Questions tagged [concrete]

For questions about the material concrete, or its application in an engineering context. Concrete is a composite material composed mainly of water, aggregate, and cement.

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What is the best insulation wall for a house? ACC wall, Cavity wall, etc

Normally, people use Autoclaved Aerated Concrete (AAC) to build a concrete house because ACC is a good thermal insulation brick that easy to buy and not expensive ...
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0answers
26 views

Moisture sensor for Mixers

I'm looking for alternatives to measure the moisture content in a concrete mixer machine. The ones on the market are expensive, like Hidro-Mix for apparent reasons; mixers are a hostile environment ...
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0answers
109 views

Maximum allowable crack in Post Tension concrete

What is the maximum allowable crack size dimension in a post-tension concrete slab before it is considered a "structural" crack, in Arizona, USA? Is there a certain standard for this. I have tried ...
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0answers
52 views

Crooked floor, but ceiling with no incline - could it possibly be a screed?

This question is related to the situation in an apartment in a reinforced concrete building that is approximately 30 years old. The ceiling is almost perfectly straight and level. However, the floor ...
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0answers
10 views

What degree of open span/narrow support can rigid PIR thermal insulating foam sustain under the short term load of setting concrete?

I've found data related to the deformation and shear performance of typical PIR (polyisocyanurate) foams such as Celotex/Kingspan, but I'm not sure how to use these figures in my own situation. I am ...
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201 views

Bonding steel plate to fiber cement sheet effectively

I've been trying to produce a cheap panel using fiber cement and zincalume sheet. There is a research paper that I read about bonding steel plate to concrete to increase their tensile strength by ...
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0answers
70 views

How to consider shear forces in CEB/fib 2010 three-layer model for concrete slab design?

I have a question about design of concrete shells with three-layer method described in p.7.3.2.2 fib Model Code for concrete structures. The main idea of method is that we divide shell on three layers....
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0answers
172 views

Why do we dig holes and fill them in with concrete?

I'm watching construction of a new building across from my office. The old building has been demolished and the demo team has completed taking everything away and a new company has come in to start ...
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5answers
128 views

Exactly what makes steel-concrete composite beam better than pure steel?

A composite action beam may have a concrete section the top, carrying the compression load, and steel at the bottom, carrying tension. But I have always thought that concrete had lower strength for a ...
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2answers
2k views

Can a retention/detention pond and a parking-lot be constructed in the same site foot-print?

Retention/Detention Ponds are often added to a site-design to mitigate storm-water runoff. Enhanced Porosity Concrete (EPC), aka Pervious Concrete, can be used as a parking-lot pavement that allows ...
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1answer
7k views

What are the regular holes in poured concrete walls called?

These holes are caused by bars that are put through the frame before the concrete is poured and then clamped, so the mold can't swell outward. Is there a name for these holes though that is widely ...
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1answer
1k views

Is there a way to derive a formula of modulus of rupture vs compressive strength?

Is there a way to derive a formula of modulus of rupture (flexural strength) vs compressive strength? I want to know is there any mathematical reason for the $\sqrt{f_{c} ^{'}}$ placed somewhere in ...
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1answer
57 views

Raised plywood false floor for heavy equipment usages

I have a electronics assembly company, and we run two assembly lines. They consist of several machines, with the heaviest being around 4000lbs, on 6 metal casters. We currently have the line on a ...
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2answers
94 views

Dependency between load capacity for reinforced concrete slab and thickness

How does the load capacity for a reinforced concrete slab depend on the thickness of the slab? Example: Let's suppose that we have the following constants: concrete quality (including the maximum ...
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1answer
152 views

How will using desert sand instead of concrete sand affect my concrete recipe?

I've read that desert sand is too round for concrete mixes. But, I'm not building a dam, I'm building a 3 foot landscaping wall. I'm interested in using desert sand for the color, so this is an ...
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2answers
70 views

Which design to maximize friction for a device standing on concrete?

