Concrete Block
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a. Goal: provide shelter for the CYEC children
b. Benefits of the specific technology to the community
  • economical
  • energy efficient - better than wood homes
  • fire-resistant: concrete block is a non-combustible material
  • involve minimal maintenance and upkeep
  • design flexibility: have the flexibility to do just about anything you want. Whether it be a one- story home or a three story home with such options as columns, arches, high ceilings and tall windows concrete block provides the needed flexibility for every type of job.
  • durability: one of the most durable materials
*c. Local Availability: are available locally
d. Regulatory or Industry Standards for Implementation of Technology
i. International Standards: International Building Code
ii. Local code enforcement: none found
e. Description of Product (s) or Process (es) and its Functionality (Succinct but Detailed Enough)
The standard concrete block is a rectangular 8X8X16-inch unit (200X200X400 mm) made mainly of portland cement, gravel, sand, and water.
f. Design parameters
Walls and foundations are created by stacking the blocks with a layer of mortar between the blocks. Although a simple mortar construction may be adequate for a small free-standing garden wall, it will not be sufficient for foundations, retaining walls or load-bearing walls in houses.

The strength of block construction can be improved by completely filling the voids with concrete, but it is more cost effective use steel reinforcement. Reinforcement can be achieve in several ways. The picture below shows a few examples of such reinforcement. Steel bars (usually called rebar) can be placed vertically within the blocks at evenly spaced intervals, or at piers like that shown in the first example. (Piers are the concrete equivalent of posts and beams in wood framing.) This provides resistance to flexural stress. Steel rebar or steel mesh is placed horizontally between rows of blocks to provide resistance to shear stress. Note in both examples, control joints are indicated. A flexible caulking must be placed at regular intervals in place of mortar to accommodate expansion and contraction of the walls. Without these joints, concrete block walls will inevitably develope cracks.
external image Reinforcement.gif
Courtesy of Architectural Graphics Standards, 5th Ed.

Electrical conduit and plumbing can be placed within the walls as the wall is constructed. The top of the divider sections can be hammered out to make room for pipes, or specially designed blocks can be used. Door and window frames (usually wood or steel) are placed in position and the wall built up and around the frames. For large openings, a lintel is needed, It can be constructed by using extra reinforcement in the blocks immediately above the frame or a prefabricated concrete, steel or wood lintel can be used provided it is properly tied into the surround blocks.
external image PipeInBlock.gif Special attention must be paid when finishing the top of the wall. If the roof is to be of standard wood construction, accommodation must be made for securely attaching the roof to the walls. Usually, the top is capped with a wood plate that is anchored to rebar or bolts that protrude from the top of the wall. If a concrete roof is to be poored, the rebar from the walls is bent over and into the forms before the poor.

i. Sizing
ii. Materials needed for Fabrication/ Construction of Technology

Building with Concrete Blocks

Design
  • In order to minimize the need for cutting concrete blocks, all horizontal dimensions of walls should be multiples of nominal half blocks (most commonly 20 cm) and all vertical dimensions should be multiples of nominal full-heights (20 cm). This also applies to the positioning of doors and windows.
  • In order to minimize the risk of cracking, the lengths of individual wall sections should not be greater than one-and-a-half times the height.
  • Hollow blocks should be specified when good thermal insulation is required. These blocks are also useful when additional structural stability is needed, eg in earthquake areas, because the cavities align vertically and can be filled with reinforcing steel and concrete.
  • Blocks with a rough surface (open textured), as in the case of most lightweight blocks, are advantageous, because they
    - provide a better key for bedding mortar and applied finishes,
    - have less capillary attraction for water and dry out more quickly after rains.
Construction
  • Concrete blocks must be dried out thoroughly before use, otherwise drying will continue after building the wall and shrinkage cracks may develop. Only dry blocks should be used and they should not be wetted before laying. Instead the preparation of the mortar must take into consideration that the blocks absorb some of the water.
  • Mortars used for bedding should not be too rich in cement. Cement: hydrated lime: sand mixes of 1: 2: 9 or 1: 1: 6 have a high water retention and good workability. It is important that the strength of the mortar does not exceed that of the blocks, so that the joints can absorb a limited amount of movement, preventing the blocks from cracking.

1. Various Options
iii.Other resources Needed for Implementation/ Use
  1. Construction Equipment
  2. Labor
  3. Technical Consultation
  4. Transportation Requirements
  5. Energy Requirements
  6. Space
  7. Spare Parts
  8. Time for Construction
iv. Technical Skills Required to Operate or Utilize
  1. Training Requirements
g. Associated Costs
i. Capital
ii. Operations & Maintenance
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