Engineering Today

Limits For driveway road slopes in concrete asphalt paving as follow:  Longitudinal Slopes: shall not exceeded 14% this is for confort and safety of vehicles. Transvers slopes : should be a minimum 2% towards shoulders of the road, this slopes are made to drain away any comulicative water from rainfall or any from the road. Why concrete needs curing

Mortar is a mix of cement+water+ sand +lime. It's used for bricks or blocks building. 5 types of cement mortar are commonly used in construction work. Type M mortar : high Compressive Strength mix. It's recommend for high compression loads. Type M mortar consist of the following quantities properties ( by volume) 1portland cement+ 1/4 lime +3.5 sand. Type S mortar:  high bond strength mortar. It's recommend for structures subjects to lateral loads or below grade retaining walls. Type S mortar is made by ( properties by volume): 1portland cement+ 1/2 lime+ 4.5 sand  Type N mortar:  it's the general purpose mortar multiple usage in construction work for most of constructions. The components of type N mortar 1 Portland Cement+ 1 lime + 6 sand ( properties by volume). Type O mortar:   high lime low compressive strength. Common uses in non load bearing structures. Type O mortar consist of 1portland cement + 2 lime+ 9 sand ( properties by volume). Type K mortar: very ...

Definitions of block and brick Brick and Block common types of Walls partitions in concrete structures. They have many different types some of them: Bricks made of clay or concrete, have a rectangular section with maximum dimensions 25x12x13 cm. Common type 25x12x6cm Blocks made of clay or concrete CMU, have dimensions L ( length) not exceeded 6b(width). Common dimensions is 40x20x20 cm, 40x25x20cm. Solid building unit: have net area greater than 75% gross area. Perforated building unit: when net area from 25%to50% from gross area. Hollow building unit: when unit area from 50% to 75% area gross. Expansion Joint in walls. In continues walls like fences, maximum distance between expansion joints is 12m for clay brick wall and 9 m for concrete blocks. Loads to be taken in design of Walls:  Minimum loads should be taking is own weight + 25kg/m2. The design of Walls not depending on structure loads only, sound and heat isolation should be reviewed. Allowed  horizontal deflection du...

Curing : It is the process in which moisture, temperature and evaporation are controlled to prevent shrinkage and contraction of freshly poured concrete which may affect on strutural strength of concrete. Problems in uncured concrete  Due to increase of temperature, thermal stresses will cause minor cracks in concrete Loss of water due to evaporation in concrete will stop hydration of cement which decrease compressive strength. Start of curing Curing start after setting the concrete, three or four hours after placing the concrete is adequate. Importance of curing : Experiments shows compressive strength of concrete structures increase with curing as shown in attached graph. Curing for 3 days reach 75% of cubic strength of concrete. Factors affecting on curing Evaporation in concrete is a main factor need to be controlled in curing, evaporation is affected by Temperature, wind and moisture, generally increasing evaporation above 0.5kg/m2 per hour will cause plastic cracks in fresh ...

اولا ما هو البوليمرات المسلحه بالالياف؟ هي عباره عن مركبات كيميائية تتكون من عنصرين أحدهما الألياف والآخر راتنج بوليمري يتم دمجهما مع بعض لتكون العنصر الانشائي. ثانيا. انواع الالياف هي ألياف الكربون , ألياف الزجاج ، ألياف الآراميد  مميزاته: مقاومه عاليه الاحمال ، خفه الوزن ، عدم قابليتها للصدأ و سهولة الاستخدام ثالثا عيوب الفيبر :  الفيبر والخرسانة هما عناصر قاصفة اي تجعل سلوك انهيار المنشآت الخرسانية مفاجئ وهذا شئ خطير جدا علي أرواح الناس عكس السلوك المطيل لحديد التسليح لذلك اعطي الكود المصري وجميع الاكواد العالميه اشتراطات خاصه جدا جدا لاستخدام الفيبر بديل للحديد. بالإضافة إلي ذلك ارتفاع سعره مقابل الحديد  الخلاصه:  استخدامه حاليا في ترميم و تدعيم المنشآت الخرسانية مع الحديد ولكن لا بديل عن الحديد حتي لا يحدث انهيار مفاجئ المنشآت  لقد شرحت محاضره عن ترميم وتدعيم المنشآت الخرسانية باستخدام الفيبر في نقابه المهندسين بالأقصر عام ٢٠١٩  * سيتم اضافه المحاضره كامله لاحقا   Fiber reinforced polymers FRP Steel rebar color chart

In structural engineering knowledge there are different types of cement structural engineer should select between them to suit the environment and type of structures. Types of Cement used in concrete structures. Type I  it's general type of cement, usually most common type of Cement Type II  : moderate resistance to sulfates,  usually used when sulfates are founded in soil or ground water. Type III : high early strength, it's used when quick remove of form-works or early strength is required. Please note High early strength NOT meaning high Compressive Strength,  Type IV : low heat cement, it's recommend to use in bulk or mass concrete which high hydration temperature will generate. The generated temperature may cause cracks in concrete. Type V : high resistance to sulfates. It's commonly used in areas where high sulfates concentration in soil or ground water is founded. Concrete compressive strength acceptance Criteria

Curing Methods In concrete structures there are basic methods used to increase strength of strucures, curing is the most factor structure design, construction engineer should follow to ensure concrete reach the desired compressive strength. 1-   Continuous or frequent applications of water to the surface ·    P onding: it used mainly in horizontal surfaces by applying by pond of water ·       Continuous Spraying of water by sprinklers or any, avoiding alternate wetting and drying and the application of cold water to warm concrete surfaces; ·         Covering the surface with a damp absorbent material like canvas fabric or any, usually adding water to canvas two or three times per day. 2- Covering the surface to prevent water losses ·     covering the surface with an impermeable material such as polyethylene, which should be well sealed and fastened ·      spraying the su...

 Concrete strength acceptance Criteria for concrete structures As per ACI318 The compressive strength of 28 days is considered satisfactory if both conditios are met,  1. No single strength test falls below the specified compressive strength by more than 500psi (32kg/cm2) for FCU>5000Psi (340kf/cm2)& or 0.1Fcu for FCU<5000psi(340kg) cm2)  2.the average of every three consecutive strength test equal or exceeded the specified compressive strength.   chmidit hammer test accuracy

In strutural engineering works, Every steel bar has a standard color at the end which may use to identify steel bar diameter as follows:  -Steel bar diameter 10mm use green color. Steel bar diameter 12mm uses red color. Steel bar diameter 16mm use blue color. Steel bar diameter 18mm use White color. Steel bar diameter 20mm use brown color Steel bar diameter 22mm use yellow color. Steel bar diameter 25 use dark green color Steel bar diameter 32mm use black color.  , the attached picture show every steel bar diameter with the corresponding color in Egypt