Slab is the most important structural member of any building structure and also one of the largest member consuming concrete. Thus, the alternative biaxial hollow slab system known as bubble deck slab had been introduced as one of the effective slab systems that improves building design and performance while reduce the self-weight by eliminating concrete part in the middle of conventional slab which does not contribute to the structural performance. The effective hollow slab systems that dramatically reduce the slab weight by 30-50%. Moreover, concrete usage is reduced as 1 kg of recycled plastic replaces 100 kg of concrete. The new prefabricated construction technology using bubble deck slab is recently applied in many industrial projects in the world. It has many advantages as compared to conventional reinforced concrete slab such as lower total cost, reduced material use, enhanced structural efficiency, decreased construction time, and is a green. The aim of this paper is to discuss the significance and various properties of bubble deck slab against conventional reinforced concrete slab based on various studies and researches that had been done.

Slab is the most important member in any building structure which consume large amount of concrete. The slab self-weight is large due to large consumption of concrete in producing slab. Therefore, bubble deck slab is an innovative and newly designed biaxial hollow slab system that had been introduced in order to overcome this problem. Bubble deck slab is a revolutionary method which was developed by Jorgen Bruenig from Denmark in the 1990s. The bubble deck slab had been designed and constructed with plastic hollow bubbles in the middle part of slab to eliminate the concrete which does not perform any structural function and at the same time reducing the slab self-weight. Thus, the self-weight of bubble deck slab can be reduced about 30-50% than conventional concrete slab; that can reduce the loads acting on columns, walls and foundations. Finally, the use of bubble deck slab can give many benefits as compared to conventional concrete slab such as improve the structural performance of slab, reduce the materials and cost, efficiency and faster construction time, and it is also a green product. The aim of this paper is to give some of the reviews from previous studies related to bubble deck slab.

Geopolymer based cementitious materials were produced to reduce or completely eliminate the use of cement in concrete in which could be incorporated with waste materials. In this study, rice husk ash (RHA) which is a waste having rich in silica content after burnt was intended to be used as based geopolymer. Besides, sewage sludge ash (SSA) was incorporated with RHA producing geopolymer mortar in which also having pozzolanic element of Si and Al. Geopolymerisation requires Si and Al elements to react with highly alkaline solution to produce geopolymeric material. Therefore, combination of RHA and SSA will be possible solution as base geopolymer mortar in order to provide Si and Al. The effect of SSA inclusion was investigated under different sodium hydroxide (NaOH) molarity and curing conditions to the strength development. NaOH and sodium silicate were used as activator with ratio of 1:1 and the solution to ashes ratio of 1:1 was used. Compressive strength was tested at 7, 14 and 28 days. The results showed that the geopolymer mortar made of SSA replacement exhibited higher compressive strength with reference to those made of RHA (control sample). In addition, the results showed that geopolymer mortar specimen containing 15% of SSA replacement activated with 8M NaOH solution gave the highest strength recorded 15.0MPa in oven curing condition (60°C for 24 hours). As conclusion, SSA up to 20% replacement has potential to be used in producing geopolymer as replacement alternative to RHA.

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