Geo-polymer Concrete Development Procedure for the Mix Design of 4th year Project Prepared by Blnd Taib Hora Saman Ibrahim jamil Supervised by Dr. Dillshad Khidir Hamad Amen
Abstract • In view of sustainable development in the construction industry, a new alternative to the ordinary Portland cement concrete has been developed. Geopolymer concrete is a no Portland cement concrete , polymerization will be produced when highly alkaline solution such as sodium hydroxide are incorporated with source materials rich in SiO2 and Al2O3 . such as fly ash.
Literature review • Previous studies on the engineering properties and structural behaviour of Geopolymer concrete have shown promising potential of this material. In this project non-destructive strength evaluation of fly ash based Geopolymer concrete using ultrasonic pulse velocity, rebound number and Pull off tests are investigated.. • Although direct strength tests, which are destructive in nature, are excellent for quality control during construction, their main shortcoming is that the tested specimen may not truly represent the concrete in the actual structure. The destructive tests reflect more the quality of the supplied materials rather than that of the constructed structure
The Non-destructive methods, on the other hand, aim to measure the strength of concrete in the actual structures. This project presents a new approach for the non-destructive evaluation of Geopolymer concrete (GPC) . Nine Cylinders with size of 10 X 20 cm and square slab of size (50 X 50) cm and thickness of 10 cm of geopolymer are prepared in concrete Lab.
. Specimens were tested at different ages using non destructive testing methods (Rebound Hammer , ultrasonic pulse velocity and Pull off tests before measuring the compressive strength. • Results showed good correlation between Non-destructive testing methods with compressive strength of GPC
Historical background • Davidovits has proposed that some of the major pyramids, rather than being blocks of solid limestone hauled into position, are composed of geopolymers, cast in their final positions in the structure. He also considers that roman cement and the small artifacts, previously thought to be stone, of the Tiahuanaco civilisation were made using knowledge of geopolymer techniques.
However, because roman cement forms calcium-silicate-hydrates, and requires calcined limestone as a reactant/precursor, it is more similar to Portland cement than alkali-activated "geopolymer cements" such as Pyrament cement of LoneStar.geopolymer binders and geopolymer cements are generally formed by reaction of an aluminosilicate powder with an alkaline silicate solution at roughly ambient conditions. Metakaolin is a commonly used starting material for laboratory synthesis of geopolymers, and is generated by thermal activation of kaolinite clay.
Geopolymer cements can also be made from natural sources of pozzolanic materials, such as lava or fly ash from coal. Most studies on geopolymer cements have been carried out using natural or industrial waste sources of metakaolin and other aluminosilicates. Industrial and high-tech applications rely on more expansive and sophisticated siliceous raw materials.
Davidovits proposed in 1978 that a single aluminium and silicon-containing compound, most likely geological in origin, could react in a polymerization process with an alkaline solution.
Introduction • Concrete is one of the most common building materials used in the construction of buildings, bridges and infrastructure across the world. Whilst concrete is an excellent construction material it’s manufacture releases a large amount of carbon dioxide (CO2) .
Geo-polymer concrete was introduced by davidovits to reduce environmental pollution that causes by production of Portland cement. • Geo-polymer concrete : is an inorganic material that has been used in a wide range of diverse applications such as heat-resistant ceramics, waste encapsulation and construction products over the past 40 years
it’s a new development in the world of concrete in which cement is totally replaced by pozzolanic materials like fly ash and activated by highly alkaline solutions to act as a binder in the concrete mix.
Recently , alkali –activated binders have been widely studied to be used as a substitute for Portland cement , this is because : • they show great promise as an environmentally friendly binder • have high strength • Stable at high temperature • and have high durability which are similar to those of Portland cement
Aim of the Project In this project we attempt to make a new design procedure for fly ash –based geopolymer concrete, the effect of alkaline solution to fly ash ratio on the compressive strength of concrete cylinder specimens will be investigated , then . The Step by step procedure of the mix design of geopolymer concrete will be explained . The outcome of this study would lay a foundationfor the future use of geopolymer concrete for manufacturing the material in construction work
Benefits of geo-polymer • Geo-polymer concretes offer a number of benefits over conventional OPC concrete including: • significantly lower CO2 emissions than OPC concretes – up to~90% • better thermal insulation properties • higher temperature/fire resistance • providing a viable use for ‘waste’ materials which are often disposed in landfill
Problems • Geo-polymer concrete contains alkali solution • Hard to prepare on site • Set adequate proportion of ingredients • Geo-polymer concrete needs heating not water to give its strength
Application • The applications is same as cement concrete. However, this material has not yet been popularly used for various applications. • This concrete has been used for construction of pavements, retaining walls, water tanks, precast bridge decks.
