Presentation on theme: "SUSTAINABLE SOLUTIONS IN CONCRETE INDUSTRY"— Presentation transcript:
1SUSTAINABLE SOLUTIONS IN CONCRETE INDUSTRY GSAS Sponsored Seminar / WorkshopMEETING TODAY’S DEMANDS BY ADOPTING THE LOW CARBON CONCRETE REVOLUTIONChristopher Stanley, Technical Director, UnibetonQatar National Convention Centre, Doha – Qatar24th May 2014
2What is Sustainability? Producing great structures that lastUsing least possible energy both during construction and remaining service life. Embedded CO2 and operational CO2 need to be consideredEliminating future maintenance costs. 120 year design life can now be extended to 400 years.Leaving a better world to our childrenBetter durability: against chlorides, sulphates, ASR, acid attackBetter colour – high light reflectance
6What is Low Carbon concrete? Low Carbon Concrete is a GREEN concrete. That does not mean concrete that has not yet hardened, or is coloured with green pigment, but in the context of this presentation green concrete is taken to mean environmentally friendly concrete.• This means concrete that uses less energy in its production & produces less carbon dioxide than normal traditional concrete.
7Where does the Carbon Dioxide come from in concrete? The main ingredient in cement is Limestone (Calcium Carbonate CaCO3 )During manufacture the ingredients are heated to about1200oCDuring this process the Carbon Dioxide is driven off :CaCO3 = CaO + CO21kg of cement releases 700gms -1kg of Carbon Dioxide into the atmosphere during its manufacture
8Low Carbon Green concrete Most of CO2 in concrete is from the cement manufacturing process (1 kg of cement produces about 1 kg of CO2 or 5 m3 of CO2)Low Carbon Green concrete makes more effective use of cement giving a reduced carbon footprint and therefore protects the environment.Low carbon green concrete = effective use of cement means better not lower quality
14If some of the cement in the mix was replaced with GGBFS GGBFS (say 70%) = 294 kg x = 32 kg of CO2/m3126 kg of cement x = kg CO2/m3= 32 kg CO2/m kg CO2/m3 = kg CO2/m3REPRESENTING A REDUCTION OF kg CO2/m3
15A 25% replacement of Portland Cement with PFA 25% PFA = 105 kg x 0.06 = 6.3 kg of CO2/m3+ 315 kg of cement x = kg CO2/m3Total of kg, or a saving of kg of CO2 replacing 25% of the cement with PFA
16Low Carbon Green concrete Cement production accounts for 6% of all CO2 emission which is claimed to be one of the factors influencing global warming.In 2013 Qatar was the highest cement consumer per capita in the world.1 Qatar tonnes/year/capita2 UAE tonnes/year/capita3 Kuwait tonnes/year/capita8 Saudi Arabia 1.4 tonnes/year/capita40 Oman below 0.6 tonnes/year/capita
18Optimized Concrete Means Value Engineering Better PerformanceEnhanced cohesion workability, finishability and consistencyReduced shrinkage / creep. Lower compressive strength SDDurability - Increased service life of concreteGreater ValueMinimizes amount of steel neededHigher MOE can allow reduced section thickness weightOptimizes use of available materialsGreenerLEED Contributes to Certification pointsReduced carbon footprintAffordable “green” alternative
27Aggregate proportions affect the properties of concrete The slump of the concrete and its flow are a function of the angle of repose, shape & the quantity of the predominant size of the aggregate in the mix.Use of more fine aggregate, because of the smaller angle of repose, gives higher slump & flow.But the optimum proportions of coarse & fine aggregate are critical to the properties of both fresh & hardened concrete.
28“Particle-Packing Optimization” to meet requirements of plastic and hardened properties”
29Typical spread of an optimized mix – note the aggregate distribution & that it does not bleed
34Heat of hydrationThe heat of hydration of optimized modified concrete is significantly lower than traditional concreteThis results in a lower temperature rise in large concrete pours which is a distinct advantage.The peak temperature rise can be reduced by up to about 14oC.
35A typical 40N optmized mix produces only 27 balloons of CO2 per cubic metre of concrete
36Low Carbon Optimized Green concrete gives value engineering Better performance• Enhanced workability,finishability & consistency• Reduced creep & shrinkage• Increased service lifeGreater value• Minimises amount of reinforcement• Higher Modulus of Elasticity – reduced thickness• Ease of compaction – less labourGreener• Contribution towards LEED Certification points• Upto two ESTIDAMA points in UAE• Reduced Carbon Footprint• Affordable Green construction
41VERY GREEN CONCRETEUnibeton is now developing a technology to make very green concrete, sometimes even without Portland Cement, using a special process. This concrete will produce only about 7 balloons of CO2 per cubic metre. The concrete sets and hardens like Ordinary Portland Cement. It has a one day strength of about 22MPa and 28day strengths of 60 – 75 Mpa can be achieved.
