Author: Mezie Ethelbert

Reading Time: 4 minutes Introduction To select the most appropriate type of compaction equipment, a project manager must know the characteristics, capabilities, and limitations of the different types of rollers. Generally, compaction equipment uses one or more of the following methods to accomplish soil densification: 1. Static weight (pressure) 2. Kneading (manipulation) 3. Impact (sharp blow) 4. Vibration (shaking) Factors to be considered when selecting compaction equipment i. Type and properties of the soil ii. Density desired to be achieved iii. Placement layer thicknesses iv. Size of job v. Compaction equipment available Spectrum of capabilities of different rollers See Table 1 for the spectrum…

Reading Time: 6 minutes A flexible pavement is made up of five distinct layers namely, subgrade, subbase, base course and surfacing or wearing course (Figure 1). Each of these layers requires special treatment to ensure they perform their function satisfactorily. Subgrade Subgrade describes the in-situ soil on which a road, an airfield, or a heliport is built. Subgrade includes the soil to the depth that may affect the structural design of the project or the depth at which the climate affects the soil. Depths up to 300 mm may be considered subgrade for pavements carrying heavy loads. The quality and natural density of this…

Reading Time: 4 minutes PROCEDURE Step 1. Clean the density bottle and stopper. Dry by rinsing with acetone or an alcohol-ether mixture and then blowing warm air through it at 105 °C to 110 °C. Weigh the bottle with the stopper to the nearest 0.001 g (m1). NOTE: In order to avoid distortion, the density bottle should not be dried by placing it in an oven. Step 2. Transfer the first soil specimen to the density bottle direct from its sealed container. Weigh the bottle, contents and stopper to the nearest 0.001 g (m2). Step 3. Add sufficient air-free distilled water or other liquid…

Reading Time: 17 minutes Planning is a general term that sets a clear road map that should be followed to reach a destination. It is a decision-making process that involves the break down of the project into definable, measurable and identifiable tasks/activities and then establishes the logical interdependence among them. When this planning is applied to construction work, it is called construction planning. Construction plans my exist at different levels which include corporate strategic plans, pre-tender plans, pre-contract plans, short-term construction plans, long-term construction plans etc. These levels of plans differ from each other but they are unique in four (4) steps in which…

Reading Time: 2 minutes Presently, our highways are filled with trucks that apply heavy radial truck tyre pressure of about 861.845 kPa (125 psi) to today’s pavement. Due to this increasing wheel load, conventional bituminous roads do not stand the test of time and polymer modification of bitumen studies have been on the rise as a solution to the challenge. Modified binders or asphalt are used to reduce the amount and severity of pavement distresses and to increase service life (about 4 – 6 years of additional service life or an average of 25% increase in service life). They also help improve pavement rutting…

Reading Time: 3 minutes Rolling tests are important because several types of compaction equipment used in construction works used to overlap. Test strips helps to make final determination of the most efficient compactor and compaction procedures. It also helps to avoid economic and time losses in field compaction. The test strip for rolling tests should be located adjacent to the project site. The following information are obtained from the test strip: 1. Most effective type of compaction equipment through the determination of maximum dry density and optimum moisture content of the proposed roller. 2. Optimum depth of layer. 3. Optimum compactor speed. 4. Number…

Reading Time: < 1 minute When digging strip footing on sloping ground, it is often necessary to introduce a stepped foundation (see Figure 2). This is necessary to reduce the depth of the foundation because the effort to get level ground under the foundation would increase the depth of the foundation on the high side of the ground (see Figure 1). Sloping a foundation reduces the cost of the foundation but it is necessary to know how to do this properly. The figures below show the ideal considerations in the sloping of the foundation (See Figure 3). Adapted from Building Construction Handbook by Roy Chudley…

Reading Time: < 1 minute When a freshly made concrete is placed inside its form or mould, it is necessary to compact this concrete properly to remove air voids, increase the density of the concrete and improve its strength. This compaction can be done manually using tamping rods or boards especially for small jobs. For more effective compaction, mechanical equipment such as poker vibrator is often used for the purpose. Poker vibrators consist of a hollow steel tube casing in which is a rotating impeller which generates vibrations as its head comes into contact with the casing. Effective compaction of concrete using poker vibrator required…