Effect of waste marble powder and rice husk ash on the microstructural, physico-mechanical and transport properties of foam concretes exposed to high temperatures and freeze–thaw cycles

Highlights

• Effects of waste marble powder (WMP) and rice husk ash (RHA) on the properties of foamed concrete were studied.

• High temperature and freeze–thaw durability of foamed concrete incorporating WMP and RHA were investigated.

• Transport properties and shrinkage of foamed concrete were discussed.

• Effects of WMP and RHA on the on the fresh properties of foamed concrete were analyzed.

Abstract

An experimental program was performed to evaluate the impact of rice husk ash (RHA) as cement replacement and waste marble powder (WMP) as sand replacement on the microstructural, mechanical and transport properties of foamed concrete exposed to high temperature and freeze–thaw cycles. For this, Portland Cement (PC) was replaced by RHA at 10% and 20%wt of binder and silica sand was replaced by WMP at 25% and 50%wt of fine aggregates to cast foamed concrete mixtures. Two different foam contents of 40 kg/m³ and 80 kg/m³ were used in the production of foamed concretes with water/binder (w/b) ratio of 0.70. Two reference mixtures were produced from silica sand and without RHA at each foam content. Other foam concretes were fabricated from 25% and 50% WMP instead of silica sand and 10% and 20% RHA instead of cement. Fresh properties of mixtures were evaluated by performing slump test. Transport properties of foam concretes were investigated, including porosity, sorptivity and water absorption after 90 days curing. Mechanical properties of foam concretes were investigated, including compressive and flexural strength ultrasonic pulse velocity (UPV) after 7, 28 and 90 days. Drying shrinkage and thermal conductivity of concretes were also studied after 90 days. Durability of concretes were also investigated after exposure to the temperature of 200, 400, 600 and 800 °C and freeze–thaw (F-T) cycles of 100 and 200 in addition to microstructure investigations. Results show that 10% RHA as cement substitute and 50% WMP as sand substitute give optimum percentage especially at late-age of 90 days at foam content of 40 kg/m3. The lowest drying shrinkage and sorptivity were obtained by using 10%RHA and 25%WMP. The results also indicate that water cooled specimens showed more strength loss than air cooled specimens after 200 °C. The worst F-T performance was obtained for the mixture containing 10% RHA and without WMP by 43.8 and 59.8% strength reductions.

Introduction

Foam concrete is a type of cement mortar in which cement, water, filler and air bubbles are given using a suitable foaming agent that does not contain coarse aggregate. It has advantages such as minimum aggregate consumption, high fluidity, high porosity, good thermal insulation, low self-weight, fire resistance, airborne sound insulation, and desired compressive strength and cost effectiveness.

In practice, foamed concrete is widely used in panels, walls, road fill, partitions blocks, insulated wall panels, bridge padding, floor insulation, roof insulation and lightweight building blocks in many countries [1], [2], [3], [4], [5], [6]. There has been a serious transition towards the search for alternative concrete materials in economic, environmental and social terms for sustainable development because in many parts of the world, the consequences of using tons of natural resources in concrete are irreversible and the consumption of natural materials and environmental effects have started to occur [7]. One of the ways to reduce the use of natural materials is to use industrial by-products and waste materials such as silica fume, ground blast furnace slag, rice husk ash, fly ash and waste marble powder as cement substitutes or aggregates in cement-based composites. Failure to use such materials will cause great damage to the soil and water as well as air pollution [8], [9], [10], [11], [12], [13], [14], [15], [16]. These materials contribute to the pozzolanic reaction with calcium hydroxide as they have a high silica content and contribute to concrete performance due to the production of more calcium silicate hydrate gel compounds and not only provide visible environmental benefits but also provided less CO₂ emission and good economy [17], [18], [19].

