INFLUENCE OF FIBER REINFORCEMENT ON CONCRETE SHRINKAGE FOR RIGID ROAD AND AIRFIELD PAVEMENT REPAIR

Abstract

Abstract. The influence of fiber reinforcement with steel anchor fiber on the shrinkage of modified concrete for rigid airfield pavements repair has been determined. A 2-factor experiment was carried out, in which the following composition factors were varied: the amount of hardening accelerator Sika Rapid 3 from 0 to 2.4% of the cement content (0-9.6 kg/m3); the amount of steel anchor fiber with 1 mm diameter and 50 mm length, from 0 to 100 kg/m3. For the concrete batching were used: Portland cement CEM II / AS 42.5 in the amount of 400 kg/m3, granite crushed stone 5-20 mm, quartz sand, plasticizer admixture BASF MasterGlenium SKY 608 in the amount of 1.2% by cement content. The workability of the mixtures was S2 (6-8 cm); W/C ratio depended on the concrete composition. Due to the use of superplasticizers, the W/C of all investigated mixtures was in the range of 0.309-0.343. The shrinkage of the prism specimens was recorded after 3 hours, 6 hours, 1, 2, 3 and 7 days of being in air-dry conditions. The shrinkage process does not end after 7 days of concrete hardening, however, the general nature of the influence of variable factors on its value remains. It has been established that fiber-reinforced concretes, with a fiber amount of 50 kg/m3 and with a fiber amount of 100 kg/m3, have 10-15% less shrinkage compared to unreinforced concretes. Compositions with a fiber amount of 50 kg/m3 and 100 kg/m3 have practically the same shrinkage, which is explained by an increase in W/C ratio with an increase in the amount of fiber reinforcement. The amount of hardening accelerator has a less noticeable effect on the amount of concrete shrinkage. By adding Sika Rapid 3, concrete shrinkage at the age of 7 days is reduced by 2-9%. This effect can be explained by the fact that internal stresses arising in the process of structure formation and moisture loss in concrete are contained in a more durable cement-sand matrix. The concrete shrinkage without fiber and accelerator was also measured up to the age of 98 days. It was found that the limiting shrinkage for such concrete is 2.5×10-4. The analysis of the drawn experimental-statistical model showed that with the amount of metal fiber from 60 to 90 kg/m3 and the amount of the hardening accelerator from 0.9 to 2.4%, the shrinkage of the investigated concretes is minimal (7 = 1.3×10-4). Thus, the use of fiber reinforcement with anchor steel fiber and a hardening accelerator can significantly reduce the concrete shrinkage for the rigid airfield pavements repair is important for this material.