Skip to main content

Dry Lean Concrete (DLC) Methodology, specifications ,joint formation and construction procedure as per MORTH and Indian standard

  DRY LEAN CONCRETE

Scope-
DLC acts as a sub-base for the cement concrete pavements or pavement quality concrete (PQC) .DLC material has no slump i.e. zero slump.
The design parameters  of DLC viz. Width, thickness, grades of concrete, details of joins is given in the drawings.



Material- 

1 - Sources of Material 

The contractor shall indicate to the engineer the source of all material with relevant test data to be used in the dry lean concrete (DLC)  work sufficiently in advance and approval of the engineer for same shall be obtained at least 45 days for the scheduled commencement of the work in the trial length. Contractor can take approval of different source of material with relevant test data at least 45 days in advance to use the material by the engineer during the execution of main work.

2 - Cement

Any of the following type of cement may be used with prior approval of the engineer.


If the subgrade soil contains soluble sulphates in a concentration more than 0.5%, sulphate resistant cement conforming to IS:6909 shall be used.



3 - Fly-ash
Fly-ash up-to 20% by weight of cementitious material (cement + fly-ash) may be used along with 43/53 grade cement  may be used to replace Ordinary Portland cement (OPC)  cement grade 43 up-to 30% by weight of cement.Fly-ash shall conform to IS:3812(part 1).


4- Aggregate
Aggregate for lean concrete shall be natural material complying with IS:383. Aggregate shall not be alkali reactive.In case engineer consider that the aggregates are not free form dirt, the same may be washed and drained for at least 72 hours before batching, or as directed by the engineer.


A-Coarse aggregate
 Coarse aggregate shall Consist of clean, hard, dense, strong, durable and  non-porous pieces of crushed stone and crushed gravel and shall be devoid of pieces of disintegrated stone, soft flaky, elongated, very angular, splintery pieces.The Max.  size of aggregate is 26.5 for pavement concrete. No aggregate which has water absorption more than 2% shall be used in concrete mix.  The aggregate shall be tested for soundness in accordance with IS:2386(part-5).After 5 cycle of testing , the loss shall not be more than 12% , If sodium sulphate solution is used , 18% If magnesium sulphate solution is used.The combined flakiness index and elongation index of aggregate  shall not be more than 35% and the Los Angeles abrasion value shall also not be exceed 35.
The aggregate gradation shall comply with Table 600-1 given below..


         
B-Fine aggregate 

The fine aggregate shall consist of clean natural sand and crushed stone sand or a combination of the two and shall conform to IS :383. Fine  aggregate shall be free from soft particles, clay ,shale, loam, cemented particles ,mica and organic and other foreign  matter. The fine aggregate shall have a sand equivalent value of not less than50 when tested in accordance with the requirement of IS:2720 (part 37).

5- Water 
     Water used for mixing and curing shall be clean and free from injurious amounts of oils,  acids, alkalis,  salts,  sugar, organic materials or other substances that may be deleterious to concrete or steel.


Potable water is generally considered satisfactory for mixing concrete. Water found satisfactory for mixing is also suitable for curing of concrete.

The PH value of water shall not be less than 6.

Sea water is not allowed due to presence of harmful salts. Under unavoidable circumstances sea water may be used for mixing or curing in plane concrete not in embedded steel.

Proportioning of the material for the mix

 The mix shall he proportioned with a maximum aggregate cementitious material ratio 15:1.

A- Moisture Content 

The optimum water content shall be determined and demonstrated by rolling during trail length construction and the optimum moisture content and degree of compaction shall be got approved by the engineer. While laying in main work, the lean concrete shall have a moisture content between the optimum and optimum +2 percent, keeping in view the compaction and compensate evaporation losses.

B- Cement Content 
Cement content in DLC shall be such that the strength specified in concrete strength( Next point) is achieved.The minimum cement content shall be 150 kg/cu.m of concrete. In case flyash is blended at site as part replacement of cement, the quantity of flyash shall not be more than 20% by weight of cementitious material and the content of OPC( Ordinary Portland Cement) shall not be less than 120 kg/cu.m.

If this (above described)  minimum  is not sufficient to produce DLC of the specified strength, it shall be increased by the contractor at his own cost.