Marble is widely used as a building stone, and high volume marble production generates a significant amount of waste material. Approximately 70% of this mineral is wasted in mining, processing and polishing stages, which have a serious impact on the environment. Unloading large quantities of marble waste can cause large dust generation in the environment, air pollution from fine marble particles, clogging of sewers and degradation of agricultural land due to clogging of the soil pores of aquifers [20], [21]. Many studies showed that marble waste can be utilzed in concrete as fine aggregate or as a cement substitute and has found to have potential uses. However, due to its inert structure, using it as fine aggregate is is more suitable as reported by many investigations [22], [23], [24]. Large marble particles can be used to produce concrete as coarse aggregate or fine aggregate by crushing [24], [25], [26]. It was found that concrete produced from WMP as sand substitute had improvement properties when compared to concrete produced from WMP as cement substitute [27]. Demirel [11], [28] showed that compressive strength of concrete in which aggregates replaced by with 0.25 mm marble waste enhanced and the porosity also reduced. Gameiro [29] investigated the performance of concrete containing WMP as sand replacement and reported that concrete durability and carbonation resistance increased by replacing sand by 20% WMP and also improved capillarity. Vardhan et al. [24] reported that 20% strength enhancement and 30% shrinkage reduction was obtained by using marble waste in concrete. There has been no study used WMP as aggregate replacement or cement substitute in foam concrete so far therefore it was utilized as fine aggregates instead of sand in this work. Large amount of rice is grown in the world and large amount of waste is produced, which poses a great threat to the environment, RHA arises from these wastes, and due to its binding properties, its use as a cement substitute can provide great economic and environmental benefits. RHA has pozzolanic property and has been successfully used to replace some of the cement in concrete with no visible deterioration in strength and durability, with a significant increase in workability [30], [31], [32], [33]. Adesina and Olutoge [34] reported that a 45% increase in compressive strength by replacing cement with RHA. Safiuddin et al. [35] pointed out that compressive strength enhances by replacing cement with 15% RHA and previous research studies also noted similar observations [36], [37], [38]. Gill and Siddiqui [39] added metakaolin and RHA up to 40% instead of cement and recorded that 88% enhancement in the 28-day compressive strength. Huang et al. [32] replaced cement wirh both silica fume and RHA by 30%. They obtained 14.5% enhancement in bending and compressive strength by replacing cement with 20% RHA. Ameri et al. [40] reported 21% compressive strength enhancement by replacing cement with 15% RHA. Rahman et al. [41] obtained the compressive strength enhancements at 10, 15 and 20% RHA as cement substitute. Kannan and Ganesan [42] added RHA and metakaolin combination in place of cement and achieved compressive increase of up to 15%. Using RHA in foam concrete has not been investigated so far therefore it was utilized as cement replacement in this experimantal work.

This study focus on the impact of rice husk ash (RHA) as cement replacement and waste marble powder (WMP) as sand replacement on the microstructural, mechanical and transport properties of foamed concrete exposed to high temperature and freeze–thaw cycles. For this, Ordinary Portland Cement (OPC) was replaced by RHA at 10% and 20%wt of binder and silica sand was replaced by WMP at 25% and 50%wt of fine aggregates to cast foamed concrete mixtures. Two different foam contents of 40 kg/m3 and 80 kg/m³ were used in the production of foamed concretes with water/binder (w/b) ratio of 0.70. Two reference mixtures were produced from silica sand and without RHA at each foam content. Other foam concretes were fabricated from 25% and 50% WMP instead of silica sand and 10% and 20% RHA instead of cement. Fresh properties of mixtures were evaluated by performing slump test. Transport properties of foam concretes were investigated, including porosity, water absorption and sorptivity after 90 days curing. Mechanical properties of foam concretes were investigated, including compressive and flexural strength ultrasonic pulse velocity (UPV) after 7, 28 and 90 days. Drying shrinkage and thermal conductivity of foam concretes were also studied after 90 days. Durability of foamed concretes after subjected to high temperature and freeze–thaw (F-T) cycles were also evaluated after 200, 400, 600 and 800 °C and 100 and 200F-T cycles respectively in addition to microstructural analysis.