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High strength concrete mixtures containing 10% metakaolin replacement and 10% metakaolin addition, water/cementitious material ratio of 0.3 and 1% super-plasticizer were studied.. Similar mixtures incorporating silica fume were also prepared. The effect of mineral admixtures on the fresh and hardened properties of concrete was investigated. Mixtures with mineral admixture exhibited lower workability, less bleeding, and slightly lower air content. Metakaolin resulted in a higher loss of workability compared with silica fume. Mixtures incorporating mineral admixture developed greater compressive strength and elastic modulus at all ages. The enhancement was more pronounced at early ages and in the addition mixtures. The study concludes that the performance of metakaolin is equivalent to silica fume in terms of contribution to the enhancement of strength and elastic modulus. The metakaolin addition mixture attained 70% and 50% strength improvement while the metakaolin replacement mixture achieved 67% and 39% strength increment at the respective ages of 3 and 28 days.

bleeding; bottom ash; CLSM; compressive strength; deterioration; durability; flowability; fly ash; freezing and thawing; frost heaving; mix proportioning; slump flow; used foundry sand

This work was conducted to develop two types of controlled low strength materials (CLSM) or flowable slurry utilizing post-consumer glass (broken glass or glass cullet) aggregate and fly ash. Type A CLSM consisted of glass, fly ash, cement, and water; and Type B CLSM consisted of glass, sand, cement, and water. All mixtures were proportioned to achieve the 28-day compressive strength of 0.7 MPa (100 psi). The Type A CLSM mixtures consisted of a control mixture (100% fly ash without glass) and five other mixtures with glass, as a replacement of fly ash in the range of 20 to 80 percent. The Type B CLSM mixtures were composed of a control mixture (without glass) and two other mixtures at 30 to 75 percent replacement of sand with glass. The flowable slurry developed in this project satisfied the ACI Committee 229 definition of CLSM. Decreasing the amount of fly ash and increasing the glass content led to increased bleeding and segregation at high replacement levels of 60% and 80%. Permeability of Type A CLSM remained essentially unchanged except at high glass contents it was lower. For Type B CLSM, the permeability was about the same.

This paper deals with the development of self-levelling concrete at low cost for casting slabs and other horizontal structures. The 28-day compressive strength of such concrete is in the range of 25 to 40 MPa, and its cost is 15 % higher than that of usual concrete. This overcost is offset by some advantages: quicker execution, absence of noisy vibration at job-site and reduced painful task for workers. The cement content for this concrete ranges from 260 to 380 kg/m’, and that of limestone powder from 20 to 140 kg/m3, in order to get a total amount of fine particles of 400 kg/m3. To prevent segregation, a viscosity agent - a suspension of modified starch - was introduced in the mixture at different contents. The following characteristics were measured: static spread of concrete, unit weight, bleeding, resistance to segregation, compressive strength, elastic modulus and shrinkage. The results show that the optimum dosage of viscosity agent is 2 kg/m3, regardless of the amount of cement.

Although 37 million tons of concrete wastes have been generated annually in Japan, the use of recycled aggregate for concrete is limited because of low density and high absorption due to adhered cement paste and mortar. A new method to produce high qualty recycled aggregate by heating and grinding concrete rubbles to separate cement portions adhering to aggregate was developped recently. In this process by-product powder with the fineness of 400 m/kg is generated. By-product recycled concrete powder consists of fine particles of hydrated cement and crushed aggregate. To utilize the recycled concrete powder as concrete additives two series of experiments were performed to make clear of the effect of recycled powder. Self-compacting concrete with recycled concrete powder, ground blast-furnace slag and ground limestone were tested for slump-flow, compressive strength, modulus of elasticity and drying shrinkage. Reduction in super-plasticizing effect of high-range water reducer was found for concrete with recycled concrete powder. Compressive strength of concrete with recycled concrete powder were the same as those with ground limestone, and lower than those with ground slag. Concrete with recycled concrete powder showed lower elastic modulus and higher drying shrinkage than those with ground slag and ground limestone. The recycled concrete powder is usable for self-compacting concrete without further processing, despite the possible increase in dosage of high-range water reducer for a given slump-flow and in drying shrinkage. The addition of ground blast-furnace slag together with recycled concrete powder to self-compacting concrete improved superplasticizing effect of high-range water reducer and properties of concrete .