I have a device 4cm X 5cm X 15cm that stands on asphalt/concrete/road. So, the device is taller than its base which makes contact with the asphalt. I want to maximize the friction so that the device ...
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5answers
143 views

Reinforced concrete by steel, poor durability, why?

I've been reading up about reinforced concrete, as it is one if not the cheapest way how to build (with some solid foundation). I found out that it actually has quite poor durability (50-100 years or ...
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1answer
39 views

Jointed reinforced concrete tie-bar smoothness

We know that in Jointed Reinforced Concrete pavements we use dowels and tie bars. Why are dowel bars Smooth and tie bars are deformed? Dowels are used to transfer about 40% of the load from one slab ...
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1answer
687 views

Shear strength of reinforced concrete filled PVC pipe

BACKGROUND: I'm burying a 3 foot x 4 foot drainage box (2 foot tall) in my driveway to hold/distribute excess gutter flow (1" of rain produces ~21cuft). I've constructed the walls with brick, laid on ...
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2answers
44 views

Where to place air, water and electric cables in a composite beam [closed]

If water, gas and electrical cables have to pass through three (3) openings provided in the cross section shown in Figure 2, with tangible and scientific arguments specify the adequate opening for ...
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1answer
87 views

installing swing hook before concrete is poured

I want to place a swing hooks in place before the concrete is poured so that , i dont have to drill a hole later. My contractor is not ready to make these bolts with TMT bars itself.. what kind of ...
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3answers
112 views

Does screed increase the slab tension capacity?

Does a screed applied over the slab increase the slab tension capacity? Somehow it's counter intuitive because adding weight on the slab should tension it, but do the slab and the screed behave as a ...
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2answers
817 views

Why is desert sand not processed to make it suitable for concrete?

The shape of the sand grains from our planet's deserts is too round to be used in concrete (1, 2, 3). This is why we are drawing the last sand resources from natural beaches for making concrete for ...
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1answer
57 views

What effect does the weight of a wall have on the steel in the reinforced concrete below?

Considering the two options build internal wall on top of 10 cm deep concrete slab reinforced with 7.7 mm smooth steel wire mesh build internal wall on top of 30 cm deep concrete floor ...
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0answers
29 views

How to calculate load bearing capacity of a floating pavement?

Given tire load of a vehicle, how do I calculate load bearing capacity of a non-reinforced concrete pavement floating on a layer of heat insulation material, which is on the RC base? I can't figure ...
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0answers
66 views

Is it possible to measure the concrete workability by a mobile app one day? [closed]

After studying all methods that can measure the concrete slump, I found 62 devices that service this purpose at the same time these devices are expensive and not practical enough, for this reason the ...
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0answers
42 views

House construction using concrete panels

Background Information Currently looking to buy a house in the Southampton area in the UK and have noted there are quite a few houses which use a concrete panelling construction technique see example ...
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2answers
125 views

Reinforced mesh at different distance in a concrete slab?

Trying to determine some information regarding the reinforced concrete slabs (reinforced with mesh) in an apartment, by looking through the holes in the middle of the rooms for lights, I've come ...
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0answers
23 views

How to build multiple large scale fish tanks with water at different temperatures

I am wondering at a high level what are the material components that might be used in building several large scale fish tanks that are temperature regulated like on a fishing farm. For example, what ...
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0answers
50 views

How to grind into concrete ( not core drill )

I have a very specific and weird task I need to accomplish. I have a concrete wall that I need to get samples of the concrete dust to grind and get them tested, i plan on using a plunge router with a ...
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0answers
27 views

Difference Between minimum steel required in Slabs and Shear Walls

My question is very simple, I need to know why the minimum reinforcement for slabs is less than the minimum reinforcement required in Shear walls? What are the criteria and reasons to set minimum ...
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0answers
44 views

Will screed on plywood do instead of beam and block, to replace a floor?

I'm gutting and redoing an older house (early 20th C, ordinary suburban terrace house, London UK). I'd planned beam and (dense) block for the upstairs structural floor, for a few reasons, and already ...
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0answers
346 views

Shift Concrete Column by few inches

While building the foundation of a house, the concrete columns were built 15cm (6 inches) from the planned position, which is reducing the space for a door. The position that should have been there ...
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2answers
167 views

Why does rebar in reinforced pre-stressed conrete reduce in deflection if compressive stress is applied to member?