C - Concrete  Strength 
The average compressive strength of each consecutive group of 5 cubes shall not be less than 10 MPa at 7 days. In addition,  the minimum compressive strength of each cube shall not be less than 7.5 MPa at 7 days. The design mix shall be got approved from the engineer and demonstrated in the trail length construction.


Construction of DLC Layer ( Construction Procedure) 

The DLC shall be laid on the prepared granular drainage layer. The dry lean concrete (DLC)  sub-base shall be over laid with concrete pavement (viz.  Pavement quality Concrete (PQC)) only after 7 days of sub base construction.

A- Batching and Mixing 

B- Transporting 
Plant mix lean concrete shall be transported in tipping trucks at the required point and discharged immediately. Protection from weather is done by covering the tipping trucks with tarpaulin during transit. Each tipping truck shall be washed with water jet before next loading.

C- Placing
Lean concrete shall be placed by a paver with electronic sensor on the drainage layer or as specified in the contract.
DLC material shall be laid in one layer in even manner without segregation with suitable equipments.
The paver machine shall have high amplitude tamping bars to give good initial compaction to the sub-base. One day before placing of the DLC sub base, the  surface of the granular sub base /drainage layer shall be given a fine spray of water and rolled with smooth wheeled roller.
Preferably the lean concrete shall be placed and compacted across the full width of the two lane carriage way by constructing it one go.
 In roads with carriage way more than 2 lanes a longitudinal joint shall be provided.Transverse butt type joint shall be provided at the end of the construction in a day.
The DLC shall be laid in such way that it is atleast 750 mm wider on each side than the proposed width including paved shoulder of the concrete pavement.

D- Compaction
The  shall be carried out immediate after the material is laid and levelled.Rolling shall be continued on the full width till there is no further visible movement under the roller and the surface is well closed.
The minimum dry density obtained shall not be less than 98% of that achieved during the trail length construction (of max dry density).  The density achieved at the edge I.e. 0.5 meter from the edge shall not be less than 96%  of the that achieved during the trail length construction (of max dry density).
The spreading,compacting and finishing of the lean concrete shall be carried out as soon as possible and time between the mixing of first batch of concrete in any transverse section of the layer and the final finishing of the same shall not exceed 90 minutes when the temperature of concrete is between 25°C and 30°C, and 120 minutes if less than 25°C.This period may be reviewed by the Engineer in the light of the results of the trial run but in no case shall it exceed 120 minutes. Work shall not proceed when the temperature of the concrete exceeds 30°C. If necessary, chilled water or addition of ice may be resorted to for bringing down the temperature. It is desirable to stop concreting when the ambient temperature is above 35°C. After compaction has been completed, roller shall not stand on the compacted surface for the duration of the curing period except during commencement of next day's work near the location where work was terminated the previous day.
Double drum smooth-wheeled vibratory rollers of minimum 80 to 100 kN static weight are suitable for rolling dry lean concrete.
The number of passes required to obtain maximum compaction depends on the thickness of the drylean concrete.
Except on super elevated portions where rolling shall proceed from the inner edge to the outer, rolling shall begin from the edges gradually progressing towards the centre. First, the edge/edges shall be compacted with a roller running forward and backward. The roller shall then move inward parallel to the centerline of the road, in successive passes uniformly lapping preceding tracks by at least one half width. A preliminary pass without vibration to bed the Dry Lean Concrete down shall be given followed by the required number of passes to achieve the desired density and, a final pass without vibration to remove roller with vibration marks and to smoothen the surface.
For repairing honeycombed/hungry surface, concrete with aggregates of size 10 mm and below shall be spread and compacted as per Specifications.Any level/thickness deficiency shall be corrected after applying concrete with aggregates of size 10 mm and below after roughening the surface. Surface regularity also shall be checked with 3 m straight edge. 


Joints 

Joints Construction and longitudinal joints shall be provided as per the drawings.
Transverse butt type joint shall be provided at the end of the construction in a day. Longitudinal construction joint shall be provided only when full width paving is not possible. Transverse joints in Dry Lean concrete shall be staggered from the construction butt type joint in Concrete pavement by 800-1000 mm. 
Longitudinal joint in Dry Lean Concrete shall be staggered by 300-400 mm from the longitudinal joint of concrete pavement. 

