Affordable Technology for Rural concrete roads   

Dr.V.V.Deshmukh

(A white paper on affordable technology for rural concrete roads

Rural roads mostly bituminous roads are in bad shape because of severe climatic conditions in our country. Funds for maintenance are not available resulting very bad condition of road in our country. The concrete roads are recommended for our country because no severe climatic condition affect the performance of concrete roads.

The main constrain is the cost .There is general perception of the construction fraternity the concrete is very costly. The old pundits of the pavement industry are familiar with asphalt pavement because last five decades the asphalt roads are made over concrete. People are not aware of significant development in concrete admixture. and its effect on strength and performance. It is possible to produce concrete at much cheaper rate

According to Mr.P.Bongirwar out of 33lack km of length only 2lakh kilometre carry heavy traffic from 30MSA to 200 MSA and only about  50000 kilometre may be carrying more than 100 MSA. Majority of village roads and ODR of about 28 lack kilometre must be carrying traffic less then 3MSA.Considering the  present road construction activity the same will need 175 cubic meter of aggregate every year which is creating environmental issue .Large requiring of sand also creating problem of underground water. Heavy consumption of diesel and bitumen is increasing our burden of foreign exchange .Most of the village roads are seriously affected due to inadequate provision of maintenance grands.

omt 90% length is metalled and top WBM layer is seriously affected and not in traffic worthy condition .The black topped village roads are also heavily damaged due to lack of renewal coat. Huge funding is required to revive these assets to proper standards .we therefore plan such specifications and develop technology which can result into more durable assets at minimum affordable cost. All low volume road is usually provided with thin bituminous surfacing which require constant maintenance of potholes formed during rains. The road also require major renewals such as bituminous carpet and seal coat after every five years. if there is water logging due to lack of drainage the bituminous surface may get damp within a week of construction and entire investment is lost in a short time There is need for suitable pavement material having expected life of 15 to 20 years which is low in initial and maintenance cost not affected by water labour intensive and employment generation and dust free environment.

The author has categorised the village roads as roads villages turning cities and village roads.

The city roads The traffic of the city road is of cars ,rickshaws, buses, trucks  etc. The axle load is of 10MSA.The thickness of the road is 100mm based on IRC -78. The optimum mix design is given below. 

Historical development in urban pavement technology at TMC

MIX DESIGN FOR WHITE TOPPING AS OVERLAY

 for TMC CORPORATION

MATERIAL	kg/M3	RS/KG	COST	DENSITY	VOLUME
cement	360	6.00	2160	3.15	114.29
flyash	150	2	300	2.25	66.67
micro silica	0	22	0
sand	917	0.6	550.2	2.69	340.89
metal-2	450	0.6	270	2.88	156.25
metal-1	550	0.6	330	2.88	190.97
admix	3	140	420	1.23	2.44
water	160	0.4	64	1	160.00
fiber	0	225	0		1031.51
	2590		4094.2

COMPRESSIVE STRENGTH		7-DAYS	25mpa
		28-days	40mpa
	510.00
water/powder	0.88	88
past content	0.33	36
sand content	0.33048015	35
coarse aggregate	0.33661683	28

.THIN WHITE TOPPING IS GRDUALLY BECOMING POPULAR IN URBAN AREAS The author has developed the above mix design and first time laid 100meter stretch of white topping in thane city in the year 2008.The project was successful and 25 kilometre white topping is done in thane city .The methodology is given below. The life cycle study certainly prove that white topping is cheaper than conventional bituminous roads

FIG1 Milling of existing bituminous road

FIG2 Sub base preparation

Fig3 concrete laying

FIG4 UTWT Topping

Historical development in rural pavement technology at Murbad Thane

The Thane unit of PMGSY made history by adopting /experimenting technology which is different than regular prescribed method of Road building

In the month of April 2011 thane unit of PMGSY  was successful in laying 150 mm of PQC on 150mm of GSB The concrete used was totally different than conventional concrete.

1.      The M-40 Grade concrete is made by using 290kg of cement. The reduction in cement quantity was possible by using additives like flyash,silica fume,GGBS etc. and by using water reducing admixture  like BASF Glenium sky, Glenium 276 etc.

2.      The SCC technology is used to achieve concrete to spread of its own weight.

3.      First time the joint cutting is avoided by placing geopolymer strips of 50mm in 150mm concrete at regular interval.

Three fundamental changes in concrete technology made it possible to give concrete roads to villages  in slightly higher cost.

The white topping has made distinct difference in the output.

1 Maintenance free roads for next fifteen years

2  Acceleration of rural economy.

3 Saving in raw material namely lime stone by less use of cement .

Few photographs of concrete road at kunde bangar wadi under the scheme of prime minister of gram Sadak yogna

Mix design for PMGSY

SCC concrete

MATERIAL	kg/M3	RS/KG	COST	DENSITY	VOLUME
cement	290	5.40	1566	3.1	93.55
flyash	200	1.8	360	2.25	88.89
sand	355	0.6	213	2.69	131.97
crush stone	355	0.75	266.25	2.88	123.26
metal-2	536	0.6	321.6	2.88	186.11
metal-1	630	0.6	378	2.88	218.75
admix-BASF-B-276	3	140	420	1.23	2.44
water	150	0.4	60	1	150.00
					994.97
	2519		3584.85

slump flow	400mm
ycone	8sec
water/cementitious	0.306122

Gradation for crush stone and sand

	%PASSING
10MM	100
4.75MM	90-100
2.36MM	60-95
1.18MM	30-70
600MICRON	15-34
300MICRON	5_20
150MICRON	0-10

Gradation for metal i&ii

Gradation for metal i&ii	metal ii	metali
	%passing
20mm	95-100	100
16mm
12.5mm		90-100
10mm	25-55	40-85
4.75mm	0-10	0-10

Flyash should be from field 3 residue on 45 micron is 10%

A trail stretch of about 900m with above technology has been done for a project near kalyan Feasibility and cost advantage has been proved beyond doubt.

