no 460 the high pozzolan to cement ratio of this mix creates a concrete with very low porosity 1 4 and hydraulic absorption 0 62 which is reflected in the high compressive strength 77 mpa the 28 day compressive strength of mix no 211 is comparable to 460 but obtains this strength by having high cement content also note that the resulting concrete has a 3 fold increase in porosity and a 3 fold increase in absorption relative to 460 table iv presents a series of formulations that incorporate a mixture of pozzolans the pozzolan cement ratio ranges between 0 16 and 2 25 mixes 211 225 and 231 have the pozzolans metakaolin and silica flour fixed at 2 0 wt each with the cement content being 25 0 20 0 and 15 0 respectively in this series the density decreases while the porosity and absorption increase the water to cement ratio w cm also increased in this series and is probably responsible for the deterioration of the material properties comparing mixes 231 and 190 illustrate this point the mixes have nearly identical compositions but very different w c the 28 day strength porosity and absorption are dramatically improved mixes 342 455 and 460 illustrate the role of the glass pozzolan there is an increased water demand as 12 mesh glass is replaced by 100 mesh glass pozzolan but the resulting 28 day compressive strength is greatly enhanced the porosity and absorption which are already excellent are also improved table v below examines mixes with low cement content and with very high p cm and particularly for a series of formulations that incorporate a.