Abstract
One of the biggest technological problems connected with the production of lightweight concretes made of porous aggregates is their much higher water absorption, which may cause on the one hand workability loss, and on the other hand excess water content in concrete. The aim of this research was to assess the effect of impregnation of lightweight aggregates (LWAs) with cement paste on their properties and to verify its effectiveness in concretes. Three types of lightweight aggregates differing in porosity and pore structure (sintered fly ash Lytag, expanded clay: Leca and Liapor) were selected for the tests. The following parameters were taken into consideration in the research program: LWA type and size, LWA initial moisture content, strength, and rheology of cement pastes. The tests of 22 different aggregates, plain and coated with cement paste, included density, crushing strength, and development of water absorption in time. The research program proved that porous aggregates, due to their impregnation with cement pastes, may be effectively sealed and strengthened. All tested LWAs showed a considerable decrease in water absorption by up to 71%. However, only Lytag aggregate showed a visibly enhanced crushing strength. Verification of effectiveness of aggregate sealing on the enhancement of concrete properties showed both a considerable reduction in water absorption of composites (by up to 52%) and a very high increase in their strength (by up to 107%).
Highlights
Lightweight aggregate concrete (LWAC) is deemed as one of the most comprehensive building materials, used for both structural and insulating purposes, and made for both monolithic and precast applications
Oven dry density for each LWAC was determined in three specimens used previously for water absorption tests
The analysis of the archived test results showed that pre-coating of lightweight aggregates with cement paste may enhance both the properties of LWAs themselves, and properties of concrete made of these aggregates
Summary
Lightweight aggregate concrete (LWAC) is deemed as one of the most comprehensive building materials, used for both structural and insulating purposes, and made for both monolithic and precast applications. On the other hand, owing to the application of by-products for aggregate manufacturing in better thermal insulation, possible better durability [5,6,7,8,9], and possibility of recycling, LWAC is regarded as one of the most sustainable building materials. Application of lightweight aggregate (LWA) may increase the risk of fresh concrete segregation and/or workability loss, resulting from much lower LWA particle density (typically from 400 up to 2000 kg/m3 ) and much higher LWA water absorption (typically from 5 up to 45%) in relation to normal-weight aggregate (NWA) [4].
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