Intelligent Replaced of Natural Aggregate and Cement with Recycled Concrete Aggregate, Rice Husk Ash

Annually a huge amount of construction and demolition (C&D) waste is generated. It becomes really harmful and posing an adverse effect to the environment, increasing waste generation have demanded the need for recycling the C&D Waste. Similarly, as cement accounts for 10% global CO2 emissions, it is imperative to reduce the embodied CO2 of concrete. Thus, the sustainability of concrete is a major issue which needs to be addressed. Ways of achieving this is to recycle concrete waste back into concrete to reduce waste and use of supplementary cementitious to reduce CO2 emissions. This research aims to take a two-pronged approach by investigating the effect of pozzolanic replacement with fixed proportion of recycle aggregates to evaluate the strength and potential structural application. In this research carried out M40 mix design and rice husk ash were substituted for cement at level of 5, 10, 15, 20% by using a fixed ratio of 10, 20,30% recycle concrete aggregate (RCA). Compression test, Split Tensile Test, Flexural Test and Rapid Chloride penetration test were conducted on specimens of Grade M40, for compression test the cube was cured for 28 days and 90 days for durability (RCPT). All RCA mixes and up to 15% RHA replacement satisfied M40 criteria at 90 days, however the 20% RHA replacement mix was close to achieving this. Thus, the finding of this study indicates the use of concrete containing 30% RCA and 15% RHA can be substantially reduce waste and embodied CO2 without compromising on strength and durability parameters.

The mechanical properties of brick containing recycled concrete aggregate and polyethylene terephthalate waste as sand replacement

This research focuses on the performance of composite sand cement brick containing recycle concrete aggregate and waste polyethylene terephthalate. This study aims to determine the mechanical properties such as compressive strength and water absorption of composite brick containing recycled concrete aggregate (RCA) and polyethylene terephthalate (PET) waste. The bricks specimens were prepared by using 100% natural sand, they were then replaced by RCA at 25%, 50% and 75% with proportions of PET consists of 0.5%, 1.0% and 1.5% by weight of natural sand. Based on the results of compressive strength, only RCA 25% with 0.5% PET achieve lower strength than normal bricks while others showed a high strength. However, all design mix reaches strength more than 7N/mm2 as expected. Besides that, the most favorable mix design that achieves high compressive strength is 75% of RCA with 0.5% PET.

The Effect of NaOH Concentration and Curing Condition to the Strength and Shrinkage Performance of Recycled Geopolymer Concrete

Concrete is widely used as a material construction. Globally, the consumption of concrete was estimated to be more than 8 billion tons per year. Nowadays, many problems arise related to concrete manufacturing occur especially on environmental issues. A key concern for environmentalists has always been climate change. One of the ways to mitigate the impact activities on the climate is to reduce carbon footprint. Portland cement are commonly been used in concrete is responsible for about 5% of all CO2emission. It is reported by Davidovit that the production of one ton of Portland cement emits approximately one ton of CO2into the atmosphere. There are several ways to reduce environmental pollution that cause by production and utilization of Portland cement, one of it is Geopolymer concrete. Subsequently Geopolymer concrete incorporating with recycle concrete aggregate (RCA) is one of the alternative to further reduce carbon footprint and as well as can reduce waste. Geopolymer concrete is a concrete that use no cement and produced by the combination of alkaline activator and supplementary cementitious material (SCM) such as fly ash, boiler ash, waste paper sludge ash (WPSA), ground granulated blast-furnace slag (GGBS), and so on in order to reduce carbon emission. In this study the Waste Paper Sludge Ash (WPSA) were used as a SCM and the combination of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) as a binder. Two (2) series of geopolymer concrete specimens comprising two (2) different molar of sodium hydroxide (NaOH) which are 8M and 14M were adopted. The effect variable alkaline molarity on the compressive strength and shrinkage of the geopolymer concrete specimens is tested at the age of 3, 7, 14 and 28 days. The mixture of geopolymer concete with 8M of sodium hydroxide (NaOH) concentration then was categorized into three (3) groups. Each group were been cured at different curing condition which are in ambient condition, oven, and external condition. The size of specimens prepared were 100mm x 100mm x100mm. The result shows that the molarities of sodium hydroxide (NaOH) influenced the strength of Waste Paper Sludge Ash (WPSA) based geopolymer concrete produced incorporating with increasing of recycle concrete aggregate (RCA). The result also show that the geopolymer concrete undergoes very low shrinkage. Curing condition will also effect the strength of geopolymer concrete produced.