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- Compressive strength (2) (entfernen)
Rice husk as (RHA) is an eco-friendly material, which can be used as a supplementary cementitious material (SCM) in cement and concrete. Due to the high water demand for the material, superplasticizers (SPs) are essential to improve the performance. However, the interaction between the SPs and RHA systems is limited. This paper investigates the interaction of the binders with three SPs, i.e. two polycarboxylate ethers (PCEs) and one lignosulphonate (LS). The investigations are performed on blended systems of mortar containing various percentages of RHA and limestone powder (LSP). LSP is used in this research to improve the workability of the mortar. The results from the zeta potential (ZP) shows that the SPs are extremely dependent on the pH of the suspension. At higher pH values such as in a cementitious system, the ZP becomes less negative indicating that the ions in the suspension interact with the carboxyl groups in the backbone of the polymers thus reducing the surface charges of the SP. The mini-slump flow shows that the workability of the blended mortar systems is significantly improved with the addition of SPs. LS systems with increasing RHA is observed to have similar workability as the control mix over time. The compressive strength test results show increased strength for all mortar specimens with added RHA and LSP at later ages.
The main aim of the research was the development of a first valid database for material parameters of earth block masonry (EBM) with particular regard to statistical characteristics. A solid database is needed for the determination of the materials partial safety factor. Therefore, compressive strength tests were carried out with two types of earth blocks and two types of prefabricated earth mortar.
The evaluation has shown that the mean variation of the compressive strength was remarkably less than expected, which indicates high quality standards of the components earth block and mortar with regard to industrial production. Using the reliability method, a partial safety factor for EBM subjected to compression was determined on the basis of these test results. The findings have shown that a common calculation method for EBM based on partial safety factors following the valid masonry construction standard is feasible.