According to What is Prestressed Concrete? - Practical Engineering, one way to reduce deflection in the steel rebar is to pre-stress the rebar by applying compressive stress in the member before ...
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3answers
82 views

Why we say prestressed concrete is "more efficient"?

In my class my teacher said that prestressed concrete is more efficient, and when asked why he talk because of the constructing process. I believe because you have no cracked section hence you can use ...
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4answers
1k views

Why does a beam in shear crack at 45 degrees?

Why does a beam in shear like in this picture crack at 45 degrees instead of vertically? This is called "Punching shear", and requires concrete reinforcement at an angle: Assuming that the ...
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2answers
238 views

Impact of having flexible electrical hose buried into the reinforced concrete slab

Given: a reinforced concrete two-way slab at about 160 mm (the edges are cantilevered between the concrete walls) the electricians buried the flexible electrical hose into the slab (red lines in the ...
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1answer
42 views

How do extra building levels affect the foundation design apart for the extra load?

I have been talking to some structural engineers trying to find one to design foundations for my contemplated bespoke building based on hi-cube 40-ft shipping containers. The initial concept is just ...
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2answers
92 views

Creep coefficient over time

I came across 2 creep coefficient diagram. First one is from Eurocode, second one is from elsewhere. I think the second one make sense, As the time progress, the creep coefficient shall increase, ...
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2answers
177 views

Concrete pad over filled, in-ground pool better with or without wall support?

We are currently having a project done in our backyard to: (1) fill an in-ground pool and (2) build a "sport court" (with a large concrete pad and some tiles) over top. The pool demolition ...
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1answer
35 views

Control joint and contraction joint in concrete

What is the difference between a control joint and a contraction joint in concrete? I mean, a control joint is to control the cracks in concrete due to temperature or shrinkage etc... I understand it. ...
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3answers
104 views

How does Gypsum Concrete work?

When mixed with water how does gypsum act as a binder in creating concrete?
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1answer
63 views

Are there any ways to know whether the element has failed under loading, while knowing only limited properties?

I opt to check whether a precast concrete wall (no reinforcements, only concrete) withstand both vertical and lateral loading condition but the only properties I know are the Young's Modulus, density, ...
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2answers
37 views

Can anyone help me with the concept of bearing stresses in steel reinforcement in Reinforced Concrete?

When there is tension reinforcement(steel) embedded in concrete, does it not also undergo bearing stresses on account of the weight of the concrete and other forces which are acting above the steel? ...
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1answer
40 views

How to reinforce concrete over a circular span

Last year we poured a RC suspended slab according to designs of a structural engineer. (Note we are just DIY home builders but have taken professional advice throughout.) The slab was cast with three ...
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1answer
79 views

Base Support for a Tree house

I am building a tree house in my backyard and it is going to be relatively simple. There are no parts that require drilling into the tree. The whole house is propped up by four 4x4 wood supports. I'm ...
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0answers
27 views

where did the concrete splitting test calculated stress formulat come from?

In compression test of cylindrical concrete sample we get the normal stress easily by dividing failure force by sample cross section, but how we can explain the formulat used to determine tensile ...
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0answers
30 views

Modern equivalent concrete strength to 'Class Ws 3/4" '

Consider the following extract from a UK reinforced concrete detail drawing dated 1970: What is the modern equivalent to this concrete class?
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2answers
60 views

Is there a standard formula available to calculate lateral concrete pressure from the measurements of lateral concrete strain?

As shown in the image, I have done a vibrating wire type strain gauge and pressure cell (not shown in the image) instrumentation on full scale form. the objective is to measure the lateral pressure of ...
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2answers
149 views

Why do lvdt sensors give us different results?

We take a cylindrical concrete sample and apply compression load on it, perpendicular to its head. To measure its strain we use 2 Lvdt(strain measurement devices)on both sides of the concrete sample . ...