Historical work carried out in Bhangarwadi village near kalyan.is given below

            FIG1 Mixer for making concrete,FIG2 Laying of channelFIG3 Placing of concreteFIG4Authorities inspecting the roadFIG5Ready to use road

For village roads normally crust consist of 300mm sub grade ,200mm GSB,150-

to 225 mm WMM  20MM carpet and seal coat. Carpet and seal coat does not add to strength. but act as dust proof course .it also prevents the sucking of blindage from WMM due to pneumatic tyre and thereby prevents the damage to WMM/WBM surface. Most of the village roads are metal led and for the want of maintenance grand top later is worn out. Almost top  75mm to 100mm WBM/WMM Layer is heavily damaged in such cases normally additional 75mm to  100mm WBM/WMM layer is added and road is restored to proper cmber.20mm carpet and seal coat is added as wearing course

As an alternate to above the levelling course itself could be converted in to white topping layer the structure could be on line of white topping technology.

The WBM of hand broken material/crushed aggregates of proper gradation are laid it will  then be rolled and compactedThe entire surface then will be grouted with specially designed flow table grout and compacted again.

Rate analysis  of technology similar to coalcrete

length	1000	m
breadth	3	m
thick	0.05	m

volume m3	150
voids%	30
total voids m3	45
grout quality	%	m3	kg	ton	cost/ton	cost in Rs
cement	20	8.955224	19701.49	19.70149	5600	110328.4
aggrgate	70	31.34328	68955.22	68.95522	700	48268.66
flyash	10	4.477612	9850.746	9.850746	1800	17731.34
admix	0.5	0.223881	1100	1.1	150000	165000
sf	0	0	0	0	28000	0
					total	341328.4

grout density	2200kg/m3
						cost in Rs
aggregate in tons	211.5	211500
aggregate cost		211500				211500
						552828.4
box making with geopolymer						50000
labour and machinery						110565.7
tax						27641.42
profit 20%						110565.7
						851601.1
				m3		5677.341
				sq.meter		283.867

 FIG1Mixing of fine powder materials,FIG2 Spreading of hand broken stones across the damaged road,FIG3 Grout prererationFIG4 Pouring the groutFIG5Final road

 The cementitious grouts

The high quality cheaper grouts are prepared. In order to keep the cost of the grout competitive additives like flyash, GGBS are used in large proportion. In order to keep the grout in suspension polymer based admixture is used..the pore volume is adjusted using lower size stone.

Few compositions of high strength cementitious grouts are given below

	Compressive strength test results of grouts with Tata flyash
CEMENT	55	55	45	45
TFA	40	45	55	50
SF	5			5
ADDITIVE	0.5	0.5	0.5	0.5
WATER	20.6	20.3	18.3	18.6
STRENGTH Kg/Cm2)
1-Day	244	208	102	165
3-Day	728	755	599	543
7-Day	753	879	760	672
28-Days	Results awaited

The grout using TATA flyash can achieve compressive strength of 100Mpa.

Comparison of modified grouts compositions with normal grout using SF

composition	Gr-II	50cement	35cement	30cement	45cement
		50pozo	65pozo	70pozo	30pozo
					30Dahanu
comp.strength
1-Day	199	293	189	133	134
3-Days	433	436	300	248	316
7-Days	528	526	450	430	480
28-Days	633

Pozocrete micronized flyash can replace costly silicafume

Trials conducted using slag cement

Slag cement	55		60		65
flyash	40		35		30
SF	5		5		5
Additive	0.5		0.5		0.5
water	27		26		25
Compressive strength(kg/cm2)
1-Day	54	85		114
3-Days	185	233		321
7-Days	275	330		522
28-Days	530	650		710

Preparation of base for roads;

The damaged bituminous roads are cleaned and milled using milling machine. The 50mm thick of 30mm stone are laid on the damaged bituminous roads. rolled with vibratory roller and the high strength grout is poured in to the pores of the aggregate bed.

The 30mm aggregates are even prepared from the rock at site by hand braking.This will provide employment to rural youth.

The high quality cheaper grouts are poured into the 30mm stone laid on the damaged roads. rolled with vibratory roller and the grout is penetrated into the pores of the bed

The compressive and flexural strength of such roads tested inlab is found to be 40Mpa and 4.25Mpa respectively

It is observed that during the testing of compressive strength at some occassion the aggregates were fractured keeping the matrix strong.

Cost of the grout is Rs 4/kg which can be further reduced by at least one rupee by having dialog with admixture manufacturers.

The grout composition

material	Gr-1	Gr-2
cement	55	45
flyash	45	55
admixture	0.5	0.5
water	30	30

The cost of square meter road.

The cost of the road is approximately Rupees 350  per meter square.

The technology is rural friendly it requires only blender for grout preparation and pump to deliver the grout at site. Unskilled labour to brake the stone and labour to pour the grout. The cost can further be reduced.

IN THIS TECHNOLOGY THE 40MM STONE ACT AS  SOLD PLASTIC CELL .AND THE GROUT RESTRICTS THE BOUNDRIES.

WE CAN SAVE THE ADDITIONAL COST OF PLASTIC CELL.

Conclusion

1)      Affordable technologies are readily available  to use

2)      The citizen of India should examine these technologies