This paper presents the concrete structure repairing method, using concrete with expanded polystyrene granules (EPS). Reinforced concrete slabs are cast with depression of the top surface up to 70 mm. For the top surface leveling, with minimum selfweight load addition, a new flooring system is developed: over the sound isolation layer, EPS concrete leveling layer, 60-130 mm thick, (p = 450-500 kg/m3, Bk = 1-2 MPa) is cast. As a top finishing surface, high performance concrete layer, 15 mm thick (Pk = 60 MPa) is cast. Flooring system satisfied all the requirements, with total weight of 55-90 kg/m2.

A laboratory test and a case history of deteriorated reinforced concrete slab repair are presented. Since several structural problems have been reported for reinforced concrete slabs, it is necessary to establish repair techniques for such slabs. Many structural problems of reinforced concrete slabs derive from a decline in rigidity with age. Although several techniques have been developed, their effectiveness has not been ascertained, especially over the long term. A laboratory test was conducted to ascertain the effectiveness of repair techniques. Based on the test results, the overlay repair technique was applied to actual slabs. In the case history, short and long-term performances of the repaired slabs were measured for more than 2000 days. Changes in the rigidity and natural frequency of the slabs were examined. The material properties and adhesive strength of old and new concrete were also examined. Although the static and dynamic performances of the repaired slabs improved remarkably, their performances gradually decreased with age. It is important to allow a reasonable margin of error for repairing deteriorated slabs.

Today, in Russia, carbide - silicon and aluminate - silicate packing masses are generally used for lining blast - furnace chutes. They contain re-fractory clay, coal-tar pitch and resins as binders which emit carcinogenic sub-stance dangerous for a human organism. Thirty compositions of chute concrete masses excluding any carcinogenic substance were studied and tested on a chute by the Siberian State University of Industry in conjunction with the Kuznetsk Metallurgical Combine company. The best results were obtained with the following composition: 75 % fused electrocorundum, 20 % refractory clay, 5 % high-alumina cement and 7.3 % water (above 100 %). Thermal resistance in heat changes was above 25 cycles at 800 ‘C, apparent density was 2.54 to 2.75 g/cm3, compressive strength was 76.6 and 79.2 MPa at 110 ‘C and 1450 ‘C, respectively, slag resistance was 0.1 to 0.2 mm at 1450 ‘C, firing shrinkage was 0.2 % with no corrosion observed. The composition developed increased the service life by 10 times compared with the composition generally applied and does not emit any carcinogenic matters. However, in view of the economic crisis and high cost of the electrocorundum, its application is limited. Therefore, we have developed compositions with a high - alumina product (HAP), the waste from the Yurga abrasive works, as a replacement for the electrocorundum. They are as follows: (i) 35 % HAP, 20 % fireclay powder, 15% refractory clay, 30 % waste from the production of silicon carbide; (ii) 48 % HAP, 20 % fireclay powder, 15 % refractory clay, 32 % waste of silicon car-bide with a particle size distribution of 3 to 0 mm. These compositions exhibit < 50 % reduction in strengths (from 80 to 40 MPa) at 1450 ‘C with other indices (slag resistance, iron resistance, apparent density and shrinkage) being the same as for compositions containing pure fused electrocorundum. Their cost is simi-lar to that of the concrete masses generally used but the service life is 4 times longer which was proved by testing in a central chute of a blast furnace.

In recent years, glass fiber reinforced plastic material (GFRP) has been used as a repair or rehabilitation material for deteriorated R.C. structures. The main topic of this paper is a study of the strengthening of reinforced concrete beams using prestressed glass fiber reinforced plastic material (PGFRP). The increase in the load capacity and the deflections in R.C. beams using GFRP and PGFRP were tested and compared. Two beam shapes, T-shaped and inverted T beams, were used as under-strengthened and over-strengthened beams in these tests. Test results show that PGFRP can be used to strengthen R.C. beams and cause no crack when the pretension is transferred. For the load capacity, the test results indicate that, for T-shaped beams, using GFRP can increase the load capacity by as much as 55% compared with the reference beams and PGFRP can increase by 100%. For inverted T beams, using GFRP can increase the load capacity by as much as 97%, and PGFRP can increase by 117%. For the deflections, at the same external loads, beams with GFRP display larger deflections than beams with PGFRP.’ Test results also show that using glass fiber plates to strengthen R.C. beams will decrease the displacement ductility of the beams. The over-strengthened beams have less displacement ductility than under-strengthened beams.

This study focused on the investigation of durability characteristics of very early strength concretes incorporating polypropylene fibers and application feasibility of these into the highway pavements. A series of laboratory tests were performed to assess the strength development and scaling resistance. The test of surface scaling resistance was performed according to ASTM C 672 exposed to frost in the presence of de-icing chemicals. The experimental variables included cement types, fiber contents and concrete mixtures. The compressive strength of very early strength concrete at 3 hours was measured as 22 MPa, which corresponded to the strength at 7 days or 28 days of ordinary portland cement concrete. This may enable the repaired concrete pavement to be opened to traffic 3 hours after concrete placement. There was little effect of polypropylene fiber reinforcement on compressive strength. The fiber reinforced concretes exhibited noticeably higher flexural strength than the reference concrete at all ages. The plain concrete slabs were given a visual rating of 3 or 4, and according to ASTM Standard C 672. This corresponds to moderate to severe scaling. The fibrous concrete performed better than the plain concrete slab which was given a visual rating of 0 or 1. This corresponds to no scaling or very light scaling. As the amount of fiber reinforcement increased the surface scaling resistance increased. The scaling resistance of very early strength concrete was comparable to that of ordinary concrete from the visual rating. Thus, the developed very early strength concrete may be satisfactory for use in repair works for pavements.