Explain these construction engineering terms. 1 Stone core 2 Stone size % passing by weight. 3 Slump test?
Answer:
It's always a good idea to start a question like that with 'please'
As far as I know stone core doesn't mean anything at all.
If you are using crushed stone or pebbles for any purpose,e.g. concrete aggregate,macadam, or road sub-base then the pieces of different size have to be (usually) in certain proportions. Say 100% passing through a 3/4" sieve,40% of that passing through a 1/2" sieve and 5% passing through a 3/8" sieve. These %ages are expressed by weight.
The slump test is a measure of the 'liquidity' of the concrete for want of a better word. If concrete is too dry it won't get into all the tight spots and air bubbles remain, weakening the concrete. The more water in a concrete mix, the weaker the concrete will be. Also it is more likely to shrink when it sets and even for the uniformity of the mix to be lost so there is only coarse aggregate in some places and sand/cement mortar in others. So you use as little water in the mix as possible.
To do the test you fill a standard truncated metal cone with the fresh concrete, lightly compact it and then invert the cone onto a base and carefully lift it off the concrete. Then measure how much shorter the concrete is than the cone. Stiff cioncrete has a slump of up to 1/2 ". Easily workable is up to 2".If the concrete is a puddle on the floor then there is too much water.
I am a bit worried that people who are considering the engineering profession do not even know that you can find out things like this more easily by using a search engine such as Google rather than asking factual questions here!
1) Stone core, if you are refering to concrete then it is the stone or gravel within the mix.
2) Stone size is important to strength, small jagged edged (crushed) stones create stronger mix.
Larger course stones and 'un-crushed' (pebbles) provide less strength as the particles are larger and smoother, but the cement quality also makes a difference and there are many specialist cements, and the amount of water and compaction (removal of airbubbles by vibration).
3) A slump test shows up the 'angle of repose' of a material, normally concrete.
In other words, the amount of internal friction between the particles within.
Think of an egg timer, the sand that flows into the lower chamber will have a point at the top, this is the 'slump', although in construction it is used to determine how much water is in the mixture.
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