?Bonding of Old and New Concrete?

?In construction, there always comes a time when there is a need to bond hardened concrete (substrate) with fresh concrete topping/overlay. The aim of this post is to explain how to bond old and fresh concrete successfully.
Furthermore, we will review the strength of the interfacial bond between old and new concrete based on laboratory studies.

⏺Proper bonding is very important for adequate performance when the fresh concrete topping is used to overlay an existing hardened concrete. This construction feature is usually found in bridge deck construction, concrete pavements, precast filigree slab, pile caps (in some cases) etc. Proper bonding between the substrate and the topping is not always guaranteed unless simple precautions are taken.

⏺For adequate bonding, it is very important to prepare the surface of the substrate adequately. The preparation of the surface usually involves:

?Roughening the surface, and removal of all dirt, oil, grease, and loosened or unbonded portions of the existing concrete.

⏺By implication, the surface of the substrate should be hard, firm, clean, and free from loosened particles. This can be achieved by the use of chipping hammers, wire brushing the surface, etc.

?After this is done, the exposed concrete surface can be cleaned by using pressurized clean water, air, etc. The man hours involved depend on the area of the surface, location, and the ease of cleaning (e.g reinforcement obstruction).

?After surface preparation, there is usually a need to apply a bonding agent on the surface of the existing concrete in order to facilitate the bonding. Epoxy-based bonding agents are very popular for such operations. It is recommended that a bonding agent is applied prior to casting the fresh concrete.  In essence, the procedure should be ‘wet-to-wet’ as the bonding agent should not be allowed to dry before the fresh concrete topping is placed.

?In a research carried out by Vandhiyan and Kathiravan (2017), the compressive strength of monolithic and bonded concrete was compared using 150mm x 150mm cube specimens at 28 days. With an epoxy-based bonding agent, the compressive strength of the bonded concrete was about 5% less than the monolithic strength, while without the bonding agent, the compressive strength was about 28% less than the monolithic compressive strength.

?Research has also shown that the moisture condition of the substrate affects the shear bond strength of bonded concrete. Shin and Wan (2010) investigated the interfacial bond strength of old and new concrete considering saturated surface dry (SSD) and air dry conditions. Saturated surface dry is a condition in which the concrete contains moisture that is equal to its potential absorption, without the surface being wet or damp.

?At a water/cement ratio of 0.45 (for the topping concrete), the shear bond strength at the interface was about 44% greater when the substrate was at SSD condition than when it was air dry. At a water/cement ratio of 0.6 for the topping layer, an increase in shear bond strength was recorded, but there was a reduction in the compressive strength of the concrete.

⏺So the recommendation in this article is that when casting a topping layer of fresh concrete on old concrete, adhere to the following guidelines;

(1) Prepare the surface properly
(2) Make sure that the substrate is at saturated surface dry condition
(3) Use a bonding agent and follow the manufacturer’s technical recommendation properly.

Source : Article

# We are looking for a civil engineer who can do the following tasks 1, quantity/takeoff 2, prepare bid documents 3, supervision Location :- Butajira and Addis Ababa Minimum experience - Bsc degree in civil/cotm with 0yr experience…

# We are looking for a civil engineer who can do the following tasks
1, quantity/takeoff
2, prepare bid documents 3, supervision

Location :- Butajira and Addis Ababa
Minimum experience - Bsc degree in civil/cotm with 0yr experience

Contact me its urgent
@davitua

? ብዙዎች ስለስራ ቅጥር እና ቫካንሲ ይጠይቁናል

እስቲ ምክር ቢጤ ጣል እናርግላቹ

የዛሬ አምስት አመት ወይም አስር አመት የት መድረስ ነው ፍላጎትህ / ሽ?

የራስህን የኮንስትራክሽን ተቋም ማቋቋም? ወይስ አንድ ካምፓኒ ውስጥ ተቀጣሪ መሆን?

