The influence of reusing ‘Formtex’ controlled permeability formwork on strength and durability of concrete

Abstract

The effects of the reuse of 'Formtex' Controlled Permeability Formwork (CPF) liner on strength and durability properties of concrete were investigated at two different water-cement ratios and the results are reported in this paper. Test blocks were cast using the CPF on one side and impermeable formwork (IF) on the opposite side of the mould so that direct comparisons could be made between the two. The strength was assessed using the Limpet pulloff tester and both the air permeability and the water absorption (sorptivity) were measured using the Autoclam Permeability System. Both these instruments measured the 'covercrete' properties. In addition, cores cut from the test specimens were subjected to an accelerated carbonation test and a chloride exposure test. The results showed that the 'Formtex' CPF increases the surface strength and the durability of concrete compared to the IF. There was an almost complete elimination of blowholes. The permeability of concrete decreased and its resistance to the ingress of both carbon dioxide and chlorides increased when CPF was used. The beneficial effects of the Formtex CPF were most evident in concrete of higher water-cement ratio. With the reuse of the Formtex liner twice, that is a total of three uses, the performance of the CPF to improve the properties of concrete remained almost the same. In this research the CPF liner was cleaned thoroughly between each use, which must be adhered to for site applications for reproducing the beneficial effects observed in the laboratory.

Influence of formwork liners on fresh, mechanical and durability properties of cast concretes

“…Chapter 5 represents the conclusion drawn from the results and the performance evaluation of different forming tubes. honeycombing and improved surface strength have also remarked (Basheer et al, 2008).…”

“…The basic form of a formwork liner is the use of permeable liner against a vertical or inclined formwork. Zemdrain type liner is manufactured from 100 % polypropylene fibers and is thermally bonded (Basheer et al, 2008).…”

“…Chinese engineers checked the strength of surface with rebound hammer and they noticed strength increase of 11-28 % on formwork liner as compare to conventional molds (Cuicui, at al., 2012). From the two OPC mix (different w/c) it was noticed the strength increase was in the concrete with formwork liner but the percentage change was not very remarkable (Basheer et al, 2008). conducted research on three different formwork liner of different absorption and compared surface roughness, surface hardness and surface tensile strength with control impermeable plywood formwork.…”

Designing metallic surfaces in contact with hardening fresh concrete: A review

“…On the contrary, water removal by absorption (e.g. on wood formworks and porous skins) reduces the water amount at the interfacial layer [55][56][57][58], weakens the capillary forces, and lowers the concrete-substrate bonding [59][60][61].…”

Utjecaj Oplata Kontrolirane Propusnosti Na Mehanička I Trajnosna Svojstva Zaštitnog Sloja Betona

“…Rezultati dosadašnjih istraživanja pokazali su da CPF oplate smanjuju upijanje vode za gotovo 80% u odnosu na betone pripremljene su klasičnoj oplati [13]. Slično je primijećeno i kod ostalih trajnosnih svojstava [14]. Kako bi se ocijenio utjecaj CPF oplata na svojstva propusnosti, provedeno je nerazorno ispitivanje plinopropusnosti pomoću metode APIS [9] te su izvađeni valjci promjera 10 cm na kojima je provedeno ispitivanje kapilarnog upijanja i plinopropusnosti, prema RILEM preporukama [7].…”