S-401 Project sheet · M.Tech thesis

One-part geopolymer concrete

Experimental investigation + finite element analysis

A cement-free concrete made from fly ash, GGBS and a solid activator that needs only water at the mixer. Four trial mixes were cast and tested in the lab, the best one was picked on workability and strength, and its measured properties were carried into ABAQUS to analyse a reinforced beam under load.

M.Tech Structural Engineering Vel Tech University, Chennai Guide · Dr. A. Chithambar Ganesh Viva May 2026

Full report (PDF) Back to résumé

Compressive · 28 d45.8 MPaOptimum mix, cube test

Flexural · 28 d6.3 MPaPrism modulus of rupture

Cement replaced100 %Binder is 10% fly ash + 90% GGBS

FE beam · 15 kN4.1 mmMidspan deflection, CDP model

Why it matters. Cement production is one of the largest single industrial sources of CO₂. Geopolymer binders replace Portland cement with industrial by-products, but the usual two-part system needs corrosive liquid activators on site. The one-part, or "just add water", system mixes dry precursors with a solid activator so it can be batched like ordinary concrete.

Objectives. Develop a one-part geopolymer concrete from fly ash, GGBS and sodium metasilicate. Cast four trial mixes and compare fresh behaviour (slump, compaction factor, Vee-Bee) and hardened behaviour (compressive, split tensile, flexural). Select the best mix and transfer its properties into a Concrete Damage Plasticity model in ABAQUS to study a reinforced beam.

MaterialsFly ash, GGBS, solid Na₂SiO₃ activator, M-sand, 20 mm aggregate

Four mixesVary fly ash : GGBS ratio and activator dose; ambient curing

Fresh testsSlump, compaction factor and Vee-Bee on each mix

Strength28-day cube, cylinder and prism tests; pick the optimum

ABAQUS230 × 300 × 1000 mm RC beam, CDP model, midspan load

S-402 Materials & mix design

What went into it

Every constituent was characterised against the relevant Indian Standard before mixing. Binder content was held at 500 kg/m³ and water at 175 kg/m³ so that only the fly ash : GGBS ratio and the activator dose changed between trials.

Trays of the four raw materials: GGBS, coarse aggregate, fly ash and sodium metasilicate powder — **FIG 3.1**Raw materials, left to right: GGBS, coarse aggregate, fly ash, sodium metasilicate.

Material	Standard	Properties	Role
Fly ash	IS 3812 (Pt 1)	Class F · SG 2.20	Silica and alumina for the geopolymer gel
GGBS	IS 16714	Grade 120 · SG 2.85	Calcium for early strength under ambient curing
Activator	—	Sodium metasilicate powder · SG 2.40	Solid alkali; dissolves silica and alumina, starts geopolymerisation
Fine aggregate	IS 383	M-sand · Zone II · SG 2.65 · FM 2.75	Cohesion and workability
Coarse aggregate	IS 2386	Crushed stone 20 mm · SG 2.70 · FM 6.90	Strength and stiffness of the matrix
Steel	IS 1786	Fe500 · E 200 GPa	Reinforcement in the FE beam model

Trial mix proportions kg/m³ unless noted

Mix	Fly ash %	GGBS %	Binder	Fly ash	GGBS	Fine agg.	Coarse agg.	Activator	Water
Mix 1	30	70	500	150	350	589	1041	100	175
Mix 2	20	80	500	100	400	579	1027	125	175
Mix 3	10	90	500	50	450	569	1006	150	175
Mix 4	15	85	500	75	425	559	989	175	175

Specimens were cast in cube, cylinder and prism moulds, compacted in layers, demoulded after initial hardening and cured at ambient temperature, since the point of a one-part system is field use without heat curing.

S-403 Fresh concrete

Workability

Three tests on every mix. Mix 4 flows most, but flow alone is not the target: Mix 3 compacts best and still holds together, which is what matters for placing a reinforced member.

Slump

92mm · Mix 3

Workable and cohesive; Mix 4 flows more but with less cohesion.

Compaction factor

0.94Mix 3

Highest of the four: fewest voids after compaction.

Vee-Bee time

6s · Mix 3

Lower is easier to remould under vibration. Mix 3 responds well without segregating.

Trial mixesMix 3, selected

Mix	Slump (mm)	Compaction factor	Vee-Bee (s)	Reading
Mix 1	62	0.86	12	Stiff mix, lower compactability
Mix 2	78	0.89	9	Improved workability
Mix 3	92	0.94	6	Workable, cohesive, best compactability
Mix 4	105	0.91	5	Highest flow, but lower compaction and strength

S-404 Hardened concrete · 28 days

Strength

Compressive strength on 150 mm cubes, split tensile on cylinders and flexural strength on 150 × 150 × 700 mm prisms. Mix 3, with 90% GGBS and 150 kg/m³ activator, led on all three.

