為了減少對環境的負面影響及利用廢棄物之目標, 本研究利用緻密配比（DMDA），並添加飛灰（FA）、稻殼灰（RHA）及無機聚物，對設計出之環保建築用磚可行性進行調查. 試驗主要分為兩個階段，為無機聚合物漿體開發及環保建築用磚之生產，而兩階段製成之試體將置於相同之養護環境。第一階段無機聚合物漿體部分，試體尺寸為 50 × 50 × 50 mm，而液固比（L/S）、氫氧化鈉（NaOH）濃度、矽酸鈉（Na2SiO3）濃度及稻殼灰(RHA)用量對抗壓強度之影響，其試體皆於不同齡期進行了研究。第二階段環保建築用磚部分，試體尺寸為220 × 105 × 60 mm， 進行了外觀缺陷、抗壓強度、抗彎強度、吸水率、容積密度、孔隙率之硬固性質試驗。 這個階段，配比中之未研磨之稻殼灰(URHA)主要取代天然砂，並且於鋼模中加壓成型。
無機聚合物漿體之試驗結果顯示，最佳之材料添加比例為，液固比（L/S）0.37、氫氧化鈉（NaOH）濃度10M、稻殼灰(RHA)含量40%漿體之重量比例及矽酸鈉（Na2SiO3）濃度如從10%增加至25%將會增加其抗壓強度。環保建築用磚之試驗結果顯示，未添加未研磨之稻殼灰(URHA)之試體，抗壓強度介於29.31–31.46 MPa、抗彎強度介於5.19–6.91 MPa、吸水率則是介於8.83–10.11% ，而其它之試驗均符合越南標準規範 (TCVN 1541:1998)。研究結果也顯示，添加未研磨之稻殼灰(URHA)將會降低試體之力學性能。總而言之，試驗結果，本研究研製之環保建築用磚，較越南標準規範 (TCVN 1541:1998)中之要求，擁有良好之力學及耐久性能 。 確切地證明了飛灰(FA)及稻殼灰(RHA)在環保建築用磚上應用之可行性。

With the objectives of reducing the negative impacts on environment and utilizing of waste materials, the possibility of producing eco-friendly construction bricks by using fly ash (FA) and rice husk ash (RHA) with applying geopolymerization combined with Densified mixture design algorithm (DMDA) method was investigated in the present study. There are two main stages of experimental programs, which are named as geopolymer paste development and eco-friendly construction bricks production, in this investigation. It was noticed that all geopolymer paste specimens and brick samples were kept in the same curing conditions for these stages. In the first stage, geopolymer paste specimens of 50 × 50 × 50 mm in size were prepared. The effect of various parameters such as liquid-to-solid (L/S) ratio, sodium hydroxide (NaOH) concentration, sodium silicate (Na2SiO3) dosage and RHA amount on the compressive strength of the specimens at different ages was investigated in this stage. Whereas, in the second stage, eco-friendly construction bricks in size of 220 × 105 × 60 mm were prepared for the tests of dimensions and visible defects, compressive strength, flexural strength, water absorption, bulk density and void volume to evaluate the hardened properties of brick samples. In this stage, especially, unground rice husk ash (URHA) was used as a partial replacement of natural sand in the mixtures and forming pressure was applied to form the solid bricks in the steel mold.
From the test results of geopolymer paste specimens, the optimum conditions were found to be that the L/S ratio was 0.37, NaOH concentration was 10M, RHA amount was 40% weight of binder and compressive strength was increased corresponding to the increase in Na2SiO3 dosage from 10% to 25%. By following these conditions for the bricks production stage, the compressive strength, flexural strength and water absorption of the bricks without URHA added were respectively in range of 29.31 – 31.46 MPa, 5.19 – 6.91 MPa and 8.83 – 10.11% and the other properties of the bricks were well conformed to Vietnamese Standard (TCVN 1541:1998). It was found that the addition of URHA in the mixture caused the decrease in mechanical strength as well as in other properties of the bricks. In summary, the test results clearly indicated that all brick samples had very good mechanical properties and durable performance that were much better than the requirements of TCVN 1451:1998. It was definitively proved many possible applications of FA and RHA in the production of eco-friendly construction bricks.

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