Curing 

As soon as the lean concrete surface is compacted, curing shall commence. One of the following methods shall be adopted:

a) Curing may be done by covering the surface by gunny bags/hessian, which shall be kept wet continuously for 7 days by sprinkling water.

b) The curing shall be done by spraying with approved resin based aluminized reflective curing compound conforming to ASTM-C 309-81. As soon as the curing compound has lost its tackiness, the surface shall be covered with wet hessian for 3 days. The rate of application shall be as recommended by the supplier.

c) Wax-based white pigmented curing compound with water retention index of not less than 90 percent shall be used to cure the dry lean concrete. The curing compound shall conform to BS:7542. The compound shall be applied uniformly with a mechanical sprayer and with a hood to protect the spray from the wind. The curing compound shall be applied over the entire exposed surface of the Dry Lean Concrete, including sides and edges, at the rate of 0.2 litres/sq.m, or as recommended by the supplier.

Measurement for Payment

The unit of measurement for dry lean concrete pavement shall be in cubic metre of concrete placed, based on the net plan area for the accepted thickness shown on the drawings or as directed by the Engineer.

Thanks a lot
Mukesh Kumar (Gyan of engineering) 

Comments

  1. Mostly I do not comment on any post, but your blog has lots of knowledge. it's forcing me to do this. it has really amazing content please share more information with us.Commercial Asphalt

    ReplyDelete

Post a comment

Popular posts from this blog

Granular Sub base (GSB) specifications, GSB Grading, layer thickness, Water absorption, Physical requirements (like liquid limit, Plasticity index ,AIV), construction procedure or Rolling , measurement and treatment of GSB as per MORTH 5th revision and Indian standard in Civil engineering

Granular sub-base (GSB) SUB BASE (GSB)– The full form of GSB is granular sub base.it is being laid in road work because it plays two major roles 1- it works as  drainage layer 2- it provides a good sub base to laid base layer on it. How to calculate the quantity, compaction factor value and loose thickness of GSB? To know more information kindly visit on below link 🔗  www.gyanofcivilengineering.com/granular sub-base(GSB) Quantity. Material –     The material to be used for the work shall be natural sand, crushed   gravel, crushed stone, crushed slag, or combination thereof depending upon the grading required use of material like brick metal, kankar and crushed concrete shall be permitted in the lower sub base. The material shall be free from organic or other deleterious constituents. Grading III and IV shall be used in lower sub base. Grading V and VI shall be used as sub-base-cum-drainage layer. Where the sub-base is laid in two layers as upper sub-base and lowe

Wet Mix Macadam (WMM) technical specifications as per MORTH and Indian standard in Civil engineering

WET MIX MACADAM (WMM) sub – base /base:- Wet mix macadam (WMM) act as a base course just below the bituminous layer (bitumen base course or surface course).  The thickness of a single compacted Wet mix macadam(WMM)  layer shall not be less than 75mm.when vibrating or other approved types of compacting equipment are used, the compacted depth of a single layer of the sub-base course may be up to 200mm. How to calculate the loose thickness of WMM, compaction factor and quantity of WMM ? Kindly visit on below link 🔗 https://www.gyanofcivilengineering.com/2020/05/wet-mix-macadam-wmm-quantity-compaction.html Physical requirements   Material finer than 425 micron shall have plasticity index (PI) not exceeding 6. To determine this combined portion, the flaky stone from a representative sample should first be separated out. Flakiness index is weight of flaky stone metal divided by weight of stone sample. Only the elongated particles are separated out from

Full form of various terms used in civil engineering /highway engineering or road work

