A study to ascertain the productivity of different types of cement used in block production in Uganda

Abstract

Bricks are the most commonly used form of building in the world. In Uganda like many other parts of the world, many buildings are built with clay bricks. They are associated with several disadvantages as they are small in size, require a lot of mortar to join each other, and require plastering them from both faces to fill the unevenness of the wall surface to provide a better finish. Concrete blocks are a good substitute to clay bricks as they reduced mortar consumption, offering unique combination of high durability, strength and faster speed of work compared to brick. But during the production of these blocks, cement is not used efficiently as its productivity is not known. Cement productivity refers to the amount of strength obtained from a single unit of cement, serving as a measure of cement quality. It can also be defined as the 28th day strength divided by cement content. Results from a case study in Dar es Salaam show that cement is poorly used in the main application of sandcrete blocks. The relative cement productivity was found to range within 20- 30% a very low value compared to when used in the production of mass concrete (Isaksson and Buregyeya, 2020). With low cement productivity, cement consumption is high in order to achieve a desired strength. To improve cement productivity, there is need to change the products used in making the sandcrete blocks or shift to hollow blocks (Isaksson and Babatunde, 2019). This study investigates the productivity of various cement types specifically CEM I, CEM II, CEM IV and volcanic ash, lime- gypsum binder in the production of concrete hollow blocks. The volcanic ash used in this research was sourced from Nyarurambi volcanic ash deposit in Rutooga village, Rubanda district. All cements (CEM I, CEM II, and CEM IV), Lime and gypsum were bought from Hardware World, Kampala. All the materials used to include sand, stone dust, cement and volcanic ash were characterized to know their physical properties. Concrete hollow blocks were produced using different percentages i.e. 5,6 & 7% of each type of cement and their compressive strength evaluated through a standard compressive strength test at 3, 7 and 28 days. All blocks made were able to achieve the minimum requirement of 2.8MPa in accordance to BS EN 771-3 and Ministry of Work’s standard specification for building works Type A concrete hollow blocks. Cement productivity was calculated as the ratio of the 28-day compressive strength to the percentage of cement used in the mix. The results indicated that the volcanic ash –lime- gypsum binder with a binder content of 12.5% exhibited superior productivity (52.9%) compared to the conventional cement types (CEM I, CEM II and CEM IV) which showed relatively lower productivity values. This enhanced productivity attributed to the synergistic pozzolanic reactions and optimized binder composition of the volcanic-ash-based mix. The findings suggest that the volcanic ash –lime- gypsum binder could serve as a sustainable and cost-effective alternative for block production, particularly in regions with abundant volcanic ash resources.