Application • Structural building Recently world’s first building Structural Building, The University of Queensland’s Global Change Institute (GCI) has been constructed with the use of geopolymer concrete. It is a four storey high building for public use.
Structural materials made with Geo-polymer Watershed Materials, a California based building materials technology startup, has developed a solution to produce high strength masonry with a low carbon footprint using natural mineral based geo-polymers.
airport road : Joseph Davidovits
Mixing procedure of mix designe of geopolyemer concrete As geopolymer does not have any code for mixing designe in this project we made the mix design with ACI 211.4 R for high strength concrete . As geopolymercontains some compounds which is differ from normal cement concrete it react in differetn manner which is called geopolymerization instead of hydration
Geopolymer concrete to form it require reaction between alkalie activator and the fly ash which are used instead of water and cement respectively. • ACI 211.4R in its procedure for mixing designe presents equations and tables which are used as function of water to cement ratios
So we used alkalie activator to cement ratio or AAS/C ratio.
Mix Proportioning Procedure Step-1 : Select slump and required compressive strength. Recoomended values for slump are given in Table-1 Table-1 Recommended slump for concrete with and without Superplasticizer according to ACI 211.4R
Step-2 Select the maximum size of coarse aggregate This step is to select the maximum sizes of coarse aggregate for mixing GPC. Based on strength requirements . The recommended nominal maximum sizes of coarse aggregate are given in Table -2 ACI 318 states the maximum size of an aggregate should not exceed 1/5 of the narrowest dimension between sides of forms 1/3 of the depth of the slab or concrete element ¾ of the minimum clear spacing between individual reinforcing bars Suggested maximum size coarse aggregate
Step-3 : Select Optimum coarse aggregate content – The optimum content of coarse aggregate depends on its strength , potential characteristics and maximum size In Normal strength concrete , the optimum content of coarse aggrgetae depends on the maximum size and fineness modulus of fine aggrgetae . For High strength concrete the recommended coase aggregate expressed as a fraction of the bulk density and as a function of nominal maximum size are given in Table-3 Table-3 Recommended volumes of coarse aggregate per unit volume of concrete
Step-4 : Estimate Alkali activated solution and air content Alkali activated solution considered as the mixing water , The quantity similar to mixing water required to produce a given slump is dependent on many factors including the maximum size ,particle shape and grading of the aggregate , the quantity of fly ash and the type of chemical admixtures used. Table-4 gives estimate of required mixing water (Alkali Activated solution ) for making GGPC
Step-5 Adjustment of the alkaline activator solution (AAS) content due to percentage of voids in fine aggregtae As per ACI 211.4R-93 , a mixture of concrete has been recommended to use the fine aggregate with fineness modulus values from 2.4 to 3.2. However, particle shape and surface texture of the fine aggregate have an effect on its voids content; therefore, mixing water requirements may be different from the values given. As mentioned, the values for the required mixing water given are applicable when the fine aggregate is used that has a void content of 35%. If not, an adjustment of water content must be added into the required water content. Therefore, this study will calculate the AAS content due to percentage of void in the fine aggregate in a similar way to Portland cement concrete. This adjustment can be calculated using the following equation:
Step-6 Selection of AAS to Fly Ash In Table-5 recommended maximum w/cm is given as a function of maximum size of aggregate to achieve different compressive strength at either 28 or 56 day . , Here is total AAS/ Fly Ash will be instead of w/cm ratio Table-5 Recommended maximum w/cm for high strength concrete
Step-7” Calculate of Binder content The weight of the binder required per cubic meter of GPC could be determined by determined by dividing the values of AAS content after the adjustment by Alkali Activated solution to Fly Ash ratio
Step-9 calculation of individual mass of AAS content (NaOH and Na2SiO3 solutions) • In this study, NaOH and Na2SiO3 have been selected as alkaline activator solutions. According to Table 6, the density of NaOH with different concentrations has been used for calculating the volume of AAS as per the volume method. The individual mass of alkaline activator solutions content could be calculated using the following equation: Table-5 composition of Na2 SiO3 and NaOH solutions with different concentrations NaOH (molar) 10M 12M 14M Concentration gm/L400 480 560 Solid 0.40 Water 0.60 • Na2 SiO3 • Solid 0.56 • Water 0.44
The individual mass of alkaline activator solutions content could be calculated using the following equation: Step-10 Calculate Total mass of Solids Total mass of AAS = 165 kg/m3 (NaOH)sol = AAS/(1+1.5) = 165/2.5 = 66 (Na2SiO3)sol = 165-66 = 99 (NaOH)solid = 0.4* 66= 26.4 kg (Na2SiO3) solid = 0.56 * 99 =55.44 Total solid = Fly Ash + (NaOH)solid + (Na2SiO3) solid = 400+26.4+55.44 = 481.84 water from alkaline sol= (NaOH) water + (Na2SiO3)water = Water from alkaline sol = 0.6*66 +0.44*99 = 39.6 +43.56 =83.16 Water / Solid ratio = 83.16/481.84=0.172
Step 11: calculation of coarse aggregates The mass of fine and coarse aggregates content is determined as per the absolute volume method. Let the percentage of the fine aggregate in the total aggregate be 30% and that of the coarse aggregate be 70%. Fine and coarse aggregates content are determined using the following equation: WCA= VCA * Bulk Density of CA Adjusted WCA based on water absorption WCA(adjusted) = WCA (1+ % WA)
Step-12: Calculation of fine aggregate using absolute volume method Af= SG *FA [1000-(VFA -VNaOH -VNa2SiO3-VCA - 10*Air )] Or using mass method Af = (Estimated density – Mass(CA) – Mass(FA) -Mass (AAS) ) The mass of fine and coarse aggregates content is determined as per the absolute volume method. • Step 13: validation of strength attained with the proposed mix design The 28-day compressive strength obtained from testing will be verified with the target strength.