አንድ ሰው ሃብታም ነው የሚባለው የጊዜው እና የገንዘቡ «አለቃ» መሆን ሲችል እንጂ ብዙ ብር ስለተከፈለው አይደለም።

አንድ ትልቅ ተቋራጭ ውስጥ ተቀጠርክ / ሽ እንበል ...15 ሺ / 20 ሺ ይከፈልሃል ...ብር አለህ ነገር ግን የገንዘብህ እና የጊዜህ አለቃ አይደለህም።

በየወሩ ይከፈልሃል ስለዚህ የገንዘብህ አለቃ አይደለህም በሚወሰንልህ ጊዜ ፍቃድ ይሰጥሃል ስለዚህ የጊዜህ አለቃ አንተ ሳትሆን ሌላ ነው።

ምን መሰለህ አንተ ኢንጅኒየር ነህ ሌሎች ሞያዎች ላይ ተደግፎ ሳይሆን በግልህ ሊያንቀሳቅስህ የሚችል የሞያ ባለቤት ነህ ።

የዚህ ሞያ ባለቤት ከሆንክ ተቀጥሮ ለሌሎች መስራትን ትተህ ለምን የራስህን ድርጅት አታቋቅምም? እውቀት አለህ፤ የመስራት አቅም እና ተነሳሽነት አለህ የቸገረህ ገንዘብ ነው?

Well እስኪ አካባቢህን አስተውል የተመቻቹልህን አማራጮች ገምግም ... አንድ አማራጭ ልጠቁምህ መንግስት ለወጣቶች ያመቻቸው የስራ እድል ፈጠራ ... የCobel እና ሌሎች
የኮንስትራክሽን ስራዎች።

ከነዚህ እድሎች አላማህ የአሁን ድሎትህን ሳይሆን የማይነቃነቅ የነገ ምቾትህን ከሆነ ምትፈልገው ፤ ራእይህ ትልቅ ከሆነ ... ይህን ራዕይ ሊያሳካ የሚችል ገንዘብ የተወሰነ ቢሆንም ታገኛለህ እንዳንተ አላማ ካላቸው ጋር ሽርክና ብትፈጥር በአጭር ጊዜ
ውስጥ የራስህን ድርጅት ታስተዳድራለህ። ስራን አታጥላላ ስራን አትናቅ አላማህን በውስጥህ ይዘህ ዝም ብለህ ስራ የነገ ስኬትህ በአደባባይ ይጮኽልሃል።

እስኪ የ ኣንድ ድርጅት አጀማመር እንንገራቹ እንይ ስሙ ሰንሻይን ኮንስትራክሽን ይባላል የተጀመረው በስለት ገንዘብ ካፒታሉም 20ሺህ ብር ነው አሁን አሉ ከሚባሉ የኮንስትራክሽን ድርጅቶች አንደኛው ነው ።

ተክለ ብርሃን አምባዬ ትልቅ ቦታ እንደሚደርስ አምኖ በትንሽ ገንዘብ ይህን ድርጅት ጀመረ ። አሁን የደረሰበት ደረጃ ሳንወድ በግድ ስለሱ እንድናወራ ያስገድደናል።

እስኪ እነዚህን ስራዎች እንደ መነሻ ልንጠቁምህ በሃይድራውሊክስ ~

የሳኒታሪ ኢንስታሌሽን ስራን በትንሹ ብትሰራ

- የሃገራችን ፎቆችን ታዝበኃቸዋል ? አብዛኞቹ ትልቁ ስህተታቸው የሳኒቴሪ ኢንስታሌሽን ስራ ማለትም ከ ዳምፕነስ እናሌሎች ተያያዥ ችግሮች ጋ በተያያዘ ብዙ ሰው ሲያማርር ይስተዋላል  ፕሮፌሽናል በሆነ ሰው ስለማይሰሩ ከዚጋ ተያይዞ በሚመጡ ችግሮች ይጎዳሉ። አንተ ደሞ ዲያዝይን እና ኢንስታል የማረግ እውቀት አለክ እና ለምን ይህን ቢዝነስ የሚጠይቀው ትንሽ ካፒታል ስለሆነ ለመጀመር አታስብበትም ??..

