Self-compacting lightweight aggregate concrete in Vietnam

Abstract

Self-Compacting Lightweight Aggregate Concrete (SCLC) is a new building material in Vietnam. The lightweight aggregates (keramsite) produced from expanded clay or slate is used for the SCLC. If dry Keramsite is used in making the concrete mixture, it will partly absorb water from the cement paste, which causes the slump loss of concrete mixture, increasing shrinkage of cement matrix in the concrete. With regard to Self-Compacting Structural Lightweight Aggregate Concrete (SCLC), the cement content used is significant, the ratio of Water to Binder is rather low, and the structure of cement paste is very dense. This does not only increase the autogenous shrinkage of concrete but also have influence on the effectiveness of external curing. Taking advantage of the special structure of Lightweight aggregate as Keramsite, internal curing can be performed in order to improve the quality of SCLC by wetting Keramsite before mixing with suitable water absorption.This paper presents some research results about SCLC, the incorporation of internal curing with other measures such as the use of dispersal fiber reinforcement, viscous stabilizing admixtures in order to restrain the segregation level of lightweight aggregates, reducing shrinkage and improving mechanical-physical properties of SCLC in the hot-humid climate condition of Vietnam. The research results show that, from selected materials, lightweight concretes with unit weight of 1600 - 1800 kg/m3, compressive strength of 30 - 35 MPa, good workability, capable of self-compacting can be manufactured. The use of pre-wetted lightweight aggregate with suitable humidity for producing SCLC will result in better effectiveness than the use of dry lightweight aggregate, as in reducing restraining shrinkage, improving the strength for SCLC.