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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11
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2answers
562 views

Why do air entrainment admixtures improve the freeze-thaw resistance of concrete?

It is stated on here that: Air-entraining admixtures cause small stable bubbles of air to form uniformly through a concrete mix. The bubbles are mostly below 1 mm diameter with a high proportion ...
0
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1answer
30 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 ...
2
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1answer
121 views

What's the difference between Creep and Dynamic Viscous Damping?

What's the mechanism behind each phenomenon and what's the difference between them? Why is Creep considered in the Constitutive Equation (taken as an inelastic strain) while damping is considered in ...
0
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0answers
21 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 ...
0
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2answers
28 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? ...
0
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1answer
37 views

Help needed: dimensions and weight of concrete base required

We have an art project that involves a steel structure. The structure weighs around 200KG; it is 3 meters tall and 1 meter wide. It will be exposed to wind outdoors of around 38m/s. What are the ...
0
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0answers
27 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?
4
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3answers
125 views

Why is the stress distribution on concrete approximated like this?

I'm reading here on reinforced concrete. It is explained there that in calculations, the actual stress distribution is replaced by a constant stress distribution over some limited distance from the ...
1
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0answers
63 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 ...
5
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2answers
112 views

Why railroad concrete tie tips become dry first after a rain?

I've witnessed this phenomenon: Why are only the tie tips dry? Why are only the stones around the tips dry? This is a railroad in Ukraine in the morning after a rain at night. Around 80% of observed ...
0
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2answers
56 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 ...
3
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3answers
113 views

Trapping heat by curing of concrete under plastic sheets

Although curing of concrete under plastic sheets is a recognized technique, I have some doubts about it. I think that the plastic sheets may trap heat coming from the exothermic reaction, which will ...
-1
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1answer
35 views

How to choose the dimensions for a prestressed I-beam?

I need to design a simply supported symmetric I-beam (for a school problem). However, I can't find much information about the selection of the section or if there exist any standards for that. the ...
3
votes
2answers
64 views

Tiled/block pavement used to pave high traffic roadway?

We're normally paving the high-traffic road with concrete or asphalt. While for sidewalk/garden, we use pave block/tiles (either concrete or else) Common reason is because pave block/tiles doesn't ...
2
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0answers
58 views

Any Idea of This China's “Transparent Concrete”?

I am currently make an attempt to make miniaturized version of this China's solar highway on my garage https://www.youtube.com/watch?v=zK8FvzI3yDA Just so i can re-evaluate the performance However, I ...
0
votes
1answer
30 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. ...
2
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0answers
31 views

water leak through subterranean cable penetrations in concrete

See the image below for the detail of 4 no. cable ducts that run from a trench in a raft foundation (on the left) through an approximately 1 m square penetration in the raft foundation, through soil (...
-1
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3answers
98 views

can ceramic be used as a building material?

From what I read, concrete has much lower compressive strength than ceramics. So why aren't we using ceramics to build? Is it because ceramic failure is difficult to predict? Because it's hard to ...
4
votes
1answer
91 views

Why is there this perforated pipe inside this vertical construction joint in a reinforced concrete wall?

The picture below shows a veritcal construction joint of an approximately 50 years old reinforced concrete industrial structure. The expansion joint was likely originally sealed with a flexcell which ...
2
votes
1answer
38 views

Can aggregate gain almost 200 grams of water when submerged in water for a day?

I'm doing this special project where I have to make concrete using a Martian simulant provided from a commercial source. I measured it as 500 grams initially, then submerged it in water for a day. It ...
2
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0answers
159 views

Why do we use the strain-controlled test for the compressive strength of concrete?

As you all now, a typical stress-strain curve for concrete under compression can be seen in any reinforced concrete design textbook. The decreasing part of the curve (post-peak) can be obtained by ...
4
votes
2answers
67 views

The design of precast concrete— are they the same with cast-in situ design?

I am curious as to how different is precast concrete design than conventional cast-in situ reinforced concrete design as far as structural engineering is concerned. To my mind, they should be the ...
-1
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1answer
40 views

How does Gypsum Concrete work?

When mixed with water how does gypsum act as a binder in creating concrete?
1
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1answer
49 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 ...
1
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0answers
23 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 ...
-1
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1answer
40 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 ...
0
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1answer
64 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 ...
2
votes
2answers
185 views

Concrete Slab Deformation

The concrete slab (?) supporting the swimming pool (≈ 10 x 10m x 1m) of my building has clearly a 'belly': I'm not sure whether this was built this way or evolved over time, however, my best guess is ...
3
votes
3answers
81 views

Design Roller Compacted Concrete Pavement Section

I have been asked to consider using RCC instead of traditional PCC on an upcoming project. For a rough order of magnitude estimate, can I assume that the pavement section design will be similar? I ...
0
votes
2answers
96 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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0answers
30 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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0answers
70 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 ...
0
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1answer
33 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 ...
1
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1answer
53 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 ...
0
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1answer
86 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 ...
1
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0answers
45 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 ...
1
vote
3answers
103 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 ...
0
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2answers
163 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 ...
0
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0answers
22 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 ...
0
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0answers
48 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 ...
1
vote
1answer
134 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 ...
1
vote
2answers
67 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 ...
0
votes
1answer
3k 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 ...
-1
votes
1answer
48 views

International Building Code vs Industry Standards

Which is more reliable. For example, in setting steel posts in the ground, the pole should go under ground 1/3 of its height from the surface up. In IBC, steel post depth is made rather on a storey ...
2
votes
1answer
43 views

How does concrete perform in an Insulated Concrete Form (ICF) house?

From: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4033560/ I can see that concrete can really go bad after a few hundred freeze and unfreeze cycles: If an ICF house has insulation from the inside ...
3
votes
1answer
71 views

How to resolve the interruptions in the screw pump operation due to air trap?

In one of my application, there is a requirement to dispense the concrete paste at the required rate continuously. some technical details of the application given below Dispense rate 5-50 LPM ...
4
votes
1answer
56 views

Can plasticizer leach out of cured concrete?

About 6 months ago I have poured concrete in a plastic mould. The mould was plastic plinth for sun umbrella. It is usually filled with water but it cracked so I filled it with concrete. Before pouring ...
3
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0answers
29 views

Waste Foundry Sand as an aggregate for concrete mixes. I have a question regarding grain diameter and it's possible applications

I'm working on a project with a company that uses sand casts during moulding processes and they provided us with samples of the sand they use before it's involved in the procedure and afterwards (...
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0answers
7 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 ...
2
votes
1answer
166 views

What is the curing process for polymer concrete if it doesn't use any water?

The curing process for regular cement concrete is sprinkling water fog or using a moisture retaining fabric. I was wondering what the process is for polymer concretes because they don't use any water.