RECIPE AND TECHNOLOGICAL METHODS OF INCREASING THE DURABILITY OF CONCRETE ON LIGHT FILLERS FOR THIN-WALLED HYDRO-TECHNICAL AND TRANSPORT CONSTRUCTIONS

Abstract

To increase the durability of lightweight concrete thin-walled constructions of hydro-technical and transport structures it is necessary to increase their water-tightness and frost-resistance. Purpose of the research is the development of prescription and technological methods for increasing the durability of concretes on lightweight aggregates through the use of rational modifiers and treatment of a porous aggregate.

Two methods of processing a porous filler are suggested. The first method is the hydrophobization of its surface. Hydrophobization reduces the absorption of water from the cement matrix and the W/C mixture, and also reduces the volume deformation of the aggregate. The second method is the treatment with a cement slurry in the initial stage of mixing the mixture. Due to the treatment, the surface layer of the aggregate and the transition zone between the aggregate and the cement-sand matrix hardens. Both methods contribute to the transformation of the porosity of the aggregate into a closed porosity.

It is established that due to hydrophobization, the volume moisture deformations of gravel are reduced by 3..4 times. Also, hydrophobization increases the strength and water-tightness of expanded clay lightweight concrete. By treating the porous aggregate with a cement slurry, the strength of lightweight concrete increases by 2..3 MPa, and the water-tightness increases by one grade.

Also, to improve the durability of concretes on porous aggregates, it is recommended to use modifiers. The effect of plasticizers, colmatizing additives, silica fume and fibers on the properties of lightweight concrete was investigated.

It has been established that expanded clay lightweight concrete modified by rational chemical additives has high water-tightness (W8-W14), frost-resistance 200..300 cycles in seawater, compressive strength from 35 to 45 MPa, tensile strength from 4,5 to 7 MPa. The average density of these lightweight concretes in the water-saturated state is from 1800 to 1870 kg/m³. Thus, modified expanded clay lightweight concrete on the basis of processed gravel is an effective material for a significant part of thin-walled constructions of hydro-technical a nd transport structures, including floating reinforced concrete structures.