Mix proprtions obtained Mix Fly ash NaoH Na2Sio3 Af CA TotalL (kg) (kg) (kg) (kg) (kg) (kg) 1 312.5 60 90 734.32 1269.76 2466.58 2 357.14 60 90 674.10 1269.76 2451 3 416.67 60 90 607.13 1269.76 2443.56
Eperimental work • Materials • Fly Ash • Low-calcium, Class F (ASTM Standard C618, 2012) dry fly ash obtained from the CHRYSO group, Doha-Qatar, was used as the base material. • The chemical compositions of the fly ash are given in tab.1, ALSE KIMYA MINERAL factory, Eskişehir-Turkey, carried out the chemical analysis.
Alkaline Liquids • The alkaline liquid used is a combination of sodium hydroxide solution (NaOH) and sodium silicate solution (Na2SiO3). The chemical composition of the sodium silicate solution was Na2O=17.98%, SiO2=36.14%, and water 45.88% by mass. • Fine Aggregate • Natural river sand used as fine aggregate, the specific gravity of the sand is 2.69, max aggregate size used is 1.18 mm according to ASTM C778 (ASTM Standard C778, 2013)
Superplasticizer • To improve the workability of the fresh geopolymer binder, Naphthalene-based superplasticizer was used, it complies with ASTM C494, type A and F (ASTM Standard C494/C494M, 2015), it was obtained from Don Construction Products (DCP) company. • Mixture Proportions • Different mixture proportions are selected for the preparation of geopolymer binder mortar specimens of as shown in tab.2, various fly ash contents, alkaline liquid to fly ash ratios, NaOH concentrations, and various Na2SiO3 -to-NaOH solution ratios are considered.
The following ranges were selected for the constituents of the mixtures: • Fly Ash content varied from 400 to 600 in the increment of 50 kg/m3. • Alkaline-to-Fly Ash ratio varied from 0.45 to 0.65, in increment of 0.5 • Mplarity or concentration of Sodium hydroxide varied from 8M to 16 M. • Sodium silicate-to-sodium hydroxide solution ratio varied from 1 to 3 in increment of 0.5.
Manufacturing Process • Preparation of the Alkaline Activator • Water was added to NaOH flakes and mixed then left for about 30-40 minutes to cool down. Then Na2SiO3 solution was added to NaOH solution and mixed properly. The Alkaline activator (NaOH solution+Na2SiO3 solution) was left for 24 hrs. • Mixing • For mixing, an electrically driven mechanical mixer of the type equipped with paddle and mixing bowl, as specified in ASTM C305 (ASTM Standard C305, 2014) was used . • The solid ingredients, fly ash and fine aggregate, were dry mixed for 2 minutes. The alkaline activator, the superplasticizor and the added water were added to the solids, then mixed for another 3 minutes.
Casting • The fresh geopolymer mortar was poured in 50 mm cubes in two layers each layer was compacted by applying 30 manual strokes, and followed by compaction on a vibrating table for about 3 minutes. After casting, the specimens were left for 24 hrs. Prior to curing. • Curing • After 24 hrs. rest period the specimens were placed in an oven for means of dry curing at 80oC.
References https://www.cement.org https://www.irjet.net https://theconstructor.org http://www.era.gov.et http://civilenggseminar.blogspot.com http://geopolymer.weebly.com