EFFECT OF SUPERPLASTICIZER TYPE ON WORKABILITY RETENTION AND COMPRESSIVE STRENGTH DEVELOPMENT IN TC

The performance of superplasticizers has not been well characterized under prolonged tropical conditions. There is more research on these additives in temperate climates, particularly in West Africa. This research was done to assess the workability retention and compressive strength development of concrete made with the three generations of superplasticizers. These superplasticizers were lignosulfonate (LS), naphthalene-based (NS) and polycarboxylate ether (PCE). All these superplasticers were studied under controlled tropical conditions simulating Nigerian construction environments. Four types of concrete mixes were prepared, control mix (Mix C), and three admixture mixes (Mix L, Mix N, and Mix P) at optimized dosages of 1.0%, 1.50% and 0.80% by weight of cement (bwoc). Every batch was evaluated in 32±2°C temperature and 70±5% relative humidity. The slump test evaluated workability at intervals of 0, 15, and 30 min. Compressive strength was tested on 150 mm cubes at 3, 7 and 28 days as per the guideline BS EN 12390-3:2019. Using current Nigerian market prices a cost-performance ratio analysis was done. The highest workability retention (Workability Retention Index = 110.5% at 30 minutes), as a slump gain of 20 mm over the observation period, was achieved by Mix P (PCE, 0.80% bwoc). Moreover, Mix P also recorded the highest 28-day compressive strength, which was 74.14 N/mm², a 37.9% gain over control (31.16 N/mm²). Mix N (NS) showed excellent retention (WRI = 94.7) with a strength of 52.38 N/mm² in 28 days. The resilience of Mix L (in LS) workability was below the control as seen in WRI (54.1%). However, its strength was enhanced by 38.7%. Admixtures based on PCE show superior performance across the board under tropical conditions and also the best economic viability. Cost-Performance Ratio = NGN 1,286/MPa (control: NGN 2,608/MPa). The results will serve as a guide in the selection of superplasticizer for Nigerian and other tropical construction practices