Full Form of various  terms used in civil engineering  (Highway and expressway)  List of various  acronyms or abbreviations used in civil engineering  TBM- Temporary Bench mark (टे᠎म्‌प्‌ररि बेंच मार्क) BM- Bench Mark ( बेंच मार्क ) / Bituminous Macadam ( बिटुमिनस मैकडम) MSL- Mean Sea Level (मीन सी लेवल) BS- Back sight( बैक साइट) FS - Fore sight  (फोर साइट) HI - Height of Instrument ( हाइट आंफ इन्‌स्‍ट्रमन्‍ट्‌) TS-  Total Station (टोटल स्टेशन) GPS- Global Positioning System (ग्लोबल पोजिशनिंग सिस्टम) ROW- Right of Way (राइट ऑफ वे) MTV- material Transport vehicle (मटेरियल ट्रांसपोर्ट वहीकल) NGL- Natural Ground Level (नेचुरल ग्राउन्‍ड्‌ लेवल ) OGL- Original Ground level (अˈरिजन्‌ल्‌ ग्राउन्‍ड्‌ लेवल ) C&G- Clearing and Grubbing ( क्लियरिंग और ग्रबिंग) EMB- Embankment SG- Subgrade (सबग्रेड) GSB- Granular sub-base WMM- Wet Mix Macadam ( वेट मिक्स मैकडैम) WBM- Water Bound Macadam (वाटर बाउंड मैकडैम) DBM- Dense Bituminous Macadam SDBM- Semi- Dense Bitumino

WMM(Wet Mix Macadam) quantity / Compaction Factor value for WMM / Loose thickness of WMM Layer

Wet Mix Macadam (WMM) quantity / Compaction Factor value for WMM / Loose thickness of WMM Layer  In this article we shall discuss three important points about wet Mix Macadam (WMM) 1- How can we calculate the required WMM  quantity?  2 -  What is value of compaction factor for WMM? 3- How much loose thickness should be taken to get proper compacted layer thickness ?  1- How can we calculate the required WMM quantity? Let us consider Length of WMM Bed(L) = 1 Km = 1000 Met. Breadth of WMM Bed(B)= 7 Met. Thickness of WMM Layer (T)  = 150 mm =0.150 Met. Max. Dry Density (MDD) =2.230 Gram/ Cubic Centimeter = 2230KG/ Cubic metre Note -  The value of MDD is calculated by conducting proctor density test as per IS 2720 (part -28) : 1983 (Reaffirmed - May 2015). Then Volume of WMM Layer = ( Length of WMM Bed X Width of WMM Bed X Thickness of WMM Layer) Volume of WMM Layer = L X B X T  Volume of WMM Layer   = 1000 X 7 X 0.150  Volume of WMM Layer    = 1050 C

Dense Bituminous Macadam (DBM) or Bituminous Concrete (BC) layer Quantity / Compaction Factor value / Loose thickness calculation

Dense Bituminous  Macadam (DBM) or   Bituminous Concrete (BC)  quantity / Compaction Factor value for DBM or BC / Loose thickness of DBM or BC Layer  In this article we shall discuss three important points about Dense Bituminous   Macadam (DBM) or Bituminous Concrete (BC) 1- How can we calculate the required DBM/BC quantity?  2 -  What is value of compaction factor for DBM/BC? 3- How much loose thickness should be taken to get proper compacted layer thickness ?  1- How can we calculate the required DBM/BC quantity? Let us consider Length of  DBM/BC layer (L) = 1 Km = 1000 Met. Breadth of DBM/BC Layer (B)= 5 Met. Thickness of DBM/BC Layer (T)  = 50 mm =0.050 Met. Max. Dry Density (MDD) =2.441 Gram/ Cubic Centimeter = 2441KG/ Cubic metre Note  -  The value of MDD is calculated by conducting suitable test . Then Volume of DBM/BC Layer = ( Length of DBM/BC layer X Width of DBM/BC layer  X Thickness of DBM/BC Layer) Volume of DBM/BC Layer = L X B X T Volume o

DBM (Dense Bituminous Macadam) specificatins,layer thickness, physical requirements, aggregate size, grades and its measurements

 DENSE BITUMINOUS MACADAM(DBM) DBM acts as a bituminous  base course and thickness of a single compacted  layer shall be 50 mm to 100 mm.  In this article we shall discuss about Technical specifications of DBM (Dense Bituminous Macadam), layer thickness, physical requirements, aggregate size, grades and its measurements A-Scope : The work shall consist of construction in a single layer of DBM on a previously prepared base or sub-base. The thickness of a single layer shall be 50 mm to 100 mm. B - Material : The choice of binder material shall be stipulated in the contract or by the engineer, where viscosity grades of bitumen are specified, they are referred to by a designation in accordance with IS: 73. Where modified bitumen is specified, it shall conform to the requirements of IRC:SP:53 and IS:15462. Selection criteria for viscosity grade bitumen based on highest and lowest daily mean temperatures at a particular site are ]given in table no -1. 1-Coarse Agg

