Optimal Constituent Mix Ratio for Improved Fresh Properties of Cementitious and Alkali-Activated Porous Concretes

This study focuses on the ideal mix of constituents (aggregate, binder, liquid phase, and admixtures) for porous concrete (PC) with optimal fresh properties to be used in pervious road pavements. Ordinary portland cement (CEM-I) and alkali-activated blast furnace slag (AA-BFS) were used as binders. This experimental investigation focused on finding the mix proportion that can best produce a consistent fresh mixture in which the mortar attaches strongly to the coarse aggregates. CEM-I and AA-BFS mortars and concretes were designed to meet the consistency criteria for PC mixtures and then tested to assess their volumetric and mechanical properties. The effect of mix composition on the consistency of fresh mixtures was adjudged through statistical analyses. In the case of AA-BFS mixtures, latex admixture (LA) and a polycarboxylate-ether-based superplasticizer (SP) both helped to achieve a higher level of consistency, and the addition of a viscosity-modifying admixture was necessary for CEM-I PC mixtures only. In terms of hardened properties, AA-BFS mortars exhibited slightly higher strengths than CEM-I ones independently of curing time. Although neither LA nor SP increased strength values at the mortar scale, in PC mixtures, the use of LA proved fundamental in the production of AA-BFS concrete with adequate strength values. This study recognizes that the optimization method as per the consistency assessment of fresh mixtures can be applied to PC with both cementitious and AA-BFS binders.