Compressive and Flexural Strength of Geopolymer Lightweight Expanded Clay Aggregate for Energy Efficient Building

Abstract

This research aims to investigate the compressive strength and flexural strength of geopolymer from lightweight expanded clay aggregate for energy efficient building. The engineering properties of geopolymer from lightweight expanded clay aggregate at different ratios and curing times were examined. The lightweight expanded clay aggregate were set up to a spherical shape with diameter of 1 .0 cm. The samples were burnt at 1 2 0 0 Celsius degree for 3 0 minutes. The lightweight expanded clay aggregate were used to replace the aggregate in the mixture. The ratio of geopolymer which was used in the experiment in four different ratios of sodium silicate solution (Na2SiO3) to sodium hydroxide solution (NaOH) as 0.60 and the ratio of solution (Na2SiO3 / NaOH) to fly ash as 0 .5 0, 0.55 and 0 .6 0 respectively. The concentrations of sodium hydroxide (NaOH) solution were arranged at 10, 15 and 20 molar. The cylindrical sample size was 10 centimeter in diameter and 20 centimeter in height and sample beams in dimension of 7.0x7.5x30 centimeter, respectively. The geopolymers were kept at room temperature about 22-27 degree Celsius for 1 hour, then incubated in an oven at 60 degree Celsius for 2 days. At the end of the curing period, took the sample to measure the height and weight to identify the compressive strength in accordance with ASTM C39/39M-03 and strength of flexural strength in accordance with ASTM C72- 02, respectively. The results of the tests revealed that the ultimate compressive strength tend to increase with longer curing age by exhibiting average ultimate compressive strength of 23.99 – 25.99; 23.52 – 25.52; and 23.67 – 25.60 kg/cm2 at curing ages of 7, 14, and 28 days, respectively. Succeeding results also showed that the average flexural strength resulted to better outcome as the curing ages increased by exhibiting average modulus of rupture of 97.66-106.78; 100.10-111.97; and 99.49- 118.10 kg/cm2 at curing ages of 7, 14, and 28 days, respectively. Based on the compressive and flexural strengths with mixing ratios of sodium hydroxide of 10, 15, and 20 molars, it was found that the ultimate compressive strength and ultimate flexural strengths were higher as the solutions of sodium hydroxide were more concentrated by exhibiting an average minimum compressive strength of 6.25% , 7.84% , and 7.54% while the modulus of rupture had 8.54% , 10.60% , and 15.76%, respectively. The findings also found that, to obtain the appropriate compressive strength, the ideal mixing ratios of sodium hydroxide and the proportions of solution to fly ash were 15 molars and 0.50 ; while for achieving the suitable flexural strength, the mixing proportions should be 10 molars and 0.55, respectively. From these proportions, the highest compressive and flexural strengths obtained from the experiments were 25.60 kg/cm2 and 118.10 kg/cm2, respectively.