Silt Factor


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Joints in concrete 456/IRC 58

Concrete joints are provided to compensate thermal expansion and contraction. The structural separation of concrete members to allow independent movement without damage. They are designed to absorb thermal expansion of concrete. They are commonly provided in bridges, slabs, railways. Bitumen Fibre Board, Dura Board Normally structures exceeding 45 m in length are designed with one or more expansion joints. The pre planned cutting grooves are given in concrete where occurrence of cracks are expected. The depth of groove is 25% of total thickness of the concrete member. Grooves are given in a straight line. These are due to shrinkage or temperature variations. Cutting grooves with blade. Providing glass strips panels not exceeding 3 sqm area in flooring When the work cannot be completed in a single day, construction joints are provided in concrete. These are common in big rafts, beams where joint is provided at L/3 Nito bond, Sika latex,Bitumen Fibre Board, Dura Board
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Penetration Test for Bitumen IS 1203 1978

Hot the Bitumen in oven 90oc + Softening point and pour in in bowl, approx 10 mm more than expacted penetration. Use bowl depth 35 mm, dia 55 mm size for penetrations below 225 Then keep it in room temp for 1 – 11/2 hours (75 min) Then in water bath at temp 25oc for 1 – 11/2 hours (75 min) Use bowl depth 45 mm, dia 75 mm size for penetrations from 225 to 350 Then keep it in air for  11/2 -2 hours (105 min) Then in water bath at temp 25oc for 11/2 -2 hours (105 min) Then place it under the apparatus Wt of assembly should be 100 g (if 50 gm wt + needle + assembly) Wt of assembly should be 200 g (if 150 g wt + needle + assembly) For CRMB 60 penetration will be <50 Penetration ratio = Penetration at 4oc 200 gm for 60 sec ---------------------------------------------- x 100 Penetration at 25oc 100 gm for 5 sec
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Role of FM of sand

The grading and maximum size of aggregates is important parameters in any concrete mix. They affect relative proportions in mix, workability, economy, porosity and shrinkage of concrete etc. Experience has shown that very fine sands or very coarse sands are objectionable – the former is uneconomical, the latter gives harsh unworkable mixes. Thus the object in this paper is to find the best fineness modulus of sand to get the optimum grading of combined aggregate (all-in-aggregate), which is most suitable, and for economy. In general, the grading of aggregates, which do not have a deficiency or excess of any size of aggregate and give a smooth grading curve, produce the most suitable concrete mix. Further a cohesive mix is also desired for the pumped concrete produced by RMC Plant. In the present investigations, effect of the grading of river sand particles has been investigated for a good Concrete mix. Sand has been sorted in three categories i.e. Fine, Medium, and Coarse. These w...
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