Normal Weight Coarse Aggregates Research Articles

Self-compacting lightweight aggregate concrete: design and experimental study

This study focuses on the production of self-compacted lightweight structural concrete. For this purpose, lightweight concrete was produced by replacing normal aggregate with pumice aggregate obtained from the Kayseri region. Three series of mixtures were prepared to obtain the proper self-compacting lightweight concrete (SCLC) mixture. The D series included normal-weight, self-compacting concrete (SCC) mixtures and the H series included SCLC mixtures having 100% lightweight coarse aggregate and different air contents. Fresh concrete test results obtained from these mixtures were used as a basis for the T series containing different amounts of lightweight and normal-weight coarse aggregate. Some mechanical and fresh concrete properties were obtained from the T series. It was found that the loss of strength owing to lightweight aggregate addition is higher than the decrease of unit weight of the mixture. Furthermore, the decrease in flexural tensile strength owing to addition of lightweight aggregate is less than the reduction in compressive strength and splitting tensile strength. The percentage of entrained air and paste content are important factors to avoid segregation problems in lightweight SCC mixtures. There is a good relationship between 28-day compressive strength and unit weight data obtained from the H and T series.

Use of porous ceramic waste aggregates for internal curing of high-performance concrete

Internal curing has become extensively used to reduce autogenous shrinkage and consequently mitigate the high risk of early age cracking of high-performance concrete (HPC). This paper investigates the efficiency of internal wet curing provided by a new type of aggregate, "recycled waste porous ceramic coarse aggregates" (PCCA). Six different silica fume HPCs with and without the PCCA are examined with respect to measured physical and mechanical property development. Four different replacement proportions of normal weight coarse aggregate (NCA) by the PCCA have been evaluated. The results have shown a high effectiveness of the PCCA for internal curing purposes, to drastically reduce and even to completely eliminate autogenous shrinkage of HPC prepared with a very low water/binder ratio (w/b) of 0.15. It has been found that the incorporation of 40% of the PCCA leads to a non-shrinking HPC that results in an insignificant internal stress accompanied by a significant increase of the compressive strength. It should be noted that for the different proportions of the PCCA incorporated no decrease of the compressive strength has been observed at either early or later ages, as is the case with some conventional lightweight aggregates.

Strength and shrinkage properties of alkali-activated slag concrete containing porous coarse aggregate

An investigation was conducted that examined the effects of internal curing of alkali-activated slag concrete (AAS) by replacing normal weight coarse aggregate with fully saturated blast-furnace slag coarse aggregate. The slow release of moisture from the porous aggregate provides ongoing internal curing of concrete. The study showed that, under drying conditions, the compressive strength was improved and the drying shrinkage was significantly less (40% less than AAS containing normal weight coarse aggregate).