Impact of different wood ash fractions on the load-bearing capacity of sand mixtures

Abstract

Different types of natural aggregates (gravel, crushed stone, sand) are used in the construction of load-bearing layers of pavement structures, the granulometric composition of which has a great influence on the compaction and load-bearing capacity of the layer. Special care should be taken when compacting single-grain materials, such as sand, as difficulties can be expected with these. For this reason, it is useful to modify the granulometric composition of the sand by adding new material of finer fractions. The bearing capacity of mixtures for the production of unbound load-bearing layers of a pavement structure is tested by determining the California Bearing Ratio (CBR), the value of which depends on the dry bulk density achieved and the granulometric composition of the mixture. The bearing capacity of the mixture is influenced by the grain shape and grain surface characteristics of the stone material. This paper describes the testing of mixtures intended for the performance of load-bearing layers of pavement structures, consisting of Drava sand and wood ash (WA) of different fractions (bottom wood ash (WBA) and fly (cyclonic) wood ash (WFA)) and different proportions. The CBR index was determined after immersion of the samples for 4 days under water, during which time swelling was monitored. The results showed that wood fly ash (WFA) has a greater impact on the bearing capacity of the sand mixture and, using it, lower linear swelling results are achieved as well as higher CBR results. Different types of natural aggregates (gravel, crushed stone, sand) are used in the construction of load-bearing layers of pavement structures, the granulometric composition of which has a great influence on the compaction and load-bearing capacity of the layer. Special care should be taken when compacting single-grain materials, such as sand, as difficulties can be expected with these. For this reason, it is useful to modify the granulometric composition of the sand by adding new material of finer fractions. The bearing capacity of mixtures for the production of unbound load-bearing layers of a pavement structure is tested by determining the California Bearing Ratio (CBR), the value of which depends on the dry bulk density achieved and the granulometric composition of the mixture. The bearing capacity of the mixture is influenced by the grain shape and grain surface characteristics of the stone material. This paper describes the testing of mixtures intended for the performance of load-bearing layers of pavement structures, consisting of Drava sand and wood ash (WA) of different fractions (bottom wood ash (WBA) and fly (cyclonic) wood ash (WFA)) and different proportions. The CBR index was determined after immersion of the samples for 4 days under water, during which time swelling was monitored. The results showed that wood fly ash (WFA) has a greater impact on the bearing capacity of the sand mixture and, using it, lower linear swelling results are achieved as well as higher CBR results.