የባኞ ቤት እቃዎች ገጠማ እና ዲዛይን ። በዚህ ስራ ራሱን ችሎ የተሰማራ ድርጅት በጣም ትንሽ ነው አስብበት ።

እና ሌሎች ኣዋጭ የ ኮንስትራክሽን ሃሳቦች ኣሉ ብቻ ኣንተ ኣስብ ... ቁጭ ብለህ ኣታማርር...

አሁንም እንድትረዳ ምፈልገው ነገር ቢኖር በመንግስት መስሪያ ቤቶች እና በግል ድርጅቶች ተቀጥረው የሚሰሩ ሰዎችን አይተህ ተማር ለነገ ሚሆናቸው ምንም ነገር የላቸውም የ«አበራሽን ጠባሳ
ያየ በእሳት አይጫወትም » እንዲሉ ይህን ለማረጋገጥ ተቀጣሪ መሆን አይጠበቅብህም።

በራስህ እምነት ይኑርህ ፤ ደፍረህ ወደ ስራ ግባ ስኬት አጠገብህ ናት!

Source
ETCONP telegram channel

Cont..

In our country Ethiopia the construction sectors are boost up due to modernization and industrialization. Wind speed data is prerequisite in designing of high raise buildings. In Ethiopia, the most common practice is to adopt design recommendations from European codes of practice which can be quite inappropriate due to the differences in climatical and topographical conditions. To foreground the present condition in Ethiopia, this paper tried to obtain the basic wind speed for different stations/towns. The basic wind speed data which is obtained from 159 stations are then compared with the design wind speed of 22 ​m/s according to EBCS 2015. Consequently, a basic wind speed zone map was prepared. The map was developed based on the basic wind speeds evaluated from the annual maximum records collected from each station. Hydrognomon Pythia-statistical analysis was done for different probability distributions. After their calculation the best fitting distribution between empirical and theoretical data was chosen using Kolmogorov-Smirnov test. The findings are clearly showing that the magnitude of the operating basic wind speed was increased in 14–150% from the constant of 22 ​m/s. By using best fitted probability distribution methods of each stations, obtained result are ranging from 25 to 55 ​m/s in Ethiopia.

@plusdesign

Wind Loads in our country's context

In some areas, wind load is an important consideration when designing and building a structure. Wind load is the load in pounds per square foot, placed on the exterior of a structure by wind. This will depend on:
The angle at which the wind strikes the structure
The shape of the structure (height, width, etc.)

Preventing wind damage involves strengthening areas where buildings could come apart. The walls, roof and foundation must be strong, and the attachments between them must be strong and secure. For a structure to resist hurricane and weak tornadic winds, it must have a continuous load path from the roof to the foundation -- connections that tie all structural parts together and can resist types of wind loads that could push and pull on the building in a storm.

Wind exerts three types of forces on a structure:
Uplift load - Wind flow pressures that create a strong lifting effect, much like the effect on airplane wings. Wind flow under a roof pushes upward; wind flow over a roof pulls upward.
Shear load – Horizontal wind pressure that could cause racking of walls, making a building tilt.
Lateral load – Horizontal pushing and pulling pressure on walls that could make a structure slide off the foundation or overturn.

High wind pressures can collapse doors and windows, rip off roofing and roof decking and destroy gable end walls. Roof overhangs and other features that tend to trap air beneath them, resulting in high uplift forces, are particularly susceptible to damage. Broken windows and doors can expose the building contents to serious damage from internal wind pressures and water entry.

✍ Good evening guys we will be releasing an introduction to wind loads in our country context the coming sunday
Stay tuned?

@plusdesign