Permeability and Porosity of Pervious Concrete Containing Blast Furnace Slag as a Part of Binder Materials and Aggregate

Abstract

The use of industrial by-products could provide a feasible solutions for the construction industry to reduce the strain on supply of natural aggregate as well as achieving the concept of environmentally friendly binder material by replacing part of Portland cement. This paper reports the results of an experimental study, mainly on the permeability and porosity characteristic of pervious concrete developed by substituting 26% Portland cement with air-cooled blast furnace slag and replacing part of natural coarse aggregate with granular blast furnace slag of different aggregate size and different water/cement ratio. The pervious concrete with lower water cement ratio and 25% GBFS affected either the porosity or the compressive strength of the pervious concrete. As expected, the porosity increased in pervious concrete with bigger aggregate size, but decreased when the smaller aggregate size was used. Partial substitution of coarse aggregate with granular GBFS of the same gradation size did not affect the permeability coefficient. Specimens developed using water cement ratio of 0.34 and coarser aggregate size tend to have a greater water permebility compared with those of 0.3 water/cement ratio.

A review of factors influencing performance of pervious concrete

“…The volume of cement paste to coat the aggregate surface increases due to an increase in sand fraction [41]. When fine aggregate is used, its water absorption affects the hydration process and consequently mechanical strength [42]. The performance of high w/cm ratio mixes improves considerably with the inclusion of sand compared to the low w/cm ratio mixes, as water absorption by sand can reduce the hydration of cement in the latter case [41].…”

“…The performance of high w/cm ratio mixes improves considerably with the inclusion of sand compared to the low w/cm ratio mixes, as water absorption by sand can reduce the hydration of cement in the latter case [41]. The absence of fine aggregates contributes to the void ratio and permeability of concrete [1,40,42]. However, a little fine aggregate content in pervious concrete tends to improve its durability and strength [20].…”

“…The porosity of concrete decreases with the reduction in aggregate size [9,30,42]. The total voids of pervious concrete tend to drop with an increase in fine aggregate content.…”

Microscopic Factors Affecting the Performance of Pervious Concrete

“…At present, the research on pervious concrete mainly involves the improvement of its properties by changing the aggregate particle size/gradation, water-cement ratio/ash-bone ratio, target porosity, and external materials. These include studies of the design of the mix ratio [2][3][4][5], the influence of the aggregate particle size [6][7][8][9][10] and type [11,12] on the performance and porosity [13][14][15][16], the relationship between permeability and the mechanical properties of pervious concrete [17,18], and fatigue performance [19][20][21][22]. However, most scholars have not extensively investigated the fine-scale parameters of pervious concrete to analyze its pore structure characteristics, except through electron microscopy [23], computed tomography scanning reconstruction [24], and the piezomercury method [25].…”