Difference between nominal mix and design mix of concrete

Difference between nominal mix and design mix of concrete - Concrete is most extensively used mix to achieve desired properties of structure. There are two methods to prepare the concrete mix. 1-Nominal mix 2- Design mix Nominal mix - Nominal mix specifies the fix proportion of the cement , sand and aggregates. Ingredients of concrete are mixed on the basis of volume. It is a site level mixing of ingredients to prepare concrete mix. Such type of concrete mix is generally used in small quantity or where load is not high. There are many grade of nominal mix concrete like M-5, M-7.5, M-10, M-15 and M-20. In above grades of concrete mix  the letter 'M' refers to Mix where as the value like 5,7.5,10,15 etc indicates the compressive characteristic strength of concrete after 28 days in specified conditios. Unit of this compressive characteristic strength of concrete is  Newton /mm 2. The ratio of various grade of concrete is being given below - M-5 

Bituminous Concrete (BC) specifications viz. Layer thickness, Mix and material requirements, grading , laying trials, Rolling , Construction procedure, transport and joint specifications, surface finish and quality control,measurement and rate etc..as per MORTH and Indian Standard

Bituminous concrete(BC)- Bituminous concrete( BC) is used for wearing  course and profile corrective courses.BC is generally laid in single layer on a previously prepared bituminous bound  surface. The thickness of single layer of BC shall be 30mm,40mm and 50mm. 1 -MATERIAL A- Bitumen - The bitumen shall be viscosity graded paving bitumin complying with IS 73 or specified in contract aggrement. The type and grade of bitumen to be used would depend upon the climatic condition and the traffic. Selection criteria of viscosity graded (VG) paving bitumens based on climatic conditions B- Coarse Aggregate It consist of crushed rock,crushed gravel or other hard material retained on 2.36 mm sieve. It shall be clean ,hard,durable and of cubical shape,free from dust,and  soft organic and other deleterious substances. The aggregates  shall satisfy the physical requirements of table  no. -2 (Table no. 500-16 ,as per MORTH 5th revision) where crushed gravel is proposed 

Civil engineering interview questions in Roadway/Highway /Expressway department

  Welcome friends, We shall learn about the various questions which are frequently ask by an  interviewer In the field of infrastructure.  So let's get start....... EMBANKMENT/SUBGRADE/BORROW AREA •Liquid Limit  <50% •Plastic Limit  < 25% •Proctor Density(Min. Value) For Embankment =1.52 to 1.60 gram/cubic centimeter For Subgrade= 1.75 gram/ cubic centimeter Sub-grade top • Field Dry Density (FDD) For Embankment= min. 95% For Sub grade = min. 97% •Number of test For Embankment = 1set/3000 sq.meter(1set=10pits) For subgrade= 1set/2000 sq.meter (1 set=10 pits) GRANULAR SUB- BASE •Maximum thickness of single compacted layer = 200 mm • Minimum thickness of single compacted layer( only when GSB is laying in two layers) = 150 mm •Max. Allowable size of aggregate =75mm •Number of grading of GSB = 6 •Liquid limit  should not be  more than 25% ( test procedure as per IS 2720 (part 5)). •Plasticity index should  not be more than 6%

Process of laying of DBM/ BC( weather limitations, Rolling of laid material and cleaning of bed)

First of all i want to tell you that DBM act as bituminous base course while BC acts as wearing course. LAYING OF DBM(Dense Bituminous macadam) /BC(Bituminous concrete)  Laying of DBM/BC is done with the help of paver. There are following points which clearly indicates detailed process of laying. To know more about the bituminous concrete (BC) ,please click on below link......... https://gyanofcivilengineering.com/2020/05/bituminous-concrete-bc-specifications.html 1-Weather and seasonal limitations- Laying shall be suspended: A- In presence of standing water on the surface B-When rain is imminent, and during rain, fog, or dust storm C-When the base/binder course is damp D-When the air temperature on the surface on which it is to be laid is less than 10°C for mixes with conventional bitumen and is less than 15°C for mixes with modified bitumen E- When the wind speed at any temperature exceed the 40 km per hour at 2 m height. 2-Cleaning of surface- The