Supplementary cementitious materials

Geopolymerization is a developing field of research for utilizing solid waste and by-products. It provides a mature and cost-effective solution to many problems where hazardous residue has to be treated and stored under critical environmental conditions. Geopolymer involves the silicates and aluminates of by-products to undergo process of geopolymerization. It is environmentally friendly and need moderate energy to produce. This review presents the work carried out on the chemical reaction, the source materials, and the factor affecting geopolymerization. Literature demonstrates that certain mix compositions and reaction conditions such as Al2O3/SiO2, alkali concentration, curing temperature with curing time, water/solid ratio and pH significantly influences the formation and properties of a geopolymer. It is utilized to manufacture precast structures and non-structural elements, concrete pavements, concrete products and immobilization of toxic metal bearing waste that are resistant to heat and aggressive environment. Geopolymers gain 70% of the final strength in first 3–4 h of curing.

Mechanism of geopolymerization and factors influencing its development: a review

Cement substitution by a combination of metakaolin and limestone

Influence of metakaolin on the properties of mortar and concrete: A review

The origin of the pozzolanic activity of calcined clay minerals: A comparison between kaolinite, illite and montmorillonite

The utilisation of calcined clay, in the form of metakaolin (MK), as a pozzolanic material for mortar and concrete has received considerable attention in recent years. This interest is part of the widely spread attention directed towards the utilisation of wastes and industrial by-products in order to minimise Portland cement (PC) consumption, the manufacture of which being environmentally damaging. Another reason is that mortar and concrete, which contain pozzolanic materials, exhibit considerable enhancement in durability properties. This paper reviews work carried out on the use of MK as a partial pozzolanic replacement for cement in mortar and concrete and in the containment of hazardous wastes. The literature demonstrates that MK is an effective pozzolan which causes great improvement in the pore structure and hence the resistance of the concrete to the action of harmful solutions.

Metakaolin and calcined clays as pozzolans for concrete: a review

Using neural networks to predict workability of concrete incorporating metakaolin and fly ash

Freeze-thaw tests were carried out on air-entrained and non-air-entrained concrete prisms containing different dosages of condensed silica fume (CSF). Six concrete mixes were made incorporating 0, 5 and 10% CSF as partial replacements for OPC. The performance of the concrete prisms exposed to 210 cycles of freezing and thawing was assessed from weight, length, resonance frequency and pulse velocity measurements of the test specimens before and after freezing and thawing. Tests were also conducted to determine the compressive and flexural strengths and the static modulus of elasticity. Although the control concrete gave better durability factors (92%) than those obtained for the CSF concrete (85%), the physical appearance of the CSF prisms exhibited less scaling.

Mechanical properties and frost resistance of silica fume concrete

Stress analysis of a compact compression specimen used for the determination of the fracture toughness of cementitious materials is carried out by the finite element method. The specimen, which is based on 100 mm cubes, contains two notches on opposite faces. It is found that the geometry and loading result in large tensile stresses at the root of the notch remote from the load. These stresses are sufficient to propagate the crack in the opening mode of fracture thus enabling the fracture toughness of the material to be determined. The fracture toughness is evaluated from the failure load and the stress intensity factor computed from the finite element results. Several finite element mesh refinements were employed and accurate estimates of the stress intensity factor were obtained by modelling the specimen by a relatively small number of elements. The accuracy of the results was largely independent of the evaluation method which included displacement extrapolation, conic section simulation, strain energy release rate and the J-integral. Whereas the stress intensity factor varied with the notch size, the tests conducted in the present work did not show significant variation in the fracture toughness.

Stress analysis of a fracture test specimen for cementitious materials

Stress analysis of the compression-splitting geometry due to Karihaloo is carried out by using the finite element method The study confirms that large tensile stresses are present near the crack tip and that failure is predominantly of the opening mode of crack extension Several methods were employed to evaluate the stress intensity factor K , all of which gave results that were in close agreement In evaluating the fracture toughness, K c , it is found that the analytical solution is not sensitive to the length of the crack and that, whereas K c is a material property, the stress intensity factor K is purely a function of geometry and loading and is unaffected by other material properties, such as the modulus of elasticity, E  Axial-splitting tests were conducted on concrete prisms modified by introducing a central notch at one end by using one of two methods In the first, the notches were cast in situ by using standard steel moulds incorporating steel plates forming the notches In the second, the notches were cut after the prisms had been fully cured by using a diamond-impregnated cutting disc Although the tests reported in the present paper were conducted on concrete specimens, the geometry and testing arrangement can also be applied to other materials, such as mortar and FRC composites

B.B. Sabir

Papers

Metakaolin and calcined clays as pozzolans for concrete: a review

Using neural networks to predict workability of concrete incorporating metakaolin and fly ash

Mechanical properties and frost resistance of silica fume concrete

Stress analysis of a fracture test specimen for cementitious materials

The use of compression-splitting tests in evaluating the fracture toughness of concrete