Compressive strength

45.8MPa · Mix 3

Used as the peak of the CDP compression curve in ABAQUS.

Split tensile strength

4.1MPa · Mix 3

Used as the crack-initiation stress in the tension model.

Flexural strength

6.3MPa · Mix 3

Modulus of rupture; directly relevant to beam bending.

Trial mixesMix 3, selected

Cube specimen in a compression testing machine — **FIG 4.7**Cube under compression.

Cylinder specimen loaded on its side for split tensile test — **FIG 4.9**Split tensile test on a cylinder.

Prism specimen fractured at midspan in a flexural testing rig — **FIG 4.11**Prism failed in flexure.

Mix	Compressive (MPa)	Split tensile (MPa)	Flexural (MPa)	Reading
Mix 1	31.2	2.7	4.2	Trial mix
Mix 2	38.6	3.3	5.1	Improved with higher GGBS
Mix 3	45.8	4.1	6.3	Highest on all three; carried into ABAQUS
Mix 4	42.1	3.8	5.8	More activator did not help further

S-405 Finite element analysis

Reinforced beam in ABAQUS

The cube, cylinder and prism results define the material, not the geometry. A separate 230 × 300 × 1000 mm reinforced beam was built with solid concrete elements and embedded truss reinforcement, then loaded at midspan in a nonlinear static step.

Concrete Damage PlasticityC3D8R solids · 25 mmT3D2 embedded trussStatic, general · NLGEOMViscosity 0.0005

Concreteρ 2100 kg/m³ · E 28 GPa · ν 0.20 · f_c 45.8 MPa · f_t 4.1 MPa · f_r 6.3 MPa (Mix 3)

CDP parametersDilation angle 30° · eccentricity 0.10 · f_b0/f_c0 1.16 · K_c 0.667 · viscosity 0.0005

Compression curve0 → 45.8 MPa peak at 0.0020 inelastic strain, softening to 28 MPa at 0.0045

Tension curveCracks at 4.1 MPa, tension-stiffening down to 0.2 MPa at 0.0010 cracking strain

SteelFe500 · E 200 GPa · ν 0.30 · f_y 500 MPa

BondEmbedded-region constraint (perfect bond; bond slip noted as a limitation)

SupportsLeft U1 = U2 = U3 = 0 (pinned) · Right U2 = U3 = 0 (roller)

LoadConcentrated 15 kN at midspan, applied with automatic increments

ABAQUS part module showing the 230 by 300 by 1000 mm beam solid — **FIG 5.1**Beam geometry.

ABAQUS material editor with Concrete Damage Plasticity parameters — **FIG 5.2**CDP material input.

Meshed beam with 25 mm hexahedral elements — **FIG 5.4**25 mm C3D8R mesh.

Beam with pinned and roller supports assigned — **FIG 5.5**Pinned and roller supports.

Results

Von Mises stress contour on the deformed beam, peaking at the bottom midspan — **FIG 5.7**Von Mises stress at 15 kN. Peak of about 32.5 MPa at the bottom midspan fibre; compression at the top, tension at the bottom, concentrations at load and supports, as expected for a simply supported beam.

Vertical deflection contour of the beam with maximum at midspan — **FIG 5.8**Vertical deflection U2. Maximum 4.1 mm at midspan, decaying smoothly to the supports with no instability. Bottom bars carry the tensile demand and control deformation.

S-406 Conclusion

What the study showed

One-part worksWith the right proportions, a just-add-water geopolymer gives structural-grade concrete with no Portland cement, and batching is as simple as ordinary concrete.

GGBS drives strengthRaising GGBS to 90% of the binder, activated by 150 kg/m³ sodium metasilicate, gave the best balance of workability, compactability and strength. More activator (Mix 4) did not improve further.

Lab to modelMeasured compressive, tensile and flexural values fed a Concrete Damage Plasticity model directly, so the beam analysis rests on tested material data rather than assumed values.

Beam behaviourThe reinforced OPGC beam showed classic flexural response: bottom-fibre tension resisted by the 16 mm bars, smooth deflected shape, and stress concentrations only where theory predicts them.

Skills exercised

ABAQUS · CDP modellingConcrete mix designLaboratory testing · IS codesNonlinear static analysisReinforcement modellingSustainable materialsTechnical reporting

Full method, literature review, test procedures and references are in the project report.