Effects of Mix Composition on Microwave Incinerated Rice Husk Ash (MIRHA) Mortar

There are many cement replacement materials (CRM) have been commercialized in
the industry. Microwave Incinerated Rice Husk Ash (MIRRA) is a new material that
can be used as CRM in the industry. The used of MIRRA in concrete has been
extremely studied in Universiti Teknologi PETRONAS (UTP). The study on use of
MIRRA in mortar has not been studied. The objectives of this project were to obtain
optimum water cement ratio for MIRRA mortar mix, to obtain the suitable mix
composition and to obtain the optimum cement replacement by MIRRA in MIRRA
mortar. Various water cement ratios (0.60 and 0.65), binder aggregate ratios (1 :3 and
1 :4) and different percentages of cement replacement by MIRRA (0%, 5%, 10%,
15%, 20%, 25% and 30%) were used to cast mortar cubes. The sample preparation
follows BS 1881 and compressive strength (7, 28 and 60 days after curing), water
absorption (60 days after curing) and initial rate of suction (IRS) (60 days after
curing) values were determined. The highest result for 28-day compressive strength
test for all samples is 46.17MPa from sample 5M360 which contains 5% of cement
replacement by MIRRA, binder to sand ratio of 1:3 and water cement ratio of 0.60.
Whereas for IRS test, almost all IRS values of all samples fall between accepted
range within between 0.25 to 1.5 k:g/m.2.min. For water absorption, almost all
samples were under maximum water absorption value for bricks which is 18% water
absorption.