.

Copyed

12/05/2021

07/24/2021

Pervious concrete (also called porous concrete, permeable concrete, no fines concrete and porous pavement) is a special type of concrete with a high porosity used for concrete flatwork applications that allows water from precipitation and other sources to pass directly through, thereby reducing the runoff from a site and allowing groundwater recharge.

Pervious concrete is made using large aggregates with little to no fine aggregates. The concrete paste then coats the aggregates and allows water to pass through the concrete slab. Pervious concrete is traditionally used in parking areas, areas with light traffic, residential streets, pedestrian walkways, and greenhouses. It is an important application for sustainable construction and is one of many low impact development techniques used by builders to protect water quality.