Effect of Lightweight Aggregate Impregnation on Selected Concrete Properties

Abstract

The impregnation of lightweight aggregate (LWA) is an alternative method to its pre-moistening, which is used to limit the loss of fresh concrete workability due to the aggregate’s ability to absorb a great amount of mixing water. The aim of this study was to access the effectiveness, by pre-coating LWAs with cement paste, in modifying the properties of concrete composites. Two types of lightweight aggregates (Lytag and Leca) characterized with a relatively open-structure shell were selected. The other changeable parameters taken into consideration in this research were: LWA size, initial moisture of aggregate before the impregnation process and type of cement paste applied as an impregnant. Sixteen concretes prepared with pre-moistened and pre-coated lightweight aggregates were subject to a density test in different moisture conditions, a water absorption test and a compressive strength test. On the one hand, the pre-coating of LWAs with cement paste resulted in a relatively slight increase in concrete density (by up to 19%) compared to the pre-moistening of LWAs. On the other hand, it caused a very significant reduction (by up to 52%) in the composite’s water absorption and an incomparably greater growth (by up to 107%) in compressive strength. The most crucial factors determining the effectiveness of impregnation of LWAs with cement pastes in improvement of composite properties were the aggregate type and its size. The composition of impregnating slurry and the initial moisture content of LWA before pre-coating also mattered.

Assessment of Properties of Structural Lightweight Concrete with Sintered Fly Ash Aggregate in Terms of Its Suitability for Use in Prestressed Members

“…In designing structures, rheological properties of concrete, such as shrinkage and creep, are also important characteristics. Due to the lower modulus of elasticity of the porous aggregate, lightweight concretes are characterized by increased shrinkage in comparison to NWAC, even by up to 50%, which was confirmed by much research on this phenomenon [7,[16][17][18]. On the other hand, since lightweight concretes have the ability to internal curing owing to water accommodated in LWA, the development of their shrinkage may be slower in time and less dependent on conditions of external curing such as temperature and humidity conditions.…”

“…Its particles are characterized by a closed structure of the external shell and a regular, spherical shape. The properties of the aggregate, shown in Table 1, especially crushing resistance and water absorption, indicate that in comparison to other sintered fly ash aggregates [1,2,6,14,18], this LWA may create new opportunities for its application in more advanced fields, e.g., for prestressed structures. Due to its high water absorption the aggregate was initially prewetted to its moisture content corresponding to its water absorption after 24 h (WA 24h ) before application for concrete.…”

“…Generally, the experimental studies proved that in the case of lightweight concrete, like for normal-weight concrete, the following rule is applied: the higher the compressive strength, the lower the creep. Various research showed that LWAC creep can be higher [18] or similar [4,[24][25][26] as for NWAC of comparable strength. In some rare cases, LWAC of higher strength class creep may be even lower than for NWAC of the same class [4].…”

A Review of Lightweight Self-Healing Concrete

“…The workability of fresh concrete decreased due to the aggregate absorbing a large amount of mixing water [ 84 ]. The mean water absorption for tested composites was up to 16.7% for reference concretes with non-impregnated LWAs [ 84 ]. Therefore, the workability of LWC also needs to be paid attention to when using impregnation.…”

Current Problems of Hardening Monolithic Road and Aerodrome Cement Concrete Curing

“…The possibility of "self-healing" of cracks was noted by some researchers. For example, in (Domagala & Podolska, 2022) it was shown that water ingress into cracks and other defects in the concrete structure leads to the emergence of the wedging effect. In this case, the strength of concrete is reduced by up to 30 %.…”