42No-cement concreteBy 2050 global use of cement likely to be 5,000Mt (steel will be 8,000Mt).No-cement concrete could be 1/3rd so 1,666Mt or 4,700Mm3 of cement-free concrete.Highly likely that PFA and other byproduct pozzolans will increasingly make “greener” concrete and reduce embedded CO.
43Our solutionUse a cement replacement (binder) based on the activation of ground granulated blast furnace slag (GGBS) and pulverised fuel ash (PFA) byproducts.Both are widely available and relatively inexpensive.GGBS and PFA must be activated to produce a binder. There are recently invented new types of activators.Resulting binder used in much the same way as Portland Cement without the carbon legacy.
44No Cement Concrete The technical advantages Sets chemically with very low heat of hydrationVast areas poured without joints- increased productivityNo early-age thermal cracking – take out reinforcement30 MPa in 7 days, >50 MPa at 90 days, and >70MPa at 365 daysGreater dimensional stability – low shrinkage and creepResistant to chloride, sulphates and acidsMaintenance-free. Much extended service lifeComplies with performance based standards such as ASTM C1157 Low Heat Concrete category
49Green Pre-stressed Concrete Advantages Cost similar to most concrete used in GCC containing Slag or PFAGreen alternative only 7% of carbon footprint of traditional OPC concreteSignificant Carbon Credits due to reduction of CO2 emissionsTrack record of use in pre-tensioned pre-stressed concrete in USA
50Green Pre-stressed Concrete Advantages Green cement free concrete can currently be produced in strengths ranging from 20MPa to over 75MPaCurrent pre-stressed production normally calls for a concrete strength of 24MPa at the time the tendons are released and with a final strength of in excess of 35MPa.The early strength gain can be adjusted to suit the production process but is normally in the region of 24hr-48hr before tendon release.
59THAT IS EQUIVALENT IN TERMS OF REDUCED CO2 TO: THREE MILLION TONNES OF GGBFS WILL PRODUCE 7.8 MILLION TONNES OF GREEN LOW-CARBON CONCRETE.THAT IS EQUIVALENT IN TERMS OF REDUCED CO2 TO:TAKING 800,000 CARS OFF THE ROAD85,000 SPACE SHUTTLE LAUNCHESSAVING 2.5 MILLION TONNES OF CO2 BY NOT USING PORTLAND CEMENTSAVING CO2 NEEDED TO SUPPLY 3.8 MILLION HOUSES WITH HOT WATER
60Doing more with lessTake out crack control reinforcement (saving up to 30% steel)Reduce binder content using performancebased specifications to achieve C40, C50, C60 … concretesReduce concrete cover by 10mm by Q C measures on site. Use Eurocode 2:1992:1-1; 2004 ClauseSustainability and durability are compatible. We can use the enhanced properties of concrete to avoid over-design
61Environmental advantages Reduced energy consumptionReduced CO2 emissionsDiversion of industrial by-products from landfillingLower water consumptionReduced steel use
62Recently finished 10,000 sq ft (1,000 sqm) warehouse – Cambridge, Laid in one day with no joints.
63Large Scale Field Trials This large scale field trial was conducted for Crossrail in East London. It marked the first occasion that No Cement Concrete concrete was pumped.
64FOR EVERY m3 OF NO CEMENT CONCRETE, 281 KG OF EMBEDDED CO2 ARE REDUCED THE EMPIRE STATE BUILDING WAS CONSTRUCTED FROM 47,400 m3 OF CONRETE. IF IT HAD BEEN CONSTRUCTED FROM NO CEMENT CONCRETE = A SAVING OF 13,319 TONNES OF CO2IT TAKES 1.87 TONNES OF CO2 TO FLY ONE PASSENGER FROM LONDON TO QATAR OR 7000 RETURN FLIGHTS FROM LONDON TO QATAR WOULD BE THE SAVINGS IN CO2 BY BUILDING THE EMPIRE STATE BUILDING IN CEMENT FREE CONCRETE RATHER THAN TRADITIONAL CONCRETE.
65Advantages of using No Cement Concrete Substantially reduced CO2 emissions and energy use in the construction sectorUtilisation of by-products which would be otherwise land filled (certain geographical locations, India, China etc;)Improved durability because:Much decreased capillary porosity (prevents ingress of aggressive chemicals, including chlorides, acids and sulphates, into concrete)Much denser cement-aggregate interface (reduces permeability)Much better bond to steel reinforcement